Misplaced Pages

#106893

120-403: Most (80–100%) amputees experience a phantom limb, with some of them having non-painful sensations. The amputee may feel very strongly that the phantom limb is still part of the body. People will sometimes feel as if they are gesturing, feel itches, twitch, or even try to pick things up. The missing limb often feels shorter and may feel as if it is in a distorted and painful position. Occasionally,

240-446: A major physical trauma or prolonged starvation can greatly disrupt homeostasis. On the other hand, an organism's attempt at restoring conditions back to or near homeostasis, often consuming energy and natural resources, can also be interpreted as stress. The brain cannot sustain an equilibrium under chronic stress; the accumulation of such an ever-deepening deficit is called chronic stress. The ambiguity in defining this phenomenon

360-437: A 2016 review. A 2018 review, which also criticized the scientific quality of many reports on mirror therapy (MT), found 15 good-quality studies conducted between 2012 and 2017 (out of a pool of 115 publications), and concluded that "MT seems to be effective in relieving PLP, reducing the intensity and duration of daily pain episodes. It is a valid, simple, and inexpensive treatment for PLP." Phantom sensations may also occur after

480-459: A barrier to chemicals dissolved in the blood, protecting the brain from most neurotoxins commonly found in food. Within the meninges the brain and spinal cord are bathed in cerebral spinal fluid which replaces the body fluid found outside the cells of all bilateral animals . In vertebrates, the CNS is contained within the dorsal body cavity , while the brain is housed in the cranial cavity within

600-478: A brief biological background of neuroanatomy and neurochemistry and how they relate to stress. Stress, either severe, acute stress or chronic low-grade stress may induce abnormalities in three principal regulatory systems in the body: serotonin systems , catecholamine systems , and the hypothalamic-pituitary-adrenocortical axis . Aggressive behavior has also been associated with abnormalities in these systems. The brain endocrine interactions are relevant in

720-436: A connection between the systems. The HPA axis ultimately results in the release of cortisol, which generally has immunosuppressive effects. However, the effect of stress on the immune system is disputed, and various models have been proposed in an attempt to account for both the supposedly "immunodeficiency" linked diseases and diseases involving hyper activation of the immune system. One model proposed to account for this suggests

840-505: A dangerous neighborhood). See allostatic load for further discussion of the biological process by which chronic stress may affect the body. For example, studies have found that caregivers, particularly those of dementia patients, have higher levels of depression and slightly worse physical health than non-caregivers. When humans are under chronic stress, permanent changes in their physiological, emotional, and behavioral responses may occur. Chronic stress can include events such as caring for

960-440: A model dividing stress into eustress and distress . Where stress enhances function (physical or mental, such as through strength training or challenging work), it may be considered eustress. Persistent stress that is not resolved through coping or adaptation, deemed distress, may lead to anxiety or withdrawal (depression) behavior. The difference between experiences that result in eustress and those that result in distress

1080-416: A number of physical changes that have both short- and long-term effects on the body. The Holmes and Rahe stress scale was developed as a method of assessing the risk of disease from life changes. The scale lists both positive and negative changes that elicit stress. These include things such as a major holiday or marriage, or death of a spouse and firing from a job. Homeostasis is a concept central to

1200-422: A number of primitive emotions or feelings such as hunger , thirst and maternal bonding . This is regulated partly through control of secretion of hormones from the pituitary gland . Additionally the hypothalamus plays a role in motivation and many other behaviors of the individual. The cerebrum of cerebral hemispheres make up the largest visual portion of the human brain. Various structures combine to form

1320-472: A peripheral nerve injury resulting in deafferentation. This causes changes in the dorsal horn of the spinal cord, which normally has an inhibitory effect on sensory transmission. Most approaches to treatment over the past two decades have not shown consistent symptom improvement. Treatment approaches have included medication such as antidepressants , spinal cord stimulation, vibration therapy , acupuncture , hypnosis , and biofeedback . Reliable evidence

SECTION 10

#1733085205107

1440-684: A person with Alzheimer's disease. Chronic stress has also been shown to impair developmental growth in children by lowering the pituitary gland 's production of growth hormone, as in children associated with a home environment involving serious marital discord, alcoholism , or child abuse . Chronic stress also has a lot of illnesses and health care problems other than mental that comes with it. Severe chronic stress for long periods of time can lead to an increased chance of catching illnesses such as diabetes, cancer, depression, heart disease and Alzheimer's disease. More generally, prenatal life, infancy, childhood, and adolescence are critical periods in which

1560-467: A person with effective coping mechanisms for dealing with psychological stress , with stress defined as a person's physiological response to an internal or external stimulus that triggers the fight-or-flight response. Stress management is effective when a person uses strategies to cope with or alter stressful situations. There are several ways of coping with stress, such as controlling the source of stress or learning to set limits and to say "no" to some of

1680-494: A preference for habit based learning , and decreased task flexibility and spatial working memory , probably through alterations of the dopaminergic systems . Stress may also increase reward associated with food, leading to weight gain and further changes in eating habits. Stress may contribute to various disorders, such as fibromyalgia , chronic fatigue syndrome , depression , as well as other mental illnesses and functional somatic syndromes . Selye published in year 1975

1800-402: A psychosocial situation to be stressful, it must be appraised as such. He argued that cognitive processes of appraisal are central in determining whether a situation is potentially threatening, constitutes a harm/loss or a challenge, or is benign. Both personal and environmental factors influence this primary appraisal, which then triggers the selection of coping processes. Problem-focused coping

