Topic 6 of 8 · Form 4
Excretion, homeostasis and coordination
Removal of metabolic waste: carbon dioxide (lungs), urea (kidneys). Urea is made in the liver by deamination of excess amino acids. The kidney filters blood (glomerulus) and reabsorbs useful substances (glucose, water, some salts). Dialysis and transplants treat kidney failure.
Notes for this topic 1 file, in order
Create a free account to download PDFs.
Excretion
Removal of metabolic waste: carbon dioxide (lungs), urea (kidneys). Urea is made in the liver by deamination of excess amino acids. The kidney filters blood (glomerulus) and reabsorbs useful substances (glucose, water, some salts). Dialysis and transplants treat kidney failure.
Homeostasis
Maintaining a constant internal environment by negative feedback.
- Temperature control: sweating, vasodilation and vasoconstriction, shivering.
- Blood glucose: insulin (lowers) and glucagon (raises), both from the pancreas; type 1 diabetes and its treatment.
The nervous system
Central and peripheral nervous systems; sensory, relay and motor neurones; reflex arcs; synapses (neurotransmitter diffuses across the gap). The eye: structure, accommodation and pupil reflex.
Hormones
Endocrine glands release hormones into the blood: adrenaline (fight or flight), insulin, glucagon, testosterone, oestrogen. Comparison of nervous and hormonal control.
Plant responses
Phototropism and gravitropism controlled by auxin.
Drugs
Medicinal drugs (antibiotics) and misused drugs (alcohol, heroin, tobacco); effects on the body and society.
Check yourself
- Where is urea produced?
- Which hormone raises blood glucose?
- What happens to the pupil in bright light?
Show answers
- In the liver.
- Glucagon.
- It constricts (becomes smaller) – circular muscles of the iris contract.
Questions about this topic (0)
No questions about this topic yet.
Sign in or create a free account to join in.