250. Introduction to endocrine

Question 1

Define the following:

Endocrine hormone
Paracrine hormone
Autocrine hormone
Exocrine hormone

Answer 1

Endocrine hormone- Travel distally to the site of synthesis, affecting all over the body

Paracrine hormone-acts locally to synthesis e.g. histamine

Autocrine hormone-act on/in the same cell e.g. cytokines

Exocrine hormone- released from exocrine glands via ducts

Question 2

What are the various means by which a hormone can travel?

Answer 2

Endocrine: Travels through blood affecting a;l cells with the appropriate receptor

Neural: Neurotransmitters release hormones across the synaptic cleft to influence the target cell

Neuroendocrine: endocrine and nervous system combine, nerves release hormones into blood.

Question 3

What are the features of an endocrine hormone?

Answer 3

Produced by a group of cells
Secreted from those cells into the blood
Transported via the blood to distant targets
Exert their affects at low concentrations
Act by binding on target tissue
Have their action terminated, often via negative feedback loops

Question 4

What are the classes of endocrine hormones?

Answer 4

Peptide or peptide hormones- composed of chains of amino acids

Amine hormones- derived from one of two amino acids

steroid hormones- derived from cholesterol

Question 5

How are peptide hormones synthesised

Answer 5

preprohormone

prohormone——> golgi apparatus

Active hormone and peptide fragment in secretory vesicle

Question 6

Discuss the mechanism of action of peptide hormones?

Answer 6

Water soluble so dissolve easily in plasma making transport via the blood simple and easy.

Create fast biological response. (e.g. open or close ion channels)

Question 7

Provide some examples of amine hormones?

Answer 7

Dopamine, norpinepherine, epinepherine, throoxine, T3
All derived from tyrosine^^

Melatonin derived from tryptophan

Question 8

Describe the production and action of steroid hormones?

Answer 8

Lipids derived from cholesterol so are very lipophillic. Once released diffuse through membranes very quickly and have very short half lives

Transported in proteins such as albumin which stabilises these hormones and increases their half life

Question 9

Give some examples of steroid hormones and where they are produced?

Answer 9

Gonads- sex steroids
Placenta- HCG, sex steroids
Kidney- vitamin D3
Adrenal cortex- corticosteroids

Question 10

Explain the mechanisms of action of steroid hormones?

Answer 10

Slow progress between hormone release and biological effect but effects persist for around the same time.

Slow time for action, last for long time

Question 11

Summarise peptide and amine (catecheloamine) hormones

Answer 11

Water soluble, transported in solution in plasma
Vulnerable to degradation
Have short half life in the plasma
Prolonged action, requires continued secretion

Question 12

Summarise steroid and thyroid hormones?

Answer 12

Lipophilic
Circulate in the plasma in transport plasma proteins
Alter protein synthesis via modyfying gene expression

Question 13

What is meant by the permissive effects of hormones?

Answer 13

Under normal circumstances thyroid hormne does not increase lipolysis. Epinepherine causes a small amount of lipolysis.

but in tandemn thyroid hormone increases epinepherine receptor number and causes greater lipolysis

Question 14

How may hormones have antagonistic effects?

Answer 14

Presence of one hormone reduces other. E.g. growth hormone impairs insulin response