Nervous System

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Nervous System

• Jake Cox

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Purpose and Function

• Coordinate activity of muscles
• Monitor organ systems and bodily function
• Interpret sensory input and Creates and Stops
  distribution of signal
• Initiate action

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Neural Development Neurulation

• The notochord (derived from mesoderm, defines
  axis of embryo, later replaced by the vertebral
  column) induces the ectoderm layer above to form
  the thick/flat neural plate
• Neural plate folds in on itself, forming Neural
  Tube
• Neural Tube later differentiates into the spinal
  chord and the brain
• Tube then twists and kinks to form the three
  primary brain vesicles and five secondary brain
  vesicles, the precursors of the different regions
  of the brain

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Central vs. Peripheral

• Central Nervous System
• Largest part of the nervous system, composed of
  brain and spinal cord. Combined with the
  Peripheral system, it controls behavior.
• Contained within the dorsal cavity, with the
  brain within the cranial subcavity, spinal cord
  in the spinal cavity.
• CNS is covered by meninges, protected by the
  skull/vertebrae.
• Peripheral Nervous System
• Consists of all other nerves that do not lie
  within the CNS.
• Largely composed of nerves.
• Can be divided by direction of neurons and by
  function
• Somatic Nervous System coordinates the bodys
  movements, receiving stimuli
• Autonomic Nervous System
• Sympathetic Division responds to impending
  danger or stress, increase heart rate and blood
  pressure, responds to adrenaline and other
  hormones
• Parasympathetic Division controls function
  during times of rest, constriction of pupils,
  slowing of heart, lowering of blood pressure
  through dilation of blood vessels, stimulation of
  digestive system
• Enteric Division manages the digestive system

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Nervous Tissue

• Three main types of neurons compose all aspects
  of the nervous system
• Sensory (afferent) conduct impulses from the
  sensory organs to the CNS
• Motor (efferent) conduct impulses from the CNS
  to organs/muscles
• Interneurons (connectors) connect sensory
  neurons to motor neurons
• Structure
• Dendrites processes that enter the cell body
  from one end, receive a signal from adjacent
  cells
• Axon single process leaving cell opposite of the
  dendrites, ends in terminal that distribute a
  signal
• Myelin Sheath Coats the axon, helps to conduct
  an electrical signal along the axon with minimal
  loss of signal
• Synapse gap between the axon of one cell and the
  dendrites of an adjacent cell

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Action Potential

• A spike of electrical signal that travels along
  the membrane of a cell, in this case a neuron,
  allows rapid transfer of information through the
  frequency and intensity of the signals
• Based on gradients of ions, specifically Sodium
  and Potassium, which are at resting levels on
  the inside and outside of a cell
• Polarize the cell membrane
• When permeability of the cell membrane changes
  due to the opening of voltage-gated ion channels,
  the cell membrane at that point along the cell
  depolarizes
• Depolarization propagates down the cell membrane,
  conducting the signal through the cell and on to
  other neurons and finally to the target cell
• Resting cell potential is restored due to ATPase
  pumps restoring the ion gradient