neurons + synaptic transmission

• sensory neuron:

  • carry messages from PNS to CNS (in PNS)
• relay neuron:

  • connect sensory neurons to motor and other neurons (in brain and visual)
• motor neuron:

  • connect the CNS to the effectors (both)
• neurons:

  • basic building blocks of nervous system and are nerve cells that process and transmit messages
  • 100 billion in nervous system, 80% in brain
  • transmits electrical and chemical signals, provides nervous system with primary means of communication
• resting state of neuron and action potential:

  • when neuron is in resting state inside of cell is negatively charged
  • when neuron is activated by stimulus, the inside becomes positively charged for split second - causes action potential
  • creates an electrical impulse that travels down axon to end
• features of neuron:

  • dendrites
  • cell body
  • nucleus
  • axon
  • schwanns cells
  • myelin sheath
  • nodes of ranvier
  • axon terminal
• synaptic transmission:

  • neurons communicate with eachother within groups (neural networks)
  • signals between neurons transmitted chemically across synapse
  • when electrical impulse reaches end of neuron it triggers release of neurotransmitters from vesicles
• features of synaptic transmission:

  • presynaptic nerve terminal
  • synaptic vesicle
  • synaptic cleft
  • neurotransmitters
  • dendrite with postsynaptic receptor sites
• neurotransmitters:

  • brain chemicals that diffuse across synapse to next neuron, direction of travel = one way
  • each neurotransmitters has its own specific molecular structure that fits perfectly into postsynaptic receptor site
• inhibition:

  • serotonin causes inhibition
  • postsynaptic neuron becomes more negatively charged, less likely to fire
• excitation:

  • adrenaline causes excitation
  • postsynaptic neuron becomes positively charged, more likely to fire
• summation:

  • firing is determined by summation - excitatory and inhibitory influences summed up: if net effect is inhibitory less likely to fire, excitatory is more likely to fire
  • once impulse is created it travels down neuron
  • action potential of postsynaptic neuron is only triggered if sum inhibitory or excitatory signals at any time reach threshold