Neurons and Synaptic Transmission

• What is the structure of a motor neuron ?

  It has short dendrites and long axons.
• What is the structure of a sensory neuron ?

  It has long dendrites and short axons.
• What is the structure of a relay neuron ?

  It has short dendrites and short axons.
• What is the function of a motor neuron ?

  It connects the Central Nervous System to the effectors (muscles/glands).
• What is the function of a sensory neuron ?

  To carry impulses from the peripheral nervous system to the central nervous system.
• What is the function of a relay neuron ?

  They connect sensory neuron to motor neurons or other relay neurons.
• What are synaptic terminals ?

  The area of a neuron that releases the neurotransmitters into the synaptic cleft.
• What is a Myelin Sheath ?

  They are made of Schwann cells and are there to insulate and protect the impulse.
• What is an axon ?

  They carry the electrical impulse down the neuron (what the Myelin Sheath protects).
• What is the cell body ?

  The cell body contains the nucleus and connects to the dendrites.
• What is the nucleus ?


  The nucleus contains the genetic material of the cell.
• What are the dendrites ?

  They receive the impulses from other neurons.
• What are the Nodes of Ranvier ?

  They are the gaps between the Myelin Sheath.
• What do the Nodes of Ranvier do ?

  They help push the impulse along the axon.
• What are the four stages of the reflex arc ?

  -The stimulus is detected by the sensory neuron.

  -The signal is sent to the relay neuron (via impulse) in the spine

  -The signal is sent to the brain WHILE the signal is also transmitted to a motor neuron.

  -The motor neuron transmits signals to the effector.
• What is a reflex arc ?

  A reflex arc is a nerve pathway that bypasses the brain and goes straight from the stimulus to the spinal cord back and to the effector. They often occur in order to prevent harm to the body.
• What is synaptic transmission ?

  When one neuron transfers an electrical impulse to a chemical message and passes this on to another neuron via the synapse.
• What are the five stages of synaptic transmission ?

  -An action potential travels to the end of a neuron

  -The synaptic vesicles merge with the terminal membrane

  -The Neurotransmitters travel across the synaptic cleft.

  -The Neurotransmitters bind to receptors on the post-synaptic neuron.

  -Any neurotransmitters that are NOT absorbed by the post-synaptic neuron are either broken down by enzymes or they go through re uptake.
• What is Excitation ?

  Excitation is the increase in positive charge that creates an excitatory post synaptic potential (EPSP) and makes the post-synaptic neuron more likely to fire an active potential.
• What is Inhibition ?

  Inhibition is the increase in negative charge that creates an inhibitory post synaptic potential (IPSP) and makes the post-synaptic neuron less likely to fire an active potential.
• What does EPSP stand for ?

  Excitatory Post Synaptic Potential
• What does IPSP stand for ?

  Inhibitory Post Synaptic Potential
• What does Uni-directional mean ?

  The flow of the impulse can only go in one direction and not the reverse due to the function of each part of the neurons.