L12: Endocrine Intro

Question 1

Negative feedback is described to have ‘hunting behaviour’; what does this mean?

Answer 1

Tends to overshoot the set point until the set point is reached

Question 2

Give an example of negative feedback

Answer 2

• Temperature control
• Hyperglycaemia and insulin release

Question 3

Give an example of positive feedback

Answer 3

• Blood clotting
• Ovulation

Question 4

Are set points fixed at a certain value?

Answer 4

No they can vary over time giving rise to biologcial rhythms

Question 5

Describe what circadian (dinural) rhythm is

Answer 5

Roughly 24 hour cycel which has patterns of physical, mental and behavioural changes that are controlled by biological clock

Question 6

What part of body is the biological clock?

What is it triggered by?

What hormone, and from what gland, is involved in setting the biological clock?

Answer 6

• Superchiasmatic nucleus
• Triggered by cues in the environment (zeitgebers) e.g. light, temp, exercise, eating…
• Melatonin from pineal gland

Question 7

Give some examples of biological rhythms- state when each is high and low

Answer 7

• Core body temp
• Cortisol
• Melatonin

Question 8

What is the endocrine system?

Answer 8

Collection of glands throughout body that secrete hormones (NOTE: organs also secrete important hormones)

Question 9

State an important hormone secreted by each of following organs:

• Heart
• Liver
• Stomach
• Adipose
• Kidney

Answer 9

• Heart: ANP, BNP
• Liver: IGF1
• Stomach: gastrin, grehlin
• Adipose: leptin
• Kidney: erythropoietin, renin, calcitriol

Question 10

Is the concentration of hormones in blood low or high?

Answer 10

Very low (x10^-10- x10^-9)

Question 11

Describe each of the types of signalling:

• Autocrine
• Paracrine
• Endocrine
• Neurocrine

Answer 11

Question 12

Endocrine and nervous system work in parallel to maintain homeostasis; compare endocrine & nervous system in terms of:

• Singal
• Nature
• Conveynace
• Mediators
• Speed

Answer 12

Question 13

What is a tropic hormone?

Answer 13

Tropic hormones have other endocrine glands as their targets

Question 14

What is a trophic hormone?

Answer 14

Stimulate growth in target tissue

Question 15

State the 4 types of hormones

Answer 15

• Peptide/polypeptide
• Glycoproteins
• Amino acid derivatives (amines)
• Steroids

Question 16

For peptide hormones, state:

• Description
• Water or lipid soluble
• Example

Answer 16

• Short or long chain of amino acids
• Water soluble
• Insulin, glucagon, GH

Question 17

For glycoprotein hormones, state:

• Description
• Water or lipid soluble
• Example

Answer 17

• Large protein molecules with carbohydrate side chains
• Water soluble
• TSH, FSH

Question 18

For amino acid derivative hormones, state:

• Description
• Water or lipid soluble
• Example

Answer 18

• Small molecules synthesised from aromatic amino acids
• Adrenal medulla hormones= water soluble
• Thyroid hormones= lipid soluble
• Adrenaline, NA, thyroxine, melatonin

Question 19

For steroid hormones, state:

• Description
• Water or lipid soluble
• Example

Answer 19

• Derived from cholesterol
• Lipid soluble
• Cortisol, aldosterone, testosterone

Question 21

What 3 factors determine hormone concentration in blood?

Answer 21

• Rate of production *MOST HIGHLY REGULATED ASPECT
• Rate of delivery
• Rate of degradation

Question 22

Hormones can sometimes be inactivated in liver and kidneys; state how steroid and peptide hormones can be degraded

Answer 22

• Steroid: change in structure to increase water solubility
• Peptide: chemical changes and degraded to amino acids which are used in protein synthesis

Question 23

Where is the appetite control centre (satiety centre)?

Which ‘nucleus’ plays a role in controlling appetite?

Answer 23

• Hypothalamus
• Several clusters of neurones referred to as nuclei; arucate nucleus plays role in controlling appetite

Question 24

Neuronal nutrient and hormonal signals are processed by primary neurones in arcuate nucleus (which has role in satiety centre); state the two types of primary neurones

Answer 24

• Stimulatory (orexigenic)
• Inhibitory (anorexigenic)

Question 25

What do stimulatory primary neurones in arcuate nucleus release?

Answer 25

* Neuropeptide Y (NPY) * Agouti-related peptide (AgRP) ... both promote hunger

Question 26

What do inhibitory (anorexigenic) primary neurones in arcuate nucleus secrete?

Answer 26

* Release POMC (proopiomelanocortin) which is a polypeptide that can be cleaved into: * alpha-MSH * B-endorphin ... both promote satiety

Question 27

Priamry neruones in arcuate nucleus synapse with....

Answer 27

Secondary neurones in other regions of hypothalamus to alter feeding behaviour

Question 28

State 2 hormones that are **released from gut and send signals to hypothalamus** in control of appetite

Answer 28

* Grehlin * PYY (peptide tyrosine tyrosine)

Question 29

State 3 hormones that are released from body and send signals to hypothalamus in control of appetite

Answer 29

* Leptin (from adipose cells) * Insulin (from pancreas) * Amylin (from pancreas)

Question 30

State the effect of each of the following on appetite: * Grehlin * PYY * Leptin * Insulin * Amylin

Answer 30

* Grehlin: stimulate * Others: supress

Question 31

For hormone grehlin, state: * Where released from and when * Effect on arcuate nucleus * Effect on appetite

Answer 31

* Released from stomach wall when empty * Stimulate excitatory neurones * Stimulate appetite ## Footnote *\*Filling of stomach inhibits grehlin release*

Question 32

For hormone PYY, state: * Where it is released from and when * Effect on arcutate nucleus * Effect on appetite

Answer 32

* Cells in ileum and colon in response to feeding * Inhibits excitatory, stimulates inhibitory * Supress appetite

Question 33

For hormone leptine, state: * Where it is released from * Effect on arcuate nucleus * Effect on appetite

Answer 33

* Released from adipose cells * Inhibits excitatory neurones, stimulates inhibitory * Supress appetite

Question 34

For hormone insulin, state: * Where released from and when * Effect on arcuate nucleus * Effect on appetite

Answer 34

* B-islet cells in pancreas in response to hyperglycaemia * Inhibits excitatory, stimulate inhibitory * Supress appetite

Question 35

For hormone amylin, state: * Where released from * Effects? * Effect on appetite

Answer 35

* Released from B-islet cells in pancreas * Role not fully understood (thought to decrease glucagon secretion and slow gastric emptying) * Supress appetite

Question 36

Can leptin help patients with excess hunger?

Answer 36

Some individuals have loss of function mutation in leptin gene which results in excess hunger; these individuals respond well to leptin injections. However, leptin injections won't work for those with common obesity as higher centres overrule leptin/leptin production is fine.