5.1.1 Communication and Homeostasis

Question 1

Hoemostasis

Answer 1

Maintenance of a constant internal environment via physiological control systems
Keep body temp, blood pH, blood glucose, blood water potential within set limits
Involves negative feedback loops

Question 2

Negative feedback

Answer 2

When deviation from the set limits is detected in the body by receptors
Mechanisms put in place to restore the conditions back within the set limits
Involves nervous system + hormones

Question 3

Positive feeback

Answer 3

When deviation from set limits triggers a response to increase the deviation further
Rare in the body
- During childbirth, baby’s head presses on the cervix - causes oxytocin to be released - uterus contracts - results in the release of more oxytocin

Question 4

Thermoregulation

Answer 4

If body temp dropped too low, insufficient kinetic energy for enzyme-controlled reactions
If body temp increased too high, enzymes would denature

Question 5

Ectotherms

Answer 5

Control internal temp by changing their behaviour - less well than endotherms
Within aquatic - don’t have to regulate temp much - water has high specific heat capacity + remains relatively constant
On land - bigger challenge - temp of air fluctuates

Question 6

Endotherms

Answer 6

Regulate body temp through nervous response
- Peripheral temp receptors in skin detect change in external temp
- Sends an impulse along sensory neurone to the brain - hypothalamus coordinates impulse
- Triggers a response by glands in skin + muscles

Produce more sweat - water has high latent heat of evaporation
Vasodilation - more blood flows through arterioles near skin surface - more heat energy lost
Vasoconstriction - arterioles near skin surface constrict, less heat lost