Lesson 2

Question 1

What are dendrites?

Answer 1

long branches and their role is to receive chemical messages from the axon terminals of other neurons and convert them into electrical transmission.

Question 2

What is the soma?

Answer 2

the cell body - is the control centre of the neuron. it contains the nucleus - genetic material of the cell.

Question 3

What are axons?

Answer 3

these carry the electrical impulses (action potential) down the length of the axon.

Question 4

What are the nodes of ranvier?

Answer 4

these are gaps within the myelinated axon and helps speed up the transmission of electrical impulses.

Question 5

what are axon terminals?

Answer 5

terminal buttons are responsible for communicating the message with the next neuron.

Question 6

What is myelin sheath?

Answer 6

they coat the axons which is a protective insulating covering which acts to speed up electrical impulses.

Question 7

What is a sensory neuron?

Answer 7

• carry nerve impulses from sensory receptors (vision , taste, smell) to the spinal cord and the brain.
• they are found in the eyes ears tongue and skin.
• they convert info from sensory receptors into neural impulses.
• info is sent via the PNS to the CNS
• when impulses reach the brain, they are translated into sensations of visual input, heat, pain etc.

Question 8

What is a relay neuron?

Answer 8

• some neurons are neither sensory or motor neurons but sit somewhere in between the sensory input and motor response.
• they lie within the brain and the spinal cord and allow sensory motors neurons to communicate.

Question 9

What is a motor neuron?

Answer 9

• they are located in the CNS.
• motor neurons are used to connect the CNS to effectors, such as muscles to control muscle movement.
• when stimulated they release neurotransmitters that bind to the receptors on the muscles and triggers a response which leads to muscle movement.

Question 10

How does the three neurons work in action?

Answer 10

stimulus
receptor
sensory neuron
relay neuron
motor neuron
effector
response

Question 11

What is a synapse?

Answer 11

a synapse is a small gap between the axon terminals of one neuron and the dendrites of another neuron, neurotransmitters are released within this space.

Question 12

How are signals passed?

Answer 12

• the info neurons carry in the from of electro - chemical signals i.e they are electrical and chemical signals.
• signals within neurons are transmitted electrically.
• signals between neurons are transmitted chemically.

Question 13

What is the presynaptic neuron?

Answer 13

the neuron which transmits the neural impulse.

Question 14

What is the postsynaptic neuron?

Answer 14

the neuron which receives the neural impulse.

Question 15

What is the axon?

Answer 15

a nerve fibre which conducts electrical impulses away from the cell body towards the end of a neuron.

Question 16

What is the presynaptic nerve terminal?

Answer 16

end of the presynaptic neuron and facilitates communication with the next neuron.

Question 17

what is a synaptic vesicle?

Answer 17

they store neurotransmitters.

Question 18

What is a neurotransmitter?

Answer 18

chemical substances made by the neuron specifically to transmit a message.

Question 19

What is a synapse?

Answer 19

a small gap between the presynaptic axon terminals and the postsynaptic dendrites. neurotransmitters are released between them.

Question 20

What is postsynaptic receptor sites?

Answer 20

found on the surface of a postsynaptic neuron and binds to neurotransmitters.

Question 21

What is the process of synaptic transmission?

Answer 21

1. an electrical impulse travels along the axon of the presynaptic neuron.
2. when the electrical impulse reaches the synaptic vesicles which release neurotransmitters towards the presynaptic neuron terminal.
3. the released neurotransmitter diffuses across the synapse between the pre and postsynaptic cell - where the chemical message is being transmitted.
4. the released neurotransmitter binds to the specialised receptor sites on the postsynaptic neuron to transmit an electrical impulse.
5. reuptake: the neurotransmitters is reabsorbed in the vesicles of the pre-synaptic neuron after it has performed its function of transmitting a neural impulse.

Question 22

What are neurotransmitters?

Answer 22

• chemicals that diffuse across the synapse to next neuron.
• the direction of travel for neurotransmitters can only be one way. this is because neurotransmitters are released from the pre-synaptic terminal and received by the postsynaptic neuron.
• each neurotransmitter has a specific molecular structure which fits into a postsynaptic receptor site.
• they have a specialist function e.g. acetylcholine is found at each point where a motor neuron meets a muscle, upon release it will cause the muscles to contract.

Question 23

What are excitatory and inhibitory neurotransmitter?

Answer 23

NT either have an excitatory or a inhibitory effect on the post - synaptic neuron.

adrenaline (excitatory nt) increases the positive charge of the postsynaptic neuron - makes the neuron more likely to fire which leads to an excitatory post - synaptic potential.

serotonin (inhibitory nt) increases the negative charge of the postsynaptic neuron - makes the neuron less likely to fire which leads to a inhibitory post - synaptic potential.

Question 24

What is summation?

Answer 24

• the question of whether the postsynaptic neuron does fire is based on a process called summation.
  a post - synaptic nerve cell can receive EPSPs and IPSPs at the same time.
  excitatory or inhibitory potentials are summed and must reach a certain threshold for an action potential in the postsynaptic neuron to be fired.

Question 25

Briefly outline how excitation and inhibition are involved in synaptic transmission?

Answer 25

when a nt is released across the synaptic cleft it has either an excitatory or inhibitory effect on the postsynaptic neuron. an excitatory effect increases the positive charge in the post - synaptic neuron, making it more likely to fire. An inhibitory effect results in the neuron becoming more negatively charged and less likely to fire.