Endocrine System Flashcards
What is a hormone?
A chemical substance synthesised by a specific tissue + secreted into bloodstream, whereby it is carried to a non-adjacent sites in body + exert its actions
What is a neurotransmitter?
A chemical substance synthesised by neuron + secreted directly on to adjacent neurons or tissues, whereby it exerts its actions
What are endocrine glands?
Secrete hormones into bloodstream
What are target cells?
Have receptors for given hormones so can later activities in response to hormone
What is the HPA axis + cortisol activated by?
Stress (physical + mental)
Describe HPA axis
Hypothalamus nuclei -----> CRH Anterior pituitary gland -----> ACTH Adrenal cortex Cortisol released
Why is there a final hormone feedback in HPA axis?
To turn off endocrine system
Describe final hormone feedback in HPA axis
Cortisol feeds back to anterior pituitary then hypothalamus nuclei
What does cortisol do?
Increase + maintain glucose levels Increase gluconeogenesis Decrease glucose uptake Decrease protein synthesis Regulate brain function Immune response/inflammation
Why does cortisol decrease protein synthesis?
Amino acids available for gluconeogenesis
What is the disorder associated with cortisol?
Cushing’s syndrome
What is Cushing’s syndrome?
Hypercortisolaemia = too high cortisol
Describe regulation of blood glucose by insulin
Beta cells in pancreas Glucose undergoes glycolysis = increase ATP ATP acts on K+ channel = closes it = depolarisation of beta cell = Ca2+ channels open = Ca2+ enter cell Release of insulin
Describe hypothalamic - pituitary - ovarian axis/tract
Hypothalamus ----> GRH Pituitary ----> FSH & LH Ovaries Ovulation Oestrogen + progesterone released
What is GRH?
Gonadotrophin releasing hormone
What is FSH?
Follicle stimulating hormone
What is LH?
Luteinising hormone
What does oestrogen do?
Sensitises LH releasing cells in pituitary
Proliferation of endometrium
Inhibits FSH = regulates cycle
What do progesterone do?
Render endometrium = suitable for implanting of fertilised egg + maintaining endometrium
Inhibits further release of GRH, FSH + LH = regulate cycle + ovulation
What are the two options after ovulation?
Fertilisation
OR
No fertilisation
Describe what happens if there is fertilisation
Ovum secrets human chorionic gonadotrophin = stimulates corpus luteum to continue secreting progesterone
= maintains endometrium + pregnancy
= inhibits further secretion of GRH, LH + FSH = prevents further follicles developing
Describe what happens if there is no fertilisation
Corpus luteum regresses, progesterone levels drop
Endometrium cannot be maintained = menstruation
Lack of progesterone = clamp on GRH, FSH + LH released = cycle starts again
What are the causes of Cushing’s syndrome?
Adrenal or pituitary tumour
Side effect of chronic glucocorticoid therapy
Metabolic side effects - eg. increased abdominal fat
What type of hormone is cortisol?
Metabolic
What are some side effects of Cushing’s syndrome?
Buffalo hump Moon face Thinning of skin Depression Diabetes
What is the treatment for Cushing’s syndrome?
Removal of tumour
Inhibition of cortisol synthesis by metyrapone
Describe the treatment of Cushing’s syndrome with metyrapone?
11β -hydroxylating enzyme can be blocked by metyrapone
= decreases amount of cortisol available for secretion
Why is cortisol important?
At high levels = inhibit inflammation + immune response
What disorders associated with insulin?
Diabetes mellitus
Insulin hyposecretion
Insulin receptor hyposensitivity
Describe type 1 diabetes
Loss of β cell
Substitute with insulin
What background intermediate acting insulin is used in type 1?
Isophone insulin
What short term fast acting insulin is used in type 1?
Soluble insulin before meal
Describe type 2 diabetes
Non-insulin dependant
Desensitization of pancreas or β cells
Introduce K+ blocker (act similar to ATP)
What is cause of type 2?
Metabolic demands of obesity
What do oral contraceptives do?
Target negative feedback = clamp secretion of GRH, FSH + LH
What do oral contraceptives supply?
Exogenous oestrogen + progesterone
= mimic pregnant state
What is the combined pill?
Oestrogen + progesterone
What does the combined pill do?
Oestrogen
Oestrogen inhibits secretion of FSH via negative feedback = prevents development of ovarian follicle
What does the combined pill do?
Progesterone
Progesterone inhibits secretion of LH = prevents ovulation + males cervical mucus less suitable for passage of sperm
What is the mini pill?
Progesterone
Why is mini pill mainly effective?
Effect on cervical mucus
DOES NOT block ovulation
What are the main hormone-producing glands?
Hypothalamus Pituitary Parathyroid Pancreas Thyroid Adrenal gland Pineal gland Ovaries Testes
What does the hypothalamus control?
Body temp, hunger, mood + release of hormones from other glands
What does the pituitary control?
Other glands + make hormones that trigger growth
What does the parathyroid control?
Ca2+ in body
What does the pancreas control?
Insulin
What does the thyroid control?
Hormones associated with calorie burning + HR
What does the adrenal gland control?
Cortisol
What does the pineal gland control?
Melatonin
What does the ovaries control?
Oestrogen, testosterone + progesterone
What does the testes control?
Testosterone