1920-492: A push towards an imbalance of cellular immunity (Th1) and humoral immunity (Th2). The proposed imbalance involved hyperactivity of the Th2 system leading to some forms of immune hypersensitivity , while also increasing risk of some illnesses associated with decreased immune system function, such as infection and cancer . Chronic stress is a term sometimes used to differentiate it from acute stress. Definitions differ, and may be along

2040-412: A region called the ventricular zone . The neural stem cells, principally radial glial cells , multiply and generate neurons through the process of neurogenesis , forming the rudiment of the CNS. The neural tube gives rise to both brain and spinal cord . The anterior (or 'rostral') portion of the neural tube initially differentiates into three brain vesicles (pockets): the prosencephalon at

2160-400: A role in hypertension , and may further predispose people to other conditions associated with hypertension. Stress may precipitate abuse of drugs and/or alcohol. Stress may also contribute to aging and chronic diseases in aging, such as depression and metabolic disorders. The immune system also plays a role in stress and the early stages of wound healing . It is responsible for preparing

2280-401: A shift from Th1 (cellular) to Th2 (humoral) immunity, while decreased T-cell proliferation, and natural killer cell cytotoxicity. Stressful event sequences did not elicit a consistent immune response; however, some observations such as decreased T-Cell proliferation and cytotoxicity, increase or decrease in natural killer cell cytotoxicity, and an increase in mitogen PHA. Chronic stress elicited

2400-441: A shift toward Th2 immunity, as well as decreased interleukin 2, T cell proliferation, and antibody response to the influenza vaccine . Distant stressors did not consistently elicit a change in immune function. Another response to high impacts of chronic stress that lasts for a long period of time, is more immune dysfunction and more metabolic dysfunction. It is proven in studies that when continuously being in stressful situations, it

2520-474: A spouse with dementia, or may result from brief focal events that have long term effects, such as experiencing a sexual assault. Studies have also shown that psychological stress may directly contribute to the disproportionately high rates of coronary heart disease morbidity and mortality and its etiologic risk factors . Specifically, acute and chronic stress have been shown to raise serum lipids and are associated with clinical coronary events. However, it

SECTION 20

#1733085205107

2640-451: A state similar to hyperaldosteronism . If the stressor persists, it becomes necessary to attempt some means of coping with the stress. The body attempts to respond to stressful stimuli, but after prolonged activation, the body's chemical resources will be gradually depleted, leading to the final stage. The third stage could be either exhaustion or recovery : The result can manifest itself in obvious illnesses, such as general trouble with

2760-401: A stranger's hand, and then held no one's hand. When the women were holding their husband's hand, the response was reduced in many brain areas. When holding the stranger's hand the response was reduced a little, but not as much as when they were holding their husband's hand. Social support helps reduce stress and even more so if the support is from a loved one. Lazarus argued that, in order for

2880-438: Is a painful or unpleasant sensation experienced where the amputated limb was. Phantom sensations are any other, nonpainful sensations perceived in the amputated or missing limb area. There are 3 differentiated types of phantom sensations: kinetic, kinesthetic, and exteroceptive. Kinetic phantom sensations are perceived movements of the amputated body part (i.e., feeling your toes flex). Kinesthetic phantom sensations are related to

3000-424: Is absent from both lay and expert life narratives before the 1930s". Physiological stress represents a wide range of physical responses that occur as a direct effect of a stressor causing an upset in the homeostasis of the body. Upon immediate disruption of either psychological or physical equilibrium the body responds by stimulating the nervous , endocrine , and immune systems . The reaction of these systems causes

3120-466: Is also subcortical gray matter making up a large number of different nuclei . From and to the spinal cord are projections of the peripheral nervous system in the form of spinal nerves (sometimes segmental nerves ). The nerves connect the spinal cord to skin, joints, muscles etc. and allow for the transmission of efferent motor as well as afferent sensory signals and stimuli. This allows for voluntary and involuntary motions of muscles, as well as

3240-505: Is an organism's response to a stressor such as an environmental condition. When stressed by stimuli that alter an organism's environment, multiple systems respond across the body. In humans and most mammals, the autonomic nervous system and hypothalamic-pituitary-adrenal (HPA) axis are the two major systems that respond to stress. Two well-known hormones that humans produce during stressful situations are adrenaline and cortisol . The sympathoadrenal medullary (SAM) axis may activate

3360-400: Is characterized by three phases: a nonspecific alarm mobilization phase, which promotes sympathetic nervous system activity; a resistance phase, during which the organism makes efforts to cope with the threat; and an exhaustion phase, which occurs if the organism fails to overcome the threat and depletes its physiological resources. Alarm is the first stage, which is divided into two phases:

3480-536: Is determined by the disparity between an experience (real or imagined) and personal expectations, and resources to cope with the stress. Alarming experiences, either real or imagined, can trigger a stress response. Responses to stress include adaptation, psychological coping such as stress management , anxiety, and depression . Over the long term, distress can lead to diminished health and/or increased propensity to illness; to avoid this, stress must be managed. Stress management encompasses techniques intended to equip

3600-465: Is directed at managing the problem, whereas emotion-focused coping processes are directed at managing the negative emotions. Secondary appraisal refers to the evaluation of the resources available to cope with the problem, and may alter the primary appraisal. In other words, primary appraisal includes the perception of how stressful the problem is and the secondary appraisal of estimating whether one has more than or less than adequate resources to deal with

3720-546: Is important for learning, responding to the stressors and cognitive flexibility. Chronic stressors may not be as intense as acute stressors such as natural disaster or a major accident, but persist over longer periods of time and tend to have a more negative effect on health because they are sustained and thus require the body's physiological response to occur daily. This depletes the body's energy more quickly and usually occurs over long periods of time, especially when these microstressors cannot be avoided (i.e. stress of living in

