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Anatomy and Physiology I Lab BSC 2085L Laboratory 9

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Title: Anatomy and Physiology I Lab BSC 2085L Laboratory 9


1
Anatomy and Physiology I Lab BSC 2085L Laboratory
9
  • Neuron Structure
  • Cranial Nerves
  • Spinal Cord
  • Spinal Nerves

Associate Professor Pamela L. Pannozzo pannozzp_at_pb
cc.edu
2
Neuron Structure
  • Cell body perikaryon soma
  • single, central nucleus with large nucleolus,
    cell organelles
  • Dendrites
  • for receiving signals, conduct impulses toward
    the cell body
  • Axon
  • for sending signals, conduct impulses away from
    the cell body to effectors
  • Covered by lipid myelin

3
Myelin Sheath
  • Note Node of Ranvier between Schwann cells

4
Myelin Sheath
  • Insulating layer around a nerve fiber
  • 20 protein 80 lipid (looks white)
  • In PNS, hundreds of layers wrap axon
  • the outermost coil is schwann cell (neurilemma)
  • covered by basement membrane endoneurium
  • In CNS, no neurilemma or endoneurium
  • Gaps between myelin segments nodes of Ranvier
  • Initial segment (area before 1st schwann cell)
    axon hillock form trigger zone where signals
    begin

5
Myelin Sheath Formation
  • Myelination begins during fetal development, but
    proceeds most rapidly in infancy.

6
Nerve-Muscle Relationships
  • Skeletal muscle must be stimulated by a nerve or
    it will not contract
  • Cell bodies of somatic motor neurons are in
    brainstem or spinal cord
  • Axons of somatic motor neurons are called somatic
    motor fibers
  • each branches, on average, into 200 terminal
    branches that supply one muscle fiber each
  • Each motor neuron and all the muscle fibers it
    innervates are called a motor unit

7
Fundamental Types of Neurons
8
Myoneuronal Junctions
  • region where a nerve fiber makes a functional
    connection with its target cell (NMJ)
  • Neurotransmitter (acetylcholine/ACh) released
    from nerve fiber causes stimulation of muscle
    cell
  • Components of synapse
  • synaptic knob is swollen end of nerve fiber
    (contains ACh)
  • motor end plate is specialized region of muscle
    cell surface

9
The Neuromuscular Junction
10
Motor Units
  • A motor neuron the muscle fibers it innervates
  • dispersed throughout the muscle
  • Fine control
  • small motor units contain as few as 20 muscle
    fibers per nerve fiber
  • eye muscles
  • Strength control
  • gastrocnemius muscle has 1000 fibers per nerve
    fiber

11
The Cranial Nerves
  • 12 pair of nerves that arise from brain exit
    through foramina leading to muscles, glands
    sense organs in head neck

12
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13
Olfactory Nerve
  • Provides sense of smell
  • Damage causes impaired sense of smell

14
Optic Nerve
  • Provides vision
  • Damage causes blindness in visual field

15
Oculomotor Nerve
  • Provides some eye movement, opening of eyelid,
    constriction of pupil, focusing
  • Damage causes drooping eyelid, dilated pupil,
    double vision, difficulty focusing inability to
    move eye in certain directions

16
Trochlear Nerve
  • Provides eye movement
  • Damage causes double vision inability to rotate
    eye inferolaterally

17
Trigeminal Nerve
  • Main sensory nerve to face (touch, pain and
    temperature) and muscles of mastication

18
Abducens Nerve
  • Provides eye movement
  • Damage results in inability to rotate eye
    laterally at rest eye rotates medially

19
Facial Nerve
  • Provides facial expressions, sense of taste on
    anterior 2/3s of tongue, salivary glands and
    tear, nasal palatine glands
  • Damage produces sagging facial muscles
    disturbed sense of taste (missing sweet salty)

20
Branches of Facial Nerve
21
Vestibulocochlear Nerve
  • Provides hearing sense of balance
  • Damage produces deafness, dizziness, nausea, loss
    of balance nystagmus

22
Glossopharyngeal Nerve
  • Provides control over swallowing, salivation,
    gagging, sensations from posterior 1/3 of tongue,
    control of BP and respiration
  • Damage results in loss of bitter sour taste
    impaired swallowing

23
Vagus Nerve
  • Provides swallowing, speech, regulation of
    viscera
  • Damage causes hoarseness or loss of voice,
    impaired swallowing fatal if both are cut

