Moto Neuron

  • View
    222

  • Download
    0

Embed Size (px)

Text of Moto Neuron

  • 7/27/2019 Moto Neuron

    1/44

  • 7/27/2019 Moto Neuron

    2/44

    The pyramidal motor systemcontrols all of our voluntary

    movements.

    The pyramidal system is a two neuron system

    - upper motor neurons in the PrimaryMotor Cortex

    - lower motor neurons in the anterior

    horn of the spinal cord

    consisting of

  • 7/27/2019 Moto Neuron

    3/44

    The upper motor neurons reside in theprecentral gyrus of the frontal lobe also

    called the "motor strip".

    Upper motor neurons (UMN) are a type of

    first order neuron

    They are unable to leave the centralnervous system

  • 7/27/2019 Moto Neuron

    4/44

    The axons of these lower motor

    neurons then exit the spinal cord viathe Ventral root

    The upper motor neuron axons thensynapse on lower motor neurons in the

    Anterior horn of the spinal cord

    The ventral root then joins the dorsalroot to form the spinal nerve, which

    finally innervates the skeletal muscle.

  • 7/27/2019 Moto Neuron

    5/44

    This group of fibers carries messages for voluntary motormovement to the lower motor neurons in the brain stem

    and spinal cord.

  • 7/27/2019 Moto Neuron

    6/44

    are the motor neuronsconnecting thebrainstemand spinal cordto muscle fibers,

    bringing the nerve impulsesfrom theupper motor neuronsout to the muscles. A

    lower motor neuron's axon terminates onan effector (muscle).

    Lower motor neurons (LMNs)

    The lower motor neurons relay the movementinstructions provided by the upper motor neurons,to the muscles. When the lower motor neurons aredamaged the result is muscle weakness, twitching

    and atrophy.

    http://en.wikipedia.org/wiki/Motor_neuronhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Muscle_fibershttp://en.wikipedia.org/wiki/Action_potentialhttp://en.wikipedia.org/wiki/Upper_motor_neuronhttp://en.wikipedia.org/wiki/Musclehttp://backandneck.about.com/od/m/g/uppermotorneuro.htmhttp://backandneck.about.com/od/m/g/muscstrength.htmhttp://backandneck.about.com/od/m/g/muscstrength.htmhttp://backandneck.about.com/od/m/g/uppermotorneuro.htmhttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Upper_motor_neuronhttp://en.wikipedia.org/wiki/Action_potentialhttp://en.wikipedia.org/wiki/Muscle_fibershttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Motor_neuron
  • 7/27/2019 Moto Neuron

    7/44

    Lower motor neurons are classifiedbased on the type of muscle fiber they

    innervate:

    Alpha motor neurons(-MNs) innervate extrafusal

    muscle fibers, the most numerous type of musclefiber and the one involved in muscle contraction.

    Gamma motor neurons(-MNs) innervateintrafusal muscle fibers, which together with

    sensory afferents compose muscle spindles. Theseare part of the system for sensing body position(proprioception).

    http://en.wikipedia.org/wiki/Alpha_motor_neuronhttp://en.wikipedia.org/wiki/Extrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Extrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Muscle_contractionhttp://en.wikipedia.org/wiki/Gamma_motor_neuronhttp://en.wikipedia.org/wiki/Intrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Muscle_spindlehttp://en.wikipedia.org/wiki/Proprioceptionhttp://en.wikipedia.org/wiki/Proprioceptionhttp://en.wikipedia.org/wiki/Muscle_spindlehttp://en.wikipedia.org/wiki/Intrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Gamma_motor_neuronhttp://en.wikipedia.org/wiki/Muscle_contractionhttp://en.wikipedia.org/wiki/Extrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Extrafusal_muscle_fiberhttp://en.wikipedia.org/wiki/Alpha_motor_neuron
  • 7/27/2019 Moto Neuron

    8/44

    Glutamatereleased from the upper motorneurons triggers depolarizationin the

    lower motor neurons in the ventral hornwhich in turn causes an action potential to

    propagate the length of the axonto theneuromuscular junctionwhere

    acetylcholineis released to carry the signal

    across the synaptic cleftto thepostsynaptic receptors of the muscle cellmembrane, signaling the muscle to

    contract

    Physiology

    http://en.wikipedia.org/wiki/Glutamatehttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Axonhttp://en.wikipedia.org/wiki/Neuromuscular_junctionhttp://en.wikipedia.org/wiki/Acetylcholinehttp://en.wikipedia.org/wiki/Synaptic_clefthttp://en.wikipedia.org/wiki/Muscle_cellhttp://en.wikipedia.org/wiki/Muscle_cellhttp://en.wikipedia.org/wiki/Synaptic_clefthttp://en.wikipedia.org/wiki/Acetylcholinehttp://en.wikipedia.org/wiki/Neuromuscular_junctionhttp://en.wikipedia.org/wiki/Axonhttp://en.wikipedia.org/wiki/Depolarizationhttp://en.wikipedia.org/wiki/Glutamate
  • 7/27/2019 Moto Neuron

    9/44

    not all cranial nerves have lowermotor neuron components.

