Lecture 11- Intro To Endocrine System Flashcards
What is a circadian rhythm.
24 hour cycle in a physiological process
Circadian rhythm cues?
Light, temperature, eating times etc
What hormone sets biological clock?
Melatonin from pineal gland
What causes jet lag?
Environmental cues and circadian rhythm going out of sync
Where is osmotic pressure of blood plasma detected?
Osmoreceptors of hypothalamus
Osmolarity vs osmolality?
Osmolarity refers to osmolarity per litre while osmolality refers to osmoles per kg
What is an osmole?
Amount of substance that dissociates in solution to form one mole of osmotically active particles
Eg 1mM solution of NaCl corresponds to 2mOsmol/L due to the Na and Cl both being osmotically active
What is osmolality reference range?
275 to 295 mOsmol/Kg
How is body fluid homeostasis controlled?
High osmolality detected by osmoreceptors in hypothalamus resulting in thirst and ADh secretion from posterior pituitary etc
What is neurocrine secretion?
Hormone originates in neurone and is transported down the axon before it is released and carried to distant tissues
Hormone types?
Peptide= insulin and growth hormone water soluble extracellular receptors
Amino acid derived= adrenaline and melatonin can be water (adrenal medulla) or lipid soluble (thyroid)
Steroid= cortisol, testosterone etc all made from cholesterol and act intracellularly
Glycoproteins= large proteins eg LH, FSH and water soluble
Hormone transport?
Carrier proteins. Only free hormone can bind to receptors. Carrier proteins ensure readily available reserve and increase half life
Why are intracellular hormones slower acting?
They alter gene transcription and their actions are exerted through protein production which causes a cellular response. This is a slow process
How is appetite controlled?
Through the arcuate nucleus of the hypothalamus. Stimulators and inhibitory primary neurons are integrated to alter feeding behaviour through a secondary neuron
Appetite hormones?
Ghrelin is the only stimulatory. Produced by stomach wall when empty.
PYY released from ileum and colon when full and suppressed appetite
Leptin- released from adipocytes and can uncouple proteins in mitochondria to release heat
Insulin- similar to leptin
Amusing- released by pancreas suppressed appetite
