Neurons & Neurotransmission

Question 1

Explain the steps of neurotransmission. [4 marks]

Answer 1

1 > An electrical impulse travels down the pre-synaptic neuron.

2 > The electrical impulse stimulates the vesicles containing neurotransmitters to migrate towards the pre-synaptic membrane.

3 > The vesicles release the neurotransmitters into the synaptic cleft via exocytosis.

4 > The neurotransmitters diffuse across the synaptic cleft and attach to specific protein receptor sites on the post-synaptic membrane.

5 > This then activates the post-synaptic neuron.

6 > Once the receptors on the post-synaptic membrane have been activated, they produce either an excitatory or inhibitory effect.

7 > If the neurotransmitter is excitatory it makes the post-synaptic neuron more likely to fire as there is an increase in positive charge.

If the neurotransmitter is inhibitory it makes the post-synaptic neuron less likely to fire as there is an increase in negative charge.

8 > The net effect of the neurotransmitters is then calculated through a process of summation.

Question 2

What are the 3 main types of neurons?

Answer 2

Sensory

Relay

Motor

Question 3

How would you identify neurons based on their structures on a diagram?

Answer 3

SENSORY =
has a receptor cell attached onto the dendrites.
the cell body is found attached to the axon & myelin sheath.
Long dendrites, Short axons (LS).

RELAY =
the most normal looking neuron.
NO myelin sheath.
Short dendrites, Short axons (SS)

MOTOR =
looks like it’s holding TNT at the pre-synaptic terminal.
very long dendrites.
Short dendrites, long axon (SL)

Question 4

What are sensory neurons and where are they found? Give examples.

Answer 4

Nerve cells that picks up info from sense receptors (e.g. skin), and carry nerve impulses TO the CNS (spinal cord and brain)

Found in receptors, E.G.
eyes, ears, tongue, skin.

Carry msgs from PNS to CNS.

Question 5

What happens when nerve impulses carried by sensory neurons reach the brain and spinal cord?

Answer 5

In the BRAIN =
impulses are TRANSLATED into ‘sensations’, such as vision, hearing, taste, touch.

In the SPINAL CORD =
some neurons stop at the spinal cord - allowing for quick REFLEX actions.

Question 6

What are relay neurons and where are they found?

Answer 6

Nerve cell that passes msgs and carry nerve impulses within the CNS (brain and spinal cord).

Found between SENSORY neurons (input) and MOTOR neurons (output / (response).

Relay neurons allow sensory & motor neurons to communicate.

Question 7

What are motor neurons and where are they found?

Answer 7

Nerve cells that carry messages from the CNS to the muscles for muscle movement.

1 = Motor neurons stimulated.
2 = Releases neurotransmitters that bind to receptors on muscles.
3 = Triggers a response - leads to movement.

Carry messages from CNS to muscles and glands.

Question 8

What are neurons?

Answer 8

A type of nerve cell that involved in generating and transmitting electrical impulses to communicate.

(There are 100 billion of them in the human body, with 80% ‘living’ in the brain) extra.

Question 9

Where does each type of neuron carry information to and from?

Answer 9

Sensory =
From PNS to CNS.

Relay =
Within CNS, between sensory neurons & motor neurons.

Motor =
From CNS to muscles & glands.

Question 10

Describe the function of the cell body (soma) of a neuron. [1 mark]

Answer 10

Nucleus containing genetic material (DNA).

Referred to as the ‘control centre’ bc of nucleus.

Question 11

Describe the structure and function of the axon. [2 marks]

Answer 11

Axon - a long slender fibre covered in myelin sheath.

Carries nerve impulses in the form of electrical signals (aka action potential) FROM the cell body TO the axon terminals.

Question 12

Describe the structure and function of myelin sheath. [1 mark]

Answer 12

Fatty layer which insulates the axon so electrical impulses travel faster along the axon.

Speeds up signal.

Question 13

Describe the structure and function of the axon terminal. [2 marks]

Answer 13

Connects a neuron to other neurons (or directly to organs) using a process called SYNAPTIC TRANSMISSION.

End of axon forming part of the synapse.

Question 14

Describe the structure and function of dendrites. [1 mark]

Answer 14

Connected to the cell body.
Receive signals from other neurons (or sensory receptor cells).

