2.77b - Thermoregulation

- negative feedback loop - method of control and maintaining constant conditions 
- in the case of humans our fixed point is our body temperature (37/38 degrees) 
- in order for it to work we have receptors of body temperature - hypothalamus (region of the brain)
- responds to a stimulus (temp of body and blood) 
- fixed point that we regulate around and try to maintain is our body temperature 
- body temperature feeds into the brain and is then compared to the theoretical fixed point (37/38degrees)
- if need to be increased or decreased then it is brought about by the action of the effectors (e.g. skin) 
- response is either a increase or decrease in body temperature 
- this would feedback to the hypothalamus and based on the input, a new output would be produced 

- main components of skin to control the body temperature - sweat glands and capillary network (allows blood to move closer or further away from the surface of the skin

- x axis - time 

- y axis - 37 and 38 degrees celsius (regulation points) 
if body temperature increases - input into hypothalamus, stimulates responses in the skin for cooling - sweating and increased blood flow to the surface of the skin
- blood vessels dilate (widen) and so more blood flows to the surface 
- this increases exchange of heat to outside of body by evaporation of sweat and radiation
- This brings about the cooling of the blood and returns body temperature to the fix level 


- If body temp falls, this feeds to the hypothalamus and switches on regulations to increase the body temperature - shivering, raised hairs 
- Forces blood to travel deeper through tissues and reduces heat exchange with external environment 
- temperature of the blood varies up and down around the fixed point making the efficiency of the system depend on how far they deviate from the fixed point