Nervous System

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Nervous System

• Neural Control

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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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Cell Types of Neural Tissue

• neurons
• neuroglial cells

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Neuron Structure
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Classification of Neurons Functional Differences

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

• Interneurons
• link neurons
• multipolar
• in CNS

• Motor Neurons
• multipolar
• carry impulses away from CNS
• carry impulses to effectors

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Classification of Neurons Structural Differences

• Bipolar
• two processes
• eyes, ears, nose

• Unipolar
• one process
• ganglia

• Multipolar
• many processes
• most neurons of CNS

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Myelination of Axons

• White Matter
• contains myelinated axons
• Gray Matter
• contains unmyelinated structures
• cell bodies, dendrites

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Types of Neuroglial Cellsin the PNS

• Schwann Cells
• produce myelin found on peripheral myelinated
  neurons
• speed neurotransmission

• Satellite Cells
• support clusters of neuron cell bodies (ganglia)

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Types of Neuroglial Cellsin the CNS

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

• Microglia
• CNS
• phagocytic cell

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

• Oligodendrocytes
• CNS
• myelinating cell

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Types of Neuroglial Cells
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Divisions of the Nervous System

• Central Nervous System
• brain
• spinal cord
• Peripheral Nervous System
• 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

• Divisions of the Motor Division
• 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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Resting Membrane Potential

• inside is negative relative to the outside
• polarized membrane
• due to distribution of ions
• Na/K pump

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Local Potential Changes

• caused by various stimuli
• temperature changes
• light
• pressure
• environmental changes affect the
• membrane potential by opening a
• gated ion channel

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Local Potential Changes

• if membrane potential becomes more negative, it
  has hyperpolarized
• if membrane potential becomes less negative, it
  has depolarized
• graded
• summation can lead to threshold stimulus that
  starts an action potential

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Local Potential Changes
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Action Potentials

• at rest membrane is polarized

• threshold stimulus reached

• sodium channels open and membrane depolarizes

• potassium leaves cytoplasm and membrane
  repolarizes

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Action Potentials
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Action Potentials
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Action Potential Animation

• http//www.mhhe.com/biosci/genbio/animation_quizze
  s/graphics/anm7s3e.ram

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All-or-None Response

• if a neuron responds at all, it responds
  completely
• a nerve impulse is conducted whenever a stimulus
  of threshold intensity or above is applied to an
  axon
• all impulses carried on an axon are the same
  strength

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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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Impulse Conduction
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Saltatory Conduction
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The Synapse
Nerve impulses pass from neuron to neuron at
synapses
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Synaptic Transmission
Neurotransmitters are released when impulse
reaches synaptic knob
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