biology specification 13.6 – 13.8 13.6 nervous coordination the mammalian eye rods and cones the...

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Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs and synapses 13.7 Analysis and integration Brain and cerebral hemispheres Autonomic nervous system 13.8 Muscles are effectors which enable movement to be carried out Antagonistic muscle action Muscle structure Muscle contraction

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Page 1: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Biology Specification 13.6 – 13.8

13.6 Nervous coordination

The mammalian eye

Rods and Cones

The nerve impulse

Synapses and synaptic transmission

Drugs and synapses

13.7 Analysis and integration

Brain and cerebral hemispheres

Autonomic nervous system 13.8 Muscles are effectors

which enable movement to be carried out

Antagonistic muscle action

Muscle structure

Muscle contraction

Page 2: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Section through a mammalian eyeball

Sclera

Choroid RetinaVitreous humour

Blind spot

Optic nerve

Fovea (yellow spot) Ciliary muscle

Iris

Cornea

Aqueous humour

Lens

Suspensory ligaments

Page 3: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Reflex Action and Antagonistic Muscle Action

Circular muscles contract

Radial muscles relax

Pupils constricted

Radial muscles contract

Circular muscles relax

Pupils dilated

Why is it important that the amount of light entering the eye is regulated?

Page 4: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Accommodation

Accommodation is the ability to focus objects which are at different distances from the eye.

Focusing occurs via refraction – the change in the speed of light as it passes from one medium into another. Most refraction occurs at the interface between air and the cornea. The lens refracts the light only slightly

Light from a distant object

Most Refraction at air-cornea interface

Limited refraction at aqueous humour-lens interface

Page 5: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Light Rays from a near object

How does the eye alter the pathways of light rays?

Muscle action and lens shape in focusing distant objects:

Page 6: Biology Specification 13.6 – 13.8 13.6 Nervous coordination The mammalian eye Rods and Cones The nerve impulse Synapses and synaptic transmission Drugs

Muscle action and lens shape in focusing near objects:

• Cornea refracts most light

• Lens is elastic and changes its shape giving it a variable refractive index

• Ciliary muscles and suspensory ligaments bring about the change in shape of the lens

•As we age the elasticity of the lens decreases