Bio 104 5/24/96

1. Consists of the brain and the spinal cord
2. Brain: mass of nerve tissues
   • located in the cranial cavity
3. Spinal cord (=column)
   • mass of nerve tissue in the vertebral cavity from which the spinal nerves emanate
4. Function: Communicate with and coordinate responses to and from stimuli occurring in the PNS

1. Nervous system outside of the brain and the spinal cord
2. Cranial nerves (nerves from the brain) and spinal nerves
3. Communication between the body and the CNS
4. Division of the PNS which takes information to the brain from the body
   • sensory division of the PNS
5. Division of the PNS which relays information from the brain to the body: motor division of the PNS
   1. Two components of the motor division of the PNS
      1. somatic nervous system:
         • voluntary skeletal muscles (soma=body)
      2. autonomic nervous system
         • involuntary
         • sympathetic and parasympathetic division of the ANS
         • sympathetic nervous system is responsible for "adrenalin rushes" It pulls blood to the center of the body and is associated with our "fight or flight" mechanism
         • parasympathetic nervous system brings us down
   2. Neurons
      1. all neurons have basically the same architecture
      2. cell bodies contain the nucleus of the cell
      3. Dendrites: multiple cytoplasmic projection from the cell bodies
         • receives information from other neurons and carries the nerve impulse toward the cell body
      4. Axon (single; usually)
         • long projections from the cell body
         • carries nerve impulse away from the cell body

         DENDRITES-->CELL BODY-->AXON See figure 34.1

         Types of vertebrate neurons. Figure 34.1 (a) dendrites are in the receptors
         (c) association neurons or interneurons
         • naked axon
         • in CNS

      5. dendrites interface with:
         1. axon of another neuron and/or
         2. sensory receptors
      6. axons interface with:
         1. dendrites of another neuron and/or
         2. an effector-either a muscle or a gland
         • Cell body
           • nucleus regulates cell division
           • 3 months after birth neurons stop dividing
           • can't regenerate nerve cells
   3. Types of Neurons
      1. Sensory neurons
         1. PNS
         2. dendrites function with sensory receptors
         3. carry information from the body toward the brain and spinal cord
      2. Motor neurons
         1. In PNS
         2. axons junction with effectors (muscles and glands)
         3. carry information from the brain and spinal cord to the body
      3. Interneurons
         1. in both brain and spinal cord
         2. connects sensory neurons with motor neurons
      4. Neuroglial cells:
         • specialized cells found in association with neurons
         1. may serve to assist the nerve in nutrition
         2. may serve to bind several neurons together to form nerves (neuro=nerve and glial=glue)
         3. specialized neuroglial cells of the PNS, Schwann Cells See figure 34.2
            Structure of a typical neuron. Figure 34.2

         4. Schwann Cells wrap itself around the axon of some PNS neurons
            • the cell membrane forms a fatty, protective layer around the axon called a myelin sheath. See figure 34.10
            How a myelin sheath is made. Figure 34.10

         5. Node of Ranvier
            • spaces between the myelin sheath
            • formed by the schwann cells
      5. Multiple Scorosis
         1. autonomical disease
         2. auto-immune disorder in which the body's defense mechanisms (T-lymphocytes = T-cells) attack the myelin sheath
         3. the result of the immune response is the formation of scar tissue on the myelin sheath (termed plaque) which interferes with the ability of the neuron to transmit the information to and from the CNS
         4. progressive and terminal disease
         SEE SIDELIGHT 34.1 PAGE 540
      6. synapse: space between 2 neurons
      7. neuromuscular junction
         • the synapse between the axon of a motor neuron and a muscle
   4. Nerve Impulse

      

      1. At the resting state--resting potential
         • no stimulation
         • net positive charge on the outside of the neuron, and a net negative charge (-70 mV) on the inside of the neuron: polarization
      2. Stimulus of sufficient strength is applied and charges occur in the cell membrane of the neuron which effectively reverse the arrangement of ions
         • Outside of the neuron has a net negative charge
         • Inside the neuron has a net positive charge
      3. This reversal of charge during stimulation is termed depolarization
      4. polarized area (action potential) is propagated down the length of the neuron-this is a nerve impulse
      5. the ions return to their resting state arrangement (net-charge of the inside of the membrane (-70 mV) and net positive charge of the outside of the membrane-- repolarization
         • positive: sodium and potassium
         • negative chloride ions. See figure 34.8

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