Unit 3 - Hormones Flashcards
what are classical glands?
glands whose primary function is endocrine
- e.g. pituitary, adrenal, pancreas, placenta
what are non-classical glands?
glands whose primary function is not endocrine
- e.g. kidneys, brain, heart, GI tract
what is the difference between paracrine, autocrine and juxtacrine?
paracrine - neighbouring cells
autocrine - same cell
juxtacrine - cells in close contact
name three steroid hormones
cortisol, oestrogen, testosterone
name three peptide hormones
growth hormone, oxytocin, parathyroid hormone
name two amino acid derivative hormones
thyroid hormones (derived from ionated tyrosine residues), catecholamines (derived from tyrosine)
describe the properties of steroid hormones
- cholesterol derivatives
- receptors are in nucleus or cytosol
- bind DNA/ transcription
- slow effect
- more permanent
describe the properties of peptide hormones
- bind 2nd messengers
- receptors are on cell surface
- rapid effect
- temporary
what is the basic pathway for endocrine feedback?
hypothalamus releasing hormone anterior pituitary tropic hormone endocrine gland hormone
where will negative feedback occur in basic pathway?
- hormone can inhibit the anterior pituitary and hypothalamus
- tropic hormone can inhibit the hypothalamus
where is the pituitary gland located?
inferior to hypothalamus with optic chiasm inbetween
lies in depression of sphenoid bone (sella turcica)
describe the structure of the gland
anterior/ intermediate/ posterior lobe
infundibular sterm has pars tuberalis wrapped around it forming the pituitary stalk
how is the anterior lobe connected to the hypothalamus?
hypothalamus - hypophyseal portal system originating in primary capillary plexus - long portal vessels travel down pituitary stalk to anterior lobe
how is the posterior lobe connected to the hypothalamus?
connected by nerves which originate in hypothalamus (supra-orbital nucleus/ paraventricular nucleus) -travel in axons to posterior lobe
which hormones are secreted by the posterior lobe and where are they stored beforehand?
vasopressin/ oxytocin
stored in axon terminals or Herring bodies (along with neurophysins -proteins)
explain the role of oxytocin for lactation
child sucking on mothers breast stimulates hypothalamus - supraoptic nucleus - increased nerve impulses
- release of oxytocin from posterior lobe
- has effect on target cells via GPCR causes increase in intracellular calcium in myoepithelial cells which activates contractile machinery to cause milk ejection
what is another role of oxytocin?
uterine spasmogen (causes contractions)
explain the role of vasopressin in kindyes
regulates urine osmolality and plasma osmolarity by kidney reabsorption
dehydration (increased plasma osmolarity) - detected by osmoreceptor in hypothalamus - release of ADH from posterior lobe (initiated by paraventricular nucleus) - acts on target cell via GPCR
- stimulates water reabsorption from final 1/3 of distal tubule and collecting ducts of kidneys (into plasma)
- urine volume decreases and is more concentrated = urine osmolality increases and plasma osmolarity decreases
what type of reflex do the hormones of posterior lobe of pituitary gland produce?
neuroendocrine reflex
what are the six hormones produced by the anterior pituitary gland and which cell type?
gonadotrophs = LH/ FSH corticotrophs = ACTH thyrotrophs = TSH lactotrophs= prolactin somatotrophs = growth hormone
which hormones are tropic and non-tropic?
tropic: FSH/ LH/ ACTH/ TSH (FLAT)
non-tropic: prolactin/ growth hormone
what endocrine glands do the tropic hormones have an effect on?
ovaries/testes - FSH/ LH
adrenal glands - ACTH
thyroids - TSH
what is the principle target of non-tropic hormones?
mammary glands - prolactin
bones/ skeletal muscle/ liver - growth hormone
what are the four stimulating releasing hormones?
GHRH for growth hormone
GnRH for FSH/ LSH
CRH for ACTH
TRH for TSH
what are the two inhibitory releasing hormones?
DA (dopamine) for prolactin
SS (somatostatin) for growth hormone
what other hormones have an effect on extent of growth?
stimulate growth - excess insulin
inhibit growth - excess cortisol/ lack of thyroxine
what are the stimulants of growth hormone?
stress/ exercise/ fasting/ sleep/ sex hormones/ amino acids/ hypoglycaemia
how does growth hormone affect skeletal muscle?
decreases glucose uptake
increases amino acid uptake - more protein synthesis
no protein breakdown - increase muscle mass
how does growth hormone affect adipose tissue?
decreases glucose uptake
increases lipolysis - so decreased fat deposits
how does growth hormone affect liver?
direct effect: increase gluconeogenesis and protein synthesis: stimulate IGF production (insulin-liek growth factor)
what are the effects of IGF-1, -2 on growth?
skeletal growth = cartilage formation/ bone deposition
soft tissue growth = protein synthesis/ cell proliferation
what is somatopause?
rapid decline in growth hormone as age increases
what are the effects of somatopause?
increased body fat
sleep disturbance
decreased lean body mass
why do growth hormone disorders occur?
due to pituitary tumours secreting GH
name and describe two disorders that occur due to excess GH
gigantism - abnormal growth before epiphyseal growth plate fuse - normal body proportions (EXCESS IGF)
acromegaly - abnormal growth after epiphyseal growth plate fuse - disproprtionate body proportions (ie. enlarged hands/feet, tongue, lips, heart)
name a disorder that occur due to insufficient GH
pituitary dwarfism - slow growth rate - poor muscle development and excess subcutaneous fat