24
Spinal Accessory Nerve
  • Provides swallowing, head, neck shoulder
    movement
  • Damage causes impaired head, neck shoulder
    movement, head turns towards injured side

25
Hypoglossal Nerve
  • Provides tongue movements of speech, food
    manipulation swallowing

26
Spinal Cord
27
Overview of Spinal Cord
  • Information highway between brain and body
  • Extends through vertebral canal from foramen
    magnum to L1
  • Each pair of spinal nerves receives sensory
    information and issues motor signals to muscles
    and glands
  • Spinal cord is a component of the Central Nervous
    System while the spinal nerves are part of the
    Peripheral Nervous System

28
Spinal Cord
  • Cylinder of nerve tissue within the vertebral
    canal (thick as a finger)
  • 31 pairs of spinal nerves arise from the cord
  • Cervical lumbar enlargements
  • Medullary cone is tapered tip of spinal cord
  • Cauda equinae is L2 to S5 nerve roots resemble
    horses tail

29
Gross Anatomy of Lower Spinal Cord
30
Meninges of the Spinal Cord
  • 3 Fibrous layers enclosing spinal cord
  • Dura mater
  • tough collagenous membrane surrounded by epidural
    space filled with fat and blood vessels
  • Arachnoid mater
  • layer of simple squamous epithelium lining dura
    mater and loose mesh of fibers filled with
    CSF (creates subarachnoid space)
  • Pia mater
  • delicate membrane adherent to spinal cord
  • filium terminale and denticulate ligaments anchor
    the cord

31
Cross-Sectional Anatomy of the Spinal Cord
  • Central area of gray matter shaped like a
    butterfly and surrounded by white matter in 3
    columns
  • Gray matter neuron cell bodies with little
    myelin
  • White matter myelinated axons

32
Gray Matter in the Spinal Cord
  • Pair of dorsal or posterior horns
  • dorsal root of spinal nerve is totally sensory
    fibers
  • Pair of ventral or anterior horns
  • ventral root of spinal nerve is totally motor
    fibers
  • Connected by gray commissure punctured by a
    central canal continuous above with 4th ventricle

33
White Matter in the Spinal Cord
  • White column bundles of myelinated axons that
    carry signals up down
  • Dorsal or posterior columns, lateral columns, and
    anterior columns
  • Each column is filled with named tracts (named
    fibers with a similar origin, destination
    function)

34
Anatomy of a Nerve
  • A nerve is a bundle of nerve fibers (axons)
  • Epineurium covers nerves, perineurium surrounds a
    fascicle endoneurium separates individual nerve
    fibers blood vessels

35
Reflexes
  • Rapid, involuntary responses to stimuli
  • Two types of reflexes
  • Autonomic-smooth muscle, cardiac, or gland
  • Somatic-skeletal muscle
  • Reflexes follow a reflex arc pathway
  • Stimulus -gtsensory receptor -gtaction potential to
    sensory neuron -gt interneurons in CNS -gt action
    potential to motor neuron -gt effector

36
The Spinal Nerves
  • 31 pairs of spinal nerves (1st cervical above C1)
  • mixed nerves exiting at intervertebral foramen
  • Proximal branches
  • dorsal root is sensory input to spinal cord
  • ventral root is motor output of spinal cord
  • cauda equina is roots from L2 to C0 of the cord
  • Distal branches
  • dorsal ramus supplies dorsal body muscle skin
  • ventral ramus to ventral skin muscles limbs
  • meningeal branch to meninges, vertebrae
    ligaments

37
Branches of a Spinal Nerve
Spinal nerves 8 cervical, 12 thoracic, 5 lumbar,
5 sacral and 1 coccygeal. Each has dorsal and
ventral ramus.
38
Nerve Plexuses
  • Branches of spinal nerves that exit the spinal
    cord and form branching networks with other
    nerves
  • Five plexuses
  • cervical in the neck, C1 to C5
  • supplies neck and phrenic nerve to the diaphragm
  • brachial in the armpit, C5 to T1
  • supplies upper limb and some of shoulder neck
  • lumbar in the low back, L1 to L4
  • supplies abdominal wall, anterior thigh
    genitalia
  • sacral in the pelvis, L4, L5 S1 to S4
  • supplies remainder of butt lower limb
  • coccygeal, S4, S5 and C0

39
Structure of a Nerve Plexus
  • Notice the branching and merging of nerves in
    this example of a plexus

40
The Cervical Plexus
41
The Brachial Plexus
42
The Lumbar Plexus
43
The Sacral and Coccygeal Plexuses
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