Karius Thermoregulation Flashcards
Normal body temperature
36.3 - 37.1 degrees C
How is controlled variable measured
sensor ex. thermostat
Sensor of controlled variable system
ex. thermostat if it’s cooler that set point then the the heater will turn on, if thermostat is warmer than the set point then the air conditioning will turn on
Feed-Forward system
information is used to prevent changes in the controlled varible
Example of feed forward system
- sun an change room temperature, the actual room never changed
- bodies in a room make the room warmer but the actual temperature of the room never changes
- If it’s cold outside, you put on a sweater, body temperature didn’t change but you know it would if you didn’t but a sweater on
Is thermoregulation feed forward or negative feedback
Negative feedback with some feed forward aspects
Thermoreceptors
neurons which change their firing rate in response to changes in local temperature
Warm sensitive thermoreceptors
4 channels - TRP V1-4 which all cover different temperature ranges
V = vanilloid = capsaicin
Warm sensitive thermoreceptors at low temperatures
not a lot of action potentials
Warm sensitive thermoreceptors at high temperatures
lots of action potentials – except it can plateau and that means the skin is burning
Cold sensitive thermoreceptors activated
as temperature decreases
Ions involved in cold sensitive thermoreceptors
Na and Ca++ influx
Where are thermoreceptors found
skin, viscera, and the brain (hypothalamus)
Hypothalamus invovled in thermoregulatory system
controls hormonal, autonomic, and behavioral changes
Location for response to heat
anterior - heat loss behaviors
Location for response to cooling
posterior - heat production behaviors
Most controlled temperature place in the body
brain and abdomen
Least controlled temperature place in the body
hands and feet
Body temp change with sleep
temp decreases b/c of circadian influence
Body temp change with excercise
temp increases b/c of increase in heat production and set point increase
What determines set point
hypothalamus determines set point for core temp
Set point
desired temp value
Temperature influence on body
changes enzyme activity and cellular function
Change in environment temperature
can threaten body temperature
Cutaneous themoreceptors
*these tell us about environmental conditions
axons located in skin
often bimodal
may be warm or cold - 10x as sensitive to cold
Visceral thermoreceptors
*threats to maintenance due to food intake (eat scoop of ice cream or hot pepper)
Central thermoreceptors location
pre-optic and superoptic region of hypothalamus
Central thermoreceptors function
tells me about temperature in the brain b/d neuron cell bodies are sensitive to change in temp
relay info to hypothalamus
3x as many warm receptors
Heat production mechanism
sympathetic system, hormonal control
Hormonal heat production mechanism
thyroxin and epinephrine/NE
Ways of producing heat
muscular activity - can be voluntary or involuntary (shivering)
Non-shivering thermogenesis (jumping up and down when at gas station)
Shivering sensory to hypothalamus
dorsomedial posterior hypothalamus to increase motorneuron excitation
Non-shivering thermogenesis
hormone influence, food intake, brown adipose tissue
Increase food intake on thermogenesis
non-shivering thermogenesis
increase metabolism
Brown adipose tissue
use ATP without directing it towards somewhere
low efficiency = lots of heat production
strong in infants and not adults
Evaporative heat loss
energy lost as water evaporates
Two kinds of evaporative heat loss
sweating (controlled) and insensible (respiratory)
Convection
heat loss
movement of molecules AWAY from contact
Conduction
heat loss
transfer of heat between objects in contact with one another
depends on the object being colder than body temp
Radiation
heat loss
infrared radiation transferring heat between 2 objects NOT in physical contact
ex. a wall
How to respond to changes in core temperature
hypothalamus will adjust to both heat loss and heat production
Hypothalamus response to increased core temp
decrease heat production - less likely to eat and exercise
increase heat loss - blood to skin (flushing), sweat, insensible heat loss (panting)
How to increase convection and conduction
send more blood to the skin to send more heat from blood to external environment
Sweat gland innervation
sympathetic CHOLINERGIC- Ach is the NT binding to a muscarinic receptor
Primary secretion of sweat
high in water and sodium
*when you sweat a little bit
Low flow rate of sweat
concentrated- little water, high sodium
High flow rates
diluted- lots of water, little sodium
What happens along the sweat duct
reabsorb sodium, chloride, and water
Fever
controlled increase in body temperation
Hypothalamus during fever
causes a increase in set point
telling body to change to accommodate for the set point change
How to make a fever
Secretion of endotoxins –> Immune cells activated –> prostaglandin E2 –> increase hypothalamic set point
Body temp to set point temperature during fever
body temp
Body response to making a fever
increase heat production and decease heat loss
Increasing heat production during fever
shivering and non-shvering thermogenesis
Decreasing heat loss during fever
decrease conduction/convection and decrease sweat
Getting rid of fever
no endotoxins, no more immune activation, set point goes back to normal
Body temp to set point temperature when getting rid of fever
Tb > Tset point
Fever breaking
decrease heat production, increase heat loss
Decreasing heat production when breaking a fever
eat less, do less
Increasing heat loss when breaking a fever
conduction/convection, sweat, pant
Hyper and Hypothermia
uncontrolled changed in body temperature
Implications for hypo and hyperthermia
set point is normal, environmental stresses exceed bodies ability to regulate temp
hypothalamic regulation may be lost
Hypothalamic tumor
can’t thermoregulate
