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Nervous System Notes Anatomy

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					Nervous System
Basics
 Anatomy and Physiology
The Nervous System
Organization
  Nervous     system divided into:
    Central   Nervous System
      Brain   and spinal cord
    Peripheral   Nervous System
      Somatic

      Autonomic
Central Nervous System
    Brain
      Contains ~100 billion nerve cells
      Trillions of glial cells (support cells)

    Spinal Cord
      Main pathway connecting brain and
       peripheral nervous system (pns)
      Protected by spinal column
Peripheral Nervous System
    Somatic
      Sends sense info to CNS
      Motor nerve fibers from CNS to muscles

      Voluntary motion and reflexes

    Autonomic
      Controls smooth muscles and glands
      Involuntary
The Basic Unit of the
 Nervous System?

    THE NEURON!
Types of neurons
    Sensory
        Ex. from finger tip to spinal cord
    Motor
        Ex. from brain to bicep
    Interneurons
        Carry impulses between them
The Neuron
What’s up with neurons
    Like other cells
        Cell membrane, nucleus, organelles,
         perform normal metabolic processes
    Special because…
      Have dendrites (toward cell) and axons
       (away)
      Communicate using electrochemical
       process
      Specialized structures and chemicals
Neuron Parts
    Cell body (soma) – largest part
        Carries out typical cell functions
    Axons – usually only 1 per neuron
        Long fiber
        Carries impulses away from cell
    Dendrites – can be many
        Short extensions
        Carry impulses to cell body from environment or
         other cells
Nerve Impulse
  Due to movement of ions (charged
   particles) across membrane
  Neurons at rest have a net negative
   charge and outside cell has a net
   positive charge
  A difference in electrical charge
   between two places is a potential
The neuron at rest




         Resting potential = 70mV
Moving Impulse
  Stimulus causes sodium channels to
   open
  Sodium ions rush in to cell
        Cell becomes positively charged
    Potassium ions (which are slower) then
     open to reverse depolarization
Nerve Impulse
  The reversal of
   charges is the
   action potential
  Impulse moves
   down length of cell
        Self-propagating
 http://www.blackwellpublishing.com/ma
  tthews/channel.html
 http://www.blackwellpublishing.com/ma
  tthews/animate.html
 http://www.tvdsb.on.ca/westmin/scienc
  e/sbioac/homeo/action.htm
Threshold = all or none
impulse
Synapse =
             When the wave of Action
            Potentials reach the end of
            the axon the electrical signal
            is converted into a chemical
            signal. This chemical, or
            neurotransmitter, crosses
            the space (Synapse) between
            adjacent neurons and
            initiates an Action Potential
            on another neuron.
Signal Transduction
 1.   Action potential reaches end of axon
 2.   Activates calcium channel – Ca+2 comes into
      neuron
 3.   Ca+2 causes vesicles filled with
      neurotransmitters to fuse with membrane
 4.   Neurotransmitters released into synapse
 5.   Neurotransmitters bind to receptors; Na+
      channels open
 6.   Neurotransmitter destroyed or reabsorbed
Central Nervous System
                 Brain and spinal
                  cord
                 Protected by
                       Meninges
                       Cerebrospinal fluid
The Brain
    Parts of the brain
        Cerebrum
             4 lobes: frontal,
              parietal, temporal and
              occipital
        Cerebellum
        Medulla oblongata
         and pons
        Thalamus and
         Hypothalamus
The Cerebrum
    Responsible for conscious activities
        Thought, voluntary movement, reasoning,
         perception
    Deals with opposite side of body
        Right and left connected by corpus
         callosum
    White and gray matter (gray=cerebral
     cortex)
Cerebellum
  Movement, balance, posture
  Coordinating muscles
Brain Stem
              Pons and medulla
               oblongata
              Controls blood
               pressure, heart rate,
               breathing, and
               swallowing
Hypothalamus and Thalamus
    Hypothalamus               Thalamus
        Control for body           Receives sensory
         temperature,                information and
         emotions, hunger            relays info to proper
         thirst, circadian           region of cerebral
         rhythms                     cortex
Spinal Cord
  Some reflexes processed directly by
   spinal cord (grey matter=cell bodies)
  Relays other messages to or from brain
Organization of PNS

              Peripheral Nervous System


    Somatic           Autonomic


   Sympathetic     Parasympathetic        Enteric
Somatic-Sensory Nervous System
                  All nerves that serve
                   muscoskeletal
                   system and
                   receptors
                  Reflex arc
                        Receptorsensory
                         neuron 
                         interneuron  motor
                         neuron  effector
Autonomic
  Function
   automatically and
   usually
   subconsciously
  Control internal
   organs
  Use 2 motor
   neurons and one
   ganglion for each
   impulse
Sympathetic
    Sympathetic
        Fight or flight
        Accelerates
         heartbeat, dilates
         pupils, increases
         breathing rate
        Main
         neurotransmitter is
         norepinephrine
Parasympathetic
                     Parasympathetic
                         “Rest and Digest”
                         Promotes digestion,
                          slows heartbeat,
                          contracts pupil
                         Main
                          neurotransmitter:
                          acetycholine
Drugs affect on the NS
    Drug: any substance, other than food, that
     changes the structure or function of the body
Stimulants
    Increase actions regulated by nervous
     system
      Increase heart rate, blood pressure,
       breathing rate
      Increase release of neurotransmitters

      Can cause circulatory problems,
       hallucinations and psychological depression
Depressants
  Slow down heart rate, lower blood
   pressure, and relax muscles
  Can be fatal when used with alcohol
   (breathing stops)
  Alcohol – slows down reflexes, disrupts
   coordination and impairs judgment
Other types
    Cocaine – causes release of dopamine
      Causes major crash after use
      Also powerful stimulant

    Opiates- mimic endorphins, overcome
     pain
      Can be highly addictive
      Mess with regular endorphins

				
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