Nervous System

• Sensory input is the function of gathering information and changes are referred to as stimuli.
• Integration is the process of processing and interpreting sensory input.
• Motor output is the response that activates muscles or glands.
• The Central Nervous System (CNS) functions to integrate and interpret, with organs including the brain and spinal cord.
• The Peripheral Nervous System (PNS) serves as communication lines among sensory organs, the brain and spinal cord, and glands or muscles, with organs including nerves extending from the brain and spinal cord.
• Spinal nerves carry impulses to and from the spinal cord.
• Cranial nerves carry impulses to and from the brain.
• • Sensory (afferent) division - nerve fibers that carry information to the CNS
• Motor (efferent) division - nerve fibers that carry impulses away from the CNS

  Two Subdivisions

  1. Somatic nervous system - voluntary; consciously controls skeletal muscles
  2. Autonomous nervous system - involuntary, automatically controls smooth and cardiac muscles and glands; further divided into the sympathetic and parasympathetic nervous systems
• Supports cells in the CNS are grouped as “neuroglia”.
• The general functions of neuroglia include support, insulation, protection of neurons, and control of the chemical environment of the brain.
• Astrocytes are abundant, star-shaped cells that brace neurons and form a barrier between capillaries and neurons.
• Microglia are spiderlike phagocytes that dispose of debris.
• Ependymal cells line the cavities of the brain and spinal cord and assist with the circulation of cerebrospinal fluid.
• Oligodendrocytes wrap around nerve fibers in the central nervous system and produce myelin sheaths.
• Satellite cells protect neuron cell bodies.
• Schwann cells form a myelin sheath in the peripheral nervous system.
• • Neurons - nerve cells
  • Cell body - nucleus and metabolic center of the cell
  • Processes - fibers that extend from the cell body
• Nissl bodies - specialized rough endoplasmic reticulum

  Neurofibrils - intermediate cutoskeleton
• Dendrites - conduct impulses toward the cell body

  Axons - conduct impulses away from the cell body; ends in axon terminals; contains vesicles and transmitters; separated by gaps from the next neurons

  1. Synaptic cleft - the gap between adjacent neurons
  2. Synapse - junction between nerves

  Myelin sheath - whitish, fatty material covering axons

  Schwann cells - produce myeline sheaths in jelly roll-like fashion around axons (PNS)

  Nodes of Ranvier - gaps in myelin sheath along the axon

  Oligodendrocytes - produce myelin sheaths around the axons of the CNS
• Most neuron cell bodies are found in the CNS
• Gray matter - cell bodies and unmyelinated fibers

  Nuclei - clusters of cell bodies within the white matter of the CNS

  Ganglia - collections of cell bodies outside the CNS

  Tracts - bundles of nerve fibers in the CNS

  Nerves - bundle of nerves in the PNS

  White matter - collection of myelinated fibers (tracts)
• Integration - to process and interpret and decide if action is needed
• Interneurons (associated neurons) - connects sensory and motor neurons, found in neural pathways in the CNS
• Multipolar neurons - many extensions from a single cell body, axons branching into many dendrites, most common structure
• Bipolar neurons - one axon, one dendrite, rare in adults, located in special sense organs such as the eye and nose
• Unipolar neurons - have a short single process leaving the body
• Irritability - ability to respond to stimuli
• Conductivity - ability to transmit an impulse