sympatho-adrenal response

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 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.

• Overview of the Endocrine System

  • For example, the pineal gland, located at the base of the brain, secretes the hormone melatonin, responsible for regulating sleep patterns.
  • Endocrine signaling is typically slow to initiate but is prolonged in response; this provides a counterpoint to the more rapid and short-lived nervous system signals.
  • The major endocrine glands include the pituitary, pineal, ovaries, testes, thyroid, hypothalamus and adrenal glands, additionally other tissues such as the kidney and liver also display secondary adrenal functions.

• The Fight-or-Flight Response

  • The fight-or-flight response (also called the acute stress response) was first described by Walter Bradford Cannon.
  • This response was later recognized as the first stage of a general adaptation syndrome that regulates stress responses among vertebrates and other organisms.
  • Upon sensing a threat the brain stimulates the hypothalamus to secrete corticotropin-releasing hormone that induces adrenocorticotropic hormone from the pituitary to stimulate the release of cortisol from the adrenal cortex to increase blood sugar levels in preparation for fight or flight.
  • Simultaneously, the adrenal gland also releases catecholamine hormones, such as adrenaline or noradrenaline, into the blood stream.
  • The stress response halts or slows down various processes, such as sexual responses and digestive systems, to focus on the stressor situation.

• Aging and the Endocrine System

  • This decrease in responsiveness can be attributed to a decrease in IGF-I signaling pathways with advanced cell age.
  • The hypothalmus-pituitary-adrenal pathway plays an integral role in controlling immune function.
  • Two adrenal hormones, DHEA and cortisol have opposing effects on immune system function with DHEA generally enhancing immunity and cortisol suppressing it.
  • DHEA is released from the adrenal cortex in response to adrenocorticotrophic hormone (ACTH).
  • Glucocorticoids (GCs) such as cortisol also respond to ACTH and are released from the adrenal glands.

• Location and External Anatomy of the Kidneys

  • They are also responsible for the reabsorption of water, glucose, and amino acids, and will maintain the balance of these molecules in the body.
  • Resting on top of each kidney is an adrenal gland (adrenal meaning on top of renal), which are involved in some renal system processes despite being a primarily endocrine organ.
  • The upper parts of the kidneys are partially protected by lower ribs, and each whole kidney and adrenal gland are surrounded by two layers of fat (the perirenal and pararenal fat) and the renal fascia.