Session 2: Endocrine System

Question 1

What are feedback loops?

Answer 1

Physiological processes are commonly moderated via two distinct feedback mechanisms – positive and negative feedback. Homeostatic processes are controlled by negative feedback and hence these systems occur more commonly within the body to keep or return the body to a steady state. Positive feedback usually involves departure from the steady state and an increase in the change, so are less common.

Question 2

What do homeostatic feedback loops require?

Answer 2

Receptors (to detect changes), processing g (to determine response), and effectors (to return parameter to steady state)

Question 3

What are Endocrine and exocrine glands?

Answer 3

Endocrine glands release chemical substances directly into the bloodstream or tissues of the body. The chemical substances released by the endocrine glands are generally known as hormones. Exocrine glands release chemical substances through ducts to outside the body or onto another surface within the body (e.g. sweat).

Question 4

What are steroid hormones?

Answer 4

Steroid hormones are lipophilic – meaning they can freely diffuse across the plasma membrane of a cell and bind to receptors in either the cytoplasm or nucleus of the target cell, to form an active receptor-hormone complex. This activated complex will move into the nucleus and bind directly to DNA, acting as a transcription factor for gene expression. Examples include those produced by the gonads (estrogen, progesterone and testosterone)

Question 5

What are peptide hormones?

Answer 5

Peptide hormones are hydrophilic and lipophobic – meaning they cannot freely cross the plasma membrane so they bind to receptors on the surface of the cell. The receptor complex activates a series of intracellular molecules called second
messengers, which initiate cell activity and enables the amplification of the initial signal (as more molecules are activated) which then leads to alteration of cell activity. Peptide hormones include insulin, glucagon, leptin, ADH and oxytocin

Question 6

What is the hypothalamus?

Answer 6

The hypothalamus is a region at the base of the brain that links the nervous system to the endocrine system via its connection to the pituitary gland. It helps control the release of hormones from other endocrine glands. It also helps regulate (among other functions): body temperature, hunger, thirst, sleep.

Question 7

Describe the growth hormones.

Answer 7

A peptide hormone released from the anterior pituitary gland. It’s important for normal growth during childhood. It stimulates cells to grow and divide, makes long bones increase in length, increases muscle mass. GH is released during deep sleep repair of body tissues, has many secondary roles (glucose metabolism, immune system)

Question 8

Describe thyroxin (thyroid hormone)

Answer 8

Amine hormone released from the thyroid gland that acts on nearly every tissue in the body and is essential to the proper development and differentiation of cells. The primary role of thyroxin is to increase the basal metabolic rate (amount of energy the body uses at rest). This can be achieved by stimulating carbohydrate and lipid metabolism via the oxidation of glucose and fatty acids. It can also increase the body’s sensitivity to catecholamines (such as adrenaline)

Question 9

Describe insulin & glucagon.

Answer 9

Insulin is a peptide hormone released from beta (β) cells of the pancreas and causes a decrease in blood glucose concentration. This may involve stimulating glycogen synthesis in the liver (glycogenesis), promoting glucose uptake by the liver and adipose tissue, or increasing the rate of glucose breakdown (by increasing cell respiration rates)

Glucagon is a peptide hormone released from alpha (α) cells of the pancreas and causes an increase in blood glucose concentration. This may involve stimulating glycogen breakdown in the liver (glycogenolysis), promoting glucose release by the liver and adipose tissue, or decreasing the rate of glucose breakdown (by reducing cell respiration rates)

Question 10

Describe Diabetes

Answer 10

Diabetes mellitus is a metabolic disorder that results from a high blood glucose concentration over a prolonged period. Treatment involves lifestyle and diet changes, monitoring blood glucose levels and injections of insulin. Type 1 is when insulin is not produced by beta cells in the pancreas and hence glucose is not removed from the blood stream. Type 2 diabetes is when insulin is overproduced which leads to desensitisation of the insulin receptors and so glucose is not removed from the bloodstream. In normal function, insulin binds to insulin receptors and triggers the opening of glucose transporters in fat and muscle cells, allowing glucose removal from the bloodstream.