5.4 Hormones

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 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 adrenaline?

Answer 3

A hormone released from the adrenal glands, which stimulates the body to prepare for flight or flight.

Question 4

What is an adrenal medulla?

Answer 4

The inner layer of the adrenal glands.

Question 5

What are adrenal glands an example of?

Answer 5

An endocrine gland.

Question 6

Where are adrenal glands found?

Answer 6

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

Question 7

What is each adrenal gland divided into?

Answer 7

• the outer adrenal cortex
• the inner adrenal medulla

Both regions are well supplied with blood vessels and produce hormones which are secreted directly into the blood vessels.

Question 8

The adrenal cortex has an outer capsule surrounding which three distinct layers of cells?

Answer 8

• zona glomerulosa - the outermost layer, which secretes mineralocorticoids such as aldosterone.
• zona fasciculata - the middle layer, which secretes glucocorticoids such as cortisol.
• zona reticularis - the innermost layer, which is thought to secrete precursor molecules that are used to make sex hormones.

Question 9

What does the adrenal medulla secrete?

Answer 9

Adrenaline and noradrenaline.

Question 10

What type of hormones are produced by the adrenal cortex?

Answer 10

The adrenal cortex uses cholesterol to produce a range of hormones which are steroid based and soluble in lipids.

Question 11

Summarise the action of steroid hormones.

Answer 11

1. The steroid hormone passes through the cell membrane of the target cell.
2. The steroid hormone binds to a specific receptor (with a complementary 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 MRNA molecules, which code for the production of proteins.

Question 12

What roles do mineralocorticoids have?

Answer 12

E.g. aldosterone, from the zona glomerulosa - help to control the concentrations of sodium and potassium in the blood. As a result, they also contribute to maintaining blood pressure. Aldosterone acts on the cells of the distal tubules and collecting ducts in the kidney. It increases water retention so increasing blood pressure.

Question 13

What roles do Glucocorticoids have in the body?

Answer 13

• (e.g. cortisol) from the zona fasciculata - help to control the metabolism of carbohydrates, fats and proteins in the liver. 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 14

How may the adrenal complex cause sex hormones to be produced?

Answer 14

• Cortisol may also be released by the zona reticularis. However, if the correct enzymes are not present for the release of cortisol, then the zona reticularis releases precursor androgens into the blood. These are take up by the ovaries or testis and converted to sex hormones (e.g. testosterone in males and oestrogen in females). The sex hormones help the development of the secondary sexual characteristics and regulate the production of gametes.

Question 15

Where is adrenaline released?

Answer 15

From the adrenal medulla.

Question 16

How is adrenaline detected?

Answer 16

Adrenaline is a polar molecule derived from the amino acid tyrosine. This means that it cannot enter cells through the plasma membrane like a steroid hormone can. Therefore, it must be detected by specialised receptors on the plasma membrane of the target cells.

Question 17

Why are the effects of insulin widespread?

Answer 17

Many cells have adrenaline receptors.

Question 18

What is the role of adrenaline in the body?

Answer 18

• Relaxing smooth muscle in the bronchioles
• increasing stroke volume of the heart
• increasing heart rate
• causing general vasoconstriction to raise blood pressure
• stimulating conversion of glycogen to glucose
• increasing mental awareness
• inhibiting the action of the gut
• causing body hair to stand erect.

Question 19

What are beta cells?

Answer 19

Cells found in the islets of langerhans that secrete the hormone insulin.

Question 20

What is glucagon?

Answer 20

a hormone that causes an increase in blood glucose concentration.

Question 21

What is insulin?

Answer 21

the hormone, released from the pancreas, that causes blood glucose levels to go down.

Question 22

What hormone releasing functions does the pancreas have?

Answer 22

The pancreas is a small organ lying just beloe the stomach, and has both exocrine and endocrine functions.

Question 23

What are the two main secrretions of the pancreas?

Answer 23

1. Pancreatic juices containing enzymes which are secreted into the small intestine.
2. Hormones which are secreted from the islets of Langerhans into the blood.

Question 24

What would be found in a section of the pancreas viewed under the miscroscope?

Answer 24

Question 25

Describe the endocrine function of the pancreas.

Answer 25

Endocrine glands sectrete substances into a duct. Most cells in then pancreas synthesise and release digestive enzymes. This is the exocrine function of the pancreas. The exocrine cells are in small groups surrounding tiny tubules.

Question 26

Describe the exocrine cells in the pancreas.

Answer 26

The exocrine cells are in small groups surrounding tiny tubules. Each group of cells is called an acrinus (plural acini). The acini are grouped togther into small lobules separated by connnective tissues.

Question 27

What is the job of the cells of acini?

Answer 27

The cells of the acini secrete the enzymes they synthesise into the tubule at the centre of the group.

Question 28

Descrine a pancreatic duct.

Answer 28

The tubules from the acini join to form intralobular ducts that eventually combine to ake up the pancreatic duct. The pancreatic duct carries the fluid containing the enzymes into the first part of the intestine (duodenum).

Question 29

What does the fluid from the pancreatic duct contain?

Answer 29

• pancreatic amylase - carbohydrates which digest amylose to maltose
• trypsinogen - an inactive protease which will be converted to the active from trypsin when it eneters the duodenum
• lipase - which digests lipid molecules.