Endocrine Communication

Question 1

What is the endocrine system?

Answer 1

A communication system using hormones as signalling molecules.

Question 2

What are hormones?

Answer 2

Molecules (proteins or steroids) that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.

Question 3

What are target cells?

Answer 3

For non-steroid hormones, cells that process a specific receptor on their plasma (cell surface) membrane. The shape of the receptor is complementary to the shape of the hormone molecule. Many similar cells together form a target tissue.

Question 4

What does the endocrine system use to transmit its signals?

Answer 4

The blood circulatory system.

Question 5

What are the signals released by the endocrine system called?

Answer 5

Hormones

Question 6

What are the two types of hormone?

Answer 6

Protein/peptide and steroid.

Question 7

Protein hormones are not soluble in the phospholipid bilayer so therefore what do they do?

Answer 7

Protein hormones need to bind to the cell surface membrane and release a second messenger inside the cell.

Question 8

From what are hormones released?

Answer 8

Endocrine glands.

Question 9

Describe the endocrine glands.

Answer 9

The endocrine glands are ductless glands - they consist of groups of cells that manufacture and release the hormone directly into the blood in the capillaries running through the gland.

Question 10

How come steroid hormones are able to have a direct effect on the DNA in the nucleus?

Answer 10

They are able to pass through the membrane.

Question 11

What is the benefit to having a receptor that is specific to one type of protein hormone?

Answer 11

It means that the hormone is not able to affect other cells that don’t have the receptor as it passes through the system.

Question 12

What are the two types of adrenergic receptor?

Answer 12

Alpha and Beta

Question 13

What do alpha receptors cause?

Answer 13

They are excitatory in smooth muscles and gland cells, but cause relaxation of intestinal smooth muscles.

Question 14

What are first-messengers?

Answer 14

Non-steroid hormones. They are signalling molecules outside of the cell that bind to the cell surface membrane and initiate an effect inside of the cell.

Question 15

What is the second messenger?

Answer 15

The second signalling molecule found inside the cell that is released when the first messenger binds to the cell surface membrane.

Question 16

What does the second messenger do?

Answer 16

Stimulates a change in the activity of the cell.

Question 17

What is a G-protein?

Answer 17

A second messenger that many non-steroid hormones rely upon.

Question 18

What does the G-protein do once it is activated by the non-steroid hormone?

Answer 18

The G-protein in turn activates an effector molecule - usually an enzyme that converts an inactive molecule into the active second messenger.

Question 19

What is the effector molecule in many cells?

Answer 19

The enzyme adenyl cyclase.

Question 20

What does adenyl cyclase do?

Answer 20

Converts ATP to cyclic AMP (cAMP).

Question 21

What does cAMP do?

Answer 21

It either acts directly on another protein (such as an ion channel), or it may initiate a cascade of enzyme controlled reactions that alter the activity of the cell.