Nervous System

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Nervous System
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The Vertebrate Nervous System

• receives stimuli from receptors transmits
  information to effectors that respond to
  stimulation
• regulates behavior by integrating incoming
  sensory information with stored information (the
  results of past experience) translating that
  into action by way of effectors
• includes billions of nerve cells (or neurons),
  each of which establishes thousands of contacts
  with other nerve cells
• also includes neuroglia cells that support,
  nourish, and insulate neurons

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Subdivisions of the Vertebrate Nervous System

• Central Nervous System - including the brain
  spinal cord
• Peripheral Nervous System - including cranial
  nerves, spinal nerves, all branches of cranial
  spinal nerves

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Cell types

• Neurons
• Neuroglia
• Astrocytes
• Nourish
• Microglia
• Protection
• Schwann
• Insulation

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Neuron Anatomy

• Perikaryon
• Cell body
• Fibers
• Axons
• Carry impulses away from cell body
• Dendrites
• Carry impulse to cell body
• Unipolar, bipolar, multipolar neurons

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• Ganglion (PNS)
• Nucleus (CNS)
• Nerve (PNS)
• Nerve Tract (CNS)

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Myelinated vs. Nonmyelinated Nerves
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Transmission

• Grade Potential
• Proportional to stimulus
• Magnitude decrease with distance
• Often in Dendrites
• Action Potential
• All or none
• Axons

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Synapse

• Gaps
• Neurotransmitters
• Translate electrical signal to chemical and
  induce electrical signal in next neuron
• Synapses allow for control of impulse
• Concentration of transmitters important
• Summation
• Divergence

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PNS

• Somatic Nerves
• Visceral Nerves
• Autonomic Nervous System
• Afferent neurons
• Sensory
• Efferent
• Motor

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Spinal Nerves

• Named and numbered according to association with
  vertebral column
• Dorsal and Ventral Roots
• Dorsal Root contains a ganglion
• Afferent fibers enter through Dorsal Root
• Efferent leave by ventral root

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Spinal Nerves

• Ramus Communicans
• Nerve branches that connect spinal nerves to
  sympathetic ganglia
• Visceral nerves pass through Sympathetic,
  collateral and visceral ganglia

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Reflex arcs

• Somatic Reflex arc
• Three neurons
• Somatic sensory, somatic motor and association
  neuron
• Visceral Reflex arc
• 4 neurons
• Visceral sensory, Association Neuron,
  Preganglionic Neuron and Postganglionic neuron

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Autonomic Nervous System

• Functional Divisions
• Sympathetic
• Prepares body for strenuous activity
• Slows digestion, empties spleen, increases heart
  rate, mobilizes glucose
• Neurotransmitters Adrenaline and Noradrenaline
• Parasympathetic
• Restores body to rest, enhances digestion, slows
  heart, drops BP, promotes glycogen
• Neurotransmitters Acetylcholine
• Most organs are double innervated

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Anatomical Divisions

• Mammals
• Sympathetic
• Thoracolumbar
• Parasympathetic
• Craniosacral
• Non-mammals
• Mixed functions from all (most) vertebral regions
• Three anatomical distinctions
• Cranial, Spinal, Enteric

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Cranial Nerves

• agnathans, most fish, living amphibians have 10
  cranial nerves crossopterygians amniotes have
  12
• Olfactory nerve (I) - sensory nerve sense of
  smell
• Optic nerve (II) - sensory nerve sense of
  vision
• Oculomotor nerve (III) - motor nerve to extrinsic
  eye muscles
• Trochlear nerve (IV) - motor to extrinsic eye
  muscles
• Trigeminal (V) - mixed nerve sensory from skin
  of head mouth (including teeth) motor to
  muscles of 1st pharyngeal arch (muscles of jaw)

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• Abducens (VI) - motor to extrinsic eyeball
  muscles
• Facial (VII) - mixed nerve sensory from lateral
  line of head, ampullae of Lorenzini, taste
  buds motor to muscles of hyoid arch
• Auditory (VIII) - sensory from inner ear (balance
  hearing)
• Glossopharyngeal (IX) - mixed nerve sensory from
  taste buds lateral line motor to muscles of
  3rd arch
• Vagus (X) - mixed nerve sensory from motor to
  heart, anterior digestive system, mouth, gill
  pouches 2 - 5, lateral line
• Accessory nerve (XI) - motor to derivatives of
  cucullaris muscle (cleidomastoid, sternomastoid,
  trapezius)
• Hypoglossal nerve (XII) - motor to hyoid tongue
  muscles