The Nervous System Part 1

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The Nervous SystemPart 1

• Organization of the Nervous System

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The nervous system is the wiring that keeps
the body connected and functioning. Works with
the endocrine system to keep the body in
homeostatic balance. The nervous system also
enables us to learn, form memories and allow for
critical and creative thinking in ways not fully
understood.
Parkinsons kills dopamine producing cells, so
there is nothing to stop muscle contractions.
Alzheimer's affects memory cells.

• Parkinsons and Alzheimers disease both affect
  the nervous system.

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Organization of the Nervous System

• Central Nervous System (CNS)
• Brain and spinal cord
• makes decisions
• made up of tracts of fibers
• Peripheral Nervous System (PNS)
• Cranial and spinal nerves
• Relays info to and from the CNS
• made up of Nerves

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Organization of the Peripheral Nervous System

• Afferent Divisions (Sensory messages)
• carries info towards the CNS
• Efferent Divisions (Motor messages)
• carries info away from the CNS

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Organization of the Peripheral Nervous System

• Somatic Nervous System (SNS) Voluntary
• Controls skeletal muscles
• Somatic sensory division (afferent) stimulus
  from muscle receptors to the CNS.
• Somatic motor division (efferent) response from
  CNS to skeletal muscles
• Autonomic Nervous System (ANS) Involuntary
• Controls smooth and cardiac muscles, glands
• Visceral sensory division (afferent) stimulus
  from organ receptors to CNS.
• Visceral motor division (efferent) response from
  CNS to organs
• Sympathetic and parasympathic

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Divisions of Autonomic Nervous System

• Involuntary part of the peripheral nervous system
• Sympathetic Division
• Fight or flight response
• Takes over to deal with immediate threats
• Parasympathetic Division
• Rest and repair division
• Coordinates normal resting activities

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The Nervous SystemPart 2

• Cells of the Nervous System

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Cells of the Nervous System

• Neurons (nerve cells)
• Excitable cells that transmit signals
• Neuroglia (glial cells)
• Are support cells for the neurons
• Sometimes called nurse cells

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Neurons

• Key Parts
• No centrioles because amitotic
• Soma or cell body -contains the nucleus
• Nissl bodies - ribosomes to make
  neurotransmitters.
• Dendrites(receptors) - receive signals
• Axon - long arm extending away from cell body,
  transmits signal away from cell body to next
  neuron
• Axons can have side branches called axon
  collaterals.

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Path of Nerve Impulse

• Dendrite ? cell body ? axon ? synapse

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Structural Classification of Neurons

• A. Multipolar
• Most neurons in brain and spinal cord are
  multipolar
• B. Bipolar
• Only one axon and dendrite
• Least numerous
• Found in eye, inner ear and nose

• C. Unipolar
• One end branches toward CNS while the other goes
  toward PNS
• Two processes form a long axon
• Carries both sensory and motor info.

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TYPES OF GLIAL CELLS

1. Astrocytes
2. Microglia
3. Ependymal cells
4. Oligodendrocytes
5. Schwann cells
6. Satellite cells

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Astrocyte
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Astrocytes- star cells

• Found only in the CNS
• Largest and most numerous type of glia
• Bridge between capillaries and neurons
• filter harmful substances and transport
  nutrients.
• They form the blood-brain barrier (BBB)

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Microglia
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Microglia

• Found in CNS
• Small and stationary
• Fight infection in brain tissue through
  phagocytosis.

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Ependymal cells
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Ependymal cells

• Found only in CNS
• Line fluid-filled cavities in the brain and
  spinal cord
• Form Cerebrospinal fluid (CSF)
• Cilia helps keep fluid circulating through brain
  and spinal cord.

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Myelin

• Whitish fatty material that increases speed of
  conduction in an axon
• Insulates nerve fiber axons
• Myelinated fibers are called white matter
• Non-myelinated fibers are called gray matter
• Destroyed in individuals with multiple sclerosis

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Schwann Cells
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Schwann Cells

• Found only in PNS
• Form myelin sheaths around cells of the PNS.
• Gaps between schwann cells are called nodes of
  ranvier.

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Oligodendrocytes
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Oligodendrocytes

• Found only in CNS
• Produce the fatty myelin sheath around the nerve
  fibers of CNS
• Hold nerve fibers together

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Quick Check

1. What is the difference between neurons and glial
   cells?
2. What does myelin do?
3. Which glial cell makes myelin in the CNS?