The Nervous System

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The Nervous System

• Control Center for Maintaining Homeostasis

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Nervous System

• The nervous system coordinates the activities of
  all of the bodys organ systems so that they work
  in concert with one another
• What systems must cooperate during exercise?
• What do we use to respond to changes in the
  external environment?
• Do the senses operate individually?

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Components of the Nervous System

• Two main sections
• The Central Nervous System
• Brain and spinal cord
• coordinating center for incoming and outgoing
  information
• Peripheral Nervous system
• Nerves that extend to the rest of the body
• Carries information between organs and the CNS.

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Two basic types of Nerves

• sensory or afferent nerves
• Carry signals to CNS
• motor or efferent nerves
• Carry signals from CNS

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Peripheral Nervous System (PNS)

• Somatic nerves
• connect skin, skeletal muscles and bones to CNS
• Autonomic nerves
• Connect visceral organs

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Somatic nerves

• control skeletal muscles, bones and skin
• Voluntary
• Sensory to CNS
• CNS to Motor
• Reflexes

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Autonomic nerves

• Special motor nerves that control the internal
  organs
• Comprised of two divisions that work in
  opposition
• Sympathetic nerves
• Fight or flight response (survival)
• Parasympathetic nerves
• Active when body is at rest
• resting and digesting

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Autonomic

• Broken into two different divisions (systems) the
  Parasympathetic and Sympathetic
• Parasympathetic
• House keeper division
• Uses acetylcholine (neurotransmitter)
• Sympathetic
• Excitatory division
• Uses norephinephrine (neurotransmitter)

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What is a Nerve

• A Collection of nerve fibers in the peripheral
  nervous system

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Cells of the Nervous System

• Two type of cells that make up nerve fibers
• Neurons
• Supportive cells
• Neuroglia
• Schwann cells

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Nerve Cells

• Neurons transmit electrochemical signals along
  their length
• cell body
• dendrites
• Axon
• axon terminals

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Cell Body

• The Cell body contains all of the cell
  organelles. Such as the
• Nucleus
• Mitochondria
• Important in the manufacturing of Neural
  transmitters.

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Dendrites

• The Branching structure that receives signals
  from other Nerves or if they are sensory Neurons
  receive signals externally.
• Conducts the nerve impulse to towards the cell
  body.

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Axon

• the long extension of a neuron that carries nerve
  impulses away from the body of the cell.
• Link the Nerve to either the next nerve (sensory
  or interneuron) or to a muscle (motor neuron)

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Axon

• Usually much longer than a Dendrite and usually
  covered with a insulating layer called the myelin
  sheath.
• axon terminals - the the hair-like ends of axon
• Release chemicals (neurotransmitters) to transmit
  signal to next neuron in junction
• Junctions between neurons and another cell called
  a synapse

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Supportive Nerve Cells

• Glial Cells supporting cells that usually form a
  type of protection and insulation for electical
  conduction
• Proper names for CNS and PNS
• Neuroglia in CNS
• Schwann cells in PNS

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Glial Cells in PNS
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Myelin Sheath

• Myelin is the fatty substance that wraps around
  axons and protects/insulates them
• Formed by Schwann Cells in the PNS,
• gaps called Nodes of Ranvier are left between the
  myelin
• Myelination and the Nodes of Ranvier increase the
  speed that the electrical signal moves down the
  axon.

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Myelin Sheath

• New research suggest that the electrical wave
  that travels down the axon actually jumps from
  one node to another. Thereby increasing the speed
  of transmission.
• Multiple sclerosis is caused by the destruction
  of the myelin sheath

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Neurilemma

• All nerves in the peripheral nervous system
  contain a thin membrane called the neurilemma.
• It surrounds the axon and promotes regeneration
  of damaged axons.

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Neurilemma

• Nerves in the brain that contain myelin sheath
  and neurilemma are called white matter and those
  that arent is the gray matter. Damage to the
  gray matter is permanent.

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Different Types of Neurons

• They all carry electro-chemical nerve signals,
  but differ in structure
• (the number of processes, or axons, emanating
  from the cell body) and are found in different
  parts of the body.
• Sensory neurons
• Motor-neurons
• Interneurons

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Interneurons

• form all the neural wiring within the CNS.
• have two axons (instead of an axon and a
  dendrite).
• one axon communicates with the spinal cord
• Other one with either the skin or muscle.