Nervous Tissue

1
Nervous Tissue
Ch 12
2
Function of the Nervous System
sensory input
motor input
sensory receptor
effector
integration
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Anatomical Divisions of the Nervous System

• Central Nervous System (CNS)
• brain
• spinal cord
• Peripheral Nervous System (PNS)
• cranial nerves
• spinal nerves

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Organization of the Nervous System
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Organization of the Nervous System
brain spinal cord
CNS
NS
SNS (voluntary)
PNS (spine cranial nerves)
Sympathetic Parasympathetic
ANS (involuntary)

• Sensory (afferent)

• Motor (efferent)

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CNS
PNS
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Neuroglia
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Typical Neuron
dendrite
cell body
Myelin sheath
Synapse
axon
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Myelin Sheath
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Myelin Sheath
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Types of Neurons
unipolar
multipolar most abundant type in CNS
bipolar eye, ear, olfactory
Dorsal root ganglion cells
12
Neuron Interaction Integration
effector
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Resting Potential of an Axon
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Resting Potential of an Axon
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Depolarization of the Axon Membrane
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Action Potential
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Propagation of an Action Potential
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Propagation of an Action Potential
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Refractory Period
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Saltatory Conduction
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Synapses
Ca2
Presynaptic neuron
Postsynaptic membrane
Synaptic vesicles containing neurotransmitters
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EPSP IPSP
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Synapses
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Neurotransmitters

• Acetylcholine- slows heart rate PNS
• Glutamate- most prevalent neurotransmitter in the
  brain
• Aspartate- in CNS
• GABA- inhibitory neurotransmitter
• Glycine- inhibitory neurotransmitter
• Norepinephrine- awakening from deep sleep
• Epinephrine- increase heart rate
• Dopamine- movement of skeletal muscles
• Seratonin- sensory perception, temp regulation,
  mood, sleep
• Nitric oxide- may play a role in memory and
  learning
• Enkephalin- inhibit pain impulses by suppressing
  release of substance P
• Substance P- enhances perception of pain

tyrosine
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Neurotransmitters
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Types of Circuits in Neuronal Pools
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Neuronal Circuits

• Converging circuit
• same source
• Pacinian corpuscles -- pressure
• different sources
• control of respiration
• Diverging Circuit
• permits broad distribution of a specific input
• types
• A.  amplification
• B.  divergence into multiple tracts

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Neuronal Circuits

• Parallel after-charge circuit
• several neurons process same information at one
  time
• each chain has a different number of synapses,
  but eventually they all reconverge on a single
  output
• output neuron may go on firing for some time
  after input has ceased
• important in withdrawal reflexes
• longer-lasting output from small period of pain 

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Neuronal Circuits

• Reverberating Circuit
• axons extend back toward the sources of an
  impulse and further stimulate the presynaptic
  neuron
• helps maintain consciousness, muscular
  coordination, normal breathing, short term
  memory... 

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Neuron to Neuron Transmission
Afferent (sensory)
Integration center
Efferent (motor)
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Nerve Damage Repair in PNS
chromatolysis
Wallerian degeneration
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Nerve Damage Repair in PNS
Myelin sheath
axon
Shwann cell
cell body
chromatolysis
Shwann cell
Wallerian degeneration
Regeneration tube
Regeneration