Paper 2- Neurons and Synaptic Transmission- Biopsychology

Question 1

Neuron

Answer 1

The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals.

Question 2

Sensory neuron

Answer 2

Carry messages from the peripheral nervous system and the central nervous system. Short axons and long dendrites.

Question 3

Relay neuron

Answer 3

These connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons.

Question 4

Motor neuron

Answer 4

These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.

Question 5

Cell body

Answer 5

Known as the factory of the neuron. Contains the nucleus and produces all of the necessary proteins that the neuron requires in order to function.

Question 6

Nucleus

Answer 6

Contains the genetic material within the neuron.

Question 7

Dendrites

Answer 7

Branch like feature that protrude from the cell body. Carry nerve impulses from neighbouring neurons towards the cell body.

Question 8

Axon

Answer 8

Carries the electrical impulse from the cell body and goes down the length of the neuron. Covered in the myelin sheath.

Question 9

Myelin sheath

Answer 9

Fatty layer, surrounds and protects the axon. Helps to speed up the electrical transmission of an impulse.

Question 10

Nodes of ranvier

Answer 10

These are the gaps between the myelin sheath. Their purpose is to speed up the transmission of the impulse, by forcing it to ‘jump’ across the gaps along the axon.

Question 11

Terminal Buttons

Answer 11

Located at the end of the axon, they communicate with the next neuron that is on the other side of the synaptic clef.

Question 12

Sensory neuron- role, location, length of axon and dendrite.

Answer 12

Carry nerve impulses from sensory receptors to the spinal cord and brain = from the PNS to the CNS

Receptors of sensory neurons are located on or near the body’s surface

length of axon- short
length of dendrite- long

Question 13

Relay neuron- role, location, length of axon and dendrite.

Answer 13

Allows sensory and motor neurons to communicate with each other. Most common type of neuron.

Location- brain, spinal chord and visual system.

Length of axon- short
length of dendrite- short.

Question 14

Motor- role, location, length of axon and dendrite.

Answer 14

Carry nerve impulses from the spinal chord and brain to the effectors (muscles and glands)- from the CNS to the PNS

Question 15

What happens during synaptic transmission?

Answer 15

An electrical impulse travels down a pre-synaptic neuron, along the axon and to the terminal buttons of that neuron.

When the electrical impulse gets to the terminal branches it stimulates the synaptic vesicles. The synaptic vesicles contain neurotransmitters which are chemicals.

The neurotransmitters are released from the synaptic vesicles and travel across the synapse. This is when the electrical impulse has been changed to a chemical impulse.

The neurotransmitters cross the synapse to get to the dendrites of the post-synaptic neuron.

There are receptors on the dendrites of the post-synaptic neuron. The receptors are known as the lock, in the lock and key theory.

If the neurotransmitters (the key) are the correct shape, then they can fit into the receptors on the dendrites of the post-synaptic neuron.

The connection between the neurotransmitter and the receptor can cause an electrical impulse to be created in the dendrites of the post-synaptic neuron.

However, this depends on whether the neurotransmitters are excitatory or inhibitory.

If the neurotransmitter is excitatory it is more likely that an electrical impulse will travel down the post-synaptic neuron and the process can begin all over again.

The neurotransmitter however does not always fit into the receptors. If this is the case, there will be no electrical impulse created in the second neuron.

This above process is known as synaptic transmission.

Question 16

What are neurotransmitters?

Answer 16

Several dozen types of neurotransmitters have been identified in the brain, spinal cord and glands.

Each neurotransmitter has its own specific molecular structure that fits perfectly into a post-synaptic receptor site, similar to a lock and key

Question 17

Neurotransmitters can have one of two effects?

Answer 17

Increase the likelihood of a neuron firing – excitation

Decrease the likelihood of a neuron firing – inhibition

Question 18

Firing of neurons- excitatory and inhibition

Answer 18

Excitatory neurotransmitters, for example adrenaline, cause excitation of the post-synaptic neuron by increasing its positive charge and making it more likely to fire.

Inhibitory neurotransmitters, for example serotonin, cause inhibition in the post-synaptic neuron. The neuron becomes negatively charged and less likely to fire.

Question 19

What is summitation?

Answer 19

Weather a neuron is fired or not is decided through summation.

The excitatory and inhibitory influences are summed up.
If the net effect on the postsynaptic neuron is inhibitory, then the post-synaptic neuron is less likely to fire.
If the net effect is excitatory, it is more likely to.
The action potentials (nerve impulses) of the postsynaptic neuron are only triggered if the sum of the excitatory and inhibitory signals at any one time reaches the threshold.

Question 20

Drugs and synaptic transmission?

Answer 20

Drugs can have one of two impacts on synaptic transmission:

Increase the amount of neurotransmitter – block the reuptake channels

Decrease the amount of neurotransmitter – block the receptors.

e.g. Antipsychotics drugs in schizophrenia block the receptors to prevent dopamine binding – too much dopamine is thought to cause schizophrenia.