Phantom limb - Misplaced Pages Continue

3840-477: Is lacking on whether any treatment is more effective than the others. Most treatments are not very effective. Ketamine or morphine may be useful around the time of surgery. Morphine may be helpful for longer periods of time. Evidence for gabapentin is mixed. Perineural catheters that provide local anesthetic agents have poor evidence of success when placed after surgery in an effort to prevent phantom limb pain. One approach that has received public interest

3960-650: Is more likely to get sick. Also, when being exposed to stress, some claim that the body metabolizes the food in a certain way that adds extra calories to the meal, regardless of the nutritional values of the food. Some studies have observed increased risk of upper respiratory tract infection during chronic life stress. In patients with HIV, increased life stress and cortisol was associated with poorer progression of HIV. Also with an increased level of stress, studies have proven evidence that it can reactivate latent herpes viruses. A link has been suggested between chronic stress and cardiovascular disease. Stress appears to play

4080-536: Is possible for individuals to exhibit hardiness —a term referring to the ability to be both chronically stressed and healthy. Even though psychological stress is often connected with illness or disease, most healthy individuals can still remain disease-free after being confronted with chronic stressful events. This suggests that there are individual differences in vulnerability to the potential pathogenic effects of stress; individual differences in vulnerability arise due to both genetic and psychological factors. In addition,

4200-408: Is sensory input indicating pain from a part of the body that is no longer existent. This phenomenon is still not fully understood, but it is hypothesized that it is caused by activation of the somatosensory cortex . One theory is it may be related to central sensitization, which is a common experience among amputees. Central sensitization is when there are changes in the responsiveness of the neurons in

4320-404: Is significant in that it consists of CNS tissue expressed in direct contact to the environment, allowing for administration of certain pharmaceuticals and drugs. At the anterior end of the spinal cord lies the brain. The brain makes up the largest portion of the CNS. It is often the main structure referred to when speaking of the nervous system in general. The brain is the major functional unit of

4440-401: Is the use of a mirror box . The mirror box provides a reflection of the intact hand or limb that allows the patient to "move" the phantom limb, and to unclench it from potentially painful positions. Although mirror therapy was introduced by VS Ramachandran in the early 1990s, little research was done on it before 2009, and much of the subsequent research has been of poor quality, according to

4560-400: Is when you feel as if your amputated limb is becoming more proximal to your body through progressive shortening. Pain, temperature, touch, and pressure information are carried to the central nervous system via the anterolateral system ( spinothalamic tracts , spinoreticular tract , spinomesencefalic tract), with pain and temperature information transferred via lateral spinothalamic tracts to

4680-413: The adrenal gland releases, although this can increase storage of flashbulb memories it decreases long-term potentiation (LTP). The hippocampus is important in the brain for storing certain kinds of memories and damage to the hippocampus can cause trouble in storing new memories but old memories, memories stored before the damage, are not lost. Also high cortisol levels can be tied to the deterioration of

4800-418: The capillaries of the brain. Upon CNS injury astrocytes will proliferate, causing gliosis , a form of neuronal scar tissue, lacking in functional neurons. The brain ( cerebrum as well as midbrain and hindbrain ) consists of a cortex , composed of neuron-bodies constituting gray matter, while internally there is more white matter that form tracts and commissures . Apart from cortical gray matter there

4920-456: The cerebellum and transmit information between the cerebellum and the cerebral cortex . In the dorsal posterior pons lie nuclei that are involved in the functions of breathing, sleep, and taste. The midbrain, or mesencephalon, is situated above and rostral to the pons. It includes nuclei linking distinct parts of the motor system, including the cerebellum, the basal ganglia and both cerebral hemispheres , among others. Additionally, parts of

Phantom limb - Misplaced Pages Continue

5040-405: The digestive system (e.g. occult bleeding , melena , constipation /obstipation), diabetes , or even cardiovascular problems ( angina pectoris ), along with clinical depression and other mental illnesses. Central nervous system The central nervous system ( CNS ) is the part of the nervous system consisting primarily of the brain and spinal cord . The CNS is so named because

5160-567: The fight-or-flight response through the sympathetic nervous system , which dedicates energy to more relevant bodily systems to acute adaptation to stress, while the parasympathetic nervous system returns the body to homeostasis . The second major physiological stress-response center, the HPA axis, regulates the release of cortisol , which influences many bodily functions such as metabolic, psychological and immunological functions . The SAM and HPA axes are regulated by several brain regions, including

5280-426: The limbic system , prefrontal cortex , amygdala , hypothalamus , and stria terminalis . Through these mechanisms, stress can alter memory functions , reward , immune function , metabolism and susceptibility to diseases. Disease risk is particularly pertinent to mental illnesses, whereby chronic or severe stress remains a common risk factor for several mental illnesses . Acute stressful situations where

5400-560: The mesencephalic duct (cerebral aqueduct). The metencephalon becomes, among other things, the pons and the cerebellum , the myelencephalon forms the medulla oblongata , and their cavities develop into the fourth ventricle . Rhinencephalon , amygdala , hippocampus , neocortex , basal ganglia , lateral ventricles Epithalamus , thalamus , hypothalamus , subthalamus , pituitary gland , pineal gland , third ventricle Tectum , cerebral peduncle , pretectum , mesencephalic duct Pons , cerebellum Planarians , members of

