Lecture 12 - The Endocrine System

Question 1

Why is it important to take into account the time of day samples are taken of melatonin and cortisol?

Answer 1

Their levels change throughout the day

Question 2

Describe the negative feedback loop of thyroid release

Answer 2

Hypothalamus releases TRH -> TSH release from anterior pituitary -> thyroid gland releases T3 And T4 - note there are several levels of inhibition on this - long loop, short loop and ultrashort loop

Question 3

Give a biological example of positive feedback

Answer 3

Blood clotting/ovulation

Question 4

What percentage of TBW is intracellular fluid?

Answer 4

2/3 / 66.666%

Question 5

What is an osmole?

Answer 5

The amount of substance that dissociates in solution to form one mole of osmotically active particles
E.g. 1mMol solution of NaCl has an osmolarity of 2mOsm/L

Question 6

Give a physiological state in which it is useful to look at serum osmolality

Answer 6

Hyponatraemia (low sodium in the blood)

Question 7

What hormone would be released following a detection of high blood osmolality by the osmoceptors in the hypothalamus?

Answer 7

ADH -> increases water reabsorption in kidney CCD. Also thirst is triggered

Question 8

What is down by the body to compensate for a low blood osmolality

Answer 8

Decreased in ADH secretion

Question 9

Where is ADH released from?

Answer 9

Posterior pituitary gland

Question 10

Above what plasma glucose level do mechanisms start working to bring it back down?

Answer 10

5mM

Question 11

Insulin is released from beta cells of the islets of langerhans in the pancreas in response to elevated blood glucose. What two things does insulin have an effect on to bring it back down to the normal level?

Answer 11

Stimulates glyogenesis in the liver

Stimulates glucose uptake in the muscle and adipose tissue via upregulating glut4

Question 12

How does glucagon bring plasma glucose levels back up

Answer 12

Stimulates glycogenolysis in the liver

Question 13

What is a hormone?

Answer 13

A chemical signal produced in endocrine glands that travels in the bloodstream and acts on distant tissues

Question 14

What key hormone involved in setting the biological clock is secreted from the pineal gland?

Answer 14

Melatonin

Question 15

Explain Neurocrine signalling

Answer 15

Hormone originated in neutron and after transport down axon is released into bloodstream and acts on distant cells

Question 16

Which types of signals produce a more rapid response - lipid soluble or water soluble hormones?

Answer 16

Water soluble. Explanation - they act on cell surface receptors whereas lipid soluble work on intracellular ones which have a longer pathway involving transcription

Question 17

List the 4 major classes of hormones and whether they’re water or lipid soluble

Answer 17

Polypeptides - water soluble
Glycoproteins - water soluble
Amines - adrenal medulla ones are water soluble, thyroid hormones are lipid soluble
Steroid hormones - lipid soluble

Question 18

What is the precursor of the steroid hormones?

Answer 18

Cholesterol

Question 19

Do hormones in the blood circulate at

a) millimolar conc
b) molar conc
c) picomolar conc

Answer 19

c

Question 20

What 3 main factors determine the level of hormone in the blood

Answer 20

Rate of synthesis
Rate of delivery
Rate of degradation.

Question 21

Water soluble hormones bind cell surface receptors which initiate a response via an intracellular pathway. Lipid soluble hormones bind intracellular receptors, the receptor then binds a ____ _____ ____ in the promoter region of genes. -> transcription of protein-> effect on hormone

Answer 21

Hormone response element

Question 22

Primary neurons processing information to regulate hunger exist in which nucleus in the hypothalamus?

Answer 22

Arcuate nucleus

Question 23

Which neurotransmitters are found in the following primary neurons of the arcuate nucleus

a) stimulatory
b) inhibitory

Answer 23

AgRP and NPY
Alpha MSH (from POMC)

Question 24

Hormones stimulate or inhibit the primary neurons of the arcuate nucleus which then synapse with secondary neurons in the hypothalamus thus affecting hunger. Leptin (from adipose) inhibits hunger by both stimulating the inhibitory pathway and inhibiting the stimulatory pathway. Are the following hormones stimulating or inhibiting hunger?

a) ghrelin (from stomach)
b) PYY (from small intestine)
c) insulin (from pancreas)

Answer 24

a) stimulating
b) inhibiting
c) inhibiting

Question 25

which pathway goes towards the control centre and which pathway goes away?

Answer 25

Afferent to control centre

Efferent away from control centre

Question 26

Give two examples of biological rhythms

Answer 26

Cortisol/melatonin/feeding/body temperature

Question 27

Are the following at their highest levels in the morning or in the night?

a) body temperature
b) cortisol
c) melatonin

Answer 27

a) evening
b) morning
c) night

Question 28

Carrier proteins are sometimes used to deliver hormones, apart from increasing the solubility of the hormone, what other roles do they play in regards to the hormone they carry.

Answer 28

Increase the half-life of the hormone

Provide a readily accessible reserve of the hormone (as only free hormone is biologically active)

Question 29

A BMI of above what is considered obese/

Answer 29

30kg/msquared

Question 30

define the term hormone

Answer 30

Hormones are chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues.

Question 31

Name the polypeptide precuror to the inhibitory NT’s alpha-MSH and B-endorphin which promote satiety (inhibition of feeding)

Answer 31

POMC

Question 32

Give an example of each class of hormone

Answer 32

peptide (water solube)- Insulin/glucagon/growth hormone
Amine (water soluble) - Adrenaline, NA,
Amine (lipid soluble) - thyroid hormones
Glycoprotein (water soluble) - LH/FSH/TSH
Steroid (lipid solube) - cortisol, aldosterone, testosterone