Lesson 2 - Neurons

Question 1

What are neurones?

Answer 1

Neurones are specialised nerve cells which move electrical impulses to and from the CNS

Question 2

What are the 12 parts to a neuron?

Answer 2

Cell Body
Nucleus 
Dendrites
Axon
Synapse
Synaptic knob
Synaptic Cleft
Myelin Sheath
Schwann Cells 
Nodes of Ranvier
Neurotransmitters 
Receptor sites

Question 3

What is a cell body?

Answer 3

The cell body is the control centre of the neuron.

Question 4

What is a nucleus?

Answer 4

The nucleus contains the genetic material of the cell

Question 5

What are dendrites?

Answer 5

Dendrites are branch-like structures which protrude from the cell body which recieve an electrical impulses (action potentials) from sensory receptors or a previous neuron.

Question 6

What is an axon?

Answer 6

An axon is a long fibre which carries the electrical from the cell body to the axon terminal

Question 7

What is the synapse?

Answer 7

The ending of a neuron

Question 8

What is the synaptic knob?

Answer 8

The swelling at the end of the synapse which contained the vesicles.

Question 9

What are vesicles?

Answer 9

Vesicles release neurotransmitters

Question 10

What is the synaptic cleft?

Answer 10

The synaptic cleft is the microscopic gap between the presynaptic neuron and the postsynaptic neuron.

Question 11

What is the myelin sheath?

Answer 11

This is the insulating fatty layer that protects the axon and speeds up the transmission of an electrical impulse.

Question 12

What are Schwann Cells?

Answer 12

Schwann cells make up the myelin sheath

Question 13

What are the Nodes of Ranvier?

Answer 13

These are the gaps in the myelin sheath which speed up the transmission of electrical impulses along the axon (impulse is forced to jump over gaps in the axon which speed up the transmission).

Question 14

What are neurotransmitters?

Answer 14

These are chemicals within the synaptic knob that are released from the presynaptic neuron and are transmitted to the postsynaptic neuron via the synaptic cleft

Question 15

What are receptor sites?

Answer 15

Receptor sites are proteins on the surface of each cell. Their function is to act as receivers to the messages of the chemical molecules. The receptor site is like a lock which is capable of receiving particular types of chemical messenger keys.

Question 16

Where are sensory neurons located
Where are relay neurons located?
Where are motor neurons located?

Answer 16

Sensory receptors
The CNS
The CNS but project their axons outside of the CNS

Question 17

What is the function of a sensory neuron? How does this happen?

Answer 17

Sensory neurons carry electrical impulses from sensory receptors to the CNS via the PNS.
This is achieved by the sensory neurons converting information from sensory receptors into electrical impulses (action potentials). When these action potentials reach the CNS, they are converted into sensations so that the body can respond appropriately (conscious control).

Question 18

What do sensory neurons do when a reflex action occurs?

Answer 18

The sensory neurons will convert information from sensory receptors into action potentials which travel to the SPINAL CORD ONLY - due to reflex actions being involuntary actions under unconscious control, there is no thinking involved and no need for the full CNS i.e. the brain, meaning that these actions occur very quickly.

Question 19

What is the function of a relay neuron? How does this happen?

Answer 19

Relay neurons carry electrical impulses from one part of the CNS to another (relay neurons connect sensory and motor neurons together so that they can communicate with each other).

Question 20

How does the function of relay neurons differ between conscious control and reflex actions?

Answer 20

During conscious control, relay neurons are involved in helping the brain respond to a situation.
In a reflex arc, relay neurons in the spinal cord are involved in the analysis of a sensation and decided how to respond WITHOUT waiting for the brain to process the pain.

Question 21

What is the function of a motor neuron? How does this happen?

Answer 21

Motor neurons carry electrical impulses (action potentials) from relay neurons to the glands and muscles (effectors) via long axons. Motor neurons stimulate the release of neurotransmitters which bind to effectors on muscles to trigger a response which leads to movement (muscles either contract or relax).

Question 22

How do the structures of sensory, relay and motor neurons differ?

Answer 22

Sensory - has a cell body
Relay - no axon
Motor - no cell body
See sheets for more detail