5520-455: The primary sensory cortex , located in the postcentral gyrus in the parietal lobe , where sensory information is represented somatotropically, forming the sensory homunculus . Somatotopic representation seems to be a factor in the experience of phantom limb, with larger regions in the sensory homunculus typically experiencing more phantom sensations or pain. These areas include the hands, feet, fingers and toes. In phantom limb syndrome, there

5640-407: The shock phase and the antishock phase. Resistance is the second stage. During this stage, increased secretion of glucocorticoids intensifies the body's systemic response. Glucocorticoids can increase the concentration of glucose, fat, and amino acid in blood. In high doses, one glucocorticoid, cortisol , begins to act similarly to a mineralocorticoid ( aldosterone ) and brings the body to

5760-465: The skull . The spinal cord is housed in the spinal canal within the vertebrae . Within the CNS, the interneuronal space is filled with a large amount of supporting non-nervous cells called neuroglia or glia from the Greek for "glue". In vertebrates, the CNS also includes the retina and the optic nerve ( cranial nerve II), as well as the olfactory nerves and olfactory epithelium . As parts of

5880-404: The striatum , the hippocampus and the neocortex , and its cavity becomes the first and second ventricles (lateral ventricles). Diencephalon elaborations include the subthalamus , hypothalamus , thalamus and epithalamus , and its cavity forms the third ventricle . The tectum , pretectum , cerebral peduncle and other structures develop out of the mesencephalon, and its cavity grows into

6000-427: The tectum ). The neocortex of monotremes (the duck-billed platypus and several species of spiny anteaters ) and of marsupials (such as kangaroos , koalas , opossums , wombats , and Tasmanian devils ) lack the convolutions – gyri and sulci – found in the neocortex of most placental mammals ( eutherians ). Within placental mammals, the size and complexity of the neocortex increased over time. The area of

6120-401: The vestibular organ . The two structures of the diencephalon worth noting are the thalamus and the hypothalamus. The thalamus acts as a linkage between incoming pathways from the peripheral nervous system as well as the optical nerve (though it does not receive input from the olfactory nerve) to the cerebral hemispheres. Previously it was considered only a "relay station", but it is engaged in

SECTION 50

#1733085205107

6240-449: The 116 genes involved in the nervous system of planarians, which includes genes related to the CNS, also exist in humans. In arthropods , the ventral nerve cord , the subesophageal ganglia and the supraesophageal ganglia are usually seen as making up the CNS. Arthropoda, unlike vertebrates, have inhibitory motor neurons due to their small size. The CNS of chordates differs from that of other animals in being placed dorsally in

6360-405: The CNS and PNS, respectively. Both act to add myelin sheaths to the axons, which acts as a form of insulation allowing for better and faster proliferation of electrical signals along the nerves. Axons in the CNS are often very short, barely a few millimeters, and do not need the same degree of isolation as peripheral nerves. Some peripheral nerves can be over 1 meter in length, such as the nerves to

6480-423: The CNS to and from the face, as well as to certain muscles (such as the trapezius muscle , which is innervated by accessory nerves as well as certain cervical spinal nerves ). Two pairs of cranial nerves; the olfactory nerves and the optic nerves are often considered structures of the CNS. This is because they do not synapse first on peripheral ganglia, but directly on CNS neurons. The olfactory epithelium

6600-403: The CNS, they connect directly to brain neurons without intermediate ganglia . The olfactory epithelium is the only central nervous tissue outside the meninges in direct contact with the environment, which opens up a pathway for therapeutic agents which cannot otherwise cross the meninges barrier. The CNS consists of two major structures: the brain and spinal cord . The brain is encased in

6720-510: The CNS. Different forms of glial cells have different functions, some acting almost as scaffolding for neuroblasts to climb during neurogenesis such as bergmann glia , while others such as microglia are a specialized form of macrophage , involved in the immune system of the brain as well as the clearance of various metabolites from the brain tissue . Astrocytes may be involved with both clearance of metabolites as well as transport of fuel and various beneficial substances to neurons from

6840-419: The CNS. While the spinal cord has certain processing ability such as that of spinal locomotion and can process reflexes , the brain is the major processing unit of the nervous system. The brainstem consists of the medulla , the pons and the midbrain . The medulla can be referred to as an extension of the spinal cord, which both have similar organization and functional properties. The tracts passing from

6960-596: The age at which the stress is experienced can dictate its effect on health. Research suggests chronic stress at a young age can have lifelong effects on the biological, psychological, and behavioral responses to stress later in life. The term "stress" had none of its contemporary connotations before the 1920s. It is a form of the Middle English destresse , derived via Old French from the Latin stringere , "to draw tight". The word had long been in use in physics to refer to

7080-447: The axon. During early development of the vertebrate embryo, a longitudinal groove on the neural plate gradually deepens and the ridges on either side of the groove (the neural folds ) become elevated, and ultimately meet, transforming the groove into a closed tube called the neural tube . The formation of the neural tube is called neurulation . At this stage, the walls of the neural tube contain proliferating neural stem cells in

7200-519: The big toe. To ensure signals move at sufficient speed, myelination is needed. The way in which the Schwann cells and oligodendrocytes myelinate nerves differ. A Schwann cell usually myelinates a single axon, completely surrounding it. Sometimes, they may myelinate many axons, especially when in areas of short axons. Oligodendrocytes usually myelinate several axons. They do this by sending out thin projections of their cell membrane , which envelop and enclose

7320-476: The body's response to a stressor or embody the act of stress itself is part of the ambiguity in defining what exactly stress is. The central nervous system works closely with the body's endocrine system to regulate these mechanisms. The sympathetic nervous system becomes primarily active during a stress response , regulating many of the body's physiological functions in ways that ought to make an organism more adaptive to its environment. Below there follows

