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Endocrinology yr2 > hypothalamic pituitary gland system > Flashcards

hypothalamic pituitary gland system Flashcards

1
Q

what is the hypothalamic pituitary system

A

coordinates the endocrine system

organises hormonal responses to stimuli from higher brain centres

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2
Q

what does the hypothalamic pituitary system respond to

A

external environment changes
- temp, food, stressors
internal environment
- hormones, feedback signals, salt balance, BP, heart rate, pregnancy, trauma, disase

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3
Q

what is the pitiutary gland

A

also called hypophysis
sits in a bony cavity called sella turnica
2 distinct lobes with reoles

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4
Q

what is the anterior pituitary gland

A

adrenohypophysis
well vascularised glandular tissue
contailss 5 types of secretory ceclls
NO nerve fibres

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5
Q

what is the posterior pituitary

A

brain-like tissue

secretes 3 principle neuro-hormones

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6
Q

what are the 5 secretory cells in the ant-pit

A 
acidophiles
- somatrophs
- mannotrophs/lactotrophs
basohils
- gonadaotrophs
- thyrotrophs
- corticotrophs
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7
Q

examples of single polypeptide hormones

A

ATCH
GH
PRL

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8
Q

examples of multi-subunit polypeptide chain hormones

A

LH
FSH
TSH

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9
Q

what is a multi-subunit polypeptide chain hormone

A

common alpha subunit

but different beta subunits that give the hormones their biological specificity

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10
Q

what is the hypothalamus

A

regulatory centre

recieved nerve fibres from other areas of the brain and sends signal down to pituitary

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11
Q

what type of neurones innervate the pos pit from the hypothalamus

A

magnocellular peptidogeric neurones

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12
Q

what type of neruones innervate the ant.pit from the hypothalamus

A

hypothalamic parvocellular peptidergic neurones

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13
Q

what is a petidergic neurone

A

make a chemical messernger which is a peptide

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14
Q

what do hypothalamic parvocellular neurones do

A

terminate by the median eminence stimulating hormones in a pulsatile way

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15
Q

describe the hypophseal portal system of the ant-pit

A

neurones from hypothalamus release peptide near the median eminence
hypophyseal arteries form a capillary plexus to the portal vein which takes the peptides to the ant-pit
the peptides reach the second plexus
peptide act as ligands on ant-pit cells using GPCRs
2nd messengers made- TRH, GnRH, GHRH ( releasin hormone RH)

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16
Q

describe the anatomy of the pos pit

A

magnocellular neurones from the hypothalamus send axons down and directly terminate in the pos pit

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17
Q

key difference between pos and ant pit

A

pos has direct neuronal innervation

ant doesnt, uses circulation system

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18
Q

parvocellular hypothalamic neurones

A

ant-pit
control the 5 secretory cell types
each neurone produces a neuropeptide to act on receptors of each cell type

19
Q

what are the hypothalamic releasing hormones

A 
TRH
thryotrophin RH
GnRH
gonadotrophin RH
CRH
cortiocotrophin RH
GHRH
Growth hromone RH
20
Q

what is the HPA axis

A

hypothalamic-pituitary axis
eg. cortisol production controls its own secretion, elevated levels can act to inhibit both the pituitary and hyothalamus fro releasing CRH and ATCH

21
Q

what is pan-hypopituitaryism

A

disease
loss of multiple endocrine cells in pit
deficient in hormones

22
Q

what can pan-hypopiuitaryism be caused by

A

a space occupying non-functional tumour

23
Q

how is pan-hypopitiutaryism treated

A

with steriods to replace what the target gland would make in response to the lost pit hormones
eg gonadalstreiods

24
Q

what are the main hormones of the pos pit

A

oxytocin and vasopressin

25
Q

features of magnocellular neurones

A

send axons down to pit and directly innervate the pos pit

takes up precurosr peptide hormones and makes pre-prohormones which are then released

26
Q

how are neurohormones released

A

action potential arrives
wave of depolarisation
influx of NA ions
calcium channels opens
drives exocytosis of granules containing oxytocin or vasopressin
membrane repaptures the granule and everything is restored back to normal

27
Q

whats the role of oxytocin

A

promotes childbirth/partuition and the milk ejection reflex

28
Q

whats the role of vasopressin

A

reduced water excretion by the kidney

29
Q

what is an analogue

A

a synthetic version of the hormone used clincially

eg. oxytocin analogues used to promote childbirth

30
Q

stimulus for vasopressin

A

increased osmotic pressure in blood, picked up by osmoreceptors
fall in blood volume detected by baroreceptors

31
Q

actions of vasopressin

A

allows more aquaporins on nephron, more permeable to water

restore the blood volume to correct level, more water resorbed

32
Q

describe the process of ADH secretion

A
  • high blood osmoticpressure stimulates hypothalamic neurones
  • osmoreceptors active neurosecretory cells to syntheise ADH in hypothalamus
  • nerve impluses allow ADH to be reelased in pos pit blood stream
  • ADH goes and has effects on target tissues
    low blood osmolarity inhibits all this acitivty reducing ADH secretion
33
Q

disorders of vasopressin

A 
hypersecretion
= tooo much fluid retention, decreases osmolarity
patients need to limit fluid intake
hyposecretion
= too little ADH
diabetes insipidus
34
Q

what is the neuroendocrine reflex

A

oxytocin
sensory cells in nipple convey stimulus to brain via mechanoreceptors
synpases contact mangocellular neurones and oxytocin is made
the hormone reaces the myo-epithelial cells leading to muscle contraction, pressure and he milk is ejected

35
Q

role of the mammory gland

A

globular gland structure
epithelial cells make the milk
a reticular netrowrk and corrdianted activity with cells allow the mypepithelila cells to respond to oxytocin and rlease the milk

36
Q

whats stimulates milk production

A

prolactin

37
Q

what stimulates milk release

A

oxytocin

38
Q

what is the pregnant rat model

A

nipple transducers measured hormone levels
there was a burst of activity as the pups attach
the intramammory pressure also increased just after the hormone burst

39
Q

how does the milk ejection relfex work

A

positive feedback, more nipple stimulates equals more oxytocin and more milk

40
Q

furguson reflex

A

tactile stimulation of the reproductive tract leads to oxytocin release
shwon in sheeo and orfan lambs

41
Q

describe the oxytocin pathway

A

nipple stimuli sensed by mechanoreceptors
this is sent as a neuronal imput to the hypothalamus
which releses down axons into pos pit oxytocin
oxytocin rleased into blood stream and this targets myoepithelila cells of breast tissue
milk ejected

42
Q

what kind of receptor does oxytocin use

A

GPRC

43
Q

how is positive feedback used in oxytocin

A

the foetus drops lower into the uterus leading to cervial stretch
this positively leads to oxytocin release and uterine contractions
the loop stops when the uterus is not stretched any more and the foetus is delivered

Endocrinology yr2 (9 decks)

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