bio neurons and synaptic transmission

• what are neurons


  nerve cells that process and transmit msgs thru electrical and chemical signals
• what are the 3 types of neurons

  -sensory, relay and motor neuron
• draw and label the neurons structure 


  :

  
• explain the structure of a neuron

  -cell body includes nucleus-which contains genetic material of cell

  -dendrites: branchlike structures protruding from cell body, carry nerve impulses from neighbouring neurons to cell body

  -axon: carries impulses away from cell body down neuron, axon covered in fatty layer of myelin sheath that protects axon and speeds up electrical transmission of impulse

  -myelin sheath: segmented by gaps- nodes of ranvier this speed up the transmission of impulse by forcing it to jump across gaps
• what is at the end of axon?

  -terminal buttons at end of axon that communicate with next neuron in chain across a gap called synapse
• explain electrical transmission-how a neuron is fired

  -when neuron is in resting stage the inside of the cell is negatively charged compared to outside

  -when a neuron is activated by a stimulus, the inside of cell becomes positively charged causing the action potential to occur

  -this creates an electrical impulse that travels down the axon towards end of neuron
• explain synaptic transmission (chemical)

  -neurons communicate with each other within groups knows as neural networks

  -each neuron is separated from the next by gaps called synapse

  -signals within neurons are transmitted electrically

  -signals between neurons are transmitted chemically across synapse

  -when electrical impulse reaches end of neuron- the presynaptic terminal, it triggers the release of neurotransmitter from tiny sacs called synaptic vessels
• explain neurotransmitters


  -chemicals that diffuse across synapse to next neuron

  -once neurotransmitter crosses gap, it is taken up by postsynaptic receptor site on dendrites of next neuron

  -here chemical msg is converted back into electrical impulse

  -direction of travel in only 1 way
• what two effects does a neurotransmitter have?

  -excitatory or inhibitory
• what determines whether a postsynaptic neuron fires?

  -summation

  -the excitatory and inhibitory are summed

  -if the net effect on postsynaptic neuron is inhibitory the postsynaptic neuron is less likely to fire

  -if net effect is excitatory it is more likely to fire bc its positvely charged