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Nervous System 8:1-8:4 (8.1: The nervous system has anatomical and…

- - - - somatic nervous system
      - Autonomic: smooth muscle, cardiac muscle, glandular secretions
- - - - dendrites: receive signals
      - axon: carries outgoing signals
      - synaptic terminal: communicate with other cells
    - - multipolar neuron: most common neuron in CNS. Has two or more dendrites and a single axon. multipolar
      - unipolar neuron: continuous dendrite and axon. PNS. unipolar
      - bipolar neuron: rare but occur in special sense organs such as sight, hearing, smell
    - - sensory neurons
      - motor neurons
      - interneurons
    - - human body form the afferent division of the PNS
      - 2 somatic sensory receptors
        
        external receptors: provide info about the external environment in the form of touch, temp, and pressure sensations and the more complex senses of sight, smell, hearing and touch
        
        Proreceptors: monitor the position and movement of skeletal muscles and joints
      - visceral receptors/ internal receptors: monitor the activities of the digestive, respiratory, cardiovascular, urinary, and reproductive systems and provide sensation of taste, deep pressure and pain
    - - carry instructions from the cns to other tissues, organs and organ systems
      - 2 types
        
        somatic motor neurons
        
        innervate skeletal muscles
        
        visceral motor neurons
        
        innervate all other effectors including cardiac muscle, smooth muscle and glands
    - - located in brain and spinal cord. distribute sensory information and the coordination of motor activity
  - - - Astrocytes
        
        largest/ most numerous
        
        vital to blood- brain barrier maintenance
      - oligodendrocytes
        
        wrap around axons
        
        myelin membranous sheath of insulation
      - microglia
        
        smallest/ rarest
        
        phagocytic cells made from white blood cells in the CNS
      - Ependymal
        
        line the central canal and spinal cord and brain chambers
        
        ependyma: lining of epithelial cells
    - - satellite cells
        
        surround and support neuron cell bodies in the PNS
      - Schwann cells: cover every axon in the CNS
    - - Center
        
        neuron cell bodies with a common function
      - nucleus
        
        center with a discrete boundary
      - tracts
        
        bundles of axons
      - columns
        
        larger groups of tracts in the spinal cord
      - pathways
        
        link the centers of the brain with the rest of the body
        
        sensory pathways
        
        distribute info from sensory receptors to processing centers in the brain
        
        motor pathways
        
        concerned with motor activity and end at the the skeletal muscles they control
- - - - membrane potential
        
        charges seperated by a plasma membrane
      - resting potential
        
        potential of an undisturbed cell
    - - depolarization
        
        as the number of + charged ions on the inner surface of the plasma membrane potential shifts towards 0 mV
      - hyperpolarization
        
        taking membrane potential from -70 mV to -80 mV
      - graded potential
        
        membrane changes that cannot spread far from the site of stimulation
      - threshold
        
        an action potential will not appear unless the membrane depolarizes to the threshold level
      - all or none principal
        
        a given stimulus either triggers a typical action potential or it does no produce on at all
    - - refractory period
        
        from the moment the voltage-gates sodium channels open at threshold until repolarization is complete, the membrane cannot respond normally to further stimulation
  - - - continuous propagation
        
        the process continues in a chain reaction that soon reaches the most distant portion of the plasma membrane.
      - saltatory propagation
        
        action potential jumps from node to node rather than proceeding in a series of small steps
- - - - the opposing plasma membranes are seperated by a narrow space
  - - - acetylocholine
        
        released at cholinergic synapses
    - - Arrival of an action potental at the synaptic know
      - release of the the neurotransmitter ACh
      - Binding of ACh and the depolarization of the postsynaptic membrane
      - Removal of ACh by AChe
    - - norepinephrine (NE)
        
        important in the brain and in portions of the autonomic nervous system
      - adrenergic
      - dopamine
      - gamma aminobutyric
      - serotonin
  - - - group of interconnected interneurons with specific functions
      - divergence
        
        information spreads from one neuron to several neurons or from one neuronal pool to multiple neuronal pools
      - convergence
        
        several neurons synapse on a single postsynaptic neuron
  - - - information to another neuron or to an effector cell. Information transfer occurs through the release of chemicals called neurotransmitters
    - - synapses between a neuron and another cell type
- - - - seperates the inner surface of the dura mater from the second meningeal layer, the arachnoid
    - - deep to epithelial layer
      - made up of squamous cells
      - contain a delicate web of callagen and elastic fibers
- - - - narrow internal passageway filled with cerebrospinal fluid
    - - contain the cell bodies of sensory neurons
    - - contain the axons, bring sensory info to the spinal cord
    - - contain axons of the CNS motor neurons that control muscles and glands
    - - contain both sensory and motor fibers. form the outside of the ventral canal, where ventral and dorsal roots unite
  - - - projections of gray matter
    - - forms a butterfly shape
      - dominated by cell bodies of neurons and glial cells
    - - contain sensory nuclei
    - - involved in motor control of skeletal muscles
    - - contain axons that cross from one side of the spinal cord to the other
    - - white matter can be divided into 3 regions
        
        anterior
        
        posterior
        
        lateral
    - - carry sensory info toward the brain
    - - convey motor commands into the spinal cord