Neurons and Synaptic Transmission

Question 1

Neuron:

Answer 1

Nerve cells that process and transmit messages through electrical and chemical signals.

Question 2

Sensory neurons:

Answer 2

Carry messages from the PNS to the CNS. They have long dendrites and short axons. Found in receptors in the eyes,ears, tongue and skin.

Question 3

Relay neurons:

Answer 3

Connect sensory neurons to the motor or other relay neurons. Short dendrites and short axons. Lay somewhere between sensory input and motor output.

Question 4

Motor Neuron:

Answer 4

Connect the CNS to effectors. Short dendrites and long axons. Found in the CNS.

Question 5

Cell body (soma):

Answer 5

1. Includes a nucleus
2. Contains the genetic material of the cell.

Question 6

Dendrites:

Answer 6

Branch-like structures protrude from the cell body. They carry nerve impulses from neighbouring neurons towards the cell body.

Question 7

Axon:

Answer 7

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

Question 8

Myelin Sheath:

Answer 8

Fatty layer that protects the axon and speeds up electrical transmission of the impulse.

Question 9

Nodes of Ranvier:

Answer 9

Segments of gaps in the myelin sheath, speed up the transmission of the impulse by forcing it to jump across gaps along the axon.

Question 10

Terminal Buttons:

Answer 10

At the end of the axon there are terminal buttons that communicate with the neuron in the chain across a gap known as the synapse.

Question 11

Path of neurons:

Answer 11

1. Stimulus
2. Receptor
3. Sensory neuron
4. Relay neuron
5. Motor neuron
6. Effector
7. Response.

Question 12

What is the process of electrical transmission?

Answer 12

1. When a neuron is in its resting state, inside of the cell is negatively charged compared to the outside.
2. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second.
3. This causes an action potential to occur.
4. This creates an electrical impulse that travels down the axon towards the end of the neuron.

Question 13

Chemical Transmission: Synapses

Answer 13

1. An impulse arrives at the end of the presynaptic neuron.
2. Vesicles move towards and fuse with the presynaptic membrane, this releases neurotransmitters into the synaptic cleft.
3. The neurotransmitters diffuse across the synaptic cleft- down a concentration gradient.
4. Neurotransmitters attach to receptors on the postsynaptic receptor site.
5. This triggers an impulse which travels along the postsynaptic neuron.
6. The neurotransmitters are recycled or destroyed once an impulse is sent.

Question 14

How do neurotransmitters work?

Answer 14

1. Chemicals that diffuse across the synapse.
2. Once it neurotransmitter crosses the gap it is taken up by the postsynaptic receptor sites- dendrites of the next neuron.
3. Then the chemical message is converted back into the an electrical impulse.

Question 15

In what way are neurotransmitters specific?

Answer 15

Each one has its own specific molecular structure that fits perfectly into a post-synaptic receptor site.

Question 16

Synaptic transmission:

Answer 16

The process by which neighbouring neurons communicate with each other by sending chemical messages across the synaptic cleft.

Question 17

Neurotransmitters:

Answer 17

Brain chemicals released from the synaptic vesicles that relay signals across the synapse from one neuron to another.

Question 18

Excitation:

Answer 18

When a neurotransmitter, like adrenaline, increases the positive charge of the postsynaptic neuron. Increases the likelihood that the neuron will fire and pass on the electrical impulse.

Question 19

Inhibition:

Answer 19

When a neurotransmitter, like serotonin, makes the charge of the postsynaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass on the electrical impulse.

Question 20

What is summation and how does it impact excitation and inhibition?

Answer 20

1. Summation is the addition of positive and negative post-synaptic potentials.
2. The potentials are summed and if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to fire.
3. If the net effect is excitatory the neuron will be more likely to fire.

Question 21

What happens if the net effect on the postsynaptic neuron is inhibitory

Answer 21

If the net effect on the postsynaptic neuron is inhibitory the the psn is less likely to fire.

Question 22

What happens if the net effect is excitatory?

Answer 22

1. PSN is less likely to fire.
   2.Momentarily inside becomes positively charged.
2. Once the electrical impulse is created, it travels down the neuron.

Question 23

When is the action potential of the postsynaptic neuron triggered?

Answer 23

If the sum of the excitatory and inhibitory signals at any one time reaches the threshold.