Session 6-Intro To Endocrine System And Control Of Appetite

Question 1

True or false: homeostasis is a steady state

Answer 1

FALSE - dynamic equilibrium

Question 2

Which pathway communicates from receptor to control centre?

Answer 2

Afferent pathway

Question 3

Which pathway communicates from control centre to effector?

Answer 3

Efferent pathway

Question 4

Where is the circadian rhythm set up?

Answer 4

Biological clock in brain (hypothalamus) in a small group of neurones in suprachiasmatic nucleus

Question 5

Which environmental cues keep the body on a 24 hour cycle?

Answer 5

Light
Temperature
Social interaction 
Exercise 
Eating/drinking pattern

Question 6

What causes jet lag?

Answer 6

Long haul flights crossing time zones can result in mismatch between environmental cues and body clock

Question 7

Which hormone produced in the pineal gland is involved in setting the biological clock?

Answer 7

Melatonin

Question 8

What does negative feedback do?

Answer 8

Response in a way to reverse direction of change

Question 9

What is positive feedback?

Answer 9

Response in a way so as to change variable even more in direction of change

Question 10

When is positive feedback used and give examples?

Answer 10

When rapid change is desirable

Eg blood clotting and ovulation

Question 11

What monitors osmotic pressure of blood plasma?

Answer 11

Osmoreceptors in hypothalamus

Question 12

What is the difference between osmolarity and osmolality?

Answer 12

Osmolarity = number of osmoles per litre of solution

Osmolality = number of osmoles per kg of solution

Question 13

What is an osmole?

Answer 13

Amount of substance that dissociates in solution to form one mole of osmotically active particles

Question 14

When is serum osmolality useful?

Answer 14

When investigating hyponatraemia (low Na+ in blood)

Question 15

What is the normal range of blood osmolality?

Answer 15

275-295 mOsm/kg

Question 16

What happens when blood osmolality is high?

Answer 16

1) High osmolality is detected by osmoreceptors in hypothalamus
2) posterior pituitary secretes more ADH
3) increased reabsorption of water from urine into blood in collecting ducts in kidney
4) small volume of concentrated urine 5) normal blood osmolality

Question 17

What happens when blood osmolality is low?

Answer 17

1) detected by osmoreceptors in hypothalamus
2) posterior pituitary secretes less ADH
3) decreased reabsorption of water from urine into blood in collecting ducts in kidney
4) large volume of dilute urine
5) normal blood osmolality

Question 18

What happens when plasma glucose levels increase?

Answer 18

1) detected by pancreatic beta cells
2) pancreas releases insulin
3) insulin stimulates glycogenesis in liver and glucose uptake into tissues
4) plasma glucose decreases

Question 19

What happens when plasma glucose levels decrease?

Answer 19

1) detected by pancreatic alpha cells
2) pancreas releases glucagon
3) stimulates glycogenolysis in liver
4) glucose released into blood and plasma glucose increases

Question 20

What are hormones?

Answer 20

Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues

Question 21

What is autocrine communication?

Answer 21

Hormone signal acts back on cell of origin

Question 22

What is paracrine communication?

Answer 22

Hormone signal carried to adjacent cells over short distance via interstitial fluid

Question 23

What is endocrine communication?

Answer 23

Hormone signal released into bloodstream and carried to distant target cells

Question 24

What is neurocrine communication?

Answer 24

Hormone originates in neurone and after transport down axon is released into bloodstream and carried to distant target cells

Question 25

What are the similarities between endocrine and nervous systems?

Answer 25

1) both neurones and endocrine cells can secrete 2) both cells can be depolarised 3) some molecules act as both neurotransmitter and hormone 4) mechanism of action requires interaction with specific receptors in target cells 5) both work in parallel to control homeostasis

Question 26

What are the four classifications of hormones and state whether they are water or lipid soluble?

Answer 26

1) peptide/polypeptide - water soluble 2) glycoproteins - water soluble 3) amino acid derivatives - lipid soluble 4) steroids - lipid soluble

Question 27

Which hormones are peptides/polypeptides?

Answer 27

Insulin Glucagon Growth hormone

Question 28

Which hormones are amino acid derivatives?

Answer 28

Adrenaline Noradrenaline Thyroid hormones Melatonin

Question 29

Which is the most common amino acid used to synthesise amino acid derived hormones?

Answer 29

Tyrosine

Question 30

Which hormones are glycoproteins?

Answer 30

LH FSH TSH

Question 31

Which hormones are steroids?

Answer 31

Cortisol Aldosterone Testosterone

Question 32

What are steroid hormones derived from?

Answer 32

Cholesterol

Question 33

Which hormones must bind to proteins to be transported in the blood and why is this?

Answer 33

Lipid soluble because they are hydrophobic

Question 34

True or false: only the free form of a hormone is biologically active

Answer 34

TRUE

Question 35

What are the roles of carrier proteins?

Answer 35

Increase solubility of hormone in plasma Increase half-life Readily accessible reserve

Question 36

Which 3 factors determine hormone levels in blood?

Answer 36

1) rate of production 2) rate of delivery 3) rate of degradation

Question 37

True or false: hormones circulate in blood at high concentrations

Answer 37

FALSE - very low, picomolar range

Question 38

How do hormones exert their effects?

Answer 38

By binding to specific receptors

Question 39

Which receptors do water soluble hormones bind to?

Answer 39

Cell surface receptors: 1) GPCRs 2) tyrosine kinase receptors

Question 40

Which receptor doesn't require dimerisation and why is this?

Answer 40

Insulin receptor because it is already dimerised

Question 41

Which receptors do lipid soluble hormones bind to?

Answer 41

Intracellular receptors

Question 42

What are the two types of intracellular receptors?

Answer 42

Type I - cytoplasmic receptor binds hormone and receptor-hormone complex enters nucleus and binds to DNA Type II - hormone enters nucleus and binds to pre-bound receptor on DNA and this relieves repression of gene transcription

Question 43

Why do lipid soluble hormones have a slower response than water soluble hormones?

Answer 43

Because they need new protein synthesis to occur and this takes time

Question 44

Where is the appetite control centre situated?

Answer 44

Hypothalamus in clusters of neurones called arcuate nucleus

Question 45

What are the two types of primary neurones in the arcuate nucleus?

Answer 45

1) stimulatory neurones promote hunger | 2) inhibitory neurones promote satiety

Question 46

Which peptide hormone is released from the stomach wall when it is empty?

Answer 46

Ghrelin-> stimulates appetite

Question 47

Which peptide hormone is released by cells in the ileum and colon in response to feeding?

Answer 47

PYY (peptide tyrosine tyrosine) -> suppresses appetite

Question 48

Which peptide hormone is released into the blood by adipocytes?

Answer 48

Leptin -> suppresses appetite

Question 49

What are the two effects that leptin has on arcuate nucleus?

Answer 49

1) stimulates inhibitory neurones | 2) inhibits excitatory neurones

Question 50

What effect does insulin have on appetite?

Answer 50

Suppresses it

Question 51

What effect does amylin have on appetite?

Answer 51

Suppresses appetite

Question 52

Which neurotransmitters do stimulatory primary neurones contain?

Answer 52

1) neuropeptide Y (NPY) | 2) Agouti-related peptide (AgRP)

Question 53

Which neurotransmitter do inhibitory primary neurones contain and which neurotransmitters does it yield?

Answer 53

Pro-opiomelanocortin (POMC) Yields alpha-MSH and beta-endorphin