5.4.2: Adrenal glands

Question 1

What is the adrenal cortex?

Answer 1

The outer layer of the adrenal gland.

Question 2

What is the adrenal gland?

Answer 2

-One of a pair of glands lying above the kidneys, which release adrenaline and a number of other hormones known as corticoids (or corticosteroids) such as aldosterone.

Question 3

What is the adrenal medulla?

Answer 3

The inner layer of the adrenal gland.

Question 4

The adrenal glands are a good example of what type of gland?

Answer 4

-An endocrine gland.

Question 5

where re the adrenal glands found?

Answer 5

They are found lying anterior to the kidneys- one on each side of the body.

Question 6

Describe the structure of an adrenal gland and how they release hormones.

Answer 6

• Each gland is divided into the outer adrenal cortex and the inner adrenal medulla.
• Both regions are well supplied with blood vessels and produced hormones which are secreted directly into the blood vessels.

Question 7

The adrenal gland has an outer cortex capsule surrounding three distinct layers of cells. What are they?

Answer 7

• Zona glomerulosa
• Zona fasciculata
• Zona reticularis

Question 8

What is the zona glomerulosa?

Answer 8

The outermost layer, which secretes mineralocorticoids

Question 9

What is the zona fasciculata?

Answer 9

The middle layer, which secretes glucocorticoids such as cortisol.

Question 10

What is the zona reticularis?

Answer 10

The innermost layer, which is thought to secrete precursor molecules that are used to make sex hormones.

Question 11

What does the adrenal medulla secrete?

Answer 11

Adrenaline and noradrenaline.

Question 12

What does the adrenal gland use to produce hormones?

Answer 12

-cholesterol.

Question 13

Describe the hormones produced in the adrenal gland.

Answer 13

• These hormones are steroid based and are able to enter cells directly dissolving into the cell surface membrane.
• The steroid hormones enter the nucleus and have a direct effect the DNA to cause protein synthesis.

Question 14

Summarise the action of steroid hormones.

Answer 14

1. The steroid hormone passes through the cell membrane of the target cell.
2. The steroid hormone binds with a specific receptor (complimentary shape) in the cytoplasm.
3. The receptor-steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material.
4. Binding stimulates the production of nRNA molecules, which code for the production of proteins.

Question 15

What is the role of mineralocorticoids (e.g. aldosterone) from zona glomerulosa?

Answer 15

• They help to control the concentrations of sodium and potassium in blood.
• As a result they also contribute to maintaining blood pressure.

Question 16

What does aldosterone do?

Answer 16

• Acts on cells of the distal tubules and collecting ducts in the kidneys.
• It increases absorption of sodium ions…
• decreases absorption of potassium ions and…
• increases water retention so…
• increasing blood pressure.

Question 17

What is the role of glucocorticoids (e.g. cortisol) from zona fasciculata?

Answer 17

-Help to control the metabolism of carbohydrates, fats and proteins in the liver.

Question 18

When is cortisol released and what does it do?

Answer 18

• Cortisol is released in response to stress or as a result of low blood glucose concentration.
• It stimulates the production of glucose from stored compounds (especially glycogen, fats and proteins) in the liver.

Question 19

Where else can cortisol also be released from?

Answer 19

-Zona reticularis

Question 20

If the correct enzymes are not present for the zona reticularis to release cortisol, what happens?

Answer 20

• The zona reticularis releases precursor androgens into the blood.
• These are taken up by the ovaries or testes and converted into sex hormones (e.g. testosterone and oestrogen)
• The sex hormones help development of the secondary sexual characteristics and regulate production of gametes.

Question 21

What is adrenaline (as a molecule) and how does it affect its activity?

Answer 21

• A polar molecule derived from the amino acid tyrosine.
• so cannot enter cells through the plasma membrane like a steroid hormone can.
• must be detected by specialised receptors on the plasma membrane of target cells.

Question 22

Why is the effect of adrenaline widespread?

Answer 22

Many cells and tissues have adrenaline receptors.

Question 23

What is the role of adrenaline?

Answer 23

To prepare the body for activity.

Question 24

What are the effects of adrenaline?

Answer 24

• Relaxing smooth muscle in the bronchioles.
• Increasing stroke volume of the heart.
• Increases heart rate.
• Causing general vasoconstriction to increase blood pressure.
• Stimulating conversion of glycogen to glucose.
• Dilating pupils.
• Increasing mental awareness.
• Inhibiting action of the gut.
• Causing body hair to stand erect.