Neurones, Reflexes and Synapses

Question 1

what are nerve cells called?

Answer 1

neurones

Question 2

what are the three types of neurones?

Answer 2

• sensory neurones
• relay neurones
• motor neurones

Question 3

what happens once a receptor detects the stimulus?

Answer 3

electrical impulses from receptors pass along sensory neurones until they reach the brain and spinal cord (CNS). impulses pass to relay neurones in the CNS. the impulse is then passed to effectors (muscles or glands) along motor neurones.

Question 4

in a motor neurone, what is a nucleus?

Answer 4

contains all the genetic information of the cell

Question 5

in a motor neurone, what is a dendrite?

Answer 5

tree light projections which connect to different neurones - one neurone can connect to many other neurones

Question 6

in a motor neurone, what is a cell body?

Answer 6

the main section of the cell - contains the nucleus

Question 7

in a motor neurone, what is an axon?

Answer 7

the long section - electrical impulses travel long distances through the axon

Question 8

in a motor neurone, what is the myelin sheath?

Answer 8

insulates the axon and speeds up the transmission of the impulse

Question 9

what are reflexes?

Answer 9

reflexes are automated actions which do not involve the brain - they are very fast actions

Question 10

what three neurones do reflexes involve?

Answer 10

• sensory neurone
• relay neurone
• motor neurone

Question 11

what is a reflex arc?

Answer 11

the movement of the impulse from receptor to effector

Question 12

what are the steps of a reflex arc?

Answer 12

1. the receptors detect the stimulus (change in temperature) and send an impulse along the sensory neurone.
2. the sensory neurone passes the impulse the spinal cord to a relay neurone. the gap between neurones is called a synapse. the relay neurone then passes the impulse through the spinal cord to a motor neurone.
3. the motor neurone causes the effector to respond accordingly

Question 13

what is a synapse?

Answer 13

the small gap between two neurones - the signal needs to cross this gap to continue on its journey to/from the CNS

Question 14

what happens to the impulse when it reaches the synapse?

Answer 14

1. an electrical impulse travels along an axon
2. this triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters
3. these chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the next neuron
4. the receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron - this stimulates the second neuron to transmit the electrical impulse