Flashcards in Homeostasis Deck (35):
Maintenance of a stable internal environment despite external changes
Where does homeostasis occur?
Cellular and whole body level
What is homeostasis essential for?
Normal cell function
What do your cells maintain?
Volume, pH, rate of division, ionic gradients, electrolyte concentration, rate of protein synthesis, level of nutrients & waste
What is a negative feedback loop?
Control system within the body that acts to restore the level of some variable to within a given range following any disturbance
What 3 things are required to form a feedback loop?
Receptors, integrator, effectors
Under what condition can a negative feedback loop be reset or overridden?
Bp during exercise
What makes positive feedback loop different to a negative one?
Magnifies a change, rather than negates it
When would a positive feedback loop be present?
Childbirth, lactation, ovulation, blood clotting
What happens to proteins when temperature reaches 42-43•c?
Become denatured (irreversible change)
What are the 4 different types of heat transference?
Radiation, conduction, convection, evaporation
What type of feedback loop is thermoregulation?
What are the receptor, integrator & effectors in thermoregulation?
Thermoreceptors, hypothalmus, physical responses
Where are thermoreceptors located?
Central nervous tissue & deep tissue
Where are peripheral thermoreceptors located?
Thermoregulators can only respond to one thing, what is this?
Either a fall or rise in temperature. Not both
How does the hypothalmus work as part of a negative feedback loop?
Receives information from thermoreceptors and organises appropriate effectors
Strategies used by the body to restore normal levels
Effectors can be put in 2 categories. What are they?
Physical & behavioural
What responses does the body make to a fall in temperature?
Vasoconstriction of cutaneous blood vessels - blood flows to core away from surface, Shivering - muscles contract and relax very quickly to generate heat, Piloerection - hairs stand on end, Increased metabolic rate - heat is generated by the release of certain hormones
What hormones are secreted to help raise temp by increasing the bodies metabolic rate?
Adrenaline & thyroxine
What responses does the body make to a rise on temperature?
Vasodilation of cutaneous blood vessels - skin vessels widen so blood flows towards the skin (flushed), radiation, convection, conduction, hairs lie flat, sweating (evaporation)
What gland in the secretes sweat?
Eccrine glands of the skin
How much sweat is lost when cold?
Less than 500ml a day
How much sweat is lost when hot?
1.5 & 6 litres per hour in very hot weather and exercise
What do we loose from the body when we sweat?
Water & sodium chloride (salts)
What is it vital to replace to prevent heat exhaustion?
Fluids & salts
Why is thermoregulation harder for the elderly?
Thin skin, less hair, immobility, poor nervous system function, loss of subcutaneous fat, poor shivering, poor sweating
Raised core temperature that is not caused by exercise or the enviroment
What can cause pyrexia?
Following infection by a virus or bacterium, hypothalmic set point is raised
In hyperthermia the body temperature rises. What temperature is it safe for the body to raise to for short periods of time?
What temperature for prolonged periods can lead to brain damage?
Excess of 40•c
What are the features of heat stroke?
Hot dry skin, weak respiration, low bp, cerebral oedema, convulsions, coma, death
Hypothermia is a drop in body temperature. At what temperature do your bodies thermoregulatory mechanisms fail?