Endocrine system 3 Flashcards
Where is parathyroid hormone (PTH) secreted from?
The parathyroid glands
What are the parathyroid glands?
Four small glands located on the posterior surface of the thyroid gland
What is the role of parathyroid hormone (PTH)?
Acts to increase plasma Ca2+ levels, opposing effects of calcitonin
What is the role of calcitonin?
Produced by parafollicular “C” cells, acts to reduce plasma Ca2+ levels
What are the 2 types of hormones produced by the adrenal gland?
- Catecholamines
- Andrenal steriod hormones
Where are the adrenal glands located?
On top of the kidneys
Where in the adrenal gland are catecholamines produced?
In the medulla (inner part)
Where in the adrenal gland are adrenal steriod hormones produced?
In the cortex (outer layer)
What are they types of catecholamines?
- Adrenaline
- Noradrenaline
What are the types of adrenal steroid hormones?
- Mineralocorticoids (aldosterone)
- Glucocorticoids (cortisol)
- Weak androgens (DHEA(S)) –> dehydroepiandrosterone
What is the role of mineralocorticoids?
Involved in electrolye balance
What is the role of glucocorticoids?
Involved in plasma glucose levels
What are androgens?
Testosterone (but weak version)
What sort of cells does the adrenal medulla contain?
Chromaffin cells - these are neuroendocrine cells
What synapses with the adrenal medulla chromafin cells?
The preganglionic sympathetic neurone
Causes catecholamines to be released into the bloodstream when signal is sent
When are catecholamines released?
- During fight or flight
- Acute stress
- Hard exercise
What are the 3 zones in the adrenal cortex?
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Where are the mineralocorticooids released from?
Zone glomerulosa - in the adrenal cortex
What happens in the adrenal cortex?
- Aldosterone is the main mineralocorticoid produced
- Regulated Na+ and K+ balance
- Part of the renin-angiosten-aldosterone system
What is the main thing released from each zone in the adrenal cortex?
- Zona glomerulosa = where mineralcorticoids are released (e.g. aldosterone)
- Zona fasciculata = where mostly glucocorticoids are released (e.g. cortisol)
- Zona reticularis = mainly weak androgens
What happens in the zona fasciculata?
- Main glucocorticoid produced is glucose
- Adaption to stress
- Regulates glucose metabolism, also protein & fat
What happens in the zona reticularis?
- Weak androgens = incl dehydroepiandrosterone (DHEA), DHEAS & androstenedione
- 50% in women (auxiliary/pubic hair growth & libido
- Negligible contribution in men
Which hormones from the adrenal glands conribute to -ive feedback?
Aldosterone & androgens do not contribute to -ive feedback, only cotisol
What sort of hormone is cortisol?
Glucocorticoid & mineralocorticoid
What is the release of cortisol stimulated by?
Acute stress
What effect does cortisol have on the brain?
- Release of cortisol stimulated by acture stress
- Higher centres in the brain are activated in the brain during this
- Cortisol is controlled byt the SCN
- This is controlled by the SCN (Suprachiasmatic nucleus) - this is a cluster of neurones that control endogenous circadian rhythms
What is the role of the suprachiasmatic nucleus (SCN)?
Controls endogenous circadian rhythms
What is the typical dinural variation of plamsa cortisol?
Peak early in the morning, trough in the late evening
Associated w sleep wake cycle
Where is the pancreas located?
Sits close to the small intestine & behind the stomach
What is the exocrine role of the pancreas?
Digestive enzymes - to further break down carbs, proteins & lipids in the chyme
What is the endocrine role of the pancreas?
Islets of langerhans (glucose homeostasis)
What are the islets of langerhans?
- Endocrine cells in clusters, scattered throughout the pancreas
- Around only 1-2% of the total pancreatic mass but recieve 10% of blood supply
What are the Islet cell types?
- A or α
- B or β
- D or δ
- PP
- Epsilon or ε
Name what each of these islet cell types do:
- A or α
- B or β
- D or δ
- PP
- Epsilon or ε
- A or α = glucagon (30-40% of total human islet cells)
- B or β = insulin (50-60%)
- D or δ = somatostantin (5-10%)
- PP = pancreatic polypeptide (1-5%)
- Epsilon or ε = ghrelin (<1%)
Where is insluin synthesised?
β cells
What sort of hormone is insulin?
Peptide hormone
What are the roles of insulin?
- Main physiological regulator in blood glucose levels
- Promote growth & development
- Promote cellular uptake of K+ via Na+/K+-ATPase pump
- Promote uptake & utilisation of glucose in skeletal muscles & adipose
- Promote fuel storage (ANABOLIC)
How does insulin promote fuel storage?
Inc rate of synthesis & storage of energy reserves (glycogen & fats) and of protein
What is the insulin action of reducing blood glucose mediatd by?
Mediated by insulin receptor
(Tyrosine kinase receptor family)
Go over slide 20, need to see what it means
hfoiwe
Where is glucagon synthesised?
In α-cells
What sort of hormone is glucagon?
A peptide hormone
What is glucagon stimulated by?
Low blood glucose
How do glucagon and insulin’s actions differ?
They are opposit of each other
What is the main purpose of glucagon?
Raise blood glucose
What are the actions of glucagon?
- Stimulate hepatic glycogenolysis
- Simulate hepatic gluconeogenesis
- Stimulate lipolysis
What is the main male hormone?
Testosterone (found in the testes) - main androgen
What are the main female hormones?
- Oestradiol - main oestrogen
- Progesterone
What is the main hormones involved during pregnancy (placenta)?
Oestrogens & progesterone
What are the 3 names for different ways that hormones can interact with each other?
(Intergrated endocrine physiology)
- Synergistic
- Permissive
- Antagonistic
What is synergistic hormone interaction?
Produce much greater enhanced response than sum of the effects of individual hormones
e.g. THs & catecholamines/SNS on metabolism , CVS etc
Glucagon & adrenaline on elevating blood glucose
What is permissive hormone interaction?
Presence of one hormone allows the second hormone to act
e.g. THs on GH activity in growth promotion
Prolactin (milk production) to allow oxytocin action (milk-let down)
What is antagonistic hormone interaction?
Effects of hormones oppose each other
e.g. PTH increases blood Ca2+ –> calcitonin dec blood Ca2+
Insulin dec blood glucose –> glucagon, cortisol, GH & adrenaline inc blood glucose
Refer to slide 24 for a graph example of synergism
Effect of hormone infusions on blood glucose levels
What is hte ideal blood glucose level?
4-8mmol/L
What are the mechanisms to increase blood glucose?
Glucagon –> adrenaline, growth hormone cortisol –> glucose production via glycogenolysis & gluconeogenesis
What are the mechanisms to decrease blood glucose?
Insulin –> glucose utlisation –> glucose uptake and use
