Anterior Pituitary Flashcards

1
Q

what does hypophysectomy cause

A

stops growth and lactation
atrophy (thyroid/adrenal cortex/gonads)
disruption to (salt and water balance, carb and protein metabolism)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

anatomy of the pituitary

A

adenohypophysis/anterior - glandular
neurohypophysis/posterior - neuronal processes in SON/PVN
intermediate lobe - forms MSH, not in adults (in animals/babies)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

posterior lobe formation

A

forebrain (diencephalon) invagination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

anterior lobe formation

A

buccal cavity outgrowth (rathke’s pouch)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

formation steps

A

1) outgrowth of tissue forms at diencephalon (FB becomes thalamus and hypothalamus)
2) outgrowths combine
3) anterior and posterior lobes begin to form (Rathke’s pouch removal)
4) posterior lobe (neural tissue) anterior lobe (non-neural tissue) sella turcica (skull) protects pituitary gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

posterior vs anterior pituitary connections

A

posterior pituitary has neural connections
anterior pituitary has no neural connections - connected to median eminence via pituitary portal system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

blood supply

A

blood passes capillary loops through long/short hypophyseal portal vessels (specific to anterior pituitary)
superior hypophyseal artery supplies ME and stalk
inferior hypophyseal artery supplies posterior lobe directly / indirectly to the anterior lobe via short portal veins
inferior and superior artery connected via trabecular artery
A and P lobes drain into venous sinuses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

2 features of the anterior pituitary

A

hypothalamic hypophysiotropic hormones (very diluted released into wider circulation)
feedback by target gland hormones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

where are hypothalamic hypophysiotropic hormones synthesised

A

in the cell body and transported to axon terminal to be stored until release in adjacent capillary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

control of hypothalamic hypophysiotropic hormone release

A

1) 1 or more neurons in neural pathway converge on 1 neurosecretory hormone
2) direct synapse on soma/dendrite of neurosecretory hormone
3) axo-axonic synapse on nerve ending of neurosecretory hormone
4) neuron releases NT into portal vessels which modifies action of neurohormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

5 cells in the anterior pituitary

A

gonadotroph cells
corticotroph cells
somatotroph cells
lactotroph cells
thyrotroph cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

tropic vs trophic

A

tropic = hormone release
trophic = stimulates growth of downstream tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

hormone release

A

TSH/LH/FSH/ACTH - tropic
GH - stimulates growth of liver hormones/somatomedians - trophic
PRL - not trophic/tropic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

episodic hormone secretion

A

not secreted at a constant rate
secreted in a pulsatile pattern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

GH secretion

A

spontaneous surges throughout the day
occurs 3-4hrs (undetectable inbetween)
GHRH and somatostatin determine GH rhythm (peak during sleep)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what causes pulsatile secretion

A

intrinsic rhythm generators in hypothalamus

17
Q

why is episodic secretion important

A

desensitisation of hormone receptors when challenged with partner hormone (maintains sensitivity of system)

18
Q

negative feedback system

A

y (circulating hormone concentration) is sensed and compared to set point
difference in feedback is sensed and produces an error signal
hormone maintained in a narrow range

19
Q

CNS negative feedback

A

specific signal e.g. stress
CRH release acts on corticotroph cells in anterior pituitary cells
ACTH release
ACTH acts on adrenal glands to release cortisol
negative feedback to hypothalamus

high glucocorticoids = CRH and ACTH low (vice versa)

20
Q

positive feedback

A

occurs when increase in a hormone’s levels leads to enhancement of its effect by stimulating further release

21
Q

oestrogen release

A

normally uses negative feedback
high oestrogen levels use positive feedback, stimulates gonadotropin release from pituitary, rapid surge of FSH and LH (needed for ovulation)

22
Q

circadian rhythm

A

endogenous oscillations across a period of ~ 24hrs
synchronised precisely 24hrs rhythm by environmental signals L/D

23
Q

anterior pituitary hormones and CR

A

GH/PRL/ACTH pulses are larger amplitude/more frequent during sleep
larger TSH peaks in morning/peak in males
CRH/TRH/GnRH show CRs

24
Q

SCN

A

suprachiasmatic nucleus
in anterior hypothalamus

retina sends daylight info to SCN via optic nerve and optic chaism (retinohypothalamic tract)

25
Q

SCN projections

A

medial hypothalamus
ARC
ME
parvocellular portion of PVN

26
Q

melatonin secretion from pineal gland

A

NA nerves from superior cervical ganglia project to pineal gland
NA release regulated by SCN controls melatonin release
melatonin synthesised and released during darkness

light onto retina inhibits output from SCN

27
Q

what controls oestrous and menstrual cycles

A

GnRH release
modulated by steroid feedback

28
Q

what are seasonal rhythms

A

supression of rhythm generators for discrete periods of the year - suppression related to changes in daylength (photoperiod)

29
Q

what characteristics does daylength affect

A

coat colour
food intake
fattening
hibernation

30
Q

seasonal changes driven by photoperiod

A

no of hours of light/darkness
driven by changes in melatonin release