14.1- Hormonal Communication

Question 1

Define endocrine gland?

Answer 1

A group of cells which are specialised to secrete chemicals (hormones) directly into the bloodstream. Is ductless.

Question 2

Define exocrine gland.

Answer 2

Secrete molecules through ducts to reach parts of the body.

Question 3

What are hormones and the different types?

Answer 3

Chemical messengers that carry information from one part of the body to the other.
-steriod, proteins, glycoproteins, polypeptides, amines, tyrosine.

Question 4

Hormone secretion

Answer 4

Secreted directly into blood when a gland is stimulated.

• can occur as a result of another hormone/nerve impulse.
• transported in blood plasma once secreted.
• diffuse out of blood and bind to specific receptor sites which are found on membranes/cytoplasm of cells in target organs.
• once bound to receptors, stimulate target cells to produce a response.

Question 5

Steroid hormones

Answer 5

-lipid soluble.
- pass through the lipid component of cell membrane.
- bind to steroid hormone receptors to form hormone-receptor complex.
- receptors can be present in cytoplasm or nucleus.
- hormone-receptor complex acts as a transcription factor which facilitates of inhibits transcription of certain gene.
Eg. Oestrogen.

Question 6

Non-steroid hormones

Answer 6

• hydrophilic so cannot pass directly through cell membrane.
• bind to receptors on cell membrane of target cells instead.
• this triggers a cascade reaction mediated by chemicals called secondary messengers.
  Eg. Adrenaline

Question 7

Adrenal glands

Answer 7

Two small glands (3x5cm) located on-top of each kidney.
Made up of 2 parts surrounded by a capsule:
1. Adrenal cortex- outer region. Produces essential hormones.
2. Adrenal medulla- inner region. Produces non-essential hormones.

Question 8

Adrenal cortex.

Answer 8

Production of hormones by adrenal cortex is controlled by pituitary gland. 3 main types of hormone produced:

1. Glucocorticoids.
2. Mineralcorticoids.
3. Androgens.

Question 9

Glucocorticoids.

Answer 9

Includes cortisol and corticosterone. Release is controlled by hypothalamus.

1. Cortisol:
   - helps regulate metabolism by controlling conversion of molecules into energy.
   - helps regulate blood pressure and cardiovascular function in response to stress.
2. Corticosterone:
   - works with cortisol to regulate immune response and suppress inflammatory reactions.

Question 10

Mineralcorticoids

Answer 10

Includes aldosterone. Release is mediated by signals triggered in kidney.
- helps control blood pressure by maintaining balance between salt and water concentrations in blood/body fluids.

Question 11

Androgens

Answer 11

Small amounts of male and female sex hormones are released.

• impact is relatively small compared to larger amounts of hormones like oeastrogen/testosterone.
• important especially in women after menopause.

Question 12

Adrenal medulla

Answer 12

Hormones are released when sympathetic nervous system is stimulated which occurs during stress.
Adrenaline and noradrenaline released.

Question 13

Adrenaline

Answer 13

Increases heart rate, sending blood to muscles and brain quickly.
-rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver.

Question 14

Noradrenaline.

Answer 14

• works with adrenaline in response to stress.
• produces effects such as increased heart rate, widening pupils, widening air passages in lungs
• narrowing of blood vessels in non-essential organs = increased bp