sympatho-adrenal response

(noun)

Also called the fight-or-flight response, this activates the secretion of adrenaline (epinephrine) and, to a lesser extent, noradrenaline (norepinephrine).

Related Terms

Examples of sympatho-adrenal response in the following topics:

  • The Stress Response

    • The body's stress response is mediated by the sympathetic nervous system and the hypothalmic-pituitary-adrenal (HPA) axis.
    • The body's stress response is mediated by the interplay between the sympathetic nervous system (SNS) and the hypothalmic-pituitary-adrenal (HPA) axis.
    • The SNS plays a key role in mediating the neural response to stress known as the fight-or-flight response.
    • This response is also referred to as the sympatho-adrenal response of the body owing to the fact that the preganglionic sympathetic fibers that end in the adrenal medulla secrete acetylcholine, which activates the release of adrenaline and noradrenaline from the medulla.
    • The hypothalmic-pituitary-adrenal (HPA) axis is an endocrine cascade that mediates several aspects of physiological stress, including responses to acute stressors (i.e., fight-or-flight response) but it also causes chronic stress.

  • Sympathetic Responses

    • The SNS is perhaps best known for mediating the neuronal and hormonal stress response commonly known as the fight-or-flight response, also known as sympatho-adrenal response of the body.
    • This occurs as the preganglionic sympathetic fibers that end in the adrenal medulla secrete acetylcholine, which activates the secretion of adrenaline (epinephrine), and to a lesser extent noradrenaline (norepinephrine).
    • Therefore, this response is mediated directly via impulses transmitted through the sympathetic nervous system, and also indirectly via catecholamines that are secreted from the adrenal medulla, and acts primarily on the cardiovascular system.
    • This response was later recognized as the first stage of a general adaptation syndrome that regulates stress responses among vertebrates and other organisms.
    • In current times, these responses persist, but fight-and-flight responses have assumed a wider range of behaviors.

  • Overview of the Adrenal Glands

    • They are chiefly responsible for releasing three classes of hormones:  
    • Along with catecholamines (adrenaline), these hormones control a variety of functions including kidney function, metabolism, fight-or-flight response, and sex hormone levels.
    • In humans, the right adrenal gland is triangular shaped, while the left adrenal gland is semilunar shaped.
    • Each adrenal gland has two distinct structures, the outer adrenal cortex and the inner medulla—both produce hormones.
    • The adrenal glands are triangular-shaped organs on top of the kidneys.

  • Adrenal Medulla

    • The adrenal medulla is the core of the adrenal glands, and is surrounded by the adrenal cortex.
    • The adrenal medulla is responsible for the production of catecholamines, derived from the amino acid tyrosine.
    • To carry out this response, the adrenal medulla receives input from the sympathetic nervous system through nerve fibers originating in the thoracic spinal cord from T5–T11.
    • All of these effects are characteristic of the fight-or-flight response.
    • The adrenal medulla sits below the three layers of the adrenal cortex and is innervated by nerve fibers.

  • Adrenal Glands

    • Adrenal glands are composed of the adrenal cortex and medulla; both produce hormones that control essential body functions and responses.
    • Through hormonal secretions, the adrenal glands regulate many essential functions in the body, including biochemical balances that influence athletic training and general stress response.
    • The adrenal glands consist of an outer adrenal cortex and an inner adrenal medulla, which secrete different hormones.
    • The hormones made by the adrenal cortex supply long-term responses to stress.
    • These neural impulses originate from the hypothalamus in response to stress to prepare the body for the fight-or-flight response.

  • Adrenal Cortex

    • The adrenal cortex is devoted to the synthesis of corticosteroid and androgen hormones.
    • It increases blood glucose levels in response to stress, by inhibiting glucose uptake into muscle and fat cells
    • Androstenedione (Andro): an androgenic steroid produced by the testes, adrenal cortex, and ovaries.
    • The layers of the adrenal cortex are shown in this figure.
    • Differentiate among the zones (and hormones produced) of the adrenal cortex

  • Sympathetic Nervous System

    • Sympathetic ganglia are the ganglia of the sympathetic nervous system that initiate fight-or-flight, stress-mediated responses.
    • They deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response.
    • This response is also known as the sympathetico-adrenal response because the pre-ganglionic sympathetic fibers that end in the adrenal medulla—like all sympathetic fibers—secrete acetylcholine.
    • This secretion activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine) from the adrenal medulla.
    • Therefore, this response is mediated directly via impulses transmitted through the sympathetic nervous system, and indirectly via catecholamines secreted from the adrenal medulla, and acts primarily on the cardiovascular system.

  • Hormonal Regulation of Stress

    • The adrenal glands respond to either short-term or long-term stressors by releasing different hormones that act differently on the body.
    • Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress responses via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary.
    • Long-term stress response differs from short-term stress response.
    • The adrenal cortex is stimulated by ACTH to release steroid hormones called corticosteroids.
    • Describe the role of the adrenal glands in the "fight-or-flight" response and the body's reaction to stress

  • The Endocrine System and Stress

    • Stress is the simple name for what happens when the body's emergency response is activated; a stressful event is one that activates the sympathetic (fight-or-flight) nervous system.
    • The hypothalamic-pituitary-adrenal (HPA or HTPA) axis is a complex set of direct influences and steroid-producing feedback interactions among the hypothalamus, the pituitary gland, and the adrenal glands.
    • All vertebrates have an HPA, but the steroid-producing stress response is so important that even invertebrates and monocellular organisms have analogous systems.
    • The ACTH acts on the adrenal cortex, which produces steroids—in humans, primarily the steroid cortisol.
    • Studies on people show that the HPA axis is activated in different ways during chronic stress—depending on the type of stressor, the person's response to the stressor, and other factors.

  • Other Hormonal Controls for Osmoregulation

    • The renin-angiotensin-aldosterone system (RAAS) stabilizes blood pressure and volume via the kidneys, liver, and adrenal cortex.
    • Angiotensin II raises blood pressure by constricting blood vessels and also triggers the release of the mineralocorticoid aldosterone from the adrenal cortex.
    • Mineralocorticoids are hormones synthesized by the adrenal cortex that affect osmotic balance.
    • Patients who have Addison's disease have a failing adrenal cortex and cannot produce aldosterone.
    • It is released by cells in the atrium of the heart in response to high blood pressure and in patients with sleep apnea.