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Essentials of Human Anatomy

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Essentials of Human Anatomy Nervous System I Dr Fadel Naim Ass. Prof. Faculty of Medicine IUG Regeneration Of Neurones If: no infection partially cut axon neurolemma ... – PowerPoint PPT presentation

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Title: Essentials of Human Anatomy


1
Essentials of Human Anatomy
Nervous System I
Dr Fadel Naim Ass. Prof. Faculty of Medicine IUG
2
Introduction
  • The function of the nervous system, along with
    the endocrine system, is to communicate
  • The nervous system is made up of
  • the brain
  • the spinal cord
  • the nerves

3
Functions of Nervous System
  • Sensory Function
  • sensory receptors gather information
  • information is carried to the CNS
  • Motor Function
  • decisions are acted upon
  • impulses are carried to effectors
  • Integrative Function
  • sensory information used to create
  • sensations
  • memory
  • thoughts
  • decisions

4
Organization of the Nervous System
  • Organized to detect changes in internal and
    external environments, evaluate the information,
    and initiate an appropriate response
  • Subdivided into smaller systems by location
  • Central nervous system (CNS)
  • Structural and functional center of entire
    nervous system
  • Consists of the brain and the spinal cord
  • Integrates sensory information, evaluates it, and
    initiates an outgoing response
  • Peripheral nervous system (PNS)
  • Nerves that lie in outer regions of nervous
    system
  • Cranial nervesoriginate from brain
  • Spinal nervesoriginate from spinal cord

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Divisions of Peripheral Nervous System
  • Sensory Division
  • picks up sensory information and delivers it to
    the CNS
  • Motor Division
  • carries information to muscles and glands
  • Divisions of the Motor Division
  • Somatic carries information to skeletal muscle
  • Autonomic carries information to smooth
    muscle, cardiac muscle, and glands

7
Divisions Nervous System
8
Organization of the Nervous System
  • Systems according to the types of organs they
    innervate
  • Somatic nervous system (SNS)
  • Somatic motor divisioncarries information to the
    somatic effectors (skeletal muscles)
  • Somatic sensory divisioncarries feedback
    information to somatic integration centers in the
    CNS

9
Organization of the Nervous System
  • Autonomic nervous system (ANS)
  • Efferent division of ANScarries information to
    the autonomic or visceral effectors (smooth and
    cardiac muscles and glands)
  • Sympathetic divisionprepares the body to deal
    with immediate threats to the internal
    environment
  • Parasympathetic divisioncoordinates the bodys
    normal resting activities
  • Visceral sensory divisioncarries feedback
    information to autonomic integrating centers in
    the CNS

10
Organization of the Nervous System
  • Afferent and efferent divisions
  • Afferent divisionconsists of all incoming
    sensory pathways
  • Efferent divisionconsists of all outgoing motor
    pathways

11
Sensory Division
  • Somatic sensory components
  • General somatic senses
  • touch
  • pain
  • pressure
  • vibration,
  • temperature
  • proprioception.
  • Special senses
  • Taste
  • Vision
  • Hearing
  • Balance
  • smell

12
Sensory Division
  • Visceral sensory components
  • transmit nerve impulses from blood vessels and
    viscera to the CNS
  • visceral senses primarily include
  • temperature
  • stretch (of the organ wall).

13
Motor Division
  • The somatic motor component (somatic nervous
    system SNS)
  • conducts nerve impulses from the CNS to skeletal
    muscles
  • also known as the voluntary nervous system
  • The autonomic motor component (autonomic nervous
    system ANS) internal organs, regulates smooth
    muscle, cardiac muscle, and glands.
  • Innervates
  • Internal organs
  • Regulates smooth muscle
  • Regulates cardiac muscle
  • Regulates glands
  • also known as the visceral motor system or
    involuntary nervous system

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Nerve Cells
  • Nervous Tissue
  • Two distinct cell types
  • Neurons
  • excitable cells
  • initiate and transmit nerve impulses
  • Glial cells
  • nonexcitable cells
  • support and protect the neurons

16
The Neuron
  • structural and functional unit of the nervous
    system.
  • formed of
  • nerve cell
  • processes
  • the dendrites
  • the axon.

17
Characteristics of Neurons
  • Neurons have a high metabolic rate.
  • Neurons have extreme longevity.
  • Neurons typically are non-mitotic.

