The "fight-or-flight response", also called the "fight-or-flight-or-freeze response", the "fright, fight or flight response", "hyperarousal" or the "acute stress response", was first described by Walter Cannon Walter Bradford Cannon was an American physiologist, Professor and chairman of the Department of Physiology at Harvard Medical School, who developed secondarily to Claude Bernard the concept of homeostasis , and popularized it in his book The Wisdom of the Body, published in 1932 by W. W. Norton, New York in 1929.^[1][2][3]

His theory In philosophy, theory refers to contemplation or speculation, as opposed to action. Theory is especially often contrasted to "practice" (Greek praxis, πρᾶξις) a concept that in its original Aristotelian context referred to actions done for their own sake, but can also refer to "technical" actions instrumental to some states that animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also react to threats with a general discharge of the sympathetic nervous system The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's resources under stress; to induce the flight-or-fight response. It is, however, constantly active at a basal level in order to maintain homeostasis, priming the animal for fighting Combat, or fighting, is purposeful violent conflict meant to establish dominance over the opposition or fleeing. This response was later recognized as the first stage of a general adaptation syndrome Stress is a term in psychology and biology, first coined in the 1930s, which has in more recent decades become a commonplace of popular parlance. It refers to the consequence of the failure of an organism – human or animal – to respond appropriately to emotional or physical threats, whether actual or imagined that regulates stress Stress is a term in psychology and biology, first coined in the 1930s, which has in more recent decades become a commonplace of popular parlance. It refers to the consequence of the failure of an organism – human or animal – to respond appropriately to emotional or physical threats, whether actual or imagined responses among vertebrates Vertebrates are members of the subphylum Vertebrata, chordates with backbones and spinal columns. About 58,000 species of vertebrates have been currently described. Vertebrata is the largest subphylum of chordates, and contains many familiar groups of large land animals. Vertebrates are comprised of animals from the groups jawless fishs, bony fish, and other organisms In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many trillions of cells grouped into.

Physiology of the stress response

Normally, when a person is in a serene, unstimulated Stimulation is the action of various agents on muscles, nerves, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity state, the "firing An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a stereotyped trajectory. Action potentials occur in several types of excitable cells, including neurons, muscle cells, and endocrine cells. In neurons, they play a central role in cell-to-cell communication. In" of neurons A neuron (pronounced /ˈnjʊərɒn/ NOOR-on, also known as a neurone or nerve cell) is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core in the locus coeruleus The Locus coeruleus, also spelled locus caeruleus, is a nucleus in the brain stem involved with physiological responses to stress and panic. It was discovered in the 1700s by Félix Vicq-d'Azyr is minimal. A novel stimulus In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity. When a stimulus is applied to a sensory receptor, it elicits or influences a reflex via stimulus transduction. A stimulus is often the first component of a homeostatic (which could include a perception In philosophy, psychology, and cognitive science, perception is the process of attaining awareness or understanding of sensory information. The word "perception" comes from the Latin words perceptio, percipio, and means "receiving, collecting, action of taking possession, apprehension with the mind or senses." of danger Risk concerns the deviation of one or more results of one or more future events from their expected value. Technically, the value of those results may be positive or negative. However, general usage tends to focus only on potential harm that may arise from a future event, which may accrue either from incurring a cost or by failing to attain some or an environmental Surroundings are the area around a given physical or geographical point or place. The exact definition depends on the field. Surroundings can also be used in geography and mathematics, as well as philosophy, with the literal or metaphorically extended definition stressor Stress is a term in psychology and biology, first coined in the 1930s, which has in more recent decades become a commonplace of popular parlance. It refers to the consequence of the failure of an organism – human or animal – to respond appropriately to emotional or physical threats, whether actual or imagined such as elevated sound levels Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water. The SI unit for sound pressure p is the pascal (symbol: Pa) or over-illumination Over-illumination is the presence of lighting intensity beyond that required for a specified activity. Over-illumination was commonly ignored between 1950 and 1995, especially in office and retail environments; only since then has the interior design community begun to reconsider this practice), once perceived, is relayed from the sensory cortex The sensory cortex is an umbrella term for the primary and secondary cortexes of the different senses: the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the somatosensory cortex on the postcentral gyrus, the olfactory cortex on the entorhinal and pyriform cortexes, and the gustatory cortex laterally on the of the brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary through the hypothalamus The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis) to the brainstem In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves. Though small, this is an extremely important part of the brain as the nerve connections of the motor and.

