Coordination, Homeostasis and Reproduction
What this domain tests
Coordination, Homeostasis and Reproduction tests nervous and hormonal control, feedback mechanisms, human reproduction and contraception.
Core rules
- The CNS is the brain and spinal cord; the PNS is the peripheral nerves. A reflex arc follows sensory neurone → relay neurone → motor neurone → effector.
- Reflex actions are rapid and involuntary. A synapse uses neurotransmitters to pass impulses between neurones.
- Hormones are chemical messengers carried in the blood; they act more slowly but for longer than nerve impulses.
- Homeostasis keeps internal conditions stable by negative feedback: stimulus → receptor → control centre → effector → response.
- Temperature control involves sweating, vasodilation and shivering. Blood glucose is lowered by insulin and raised by glucagon.
- Menstrual cycle: FSH matures the follicle, oestrogen repairs the uterus lining, LH triggers ovulation, and progesterone maintains the lining.
- Contraception includes barrier, hormonal and surgical methods with different effectiveness and risks.
Worked example
Blood glucose rises after a meal. The pancreas detects this and secretes insulin. Insulin increases glucose uptake by cells and glycogen storage in the liver, so blood glucose falls. If it falls too low, glucagon stimulates glycogen breakdown. This is negative feedback because the response reverses the original change.
Traps
Do not say nerves use hormones or that hormones travel along nerve fibres. Do not confuse negative and positive feedback. In the menstrual cycle, do not swap the roles of oestrogen and progesterone. Label the reflex arc direction correctly.