Session 6-Intro To Endocrine System And Control Of Appetite Flashcards
True or false: homeostasis is a steady state
FALSE - dynamic equilibrium
Which pathway communicates from receptor to control centre?
Afferent pathway
Which pathway communicates from control centre to effector?
Efferent pathway
Where is the circadian rhythm set up?
Biological clock in brain (hypothalamus) in a small group of neurones in suprachiasmatic nucleus
Which environmental cues keep the body on a 24 hour cycle?
Light Temperature Social interaction Exercise Eating/drinking pattern
What causes jet lag?
Long haul flights crossing time zones can result in mismatch between environmental cues and body clock
Which hormone produced in the pineal gland is involved in setting the biological clock?
Melatonin
What does negative feedback do?
Response in a way to reverse direction of change
What is positive feedback?
Response in a way so as to change variable even more in direction of change
When is positive feedback used and give examples?
When rapid change is desirable
Eg blood clotting and ovulation
What monitors osmotic pressure of blood plasma?
Osmoreceptors in hypothalamus
What is the difference between osmolarity and osmolality?
Osmolarity = number of osmoles per litre of solution
Osmolality = number of osmoles per kg of solution
What is an osmole?
Amount of substance that dissociates in solution to form one mole of osmotically active particles
When is serum osmolality useful?
When investigating hyponatraemia (low Na+ in blood)
What is the normal range of blood osmolality?
275-295 mOsm/kg
What happens when blood osmolality is high?
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
What happens when blood osmolality is low?
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
What happens when plasma glucose levels increase?
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
What happens when plasma glucose levels decrease?
1) detected by pancreatic alpha cells
2) pancreas releases glucagon
3) stimulates glycogenolysis in liver
4) glucose released into blood and plasma glucose increases
What are hormones?
Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
What is autocrine communication?
Hormone signal acts back on cell of origin
What is paracrine communication?
Hormone signal carried to adjacent cells over short distance via interstitial fluid
What is endocrine communication?
Hormone signal released into bloodstream and carried to distant target cells
What is neurocrine communication?
Hormone originates in neurone and after transport down axon is released into bloodstream and carried to distant target cells
What are the similarities between endocrine and nervous systems?
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
What are the four classifications of hormones and state whether they are water or lipid soluble?
1) peptide/polypeptide - water soluble
2) glycoproteins - water soluble
3) amino acid derivatives - lipid soluble
4) steroids - lipid soluble
Which hormones are peptides/polypeptides?
Insulin
Glucagon
Growth hormone
Which hormones are amino acid derivatives?
Adrenaline
Noradrenaline
Thyroid hormones
Melatonin
Which is the most common amino acid used to synthesise amino acid derived hormones?
Tyrosine
Which hormones are glycoproteins?
LH
FSH
TSH
Which hormones are steroids?
Cortisol
Aldosterone
Testosterone
What are steroid hormones derived from?
Cholesterol
Which hormones must bind to proteins to be transported in the blood and why is this?
Lipid soluble because they are hydrophobic
True or false: only the free form of a hormone is biologically active
TRUE
What are the roles of carrier proteins?
Increase solubility of hormone in plasma
Increase half-life
Readily accessible reserve
Which 3 factors determine hormone levels in blood?
1) rate of production
2) rate of delivery
3) rate of degradation
True or false: hormones circulate in blood at high concentrations
FALSE - very low, picomolar range
How do hormones exert their effects?
By binding to specific receptors
Which receptors do water soluble hormones bind to?
Cell surface receptors:
1) GPCRs
2) tyrosine kinase receptors
Which receptor doesn’t require dimerisation and why is this?
Insulin receptor because it is already dimerised
Which receptors do lipid soluble hormones bind to?
Intracellular receptors
What are the two types of intracellular receptors?
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
Why do lipid soluble hormones have a slower response than water soluble hormones?
Because they need new protein synthesis to occur and this takes time
Where is the appetite control centre situated?
Hypothalamus in clusters of neurones called arcuate nucleus
What are the two types of primary neurones in the arcuate nucleus?
1) stimulatory neurones promote hunger
2) inhibitory neurones promote satiety
Which peptide hormone is released from the stomach wall when it is empty?
Ghrelin-> stimulates appetite
Which peptide hormone is released by cells in the ileum and colon in response to feeding?
PYY (peptide tyrosine tyrosine) -> suppresses appetite
Which peptide hormone is released into the blood by adipocytes?
Leptin -> suppresses appetite
What are the two effects that leptin has on arcuate nucleus?
1) stimulates inhibitory neurones
2) inhibits excitatory neurones
What effect does insulin have on appetite?
Suppresses it
What effect does amylin have on appetite?
Suppresses appetite
Which neurotransmitters do stimulatory primary neurones contain?
1) neuropeptide Y (NPY)
2) Agouti-related peptide (AgRP)
Which neurotransmitter do inhibitory primary neurones contain and which neurotransmitters does it yield?
Pro-opiomelanocortin (POMC)
Yields alpha-MSH and beta-endorphin
