Thermoregulation Flashcards
What branch of the nervous system has major control over both blood flow and sweat gland activation for thermoregulation?
sympathetic
What circulatory structure in the skin is critical for thermoregulation?
arterio-venous anastomoses
it means the cutaneous arterioles can bypass the capillaries by shunting blood directly into venules. This means the blood won’t pass near the surface of the skin, and heat loss will be reduced
Why are people’s faces when they’re exercising?
the AV shunts are open so more blood is passing thorugh the capillaries close to the skin surface in an attempt to cool the body.
Are sympathetic nerves efferent or afferent?
Where do they originate?
they are efferent nerves leaving the spinal cord in the thoracic-lumbar region
Where do sympathetic nerves usually synapse?
they usually synapse in the paravertebral ganglia on either side of the spinal cord (22 on each side)
In sympathetic control of thermoregulation, what neurotransmitter are the preganglionic nerves releasing?
acetylcholine
What kind of receptors does the acetylcholin work on for the postganglionic nerves?
What is the result?
ACh activates postganglionic nicotinic receptors
this depolarizes the postganglionic nerve
What neurotransmitter do the activated postganglionic nerves release?
What’s the result?
they release norepinephrine
this constructs blood vessels
What type of receptor does the norepinephrine work on to contract arterioles?
What kind of receptor is this?
the alpha-1 receptor
this is a G-protein coupled receptor
Oddly enough, sympathetic nerves can also cause vasodilation in the skin circulation. What neurotransmitter is released by the postganglionic nerve in this case?
acethylcholine
When your hands are freezing and painful, what’s actually causing the pain?
it’s the reperfusion after they start to warm up
Why are people more likely to die of hypothermia when they’re drunk?
alcohol dilates cutaneous blood vessels and increases heat loss - think about the drunks with flushed faces
WHere are sweat glands on the body? In other words, where are they not?
They are everywhere except the lips, ear canal, clitoris, labia minora, penis, areolar regions
What are the two types of sweat glands and when are each active?
eccrine - involved in temperature regulation
apocrine - involved in sweating in stressful situations
What is the ultimate controller of sweat gland secretions? Through what nervous system?
The temperature sensors in the hypothalamus, affecting through the sympathetic nervous system
Release of what neurotramsitter from postganglionic nerves will cause sweating from eccrine glands?
acethylcholine
In the case of increasing sweating, what receptor is acetylcholine working on?
muscarinic receptors
What neurotransmitter will activate apocrine sweat glands? Through what receptors?
norepinephrine affecting alpha1 and beta receptors
What ions are actively secreted by sweat glands?
Na, Cl and K
What pumps/channels are used in transporting Na, Cl and K into the lumens of sweat glands
the NKCC pump (Na, K, 2 Cl) will pump them INTO the secretory cells
the CLCA Chloride antiporter and the CFTR then allow the Cl into the sweat gland lumen
the Na and H20 will follow by the electrochemical gradient and osmosis
Once the ions are in the sweat duct, what happens to them?
they are reabsorbed by the CFTR (the Cl) and the ENaC (Na channels)
Why isn’t the water also reabsorbed in the sweat ducts?
there are no aquaporins there
What is the net result out of the sweat glands?
a dilute solution of ions
Na is only 0.9 g/L
K is slightly concentrated relative to plasma
low HCO3
acid pH
If someone has cystic fibrosis, what happens to their sweat?
the CFTR is inactive, but the CLCA is still working
this means they’re able to pump the Cl into the sweat gland lumen, but they’re not able to reabsorb it.
this means their sweat is extra salty
