homeostasis and control of temperature/fever Flashcards
what is the definition of homeostasis
any self regulating process by which biological systems maintain stability while adjusting to changing external conditions
which does the anterior hypothalamus respond to: increasing or decreasing environmental temp.
responds to increasing environmental temperatures
what does the posterior hypothalamus respond to: increasing or decreasing environmental temperature?
responds to decreasing environmental temperatures
how are decreases in the external temp. sensed by the body
via skin thermoreceptors which send information to the anterior hypothalamus which informs the posterior hypothalamus that the body needs to generate heat
what changes does the posterior hypothalamus initiate in the body
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
what is the effect of having hypothyroidism on temperature tolerance
means you have low levels of thyroid hormones so more susceptible to cold weather
what is the effect of having hyperthyroidism on temperature tolerance
means you have high levels of thyroid hormones so more susceptible to warm weather
what is the role of the sympathetic nervous system to increase body temperature - what chemical does it cause the release of
increases catecholamine production
causes vasoconstriction
what happens when external temperature is too high, how is it detected and what part of the brain is this info sent to
skin thermoreceptors send signals to the anterior hypothalamus
what changes does the anterior hypothalamus carry out in the body when external temperature is too high?
-stimulates sympathetic cholinergic fibres
what is the physiological effect when sympathetic cholinergic fibres are stimulated
stimulate thermoregulatory sweat glands leading to increased sweating which evaporates from skin - heat losing mechanism as liquid-> gas
does the anterior hypothalamus increase or decrease the activity of the sympathetic nervous system + why
decreases, vasodilation - blood from body core travels to surface of skin where heat is lost by radiation/conduction/convection
what are symptoms of heat exhaustion
dizziness
rapid heartbeat
fainting
what are symptoms of heat stroke
confusion
seizures
coma
what is malignant hyperthermia
when heat dissipating mechanisms are unable to keep up with the increased heat production
what is the role of prostaglandins and which interleukin stimulates their production
increase the set point temperature
IL-1 in the anterior hypothalamus
then normal heat increasing mechanisms occur to increase temperature
mechanism of action of aspirin
blocks prostaglandin production therefore stops the symptoms of fever
what is the role of the preoptic anterior hypothalamus in temperature control
provides an integration centre for sensory temperature inputs. both deep-body and peripheral inputs give a holistic picture of the body’s thermal state
how does the body carry out deep body thermoception
via thermosensitive neurons found in the CNS
cold sensitive neurons receive skin temp. information via which type of fibres
thin myelinated A delta fibres
warmth sensitive sensors, located deeper in the dermis, through what type of fibres do they receive signals
via unmyelinated C fibres
what do proactive responses mean in thermoeffectors
behavioural and recruited before the skin temp changes
what do corrective, late responses mean in relation to thermoeffectors
can be physiological or behavioural and they are recruited after the skin temp changes
what are examples of catecholamines
epinephrine
norepinephrine
what cell is affected by catecholamines, and what do they do in relation to temp. change
bind to ß receptors on brown adipose cells (good fat cells) - burn calories and generate heat
what is the role of TRPM8 in temperature detection
Thermosensitive ion channel TRPM8 plays a critical role in the transduction of moderately cold stimuli that give rise to cool sensations - peripheral sensing
what happens during anapyrexia
-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
