13 - Functional morphology of the adrenal glands. Hormones of the adrenal medulla. Physiological effect and control of secretion of epinephrine and norepinephrine.

sections

amount of adrenal glands, location and surrounded by

parts of adrenal gland

3 zones of adrenal cortex and what they produce

adrenocorticotropic hromone

two catecholamines of adrenal medulla

tyrosine

phsyiological effect and control fo secretion of epinephrine and norepinephrine

amount of adrenal glands, location and surrounded by

• There are two adrenal glands

• located above each kidney

• surrounded by a fatty capsule

parts of adrenal gland

• Each adrenal gland is composed of two parts:

  • outer adrenal cortex

  • inner adrenal medulla

3 zones of adrenal cortex and what they produce

1. outer zone- mineralocorticoids (i.e. aldosterone – for regulation of salt and water levels in body which regulated blood pressure, Aldosterone acts on certain cells in the kidneys to increase their reabsorption of sodium ions from the urine.)

2. middle zone- glucocorticoids (e.g. cortisol - involved in stress response and regulates body metabolism- fats, resist stress, antinflamm)

3. Inner zone- androgens (eg. Testosterone- growth and male characteristics).

adrenocorticotropic hromone

secreted by the anterior pituitary gland, binds to receptors on adrenocortical cell of the adrenal cortex and stimulates secretion of cortisol- which helps to regulate body metabolism.

two catecholamines of adrenal medulla

norepinephrine and epinephrine.

These hormones participate in establishing characteristics of the fight or flight stress response

tyrosine

1. Tyrosine is taken up by chromaffin cells in the medulla

2. Tyrosine converted to norepinephrine and epinephrine.

3. Tyrosine→dopa→dopamine→norepinrphine→epinephrine

phsyiological effect and control fo secretion of epinephrine and norepinephrine

• The secretion of these hormones is stimulated by the release of acetylcholine from preganglionic sympathetic fibres which innervate the medulla.

• Trauma, Exercise and hypoglycaemia are factors which can trigger the release of these hormones.

  • Once secreted, the hormones bind to a-1, 2 and B 1,2, 3adrenergic receptors on target cells

  • to induce the same effect as that of direct sympathetic nervous stimulation.

• physiologic effects of epinephrine from the epinephrine secreting cells and norepinephrine :

  • A and NA increase blood pressure by increasing heart rate and constricting blood vessel

    • increase breathing rate

    • dilate respiratory passageways

    • decrease the rate of digestion

    • increase the efficiency of muscular contractions

    • increase blood sugar level, and stimulate the cellular metabolism

    • increase lipolysis