The Endocrine System

Question 1

Describe endocrine hormones?

Answer 1

Secreted by endocrine glands into the blood stream where they affect other organs

Question 2

Describe paracrine hormones?

Answer 2

Secreted and acts on neighbouring cell via diffusion (i.e. neurotransmitters)

Question 3

Descibe autocrine signalling?

Answer 3

The cell secretes something that it has receptors for so it will act on itself

Question 4

How can the hormone be secreted into the blood but not affect everything?

Answer 4

Must it must bind with specific receptors on the cell surface or inside the cell in order to have its effect

Question 5

Can one endocrine gland only secrete one type of hormone? Give an example

Answer 5

No as for example the pancreas secretes insulin and glucagon

Question 6

How many different hormones can a single cell secrete - what is the exception?

Answer 6

One cell secretes one hormone except for nerve cells

Question 7

Can one type of hormone only be secreted by one endocrine gland? Give an example

Answer 7

No for example somatostatin is secreted by the pancreas and the hypothalamus

Question 8

How are peptide hormones synthesised?

Answer 8

From amino acids in cells

Question 9

How are steroid hormones synthesised?

Answer 9

From precursors in the cell

Question 10

What are the two factors that affect the concentration of hormones in the blood?

Answer 10

1. Rate of Secretion

2. Rate of Inactivation/Excretion

Question 11

How are hormones usually removed from the blood?

Answer 11

By the kidneys and the liver

Question 12

What does the rate of removal depend on?

Answer 12

Whether they are long or short acting

Question 13

How are peptide hormones bound to receptors normally inactivated?

Answer 13

By endocytosis where the cell turns the hormone inward to be metabolised

Question 14

What are steroid and thyroid hormones bound to?

Answer 14

Proteins (the plasma)

Question 15

Why do steroid and thyroid hormones have a longer circulation time?

Answer 15

Because of their protein binding proteins means they are released slowly

Question 16

Where are receptors for peptide and catecholamine hormones?

Answer 16

On the cell surface (GPCRs)

Question 17

Where are the receptors for steroid and thyroid hormones?

Answer 17

In the cell (nuclear receptors)

Question 18

What is down regulation?

Answer 18

When a high concentration of the hormone is around for a long time and the total number of receptors for that hormone decreases

Question 19

What is an example of downregulation?

Answer 19

High levels of insulin being around leads to down regulation of receptors for it which leads to type 2 diabetes

Question 20

What is upregulation?

Answer 20

Occurs when cells are left for a long period of time without the hormone or low concentrations of it so more receptors are snthesised

Question 21

What is long loop feedback?

Answer 21

Where hormones have negative feedback on the anterior pituitary (directly) and the hypothalamus (indirectly) to inhibit their production

Question 22

What is short loop feedback?

Answer 22

The anterior pituitary hormones negatively feedback to the hypothalamus

Question 23

What is ultrashort loop feefback?

Answer 23

Where the hypothalamic hormones feedback on themselves by attaching to hypothalamic receptors to inhibit their release

Question 24

When would short loop feedback be seen?

Answer 24

Only in cases where the target organ isnt there anymore

Question 25

What is an example of long loop feedback not working?

Answer 25

Large concentration of gonadotrophins in post menopausal woman with no feedback

Question 26

Give an example of thyroid hormones participating in long loop feedback?

Answer 26

The thyroid hormones (T3, T4) act directly on the anterior pituatary and indirectly on the hyporthalamus to inhibit their production

Question 27

Give an of example of TSH in short loop feedback?

Answer 27

The thyroid stimulating hormone (thyrotrophin) is released from the anterior pituitary and acts on the hypothalamus to inhibit its release

Question 28

Give an example of TRH in ultra short loop feedback?

Answer 28

The hypothalamus releases thryotrophin release hormone which acts on the receptors on the hypothalamus to inibit its release

Question 29

What is an example of positive feedback?

Answer 29

Oestrogen acting on the anterior pituitary and the