posterior pituitary

Question 1

sella turcica

Answer 1

sphenoid bone of the skull- features a protective pocket for the pituitary gland

Question 2

what are the two anatomically and functionally distinct lobes of the pituitary

Answer 2

the posterior pituitary which is composed of nervous tissue

the anterior pituitary which comprises glandular epithelial tissue (endocrine)

Question 3

what happens in the posterior pituitary

Answer 3

hormones which are packaged in the cell body of a neuron are released to the vein in the posterior pituitary

Question 4

what happens after hormones which are packaged in the cell body of a neuron are released to the vein in the posterior pituitary

Answer 4

vesicles are transported down the cell and are stored in the posterior pituitary. They are then released into the blood.

Question 5

what are the two hormones of the posterior lobe of the pituitary

Answer 5

oxytocin and vasopressin. they overlap in bioactivity

Question 6

what are the other names for vasopressin

Answer 6

anti diuretic hormone ADH or AVP- arginine vasopressin

Question 7

how is secretion controlled of the two hormones of the posterior lobe of the pituitary

Answer 7

independantly controlled from neurons within paracentricuolar PVN and supraoptic nuclei SO of the hypothalamus

Question 8

what releases oxytocin and vasopressin into systemic blood

Answer 8

neuronal terminals in posterior pituiatary

Question 9

how many hormones does each cell produce from its large precursor

Answer 9

only one from its large precursor, either prepro-oxyphysin or prepro-vasopressin

Question 10

what are the roles of oxytocin

Answer 10

childbirth and breastfeeding

Question 11

process of childbirth

Answer 11

sensory, afferent signals from stretching of the cervix lead to oxytocin release which causes contraction of the uterine smooth muscle leading to delivery of the fetus

Question 12

process of breastfeeding

Answer 12

sensorym, affrent signals induced by infant sucking at the nipple lead to ocytocin release which causes smooth muscle contractions of the mammary gland to expel milk

Question 13

men and non pregnant women and oxytocin. what stimulates its release

Answer 13

orgasm or a long hug

Question 14

where is oxytocin released in men and non pregnant women and oxytocin

Answer 14

as a neurotrasmitter in parts of the brain

Question 15

what is the result in oxytocin release during bonding and sex

Answer 15

pair bonding- attatchment of couples and nurturing parental bahaviour. this is highly conserved in evolution

Question 16

what is the importance of the hypothalamus

Answer 16

-site of interaction between nervous and endocrine systems
-many interconnections with other parts of the brain
-emotions and mental stress affect endorcine function

Question 17

what feedback loop is vasopressin a part of

Answer 17

the feedback loop that controls body fluid volume and concentration

Question 18

what target cells does vasopressin have

Answer 18

kidney cells to reduce urine production (anti diuresis) and conserve water

vascular smooth muscle to cause vasoconstriction which maintains blood pressure

Question 19

what is the mechamism of action of ADH

Answer 19

increases permeability of renal collecting tubule cells in luminal membrane to water by inserting more water channels leading to more water reabsorption in kidneys and less urine will be produced (antidueresis)

Question 20

what is ADH mechanism mediated by

Answer 20

binding to specific receptors AVPR2 in cells of collecting ducts

Question 21

secretion stimuli of vasopressin

Answer 21

high osmolarity of extracellular fluids- hyperosmolarity)
low blood volume
low arterial pressure

all of which stiumlate thirst

Question 22

what sensorts detect osmolarity for vasopressin secretion

Answer 22

hypothalamic osmoreceptor neurons detect changes in extracellular fluid osmolarity.

Question 23

what happens when there is a high ECF osmolarity

Answer 23

all cells shrink due to osmotic forces which activtaes cationic channels and membrane depolarization. this includes osmoreceptor neurons which leads to SO or PVN neurons to increase in ADH secretion

Question 24

where do osmoreceptors lie

Answer 24

outside BBB

Question 25

OVLT

Answer 25

organum vasculosum of lamina terminals

Question 26

SFO

Answer 26

sunfornical organ

Question 27

what corrects ECF hyperosmolarity

Answer 27

thirst sensation plus ADH release

Question 28

where are blood volume sensors for control of ADH secretion

Answer 28

located in low pressure complaint (easily stretchable) vessels
Ex- large veins and heart atria

Question 29

what do blood volume sensors for control of ADH secretion do

Answer 29

accomodate blood volume changes and buffer arterial pressure changes

Question 30

what are blood volume sensors for control of ADH secretion made of

Answer 30

sensory nerve endings- baroreceptors- detect the amount of stretch and signal SON and PVN neurons. Decreased stretch causes in increased ADH secretion to recover blood volume

Question 31

what inhibits ADH secretion. what does this cause

Answer 31

alcohol. causes physiologically innapropriate diuresis which results in dehyration, low blood volume, high ECF osmolarity which stimulates ADH secretion as alcohol is cleared. morning thirst is stimulated through hypothalamic thirst centre neurons connected to osmoreceptors