Endocrine Physiology Flashcards
What are the three stimuli that hormones are regulated by
Humoral- change levels of ions and nutrients, low calcium levels cause release of parathyroid hormone
Neural-nerve fibers stimulate hormone release such as sympathetic fibers releasing catecholamines from the adrenal gland
Hormonal - released as a response from another hormone such as the growth hormone being released in response to the growth hormone releasing hormone
What is up regulation in regards to hormonal change
Formation or increase in sensitivity of receptors to ligands
What is down regulation in regards to hormonal change
Removal or desensitization of receptors to ligands
How does concentration of a hormone relate to its speed and rate of release
The more concentration of a hormone you have the faster it will release and spread
What is the half life of a hormone
Amount of time needed for the body to decrease the blood concentration by one half
In what two ways does the hypothalamus control the pituitary release of hormones
The posterior pituitary (pars nervosa) which is modulated by action potentials in the hypothalamus
Anterior pituitary (pars distalis) which is modulated by hypothalmic hormones
What three nuclei make up the hypothalamus
Paraventriculus
Supra optic nucleus
Arcuate nucleus
These all contain neurons that communicate with the pituitary gland
What does the posterior pituitary do and what is another name for it
Releases neurohormones that are received from the hypothalamus and transported down the nerve fibers as part of the hypothalamic hypophyseal tract
What does neurophysin do in the posterior pituitary
It’s a carrier protein that transports oxytocin and vasopressin to the posterior pituitary
What is the anterior pituitary also know as and what is is made of
Adenohypophysis
Made of glandular tissue
Explain the pathway that oxytocin follows and what does it result in
Stretch receptors are activated by the fetus pushing on the placenta
Signal is sent to paraventricular and supraoptic nuclei of the hypothalamus
This generates a signal in the neurosecretory cells and oxytocin is released by the posterior pituitary
Oxytocin is then transported through the blood to the uterine smooth muscle where it binds to its receptor and initiates the PIP2/IP3 pathway
Smooth muscle contraction then occurs
What is vasopressin and describe how it is released
An antidiuretic hormone
Osmoreceptors detects a high osmolarity which means low water volume, low blood pressure
A signal is then sent to the paraventricular nucleus of the hypothalamus which stimulates release of vasopressin from the posterior pituitary
What happens when vasopressin binds to the V1 receptors in the blood vessels
Vasopressin binds to the V1 receptor and then moves through the PIP2/IP3 pathway
This then stimulates muscle contraction and vasoconstriction
What happens when vasopressin binds to the V2 receptor in the collecting ducts
Vasopressin binds to the V2 receptor and then moves through the camp pathway
Camp then produces aquaporins which lead to water retention/collection by the collecting ducts
What secretes the growth hormone
Somatrotrophic cells of the anterior pituitary
Explain how the growth hormone leads to target growth
A signal is sent to the arcuate nucleus of the hypothalamus and the neurosecretory cells release GHRH
GHRH then is transported by the blood to the anterior pituitary and GH is released
GHRH targets multiple tissues which stimulates the MAPK pathway which leads to cell proliferation and target growth
Explain how the thyroid stimulating hormone leads to the release of T3 and T4
Numerous inputs into the paraventriculus nucleus of the hypothalamus which leads to a stimulus release of thyrotropin releasing hormone
TRH then stimulates the release of TSH by the anterior pituitary
TSH targets the thyroid gland and binds to its receptor which initiated the camp and PIP2 pathway
This then leads to the production and release of T3 and T4
Explain how prolactin leads to milk production
Suckling generates a signal in the afferent neurons and they send a signal to the paraventricular nucleus
Dopamine release is then inhibited and prolactin is released by the anterior pituitary
Prolactin then targets mammary tissue and triggers the MAPK pathway which then leads to milk production
Explain the pathway calcitonin takes to be released
Ca sensory receptors detect an increase in blood calcium levels
A signal is then sent to the parafollicular cells of the thyroid gland which causes calcitonin to be released
Calcitonin targets osteogenic stem cells which produce OPG
OPG acts as an osteoclastgenesis receptor which decreases bone break down and decreased calcium released into the blood
Explain the parathyroid hormone pathway
Ca sensory receptors detect decreased calcium levels
A signal is sent to the parathyroid gland which release parathyroid hormone
PTH targets osteogenic stem cells which produce RANKL
RANKL produces osteoclasts which increases bone breakdown and increases blood calcium levels
When calcitonin binds to its receptor it makes OPG. What does OPG inhibit
OPG inhibits the RANKL pathway which is how calcitonin decreases the amount of Ca being put into the blood
What do mineralcorticoids regulate and what is the most important one
Regulates electrolyte levels, mostly K+ and Na
Na concentration correlates with water volume
Aldosterone is most important
Explain the Aldosterone pathway
There is a decrease of Na levels detected in the DCT
The juxtaglomerular cells release renin and renin triggers the release of angiotensin
Angiotensin triggers the release of aldosterone which targets cells in the DCT
The camp pathway in then activated to produce sodium channels which increases Na transport and Na retention which increases Na overall
What is adrenocorticotropic hormone and how does it work
Regulates glucocorticoids mainly cortisol and corticosteroid
Stimulated by low cortisol levels which means cortisol is unable to bind to corticotripic releasing hormone neurosecretory cells so it can’t inhibit the cells
This leads to a release of CRH which is transmitted through the blood to ant pit which leads to the release of ACTH
ACTH then moves through the blood and targets specialized cells in the adrenal gland which is part of the zona fasciculata
This triggers the camp pathway and leads to release of glucocorticoids (cortisol) which leads to increase glucose levels
