1.1 Hypothalamus and Pituitary Flashcards
Described the spatial relationship between the pituitary gland and the:
- Hypothalamus
- Optic chiasm
- Sphenoidal sinus
- Cavernous sinus
- Hypothalamus is superior
- Optic chiasm is superior
- Sphenoidal sinus is inferoanterior (in the sphenoid bone)
- Cavernous sinus is lateral (runs around the pituitary)
What are the four “pars” sections of the pituitary. How does this tie in with the two lobes?
- Anterior lobe (adenohypohysis): pars distalis, pars intermedia
- Posterior lobe (neurohypophysis): pars nervosa
Which vessels supply blood to the pituitary (?origin), and where does blood drain? What is unusual about the blood supply to the anterior pituitary?
- Supplied by superior (mostly adeno-) and inferior (mostly neuro-) hypophyseal arteries (which originate from the internal carotid artery)
- Blood drains predominantly into surrounding cavernous sinus
- Unusually, when blood travels from the sup. hypophyseal artery to reach the adenohypophysis, it travels through two separate capillary networks in the process (why might this be?…)
Which hormones from the adenohypophysis are direct acting vs control other glands?
Direct acting = clean = PG = prolactin and GH
Control other glands: ACTH, TSH, FSH, LH
Which hormones are released from the neurohypophysis? Describe their production, storage, and release
- Vasopressin and oxytocin are made there
- Produced in cell bodies in the hypothalamus, and transported to the nerve endings of cells in the posterior pituitary
- Here, they are stored in vesicles known as Herring bodies. When an AP is released, these hormones can be released into the bloodstream, draining into the cavernous sinus
Briefly outline the embryonic development of the pituitary glands two lobes
- Roof of oral cavity invaginates to form the hypophyseal diverticulum
- Floor of third ventricle invaginates to form the neurohypophyseal diverticulum
- They wrap around one another forming, the pars tuberalis the infundibulum etc.
What is the name of the type of glial cell that makes up most of the posterior pituitary? What does it do? Does it produce hormones?
- Pituicyte
- Important for storage and release of hormones from the neurohypophysis
- Does not produce hormones
Parvocellular vs magnocellular neurons in relation to the lobes/functions of the pituitary
Parvo (small): release hypophysiotropic hormones into the hypothalamo-hypophyseal portal system
Magno (large; adductor magnus etc.): release vasopressin and oxytocin
What are the names of the two hypothalamic nuclei where the hormones of the neurohypophysis are produced?
- Paraventricular nucleus
- Supraoptic (chiasm) nucleus
List three functions of oxytocin (and the triggers of the main two)
- Contraction of myoepithelial cells to allow milk release from the breast (triggered by suckling)
- Contraction of myometrium during childbirth (clamping vessels also prevents excess blood loss) (triggered by stretching of uterus)
- Bonding (parental, romantic, platonic etc.)
Which structural type of receptor does oxytocin act on?
G protein coupled receptors
What two stimuli can trigger ADH release? What/where are the receptors that detect this?
- Increased plasma solute concentration (detected by osmoreceptors in the hypothalamus)
- Decreased blood pressure (detected by baroreceptors in blood vessels e.g. carotid sinuses)
Why does it make sense that ADH increases ACTH release?
- ACTH exerts a modest effect on aldosterone
- Aldosterone causes increased retention of Na+ ions (and therefore water)
- Since ADH aims to retain water, this makes sense
What are the three main actions of ADH?
- Increased water reabsorption from renal collecting tubules (via aquaporin insertion)
- Arteriolar vasoconstriction (vasoPRESSin); this increases blood pressure
- Increased ACTH release from anterior pituitary
Hormonally, why do drunk people often piss in public?
Inhibited ADH release -> more water lost in urine
