4.2.2 STRUCTURE AND FUNCTION OF SENSORY, RELAY + MOTOR NEURONS

Question 1

what are neurons?

Answer 1

• cells within the nervous system
• essential to survival
  send messages around the body to our sense organs, glands, and organs and then relay info back from these to the CNS

Question 2

what are three main types of neurons?

Answer 2

1) sensory
2) motor
3) relay

Question 3

what are sensory neurons?

Answer 3

• cells that send info to the brain about the sense
• also known as afferent neurons as they carry into from the PNS towards the CNS
• keep the brain informed about the external and internal environment via processing info from eyes, ears, nose, tongue, skin
• can only transmit messages so they’re unipolar
• have long dendrites + relatively short axons
• the cell body is usually to the side of the cell

Question 4

what are motor neurons?

Answer 4

• carry signals from the CNS towards the organs, muscles + glands in the body
• they’re efferent neurons as they carry info away from CNS toward the PNS
• can transmit and receive messages = multipolar neurons
• short dendrites + relatively long axons
• if connected to muscle = known as a motor end plate

Question 5

what are relay neurons?

Answer 5

• known as interneurons as they take on the role of sensory and motor neurons in the NS
• connect the sensory neurons to the motor neurons
• based in the CNS and carry signals/messages across this part of the nervous system
• known as multipolar neurons
• short axons and short dendrites

Question 6

draw the three different types of neuron?

Answer 6

Question 7

what is the synapse?

Answer 7

the junction where two neurones meet

Question 8

what is the process of synaptic transmission?

Answer 8

1) the cell’s resting state is a negative charge, a stimulus activates the neuron

2) an action potential occurs and an electrical impulse is created which travels down the axon of the neuron

3) the impulse reaches the synaptic terminal of the pre-synaptic neuron

4) this triggers the vesicles filled with neurotransmitters to move to the edge of the membrane of the pre-synaptic neuron

5) the neurotransmitters are released into the synaptic cleft/gap and diffuse across

6) they then bind to the receptors on the post-synaptic neuron membrane

7) if the overall charge of the post-synaptic membrane is positive, this has an excitatory effect and the post synaptic neuron will fire

8) if it’s negative, the effect will be inhibitory and won’t fire

9) leftover neurotransmitters in the gap will be re-uptaken by the pre-synaptic neuron ready for another transmission
OR
broken down by enzymes

Question 9

what is an excitatory response?

Answer 9

• makes it more likely the next neuron will fire
• when the neurotransmitters bind to the receptors on the post-synaptic membrane, the post-synaptic neuron becomes positively charged and an action potential is created
• releases dopamine

Question 10

what is a inhibitory response?

Answer 10

• makes it less likely the next neuron will fire
• when the neurotransmitters bind to the receptors on the post-synaptic membrane, the post-synaptic neuron becomes more negatively charged and an action potential isn’t created

Question 11

what is summation?

Answer 11

whether the overall charge of the post synaptic neuron is +ve or -ve