| What is the sensory neuron? | They carry messages from the PNs to the CNS. They have long dendrites and short axons. |
| What is a relay neuron? | These connect the sensory neurons to the motor neurons or other relay neurons. they have short dendrites and short axons. |
| How big is a neuron? | Neurons vary in size from less than a millimeter to up to a meter long, |
| What is the cell body and dendrites ? | The cell body includes a nucleus, which contains the genetic material of the cell.
Branchlike structures called dendrites protrude from the cell body. These carry nerve impulses from neighbouring neurons towards the cell body. |
| What is the axon? | The axon carries the impulses away from the cell body down the length of the neuron. The axon is covered in a fatty layer of myelin sheath that protects. The axon and speeds up electrical transmission of the impulse. |
| What and why is the myelin sheath segmented? | If the myelin sheath was continuous this would have the reverse effect and slow down the electrical impulse. Thus, the myelin sheath is segmented by gaps called nodes of Ranvier. |
| What happens to the transmisstons after the myelin sheath? | These speed up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon.
At the end of the axon are terminal buttons that communicate with the next neuron in the chain across a gap known as the synapse. |
| What charge is the neuron at resting state? | Negativley charged comapred to the ouside |
| How does a action potential occur and what does it create? | When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur.
This creates an electrical impulse that travels down the axon towards the end of the neuron. |
| What are neurotransmitters? | chemicals that diffuse across the synapse to the next neuron in the chain. |
| What happens to the neurotransmitters (the journey)? | Once a neurotransmitter crosses the gap, it is taken up by the postsynaptic receptor site on the dendrites of the next neuron
Here, the chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron. |
| What does each neurotransmitter have in structure? | Specific molecular strucutre fits perfectly into the postsynaptic receptor site. |
| What is acetylcholine? | is found at each point where a motor neuron meets a muscle, and upon its release, it will cause muscles to contract. |
| What is excitation? | Causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire. Eg: adrenaline |
| What is inhibition? | Causes inhibition in receiving neuron, resulting in the neuron becoming more negatively charged and less likely to fire. Eg: Serotonin |