    Some of the cranial nerves containonly sensory fibers and therefore

    cannot be classified as lower motorneurons

    CN I, the olfactory nerve, CN II the opticnerve, and CN VIII, the auditory nerve

  • 7/27/2019 Moto Neuron

    10/44

    Peripheral Nervous System

    Cranial nervesarising from the brain

    Somatic fibers connecting to the skin and skeletal muscles

    Autonomic fibers connecting to viscera

    Spinal nervesarising from the spinal cord

    Somatic fibers connecting to the skin and skeletal musclesAutonomic fibers connecting to viscera

  • 7/27/2019 Moto Neuron

    11/44

    Nervous System Subdivisions

  • 7/27/2019 Moto Neuron

    12/44

    Structure of a PeripheralNerve

  • 7/27/2019 Moto Neuron

    13/44

    Nerve Fiber Classification

    Sensory Nervesconduct impulses into brain or spinal

    cord

    Motor Nervesconduct impulses to muscles or glands

    Mixed Nervescontain both sensory nerve fibers and

    motor nerve fibers; most nerves

  • 7/27/2019 Moto Neuron

    14/44

    Nerve Fiber Classification

    General somatic efferentfibers

    carry motor impulses from

    CNS to skeletal muscles

    General visceral efferentfibers

    carry motor impulses away from

    CNS to smooth muscles and

    glands

    General somatic afferentfibers

    carry sensory impulses to

    CNS from skin and skeletal

    muscles

    General visceral afferentfibers

    carry sensory impulses to CNS

    from blood vessels and internal

    organs

  • 7/27/2019 Moto Neuron

    15/44

    Nerve Fiber Classification

    Special somatic efferent fibers

    carry motor impulses from brain to muscles

    used in chewing, swallowing, speaking, and

    forming facial expressions

    Special visceral afferent fibers

    carry sensory impulses to brain from olfactory and

    taste receptors

    Special somatic afferent fibers

    carry sensory impulses to brain from receptors of

    sight, hearing, and equilibrium

  • 7/27/2019 Moto Neuron

    16/44

    Cranial Nerves

  • 7/27/2019 Moto Neuron

    17/44

    Cranial Nerves I and II

    Olfactory (I)

    sensory

    fibers transmit

    impulses associated

    with smell

    Optic (II)

    sensory

    fibers transmit

    impulses associated

    with vision

  • 7/27/2019 Moto Neuron

    18/44

    Cranial Nerves III and IV

    Trochlear (IV)

    some sensory

    proprioreceptorsprimarily motor

    motor impulses to

    muscles that move the

    eyes

    Oculomotor (III)

    some sensory

    proprioreceptorsprimarily motor

    motor impulses to

    muscles thatraise eyelids

    move the eyes

    focus lens

    adjust light entering

    eye

  • 7/27/2019 Moto Neuron

    19/44

    Cranial Nerve V

    Trigeminal (V)

    mixed

    opthalmic divisionsensory from surface of eyes,

    tear glands, scalp, forehead, and

    upper eyelidsmaxillary division

    sensory from upper teeth,

    upper gum, upper lip, palate,

    and skin of face

    mandibular divisionsensory from scalp, skin of jaw,lower teeth, lower gum, and

    lower lip

    motor to muscles of mastication

    and muscles in floor of mouth

  • 7/27/2019 Moto Neuron

    20/44

    Cranial Nerves VI and VII

    Abducens (VI)

    primarily motor

    motor impulses to

    muscles that move

    the eyes

    some sensory withproprioreceptors

    Facial (VII)

    mixed

    sensory from tastereceptors

    motor to muscles of

    facial expression,

    tear glands, and

    salivary glands

  • 7/27/2019 Moto Neuron

    21/44

    Cranial Nerves VIII and IX

    Vestibulocochlear (VIII)

    sensory

    vestibular branch

    sensory from

    equilibrium receptors of

    ear

    cochlear branch

    sensory from hearing

    receptors

    Glossopharyngeal (IX)

    mixed

    sensory from pharynx,tonsils, tongue, and carotid

    arteries

    motor to salivary glands

    and muscles of pharynx

  • 7/27/2019 Moto Neuron

    22/44

    Cranial Nerve X

    Vagus (X)

    mixed

    somatic motor to

    muscles of speech

    and swallowing

    autonomic motor to

    viscera of thorax and

    abdomen

    sensory from

    pharynx, larynx,esophagus, and

    viscera of thorax and

    abdomen

  • 7/27/2019 Moto Neuron

    23/44

    Cranial Nerves XI and XII

    Accessory (XI)

    primarily motor

    cranial branchmotor to muscles of

    soft palate, pharynx,

    and larynx

    spinal branch

    motor to muscles ofneck, and back; some

    proprioreceptor

    Hypoglossal (XII)

    primarily motor

    motor to muscles ofthe tongue; some

    proprioreceptor