homeostatic regulation of core body temperature

Question 1

what is the homeostatic regulation of core body temperature?

Answer 1

thermoregulation; ensures that enzymes function efficiently. core temp is the temp of vital organs like the brain, heart, lungs, liver and digestive system. skin temp is different to core temp.
- involves the nervous system and endocrine system
- negative feedback controls the regulation of core body temp.

Question 2

what is the importance of homeostatic regulation of core body temperature?

Answer 2

enzymes speed up all chemical reactions that take place inside a cell. w/o the enzymes, metabolism would be too slow to keep the organism alive. enzymes are temp sensitive. if it is too cold, they will work too slowly. if it gets too hot, the enzymes will denature and stop working.

Question 3

how does the body lose heat?

Answer 3

1. conduction (transfer of thermal energy by direct contact)
   - thermal energy transfers to the area of low thermal energy. hot skin loses heat to cool air.
   - factors increasing rate of conduction: increasing SA to vol ratio, increasing diff between temp of body and air, increasing the density of the substances involved since more particles are available for collision
2. radiation (electromagnetic energy waves)
   - the hotter the object, more waves it releases
3. convection (movement of molecules from warm areas to cooler areas)
   - warm air rises away from the body by convection
4. evaporation (thermal energy is required to change the liquid into a gas)
   - evaporation of liquid sweat uses thermal energy from the body
   - factors increasing rate of evaporation: increasing SA of skin, increasing diff between temp of body and air, decreasing air humidity.

Question 4

how does the body gain heat?

Answer 4

the majority of heat is produced by exergonic chemical reactions. metabolic rate and physical activity greatly influence the rate of heat production in the body. the more physically active, the higher the metabolic rate. other factors: sex, age, body weight, general health

Question 5

what are thermoreceptors?

Answer 5

1. sensory neuron that can detect changes in temp. found in brain and skin.
2. thermoreceptors in the brain monitor blood temp as an indicator of core temp; this info can override info from the skin. the hypothalamus is linked to the pituitary gland in the brain.
3. skin thermoreceptors monitor skin temp; they send a nervous signal to the hypothalamus in the brain. the hypothalamus determines if the temp change is outside the optimal range, it will send the response signal to various effectors if necessary.

Question 6

what are the behavioural responses to changes in temp?

Answer 6

response to low temp
- curling up, huddling, finding shelter, putting on more clothes
response in high temp
- stretching out, finding shade, swimming, removing clothes.

Question 7

what are the physiological responses to changes in temp?

Answer 7

1. type of response: nervous
   effector: smooth muscles in arterioles in the skin
   response to low temp: muscles contract using vasoconstriction. less blood is carried from the core to the surface of the body, reducing temp loss. extremities, like the hands and feet can feel very cold, turn blue and even be damaged.
   response to high temp: muscles relax using vasodilation. more blood is carried from the core to the surface, where heat is lost by convection and radiation.
2. type of response: nervous
   effector: sweat glands
   response to low temp: sweat glands are inhibited, no sweat is produced.
   response to high temp: sweat glands are activated. sweat produced to allow cooling by evaporation
3. type of response: nervous
   effector: erector pili muscles in skin
   response to low temp: muscles contract, raising skin hairs and trapping an insulating layer of warm air next to the skin. not very effective in humans, just causing goosebumps.
   response to high temp: muscles relax, lowering the skin hairs and allowing air to circulate over the skin, encouraging convection and evaporation
4. type of response: nervous
   effector: skeletal muscles
   response in low temp: shivering- muscles contract and relax repeatedly, generates heat by friction and increasing metabolic rates.
   response in high temp: no shivering
5. type of response: endocrine
   effector: adrenal glands
   response to low temp: release adrenaline, increasing cellular respiration and other metabolic reactions. increases heat through exothermic reactions.
   response to high temp: adrenal glands are inhibited, no adrenaline released
6. type of response: endocrine
   effector: thyroid gland
   response in low temp: multiple-step hormone-signalling pathway releases thyroxine from the thyroid gland. thyroxine increases cellular metabolic rate in all body cells. increased metabolic rates increase heat production by cells, esp the liver
   response in high temp: glands that stimulate the thyroid gland are inhibited by thyroxine in the bloodstream. no additional thyroxine produced.

Question 8

what is a fever?

Answer 8

when infected with a disease, white blood cells release a chemical called pyrogen that temporarily raises the thermoregulatory set point by 2-3 degrees celsius. this fever helps to kill bacteria and can inhibit viruses. it also explains why the body shivers even though it feels hot

Question 9

what is hypothermia and hyperthermia?

Answer 9

hypothermia
- low body/core temp due to exposure to cold weather. body induces hypothermia as a means of decreasing body metabolism and the need of oxygen for cellular respiration.
- symptoms: loss of muscle control, weak heart rate, shallow breathing, loss of consciousness
hyperthermia
- overheating of the body, high body temperatures causes permanent damage to enzymes in the body
- symptoms: rapid heart rate, muscle weakness, loss of muscle control, reduced sweating.