hormone structure and action Flashcards
different types of chemical communication?
- autocrine
- neurocrine (synaptic)
- paracrine
- endocrine (hormone)
- pheromone
- allomone
effects more distant around the body as going from 1-6
what is autocrine communication?
chemical releaed from cell feeds back on cell and affects its own activity
what is paracrine communication?
chemical release into extracellular enviro around cell and affects traget cells near by
what is pheromone communication?
chemical released into external enviro outside body and affects conspecifics (members of same species)
what is neurocrine communication?
chemical released by neuron diffuses across synaptic cleft and affects post synaptic membrane
what is endocrine communication?
chemical released into bloodstream and selectively affects distant organs (hormone)
what is allomone communication?
chemical released into external enviro outside body and affects heterospecifics (members of ther species)
describe hormones?
what are they?
what do they do?
bioregulators of the endocrine system
molecules secreted by specialised endocrine cells directly into the blood
where they’re transported to selectively act on target cells
describe the transmission of endocrine signals?
- signal stimulates endocrine cell to release hormone which it has produced
- hormones travel into bloodstream circulating around whole body
- affect any target cells possessing correct receptor for the hormone
what are the 3 main types of hormones?
- protein (incl peptides which are short chain proteins)
- amine
- steroid
describe protein hormones?
structure?
examples of different functions?
chain of amino acids
e.g insulin (metabolism),
FSH (female oestrous cycle), oxytocin (social bonding and care) and releasing hormones (cause other endocrine cells to release hormones)
predominantly release from hypothalamus
describe amine hormones?
modified single amino acid (monoamine)
e.g adrenaline and melatonin (metabolism and body function)
describe the action of protein and amine hormones?
bind to receptor on outside of cell membrane
changes the shape of receptor in cell membrane
receptor releaes another chemical into cell (secondary messenger) which alter function of cell
- act rapidly
- prolonged effects
how is sensitivity to amine and protein hormones changed?
by upregulating (increasing) or downregulating (decreasing) number of receptor for hormone on cell
describe steroid hormones?
structure and examples?
- derived from cholesterol
- soluble in lipids (dissolve in fats) so able to cross cell membrane
- e.g oestrogen and stress hormones
describe the action of steroid hormones?
can pass through cell membrane as can diffuse passively across lipid bilayer which is cell membrane
bind to receptor within cell to from steroid-receptor complex
this complex travels into nucleus and binds to DNA and alters production of proteins
- act slowly
- long lasting effects via transcription
how can sensitivity to steroid hormones be changed?
presence or absence of co-factors which are necessary for cells to respond
storage of protein and amine and steroid hormones?
protein and amine - can be stored
steroid - can’t be stored so must be synthesised
describe how endocrine glads secrete hormones?
follicles of endocrine cells secrete hormones into the lumen (interior) of the cell
hormone passes into bloodstream through capillaries from cell
ductless - no ducts or channels leading to bloodstream
subdivisions of endocrine system?
- endocrine only negative feedback loop - passive response to hormone levels in blood
- neuroendocrine (connection between nervous and endocrine) as hypothalamus and pituitary gland involved - rapid hormonal response
what is meant by a negative feedback loop in controlling hormone levels?
high levels of hormone in bloodstream inhibit further production of hormone to maintain homeostasis
what are some of the key pathways in controlling hormone production?
autocrine feedback
target cell feedback
brain regulation
brain and pituitary regulation
describe autocrine feedback to control hormone production?
and example?
endocrine cells produce hormone and feedbacks on itself when too much to inhibit secretion
e.g prostaglandins which suppresses production of HCl in stomach and inhibits itself when too much
describe target cell feedback to control hormone production?
negative feedback occurs due to biological response of target cell
e.g insulin pathway where secretion halted when blood glucose level decreases due to muscle uptake instructed by insulin
describe brain regulation pathway to control hormone production?
hypothalamus stimulates endocrine cells through neural or hormonal communication
biological repsonse due to bidning with target cells feeds back to hypothalamus
e.g alarm response when adrenaline no longer needed as threat has passed
describe brain and pituitary regulation to control hormone production?
hypothalamus stimulates pituitary gland to release tropic hormone which stimulates production of hormone from endocrine cell
negative feedback from biological response received by both hypothalamus and pituitary gland
e.g temperature homeostasis
difference between anterior and posterior pituitary?
anterior - synthesises and secretes hormones
posterior - stores and secretes hormones only DOESN’T SYNTHESISE
describe the milk letdown reflex as a short term effect of a hormone?
receptors sense sucking
nerve impulses stimulate hypothalamus
stimulates posterior pituitary via oxytocin neuron to release oxytocin
stimulates mammary glands to contract and release milk
baby stimulated to suck more so even more stimulation (therefore positive feedback loop)
production stops when stimulation (sucking/crying) stops
describe growth hormone as a long term effect of a hormone?
external factors affecting this and their effects?
hypothalamus releases somatocrinin (releasing hormone)
triggers anterior pituitary to release growth hormone which in turn influences bone growth
more sleep = more somatocrinin = more bone growth
high stress, vigorous exercise, starvation = inhibiting somatocrinin = retarded bone growth
but can be reversed if adverse situation removed