SECTION 60

#1733085205107

7440-415: The body, above the gut and notochord / spine . The basic pattern of the CNS is highly conserved throughout the different species of vertebrates and during evolution. The major trend that can be observed is towards a progressive telencephalisation: the telencephalon of reptiles is only an appendix to the large olfactory bulb , while in mammals it makes up most of the volume of the CNS. In the human brain,

7560-399: The body, including the eyes and head, as well as the limbs. Further, it is involved in motion that has been learned and perfected through practice, and it will adapt to new learned movements. Despite its previous classification as a motor structure, the cerebellum also displays connections to areas of the cerebral cortex involved in language and cognition . These connections have been shown by

7680-408: The body. Such functions may engage the heart , blood vessels , and pupils , among others. The brainstem also holds the reticular formation , a group of nuclei involved in both arousal and alertness . The cerebellum lies behind the pons. The cerebellum is composed of several dividing fissures and lobes. Its function includes the control of posture and the coordination of movements of parts of

7800-403: The body. This is different from residual limb pain (RLP) that is often experienced by people with amputations. While RLP occurs in the remaining or residual body part, the pain or sensation associated with PLS can be experienced in the entire limb or just one portion of the missing limb. Phantom limb can also present itself in two ways: phantom limb pain or phantom limb sensations. Phantom limb pain

7920-403: The brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals —that is, all multicellular animals except sponges and diploblasts . It is a structure composed of nervous tissue positioned along the rostral (nose end) to caudal (tail end) axis of the body and may have an enlarged section at

8040-408: The brain stem nuclei, particularly the noradrenergic nuclei stimulate CRH release. Other regions of the hypothalamus both directly and indirectly inhibit HPA axis activity. Hypothalamic neurons involved in regulating energy balance also influence HPA axis activity through the release of neurotransmitters such as neuropeptide Y , which stimulates HPA axis activity. Generally, the amygdala stimulates, and

8160-464: The broader context of cognitive-consistency theory . Stress can have many profound effects on the human biological systems. Biology primarily attempts to explain major concepts of stress using a stimulus-response paradigm, broadly comparable to how a psychobiological sensory system operates. The central nervous system (brain and spinal cord) plays a crucial role in the body's stress-related mechanisms. Whether one should interpret these mechanisms as

8280-429: The central nervous system can cause severe illness and, when malignant , can have very high mortality rates. Symptoms depend on the size, growth rate, location and malignancy of tumors and can include alterations in motor control, hearing loss, headaches and changes in cognitive ability and autonomic functioning. Specialty professional organizations recommend that neurological imaging of the brain be done only to answer

8400-440: The cerebral hemispheres, among others: the cortex, basal ganglia, amygdala and hippocampus. The hemispheres together control a large portion of the functions of the human brain such as emotion, memory, perception and motor functions. Apart from this the cerebral hemispheres stand for the cognitive capabilities of the brain. Connecting each of the hemispheres is the corpus callosum as well as several additional commissures. One of

8520-409: The consequent adaptive response. Chronic stress, and a lack of coping resources available, or used by an individual, can often lead to the development of psychological issues such as delusions , depression and anxiety (see below for further information). Chronic stress also causes brain atrophy , which is the loss of neurons and the connections between them. It affects the part of the brain that

8640-450: The demands that bosses or family members may make. A person's capacity to tolerate the source of stress may be increased by thinking about another topic such as a hobby, listening to music, or spending time in a wilderness . A way to control stress is first dealing with what is causing the stress if it is something the individual has control over. Other methods to control stress and reduce it can be: to not procrastinate and leave tasks for

8760-425: The digestive system, secretion of the epinephrine and cortisol from the adrenal medulla, and relaxation of the bladder wall. The parasympathetic nervous response, "rest and digest", involves return to maintaining homeostasis, and involves miosis , bronchoconstriction , increased activity of the digestive system, and contraction of the bladder walls. Complex relationships between protective and vulnerability factors on

8880-419: The dorsal horn of the spinal cord, which deals with processing somatosensory information, due to increased activity from the peripheral nociceptors. Peripheral nociceptors are sensory neurons that alert us to potentially damaging stimuli. There are theories that the phantom limb phenomenon may relate to reorganization of the somatosensory cortex after the limb is removed. When the body receives tactile input near

9000-474: The effect of childhood home stress on psychological illness, cardiovascular illness and adaption have been observed. ANS related mechanisms are thought to contribute to increased risk of cardiovascular disease after major stressful events. The HPA axis is a neuroendocrine system that mediates a stress response. Neurons in the hypothalamus, particularly the paraventricular nucleus , release vasopressin and corticotropin releasing hormone , which travel through

9120-828: The effects that acute stressors have on the immune system may be increased when there is perceived stress and/or anxiety due to other events. For example, students who are taking exams show weaker immune responses if they also report stress due to daily hassles. While responses to acute stressors typically do not impose a health burden on young, healthy individuals, chronic stress in older or unhealthy individuals may have long-term effects that are detrimental to health. Acute time-limited stressors, or stressors that lasted less than two hours, results in an up regulation of natural immunity and down regulation of specific immunity . This type of stress saw in increase in granulocytes , natural killer cells , IgA , Interleukin 6 , and an increase in cell cytotoxicity. Brief naturalistic stressors elicit

