Lecture 12 - The Endocrine System Flashcards
Why is it important to take into account the time of day samples are taken of melatonin and cortisol?
Their levels change throughout the day
Describe the negative feedback loop of thyroid release
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
Give a biological example of positive feedback
Blood clotting/ovulation
What percentage of TBW is intracellular fluid?
2/3 / 66.666%
What is an osmole?
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
Give a physiological state in which it is useful to look at serum osmolality
Hyponatraemia (low sodium in the blood)
What hormone would be released following a detection of high blood osmolality by the osmoceptors in the hypothalamus?
ADH -> increases water reabsorption in kidney CCD. Also thirst is triggered
What is down by the body to compensate for a low blood osmolality
Decreased in ADH secretion
Where is ADH released from?
Posterior pituitary gland
Above what plasma glucose level do mechanisms start working to bring it back down?
5mM
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?
Stimulates glyogenesis in the liver
Stimulates glucose uptake in the muscle and adipose tissue via upregulating glut4
How does glucagon bring plasma glucose levels back up
Stimulates glycogenolysis in the liver
What is a hormone?
A chemical signal produced in endocrine glands that travels in the bloodstream and acts on distant tissues
What key hormone involved in setting the biological clock is secreted from the pineal gland?
Melatonin
Explain Neurocrine signalling
Hormone originated in neutron and after transport down axon is released into bloodstream and acts on distant cells
Which types of signals produce a more rapid response - lipid soluble or water soluble hormones?
Water soluble. Explanation - they act on cell surface receptors whereas lipid soluble work on intracellular ones which have a longer pathway involving transcription
List the 4 major classes of hormones and whether they’re water or lipid soluble
Polypeptides - water soluble
Glycoproteins - water soluble
Amines - adrenal medulla ones are water soluble, thyroid hormones are lipid soluble
Steroid hormones - lipid soluble
What is the precursor of the steroid hormones?
Cholesterol
Do hormones in the blood circulate at
a) millimolar conc
b) molar conc
c) picomolar conc
c
What 3 main factors determine the level of hormone in the blood
Rate of synthesis
Rate of delivery
Rate of degradation.
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
Hormone response element
Primary neurons processing information to regulate hunger exist in which nucleus in the hypothalamus?
Arcuate nucleus
Which neurotransmitters are found in the following primary neurons of the arcuate nucleus
a) stimulatory
b) inhibitory
AgRP and NPY Alpha MSH (from POMC)
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)
a) stimulating
b) inhibiting
c) inhibiting
