[Physio Final] 9 Hormones- Insulin and Glucagon

Effects of insulin on fat.

1. Enhances the entry of fatty acids from the blood into adipose tissue. 2. Increases transport of glucose into adipose tissue by GLUT-4. 3. Promotes chemical reactions that use fatty acids and glucose for triglyceride synthesis. 4. Inhibits lipolysis, thus reducing the release of fatty acids from adipose tissue into the blood.

Effects of insulin on carbohydrates.

1. Facilitates glucose transport into cells. 2. Stimulates glycogenesis in skeletal muscle and the liver. 3. Inhibits glycogenolysis 4. Inhibits gluconeogenesis in the liver.

Effect of glucagon on carbohydrates.

1. Increase in hepatic glucose production and release, resulting in increase blood glucose levels.

General effects of insulin.

1. Lowers blood levels of glucose, fatty acids, and amino acids and also promotes their storage. 2. Promotes cellular uptake and conversion into glycogen, triglycerides, and protein.

Effect of insulin on protein.

1. Promotes active transport of amino acids from blood into muscles 2. Increases rate of amino acid incorporation into protein. 3. Inhibits protein degradation. Te collective result of these actions is a protein anabolic effect. For this reason, insulin is essential for normal growth.

What are the 2 ways in which insulin excess can occur?

1. Too much insulin injected, resulting in insulin shock. 2. Blood level may rise whose beta cells are overresponsive to glucose.

What stimulates GH secretion?

1. deep sleep 2. stress 3. exercise 4. hypoglycemia

Aside from blood glucose concentration, what other factors promote insulin secretion?

1. increased blood amino acid levels 2. gastrointestinal hormones in response to food, namely glucose-dependent-insulinotropic peptide (GIP) 3. autonomic nervous system (parasympathetic NS)

How does glucagon exert it's hyperglycemic effects?

By deacreasing glycogen synthesis, promoting glyogenolysis and stimulating gluconeogenesis.

How does insulin decrease the concentration of blood glucose?

By promoting the cells' uptake of glucose from the blood for use and storage while simultaneously blocking the two mechanisms by which the liver releases glucose into the blood (glycogenolysis and gluconeogenesis).

General effect of insulin on fat.

Favor removal of fatty acids and glucose from the blood and promote their storage as triglycerides.

An elevated blood glucose level stimulates insulin secretion but inhibits glucagon secretion, whereas a fall in blood glucose level leads to decreased insulin secretion and increased glucagon secretion.

FYI

An elevated blood glucose level, such as during absorption of a meal, directly stimulates the β cells to synthesize and release insulin. The increased insulin, in turn, reduces blood glucose to normal and promotes use and storage of this nutrient.

FYI

In short, insulin primarily exerts its effects by acting on the liver, adipose tissue, and nonworking skeletal muscle. It stimulates biosynthetic pathways that lead to increased glucose use, increased carbohydrate and fat storage, and increased protein synthesis. In so doing, this hormone lowers the blood glucose, fatty acid, and amino acid levels.

FYI

Insulin-dependent cells maintain a pool of intracellular vesicles containing GLUT-4. Insulin induces these vesicles to move to the plasma membrane and fuse with it, thus inserting GLUT-4 molecules into the plasma membrane. In this way, increased insulin secretion promotes a rapid 10- to 30-fold increase in glucose uptake by insulin-dependent cells.

FYI

Which glucose transporter (GLUT) transports glucose across the blood-brain barrier?

GLUT-1

Which GLUTs makes the brain freely permeable to glucose at all times?

GLUT-1 and GLUT-3

Which glucose transporter (GLUT) is the main transporter of glucose into neurons?

GLUT-3

Which glucose transporter (GLUT) is responsible for the majority of glucose uptake by most body cells?

GLUT-4

Tip for remembering glucagon effects.

Glucagon effects are just the opposite of insulin. Insulin-lower blood glucose so glucagon raises blood glucose

Why must insulin be injected and not swallowed?

If it was swallowed, it would be digested by proteolytic enzymes in the stomach and small intestine.

