Endocrine Physiology

Question 1

What are the three stimuli that hormones are regulated by

Answer 1

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

Question 2

What is up regulation in regards to hormonal change

Answer 2

Formation or increase in sensitivity of receptors to ligands

Question 3

What is down regulation in regards to hormonal change

Answer 3

Removal or desensitization of receptors to ligands

Question 4

How does concentration of a hormone relate to its speed and rate of release

Answer 4

The more concentration of a hormone you have the faster it will release and spread

Question 5

What is the half life of a hormone

Answer 5

Amount of time needed for the body to decrease the blood concentration by one half

Question 6

In what two ways does the hypothalamus control the pituitary release of hormones

Answer 6

The posterior pituitary (pars nervosa) which is modulated by action potentials in the hypothalamus
Anterior pituitary (pars distalis) which is modulated by hypothalmic hormones

Question 7

What three nuclei make up the hypothalamus

Answer 7

Paraventriculus
Supra optic nucleus
Arcuate nucleus
These all contain neurons that communicate with the pituitary gland

Question 8

What does the posterior pituitary do and what is another name for it

Answer 8

Releases neurohormones that are received from the hypothalamus and transported down the nerve fibers as part of the hypothalamic hypophyseal tract

Question 9

What does neurophysin do in the posterior pituitary

Answer 9

It’s a carrier protein that transports oxytocin and vasopressin to the posterior pituitary

Question 10

What is the anterior pituitary also know as and what is is made of

Answer 10

Adenohypophysis
Made of glandular tissue

Question 11

Explain the pathway that oxytocin follows and what does it result in

Answer 11

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

Question 12

What is vasopressin and describe how it is released

Answer 12

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

Question 13

What happens when vasopressin binds to the V1 receptors in the blood vessels

Answer 13

Vasopressin binds to the V1 receptor and then moves through the PIP2/IP3 pathway
This then stimulates muscle contraction and vasoconstriction

Question 14

What happens when vasopressin binds to the V2 receptor in the collecting ducts

Answer 14

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

Question 15

What secretes the growth hormone

Answer 15

Somatrotrophic cells of the anterior pituitary

Question 16

Explain how the growth hormone leads to target growth

Answer 16

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

Question 17

Explain how the thyroid stimulating hormone leads to the release of T3 and T4

Answer 17

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

Question 18

Explain how prolactin leads to milk production

Answer 18

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

Question 19

Explain the pathway calcitonin takes to be released

Answer 19

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

Question 20

Explain the parathyroid hormone pathway

Answer 20

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

Question 21

When calcitonin binds to its receptor it makes OPG. What does OPG inhibit

Answer 21

OPG inhibits the RANKL pathway which is how calcitonin decreases the amount of Ca being put into the blood

Question 22

What do mineralcorticoids regulate and what is the most important one

Answer 22

Regulates electrolyte levels, mostly K+ and Na
Na concentration correlates with water volume
Aldosterone is most important

Question 23

Explain the Aldosterone pathway

Answer 23

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

Question 24

What is adrenocorticotropic hormone and how does it work

Answer 24

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

Question 25

What does gonadotropin releasing hormone stimulate the release of

Answer 25

LH and FSH

Question 26

Explain the LH pathway

Answer 26

GNRH released from pre optic nucleus which stimulates the ant pit
Ant pit releases LH which then uses a modified pip2 pathway
Binds to leydig cells in the testes to release testosterone or binds to granulosa cells in the ovaries to release steroids like progesterone

Question 27

Explain the FSH pathway

Answer 27

In the testes FSH targets spermatogonia and triggers maturation of the sperm cells
In the ovaries it targets ovarian follicles and increasing metabolism and cell differentiation into a mature follicle and steroid production

Question 28

Explain the thyroid hormone pathway

Answer 28

TSH stimulates the follicular cells of thyroid and releases T4 and T3
These then go to multiple target tissues and their end result is an up regulation of transcription and metabolism

Question 29

What is the more active hormone T3 or T4

Answer 29

T3 so T4 will be converted into T3

Question 30

In some vertebrates what can T3 and T4 lead to

Answer 30

Apoptosis or metamorphosis

Question 31

What happens in the glucocorticoid pathway

Answer 31

ACTH is released by the pituitary and targets the zonal fsciculata
This then releases the glucocorticoids which target multiple cell types and initiate the camp pathway
The Glut4 glucose transporters are then deactivated and there is a decrease in glucose uptake
This increases circulation of blood glucose levels

Question 32

What is melatonin

Answer 32

Produced by the pineal gland
Inhibits hypothalamus nuclei and camp pathway which causes drowsy sensation

Question 33

Explain the insulin pathway

Answer 33

There is an increase in glucose levels in the blood and glucose enters the beta pancreatic islets
Then there is an increase in intracellular glucose which increases intracellular ATP levels
ATP then activates K+ channels and changes the membrane potential which leads to exocytosis of insulin
Insulin then targets hepatocytes which leads to the PI3k and mTDR pathway
This leads to increase in transcription of glucose channels which lead to increase glucose uptake by hepatocytes which leads to decrease blood glucose levels

Question 34

Explain the glucagon pathway

Answer 34

There is a decrease in amylin levels which means a decrease glucose levels
Amylin then doesn’t bind to receptors on alpha cells which leads to glucagon release
Glucagon then targets hepatocytes which triggers the camp pathway and an enzyme that breaks down glycogen is activated
There is then an increase in intracellular hepatocytes glucose levels
Glucose is released from hepatocytes and there is an increase in glucose blood levels