T1 L1 endocrinology intro Flashcards
comparison of NS and endocrine
NS:
- cells release chems and grow towards them
- v rapid focussed, precise comms between individual cells
Endocrine:
- chem messenger in blood
- slow sustained comms between group of cells
endocrine system definition
- series of ductless glands
- secrete chem messengers -> blood
hormone definition
- chem messenger, act on cell w/ appropriate hormone receptors
- each hormone can act ons everal target tissues
Pituitary gland location
below brain in skull
- sits in small bony cavity SELLA TURCICA
pituitary gland
Anterior pituitary gland:
hypothalamus -> hypothalamico- hypophyseal portal vessels in infundibulim -> APG
Posterior pituitary gland
neurosecretory cells in hypothalamus -> hypothalamico-hypophyseal tract in infundibulum -> PPG
thyroid and parathyroid gland location and function
- neck
- control of metabolic rate
- calcium homeostasis
pancreas
digestive enzymes directly into GIT
- insulin into blood (bgl & glucose utilisation)
Adrenal glands
- on top of kidneys
- outer cortex: stress, Na+, glucose homeostasis
- inner medulla: Stress response
gonads: ovaries/ testes
reproductive hormones
- development of secondary characteristics & reproduction
effect of hormone produced by
- hormone interaction w/ receptor: (intracellular / membrane bound)
Types of hormone receptors
- steroid hormone receptors
- G-protein coupled receptors
- Tyrosine kinase receptors
mechanism of steroid receptor hormone
- steroid hormone crosses cell membrane and binds to a receptor ( cytoplasmic or intracellular)
- H-R complex binds to a hormone response element of DNA to influence GENE TRANSCRIPTION
mechanism of G protein coupled receptor hormone
- GPCR hormone binds to 7 TM r to cause SYNTHESIS OF SECONDARY MESSENGER (inositol triphosphate/ cAMP)
- 2ndary messenger phosphorylates intracellular regulatory protein
- Influences cellular activity (smooth muscle contraction)
mechanism of Tyrosine Kinase Receptor Hormone
- hormone binds to membrane bound enzyme (dimerised receptors present for hormone action)
- Receptor acts as an enzyme to phosphorylate tyrosine components of intracellular regulatory proteins
2 classes of hormones:
- peptide hormones
2. steroid hormones (& thyroid hormones)
peptide hormones characteristics
- peptide: chain of a.acids
- highly h2o soluble (unable to cross cell membrane w/o carrier protein)
- susceptible to protease attack
- acts on membrane bound receptors
- not orally active
- rapid onset of action
- short plasma 1/2 life
- short duration of action
steroid & thyroid hormone characteristics
-highly lipid soluble (able to cross lipid membrane and act on intracellular receptors)
-POOR H2o soluble
-transported blood bound to plasma protein
-only unbound hormone is biologically active
-slow onset of action
-long plasma half life
-long duration of action
-
hypothalamus stimulates Ant. PG
hypothalamus secretes stimulating (or trophic) hormones (4)
- Thyrotrophin releasing hormone (TRH)
- corticotrophin releasing hormone (CRH)
- Gonadotrophin releasing hormone (GRH)
- Growth hormone releasing hormone (GHRH)
Ant. PG releases TSH
acts on ____
stimukates secretion of ____
- TSH -(via TRH stim from hypothalamus)
- thyroid
- thyroxine
Ant. PG releases ACTH
acts on ____
stimukates secretion of ____
- ACTH (via corticotropin releasing hormone from hypothalamus)
- adrenal cortex
- cortisol
Ant. PG releases FSH
acts on ____
stimukates secretion of ____
- follicle stimulating hormone (via GnRH from hypothalamus)
- ovary
- progesterone
hormonal secretion controlled by -ve feedback
- thyroid hormone decreases secretion of TRH & TSH
- cortisol decreases secretion of CRH & ACTH
- Oestrogen decreases secretion of GnRH & FSH
common consequence of -ve feedback
cyclical variation in hormone conc
