Describe How Hormones Are Transported, How They Act On Cells And How Hormones Secretion Is Controlled.

Question 1

Explain anti-diuretic hormone & body fluid homeostasis

Answer 1

High blood osmolality ( body needs to conserve water ) → detected by osmorereceptors (does two things):
1. → makes you thirsty → drinking reduces osmolality
2. → posterior pituitary secreted more ADH → increased reabsorption of water from urine into blood in collecting duct in the kidney→ small volume of concentrated urine

Low blood osmolality ( body needs to excrete water ) → detected by osmoreceptors in hypothalamus → posterior pituitary secretes less ADH → decreased reabsorption of water from urine into blood in collecting ducts in the kidney → large volume of dilute urine

Question 2

How are hormones transported?

Answer 2

Some hormones travel in blood in simple solution
- peptides
- adrenaline

Most hormones must bind to (usually) proteins

Often specific proteins
- thyroid hormones ( thyroxine-binding globulin )

Dynamic equilibrium between bound and free forms of hormone in plasma.

Free hormone + binding protein →
Bound hormone

Question 3

What is the role of carrier proteins?

Answer 3

1. Increase solubility of hormone in plasma
2. Increase half life
3. Readily accessible reserve

Question 4

What are the 3 factors that determine hormone levels in blood?
Describe what those factors do?

Answer 4

1. Rate of production:
   Synthesis & secretion, the most highly regulated aspect of hormonal control.
2. Rate of delivery:
   Higher blood flow to a particular organ will deliver more hormone.
3. Rate of degradation:
   Hormones are metabolised and excretion from the body.

Question 5

Why can’t hormones effect any cell In the body?

Answer 5

Hormones can only affect cells with receptors that allow the hormone to bind.

Question 6

How do water soluble hormones move across a plasma membrane?

Answer 6

They cannot move across without binding to a cell surface receptors. This then activates intracellular signalling pathways that affect cellular function.

Question 7

How do lipid soluble hormones bind to intracellular receptors?

Answer 7

Lipid soul blue hormones diffuse across plasma membrane.

Once in the cell, there are two types of receptors:
Type 1: cytoplasmic receptors bind hormone and receptors hormone complex enters nucleus & bind to DNA.

Type 2: hormone enter nucleus and bind to pre-bound receptors on DNA e.g thyroid hormone. Binding relieves repression of gene transcription.