Physiology

Question 1

What are the determinants of the specificity of hormone action?

Answer 1

1. structure of the hormone molecule
2. hormone-specific receptor structure
3. distribution of hormone receptors

Question 2

What are the 4 classes of endocrine hormones?

Give examples of each.

Answer 2

1. Modified amino acids (Adrenaline)
2. Steroids (Cortisol)
3. Peptides (ADH)
4. Proteins (Isulin)

Question 3

Define autocrine signalling.

Answer 3

The cell secreting the hormone is also its target

Question 4

Define paracrine signalling.

Answer 4

Hormones secreted by a cell target cells in its vicinity

-do not enter circulation

Question 5

Define endocrine signalling.

Answer 5

Hormones secreted by a cell enter the bloodstream to reach target tissues systemically

Question 6

How is hormonal action terminated?

Answer 6

By enzymatic inactivation of the hormone molecules (in the liver or action site)

Question 7

Amine hormones (such as Adrenaline) tend to be pre-synthesised and released ‘on demand’ in response to a particular signal (T/F)

Answer 7

True

Question 8

How are Peptide and Protein hormones stored?

Answer 8

As long precursor proteins, which are cleaved and released in response to a signal
-Ca2+ dependent exocytosis

Question 9

What is the common intermediate in all steroid hormone biosynthetic pathways? What is it formed from?

Answer 9

Pregnenolone

Formed from cholesterol
-rate limiting step

Question 10

How are steroids transported in blood?

Answer 10

Bound to plasma proteins

Question 11

Only protein-bound steroid hormones are biologically active (T/F)

Answer 11

False

-only FREE steroids are active

Question 12

What are the functions of the hormone carrying proteins?

Answer 12

1. increase amount of hormone transported in blood
2. provide a hormone reservoir and buffer
3. extend hormone half-life in the blood

Question 13

What carrier binds cortisol specifically?

Answer 13

cortisol-binding globulin

Question 14

What carrier specifically binds thyroxine (T4)?

Answer 14

thyroxine-binding globulin

Question 15

What carrier protein binds testosterone specifically?

Answer 15

sex steroid-binding globulin

Question 16

Name two important non-specific carrier proteins.

Answer 16

Albumin

Transthyretin

Question 17

Hormones must be in the free / unbound form to cross the capillary wall to activate receptors in target tissues (T/F)

Answer 17

True

Question 18

What mechanisms account for the Diurnal variation in cortisol levels?

Answer 18

…

something to do with day/night light changes

Question 19

Which hormone receptors are found at the target cells surface? What hormones bind to them?

Answer 19

G-protein coupled receptors

Receptor kinases

-amines, peptides and proteins

Question 20

Intracellular receptors bind lipophobic hormones (T/F)

Answer 20

False

-lipophilic hormones, which can diffuse across the plasma membrane

Question 21

What are the 3 classes of nuclear hormone receptors?

Answer 21

Class 1 - activated by steroid hormones
-move from cytoplasm into nucleus upon activation

Class 2 - activated by lipids
-constitutively present in nucleus

hybrid class - activated by thyroid horome (T3)

Question 22

What happens at Receptor Kinases upon hormone binding?

Answer 22

1. Autophosphorylation of intracellular tyrosine receptor residues
2. Phosphorylation of adapter proteins’ tyrosine residues

Question 23

What type of receptor is the insulin receptor?

Answer 23

Tyrosine kinase receptor

Question 24

What type of receptor binds the Growth Hormone?

Answer 24

Cytokine receptor linked to tyrosine kinase activity

Question 25

Where are steroid hormone receptors located?

Answer 25

In the nucleus

Question 26

Which pituitary hormones are essential for survival?

Answer 26

Cortisol

Thyroid hormones

Question 27

When do Cortisol levels peak?

Answer 27

8am

-close to zero at 24:00

Question 28

What are the hypothalamic gonadal hormones?

Answer 28

LH

FSH

Question 29

Where is prolactin produced?

Answer 29

anterior pituitary

-lactrotroph cells

Question 30

What is the most common cause of primary adrenal failure, resulting in insufficient Cortisol production?

Answer 30

Addison’s disease

Question 31

What is the most common cause of excess Cortisol production?

Answer 31

Cushing’s syndrome

Cushing’s disease