nervous system

Question 1

how does information passes across a synapse

Answer 1

• a chemical is released from one neuron and passes/diffuses across the synapse to the next neuron to stimulate an electrical impulse

Question 2

describe the reflex arc caused by a bright light shining in somebody’s eye

Answer 2

• the stimulus (bright light) is detected by a receptor in the retina of the eye
• the receptor generates a nervous impulse
• the impulse passes along the sensory neuron to the relay neuron located in the CNS
• the impulse passes along the motor neuron to the effector (the muscles in the iris) which bring about a response
• the response is the muscles contract and reduce the amount of light entering the eye

Question 3

what is the function of the iris

Answer 3

the muscles contract and relax to control the amount of light entering the eye

Question 4

what is the function of the suspensory ligaments and ciliary muscles

Answer 4

to contract and relax to focus the lens

Question 5

explain how a person’s eye could adjust to form a clear image of a nearer object

Answer 5

• ciliary muscles contracts so they a smaller diameter
• so suspensory ligaments slacken
• so the lens thickens
• and a thicker lens is more convergent ( refracts light inwards more)
• so the light rays are focused on the retina

Question 6

explain why a long sighted person has difficulty seeing near objects clearly

Answer 6

• eyeball is too short/lens can’t be thickened enough so light focuses behind the retina

Question 7

describe ow spectacle lenses can correct long sightedness

Answer 7

• the lens is convex which means light rays are refracted inwards more so light rays focus on the retina

Question 8

how does the eye respond to dim light

Answer 8

• in dim light the circular muscles in the iris relax and the radial muscles contract which causes the pupil to dilate

Question 9

what is hyperopia and myopia and how can they be fixed

Answer 9

• hyperopia = long sightedness, when light does not focus on the retina, it focus In front of it as lens refracts light inwards too much. fixed with convex lens
• myopia = short sightedness, when light focuses behind retina as lens is to thin and doesn’t refract light enough. fixed with concave lens