4 HP Axis pt 1 Flashcards
what did aristotle say about the pituitary gland?
major connection through the 4 essential humours pass from the brain into the body
what did Rathke do about the pituitary gland?
distinguished 2 parts: anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)
what did Pierre Marie do?
associated pituitary tumors with acromegaly in 1886
what did Cushing do?
pioneered modern neurosurgical techniques
what functions were discovered to be controlled by the pituitary?
- growth (GH)
- lactation (PRL)
- action on thyroid (TSH)
- action on the adrenals (ACTH)
- action on the gonads (LH & FSH)
what is the pituitary gland controlled by?
the nervous system via the hypothalamus
what components make up the hypothalamo-hypophyseal tract?
- rathke’s pouch
- infundibulum
where does the infundibulum come from? where does it go?
it’s an outgrowth of the neuroectoderm from the floor of the third ventricle.
gives rise to pituitary stalk, median eminence, posterior pituitary
what is a nucleus in the context of the hypothalamic-pituitary axis?
group of similarly functioning neurons
how are the hypothalamus and pituitary glands connected?
- ant. pituitary’s got hella vessels that’s connected to the median eminence
the picture looks like a seahorse and like, where the head and neck meet, that’s where the median eminence starts. also on the head there’s secretory neurons that are the seahorse’s antlers
so releasing factors go from median eminence to the pituitary
there’s also some retrograde blood flow to enable negative feedback from pit to hypothalamus
what’s the adenohypophysis?
anterior pituitary gland (they both start with A)
what’s a plexus?
a highly vascularized area
hi ruru
:)
where do the nerve endings go in the anterior pit?
in the plexus regions. it’s where releasing hormones are released.
pituitary enter the bloodstream via _____ capillaries
venous
describe how the hypothalamus can control the pituitary gland
- seahorse: nerve endings in the median eminence release hormones here
- hormones are uptaken in capillaries
- take a hike to the anterior pituitary via portal vein
- trigger the anterior pituitary to release a second wave of hormones
- 2nd wave hormones enter bloodstream via venous capillaries
describe how nerves are situated in the posterior pituitary
posterior pituitary’s got the axons whose cell bodies are in the hypothalamus
what hormones are produced in the neuronal cell bodies of the hypothalamus?
oxytocin, vasopressin (ADH)
true or false: oxytocin and vasopressin are packaged stored in granules
true
what happens when neurons in the hypothalamus are stimulated?
triggered to release hormones from axon tips located in posterior pituitary; hormones get uptaken by capillaries there
why aren’t oxytocin and vasopressin considered neurotransmitters even though they originate from neurons?
they don’t travel to the next neuron; they get released into the bloodstream
how were the functions of the hypothalamic nuclei discovered?
selective destruction of areas
what kind of neurons are in the hypothalamus?
- magnicellular
- parvicellular hypophyseotropic neuron
- hypothalamic projection neuron
describe magnicellular neurons
start in hypothalamus, end in posterior pituitary; release hormones into capillaries there
describe parvicellular hypophyseotropic neurons
start in hypothalamus, end in median eminence in the anterior pituitary gland where they release their hormones
describe hypothalamic projection neurons
these neurons connect to other neurons, like what you would classically see in the central nervous system
where does the hypothalamus receive sensory inputs from?
inside and outside babeyyy
what’s nociception?
pertains to how you feel pain; happens to be one of the many stimuli for your hypothalamus
target outputs of the hypothalamus?
- anterior and posterior pituitary gland
- cerebral cortex
- premotor and motor neurons in brainstem/spinal cord
- parasympathetic and sympathetic preganglionic neurons
gimme the abbreviations of the circumventricular organs
- OVLT
- SFO
- ME
- SCO
- AP
expand OVLT
organum vasculosum of the lamina terminalis
expand SFO
subfornical organ
expand ME
median eminence
expand SCO
subcommissural organ
expand AP
area postrema
what characterizes the circumventricular organs?
- rich blood supply w/permeable vessels
- exposed to hormones, metabolites, and toxins
name some hypothalamic nuclei
- supraoptic
- paraventricular
- hypothalamic-hypophysiotropic (PeVH, PVH, Arc)
true or false: the granules in the supraoptic and paraventricular nuclei are visible
true - they can be seen traveling down the axons
true or false: the granules in the hypothalamic-hypophysiotropic nuclei are visible
true, but only in the axon terminal
what do the supraoptic and paraventricular nuclei produce?
oxytocin or vasopressin
what methods are used to assess the target cells in the anterior pituitary gland?
- electron microscopy
- staining for a particular hormone
hypothalamic hormones that affect the anterior pituitary have a (short/long) half-lfie
short
what happens after hypothalamic hormones bind to the target cells in the anterior pituitary?
trigger exocytosis of hormone granules
what stops the anterior pituitary from continuing the release of hormone granules?
feedback control through modulation of receptor numbers
the hypothalamus can prompt the anterior pituitary to send out signals. what kinds of signals are these and what are some examples?
Signaling by G proteins
ex)
- tropic hormones: Gsa and Gqa proteins; increases Ca2+ and exocytosis of hormone granules
- inhibitory hormones: Gia somatostatin and dopamine
why does the anterior pituitary rely so much on the renewal of stimulus?
because the hormones released by the hypothalamus have short half-lives
hormone release from the hypothalamus is _____
pulsatile
expand SCN
suprachiasmatic nucleus
what does the SCN do?
circadian pacemaker; susceptible to light
which hormone is the major one secreted by the pineal gland?
melatonin
when do melatonin levels peak?
middle of the night
what functions other than monitoring the circadian rhythm does the pineal gland do?
- induction of sleep
- depression of reproductive activity in animals
- affects seasonal breeding
where are melatonin receptors found
almost everywhere
what are some other functions of melatonin?
- adjustment of jet-lag
- sleeping aid
- antioxidant
- enhancement of immunity
- “health food additive”
what are some adverse side effects to taking melatonin?
- daytime sleepiness
- hypothermia
- desensitization of melatonin receptors
- bad stuff if you have a seizure disorder
- interaction with blood thinners
which pituitary hormones are single-chain proteins?
ACTH, GH, PRL
which pituitary hormones are glycoproteins with 2 subunits?
LH, FSH, TSH