That route of signaling In biology, signal transduction is a mechanism that converts a mechanical or chemical stimulus to a cell into a specific cellular response. Signal transduction starts with a signal to a receptor, and ends with a change in cell function increases the rate of noradrenergic Norepinephrine (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or NAd) is a catecholamine with multiple roles including as a hormone and a neurotransmitter activity in the locus coeruleus, and the person becomes alert Alertness is the state of paying close and continuous attention, being watchful and prompt to meet danger or emergency, or being quick to perceive and act. It is related to psychology as well as to physiology. A lack of alertness is a symptom of a number of conditions, including narcolepsy, attention deficit disorder, chronic fatigue syndrome, and attentive Attention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources to the environment. Similarly, an abundance of catecholamines Catecholamines are sympathomimetic "fight-or-flight" hormones released by the adrenal glands in response to stress. They are part of the sympathetic nervous system at neuroreceptor In biochemistry, a receptor is a protein molecule, embedded in either the plasma membrane or the cytoplasm of a cell, to which one or more specific kinds of signaling molecules may attach. A molecule which binds to a receptor is called a ligand, and may be a peptide (short protein) or other small molecule, such as a neurotransmitter, a hormone, a sites facilitates reliance on spontaneous or intuitive Intuition is the apparent ability to acquire knowledge without inference or the use of reason. “The word ‘intuition’ comes from the Latin word 'intueri', which is often roughly translated as meaning ‘to look inside’ or ‘to contemplate’." Intuition provides us with beliefs that we cannot necessarily justify. For this reason, it behaviors Behavior, or behaviour , refers to the actions of a system or organism , usually in relation to its environment, which includes the other systems or organisms around as well as the physical environment. It is the response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or often related to combat or escape.

If a stimulus is perceived as a threat, a more intense and prolonged discharge of the locus ceruleus activates the sympathetic division The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's resources under stress; to induce the flight-or-fight response. It is, however, constantly active at a basal level in order to maintain homeostasis of the autonomic nervous system The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal.^[4] This activation Activation in chemical sciences generally refers to the process whereby something is prepared or excited for a subsequent reaction is associated with specific physiological actions in the system, both directly and indirectly through the release of epinephrine Epinephrine is a hormone and neurotransmitter.. It increases heart rate, contracts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. Chemically, epinephrine is a catecholamine, a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine (adrenaline) and to a lesser extent norepinephrine Norepinephrine (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or NAd) is a catecholamine with multiple roles including as a hormone and a neurotransmitter from the medulla The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the inner most part of the adrenal gland, consisting of cells that secrete epinephrine, norepinephrine, and a small amount of dopamine in response to stimulation by sympathetic preganglionic neurons of the adrenal glands In mammals, the adrenal glands are the triangular-shaped endocrine glands that sit on top of the kidneys. They are chiefly responsible for releasing hormones in conjunction with stress through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline (epinephrine), respectively. The release In a neuron synaptic vesicles or neurotransmitter vesicles store various neurotransmitters that are released at the synapse. The release is regulated by a calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell. The area in the axon which holds groups of vesicles is a bouton is triggered by acetylcholine The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the motor division of the somatic nervous system. ( released from preganglionic sympathetic nerves In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers. The other major factor in the acute stress response is the hypothalamic-pituitary-adrenal axis The hypothalamic-pituitary-adrenal axis , also known as the limbic-hypothalamic-pituitary-adrenal axis (LHPA axis) and, occasionally, as the hypothalamic-pituitary-adrenal-gonadotropic axis, is a complex set of direct influences and feedback interactions among the hypothalamus (a hollow, funnel-shaped part of the brain), the pituitary gland (a pea-.^[5]

These catecholamine Catecholamines are sympathomimetic "fight-or-flight" hormones released by the adrenal glands in response to stress. They are part of the sympathetic nervous system hormones facilitate immediate physical reactions associated with a preparation for violent muscular Muscle is the contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause action. (Gleitman, et al., 2008) These include the following:

• Acceleration In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up. However, as a vector quantity, acceleration is also the of heart Cardiac dysrhythmia is a term for any of a large and heterogeneous group of conditions in which there is abnormal electrical activity in the heart. The heart beat may be too fast or too slow, and may be regular or irregular and lung It is not identical with hyperventilation - tachypnea may be necessary for a sufficient gas-exchange of the body, for example after exercise, in which case it is not hyperventilation action
• Paling Pallor is a reduced amount of oxyhemoglobin in skin or mucous membrane, a pale color which can be caused by illness, emotional shock or stress, stimulant use, lack of exposure to sunlight, anemia or genetics. It is more evident on the face and palms. It can develop suddenly or gradually, depending on the cause or flushing For a person to flush is to become markedly red in the face and often other areas of the skin, from various physiological conditions. Flushing is generally distinguished, despite a close physiological relation between them, from blushing, which is milder, generally restricted to the face, cheeks or ears, and generally assumed to reflect, or alternating between both
• Inhibition of stomach and upper-intestinal action (digestion slows down or stops)
• General effect on the sphincters of the body
• Constriction of blood vessels in many parts of the body
• Liberation of nutrients (particularly fat and glucose) for muscular action
• Dilation of blood vessels for muscles
• Inhibition of the lacrimal gland (responsible for tear production) and salivation
• Dilation of pupil (mydriasis)
• Relaxation of bladder
• Inhibition of erection
• Auditory exclusion (loss of hearing)
• Tunnel vision (loss of peripheral vision)
• Acceleration of instantaneous reflexes
• Shaking

