Endocrine system 2 Flashcards
Where is parathyroid hormone (PTH) secreted from and what does it do?
Parathyroid hormone is secreted from the parathyroid glands located on the posterior surface of the thyroid gland
PTH acts to increase plasma Ca2+ levels, opposing the effects of calcitonin - antagonistic hormone action
Where is calcitonin produced and what does it do? (2)
Produced by parafollicular C cells
Acts to reduce plasma Ca2+ levels
Where is the adrenal gland located?
On top of each kidney, the right is slightly lower due to the liver
What does the adrenal gland produce? (3)
Adrenaline - catecholamine
Noradrenaline - catecholamine
Dopamine - small amount
What are 3 adrenal steroid hormones?
Mineralocorticoids (aldosterone) Glucocorticoids (cortisol) Weak androgens (DHEA)
What cells are in the adrenal medulla and what’s produced in the adrenal medulla?
Chromaffin cells - modified postganglionic sympathetic neurone (axonless)
Adrenaline and noradrenaline (boosts immune system)
What are the 3 zones of the adrenal cortex?
(Capsule encompassing organ) Zona glomerulosa Zona Fasciculata Zona Reticularis (Medulla (chromaffin cells))
What is the main mineralocorticoid in the zona glomerulosa and what does it do (2)?
Aldosterone
Regulates Na+ and K+ balance
Part of the renin-angiotensin-aldosterone system
What is the main mineralocorticoid in the zona fasciculata and what does it do (2)?
Cortisol
Adaptation to stress
Regulates glucose metabolism, also protein and fat
What is the main mineralocorticoid in the zona reticularis and what does it do?
Mainly weak androgens (DHEA)
Testosterone - 99% male, 50% female
Which hormone gives negative feedback?
Cortisol
Describe the stages in the hypothalamus-pituitary-adrenal axis: (7)
Hypothalamus Corticotropin-Releasing Hormone (CRH) Anterior pituitary Adrenocorticotropic hormone (ACTH) Adrenal cortex Cortisol (exogenous glucocorticoids) - feedback Target cell response
Explain a typical diurnal variation of plasma cortisol?
Cortisol peaks in the early morning and declines until we sleep - sleep wake cycle
What are the pancreas’ exocrine and endocrine functions?
Exocrine - digestive enzymes to break down carbs, proteins and lipids in the chyme
Endocrine - islet of Langerhans
Where is the pancreas located?
Close to the large intestine, under the liver, behind the stomach
What are the islets of Langerhans? (2)
Endocrine cells in clusters scattered throughout the pancreas
Small but require large blood supply
What do islets of Langerhans look like under a microscope?
Paler regions in circular shape
What are islets made up of? (3)
Alpha cells - 30/40% - glucagon
Beta cells - 50/60% - insulin
Delta cells - 5/10% - somatostatin
What type of hormone is insulin, where is it made and what does it do?
Peptide hormone
Synthesized in Beta cells
Main physiological regulator in blood glucose levels
What does insulin promote (3)?
Promotes Growth and development
Promotes cellular uptake of K+
Promotes uptake and utilisation of glucose in muscles
What is the main insulin action?
Reduce blood glucose by uptaking glucose in muscle, the liver and adipose tissue via GLUT-4
Where is glucagon synthesised and why is it produced?
Glucagon is synthesised in alpha cells and is a peptide hormone
Stimulated by LOW blood glucose
What does glucagon stimulate? (3)
Hepatic glycogenolysis
Hepatic gluconeogenesis
Lipolysis
All raise blood glucose
What are Gonads? (3)
Testes - testosterone
Ovaries - progesterone
Placenta - oestrogen and progesterone
What is a synergistic hormone action provide one example?
Multiple hormones acting with other hormones to produce an enhanced response
Example: Glucagon, adrenaline, cortisol to increase blood glucose
What is a permissive hormone response and an example?
Presence of one hormone allows a second hormone to act
Example: Prolactin (milk) to allow oxytocin action (milk let down)
What is an antagonistic hormone response and an example?
Effects of hormones oppose each other
Example: Insulin and glucagon