9240-542: The experience of the body is created by a wide network of interconnecting neural structures, which he called the "neuromatrix". Pons and colleagues (1991) at the National Institutes of Health (NIH) showed that the primary somatosensory cortex in macaque monkeys undergoes substantial reorganization after the loss of sensory input. Hearing about these results, Vilayanur S. Ramachandran hypothesized that phantom limb sensations in humans could be due to reorganization in

9360-520: The front, the mesencephalon , and, between the mesencephalon and the spinal cord, the rhombencephalon . (By six weeks in the human embryo) the prosencephalon then divides further into the telencephalon and diencephalon ; and the rhombencephalon divides into the metencephalon and myelencephalon . The spinal cord is derived from the posterior or 'caudal' portion of the neural tube. As a vertebrate grows, these vesicles differentiate further still. The telencephalon differentiates into, among other things,

9480-439: The hand and sensory information from digging their nails into their palm. These memories remain due to previous neural connections in the brain. Despite the term "phantom limb" not being coined until 1871 by a physician named Silas Weir Mitchell , there have been earlier reports of the phenomenon. One of the first known medical descriptions of the phantom limb phenomenon was written by a French military surgeon, Ambroise Pare , in

9600-407: The hippocampus and decline of memory that many older adults start to experience with age. These mechanisms and processes may therefore contribute to age-related disease, or originate risk for earlier-onset disorders. For instance, extreme stress (e.g. trauma) is a requisite factor to produce stress-related disorders such as post-traumatic stress disorder. Chronic stress also shifts learning, forming

9720-454: The human brain's somatosensory cortex. Ramachandran and colleagues illustrated this hypothesis by showing that stroking different parts of the face led to perceptions of being touched on different parts of the missing limb. Later brain scans of amputees showed the same kind of cortical reorganization that Pons had observed in monkeys. Ramachandran have also performed the world's first phantom limb amputation surgeries by asking patients to visualize

9840-469: The hypophysial portal vessel where they travel to and bind to the corticotropin-releasing hormone receptor on the anterior pituitary gland . Multiple CRH peptides have been identified, and receptors have been identified on multiple areas of the brain, including the amygdala. CRH is the main regulatory molecule of the release of ACTH. The secretion of ACTH into systemic circulation allows it to bind to and activate Melanocortin receptor , where it stimulates

9960-567: The idea of stress. In biology , most biochemical processes strive to maintain equilibrium (homeostasis), a steady state that exists more as an ideal and less as an achievable condition. Environmental factors, internal or external stimuli, continually disrupt homeostasis; an organism's present condition is a state of constant flux moving about a homeostatic point that is that organism's optimal condition for living. Factors causing an organism's condition to diverge too far from homeostasis can be experienced as stress. A life-threatening situation such as

10080-487: The information out. The spinal cord relays information up to the brain through spinal tracts through the final common pathway to the thalamus and ultimately to the cortex. Apart from the spinal cord, there are also peripheral nerves of the PNS that synapse through intermediaries or ganglia directly on the CNS. These 12 nerves exist in the head and neck region and are called cranial nerves . Cranial nerves bring information to

10200-562: The internal distribution of a force exerted on a material body, resulting in strain . In the 1920s and '30s, biological and psychological circles occasionally used "stress" to refer to a physiological or environmental perturbation that could cause physiological and mental "strain". The amount of strain in reaction to stress depends on the resilience . Excessive strain would appear as illness. Walter Cannon used it in 1926 to refer to external factors that disrupted what he called homeostasis . But "...stress as an explanation of lived experience

10320-460: The last minute, do things you like, exercise, do breathing routines, go out with friends, and take a break. Having support from a loved one also helps a lot in reducing stress. One study showed that the power of having support from a loved one, or just having social support, lowered stress in individual subjects. Painful shocks were applied to married women's ankles. In some trials women were able to hold their husband's hand, in other trials they held

10440-427: The lines of continual activation of the stress response, stress that causes an allostatic shift in bodily functions, or just as "prolonged stress". For example, results of one study demonstrated that individuals who reported relationship conflict lasting one month or longer have a greater risk of developing illness and show slower wound healing. It can also reduce the benefits of receiving common vaccines. Similarly,

10560-422: The missing limb, which relieved pain, and in the long term completely removed the sensation of a phantom limb – the method is now known as the mirror therapy . Maladaptive changes in the cortex may account for some but not all phantom limb pain. Pain researchers such as Tamar Makin (Oxford) and Marshall Devor (Hebrew University, Jerusalem) argue that phantom limb pain is primarily the result of "junk" inputs from

10680-554: The most important parts of the cerebral hemispheres is the cortex , made up of gray matter covering the surface of the brain. Functionally, the cerebral cortex is involved in planning and carrying out of everyday tasks. The hippocampus is involved in storage of memories, the amygdala plays a role in perception and communication of emotion, while the basal ganglia play a major role in the coordination of voluntary movement. The PNS consists of neurons, axons, and Schwann cells . Oligodendrocytes and Schwann cells have similar functions in

10800-715: The natural regulatory capacity of an organism". The brain cannot live in an harsh family environment, it needs some sort of stability between another brain. People who have reported being raised in harsh environments such as verbal and physical aggression have showed a more immune dysfunction and more metabolic dysfunction. Indeed, in 1995 Toates already defined stress as a "chronic state that arises only when defense mechanisms are either being chronically stretched or are actually failing," while according to Ursin (1988) stress results from an inconsistency between expected events ("set value") and perceived events ("actual value") that cannot be resolved satisfactorily, which also puts stress into

