Endocrinology Introduction and Overview

Question 1

What is the difference between the nervous system and the endocrine system?

Answer 1

signals of neurons in the nervous system are precisely targeted, whereas, signals produced by the endocrine system are broadly distributed throughout an animal’s body

Question 2

What 3 classes can most hormones fall into?

Answer 2

1. steroid hormones
2. peptide and protein hormones
3. amine hormones

Question 3

What is the half life of steroid hormones?

Answer 3

hours

Question 4

Where are steroid hormones secreted from in vertebrates?

Answer 4

gonads, adrenal cortex and placentas(in pregnant animals)

Question 5

What feature of steroid hormones mean they can diffuse across cell membrane?

Answer 5

lipid soluble

Question 6

What is the half life of peptide and protein hormones?

Answer 6

minutes

Question 7

Where are peptide and protein hormones soluble?

Answer 7

aqueous solutions

Question 8

How are peptide and protein hormones secreted?

Answer 8

exocytosis

Question 9

What are the steps of peptide hormone synthesis?

Answer 9

1. a prepropeptide is synthesised and released into the rough ER
2. proteolytic enzymes in RER cleave off some amino acids to yield propeptides
3. in the smooth ER, propeptides are packaged into transport vesicles
4. the vesicles are transported to the golgi complexes
5. golgi complexes package the propeptide into secretory vesicles (more AAs cleaved is GA or secretory vesicles to yield final peptide)
6. the peptides are released by exocytosis

Question 10

What is the half-life of amine hormones?

Answer 10

ranges from seconds, minutes or days

Question 11

What are some differences between lipid-soluble and water-soluble hormones?

Answer 11

Lipid-soluble hormones:
- Diffuse across cell membranes
- Travel in the bloodstream bound to transport proteins
- Diffuse through the membrane of target cells

Water-soluble hormones:
- secreted by exocytosis
- travel freely in the bloodstream
- bind to cell-surface receptors

Question 12

How do steroid hormones elicit a response?

Answer 12

1. hormone interacts with receptor
2. translocates to the nucleus
3. interacts with response elements
4. produce mRNA/protein
5. biological effect

Question 13

How do protein hormones elicit a response?

Answer 13

1. hormone interacts with receptor
2. activation of adenylate
3. production of cAMP
4. protein kinase phosphorylation
5. biological effect

Question 14

What does inactivation of steroids involve?

Answer 14

Inactivation of steroids involves reductions and conjugation to glucuronides or sulfate to increase their water solubility

Question 15

How are conjugated steroids excreted?

Answer 15

• 70% are excreted in the urine
• 20% leave in faeces
• the rest leave through the skin

Question 16

Describe the negative feedback system in hormones?

Answer 16

increased hormone concentration(blood) -> less production of hormone

Question 17

What happens if blood concentrations increase beyond the physiological set point?

Answer 17

releasing hormone output is decreased

Question 18

What is the function of the hypothalamus?

Answer 18

control centre

Question 19

What does the hypothalamus monitor?

Answer 19

composition and temperature of blood

Question 20

What 2 lobes make up the pituitary gland?

Answer 20

anterior lobe and posterior lobe

Question 21

What does the hypothalamus and pituitary release?

Answer 21

• cascades of hormones that act at peripheral tissues (target organs) which in turn release hormones
• hormones released from target organs “feedback” to the hypothalamus and pituitary gland to regulate their own release