case 6 - PBL and somatostatin

Question 1

what are the three parts of the hypothalamus that regulate food intake

Answer 1

ventromedial nuclei
Lateral hypothalamic area - known as the hunger centre
Arcuate nucleus

Question 2

what is the satiety centre

Answer 2

the ventromedial centre

Question 3

how is thirst detected

Answer 3

the osmoreceptors in the hypothalamus detect sodium concentration in the blood

in response to this high sodium level, the hypothalamus activates the thirst mechanism and concurrently stimulates the release of antidiuretic hormone

Question 4

what are the thirst areas in the brain

Answer 4

lateral hypothalamic area
Hypothalamic paraventricular nucleus
Periaqueductal gray

Question 5

what is the result of glucose transport in beta cells in T2DM being reduced

Answer 5

shifting the control point for insulin secretion from glucokinase to the glucose transport system. This defect is improved by the Sulfonylureas

Question 6

what is somatostatin also referred to as

Answer 6

growth hormone inhibiting hormone

Question 7

what is the structure of somatostatin

Answer 7

is a polypeptide hormone capable of inhibiting the actions of various pancreatic and gastrointestinal hormones

Question 8

what does somatostatin have high binding affinity to

Answer 8

five different SS receptors in the G protein coupled receptor superfamily

These receptors are coupled to inhibitory G proteins and are involved in motility, mucous and hormone secretion and inflammatory responses.

Question 9

what is somatostatin produced by

Answer 9

D cells in the stomach and duodenum and the delta cells in the islet of Langerhans in the pancreas

Question 10

what is SS secretion stimulated by

Answer 10

the presence of glucose, amino acids, and glucagon-like peptide-1

Question 11

what is somatostatins primary role in gastric physiology

Answer 11

Its primary role in gastric physiology is to inhibit both gastrin release and parietal cell acid secretion.

Question 12

what is somatostatins effect on gastric acid secretion

Answer 12

inhibits gastric acid secretion via an indirect and direct pathway

Question 13

why does it matter what the source of the somatostatin is

Answer 13

can act in a paracrine or an endocrine fashion

Question 14

where are D cells found in the stomach

Answer 14

found near the base of the oxyntic glands, the predominant gland type within the body and the fundus of ths tomach

Question 15

what happens once somatostatin is released into the stomach

Answer 15

Somatostatin binds to the a alpha-1 G protein coupled receptor on the basolateral membrane of the parietal cell

Question 16

what does this binding lead to

Answer 16

leads to the inhibition of adenylyl cylcase, antagonising the stimulatory effects of histamine, and thus inhibiting gastric acid secretion by parietal cells

Question 17

what is the indirect pathway

Answer 17

somatostatin can activate tow indirect paracrine pathways on G and D cells of the stomach

Question 18

what are examples of secretagogues and what are they

Answer 18

histamine and gastrin are both examples of secretagogues which are substances that cause another substance to be secreted and due to this function, Somatostatin can inhibit gastric acid secretion

Question 19

what happens in the corpus of the stomach

Answer 19

D cells release the hormone to inhibit the release of histamine from the ECL cells

Question 20

what happens in the antrum of the stomach

Answer 20

the release of somatostatin from the D cells inhibits the release of gastrin from the G cells.

this is an example of redundant regulatory pathways that control acid secretion

Question 21

what happens in the pancreas

Answer 21

somatostatin is secreted by delta cells

Question 22

what happens once somatostatin is released

Answer 22

it acts as a powerful inhibitor of glucagon and insulin secretion from the alpha and beta cells respectively

Question 23

what does glucose stimulate somatostatin via

Answer 23

G proteins

Question 24

what happens when blood glucose concentrations are high

Answer 24

activation of cellular receptors causes the closure of ATP-sensitive K+ channels, initiating membrane depolarisation and increasing somatostatin release from delta cells.

Question 25

how does somatostatin also suppress pancreatic exocrine secretions

Answer 25

through the inhibition of cholecystokinin-stimulated enzyme secretion and secretin-stimulated bicarbonate secretion

Question 26

give a summary list of gastrointestinal effects of somatostatin

Answer 26

Decrease gastrin release leading to reduced gastric acid

Increase fluid absorption

Increase smooth muscle contraction

Paracrine inhibition of insulin and glucagon secretion from α and β-cells of the Islets of
Langerhans

Decrease bile flow

Decrease blood glucose concentration

Question 27

what is somatostatin produced by aswell as the GI tract

Answer 27

the brain

Question 28

what is a key producer of this neuropeptide

Answer 28

hypothalamus, which predominantly synthesises the 14 amino acid form of the hormone in the periventricular region

Question 29

where is SS-14 released

Answer 29

into the hypophyseal portal blood stream

Question 30

what is SS

Answer 30

a potent growth hormone inhibitor

Question 31

what is control if GH regulated through

Answer 31

both positive and negative control

Question 32

give a summary of somatostatin neurological effects

Answer 32

Inhibits secretion of growth hormone from the anterior pituitary
Inhibits secretion of thyroid-stimulating hormone from the anterior pituitary