Structure of a Neuron

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Structure of a Neuron
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Structure of a Neuron

1. cell body
2. nucleus
3. dendrites
4. axon
5. Schwann cell nucleus

1. myelin sheath
2. node of Ranvier
3. Schwann cell
4. terminal branches
5. synaptic knobs

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Impulses Along a Neuron

• Dendrites receive the nerve impulse and carry it
  toward the cell body, which contains the nucleus.
• The axon carries the impulse from the cell body
  toward the synaptic knobs where it will be
  transferred to other neurons.

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Myelinated vs. Unmyelinated

• Myelinated neurons (those that have a myelin
  sheath) carry nerve impulses faster than
  unmyelinated ones because the impulse jumps from
  one node of Ranvier to the next, instead of
  traveling the whole length of the axon.

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Normal Neural Pathway

• Specialized receptors (light, sound, taste,
  touch, odors) react to a stimulus and generate
  nerve impulses in the sensory neurons around
  them.
• The sensory neurons carry the impulse to the
  spinal cord and then to the brain where
  interneurons interpret the sensory information.

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• The interneurons send out impulses to motor
  neurons which cause a response by an effector
  (muscle or gland).

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Reflex Arc Pathway

• The simplest neural pathway is called a reflex
  arc and it does not involve the brain.
• The pathway is receptor, sensory neuron,
  interneuron in spinal cord, motor neuron,
  effector.

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Reflex Arc
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• The fact that the decision is made in the
  spinal cord saves the time that it would take the
  nerve impulse to travel through the many circuits
  of the brain.
• A faster response time can save the body from
  further damage.
• Reflexes are protective mechanisms that are
  important in maintaining homeostasis.