Endocrine System - Adrenal Gland Flashcards
List the main hormones produced by the adrenal gland and their functions
Cortisol - Regulates metabolism, immune and stress response.
Aldosterone - Regulates electrolyte balance, particularly sodium and potassium.
Epinephrine - Acts as a neurotransmitter and hormone involved in the body’s “fight or flight” response.
Norepinephrine - Acts as both a neurotransmitter and hormone, works with epinephrine to regulate the body’s response to stress by increasing heart rate, constricting blood vessels, and increasing blood pressure.
DHEA (Dehydroepiandrosterone) - Acts as a precursor hormone, plays a role in the development of secondary sexual characteristics.
Describe the hypothalamic-pituitary-adrenal axis and its role in control of glucocorticoid secretion.
In response to stress or other stimuli, the hypothalamus secretes corticotropin-releasing hormone.
CRH travels through the bloodstream to the anterior pituitary gland, where it stimulates the release of adrenocorticotropic hormone (ACTH).
ACTH is a peptide hormone that stimulates the adrenal glands to produce and release glucocorticoid hormones, primarily cortisol.
Once cortisol levels rise in response to stress, they exert negative feedback on the hypothalamus and pituitary gland to regulate the HPA axis.
Elevated cortisol levels inhibit the release of CRH from the hypothalamus and ACTH from the pituitary gland, thereby reducing further secretion of cortisol
List the main actions of glucocorticoids
Metabolism regulation - promoting gluconeogenesis
Anti-inflammatory and immunosuppressive effects:
Stress response - help prepare the body to cope with stress by mobilizing energy reserves
Regulation of cardiovascular function - increasing the sensitivity of blood vessels to vasoconstrictors, such as catecholamines.
Explain the significance of cortisol during major physical stress
Its actions help ensure adequate energy supply, modulate the inflammatory response, support tissue repair and recovery, and facilitate the body’s overall ability to cope with and recover from physical stress
Describe the mineralocorticoid effects of aldosterone in terms of its renal actions
Aldosterone is a steroid hormone produced by the adrenal cortex, specifically in the z. glomerulosa region. It acts as a mineralocorticoid so regulates electrolyte balance, particularly sodium and potassium, in the body. Aldosterone exerts its effects in the kidneys, where it helps maintain proper electrolyte levels through several renal actions;
stimulates the reabsorption of sodium ions (Na⁺) from the renal tubules back into the bloodstream (DCT)
enhances the secretion of potassium ions (K⁺) into the urine
indirectly stimulates the secretion of hydrogen ions (H⁺) into the urine (regulates blood pH)
Indirectly reabsorbs water
Describe the effects of excess cortisol secretion.
Known as Cushing’s syndrome.
Metabolic effects - increased gluconeogenesis, redistribution of fat and insulin resistance.
Immunosuppression
Hypertension: Excess cortisol can lead to increased blood pressure by promoting sodium retention and vasoconstriction
Osteoporosis and muscle weakness
Describe the effects of deficient cortisol.
Addison’s disease.
Adrenal insufficiency;
hypotension - decreased sodium retention and volume depletion
Reduced aldosterone secretion in primary adrenal insufficiency can lead to electrolyte imbalances such as hyponatremia - low sodium levels
hyperkalemia - high potassium levels
Fatigue and gastrointestinal symptoms.
Describe the effects of excess aldosterone.
Primary Aldosteronism
Excess aldosterone leads to Na+ retention and K+ excretion = volume expansion and hypertension.
Hypokalaemia - excess K+ excretion
Excess aldosterone promotes H+ secretion in exchange for K+, leading to metabolic alkalosis (low blood pH)
Describe the effects of reduced aldosterone secretion.
Hyperkalemia - reduced aldosterone secretion leads to impaired K+ excretion by the kidneys, resulting in elevated potassium levels
Hyponatremia -
Decreased sodium reabsorption by the kidneys can lead to low sodium levels
Deficient aldosterone secretion leads to decreased sodium retention and volume depletion, resulting in hypotension and orthostatic symptoms
Describe the main effects of normal catecholamine secretion.
- Stress response - prepare body for action by increasing heart rate, dilating airways, and mobilising energy reserves.
- CNS effects - Dopamine modulates mood and reward pathways in the brain. Norepinephrine and epinephrine act as neurotransmitters in the central nervous system.
- Metabolic effects - stimulate glycogenolysis (breakdown of glycogen into glucose) in the liver and skeletal muscles, increasing blood glucose levels to provide energy for cellular metabolism. Also promote lipolysis.
Describe the main effects of excess catecholamine secretion.
Hypertension - due to increased systemic vascular resistance and cardiac output.
Tachycardia and palpitations - caused by excessive stimulation of beta-adrenergic receptors by epinephrine and norepinephrine.
Hypermetabolism
Glycogenolysis and hyperglycemia
Anxiety and nervousness.
What are catecholamines?
Catecholamines are a group of neurotransmitters and hormones that include dopamine, norepinephrine and epinephrine.
Synthesised in the adrenal medulla
Crucial roles in the body’s response to stress, regulation of cardiovascular function, and modulation of the autonomic nervous system
