13- nervous system

Question 1

what are the parts of the nervous system

Answer 1

1. CNS: brain and spinal chord
2. PNS: neurones

Question 2

how does the CNS coordinate a response

Answer 2

1. sensory receptors detect a change in the environment
2. the information is converted into electrical impulses
3. the brain coordinates a response as the information travels through sensoray neurones to relay neurones
4. CNS sends information to motor neurones to an effector gland to respond accordingly

Question 3

what is a synapse

Answer 3

junction between 2 neurones

Question 4

how are neurones connected in a synapse?

Answer 4

1. Neurones before the synapse have vesicles to release neurotransmitter
2. The post synaptic neuron has receptor proteins to receive neurotransmitter
3. after the neurotransmitter is transferred, an electrical impulse is transferred

Question 5

what are reflex actions

Answer 5

1. Rapid automatic actions that are not done by the conscious part of the brain
2. Response of effector is coordinated by a stimuli

Question 6

explain the reflex arc

Answer 6

1. nerve impulse goes through the unconscious part of the brain
2. impulses are sent along sensory neurones if a stimuli is detected by a receptor
3. impulses are sent across the synapse to relay neurones
4. Neurones travel along motor neurones to effector neurones
5. Muscle contracts

Question 7

identify parts of the eye and identify their functions

Answer 7

1. Cornea: outer most layer of the eye, refracts light
2. The IRIS: contains muscles that allow it to control the diameter of the PUPIL
3. The LENS focuses the light onto the RETINA
4. The OPTIC NERVE: carries impulses from the receptors on the retina to the brain.
5. BLIND SPOT: there aren’t any light receptors
6. The FOVEA: is a specific area of the retina which contains cone cells

Question 8

what are rods and what are their functions

Answer 8

1. found in the peripheral parts
2. very sensitive to light, so work well in dim light
3. one kind of rod, which gives information in black and white

Question 9

what are cones and what are their functions

Answer 9

1. Cones are mainly found packed together in the fovea.
2. Cones are less sensitive to light than rods
3. There are three kinds of cones which give information in different colours for colour vision.

Question 10

what is The Pupil Reflex

Answer 10

1. When light receptors in the eye detect a high light intensity, a reflex action is triggered that reduces the diameter of the pupil. This reduces the amount of light that can enter the eye.
2. control pupil diameter — the radial and circular muscles.

Question 11

how to change the size of the pupli

Answer 11

To make the pupil wider, the radial muscles in the iris contract and the circular muscles relax.

Question 12

how do eyes focus on near objects

Answer 12

1. ciliary muscles contract
2. suspensoray ligament slackens
3. lens becomes fat
4. refraction increases