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Nervous System I


Nervous System The nervous system is the master controlling and communicating system of the body Every thought, action, ... Parasympathetic Division: ... – PowerPoint PPT presentation

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Title: Nervous System I

Nervous System I
  • Chapter 11

Nervous System
  • The nervous system is the master controlling and
    communicating system of the body
  • Every thought, action, and emotion reflects its
  • Three overlapping functions
  • Millions of sensory receptors to monitor changes
    occurring both inside and outside the body.
    (called sensory input)
  • It processes and interprets sensory input and
    decides what should be done at each moment
  • It causes a response (called motor output), by
    activating effector organs
  • This next slide is on pg 389 in your book!

Nervous System
Central Nervous System and Peripheral Nervous
  • Central Nervous System (CNS) composed of the
    brain and spinal cord
  • Peripheral nervous system (PNS) composed of the
    nervous (cranial and spinal) that connects the
    CNS to other body parts.
  • Together these systems provide three general
    functions sensory, integrative and motor.

Autonomic and Somatic Nervous Systems
  • Autonomic Portion of the nervous system that
    controls the actions of the viscera. (such as
    heart, stomach, intestines, and various glands)
  • Somatic Portion of the nervous system that
    controls skin and skeletal muscles.

Two Divisions of Autonomic Nervous Systems
  • Sympathetic Division Mobilizes body systems.
    Arises from the thoracic and lumbar regions of
    the spinal cord.
  • Parasympathetic Division Conserves energy and
    promotes housekeeping functions during rest.
    Arises from the brain and sacral regions of the
    spinal cord.

Nervous System
  • The nervous system is composed predominantly of
    neural tissue.
  • It also includes some blood vessels and
    connective tissue.
  • Neural Tissue consists of two cell types
  • Nerve cells called Neurons
  • Neurogilia or glial cells

Neurons and Neuroglial Cells
  • Neurons- A nerve cell that consists of a cell
    body and its processes.
  • Neuroglial- specialized cell that produces
    myelin, communicates between cells, and maintains
    the ionic environment, as well as other functions.

  • They are specialized to react to physical and
    chemical changes in their surroundings.
  • While variable in size and shape, all neurons
    have three parts. Dendrites receive information
    from another cell and transmit the message to the
    cell body. The cell body contains the nucleus,
    mitochondria and other organelles typical of
    eukaryotic cells. The axon conducts messages away
    from the cell body.
  • The information is in the form of of bioelectric
    signals called nerve impulses.
  • Nerves are bundles of axons.

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Draw, Color and Label
  • You need to use a plain white sheet of paper and
    properly draw, color, and label a neuron.
  • You may use the drawing in this PowerPoint or on
    pg 392 in your book.

Classification of Neurons
  • Neurons vary in size and shape, and in function.
  • Structure is different.
  • Bipolar- a cell body with two processes, one axon
    and one dentrite. (Specialized parts of eyes,
    nose and ears.)
  • Unipolor- Cell body with a single process that
    divides into two branches and functions as an
    axon.(cell body in ganglion outside the brain or
    spinal cord)
  • Multipolar- Cell body with many processes, one of
    which is an axon, the rest dendrites.( Most
    common type of neuron in the brain and spinal

Classification of Neurons
  • When function is different
  • Sensory neuron conducts nerve impulses from
    receptors in peripheral body parts into the brain
    or spinal cord
  • Interneuron-Transmits nerve impulses between
    neurons within the brain and spinal cord
  • Motor Neurons- conduct nerve impulses from the
    brain or spinal cord out to effectors- muscle or

The Synapse
  • The operation of the nervous system depends on
    the flow of information through chains of neurons
    functionally connected by synapses.
  • The synapse is a junction between two cells.
  • A synaptic cleft is the gap between parts of the
    two cells at a synapse.
  • Synapse can occur between two neurons, a
    receptor cell and a neuron, or a neuron and an

The Synapse Transmission
  • Between adjacent neurons, there is a microscopic
    gap called the synaptic cleft.
  • However small, the electrical signal carrying a
    message cannot bridge the synaptic cleft as it

The Synapse
  • The neuron conducting impulses toward the synapse
    is the presynaptic neuron
  • The neuron transmitting the electrical signal
    away from the synapse is the postsynaptic neuron.
  • There are two varieties of synapses
  • Electrical
  • Chemical

The Electrical Synapse
  • Less common variety.
  • They intimately connect the cytoplasm of adjacent
    neurons and allow ions and small molecules to
    flow directly from one neuron to the next.
  • Found in regions of the brain responsible for
    certain stereotyped movements.
  • Jerking of the eyes
  • Involved in emotions and memory.
  • Abundant in embryonic nervous tissue.

The Chemical Synapse
  • The chemical synapse are specialized for release
    and reception of chemical neurotransmitters.
  • The solution to this is the synapse, an elegant
    way of bridging the gap chemically. The
    electrical impulse triggers the release of
    certain chemical substances into the gap. These
    substances are called neurotransmitters and are
    carried over the small synaptic cleft by

The Synapse Transmission
  • Once on the other side of the cleft, the
    neurotransmitters bind to certain proteins,
    called receptors, that are attached to the cell
    surface of the receiving cell. The binding of the
    transmitter to the receptor leads to the
    generation of a new electrical impulse. The gap
    has been bridged!

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  • The SynapseNerve Signaling An Introduction

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Synapse Transmission
The Synapse Transmission
  • Impulses usual travel from dendrite or cell body,
    then along the axon to a synapse.
  • Axons have synaptic knobs at their distal ends
    that secrete neurotransmitters.
  • The neurotransmitter is released when a nerve
    impulse reaches the end of an axon, this opens
    two channels Na and Ca2
  • This surge of Ca2 acts as a messenger, directing
    synaptic vesicles to empty contents.
  • Then the neurotransmitter diffuses across the
    synaptic cleft
  • A neurotransmitter reaching the dendrite or cell
    body on the distal side of the cleft triggers a
    nerve impulse.

  • Different neurotransmitters are being released on
    different occasions. The intensity and strength
    of the electrical impulse will decide which
    neurotransmitter to be released.

  • Not all neurotransmitters are known, but among
    the more profoundly mapped
  • Some medical disorders are caused by the
    dysfunction of neurotransmission in the central
    nervous system, for example lack of certain
  • One such disorder is Parkinson's disease.