Question 15

Describe how electrical transmission / an impulse occurs in neurons.

Answer 15

Resting state =
Inside has a negative charge compared to outside.

When it fires =
Changes to a positive charge which causes an action potential (electrical impulse)

Question 16

Explain what is meant by a synapse [1 mark]

Answer 16

The small gap between 2 neurons that allows signals to pass between them.

Question 17

What is action potential?

Answer 17

When info is passed down the axon of a neuron as an electrical impulse.

Question 18

What are neurotransmitters and where are they found?

Answer 18

A brain chemical released across the synaptic cleft by a neuron, and picked up by the next neuron.

Can cause excitation or inhibition when it fuses with the post-synaptic neuron.

Found in synaptic vesicles.

Question 19

What happens when neurotransmitters bind onto the receptor sites of the post-synaptic neuron?

Answer 19

The receptor sites become activated and the neurotransmitters cause either…

EXCITATION
or
INHIBITION.

Question 20

What is meant by excitation?

Answer 20

When a neurotransmitter binding with a receptor on the next neuron…

INCREASES the likelihood that an electrical impulse will be fired in the next neuron.

Question 21

What is meant by inhibition?

Answer 21

When a neurotransmitter binding with a receptor on the next neuron…

DECREASES the likelihood that an electrical impulse will be fired in the next neuron.

Question 22

Explain what is meant by ‘excitatory post-synaptic potential’ [1 mark]

Answer 22

When an excitatory neurotransmitter binds onto the post-synaptic receptors and causes an electrical charge, making the post-synaptic cell MORE likely to fire an impulse.

Question 23

Explain what is meant by ‘inhibitory post-synaptic potential’ [1 mark]

Answer 23

When an inhibitory neurotransmitter binds onto the post-synaptic receptors, making the post-synaptic cell LESS likely to fire an impulse.

Question 24

Give an example of an excitatory and inhibitory neurotransmitter.

Answer 24

EXCITATORY neurotransmitter = noradrenaline

INHIBTORY neurotransmitter = GABA

Question 25

What is seratonin?

Answer 25

A neurotransmitter that is a brain chemical responsible for mood stability.

Question 26

What is meant by the ‘reuptake of neurotransmitters’?

Answer 26

When a neurotransmitter in the synaptic cleft that has been used is broken down by enzymes and reabsorbed by the presynaptic neuron through re-uptake proteins.

Question 27

Describe how excitation and inhibition interact.

Answer 27

Excitatory neurotransmitters increase the postsynaptic neuron’s POSITIVE charge and make it MORE likely to fire.

Inhibitory neurotransmitters increase the postsynaptic neuron’s NEGATIVE charge and make it LESS likely to fire.

Question 28

What is meant by summation?

Answer 28

If there are more excitatory signals than inhibitory signals, this causes an electrical impulse to be fired.

Question 29

What is the spinal cord protected by?

Answer 29

The spinal column

Question 30

What is the brain protected by?

Answer 30

The skull

Question 31

How do neurons communicate?

Answer 31

Via electrical signals called nerve impulses, also known as action potential.

Question 32

Explain the steps of neurotransmission (uplearn) [4 marks]

Answer 32

1 > Nerve impulse arrives at the pre-synaptic terminal , causing the synaptic vesicles to travel down to the pre-synaptic membrane.

2 > Pre-synaptic membrane and synaptic vesicle fuse.

3 > This causes the neurotransmitters to be released into the synaptic cleft.

4 > Neurotransmitters diffuse across the synaptic cleft, and fuse with the receptor sites on the post-synaptic terminal.

This causes either excitatory post-synaptic potential (EPSP) or inhibitory post-synaptic potential (IPSP)

Question 33

Potential is another word for…

Answer 33

Voltage

Question 34

Using your knowledge of different types of neurotransmitters, explain what effects acetylcholine will have on neural transmission

Answer 34

Acetylcholine is an excitatory neurotransmitter.

This means that it allows positively charged particles to enter the post-synaptic neuron, creating a positive electrical charge, making a nerve impulse more likely to occur.

Question 35

What are the structures of sensory, relay and motor neurons?

Answer 35

Sensory = Long dendrite, Short axon - long fingers to receive information

Relay = Short dendrite, Short axon

Motor = Short dendrite, Long axon - opposite of sensory