18
Neuron Structure
  • Neurons come in all shapes and sizes
  • All neurons share certain basic structural
    features.
  • typical neuron
  • Cell body (soma)
  • Dendrites
  • Axon

19
Neuron Structure Cell Body
  • The cell body
  • the neurons control center
  • responsible for
  • receiving
  • integrating
  • sending nerve impulses.
  • Consists of
  • Plasma membrane
  • Cytoplasm
  • Nucleus with prominent nucleolus
  • Chromatophobic substance (Nissil bodies) RER
  • Free ribosomes

20
Cells of the Nervous System
  • Components of neurons
  • Axon
  • A single process extending from the axon hillock,
    sometimes covered by a fatty layer called a
    myelin sheath
  • Conducts nerve impulses away from the cell body
    of the neuron

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Cells of the Nervous System
  • Components of neurons
  • Dendrites
  • Each neuron has one or more dendrites, which
    branch from the cell body
  • Conduct nerve signals to the cell body of the
    neuron
  • Distal ends of dendrites of sensory neurons are
    receptors

23
Classifications of Neurons
  • Neurons vary widely in morphology and location.
  • classified based on
  • structure
  • function.
  • Structural classification number of processes
    extending from the cell body.
  • unipolar neuron has a single process
  • bipolar neurons have two processes
  • multipolar neurons have three or more processes

24
Classification of Neurons Structural Differences
  • Unipolar
  • one process
  • ganglia
  • Bipolar
  • two processes
  • eyes, ears, nose
  • Multipolar
  • many processes
  • most neurons of CNS

25

Light micrograph of the gray matter of the spinal cord (270). Observe the multipolar neuron (mN) cell bodies and their processes.
26
Classification of Neurons Functional Differences
  • Sensory Neurons
  • afferent
  • carry impulse to CNS
  • most are unipolar
  • some are bipolar
  • Interneurons
  • link neurons
  • multipolar
  • in CNS
  • Motor Neurons
  • multipolar
  • carry impulses away from CNS
  • carry impulses to effectors

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29
Nerves
  • Nerves are organs of the PNS.
  • Sensory (afferent) nerves convey sensory
    information to the CNS.
  • Motor (efferent) nerves convey motor impulses
    from the CNS to the muscles and glands.
  • Mixed nerves both sensory and motor
  • Axons terminate as they contact other neurons,
    muscle cells, or gland cells.
  • An axon transmits a nerve impulse at a
    specialized junction with another neuron called
    synapse.

30
Peripheral Nerves
  • Organization coverings
  • Epineurium wraps entire nerve
  • Perineurium wraps fascicles of tracts
  • Endoneurium wraps individual axons

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Repair of Nerve Fibers
  • Mature neurons are incapable of cell division
    therefore, damage to nervous tissue can be
    permanent
  • Neurons have limited capacity to repair
    themselves
  • Nerve fibers can be repaired if the damage is not
    extensive, the cell body and neurilemma are
    intact, and scarring has not occurred

33
Regeneration of PNS Axons
  • PNS axons are vulnerable to cuts and trauma.
  • A damaged axon can regenerate
  • if some neurilemma remains.
  • PNS axon regeneration depends upon three factors.
  • amount of damage
  • neurolemmocyte secretion of nerve growth factors
  • stimulates outgrowth of severed axons
  • distance between the site of the damaged axon and
    the effector organ

34
Regeneration Of Neurones
Regeneration in human nerves is a slow process.
The rate of growth is about 1.5 mm per day in
human, while in rabbits it is about 3 mm. per day.
  • If
  • no infection
  • partially cut axon
  • neurolemma is intact
  • regeneration starts in the nerve cell by resuming
    its normal shape and contents.
  • The neurofibrils (axon sprouts) of the central
    stump will grow.
  • They enter the neurolemmal tube and extend to the
    distal cut end of the nerve.

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The Neuroglia
  • no C.T. in the CNS
  • instead there are the neuroglia.
  • the supporting tissue between the neurones of the
    C.N.S.

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Functions Of Neuroglia
  • Support the neurones
  • similar to the function of C.T. in other organs
  • form the myelin sheaths around axons
  • act as insulator between neurones
  • nutritive function for neurones
  • defend against inflammations
  • help in regeneration of neurones
  • secrete the C.S.F

40
THE END
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