Neurons and synaptic transmission

• What are neurons?


  specialised cells whose function is to move electrical impulses to and from the central nervous system
• what is an action potential?


  Electrical signal that travels along the membrane of a neuron.
• How does an action potential occur?


  • the dendrites of neurons receive information from sensory receptors or other
  • this information passes down to the cell body and onto the axon
  • the information travels down the membrane of the neuron in the form of an electrical signal (an action potential)
• what speed do neurons travel at?


  250mph
• what is exocytosis?


  • vesicles containing neurotransmitters move and merge with the cell membrane to release neurotransmitters into the synaptic gap
• what is the control centre of a neuron?


  cell body
• what is the myelin sheath?


  an insulating layer that forms around the axon
• what happens if the myelin sheath is damaged?


  impulses slow down
• what do sensory neurons do?


  carry nerve impulses from sensory receptors to the CNS (brair and spinal cord)
• where are sensory neurons found?


  eyes, ears, tongue and skin
• what is neurotransmission?


  when information (sensory, cognitive, autonomic) is passed around the nervous system via electrochemical signals.
• how do reflex actions occur quickly?


  not all sensory information travels as far as the brain, with some neurons terminating in the spinal cord. This allows reflex actions to occur quickly without the delay of sending impulses to the brain
• what are relay neurons?


  Relay neurons, also known as interneurons or association neurons, are neurons that transmit signals between sensory neurons and motor neurons in the central nervous system.
• what are motor neurons?


  form synapses with muscles and control their contractions
• what’s a neurotransmitter?


  chemical substances that play an important part in the workings of the NS by transmitting nerve impulses across a synapse
• what’s synaptic transmission?


  refers to the process by which a nerve impulse passes across the synaptic cleft from one neuron to another
• explain the process of synaptic transmission


  • an action potential travel down a pre-synaptic neuron to its axon terminal
  • exocytosis takes place
  • neurotransmitters diffuse across the synaptic gap, binding to their corresponding receptor sites on the post-synaptic neuron
  • if positively charged posn will fire
  • the neurotransmitters detach from their receptor sites, getting re absorbed by the vesicles, broken down by enzymes or excreted via the intercellular fluid and bloodstream
• what is summation?


  the sum total of excitatory, vs inhibitory, neurotransmitters locking on to a post synaptic cell and affecting its polarity
• what are examples of excitatory neurotransmitters?


  dopamine and noradrenaline
• examples of inhibitory neurotransmitters? 


  serotonin, GABA
• when will an action potential occur?


  only generated if sum total of all excitatory and inhibitory post-synaptic potentials create a positive charge in the POS cell otherwise it stay negatively charged overall and doesn’t fire
• what is the polarity of the POSN?


  negative
• what do some antidepressants do?


  inhibit the reuptake of neurotransmitters leaving the neurotransmitter in the synapse for longer therefore increasing its activity
• Whats a synapse?


  the conjunction of the end of the axon of one neuron and the dendrite or cell body of another
• what does EPSP stand for?


  Excitatory Postsynaptic Potential
• what does IPSP mean?


  Inhibitory postsynaptic potential.