The Nervous Shitstem

Question 1

Pupil reflex bright light

Answer 1

1. Bright light enters eye
2. Photoreceptors in the retina of the eye are stimulated to produce nerve impulses
3. Nerve impulses are transmitted to sensory neurone in the optic nerve
4. Optic nerve transmits nerve impulse to relay neurone in the brain across a synapse via chem signals
5. Relay neurone transmits nerve impulses to motor neurone across another synapse
6. Motor neurone transmits nerve impulses to muscles in the iris
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7. In the iris, circular muscles contract, radial muscles relax
8. Pupil constricts, less light enters eye

Question 2

Accommodation. CLOSE OBJECT

Answer 2

1. Diverging light rays from close object enter eye
2. In the eye, ciliary muscles contract,
   3 causing suspension ligaments to slacken
   4 Lens becomes more convex & thicker
   5 Focal length decreases
   6 Image is sharply focused onto fovea
   7 This stimulates photoreceptors in the retina to generate nerve impulses that are transmitted to the sensory neurone in the optic nerve