homeostasis and control of temperature/fever

Question 1

what is the definition of homeostasis

Answer 1

any self regulating process by which biological systems maintain stability while adjusting to changing external conditions

Question 2

which does the anterior hypothalamus respond to: increasing or decreasing environmental temp.

Answer 2

responds to increasing environmental temperatures

Question 3

what does the posterior hypothalamus respond to: increasing or decreasing environmental temperature?

Answer 3

responds to decreasing environmental temperatures

Question 4

how are decreases in the external temp. sensed by the body

Answer 4

via skin thermoreceptors which send information to the anterior hypothalamus which informs the posterior hypothalamus that the body needs to generate heat

Question 5

what changes does the posterior hypothalamus initiate in the body

Answer 5

stimulates thyroid hormones - thyroxine (T4) and triiodothyronine (T3) which work together to increase heat production.. T3 forms more atp
- the sympathetic nervous system is also activated
-signals skeletal muscles to contract - shivering

Question 6

what is the effect of having hypothyroidism on temperature tolerance

Answer 6

means you have low levels of thyroid hormones so more susceptible to cold weather

Question 7

what is the effect of having hyperthyroidism on temperature tolerance

Answer 7

means you have high levels of thyroid hormones so more susceptible to warm weather

Question 8

what is the role of the sympathetic nervous system to increase body temperature - what chemical does it cause the release of

Answer 8

increases catecholamine production
causes vasoconstriction

Question 9

what happens when external temperature is too high, how is it detected and what part of the brain is this info sent to

Answer 9

skin thermoreceptors send signals to the anterior hypothalamus

Question 10

what changes does the anterior hypothalamus carry out in the body when external temperature is too high?

Answer 10

-stimulates sympathetic cholinergic fibres

Question 11

what is the physiological effect when sympathetic cholinergic fibres are stimulated

Answer 11

stimulate thermoregulatory sweat glands leading to increased sweating which evaporates from skin - heat losing mechanism as liquid-> gas

Question 12

does the anterior hypothalamus increase or decrease the activity of the sympathetic nervous system + why

Answer 12

decreases, vasodilation - blood from body core travels to surface of skin where heat is lost by radiation/conduction/convection

Question 13

what are symptoms of heat exhaustion

Answer 13

dizziness
rapid heartbeat
fainting

Question 14

what are symptoms of heat stroke

Answer 14

confusion
seizures
coma

Question 15

what is malignant hyperthermia

Answer 15

when heat dissipating mechanisms are unable to keep up with the increased heat production

Question 16

what is the role of prostaglandins and which interleukin stimulates their production

Answer 16

increase the set point temperature
IL-1 in the anterior hypothalamus
then normal heat increasing mechanisms occur to increase temperature

Question 17

mechanism of action of aspirin

Answer 17

blocks prostaglandin production therefore stops the symptoms of fever

Question 18

what is the role of the preoptic anterior hypothalamus in temperature control

Answer 18

provides an integration centre for sensory temperature inputs. both deep-body and peripheral inputs give a holistic picture of the body’s thermal state

Question 19

how does the body carry out deep body thermoception

Answer 19

via thermosensitive neurons found in the CNS

Question 20

cold sensitive neurons receive skin temp. information via which type of fibres

Answer 20

thin myelinated A delta fibres

Question 21

warmth sensitive sensors, located deeper in the dermis, through what type of fibres do they receive signals

Answer 21

via unmyelinated C fibres

Question 22

what do proactive responses mean in thermoeffectors

Answer 22

behavioural and recruited before the skin temp changes

Question 23

what do corrective, late responses mean in relation to thermoeffectors

Answer 23

can be physiological or behavioural and they are recruited after the skin temp changes

Question 24

what are examples of catecholamines

Answer 24

epinephrine
norepinephrine

Question 25

what cell is affected by catecholamines, and what do they do in relation to temp. change

Answer 25

bind to ß receptors on brown adipose cells (good fat cells) - burn calories and generate heat

Question 26

what is the role of TRPM8 in temperature detection

Answer 26

Thermosensitive ion channel TRPM8 plays a critical role in the transduction of moderately cold stimuli that give rise to cool sensations - peripheral sensing

Question 27

what happens during anapyrexia

Answer 27

-decrease in body temp. due to a decrease in the set point.

-occurs in trauma, hypoxia, shock, heatstroke, intoxications, anaesthesia, starvation

-threshold for cold thermogenesis decreases by a few degreesv