neurons, structure and synaptic transmission

• What is a neuron?

  A cell which is found throughout the body within the nervous system, 80% of the neurons in a human body are found in the brain
• What is the role of neurons?

  These neurons provide the nervous system with its primary means of communication
• What parts make up the structure of all neurons?

  Dendrites, cell body, nucleus, myelin sheath, nodes of ranvier, terminal buttons
• What is the function of the nucleus?

  Contains the genetic material of a cell
• What is the function of the dendrites?

  Receives signals from other neurons or from sensory receptor cells
• What is the function of the axon?

  Carries nerve impulses, in the form of an electrical signal known as action potential, away from the cell body towards the axon terminals
• What is the function of the myelin sheath?

  Insulates the axon so that the electrical impulses travel faster along the axon
• What is the function of the nodes of ranvier?

  Speed up transmission of the impulse by forcing it to "jump" across the gaps along the axon
• What is the function of the terminal buttons?

  Connects the neuron to other neurons (or directly to organs), using a process called synaptic transmission.
• What are the three types of neuron?

  Sensory, relay and motor
• What do sensory neurons do?

  Carry information from the sense organs in the peripheral nervous system to the central nervous system
• Where are sensory neurons found?

  In the peripheral nervous system
• What is the structure of a sensory neuron?

  They have a cell body, with two stems on either side. One end receives information from the sense organs, and the other passes this on. Each stem ends in dendrites, which spread out and connect with other cells
• What do relay neurons do?

  Allow sensory and motor neurons to communicate and make millions of connections between each other, sensory neurons and motor neurons
• Where are relay neurons found?

  In the central nervous system
• What is the structure of a relay neuron?

  Relay neurons have a cell body surrounded entirely by dendrites.
• What do motor neurons do?

  Stimulate muscles for movement
• Where are motor neurons found?

  In the peripheral nervous system
• What is the structure of a motor neuron?

  They begin at the spinal cord, a long axon (or stem), leads to the muscle, where it divides into a spread-out set of dendrites called the motor end plate, which connects with the muscles. This will cause that muscle to either contract or relax
• What is the first step of synaptic transmission?

  Information is passed down the axon of the neuron as an electrical impulse known as action potential
• What is found at the terminal button?

  Synaptic vesicles which contains chemical messengers, known as neurotransmitters
• What happens once the action potential reaches the terminal button?

  When the electrical impulse (action potential) reaches these synaptic vesicles, they bind to the membrane of the pre-synaptic neuron and release their contents of neurotransmitters into the synaptic gap
• What happens once the neurotransmitters are released into the synaptic gap?

  Neurotransmitters then carry the signal across the synaptic gap. They bind to receptor sites on the post-synaptic cell that then become activated
• What happens once the receptors have been activated?

  They either produce excitatory or inhibitory effects on the post-synaptic cell
• What are excitatory potentials?

  Make the post-synaptic neuron more likely to fire.
• What are inhibitory potentials?

  Make the post-synaptic neuron less likely to fire.
• What is summation?


  The excitatory potentials and inhibitory potentials are summed, if the overall is excitatory then the next neuron will fire and vice versa if the overall is inhibitory