posterior pituitary Flashcards
sella turcica
sphenoid bone of the skull- features a protective pocket for the pituitary gland
what are the two anatomically and functionally distinct lobes of the pituitary
the posterior pituitary which is composed of nervous tissue
the anterior pituitary which comprises glandular epithelial tissue (endocrine)
what happens in the posterior pituitary
hormones which are packaged in the cell body of a neuron are released to the vein in the posterior pituitary
what happens after hormones which are packaged in the cell body of a neuron are released to the vein in the posterior pituitary
vesicles are transported down the cell and are stored in the posterior pituitary. They are then released into the blood.
what are the two hormones of the posterior lobe of the pituitary
oxytocin and vasopressin. they overlap in bioactivity
what are the other names for vasopressin
anti diuretic hormone ADH or AVP- arginine vasopressin
how is secretion controlled of the two hormones of the posterior lobe of the pituitary
independantly controlled from neurons within paracentricuolar PVN and supraoptic nuclei SO of the hypothalamus
what releases oxytocin and vasopressin into systemic blood
neuronal terminals in posterior pituiatary
how many hormones does each cell produce from its large precursor
only one from its large precursor, either prepro-oxyphysin or prepro-vasopressin
what are the roles of oxytocin
childbirth and breastfeeding
process of childbirth
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
process of breastfeeding
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
men and non pregnant women and oxytocin. what stimulates its release
orgasm or a long hug
where is oxytocin released in men and non pregnant women and oxytocin
as a neurotrasmitter in parts of the brain
what is the result in oxytocin release during bonding and sex
pair bonding- attatchment of couples and nurturing parental bahaviour. this is highly conserved in evolution
what is the importance of the hypothalamus
-site of interaction between nervous and endocrine systems
-many interconnections with other parts of the brain
-emotions and mental stress affect endorcine function
what feedback loop is vasopressin a part of
the feedback loop that controls body fluid volume and concentration
what target cells does vasopressin have
kidney cells to reduce urine production (anti diuresis) and conserve water
vascular smooth muscle to cause vasoconstriction which maintains blood pressure
what is the mechamism of action of ADH
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)
what is ADH mechanism mediated by
binding to specific receptors AVPR2 in cells of collecting ducts
secretion stimuli of vasopressin
high osmolarity of extracellular fluids- hyperosmolarity)
low blood volume
low arterial pressure
all of which stiumlate thirst
what sensorts detect osmolarity for vasopressin secretion
hypothalamic osmoreceptor neurons detect changes in extracellular fluid osmolarity.
what happens when there is a high ECF osmolarity
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
where do osmoreceptors lie
outside BBB
OVLT
organum vasculosum of lamina terminals
SFO
sunfornical organ
what corrects ECF hyperosmolarity
thirst sensation plus ADH release
where are blood volume sensors for control of ADH secretion
located in low pressure complaint (easily stretchable) vessels
Ex- large veins and heart atria
what do blood volume sensors for control of ADH secretion do
accomodate blood volume changes and buffer arterial pressure changes
what are blood volume sensors for control of ADH secretion made of
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
what inhibits ADH secretion. what does this cause
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
