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THE ADRENAL GLANDS

 

  • Each one about the size of a walnut

  • Measure about 1½ ins high - 3 ins in length

  • Orange-colored, triangular shaped 

  • Situated on top of each kidney

  • Just underneath the last (12th) rib

Purpose: 

  • Help us cope with stress

  • Maintain salt levels in the blood 

  • Maintain blood pressure help control kidney function

  • Control overall fluid balance in the body

  • Increase our energy (release your energy stores for immediate use)

  • Reproduction

 

medulla - inner part of the Adrenal Gland

 

Secretes

  • Epinephrine – (adrenaline) 

  • Nor epinephrine - (nor-adrenaline) 

 

The FIGHT OR FLIGHT part of the ADRENALS 

Develops from neural tissue – so to do with the Nervous System.

When the ‘fight or flight’ is stimulated (during stressful situation), it initiates a sequence of nerve cell firing and chemical release that prepares our body for running or fighting.

Often hear about ‘superhuman’ things happening i.e. lifting a car in an emergency situation).

Adrenaline, nor adrenaline and cortisol (from the Glucocorticoids in the Adrenal Cortex) are released into the bloodstream.

 

When the body starts to use the ‘fight or flight’  

 

  • It wants to give you as much strength as possible - muscular action

  • Does this by boosting the supply of oxygen & glucose to the brain/muscles

 

This includes the following physical reactions:

  • Acceleration of heart and lung action

  • Closing down of stomach and intestinal action

  • Constriction of blood vessels in many parts of the body

  • Liberation of nutrients for muscular action

  • Dilation of blood vessels for muscles

  • Inhibition of tear glands and salivation

  • Dilation of pupil

  • Relaxation of bladder

  • Failure to have an erection

All the above is necessary to cope with stress.  

So, in a nutshell, it puts the body in a heightened state to react by:

  • Dilating the bronchi (air passages) – more oxygen released

  • Dilating the blood vessels (to the muscles – which get the oxygen)

  • Increase heart beat & contraction strength

 

ADRENAL CORTEX (outer three layers of the adrenal gland)

 

MINERALOCORTICOIDS

Secreted by the outermost region of the adrenal cortex

Principal hormone from this group - Aldosterone 

Major influence is the kidney – regulates: 

  • Salt (sodium)/potassium

  • Water balance in the body

Thus – fluid balance within the:

  • Bloodstream

  • Cells

  • Interstitial fluids

Two basic functions:

  • Retains sodium

  • Elimination of potassium

  • (Salt & water balance)

It’s the blood potassium level that regulates the amount of aldosterone produced by the adrenal cortex.

When this level rises – more aldosterone is secreted

When it’s lowered – opposite effect

 

GLUCOCORTICOIDS

Secreted by the middle region of the adrenal cortex

Raises the levels of blood sugar (glucose).

Principal one CORTISOL - helps the body respond to stress by promoting the release of energy 

Does this by:

Controlling the metabolism of:

  • Fats, proteins, carbohydrates which then maintain blood glucose

AND 

  • To keep that balance in stressful situations

Effect:

  • Raises blood sugar levels (opposite to insulin)

  • Converts breakdown of protein to carbohydrate 

THIS NEEDS ENERGY

STRESS

If the body is stressed it stimulates the adrenals to produce cortisol

The extra cortisol – seen as an increase in available glucose - makes the body more alert and allows it to cope with the stress such as: 

  • Infection

  • Trauma/fright

  • Surgery

  • Temperature extremes to high altitude

  • Emotional problems

When the stressful situation ends, adrenal hormone production returns to normal.

Too much stress is ok for a short time, but sustained high levels of cortisol will gradually have negative effect, for example:

  • Destroy healthy muscle and bone (breaks down too much protein into carbohydrate).  Examples include: weakening of bone, thinning of skin & mucus membranes

  • Slowing down the healing because of the inflammatory process

  • This slows down the connective tissue regeneration (which makes wounds slow to heal)

  • Suppress the response of tissues to injury – hence easy bruising*

  • Have a higher risk of spreading infection so increased susceptibility to infections and a weakening of the immune system

 

GONADOCORTICOIDS

  • Secreted by the innermost region

  • Manufactures a portion of sex hormones for each sex

  • Also produces male hormones in women

  • Female hormones in men

  • This keeps the dominant sex hormones in balance

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