thermoregulation Flashcards
which region of the brain is responsible for regulation of body temperature? (specific nuclei + function)
hypothalamus (pre-optic area = heat dissipation, and posterior hypothalamus = heat conservation)
where are thermoreceptors found?
peripheral thermo R: skin, viscera, muscles
central thermo R: preoptic hypotha, medulla
what are the types of thermoreceptors (name, function)
warm sensing - fire with increased temperature, VR1 TRP, expresses heat-activated cation ch
cold sensing - fire with decreased temperature, CMR1 TRP, expresses cold-activated cation ch
define set point for body temperature
hypothalamus has a set temperature at which firing of warm sensitive neurons equal firing of cold-sensitive neurons
recall and explain the hypothalamus picture with temperature sensing neurons and thalamic nuclei
warm-sensing neuron from periphery and central project to pre-optic area > heat loss mechanism
cold sensing neuron from both project to posterior hypothalamus > heat production mechanism
importantly: these also project to inhibitory interneurons that inhibit the contra effects ie (activation of warm sensing neurons will activate preoptic area to dissipate heat but also to interneurons to inhibit heat production by posterior thalamus)
what are the 4 methods of heat exchange that is used to regulate body temperature
radiation - infrared
conduction - 2 object contact
convection - movement of air or water
evaporation - water evap from sweat removes energy from skin
name ANS regulation of temperature (5)
sweat secretion
vasomotor response
piloerector response
shivering
nonshivering thermogenesis
describe the anatomy of sweat glands
Sweat glands contain secretory (deep in skin) and duct portions (passes outward to skin surface)
- secretory portion make and holds sweat (at this point what is osmolarity of the fluid?)
- sweat carried out through duct portion: where ions are reabsorbed as secretion travels to surface
the reabsorption of ions is dependent on…
rate of flow
faster RoF less chance for ions to reabsorb
describe the SNS innervation of sweat glands. list players + detail the mechanisms
hypothalamus increases sympathetic outflow to sweat glands
- increases release of ACh
- sweat glands mainly express M3 R
- couples through Gq > increase intracellular calcium > opening of K and Cl ch > Na follows Cl and water is pulled in
how does vasculature change in response to temperature change
- increase in temp > vasodilation of BVes near skin > hypothalamus inhibits sympathetic nervous system > decrease release NE > inhibit a1 mediated vasocon = more blood to skin = heat loss thru conduction/convection/radiation
- decrease in temperature > activates SNS > vasoconstriction > inhibit the above
describe piloerection
- decrease temperature > piloerection
- erector pili innervated by SNS and express a1 > contraction pili muscles > hair trapping layer of warm air next to skin (not effective in humans)
describe mechanism of shivering
decrease temperature causes shivering
involuntary response mediated by somatic motor neurons
Asynchronous muscle contractions > increases metabolic rate by 5x > generation of heat
describe non shivering thermogenesis
decrease in temperature > SNS activation > release NE at brown adipose tissue > activation b3 > lipolysis = oxidation of fatty acids > release energy
describe what happens with an infection + how does NSAID work?
- In response to infection, macrophages release interleukin > increase set point by 2-3ºC to help kill bacteria and optimize immune cell function
- Interleukins stimulate cells of OVLT to produce arachidonic acid > converted to prostaglandins by cyclooxygenases (COX2)
- prostaglandin E2 (PGE2) binds receptors in preoptic area to inhibit firing of warm-sensitive neuron > increase in heat generation/conserv
- NSAIDs (ibuprofen, Advil, etc.) inhibit COX-2 to decrease fever
