Endocrine control review

Question 1

Define a hormone?

Answer 1

Blood borne chemical mediator released from endocrine glands that act on distant cells

Question 2

Describe the major differences between the nervous system and the endocrine system?

Answer 2

Question 3

How many hormones can be produced by one endocrine gland?

How many glands can one hormone be produced by?

Answer 3

Glands may produce multiple hormones

Multiple glands may produce one hormone

Question 4

What is a neurohormone?

What are the three major groups?

Answer 4

A neurocrine secreted into the bloodstream

3 major groups:

Hypothalamus > anterior pituitary

Hypothalamus > posterior pituitary

Catecholamines

Question 5

What is the difference between tropic and trophic hormones?

Answer 5

Tropic hormones control the secretion of another hormone

Trophic hormones stimulate growth and development

Question 6

How are tropic hormones usually named?

Answer 6

Usually have names that end in ‘tropin’

Question 7

Describe the different ways by which hormones can be classified?

Answer 7

Source of hormone

Hormone structure (peptide, amine, steroidP

Hormone solubility (hydrophilic or lipophilic)

Binding of receptor type

Question 8

Describe the differences between peptide, steroid and amine hormones?

Answer 8

Question 9

Describe the difference in synthesis and storage between peptide, steroid and amine hormones?

Answer 9

Peptide: made in advance, stored in secretory vesicles

Steroid: synthesised on demand from precursors

Catecholamines: made in advance, stored in secretory vesicles

Thyroid hormones: made in advance, precursor stored in secretory vesicles

Question 10

Describe the difference in release mechanism between peptide, steroid and amine hormones?

Describe the reason for each mechanism.

Answer 10

Peptide: exocytosis (lipophobic)

Steroid: simple diffusion (lipophilic)

Catecholamines: exocytosis (lipophobic)

Thyroid hormones: simple diffusion (lipophilic)

Question 11

Describe the difference in transport in the blood between peptide, steroid and amine hormones?

Answer 11

Peptide: dissolved in plasma

Steroid: bound to carrier proteins

Catecholamines: dissolved in plasma

Thyroid hormones: bound to carrier proteins

Question 12

Describe the half-lives of peptide, steroid and amine hormones?

Answer 12

Peptide: short

Steroid: long

Catecholamines: short

Thyroid hormones: long

Question 13

Describe the location of receptors for peptide, steroid and amine hormones?

Explain the reason for each.

Answer 13

Peptide: cell membrane (lipophobic)

Steroid: cytoplasm or nucleus (lipophilic)

Catecholamines: cell membrane (lipophobic)

Thyroid hormones: nucleus (lipophilic)

Question 14

Describe the response to receptor-ligand binding in peptide, steroid and amine hormones?

Answer 14

Peptide: activation of second messenger systems (membrane receptor)

Steroid: activation of genes for transcription and translation (cytoplasmic/nuclear receptors)

Catecholamines: activation of second messenger systems (membrane receptor)

Thyroid hormones: activation of genes for transcription and translation (nuclear receptors)

Question 15

Give examples of peptide, steroid and amine hormones?

Answer 15

Peptide: insulin, PTH

Steroid: oestrogen, cortisol

Catecholamine: adrenaline, noradrenaline

Thyroid hormones: thyroxine

Question 16

Briefly describe the process of peptide hormone synthesis?

Answer 16

Preprohormone synthesised by ribosomes > ER lumen > cleaved to prohormone > Golgi complex > secretory vesicles with prohormone formed > enzymes cleave into active hormone > exocytosis

Question 17

What is the parent compound for all steroid hormones?

Answer 17

Cholesterol

Question 18

Describe the action of steroid and thyroid hormones after receptor binding?

Answer 18

Alter gene expression and produce new proteins

Question 19

Describe the influences on plasma hormone concentration?

Answer 19

Rate of secretion by endocrine gland

Rate of metabolic activation

Extent of binding to plasma proteins

Rate of metabolic inactivation and excretion

Question 20

Describe the different mechanisms of hormone removal?

Answer 20

Steroid: conjugation > urine and bile

Amines: circulating degrading enzymes

Large peptides: receptor-mediated endocytosis

Small peptides: kidneys

Question 21

Describe the different mechanisms of regulation of hormones secretion?

Answer 21

Negative feedback systems: long loops and short loops

Positive feedback systems

Neuroendocrine reflexes

Diurnal and circadian rhythms

Question 22

How is regulation of cortisol release achieved?

Answer 22

According to diurnal and circadian rhythm

Question 23

Describe permissive regulation of hormone secretion?

Answer 23

First hormone cannot exert its effects without presence of second hormone

eg. cortisol and adrenaline

Question 24

Describe the difference between a primary and secondary endocrine disorder?

Answer 24

Primary: abnormal endocrine gland

Secondary: normal endocrine gland, something wrong elsewhere in pathway

Question 25

List some possible causes of decreased or increased hormone activity?

Answer 25

DECREASED: hyposecretion, increased removal from blood, lack of receptors, lack of enzyme for cell response

INCREASED: hypersecretion, decreased plasma protein binding, dcreased removal from blood

Question 26

Describe the general approach to treatment for decreased and increased hormone activity?

Answer 26

Decreased: hormone administration

Increased: tumour removal, inhbiting drugs