homeostasis & the endocrine system

Question 1

What is the body’s 24 hour clock?

Answer 1

circadian rhythm - can vary throughout the day

Question 2

What is the body’s biological clock - where is it?

Answer 2

suprachiasmatic nucleus of the brain (neurones)

Question 3

What are zeitgebers? examples?

Answer 3

cues from the environment - keeps circadian rhythm e.g. light, temp, social interactions, exercise, eating / drinking

disrupted in jetlag

Question 4

which hormone is involved in setting body clock?

Answer 4

melatonin hormone in pineal gland of brain

Question 5

List the classes of hormones

Answer 5

1. peptide (largest) e.g. insulin
2. glycoprotein e.g. LH, FSH, TSH
3. amide (AA derivative) e.g. adrenaline & noradrenaline
4. steroid (from cholesterol) - fat soluble e.g. cortisol & testosterone

Question 6

Main features of body control systems

Answer 6

stimulus, receptor, afferent pathway, control centre (CNS), efferent pathway, effector

Question 7

How does tyrosine kinase work? what’s an example of a hormone which uses this process?

Answer 7

1. dimerisation (combine 2 identical molecules)
2. autophosphorylation to the tyrosine
3. proteins etc. bind to the phosphorylated tyrosines
4. further activating protein kinase e.g. PKB to phosphorylate target proteins for cellular response

Question 8

What does lipid soluble hormone bind to?

Answer 8

receptors then HRE (hormone response element) on DNA in nucleus too affect gene transcription, affecting expression of protein causing cellular response

Question 9

Neurocrine function of posterior pituitary gland

give examples of hormones which are released like this

Answer 9

produced in hypothalamus by neurones e.g. oxytocin & ADH
travel down through nerve cell axons to posterior pituitary
stored & released from posterior pituitary to distant target cells

Question 10

anterior pituitary funcion

Answer 10

hormones made in hypothalamus
stored in median eminence of hypothalamus
released into hypophyseal portal system to anterior pituitary
hormones stimulate / inhibit the target endocrine cells of anterior pituitary gland (neurocrine function)
endocrine cells of pituitary gland then release hormones into bloodstream to distant target cells
anterior pituitary hormone also has autocrine & paracrine functions

Question 11

give an example of the anterior pituitary gland function using the hormone cortisol

Answer 11

stimulus –> hypothalamus –> CRH –> anterior pituitary gland –> ACTH –> adrenal cortex –> cortisol (negative feedback to inhibit hypothalamus & anterior pituitary gland)

Question 12

What are the modes of effect of hormones?

Answer 12

autocrine - self affecting
paracrine - affects neighbours
neurocrine - neuron to axon to bloocstream
endocrine - distant target cells - bloodstream