Hypothalamic pituitary axis

Question 1

describe relevant anatomy - when looking at a sagittal section

Answer 1

underneath the thalamus is the hypothalamus

the hypothalamus is connected to the pituitary gland via the medial eminence and the infundibulum

Question 2

describe relevant anatomy - when looking at a medial lateral section

Answer 2

surrounding the 3rd ventricle
-->periventricular layer
-->medial layer (parvocellular)
-->lateral layer (magnocellular)
paraventricular nucleus between medial and lateral layer
medial eminence at the bottom.

Question 3

describe infundibulum structure

Answer 3

connects hypothalamus to the pituitary gland
contains nerves, and portal vessels
–>vessels are fenestrated, enabling passage of substances (exception to blood brain barrier)

Question 4

describe anterior pituitary gland

Answer 4

has parvocellular neurosecretory cells, located in the paraventricular nucleus or preoptic area (hypothal)
synapse with portal vessels; neurohormones travel to specialised neurosecretory cells in the anterior pituitary gland, which produce hormones which are released into the bloodstream.

Question 5

describe how anterior pituitary gland contributes to stress regulation

Answer 5

stress occurs.
parvocellular neurosecretory cells release corticotropin releasing hormone, which goes via portal vessels to corticotrophs
releases adrenal corticotrophic hormone, which binds to adrenal cortex, which releases cortisol, which mobilises energy stores and reduces immune system function

Question 6

describe how anterior pituitary gland contributes to reproductive cycle

Answer 6

parvocellular neurostimulatory cells release gonadotrophin releasing hormone, which binds to gonadotrophs, which releases FSH and luteinising hormone; leads to estrogen production in females, testosterone/sperm production in males

Question 7

describe posterior pituitary gland

Answer 7

contains magnocellular neurosecretory cells; releases neurohormones into fenestrated vessels which go directly into bloodstream

Question 8

describe how posterior pituitary gland contributes to motherhood

Answer 8

increased contractions during labour occurs, or baby sucks on nipple
oxytocin released from posterior pituitary gland (magnocellular), released into bloodstream, resulting in increased contractions/milk production

Question 9

describe how posterior pituitary gland is involved in blood volume regulation

Answer 9

blood volume decreases due to dehydration or hemorrhage
vasopressin is released from magnocellular neurosecretory cells; goes into fenestrated tubes into bloodstream.
acts on kidneys, reducing water lost through pee.

Question 10

describe role of oxytocin and vasopressin released parvocellularly in prairie vs montane voles

Answer 10

NOT PRODUCED MAGNOCELLULARLY: IT STAYS WITHIN THE BRAIN.

in both species, both hormones are released during mating, and bind to receptors, resulting in the formation of a monogamous relationship (as oxytocin activates dopamine)
however, prairie voles have much more receptors than montane, resulting in monogamous vs polygamous behaviours

within prairie voles, level of oxytocin positively correlated to mating behaviours

Question 11

describe role of oxytocin produced parvocellularly in humans

Answer 11

related to trust, bonding and love.