B1d - the nervous system Flashcards Preview

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Flashcards in B1d - the nervous system Deck (17):

Name the main parts of the eye and uses (7)

Cornea -refracts light

Iris - controls how much light enters pupil


Lens - focuses light on to retina

Retina - contains light receptors, some sensitive to light of different colours

Optic nerve - carries impulses to the brain

Blind spot


Describe the pathway of light through the eyeball(2)

Cornea refracts light into the eye

The lens also refracts the light, focusing it onto the retina


What is accommodation

Changing the shape of the elastic lens to focus light from distant or near objects


How does the eye focus light from near objects(3)

The ciliary muscle contracts

The suspensory ligaments slackens

The lens becomes a more rounded shape, so light is refracted more


How does the eye focus light from distant objects(3)

The ciliary muscle relaxes

The suspensory ligaments to pull tight

This pulls the lens into a less rounded shape so light is refracted less


Advantages and disadvantages of binocular vision(4)

Better judgement of distance
-compares the images from each eye
- the more similar the images, the further away the object

Narrower field of view


Explain a cause of red-green colour blindness

Caused by the lack of specialised cells in the retina


What causes long-sightedness

Lens is the wrong shape and doesn't bend the light enough or the eyeball is too short


What causes short-sightedness

The lens is the wrong shape and bends the light too much or the eyeball is too long


How can long/short sight be corrected(3)

For long-sighted people - Can use glasses or contact lenses with a convex lens

For short-sighted people - can use glasses or contact lenses with a concave lens

An alternative to glasses/contact lenses is to have corneal laser surgery


Name and locate the parts of a motor neurone(3)

Cell body - surrounding the nucleus

Axon- extends from the cell body

Sheath - surrounds the axon


Explain how neurones are adapted to their function

Branched endings (dendrites) so they can connect with lots of other neurones

Sheath along the axon that acts as an electrical insulator, which speeds up the electrical impulse

Long, which also speeds up the impulse
-connecting with another neurone slows the impulse down, so 1 long neurone is much quicker than lots of short ones joined together


Describe a reflex arc(7)

Stimulus → receptor → sensory neurone → central nervous system → motor neurone → effector → response.


Describe the path taken by a spinal reflex(3)

1. A stimulus is detected by a receptor cell, which synapses with a sensory neurone

2. The sensory neurone carries the impulse from site of the stimulus to the central nervous system (spinal cord), where it synapses with an relay neurone

3. The relay neurone synapses with a motor neurone, which carries the nerve impulse out to an effector, such as a muscle, which responds by contracting


Which part of the neurone do nerve impulses pass along



What is the gap between neurones called



Describe what happens in a synapse(3)

1. An impulse triggers the release of a transmitter substance in a synapse

2. Transmitter substance diffuses across the synapse

3. Transmitter substances binds with receptor molecules in the membrane of the next neurone causing the impulse to continue