Reflex arc, synapse and eye

Question 1

List the 3 types of neurones

Answer 1

• sensory
• relay
• motor

Question 2

state the reflex pathway in order

Answer 2

• stimulus
• receptor
• sensory neurone
• relay neurone
• motor neurone
• effector
• response

Question 3

label a synapse

Answer 3

1. axon
2. vesicles
3. neurotransmitter
4. pre-synaptic membrane
5. synaptic cleft
6. post-synaptic membrane
7. neurotransmitter receptors

Question 4

features of a voluntary action

Answer 4

• its slow
• it involves the brain
• it is made consciously

Question 5

features of an involuntary action

Answer 5

• it is automatic, fast and rapid
• it does not involve the brain
• it helps minimise damage to the body

Question 6

how is a reflex carried out

Answer 6

1. a stimulus is detected e.g. by pain, pressure, smell, temperature change
2. sensory neurone sends an electrical impulse to the spinal chord
3. the electrical impulse is passed on to the relay neaurone which connects the sensory and motor neurone
4. motor neurone carries impulses to the effector
5. the appropriate response is made

Question 7

how is an impulse passed across the synapse

Answer 7

1. an impulse arrives at the end of the pre-synaptic neurone
2. vesicles move towards and fuse with the pre-synaptic membrane and neurotransmitters are then released into the synaptic cleft
3. the neurotransmitters diffuse across the synaptic cleft down a concentration gradient
4. neurotransmitters attach to the receptors on the post synaptic membrane
5. this triggers an impulse which travels along the post synaptic neurone
6. the neurotransmitters are recycled or destroyed once an impulse is sent to prevent continued stimulation of the second neurone

Question 8

label an eye

Answer 8

• iris
• pupil
• lens
• ciliary muscle
• suspensory ligament
• cornea
• sclera
• fovea
• optic nerve
• retina

Question 9

state the function of the cornea, iris, lens, retina, pupil, optic nerve

Answer 9

cornea: transparent lens that bends light as it enters the eye
iris: controls how much light enters the eye
lens: transparent disc that can change shape to focus light onto retina
retina: contains light receptor cells- rods and cones
pupil: hole that allows light to enter the eye
optic nerve: sensor neurone that carries impulses

Question 10

describe pupil reflex in dim and bright light

Answer 10

dim light: pupil dilates, circular muscles relaxed, radial muscles contracted - more light enters to improve vision

bright light: pupil constricts, circular muscles contract, radial muscles relax - less light enters to prevent retina damage

Question 11

describe accomodation of near and far objects

Answer 11

far object: lens is thinner, suspensory ligaments pulled tight, ciliary muscles relaxed

near object: lens is thicker, suspensory ligaments slack , ciliary muscles are contracted

Question 12

features of rods

Answer 12

• sensitive to light

- rod cells found all over the retina

Question 13

features of cones

Answer 13

• they distinguish between different colours in bright light
• 3 types - red, blue and green
• found mostly in the fovea