Question

Choose one of these hormones: Glucagon, Insulin, or Thyroid hormone.

1. What factors will stimulate the release of this hormone?
2. What are the metabolic effects of this hormone? (Be specific)
3. Is this hormone regulated by a positive or negative feedback mechanism?
4. Explain why.

Answer 1

Lets talk about insulin.

1. Factors causing its secretion

There are 2 ways that cause secretion of insulin.

A. Direct ways

High level of blood glucose

High level of blood fatty acids

High level of blood ketone bodies

High level of blood amino acids

B. Indirect ways

Insulin is secreted into blood by the activity of gastroinhibitory peptide, glucagon, gastrin, cholecystokinin, secretin and epinephrine.

Stimulation of secretion of insulin is associated with parasympathetic nervous system.

2. Metabolic effects of insulin

A. Carbohydrate metabolism

Promotes storage of glucose in liver, muscles and adipose by promoting glycogen synthesis and uptake of glucose and inhibiting gluconeogenesis and glycogenolysis.

Net effect - hypoglycemia

B. Protein metabolism

Stimulate RNA polymerase activity to form mRNA which forms proteins by translation. It inhibits the acitivity of transaminase.

Net effect - anabolism

C. Lipid metabolism

Increase synthesis of fatty acid, triglyceride and cholestrol. Inhibit lipolysis.

Net effect - lipogenesis

3. Regulation of insulin

This hormone causes blood glucose level to decrease. So, whenever the level of glucose falls and reach normal levels, then insulin secretion will be stopped. This will be negative feedback regulation.

Please rate.