Neurochemistry

Question 1

What is a neuron?

Answer 1

Nerve cells that process and transmit messages through electrical signals
This provides a means of communication around the body so that it can react to the environment

Question 2

What is the cell body?

Answer 2

Part of the cell that contains a nucleus, which contains the genetic material of the cell

Question 3

What are dendrites?

Answer 3

Branch like structures which protrude from the cell body.
These carry nerve impulses from neighbouring neurons towards the cell body

Question 4

What are axons?

Answer 4

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

Question 5

What is the myelin sheath?

Answer 5

Covers the axon which insulates the axon and speeds up electrical transmission

Question 6

What is the nodes of Ranvier?

Answer 6

Regular gaps in the myelin sheath that forces electrical signals to “jump” from node to node for faster transmission

Question 7

What are synaptic terminals?

Answer 7

Axons branch off at many points and at the end of these points are synaptic terminals or synaptic buttons, that communicate with the next neuron in the chain

Question 8

What are the three types of neurons?

Answer 8

• Sensory
• Relay
• Motor

Question 9

What are sensory neurons?

Answer 9

Carry messages from the PNS (receptors) to the CNS

• They have long dendrites and short axons
• Only found in the brain, visual system and spinal cord

Question 10

What are relay neurones?

Answer 10

Connect sensory neurons to motor or other relay neurons

• They have short dendrites and short axons with no myelin sheath
• Relay neurons are mostly in the spinal cord, but some are in the brain

Question 11

What are motor neurons?

Answer 11

Connect the CNS to effectors such as muscles or gland

• They have short dendrites and long axons
• Their cell body lies in the CNS but axons are in the PNS

Question 12

How do neurons communicate with each other?

Answer 12

Within groups called neural networks

Question 13

What is synaptic transmission?

Answer 13

The process by which neighbouring neurons communicate with each other, by sending chemical messages called neurotransmitters across the gap (synapse) that separates them

Question 14

What are the steps of synaptic transmission?

Answer 14

1. When a neuron is activated, the inside of the cell becomes positively charged for a split second, causing an action potential - an electrical impulse that travels down the axon
2. When an electrical impulse reaches the pre-synaptic terminal, it triggers the release of neurotransmitters from tiny sacs called synaptic vesicles
3. Neurotransmitters diffuse across the gap, binding to specific receptors in the membrane of the post - synaptic neurons
4. After activiating receptors, neurotransmitters are broken down by enzymes, or re-absorbed into pre-synaptic neuron

Question 15

Why can impulses only travel in one direction?

Answer 15

• The receptor sites are only found on the post-synaptic membranes
• The vesicles are only in the pre-synaptic neurons
• Diffusion can only occur from high to low concentration

Question 16

What is excitation?

Answer 16

When a neurotransmitter, such as dopamine, increases the posiitve charge if the post synaptic neurone
This increases the likelihood that the neuron will fire and pass on an electrical impulse

Question 17

What is inhibition?

Answer 17

When a neurotransmitter, such as serotonin, increases the negative charge of the post synaptic neuron
This decreases the likelihood that the neuron will fire and pass an impulse

Question 18

What is summation?

Answer 18

The likelihood of the cell firing is determined by the summation of excitatory and inhibitory input
This is because a nerve cell can recieve noth excitatory and inhibitory input

Question 19

What has the increased understanding of how neurotransmitters how done?

Answer 19

Led to development of psychoactive drugs to treat mental disorders

Question 20

What do SSRIs do?

Answer 20

Slow down the reuptake of serotonin after it has crossed the synapse, ensuring that it stays active for longer in the brain