Flashcards in Hypothalamus and pituitary Deck (63):
Where is the pituitary gland located?
At the base of the brain in a bony pocket called sella turcica.
How is the pituitary gland connected to the brain?
Stalk of tissue called the infundibulum containing nerves and special veins (long portal veins)
What are the parts of the pituitary gland?
Anterior lobe- pars distalis+ pars tuberalis
Posterior lobe- pars nervosa + pars intermedia
What are the 2 parts of the hypothalamus? What do they do?
1. Nuclei: clusters of nerve cells bodies that synthesize hypothalamic RH that regulats secretion of hormone from the anterior pit. gland and 2 posterior pit gland hormones (ADH/ OT)
2. Bottom portion: median eminence. Axon terminals containing hypothalamic RH. These RHs are secreted FIRST into capillaries of a portal system.
What hormones are produced by the posterior pituitary gland?
OT and ADH
Nerve axons at the posterior pituitary mainly come from? Where do they terminate?
2 nuclei in the hypothalamus- supraoptic nucleus and paraventricular nucleus
Near capillaries in the posterior pituitary. Stores and release hormones here.
Describe the structure of the pars nervosa of the posterior lobe
Neurosecretory nerve fibers from PV and SON
- Hypothalamohypopsheal T
What cell is associated with the pars nervosa of the posterior lobe of the pituitary
Function of pars nervosa of posterior lobe of pituitary
release of oxytoxin and ADH
What does oxytoxin do?
stimulates contraction of smooth muscle in pregnant uterus and myoepitherlial cells in mammary gland.
What does ADH do?
regulates body retention of water. Increases contracility of arterial smooth muscle to increase BP. Increase water reabsorption
Describe the structure of ADH and OT
nonapeptides with S-S, similar structures and overlapping activities
Describe the synthesis of ADH and OT
synthesized as much larger molecules (pro-), stored in granules with neurophysins I and II
Describe the secretion of ADH and OT
Secreted-when action potentials reach nerve terminals; analgous to neurotransmitter release secreted together with their respective neurophysins
What 2 things cause secretion of oxytocin?
dilation of cervix, suckling
What is the main stimuli of ADH?
decrease ECF volume (also increase osmolarity)
Where are osmoreceptors located?
hypothalamus: OVLT (SON and PVN?)
What does the intermediate lobe of the pituitary gland do?
It MAY secrete MSH.
What major hormones are secreted by the anterior pituitary?
GH, PRL, ACTH, FSH, LH, TSH
Chemical nature of ACTH
peptide that is split from POMC (pro-opiomelancortin). 39 aa straight chain. C terminus has most antigenic activity.
Only 20 aa @ N-terminus needed for biological activity
What is ACTH1-24?
ACTH structure that has full activity
What is MSH do?
stimulates synthesis of melanin in melanocytes- darkens skin
Where is the structure of MSH? What does this cause?
lies within ACTH- excess ACTH causes hyperpigmentation
What hormones secreted by anterior pituitary are glycoproteins?
TSH, FSH, LH
What cells make up 15-20% of pituitary volume?
What is the structure of the anterior pituitary glycoproteins?
dimers of a and b subunits. A is very similar among all 3 hormones. B is fairly similar.
What cells are stained to measure GH and PRL?
___ causes release of granules from posterior pituitary?
How do hormones get from hypothalamus to posterior pituitary?
How do hormones get from hypothalamus to anterior pituitary?
the hypothalamo-pituitary portal system- 2 capillary beds!
What kind of tissue makes up the pituitary?
Posterior: neural secretory
Neural extensions to the posterior pituitary from the hypothalamus come from _____.
2 nuclei--> SON and PVN
Oxytocin increases the contracility of _____
uterine smooth muscle and mypoepithelial cells of mammary glands--> milk let down
2 main oxytocin stimuli
suckling and dilation of cervix
What are the 2 main stimuli for ADH?
decrease in plasma volume by 5-10%
Increase osmolarity by 1-2%
In what 2 ways is ADH an example of negative feedback?
1. Water rebsorption negatively acts on osmolality so it doesnt act on SON and PVN
2. Increase plasma volume negatively acts on volume receptors so they dont signal to CNS
What are the effects of stalk section on nerve tracts to posterior pituitary?
(transient diabetes insipidus)
3. Nerve terminals develop and capillaries regrow (reversible)
In order to have an affect hormones have to diffuse in the _____.
What are the 6 cells in anterior pituitary? Which are basophils and which are acidophils?
Baso: FSH, LH, TSH, ACTH
Acid: GH, PRL
What subunit of glycoprotein do you measure?
Acidophils make up ____ of the ant. pituitary. What makes up this?
75%; 50% somatotrophs; 15-25 Lactotrophs
Target tissue of ACTH
Major actions of ACTH
increase adrenal growth, cortisol synthesis, cortisol secretion, plasma concentration of cortisol (--> vascular reactivity and gluconeogenesis)
Variables that increase release of ACTH
increase CRH, Stress, morning time, decrease of cortisol, removal of adrenal/s
Variable that decrease release of ACTH
decrease CRH, decrease stress, later in the day, increase cortisol, Rx ith glucocorticoids
Target tissue of TSH
thyroid gland cells lining follicles
Some major actions of TSH
increase thyroid growth, TH syn and secretion, TH concentration, iodide trapping, thy blood flow, and everything that T3 and 4 do--> increase metabolic rate
Variables that increase TSH
increase TRH, decrease T4 and 3, low iodide diets, removal of thyroid gland
Things that decrease release of TSH
decrease TRH, increase T4/3, increase SS, Rx with THs
Increase GnRH increases the secretion of what?
FSH, LH in males and females
What are all the RH and what do they increase?
GnRH--> LH and FSH
SS--> decrease GH
Dopamine--> decrease PRL
What is the long loop of feedback?
Target organ hormone negatively acts on Anterior pituitary and can -/+ affect hypothalamus
What is the short loop of feedback?
hormone released from anterior pituitary - on hypothalamus
Target tissue of PRL
Females: mammary glands
Males: testes, 2nd sex tissues
Some major actions of PRL
Female: glandular tissue growth, milk synthesis
Male: potentiate LH and testost. actions
Variables that increase PRL
Decrease PIH, Increase TRH, suckling
Variables that decrease PRL
increase PIH, stop nursing
Target tissue of GH
msot cells of body esp muscle liver, cartilage in growth plates
Variables that increase GH
increase GHRH AND decrease SS
Deep sleep, hypoglycemia, acute stress
Variables that decrease GH
decrease GHRH and/or increase SS
To increase ADH secretion, there must be a _____% decrease in plasma volume and a ______% increase in osmolarity.
Which is more sensitive to changes in circulating volume, RAS or ADH?#
RAS. ADH responds only to large decreases.