PowerPoint to accompany

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Chapter 10
Basics of the Nervous System
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Chapter 10Nervous System I

• Composed mainly of neural tissue
• Cell Types of Neural Tissue
• neurons
• transmit impulses
• neuroglial cells
• assist neurons

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Divisions of the Nervous System

• Central Nervous System
• brain
• spinal cord
• Peripheral Nervous System
• peripheral nerves
• cranial nerves
• spinal nerves

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Divisions of Peripheral Nervous System

• Sensory Division
• picks up sensory information and delivers it to
  the CNS

• Motor Division
• carries information to muscles and glands
• Somatic carries information to skeletal muscle
• Autonomic carries information to smooth muscle,
  cardiac muscle, and glands

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Divisions Nervous System
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Functions of Nervous System

• Sensory Function
• sensory receptors gather information
• information is carried to the CNS

• Motor Function
• decisions are acted upon
• impulses are carried to effectors

• Integrative Function
• sensory information used to create
• sensations
• memory
• thoughts
• decisions

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Neuron Structure
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Myelination of Axons

• White Matter
• contains myelinated axons (lipid)
• Gray Matter
• contains unmyelinated structures

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Classification of Neuronsbased on shape

• Multipolar
• many processes
• most neurons of CNS

• Bipolar
• two processes
• eyes, ears, nose

• Unipolar
• one process
• ganglia

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Classification of Neuronsbased on function

• Sensory Neurons
• carry impulse to CNS (afferent)
• most are unipolar
• some are bipolar

• Interneurons
• link neurons
• multipolar
• in CNS

• Motor Neurons
• carry impulses away from CNS (efferent)
• multipolar
• carry impulses to effectors

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Types of Neuroglial Cellsprovide scaffolding,
position neurons, remove ions/neurotransmitters,
produce growth factors

• Schwann Cells
• PNS
• myelinating cell

• Astrocytes
• CNS
• scar tissue
• mop up excess ions, etc
• induce synapse formation
• connect neurons to blood vessels

• Oligodendrocytes
• CNS
• myelinating cell

• Ependyma
• CNS
• ciliated
• line central canal of spinal cord
• line ventricles of brain

• Microglia
• CNS
• phagocytic cell (immune)

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Types of Neuroglial Cells
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Regeneration of A Nerve Axon
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Resting Membrane Potential

• Before stimulation, nerve must be in its resting
  potential
• Active transport keeps sodium (Na) ions out and
  potassium (K) ions inside cell
• inside is negative relative to the outside
  (because of other ions) negative inside/positive
  outside
• polarized membrane
• due to distribution of ions
• Na/K pump

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Potential Changes

• at rest membrane is polarized (- in)

• threshold stimulus reached (causes action
  potential)

• sodium channels open and membrane depolarizes
  (Na rushes in)

• Creates momentary hyperpolarization ( in)

• potassium channels open and membrane repolarizes
  (K rushes out) (- in)

• Na is now in and K is now out
• whole process takes 1/1000 of a second

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Action Potentials

• An action potential in one region stimulates an
  action potential in the adjacent region
• Action potential travels down axon (one way)

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Action Potentials/Nerve Impulse

• caused by various stimuli
• chemicals
• temperature changes
• mechanical forces
• occur on dendrites, cell bodies, and axons
• all-or-none
• refractory period
• absolute - time when threshold stimulus does not
  start another action potential
• relative time when stronger threshold stimulus
  can start another action potential

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Saltatory Conduction

• Action potential occurs only at nodes, jumps from
  node to node
• Myelin and diameter of fiber determine speed of
  potential.
• Thick/myelinated fiber- 120 meters/sec
  thin/unmyelinated- 0.5 meters/sec

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The Synapse
Nerve impulses pass from neuron to neuron at
synapses space between neurons
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Synaptic Transmission
Neurotransmitters are released when impulse
reaches synaptic knob
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Neurotransmitters
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Impulse Processing

• Neuronal Pools
• groups of interneurons that make synaptic
  connections with each other
• interneurons work together to perform a common
  function
• each pool receives input from other neurons
• each pool generates output to other neurons

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Convergence

• neuron receives input from several neurons
• incoming impulses represent information from
  different types of sensory receptors
• allows nervous system to collect, process, and
  respond to information
• makes it possible for a neuron to sum impulses
  from different sources

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Divergence

• one neuron sends impulses to several neurons
• can amplify an impulse
• impulse from a single neuron in CNS may be
  amplified to activate enough motor units needed
  for muscle contraction

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