Neurons + synaptic transmission

• Structure of a neuron

  A) synapse

  B) node of ranvier

  C) axon

  D) dendrite

  E) schwann cell

  
• cells that conduct nerve impulses are called neurons
• neurons are separated by a gap called the synapse
• a dendrite receives signals from other neurons or sensory receptor cells
• an axon is a long fibre carrying nerve impulses in form of electrical signal (actional potential) away from the cell body towards terminals
• the myelin sheath surrounds the axon (expect the relay neuron) - it insulates the axon so electrical impulses travel faster
• the synaptic terminal connects neurons to others using a process called synaptic transmission
• the 3 types of neurons

  • sensory
  • motor
  • relay
• sensory - relay - motor

  • how information travels through the body
• the sensory neuron is found in receptor cells such as eyes, ears and skin
• the sensory neuron carries nerve impulses from the PNS to the CNS
• when the nerve impulses from the sensory neuron have reached the brain, they are translated into 'sensations' for example vision and hearing
• sensory neuron = long dendrites and short axons
• motor neurons are found in the central nervous system and control the muscle movement alongside carrying messages from the central nervous system to muscles and glands.
• when motor neurons are stimulated they release neurotransmitters that bind to receptors on muscles to trigger a response - leading to movement
• the basic structure of a motor neuron includes short dendrites and long axons
• the relay neuron is found between sensory input and motor output
• relay neurons are found in the brain and spinal cord which allow sensory and motor neurons to communicate
• relay neurons carry messages from sensory to motor neurons or to other relay neurons
• the basic structure of a relay neuron includes short dendrites and long axons
• synaptic transmission is the process by which one neuron communicates with another - how information is transferred through the body - through synaptic transmission
• when a neuron is not sending a signal - it is 'at rest'

  when the neuron is at rest the inside neuron is negative compared to outside
• when neuron is activated by stimulus the inside of cell becomes positively charged for short time - action potential
• neurotransmitters are chemicals that are released from a synaptic vessel into the synapse by neurons
• neurotransmitters affect the transfer of an impulse to another nerve or muscle
• reuptake is the reabsorption of a neurotransmitter transporter
• neurons can only travel and transmit info in one direction at a synapse because of their specific functions

  • the neurotransmitters are released from the vesicles at the end of the presynaptic neuron and bind to sights at the start of post synaptic neuron
• the reflex response:

  • in reflex acr, stimulus, such as flame touching skin is detected by sense organs in peripheral nervous system which conveys message along sensory neuron
  • message reaches central nervous system where it connects with relay neuron
  • then transfers message to motor neuron
  • carries messages to an effector such as a muscle which causes muscle to contract and move

  A) sensory

  B) motor

  C) relay

  
• synaptic transmission

  A) presynaptic neuron

  B) vesicles

  C) sites

  D) inhibitory

  
• excitation is where the neurons message continues to be passed along to the next cell
• inhibitory effect on a neurotransmitter means that the message will be blocked or prevented from being passed on any further