Transmission Between Neurons

• What is synaptic tranmission?

  Chemical process where NTs released from one neuron and attach to the next, this initiates a reaction that results in postsynaptic potentials
• What is a synapse?

  A synapse is a junction between two nerve cells where information is transmitted
• 1st stage of synaptic transmission...

  AP arrives ar presynapaptic knob, calcium ions enter knob through channels opening fusion pore
• 2nd stage of synaptic transmission...

  vesicles containing NT fuse with membrane and pore fully opens, release if NT from vesicles (exocytosis)
• 3rd stage of synaptic trasnmission...

  NT diffuses across cleft and binds to postsynaptic receptors, postsynaptic channels open, ions flow creating either excitatory or inhibitory post synaptic potentials
• Post synaptic potnetial depends on..

  which ion channel is opened when NT bind to post-synatpic membrane
• If sodium ion channel opened...

  influx of sodium ions causes doplarisation ---> excititory post synaptic potential
• If potassium ion channel opened...

  efflux of potassium ions causes hyperpolarisation ---> inhibitory post syanptic potential
• If chloride ion channel opened...

  influx of chlorine ions causes hyperpolarisation ---> inhibitory post synaptic potential
• What are ionotropic receptors?

  receptors that contain a binding site and an ion channel which opens when molecule attaches
• What are metabrotropic receptors?

  receptors that contain a bindings site, initiates a chain reaction that eventually opens ion channels but this requires energy (PSPs produced are slower)
• What is reuptake?

  when NTs are taken back by the presynaptic terminal via transporter molecules
• What is enzymatic degradation/deactivation?

  When NTs are broken down by enzymes e.g. acetylcholinesterase
• What is neural integration?

  the summation of PSPs that controls whether a neuron fires
• If a PSP is excitatory...

  increases likelihood of neuron firing
• If a PSP is inhibitory...

  decreases likelihood of neuron firing
• Inhibitory PSPs do not always inhibit behaviour...

  • Inhibition of inhibitory neurons = more likelihood of behaviour
  • Excitation of inhibitory neurons = less likelihood of behaviour
• What is an antagonist?

  a drug that blocks NT, e.g. Botox blocks release of acetylcholine and prevents muscle contraction so paralyses muscles
• What is an agonist?

  a drug that mimics NT and enhances synapse function, e.g. muscarine imitates acetylcholine
• What is GABA?

  most abundant inhibatory NT in CNS
• What is glutamate?

  most abundant excitatory NT in CNS
• What is acetylcholine?

  NT that works primarily in muscles