The Structure of Neurons and Synaptic Transmission

Question 1

The Cell Body

Answer 1

Includes a nucleus contains all the genetic material of the cell

Question 2

Dendrites

Answer 2

Branch like structures that project from the cell body. They carry impulses from other neurons towards the cell body

Question 3

Axon

Answer 3

Carries the impulses away from the cell body down the length of the neuron

Question 4

Myelin Sheath

Answer 4

Covers and protects the axon, speeding up electrical impulse

Question 5

Nodes of Ranvier

Answer 5

Segmented gaps in the myelin sheath that speed up transmission of impulse by forcing it to jump across gaps along the axon

Question 6

Terminal Buttons

Answer 6

At the end of the axon, communicate with the next neuron in the chain across a synaptic gap by using neurotransmitters

Question 7

Sensory Neuron

Answer 7

• Carries messages from the PNS to the brain and spinal cord (CNS)
• Long dendrites and short axons
• Cell body on the side

Question 8

Relay Neuron

Answer 8

• Transfers messages from sensory neurons to other interconnecting neurons or motor neurons
• No myelin sheaths
• Short dendrites and short or long axons

Question 9

Motor Neuron

Answer 9

• Carries messages from the CNS to effectors such as muscles and glands
• Main cell body at the top
• Short dendrites and long axons

Question 10

The process of Synaptic Transmission (simplified)

Answer 10

1. Information passed down the neuron as an action potential
2. Once the action potential reaches the terminal buttons it must cross the synaptic gap/cleft
3. When the action potential reaches the synaptic vesicles that contains neurotransmitters the neurotransmitters are released and convert the electrical impulse/action potential into a chemical message in order to cross the gap
4. As the NT diffuses across the gap it fuses onto receptors on the dendrites of the postsynaptic neuron
5. Produces either an inhibitory or excitatory effect
6. Summation

Question 11

What is a neurotransmitter?

Answer 11

Chemicals that are released from a synaptic vesicle into the synapse by neurons which allow them to communicate with each other and relay messages to different areas/structures of the brain

Question 12

Examples of excitatory NTs

Answer 12

• Glutamate
• Acetylcholine
• Epinephrine
• Histamine
• Dopamine

Question 13

Examples of inhibitory NTs

Answer 13

• GABA

- Serotonin

Question 14

What is summation

Answer 14

The excitatory and inhibitory influences are summed. If the net effect on the post synaptic neuron is inhibitory, the neuron will be less likely to fire and if the net effect is excitatory the neuron will be more likely to fire

Question 15

Reflex Arc

Answer 15

• In a reflex arc, like the knee jerk reflex, a stimulus, such as a hammer hitting the knee, is detected by sense organs in the PNS which conveys a message along a sensory neuron
• The message reaches the CNS where it connects with a relay neuron
• This transfers the message to a motor neuron
• This then carries the message to an effector such as a muscle which causes the muscle to contract and hence the knee to move or jerk