10920-1079: The neocortex of mice is only about 1/100 that of monkeys, and that of monkeys is only about 1/10 that of humans. In addition, rats lack convolutions in their neocortex (possibly also because rats are small mammals), whereas cats have a moderate degree of convolutions, and humans have quite extensive convolutions. Extreme convolution of the neocortex is found in dolphins , possibly related to their complex echolocation . There are many CNS diseases and conditions, including infections such as encephalitis and poliomyelitis , early-onset neurological disorders including ADHD and autism , seizure disorders such as epilepsy , headache disorders such as migraine , late-onset neurodegenerative diseases such as Alzheimer's disease , Parkinson's disease , and essential tremor , autoimmune and inflammatory diseases such as multiple sclerosis and acute disseminated encephalomyelitis , genetic disorders such as Krabbe's disease and Huntington's disease , as well as amyotrophic lateral sclerosis and adrenoleukodystrophy . Lastly, cancers of

11040-454: The neurons and tissue of the CNS and the peripheral nervous system (PNS). The CNS is composed of white and gray matter . This can also be seen macroscopically on brain tissue. The white matter consists of axons and oligodendrocytes , while the gray matter consists of neurons and unmyelinated fibers. Both tissues include a number of glial cells (although the white matter contains more), which are often referred to as supporting cells of

11160-423: The only vertebrates to possess the evolutionarily recent, outermost part of the cerebral cortex (main part of the telencephalon excluding olfactory bulb) known as the neocortex . This part of the brain is, in mammals, involved in higher thinking and further processing of all senses in the sensory cortices (processing for smell was previously only done by its bulb while those for non-smell senses were only done by

11280-413: The pain can be made worse by stress , anxiety and weather changes . Exposure to extreme weather conditions, especially below freezing temperatures, can cause increased sensitivity to the sensation. Phantom limb pain is usually intermittent, but can be continuous in some cases. The frequency and intensity of attacks usually declines with time. Repressed memories in phantom limbs could potentially explain

11400-433: The perception of senses. All in all 31 spinal nerves project from the brain stem, some forming plexa as they branch out, such as the brachial plexa , sacral plexa etc. Each spinal nerve will carry both sensory and motor signals, but the nerves synapse at different regions of the spinal cord, either from the periphery to sensory relay neurons that relay the information to the CNS or from the CNS to motor neurons, which relay

11520-408: The peripheral nervous system. Despite a great deal of research on the underlying neural mechanisms of phantom limb pain there is still no clear consensus as to its cause. Both the brain and the peripheral nervous system may be involved. Research continues into more precise mechanisms and explanations. Phantom limb syndrome (PLS) is a sensation that the amputated or missing limb is still attached to

11640-418: The person with it (Arnold. E and Boggs. K. 2007). Some common categories and examples of stressors include: Physiologists define stress as how the body reacts to a stressor - a stimulus, real or imagined. Acute stressors affect an organism in the short term; chronic stressors over the longer term. The general adaptation syndrome (GAS), developed by Hans Selye, is a profile of how organisms respond to stress; GAS

11760-399: The phylum Platyhelminthes (flatworms), have the simplest, clearly defined delineation of a nervous system into a CNS and a PNS . Their primitive brains, consisting of two fused anterior ganglia, and longitudinal nerve cords form the CNS. Like vertebrates, have a distinct CNS and PNS. The nerves projecting laterally from the CNS form their PNS. A molecular study found that more than 95% of

11880-601: The postganglionic nerves, which is controlled by preganglionic neurons originating in the intermediolateral cell column . The ANS receives inputs from the medulla , hypothalamus , limbic system , prefrontal cortex , midbrain and monoamine nuclei . The activity of the sympathetic nervous system drives what is called the "fight or flight" response. The fight or flight response to emergency or stress involves mydriasis , increased heart rate and force contraction, vasoconstriction , bronchodilation , glycogenolysis , gluconeogenesis , lipolysis , sweating , decreased motility of

12000-496: The prefrontal cortex and hippocampus attenuate, HPA axis activity; however, complex relationships do exist between the regions. The immune system may be heavily influenced by stress. The sympathetic nervous system innervates various immunological structures, such as bone marrow and the spleen , allowing for it to regulate immune function. The adrenergic substances released by the sympathetic nervous system can also bind to and influence various immunological cells, further providing

12120-439: The problem that affects the overall appraisal of stressfulness. Further, coping is flexible in that, in general, the individual examines the effectiveness of the coping on the situation; if it is not having the desired effect, they will, in general, try different strategies. Both negative and positive stressors can lead to stress. The intensity and duration of stress changes depending on the circumstances and emotional condition of

12240-510: The rate of phantom sensations in cis men post-penectomy. Similarly, subjects who had undergone mastectomy reported experiencing phantom breasts; these reports were substantially less common among post- operative transgender men. Hanyu-Deutmeyer AA, Cascella M, Varacallo M. Phantom Limb Pain. 2023 Aug 4. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 28846343. Stress (medicine) Stress , whether physiological , biological or psychological ,

12360-430: The reason for existing sensations after amputation. Specifically, there have been several reports from patients of painful clenching spasms in the phantom hand with the feeling of their nails digging into their palms. The motor output is amplified due to the missing limb; therefore, the patient may experience the overflow of information as pain. The patient contains repressed memories from previous motor commands of clenching

12480-460: The release of steroid hormones . Steroid hormones bind to glucocorticoid receptors in the brain, providing negative feedback by reducing ACTH release. Some evidence supports a second long term feedback that is non-sensitive to cortisol secretion. The PVN of the hypothalamus receives inputs from the nucleus of the solitary tract , and lamina terminalis . Through these inputs, it receives and can respond to changes in blood. The PVN innervation from

