Coordination and Response

Question 1

CNS

Answer 1

central nervous system, consisting of the brain and spinal cord

Question 2

PNS

Answer 2

peripheral nervous system, consisting of the nerves outside the brain and spinal cord

Question 3

nervous system

Answer 3

coordinates its actions and sensory information by transmitting signals to and from different parts of its body, while also regulating the body functions

Question 4

simple reflex arc

Answer 4

receptor, sensory neurone, relay neurone, motor neurone and effector

Question 5

reflex action

Answer 5

a means of automatically and rapidly integrating and
coordinating stimuli with the responses of effectors (muscles and glands

Question 6

synapse

Answer 6

a junction between two neurones. synapses ensure that impulses travel in one direction only

Question 7

structure of a synapse

Answer 7

presence of vesicles containing neurotransmitter molecules, the synaptic gap and receptor proteins

Question 8

events at a synapse

Answer 8

(a) an impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap

(b) the neurotransmitter molecules diffuse across the gap

(c) neurotransmitter molecules bind with receptor proteins on the next neurone

(d) an impulse is then stimulated in the next neurone

Question 9

sense organs

Answer 9

groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

Question 10

function of each part of the eye

Answer 10

(a) cornea – refracts light

(b) iris – controls how much light enters the pupil

(c) lens – focuses light on to the retina

(d) retina – contains light receptors, some sensitive to light of different colours

(e) optic nerve – carries impulses to the brain

Question 11

the pupil reflex

Answer 11

in bright light, the pupil restricts to prevent excessive light from entering and damaging the retina.

in dim light, the pupil dilates to allow light to enter the eye so the person can see

Question 12

cones

Answer 12

found densely in the fovea.
three different kinds of cones, absorbing light of different colours, for colour vision

Question 13

rods

Answer 13

not found in fovea.
allows black and white vision in dim light

Question 14

bright light

Answer 14

• circular muscles contract
• radial muscles relax
• pupil constricts

Question 15

dim light

Answer 15

• circular muscles relax
• radial muscles contract
• pupil dilates

Question 16

accommodation

Answer 16

the adjustment of the lens of the eye, so that clear images of objects at different distances are formed on the retina

Question 17

distant

Answer 17

• ciliary muscles relax
• suspensory ligaments become taut
• lens become thinner and less convex, focal length increases
• photoreceptors are stimulated
• nerve impulses produced are transmitted via optic nerve to the brain
• brain interprets the impulses and the person sees the distant object

Question 18

near

Answer 18

• ciliary muscles contract
• suspensory ligaments slacken
• lens become thicker and more convex, focal length decreases
• photoreceptors are stimulated
• nerve impulses produced are transmitted via optic nerve to the brain

-brain interprets the impulses and the person sees the near object