Hormonal communication

Question 1

Hormones bind to receptors and trigger secondary messengers example?

Answer 1

• The hormone adrenaline is the first messenger.
• It binds to specific receptors in the cell membranes of many cells, e.g. liver cells.
• When adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase.
• Activated adenylyl cyclase catalyses the production of the secondary messenger called cyclic AMP (cAMP) from ATP.
• cAMP activated a cascade , e.g. a cascade of enzyme reactions make more glucose available to the cell by catalysing the breakdown of glycogen into glucose.

Question 2

Where are the adrenaline glands?

Answer 2

Just above the kidneys.

Question 3

Adrenal gland: What does the cortex do?

Answer 3

The cortex secretes steroid hormones, e.g. it secretes cortisol and aldosterone when you’re stressed. These hormones have a role in both the short-term and long-term response to stress.

Question 4

Adrenal gland: Effects of the hormones the cortex secretes?

Answer 4

• Stimulating the breakdown of proteins and fats into glucose. This increase the amount of energy available so the brain and muscles can respond to the situation.
• Increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys.
• Supressing the immune system.

Question 5

Adrenal gland: What does the medulla do?

Answer 5

The medulla secretes catecholamine hormones (modified amino acids), e.g. it secretes adrenaline and noradrenaline when you’re stressed. These act to make more energy available in the short-term.

Question 6

Adrenal gland: Effects of the hormones the medulla secretes?

Answer 6

• Increase heart and breathing rate
• Causing cells to break down glycogen into glucose
• Constricting some blood vessels so that blood is diverted to the brain and muscles.