12600-545: The removal of body parts other than the limbs, e.g. after amputation of the breast , extraction of a tooth (phantom tooth pain) or removal of an eye ( phantom eye syndrome ). Phantom sensations have been noted in the transgender population. Some people who have undergone sex reassignment surgery (SRS) have reported the sensation of phantom genitals. The reports were less common among post- operative transgender women , but did occur in transgender men . Phantom penises in pre-SRS transgender men have been documented to be similar to

12720-403: The residual limb, the brain is convinced that the sensory input was received from the amputated limb because another brain region took over. Reorganization has been thought to be related to sensory-discriminative parts of pain as well as the affective-emotional parts of it (I.e., insula, the anterior cingulate cortex, and the frontal cortices). Phantom sensations can also occur when there has been

12840-432: The rostral end which is a brain. Only arthropods , cephalopods and vertebrates have a true brain, though precursor structures exist in onychophorans , gastropods and lancelets . The rest of this article exclusively discusses the vertebrate central nervous system, which is radically distinct from all other animals. In vertebrates , the brain and spinal cord are both enclosed in the meninges . The meninges provide

12960-497: The sixteenth century. Pare noticed that some of his patients continued reporting pain in the removed limb after he performed the amputation. For many years, the dominant hypothesis for the cause of phantom limbs was irritation in the peripheral nervous system at the amputation site ( neuroma ). By the late 1980s, Ronald Melzack had recognized that the peripheral neuroma account could not be correct, because many people born without limbs also experienced phantom limbs. According to Melzack

13080-410: The size, shape, or position of the amputated body part (i.e., feeling as if your hand is in a twisted position). Exteroceptive phantom sensations are related to sensations perceived to be felt by the amputated body part (i.e., feelings of touch, pressure, tingling, temperature, itch, and vibrations). An additional sensation that some people with amputations experience is known as telescoping. Telescoping

13200-455: The skull, and protected by the cranium. The spinal cord is continuous with the brain and lies caudally to the brain. It is protected by the vertebrae . The spinal cord reaches from the base of the skull, and continues through or starting below the foramen magnum , and terminates roughly level with the first or second lumbar vertebra , occupying the upper sections of the vertebral canal . Microscopically, there are differences between

13320-452: The sorting of information that will reach cerebral hemispheres ( neocortex ). Apart from its function of sorting information from the periphery, the thalamus also connects the cerebellum and basal ganglia with the cerebrum. In common with the aforementioned reticular system the thalamus is involved in wakefulness and consciousness, such as though the SCN . The hypothalamus engages in functions of

13440-431: The spinal cord to the brain pass through here. Regulatory functions of the medulla nuclei include control of blood pressure and breathing . Other nuclei are involved in balance , taste , hearing , and control of muscles of the face and neck . The next structure rostral to the medulla is the pons, which lies on the ventral anterior side of the brainstem. Nuclei in the pons include pontine nuclei which work with

13560-403: The stress experienced is severe is a cause of change psychologically to the detriment of the well-being of the individual, such that symptomatic derealization and depersonalization , and anxiety and hyperarousal , are experienced. The International Classification of Diseases includes a group of mental and behavioral disorders which have their aetiology in reaction to severe stress and

13680-413: The telencephalon covers most of the diencephalon and the entire mesencephalon . Indeed, the allometric study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through cranial endocasts . Mammals – which appear in the fossil record after the first fishes, amphibians, and reptiles – are

13800-410: The tissue for repair and promoting recruitment of certain cells to the wound area. Consistent with the fact that stress alters the production of cytokines, Graham et al. found that chronic stress associated with care giving for a person with Alzheimer's disease leads to delayed wound healing. Results indicated that biopsy wounds healed 25% more slowly in the chronically stressed group, or those caring for

13920-532: The translation of stress into physiological and psychological changes. The autonomic nervous system (ANS), as mentioned above, plays an important role in translating stress into a response. The ANS responds reflexively to both physical stressors (for example baroreception ), and to higher level inputs from the brain. The ANS is composed of the parasympathetic nervous system and sympathetic nervous system , two branches that are both tonically active with opposing activities. The ANS directly innervates tissue through

14040-453: The use of medical imaging techniques, such as functional MRI and Positron emission tomography . The body of the cerebellum holds more neurons than any other structure of the brain, including that of the larger cerebrum , but is also more extensively understood than other structures of the brain, as it includes fewer types of different neurons. It handles and processes sensory stimuli, motor information, as well as balance information from

14160-421: The visual and auditory systems are located in the midbrain, including control of automatic eye movements. The brainstem at large provides entry and exit to the brain for a number of pathways for motor and autonomic control of the face and neck through cranial nerves, Autonomic control of the organs is mediated by the tenth cranial nerve . A large portion of the brainstem is involved in such autonomic control of

14280-451: The vulnerability to stressors is particularly high. This can lead to psychiatric and physical diseases which have long term impacts on an individual. Chronic stress is seen to affect the parts of the brain where memories are processed through and stored. When people feel stressed, stress hormones get over-secreted, which affects the brain. This secretion is made up of glucocorticoids , including cortisol, which are steroid hormones that

14400-576: Was first recognized by Hans Selye (1907–1982) in 1926. In 1951 a commentator loosely summarized Selye's view of stress as something that "...in addition to being itself, was also the cause of itself, and the result of itself". First to use the term in a biological context, Selye continued to define stress as "the non-specific response of the body to any demand placed upon it". Neuroscientists such as Bruce McEwen and Jaap Koolhaas believe that stress, based on years of empirical research, "should be restricted to conditions where an environmental demand exceeds

#106893