NERVE CELLS

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NERVE CELLS

• by Grace Minter

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OVERVIEW

• Definition
• Structure
• Function

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BASIC DEFINITION

• Nerve Cell (Neuron)
• the structural and functional unit of the nervous
  system

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NEURON STRUCTURE

• All nerve cells contain 4 distinct regions
• 1. Cell body
• 2. Dendrites
• 3. Axon
• 4. Axon terminals

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STRUCTURE CONTINUED

• CELL BODY
• houses nucleus is site of protein synthesis and
  degradation of all neuron proteins and membranes
• AXON
• specialized for the conduction of an electric
  impulse or action potential away from the
  neuronal cell body to axon terminals
• AXON TERMINALS
• Send chemical signals to dendrites of other
  neurons
• DENDRITES
• receive chemical signals from the axon termini of
  other neurons convert the signals into electric
  impulses for delivery to cell body

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FUNCTIONAL MECHANISM

• Neurons function through both electric chemical
  signaling
• An electric potential exist across the plasma
  membrane of neurons
• the potential is due to the selective
  permeability of the membrane to differing ions
• resting membrane potential ? 60 mV, negative on
  inside because cell pushes large number of K
  ions out
• An electrical impulse results from the sequential
  opening closing of ion channels and is
  converted into a chemical signal for message
  transmission

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A CLOSER LOOK

• Transmission of an electrical signal (performed
  by axons)
• 1. Na channels open influx of Na into cell
  causes depolarization of neuronal membrane
• 2. Na channels close K channels open
  release K ions into extracellular space,
  causing hyperpolarization of the membrane
• 3. K channels close membrane returns to
  resting potential ( 60 mV)
• 4. This process spreads across the axon,
  generating an electric signal to the axon
  terminals

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A CLOSER LOOK PART II

• Transmission of a chemical signal through
  synapses (performed by axon terminal
  dendrites)
• synapses ? sites where neurons send receive
  information from other cells
• 1. electrical impulse generated reaches axon
  terminals causes the exocytosis of a chemical
  neurotransmitter contained within a synaptic
  vesicle from the presynaptic cell
• 2. Neurotransmitter travels through synaptic
  cleft binds to specific receptors on the
  dendrites of postsynaptic cell, causing a
  change in its permeability to ions

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BRINGING IT TOGETHER
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SUMMARY

• NEURON ? functional structural unit of the
  nervous system
• All neurons are composed of a cell body, axon,
  axon terminals, dendrites
• Neurons function through both electrical and
  chemical signals in order to transmit messages
  throughout the body

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QUESTIONS