What triggers increased glucagon secretion?

In response to a fall in blood glucose.

Metabolic effects of epinephrine and cortisol.

Increase blood glucose levels. Cortisol also mobilizes amino acids by promoting protein catabolism.

Effect of glucagon on fat.

Increase blood level fatty acids by promoting fat breakdown and inhibits triglycerides synthesis.

When does glucagon secretion increase? Decrease?

Increases during the postabsorptive state. Decreases during absorptive state.

Effect of glucagon on protein.

Inhibit hepatic protein synthesis and promotes degradation of hepatic protein.

___________________ encompasses a cluster of features that predispose the person to developing Type 2 diabetes and atherosclerosis.

Metabolic syndrome

Review figure 17-26. pges 532-534

Okay.

General effect of insulin on protein.

Protein anabolism, thus insulin is essential for normal growth.

Effects of GH on muscle.

Protein anabolism.

Insulin metabolism is characteristic of the _________ state.

absorptive state

The primary control of insulin secretion is a direct negative-feedback system between __________ and ___________.

beta cells and blood glucose levels

Glucagon promotes protein catabolism in the liver, but it does not have any significant effect on __________________ levels. Why?

blood amino acid, because it does not affect muscle protein, the major protein store in the body.

Which tissues do not depend on insulin for their glucose uptake?

brain, working muscles, and liver

Insulin has important effects on __________, ____________, and ____________ metabolism.

carbohydrate, fat, and protein

Diabetes ____________ is a result of vasopressin deficiency.

diabetes insipidus

Diabetes _____________ is a result of insulin insufficiency.

diabetes mellitus

____________ is the conversion of amino acids into glucose in the liver.

gluconeogenesis

Glucose transport between blood and cells is accomplished by means of a plasma membrane carrier known as a __________________________.

glucose transporter (GLUT)

_________________ is the production of glycogen from glucose.

glycogenesis

_____________ is the breakdown of glycogen into glucose.

glycogenolysis

One of the most prominent features of diabetes mellitus is ___________________.

hyperglycemia (excess blood glucose)

When β cells are overresponsive to glucose, it's called ____________________.

hypoglycemia

Insulin excess is characterized by _________________.

hypoglycemia (low blood glucose) (thus, brain starves b/c not enough glucose to the brain)

Which type of diabetes mellitus is characterized by a lack of insulin secretion because of erroneous autoimmune attack against the pancreatic β cells?

type 1 diabetes mellitus (10% of all cases of diabetes)

Hormones released from the digestive tract that "notify" the pancreatic β cell of the impending rise in blood nutrients (primarily blood glucose) are termed ______________.

incretins

GLUT-4 only operated at the bidding of ____________.

insulin

What is the only hormone capable of lowering blood glucose?

insulin

Insulin alone can reduce blood glucose and blood fatty acid levels, whereas glucagon, epinephrine, cortisol, and GH all increase blood levels of these nutrients. These other hormones are therefore considered ____________________.

insulin antagonists

Diabetes is the leading cause of _________ and __________ in the US.

kidney failure and blindness

What is the major site of action of glucagon?

liver

Which type of diabetes mellitus is when insulin secretion may be normal or even increased, but insulin's target cells are less sensitive than normal to this hormone?

type 2 diabetes mellitus

Many Type 2 diabetics have __________________, or syndrome X, as a forerunner of diabetes.

metabolic syndrome

What triggers the insertion of GLUT-4 into the plasma membranes in the absence of insulin?

muscle contraction (thus, exercise is important in managing diabetes melltius)

____________________ are the most important regulators of normal fuel metabolism.

pancreatic hormones

Insulin secretion is reduced during the _____________ state.

postabsorptive state

Where is GLUT-4 abundant?

resting skeletal muscle and adipose tissue

Insulin promotes glucose uptake by _____________________.

transporter recruitment

Which type of diabetes mellitus require exogenous insulin for survival? aka insulin injections, pumps, etc.

type 1 diabetes mellitus