Physiology - Endocrine - Pancreas

Insulin and glucagon control fuel flow and utilization
Three principal tissue types involved:
Metabolite targets include:
Effects

The bulk of the pancreas serves _____. The endocrine functions are performed by _____, small groups of cells scattered through the pancreas, representing about 2% of pancreatic mass.

Cell types of the Islets of Langerhans:

Synthesis of insulin

The half-life of insulin in the circulation is ____.

C-peptide offers a useful measure of ______ in patients under ______, because it is released in direct proportion to endogenous insulin generation but is not present in the injected insulin.

The principal mechanism for control of plasma glucose levels:
Normally _____ plasma lvl
As glucose increases, ______ secretion is stimulated.
When plasma glucose falls below the normal range, ______ secretion is increased.

________ condition occurs during a long term fast, and insulin lvl ___________.

Mechanism of glucose regulation of insulin secretion

Factors affecting insulin secretion: stimulators

Factors affecting insulin secretion: inhibitors

Insulin action on cells: Binding of insulin to its receptor causes ________ of the receptor, which then acts as a _______ that phosphorylates ______, which then _______ in other proteins and enzymes. Numerous target enzymes are ultimately activated or inactivated, and the result is to stimulate _______. Transport of amino acids, potassium, magnesium, and phosphate is facilitated by other mechanisms. The synthesis of various enzymes is induced or suppressed by changes in gene expression.

Mechanism of insulin activation of glucose transport: Cycling of _____ through _____ in insulin-sensitive tissues. Activation of the insulin receptor causes activation of _____, which speeds translocation of the _____. The GLUT4 transporters then mediate glucose transport into the cell.

Glucose transporter families

Principal actions of insulin: Rapid (seconds)

Principal actions of insulin: Intermediate (minutes)

Principal actions of insulin: Delayed (hours)

Glucagon is a _____ hormone synthesized in the ____ cells of the _____ pancreas.
• It is synthesized initially as a ______.
• Glucagon has a half-life of ___, and is degraded by ______.

organs other than the liver are exposed to relatively low levels of glucagon because

Glucagon release is inhibited by plasma glucose over a range between ________ to ____. Therefore, the regulation of glucagon by glucose is well tailored to its glycogenolytic and gluconeogenic actions to _______ from liver.

Stimulators of glucagon secretion

Inhibitors of glucagon secretion

effect of glucagon:

Somatostatin is produced in ______ of the pancreas, but is also formed in other locations including the ______. Its release is stimulated by ___________.

The principal effect of pancreatic somatostatin is to _________. This appears to rely on a _______ action, perhaps acting predominantly _______.

In the GI-tract, somatostatin has effects to _________.

Metabolic effects of epinephrine (NE has a lesser role in regulating metabolism):

The major effect of cortisol is to __________. The glucose is stored as ______ and released for use by other tissues

Cortisol ____ the stimulation of glucose uptake by insulin in peripheral tissues (muscle and fat).
Cortisol causes _____ of fat from adipose tissue, but can also ______ in selected adipose tissue sites.

Compare to glucagon, cortisol is

Leptin is a _____ hormone produced by ______. It is formed and secreted in proportion to _______, thus "report" the size of the adipose mass to the hypothalamus and other brain areas.

When excessive food intake leads to an increase in adipose mass, the plasma level of leptin _______, and this leads to a series of behavioral and metabolic changes designed to _______, such as to _________________.

Blood glucose

Glucose uptake

Glycogenesis

Glycogenolysis

Gluconeogenesis

Glycolysis

Protein

Fat

A common cause of hypoglycemia is ______. The brain is particularly sensitive to hypoglycemia, because ________.