Nervous System

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Nervous System

• There are two divisions.
• CNS and PNS

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Central Nervous System (CNS)

• Brain
• Spinal Cord

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Peripheral Nervous System (PNS)

• Cranial Nerves emerge through cranial foramina
  of the skull
• Spinal Nerves emerge through intervertebral
  foramina
• Ganglia groups of nerve cell bodies outside of
  the brain and spinal chord
• Autonomic Nervous System innervates smooth
  muscle, cardiac muscle, and glands

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Nucleus Cell body Dendrite Axon Schwann
cell Synaptic knobs Node of Ranvier
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Classification of Nerve Cells (Neurons)

• By of Processes
• A. Unipolar one process
• B. Bipolar one dendrite and one axon
• C. Multipolar branching to create more
• than one of each

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99 are Multipolar
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By Function

• A. Sensory (afferent)
• B. Motor (efferent)
• C. Interneurons interposed between sensory and
  motor neurons

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Myelinization

• Myelin Sheath The specialized glial cells that
  wrap around the axon of neurons.
• Within the CNS ? Oligodendrocytes
• Within the PNS ? Schwann Cells

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Unmyelinated Axons
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• Nodes of Ranvier
• Gaps in
• myelin sheath
• on the axon.

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1m/s vs 120m/s Saltatory conduction refreshed
at Nof R
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Ischiatic (Sciatic) Nerve
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Terminology

• Groups of Cell Bodies
• CNS Nuclei
• PNS Ganglia
• Groups of Nerve Processes
• CNS Tracts
• PNS - Nerves

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Ganglia
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Review Parts of the PNS

• Cranial Nerves
• Spinal Nerves
• Ganglia (what do you call the CNS counterpart ?)
• Autonomic Nervous System

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Sympathetic Nervous Fight/Flight

• Increased Heart Rate
• Increased Blood Pressure
• Pupil Dilation
• Decreased Urination
• Increased Sweating
• Bronchial Dilation
• Decreased Salivation

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Parasympathetic Energy Sparing

• Decreased Heart Rate
• Decreased Blood Pressure
• Pupil Constriction
• Increased Urination
• Decreased Sweating
• Bronchial Constriction
• Increased Salivation

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Neurotransmitters -

• Chemicals released by the pre-synaptic neuron.

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• Sympathetic
• Epinephrine,Norepinephrine
• Parasympathetic
• Acetylcholine

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Whats the Matter?

• Grey Matter
• non-myelinated neurons
• White Matter
• Myelinated neurons

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• Brain
• Grey matter covers white matter
• Spinal Cord
• White matter covers grey matter

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PNS Glial Cells

• Cells that support and protect the nervous system

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• Schwann Cells form the myelin sheath for axons
• Hold neurons in place
• Keep messages from getting scrambled
• Increase Speed of Transmition
• Can reconnect a cut axon only in PNS, not CNS

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CNS Glial Cells

• Oligodendrocytes wrap around axons to form the
  myelin sheath

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• Astrocytes mediate metabolic exchange

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• Microcytes
• take up extracellular K
• macrophages

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Brain

• Cerebrum made of white and grey matter
• Largest part of mammalian brain
• Higher order behavior (awareness, learning)

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• Cerebellum motor function and coordination
• Brain Stem
• Medulla Oblongata, Pons, Mid-brain
• Autonomic Functions things you dont think about

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Ventricles and Cerebrospinal Fluid

• Ventricles Open spaces in the brain, filled
  with fluid, that support and cushion the brain.

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• Cerebrospinal Fluid slippery, clear fluid that
  bathes and cushions the CNS.
• Produced by Choroid Plexuses
• Reproduced every 24 hours

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Meninges

• Dura Mater
• Arachnoid Membrane
• Pia Mater -

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Reflexes

• Spinal Reflex- rapid, automatic response to
  sensory input
• Does not require brain
• Reflex Arc- sensory receptor-gtsensory neuron
  -gtCNS-gtinterneuron-gtmotor neuron-gttarget organ

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Divisions of Motor Systems

• UMN-neurons in CNS that activate motor neurons
  (lesionsgtgtgtspastic paralysis, hyperactive
  stretch)
• LMN-neurons in cranial spinal nerves that
  directly innervate muscles (lesionsgtgtgtflaccid
  paralysis, muscular atrophy)

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Conscious Proprioception

• Sense of body position and movement without sight
• How?
• Stretch receptors in skeletal muscle, tendons,
  ligaments, joint capsules