Unit 10
Control and coordination.
How the body senses and answers: nerves, a thermostat near 37 degrees, hormones, the eye and the ear, and the brain.
Before this unit
The unit, lesson by lesson
Lessons
7 lessons · 45 practice questions · about 3 hours
Nerve signals
How a nerve cell passes a message on: the resting potential, the threshold, an impulse that is all or nothing, strength coded as rate, and myelin that speeds the impulse a hundredfold.
Homeostasis and feedback
How the body holds 37 degrees: a cool room and a freezing night, what happens with the thermostat switched off, why sweat cools, the band where you neither shiver nor sweat, and what negative feedback is.
Hormones
Chemical messengers in the blood: how insulin and glucagon hold blood sugar steady, when sugar peaks after a meal, where the sugar comes from when you skip a meal, and what happens without insulin.
The eye and vision
How the eye focuses: power in dioptres, the near point, the ageing eye, short sight and the far point, and which glasses correct each eye.
The brain at work
A folded sheet of neurons with a map of jobs: seeing at the back, movement in a strip across the top, crossed wiring so each side of the brain serves the opposite side of the body, speech that lives on the left, and neurons that fire faster when their area works.
Touch, warmth and pain
A fingertip as a laboratory of the senses: receptors that report strength by how fast they fire, fast and slow receptors, vibration that each receptor is tuned to a rhythm of its own, and separate nerve endings for cold, warmth and pain.
Pitch and place
How the ear hears: tiny pushes of air, a wave that sorts pitch along the cochlea, a quiet sound heard only at some pitches, and high notes that go first with age and noise.