Cell Types _ Functions

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					 The Nervous System
     Introduction to
Basic Cellular Functions

10 trillion cells in the brain

               Nervous System Basics
• Neuroscience for Kids


• One of many fairly comprehensive tools
  for learning basic NS terminology.
           Cellular Communication
 Homeostasis requires communication
1. Hormone communication:
  Signal molecules produced by secretory cells in
  glands. Transported throughout body via the
2. Neurotransmitter communication:
  Signal molecules produced by nerve cells.
  Transported across a synapse to an adjacent
  nerve cell, muscle cell, organ, gland, etc.
Hormones & Neurotransmitters
Hormone Communication Example
“Fight or Flight” aka “Stress Response”
Neurotransmitter Communication
  Acetylcholine Discovered in 1921

            • Stimulated the vagus
              nerve of Heart #1
            • Heart #1 slowed down

            • Short delay. . . then . . .
            • Heart #2 slowed down
              without being zapped!
“Drugs” that work in CNS are Similar to NT’s

                          dopamine (NT)

                          norepinephrine (NT)



                 Neurons & Glia
        2 Cell Types in Nervous System
Nerve Cell, Neuron in the NS
    Several Types of Glia (aka, neuroglia)
• Astrocytes: form part of blood-
  brain barrier; remove excess NTs
  at synapse; guide axon growth

• Oligodendrocytes: wrap
  around some axons to form myelin
  sheath (can speed impulses 30X)

• Microglia: immune function;
  defend against microorganisms
  and remove cellular waste in NS

• Ependymal Cells: line brain
  cavities and ventricles of the CNS
  and produce cerebrospinal fluid
         Many Types & Functions of Glia
1.   Hold neurons together (“glia” means “glue”)
2.   Align neurons in a physical matrix
3.   Form part of blood-brain barrier
4.   Supply nutrients to neurons
5.   Carry away waste products, dead cells, etc.
6.   Remove excess neurotransmitters
7.   Form myelin sheaths for some neurons
8.   Guide neuron connections— “learning”
9.   Immune function; destroy microorganisms
       Astrocyte Glia
Remove Excess NT’s at Synapse
Astrocyte Glia--Location at Synapse
       Astrocyte Glia
Guide and Connect Neurons

            • Glia fibers orient and
              guide axons towards
              the establishment of
              connections to other
              neurons; this is critical
              to learning & skill
              development through
              practice and review.
     * Purple strand is the Astrocyte
                          Astrocyte Glia
                 Part of the Blood-Brain Barrier

“Big Feet” of astrocyte
glia surround brain
capillaries; this is part of
the blood-brain barrier
      Oligodendrocyte Glia & Microglia

Formation of
Myelin sheath

           Ependymal Cell Glia
Line Brain Cavities & Produce Cerebrospinal Fluid
              Danger: Malignant Glioma

                      When good cells go Bad !

Senator Ted Kennedy
Brain Cancer Research Incomplete

              Johnnie Cochran
   Neurons—the other kind of NS cell
    Cells that Conduct Bioelectrical Impulses

Nervous System Communicates with the Rest of the Body
Parts of a Neuron (simplistic)
  Key Principle: 1-way transmission
Parts of a Neuron (more realistic)

   Axons of motor
neurons may be very
 long. Extend from
the brain to muscles
    and tissues.
         Nervous System Communication

Neuron    Neuron

Neuron    Organs

Neuron    Muscle

Neuron    Glands
Neuron to Neuron Communication
         Neuron to Organ Communication

   Neurons of the
Autonomic Nervous
   System (ANS)
 control involuntary
    responses of
cardiac muscle cells,
blood vessels, sweat
     glands, etc.
Neurons to Gland Communication
Neurons to Sensory Receptors
Neurons to Cardiac Muscle (ANS)
Neurons to Skeletal Muscles
    (voluntary motor control)
          Sensory & Motor Neurons
          Key Principle: 1-way transmission

sensory                                   voluntary

Involuntary “Reflex” Activity

             “Reflex actions”
          (e.g., to mosquito bite)
         are handled in the spinal
        ganglia, without any brain
        interpretation or voluntary
       But NT’s are always needed
      for any nerve communication,
                 or response
        . . . voluntary or reflex . . .
       Future Nervous System Topics

        1. The Blood-Brain Barrier
     2. Routes of Drug Administration
3. Neurotransmitters in the Nervous System

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