Adrenal Glands

• Adrenal structure

  found lying anterior to kidneys - one on each side of body

  each gland is divided into outer adrenal cortex + inner adrenal medulla

  • both regions are well supplied with blood vessels + produce hormones which are secreted directly into blood vessels

  
• Adrenal Cortex

  3 distinct layers

  • zona glomerulosa - outermost layer, which secretes mineralcorticoids such as aldosterone
  • zona fasciculata - middle layer, which secretes glucocorticoids such as cortisol
  • zona reticularis - innermost layer, Tu ought to secrete precursor molecules that are used to make sex hormones
• Adrenal medulla

  found at centre of adrenal gland + secretes adrenaline + noradrenaline

  
• Hormones from adrenal cortex

  adrenal cortex uses cholesterol to produce a range of hormones

  the action of steroidal hormones :

  1. steroid hormones passes through cell membrane of target cell
  2. steroid hormone binds with a specific receptor (with a complementary shape) in cytoplasm
  3. receptor-steroid hormone complex enters nucleus of target cell + binds to another specific receptor on chromosomal material
  4. binding stimulates production of messenger RNA (mRNA) molecules, which code for production of proteins
• hormones from adrenal cortex have a variety of roles

  • mineralcorticoids (e.g. aldosterone) from zona glomerulosa helps to control the concentration of sodium and potassium ions in blood contributing to maintain blooding pressure

  → aldosterone acts on cells of distal tubules + collecting ducts in the kidney; increases absorption of sodium ions, decreases absorption of potassium ions + increases water retention so increasing blood pressure
• hormones from adrenal cortex have a variety of roles 2

  • glucocorticoids (e.g. cortisol) from zona fasciculata help to control the metabolism of carbohydrates, fats and proteins in liver

  cortisol is released in response to stress or as a result of a low blood glucose concentration , stimulating production of glucose from stored compounds (especially glycogen, fats and proteins) in liver
• hormones from adrenal cortex have a variety of roles 3

  • cortisol may also be released by zona reticularis but if correct enzymes are not present for the release of cortisol, then zona reticularis released precursor androgens into blood

  → these are taken up by the ovaries or tested + converted to sex hormones which help development of the secondary sexual characteristics + regulate production of gametes
• Adrenaline from adrenal medulla

  medulla is where adrenaline is released

  • adrenaline is a polar molecule derived from amino acids tyrosine meaning g it cannot enter through plasma membrane of target cell

  → many cells + tissues have adrenaline receptors so therefore the effects of adrenaline are widespread and role of adrenaline is to prepare the body for activity including following effects:

  A) vasoconstriction

  B) inhibiting

  C) body hair

  D) increasing

  E) smooth muscle

  
• adrenaline is known as ‘fight or flight’ hormone but its role are wider than this + can be described as arousal, flight fight and flirt

  adrenaline junkies is someone who appears to be addicted to effects of adrenaline + they appear to enjoy stressful activities or risky situations that cause release of adrenaline giving them a ‘high’
• Adrenal Medulla


  The region located in the center of the Adrenal Gland, responsible for secreting Adrenaline and Noradrenaline.