Question

1. You just has a bunch on twinkies for breakfast. Initially, you feel pretty good, but then feel low energy. After a few hours, you start to feel a little better. Describe what is happening to glucose regulation starting from just before before breakfast to a few hours after you eat. Be sure to mention what is happening in the pancreas, liver, muscle and adipose.  

2. After consuming a high salt diet, why to both ANF and AVP go up together?

Answer 1

Answer with discussion and explanation :

1. As we know glucose is the ultimate carbohydrate fuel for our body to need the metabolic demands.Two main hormones regulating glucose level in our body are insulin and glucagon. Insulin is secreted from beta cell of pancreas in response to food and high blood glucose while glucagon is released from alpha cells of pancreas in response to low blood sugar.

A) Before breakfast :

Before breakfast blood sugar is in the lower range and to avoid further fall of blood sugar (hypoglycemia) glucagon is released from alpha cells of pancreas.

Glucagon acts on liver to promote Glycogenolysis (activates glycogen phosphorylase) and gluconeogenesis releasing glucose from the liver.

Glucagon also acts on muscle to break stored glycogen and release glucose.

Glucagon acts on adipose tissue to promote lipolysis to release fatty acids which can be used as energy source by beta oxidation, thus conserving glucose indirectly. Glucagon also antagonises the inhibitory action of insulin on hormone sensitive lipase thus promoting lipolysis.

B) After breakfast:

As soon as food reaches intestine chemical mediators from gut termed as incretins and rising blood sugar level (absorbed glucose after digestion enters blood) stimulate insulin secretion from beta cells of pancreas. Insulin promotes entery of glucose in various organs or cells such as liver, muscle,adipose tissue, red blood cells via glucose transporters (GLUT).

Insulin acts on liver to promote glycogen synthesis by activating glycogen synthase and inhibits glycogenolysis by inhibiting glycogen phosphorylase. Insulin also inhibits gluconeogenesis.

Insulin acts on muscle to promote glycogen storage and inhibits glycogenolysis.

Insulin inhibits hormone sensitive lipase thus inhibiting lipolysis and promotes lipid storage.

2.Taking high salt in diet leads to higher sodium content in the blood.This higher sodium content will raise the osmolarity of blood and in turn activates osmoreceptors of the brain.Stimulation of osmoreceptors will lead to thirst sensation and release of Arginine vasopressin from posterior pituitary (AVP is synthesised in hypotahlamus and is stored in posterior pituitary before release in the circulation).This antidiuretic hormone acts on kidneys to increase water reabsorption in an attempt to reduce osmolarity of blood.

Raised sodium and osmolarity will extract fluid from intracellular space thus increasing blood volume. This increased sodium and blood volume will stretch the myocardium of the heart. The stretched atria release a hormone which promotes sodium diuresis from the kidney and thus called as atrial natriuretic peptide or factor.

Thus, in case of incresed sodium intake both AVP and ANF are released in order to maintain sodium and fluid balance of the body.