The Endocrine System

Question 1

What is the endocrine system?

Answer 1

A system which integrates and controls organs via the secretion of hormones which are carried in the blood to target organs

Question 2

What system does the endocrine system work with?

Answer 2

Nervous system

Question 3

What is endocrine communication?

Answer 3

Hormones which travel in the blood to target organs/tissues

Question 4

Where do hormones act upon?

Answer 4

Receptors.

No receptor = no response

Question 5

What occurs during Neural Communication?

Answer 5

NT’s are released from presynaptic neurons that travel across the synaptic cleft to post synaptic cleft to influence its activity. NTs released by neuron and acts locally within synaptic cleft

Question 6

What occurs when the nervous and endocrine systems combine?

Answer 6

Nerves release hormones which eter blood and travel to their target cells. Process is highly specific as only target cells have receptors for the hormone

Question 7

Define Autocrine

Answer 7

Cells that secrete chemicals that bind to receptors on the same cell

Question 8

Define Paracrine

Answer 8

Chemicals diffuse in ECF to affect neighbouring cells

Question 9

What are the features of an endocrine hormones?

Answer 9

Produced by a group of cells, secreted from those cells into the blood, Transported via the blood to distant targets, Exert their effects at very low concentrations, Act by binding to the receptors on target tissues, Have their action terminated (usually by Negative Feedback)

Question 10

What are peptide/protein hormones comprised of?

Answer 10

Chains of amino acids

Question 11

What are steroid hormones derived from?

Answer 11

Cholesterol

Question 12

What are Amine Hormones derived from?

Answer 12

Tryptophan or Tyrosine

Question 13

Give examples of Peptide Hormones

Answer 13

TRH, FSH, Insulin

Question 14

What are preprohormones?

Answer 14

Contain one or more copies of the active hormone in their amino acid sequence

Question 15

How are peptide hormones synthesised?

Answer 15

SYNTHESISED IN ADVANCED

Stored as perprohormone which are eventually cleaved into smaller units in the RER into prohormones. These are packaged into golgi apparatus, alongside proteolytic enzymes, which breakdown prohormone into an active hormone

Question 16

Where are peptide hormones stored?

Answer 16

In vesicles in endocrine cells until released into plasma

Question 17

What is C-peptide

Answer 17

The inactive fragment cleaved from insulin prohormone

Question 18

What feature of peptide hormones makes them dissolvable in plasma?

Answer 18

They are water soluble

Question 19

Where do peptide hormones bind?

Answer 19

They bind to membrane bound receptors on target cells as they cannot cross cell membrane

Question 20

What occurs when peptide hormones bind to membrane bound receptors?

Answer 20

Fast biological responses are generated via modulating either the GPCR or Tyrosine Kinase Linked signalling pathways. This results in phosphorylation of existing cellular proteins which modifies their function

Question 21

Where type of receptors do peptide hormones bind to?

Answer 21

GPCR - activated 2nd messenger systems+/ ion channels which leads to modification of existing proteins

Tyrosine Kinase Linked Receptor - Alters gene expression

Question 22

When are steroid hormones synthesised?

Answer 22

When they are needed as they are lipophilic and cannot be retained within the lipid membrane

Question 23

Why are steroid hormones bound to carrier proteins?

Answer 23

As they are poorly soluble in water which stabilises their transport through plasma from enzymatic degradation

Question 24

Where are steroid hormones produced?

Answer 24

Gonads, Placenta, Kidney, Adrenal Cortex

Question 25

Describe the action of steroid hormones

Answer 25

Steroid hormones easily cross the plasma membrane and their receptors are located inside the cells and either trigger activation or inhibition of gene function within nucleus.

Question 26

Which hormone is the only amine hormone not synthesised by tyrosine?

Answer 26

Melatonin which is derived from tryptophan

Question 27

Describe the physiological activity of lipophilic hormones

Answer 27

Only a small amount of unbound steroid/thyroid hormone in the plasma. Only free hormone can diffuse across capillary walls to target cells

Question 28

Describe the Law of Mass Action

Answer 28

As free hormone leaves the plasma, more hormone is relased by carriers

Question 29

How is total plasma hormone concentration calculated?

Answer 29

Free Hormone + Complexed Hormone

Question 30

How is hormone concentration in blood determined?

Answer 30

It is dependant on rate of secretion and removal.

Question 31

Where does hormone removal occur?

Answer 31

Kidney or liver via excretion or metabolic transformation

Question 32

What hormones are respondent to negative feedback control?

Answer 32

Parathyroid Hormone

Question 33

What hormones respond to neural feedback loops?

Answer 33

Adrenaline

Question 34

What occurs after prolonged exposure to low hormone concentration in plasma?

Answer 34

An up-regulation, Increased number of hormone receptors on target tissues which increases tissue sensitivity to hormone

Question 35

What occurs after prolonged exposure to high hormone concentration in plasma?

Answer 35

Down regulation = a decrease in receptor number on target tissues which decreases tissue sensitivity

Question 36

What is the permissive effect?

Answer 36

The presence of one hormone which enhances the effect of another hormone