Homeostasis & Temp Reg Flashcards
What is homeostasis?
Maintaining a stable internal environment in response to changes in external conditions e.g. light, seasons, temp, pressure.
Occurs at tissue & cellular levels.
What is the mechanism for homeostasis?
Negative-feedback
Why do we need to stay w/in certain ranges?
Start to see cellular damage if we go outside of these ranges e.g. cell enzymes denature.
E.g.
39-40- fever
40-44- heat stoke, brain lesions
What is the range for temperature? What do we expect to happen to our temp ranges during the day?
36-37.5°C - set point = 37°C
Temp fluctuate through the day within this range.
This stable internal environment is different for different genders, ages or stages of life e.g. pregnancy.
How does body respond to an increase in body temperature (hyperthermia)?
- Stimulus that caused temp to go up e.g. running, hot day.
- Temp has gone up - detected by Thermoreceptors.
- found in skin - for temp of external environment.
- found in hypothalamus - core temp by monitoring the temp of blood. - Thermoreceptors send information to Hypothalamus (control centre for temp).
- Hypothalamus sends instructions to effectors:
- Sweating - sweat glands.
- Vasodilation - blood vessels dilate - This shunts the blood & directs it to the skin. Allows the blood to go slower to give more time for evaporation. - Causes temp to reduce = negative feedback
-Continuous cycle - temp reducing is still detected by the thermoreceptors.
How does body respond to decrease in body temp? (Hypothermia)?
- Stimulus - getting cold.
- Detection by thermoreceptors
- Send info to hypothalamus
- Effectors told to increase temp:
- Vasoconstriction - blood to the core & constricts the blood to periphery e.g. fingers, toes = conserves heat for key organs.
- Shivering - continuous contraction & relaxation of muscle = aerobic respiration = creates heat.
- Erector pili contraction - hair standing up = trap heat.
- Increase metabolism = create heat.
5.Temp increases.
Give some types of sensors in the body (receptors).
Peripheral receptors
- Type I mechanoreceptors - touch
- Nociceptors- pain
- Thermoreceptors
- Proprioreceptors- muscle spindle (muscle length) & golgi tendon organs (muscle tension)
Central receptors
- Hypothalamus - central thermoreceptor
- Chemoreceptors - in medulla
- Pressure receptors - measures partial pressures of CO2 & O2.
What do effectors do?
- Compensation
- These mechanism can lead to disease
How do we produce heat?
- Basal rate of metabolism (60-70% in heart, liver, brain & kidneys)
- Dietary thermogenesis (5-15% fat, carbohydrate 8%, protein 20%)
- Non-shivering thermogenesis
-Shivering thermogenesis (can increase metabolic rate 5x) - Work (20-30% muscles)
How do we loose heat?
Convection:
- Removal of body heat by convection air currents
- Heat must be conducted first
- Effected by wind velocity
Evaporation:
- Evaporation of water from skin surface
What happens in hyperthermia?
e.g. in exercise
- Exercise starting - increase in heat production
- Heat is detected by thermoreceptors- sends impulse to hypothalamus.
- There’s a lag - amount of heat loss is less than heat production = get hot = heat storage because making more heat than we can get rid of.
- Heat storage drops off as effectors start to do work - effectors are now meeting the demand of heat production.
- Temp no longer increases further - we continue on at new increased core temp from set value, but it is no longer rising.
What happens in fever hypothermia?
- Due to presence of a pathogen = external stimulus.
- Pathogens activates immune system
- Cytokines - activate immune system - they breach the blood-brain barrier & go to hypothalamus
- They increase our normal temp set point = fever.
- This makes body a hostile environment for a pathogen - makes it harder for the pathogen to reproduce.
- If temp falls below our new higher set point, we shiver despite them still being hot by the standards of the normal set point.
How do hot flushes occur?
- Oestrogen declines in menopause.
- Reduced oestrogen feedback system
- Impacts hypothalamus
- Makes hypothalamus more sensitive to temp changes
- = hot flushes
What occurs in heat stroke?
- Above 41°C = clinical symptoms.
- Getting hotter → moves blood to periphery causing reduced cardiac output of blood to brain because sent to skin = confusion.
Clinical symptoms of heat stoke?
- Confusion & loss of consciousness.
- Increased core body temperature
- Abnormal blood clotting
- Heat cytotoxicity → organ damage.
- Muscle breakdown- Rhabdomyolysis = leakage of muscle-cell contents into circulation.