Psychology of the stress response

A typical example of the stress response is a grazing zebra, calmly maintaining homeostasis. If the zebra sees a lion closing in for the kill, the stress response is activated. The escape requires intense muscular effort, supported by all of the body’s systems. The sympathetic nervous system’s activation provides for these needs. A similar example involving fight is of a cat about to be attacked by a dog. The cat shows accelerated heartbeat, piloerection (hair standing on end, normally for conservation of heat), and pupil dilation, all signs of sympathetic arousal (Gleitman et al., 2004).

Though Cannon, who first proposed the idea of fight-or-flight, provided considerable evidence of these responses in various animals, it subsequently became apparent that his theory of response was too simplistic. Animals respond to threats in many complex ways. Rats, for instance, try to escape when threatened, but will fight when cornered. Some animals stand perfectly still so that predators will not see them. Many animals freeze or play dead when touched in the hope that the predator will lose interest.

Others have more exotic self-protection methods. Some species of fish change color swiftly, to camouflage themselves. These responses are triggered by the sympathetic nervous system, but in order to fit the model of fight or flight, the idea of flight must be broadened to include escaping capture in either a physical way or in a sensory way. Thus, flight can be disappearing to another location or just disappearing in place. And often both fight and flight are combined in a given situation.

The fight or flight actions also have polarity - the individual can fight or flee against or away from something that is threatening, such as a hungry lion, or fight or fly for or towards something that is needed, such as the safety of the shore of a raging river.

A threat from another animal does not always result in immediate fight or flight. There may be a period of heightened awareness, during which each animal interprets behavioral signals from the other. Signs such as paling, piloerection, immobility, sounds, and body language communicate the status and intentions of each animal. There may be a sort of negotiation, after which fight or flight may ensue, but which might also result in playing, mating, or nothing at all. An example of this is kittens playing: each kitten shows the signs of sympathetic arousal, but they never inflict real damage.

Behavioral manifestations of fight-or-flight

In prehistoric times when the fight or flight response evolved, fight was manifested in aggressive, combative behavior and flight was manifested by fleeing potentially threatening situations, such as being confronted by a predator. In current times, these responses persist, but fight and flight responses have assumed a wider range of behaviors. For example, the fight response may be manifested in angry, argumentative behavior, and the flight response may be manifested through social withdrawal, substance abuse, and even television viewing. (Friedman & Silver 2007)

Males and females tend to deal with stressful situations differently. Males are more likely to respond to an emergency situation with aggression (fight), while females are more likely to flee (flight), turn to others for help, or attempt to defuse the situation – 'tend and befriend'. During stressful times, a mother is especially likely to show protective responses toward her offspring and affiliate with others for shared social responses to threat. (Taylor et al., 2000)

Negative effects of the stress response in humans

The stress response halts or slows down various processes such as sexual responses and digestive systems to focus on the stressor situation and typically causes negative effects like constipation, anorexia, erectile dysfunction, difficulty urinating, and difficulty maintaining sexual arousal.^{[citation needed]}. These are functions which are controlled by the parasympathetic nervous system and therefore suppressed by sympathetic arousal

Prolonged stress responses may result in chronic suppression of the immune system, leaving the body open to infections, however there is a short boost of the immune system shortly after the fight or flight response has been activated. This may be due to an ancient need to fight the infections in a wound that one may have received during interaction with a predator.

Stress responses are sometimes a result of mental disorders such as post-traumatic stress disorder, in which the individual shows a stress response when remembering a past trauma, and panic disorder, in which the stress response is activated by the catastrophic misinterpretations of bodily sensations.

See also

• Adrenaline Rush
• Acute stress reaction
• Anxiety
• Anxiety disorder
• Defense physiology
• Emotional dysregulation
• Panic attack
• Phobia
• Posttraumatic stress disorder
• Rest and digest
• Stressor
• Social anxiety
• Social anxiety disorder
• Tend and befriend
• Vasoconstriction
• Yerkes–Dodson law

External links

• Anatomy and Physiology I notes from Owensboro community college.

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