2.77 b

objective 2.77b - understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis.

NEGATIVE FEEDBACK LOOP

-negative feedback look- to control body temperature in humans to the constant conditions of 37ºC
Receptor - Hypothalamus, which is the region of the brain which responds to the stimulus of blood temperature. it compares the body temperature to the 'theoretical level' 37ºC


Co-ordinator is body temperature- 37ºC

Effectors- used when the body temperature needs to be raised or lowered to reach the theoretical level. (to control body temperature) 

an example of an effector is SKIN. 

responses. 

to heat-

sweat glands. when the body temperature needs to be lowered, blood flow to the surface of the skin increases through dilated blood vessels. the body is cooled through the evaporation of sweat, and the radiation of heat from the blood.

to cold-

less blood is pumped to the skins surface, and the blood vessels constrict to allow less heat to radiate from the body. also the hairs stand upright to act as a blanket, to trap air as insulation. 

stimuli- the temperature of blood being above or below 37ºC

objective 2.77 a

objective 2.77 a - understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis
homeo- same
stasis- fixed point/conditions
so homeostasis - same conditions, conditions kept same/ constant
homeothermic- maintain same temperature
mammals, when the environmental temperature increases and decreases the body temperature remains the SAME (known as warm blooded animals)
they are homeothermic. they carry out thermoregulation which is an example of homeostasis
for enzyme reactions to occur at their maximum potential they have an 'optimum temperature'
the temperature that mammals maintain is very close to/same as the optimum temperature of enzymes

video for 2.76

2.76

objective 2.76 - understand that organisms are able to respond to changes in their environment
in MRS GREN the S stands for Sensitivity. which is how organisms respond to changes in their environment

changes in environment are changes in - light, temperature, pressure levels and chemical levels.
1 organisms detect changes with receptors
2 organisms respond to these changers with 'effectors' (muscles and glands)
it is the response which ensures the survival of the organism.