adrenal cortex

Examples of adrenal cortex in the following topics:

• Adrenal Medulla

  • The adrenal cortex is devoted to the synthesis of corticosteroid and androgen hormones.
  • 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.
  • The adrenal medulla secretes approximately 20% noradrenaline (norepinephrine) and 80% adrenaline (epinephrine).
  • 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.
  • The adrenal cortex comprises three zones, or layers: Zona glomerulosa (outer), Zona fasciculata and Zona reticularis.
  • 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

• Overview of the Adrenal Glands

  • In mammals, the adrenal glands (also known as the suprarenal glands) are endocrine glands that sit atop the kidneys.
  • 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 cortex mainly produces mineralcorticoids, glucocorticoids, and androgens, while the medulla chiefly produces adrenaline and nor-adrenaline.
  • The adrenal glands are triangular-shaped organs on top of the kidneys.

• 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.
  • 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.
  • ACTH acts on the adrenal cortices that produce glucocorticoid hormones, like cortisol, which is a stress hormone that exerts many effects throughout the body.
  • ACTH is then transported through the circulatory system to the adrenal cortex where it promotes the biosynthesis of corticosteroids like cortisol and cholesterol.

• The Fight-or-Flight Response

  • 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.

• Congenital Adrenal Hyperplasia

  • Congenital adrenal hyperplasia refers to an autosomal recessive disease caused by mutated genes for enzymes that produce cortisol from cholesterol.
  • Congenital adrenal hyperplasia (CAH) refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands (steroidogenesis).
  • Cortisol is an adrenal steroid hormone that is required for normal endocrine function.
  • Inefficient cortisol production results in rising levels of ACTH, which in turn induces overgrowth (hyperplasia) and overactivity of the steroid-producing cells of the adrenal cortex.
  • The defects causing adrenal hyperplasia are congenital (i.e., present at birth).

• Aging and the Endocrine System

  • 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.

• Adrenal Gland Disorders

  • Addison's disease and congenital adrenal hyperplasia can manifest as adrenal insufficiency.
  • Primary adrenal insufficiency is due to impairment of the adrenal glands.
  • Other cases are due to congenital adrenal hyperplasia or an adenoma (tumor) of the adrenal gland.
  • For chronic adrenal insufficiency, the major contributors are autoimmune adrenalitis, tuberculosis, AIDS, and metastatic disease.
  • Evaluate the types of adrenal insufficiency that lead to adrenal gland disorders

• Motor Areas

  • The motor areas of the brain are located in both hemispheres of the cortex.
  • Premotor cortex: Located anterior to the primary motor cortex and responsible for some aspects of motor control.
  • Posterior parietal cortex – Guides planned movements, spatial reasoning, and attention.
  • Various experiments examining the motor cortex map showed that each point in motor cortex influences a range of muscles and joints, indicating significant overlapping in the map.
  • $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.

• Stress and Disease

  • The regions of the brain involved in memory processing that are implicated in PTSD include the hippocampus, amygdala, and frontal cortex, while the heightened stress response is likely to involve the thalamus, hypothalamus, and locus coeruleus.
  • In depression, the hypothalamic-pituitary-adrenal (HPA) axis is up-regulated by a down-regulation of its negative feedback controls.
  • ACTH interacts with receptors on adrenocortical cells and cortisol is released from the adrenal glands.
  • An increase in noradrenaline in the frontal/prefrontal cortex modulates the action of selective noradrenaline re-uptake inhibition and improves mood.
  • Increasing noradrenaline transmission to other areas of the frontal cortex modulates attention.