stimulus --> receptor --> coordination --> effector --> response

Central nervous system

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Synapses

Axon

Nerve-muscle junction

Myelin

Junctions  with other neurones

 Fibre which carries impulses to effector organ

Impusles carreid out to muscle

Fatty material covees axon, insulates, speeds up conduction

Sclera- protects eye

Cornea lets light in

Choroid contains pigment, stops light being reflected round eye

Retina tranduces light energy , rods and cones

Optic nerve sends signals to brain

Bright light, pupil constricted. circular muscles contract, radial muscles relax

Dim light, circular muscles relax, radial muscles contract, pupil dilates

Example of reflex action

Blind spot, brain cancels out

Focusing on distant object, lens flatter, ciliary muscles relax, suspensory pulled tight

Near object, rounded lens, ciliary muscles contract suspensory ligaments slack, lens more rounded

Synapse- gap between two nerves- secret neutrotransmitter, diffuses accross grap, attatches to second neurone, starts of impulses, then broken down by enzyme

Cerebrum largest part of brain has 3 functions

 sensory areas- receive and process info

motor areas- voluntary actions orginate

Higher activites