NERVOUS SYSTEM

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NERVOUS SYSTEM

• Maintenance of homeostasis
• Major regulatory and control center

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FUNCTIONS

• Sensing changes (INPUT)
• Processing information (INTEGRATING)
• Responding (OUTPUT)
• SEAT OF ALL MENTAL ACTIVITY
• CONSCIOUSNESS
• MEMORY
• THINKING

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Divisions of the Nervous System

• Central Nervous System
• Peripheral Nervous System

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Central Nervous System

• Involves the brain and the spinal cord
• Part of the dorsal body cavity
• Contains gray and white matter, and has fluid
  filled spaces

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Peripheral Nervous System

• Cranial and Spinal nerves
• Afferent Nervous System - input
• Efferent Nervous System - output
• somatic (voluntary) NS
• autonomic (involuntary) NS
• sympathetic and parasympathetic divisions

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Cells of the Nervous System

• Neuroglial Cells
• Neurons

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Neuroglial Cells

• Found in CNS
• Astrocytes
• Oligodendrite
• Microglia
• Ependymal

• Found in PNS
• Schwann cell
• Satellite cell

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Neuron

• Cell body (Soma)
• Dendrites
• Axon

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Classifications of Neurons

• Structure
• Function
• Area served

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Neurons by structure

• Pseudounipolar
• Bipolar
• Multipolar

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Neurons by function

• Afferent neurons - sensory neurons
• Efferent neurons - motor or secretory neurons
• Association neurons - interneurons or
  intermediate neurons

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Neurons by the area served

• Visceral neurons - serving the internal organs
• visceral afferent, visceral efferent
• Somatic neurons - serving the body wall
• somatic afferent, somatic efferent

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Neuron Characteristics

• Excitable
• Conductive
• Transmits information
• Cannot reproduce

• Regeneration
• cell body intact
• presence of neurolemma sheath
• regeneration tunnel aligned
• very, little scar tissue

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Nerves

• Bundles of nerve cell processes in the PNS
• Link the PNS to the CNS
• Sensory, motor, or mixed
• Connective tissue
• epineurium, perineurium, endoneurium
• Tract - bundles of nerve fibers in the CNS

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White / Gray Matter

• White matter contains myelinated processes
• PNS - myelinated nerves
• CNS - myelinated tracts
• Gray matter- consists of cell bodies and
  unmyelinated processes
• Nuclei- collection of cell bodies (CNS)
• Ganglia - cell bodies outside CNS

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Conduction Speed

• Diameter of the fiber
• Presence/absence of myelin
• Saltatory conduction
• Temperature/cooling
• Stimulus intensity is coded by the frequency of
  impulses and the number of sensory neurons
  activated by the stimulus

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Synapse Transmission

• Synapse is the junction between one neuron and
  another one or between a neuron and a
  muscle/gland
• Electrical synapse
• Chemical synapse

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Neurotransmitters

• Acetylcholine (variable)
• Amino acids
• aspartate, glutamate (excitatory)
• GABA, glycine ( inhibitory)
• Amines - derivatives of tyrosine
• Dopamine (inhibitory)
• Norepinephrine (excitatory)
• Serotonin (variable)

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Neurotransmitter Removal

• Diffusion out of the synaptic cleft
• Enzyme degradation
• acetylcholinesterase
• Uptake by area cells