Homeostasis
Homeostasis keeps the internal environment within limits: blood glucose, temperature and water. Automatic control systems have receptors, a coordination centre and effectors.
Nervous system
A reflex arc is receptor → sensory neurone → synapse in the CNS → motor neurone → effector. Reflexes are rapid and automatic. Synapses use chemical transmitter to pass the impulse.
The eye focuses light on the retina. Accommodation: ciliary muscles and suspensory ligaments change lens shape. Myopia and hyperopia can be corrected with lenses or surgery.
Hormones
The endocrine system secretes hormones into the blood. Adrenaline prepares the body for fight or flight. Thyroxine controls metabolic rate via negative feedback.
Blood glucose: insulin from the pancreas lowers glucose by storing glycogen in the liver. Glucagon raises glucose. Type 1 diabetes needs insulin; Type 2 is often managed with diet and exercise.
The menstrual cycle involves FSH, LH, oestrogen and progesterone. Contraception can be hormonal or non-hormonal. IVF uses FSH and LH to stimulate egg production.
Taught with support from Joseph Danso, Science Lecturer in London. Book a session.