Neurons and synaptic transmission

Question 1

What are neurons?

Answer 1

• 100 billion of them
• transmit signals electrically and chemically
• provide nervous system with primary means of communication

Question 2

What are the types of neurons?

Answer 2

• sensory neurons
• relay neurons
• motor neurons

Question 3

The structure of a neuron

Answer 3

• cell body
• dendrites
• axon
• axon carried in myelin sheath
• myelin sheath segmented by nodes of ranvier
• end of axon is terminal buttons

Question 4

what does the cell body do?

Answer 4

• holds nucleus that contains the bodies genetic info

Question 4

what do dendrites do?

Answer 4

• carry nerve impulses from neighboring neurons to cell bodies

Question 4

what do axons do?

Answer 4

• carries the impulse away from the cell body down the length of the neuron

Question 5

what does the myelin sheath do ?

Answer 5

• fatty layer covering the axon protecting it
• speeds up electrical transmission of the impulse
• if it was continuous it would have the reverse effect

Question 5

what do the nodes of ranvier do?

Answer 5

• segments the myelin sheath and speeds up transmission of the impulse
• forcing it to jump along the gaps of the axon

Question 6

what do the terminal buttons do?

Answer 6

• communicate with the next neuron in the chain across a gap called the synapse

Question 7

Location of motor neurons

Answer 7

• ## the cell bodies may be in the CNS but have long axons which form part of the PNS

Question 8

Location of sensory neurons

Answer 8

• located in the PNS in clusters known as the ganglia

Question 9

Location of relay neurons

Answer 9

• make up 97% of all neurons and most are found in brain and visual system

Question 10

Electrical transmission: the firing of a neuron

Answer 10

• neuron in resting state= inside the cell is negatively charged compared to the outside
• when activated by a stimulus the inside becomes positively charged for a second
• this causes action potential
• creates electrical impulse that travels down axon to end of a neuron

Question 11

What is synaptic transmission?

Answer 11

• where neighboring neurons communicate with each other by sending chemical messages across synapses

Question 12

What is chemical transmission?

Answer 12

• nuerons communicate in groups called neural networks
• signals between neurons transmitted chemically across the synapse
• when impulse reaches pre synaptic terminal it triggers the release of a neurotransmitter from synaptic vesicles

Question 13

what are neurotransmitters?

Answer 13

• chemicals that diffuse across a synapse that are taken up by the next neuron at the post-synaptic receptor site
• chemical message is then turned back into an electrical one
• direction of travel can only be one way

Question 14

what is the lock and key theory ?

Answer 14

• each neurotransmitter has its own molecular structure that fits into a postsynaptic receptor site

Question 15

neurotransmitters and their specific functions?

Answer 15

• each neurotransmitter has specialist functions
• acetylcholine is found where a motor neuron meets a muscle and when it is released the muscle contracts

Question 16

what is an excitatory neuron?

Answer 16

• adrenaline causes excitation of the post synaptic neuron by increasing the positive charge and making it more likely to fire

Question 17

what is an inhibitory neuron?

Answer 17

• serotonin causes inhibition in the receiving neuron by becoming more negatively charged and less likely to fire

Question 18

what is summation?

Answer 18

• excitatory and inhibitory influences are summed
• net effect is inhibitory then the post synaptic neuron is less likely to fire
• net effect is excitatory then the posy synaptic neuron is more likely to fire
• action potential of the post synaptic neuron is only triggered if the sum of both signals reaches the threshold