Neurons & Synaptic Transmission

Question 1

What are the functions of neurons?

Answer 1

Transmit signals electrically & chemically to provide the nervous system with communication

Question 2

What are the 3 main types of neurons?

Answer 2

Sensory, relay & motor neurons

Question 3

What is the structure & function of sensory neurons?

Answer 3

• long dendrites & short axons
• carry messages from PNS to CNS

Question 4

What is the structure & function of relay neurons?

Answer 4

• short dendrites & short axons
• connects sensory to motor neurons or other relay neurons

Question 5

What is the structure & function of motor neurons?

Answer 5

• short dendrites & long axons
• connects CNS to effectors (muscles and glands)

Question 6

What are the structures that make up a neuron?

Answer 6

• cell body
• dendrites
• axon
• myelin sheath
• terminal branches of axon

Question 7

What is the function of the cell body?

Answer 7

Includes the nucleus which contains the cell’s genetic material

Question 8

What is the function of the dendrites?

Answer 8

Carries electrical impulses towards cell body

Question 9

What is the function of the axon?

Answer 9

Carries electrical impulses away from cell body to other neurons, muscles or glands

Question 10

What is the function of the myelin sheath?

Answer 10

Fatty layer that protects axon & speeds up electrical transmission of impulses

Question 11

What is the function of the terminal branches of the axon?

Answer 11

Communicates with the next neurons in the chain across the synapse.

Question 12

How is an electrical transmission that travels down the axon created?

Answer 12

• When a neuron is in its resting state the cell is negative compared to inside
• As neuron is activated by stimulus the inside of the cell becomes positive for a split second causing action potential to occur

Question 13

How does signals within & between neurons differ?

Answer 13

• signals within neurons are electrical
• signals between neurons are chemical

Question 14

What is synaptic transmission?

Answer 14

The process where neighboring neurons communicate with each other by sending chemical messages across their synapses

Question 15

What are neurotransmitters?

Answer 15

Chemicals that diffuse across the synapse to the next neuron in the chain

Question 16

What happens after the neurotransmitter crosses the synapse?

Answer 16

• taken up by postsynaptic receptor sites (dendrites of next neuron)
• chemical message converted back to electrical impulse
• process of transmission starts again

Question 17

How do neurotransmitters differ?

Answer 17

• They have their own specific molecular structure that fits perfectly into a postsynaptic receptor site
• Have specialist functions

Question 18

What are the 2 types of effects neurotransmitters can have on another neuron?

Answer 18

Excitatory and inhibitory

Question 19

What is excitation?

Answer 19

When a neurotransmitter (e.g. adrenaline) increases positive charge of postsynaptic neuron which increases the likelihood that the neuron will fire & pass on electrical impulse

Question 20

What is inhibition ?

Answer 20

When a neurotransmitter (e.g. serotonin) makes postsynaptic neuron more negative decreasing the likelihood that neuron will fire & pass on electrical impulse

Question 21

What is summation?

Answer 21

The process where whether a postsynaptic neuron is fired is decided

Question 22

How are the excitatory & inhibitory influences summed?

Answer 22

• If net effect on neuron is excitatory the neuron is more likely to fire
• If net effect on neuron is inhibitory the neuron is less likely to fire

Question 23

When is the action potential of the postsynaptic neuron triggered?

Answer 23

Only if the sum of the excitatory & inhibitory signals at any one time reaches the threshold