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Spinal Cord and Nerves


Spinal Cord and Nerves The Nervous System Coordinates the activity of muscles, organs, senses, and actions Made up of nervous tissue Has 3 main functions: 1. – PowerPoint PPT presentation

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Title: Spinal Cord and Nerves

  • Spinal Cord and Nerves

The Nervous System
  • Coordinates the activity of muscles, organs,
    senses, and actions
  • Made up of nervous tissue
  • Has 3 main functions
  • 1. Receives sensory Input
  • 2. Integration
  • 3. Dictates motor output

Divisions of the Nervous System
  • Central Nervous System (CNS)
  • Brain and spinal cord
  • Interprets incoming sensory signals
  • Dictates motor responses
  • Peripheral Nervous System (PNS)
  • Ganglia
  • Nerves
  • Cranial nerves and spinal nerves
  • Communication between regions of body and CNS

Review of Nervous Cells
  • Neuron
  • Cell body
  • Dendrite
  • Axon
  • Myelin Sheath
  • Neuroglia
  • Interneuron
  • Reflex Arc
  • Synapse

Organization of a Nerve
  • Endoneurium
  • Surrounds each axon (nerve fiber)
  • Myelinated and Unmyelinated axons
  • Motor and Sensory nerve fibers
  • Loose CT
  • Perineurium
  • Bundles axons into fascicles
  • CT
  • Epineurium
  • Bundles fascicles into a nerve
  • Fibrous CT
  • CT layers contain blood vessels

Types of Nerve Signals/Fibers
  • Sensory (afferent)
  • Picked up by sensory receptors thru body
  • Carried by nerve fibers of PNS into CNS
  • Motor (efferent)
  • Carried away from the CNS by nerve fibers into
  • Innervate muscles and glands
  • Causes these organs to contract or secrete
  • Remember SAME

Sensory and Motor Signals/Fibers
  • Somatic sensory
  • Body senses
  • touch, pressure, temperature, vibration of body,
    muscles stretching, balance
  • Visceral sensory
  • Organ senses
  • Stretch, pain, temperature in organs
  • (eg) nausea, hunger, cramps
  • Somatic motor
  • Body movement
  • Voluntary contraction of skeletal muscles
  • Visceral motor
  • Organ movement
  • Contraction of smooth muscle, glands
  • Autonomic Nervous System (involuntary)

CNS Spinal Cord
  • Runs through vertebral canal of the vertebral
  • Protected by bone, meninges, and cerebrospinal
  • Spinal cord made of a core of gray matter
    surrounded by white matter
  • 31 pairs of spinal nerves branch off spinal cord
    through intervertebral foramen
  • Functions in many ways
  • Involved in sensory and motor innervation of body
    inferior to the head (through spinal nerves)
  • Provides a 2-way conduction pathway for signals
    between body and brain
  • Major center for reflexes

Spinal Cord Segments
Meninges of Spinal Cord
  • Dura mater (superficial)
  • Spinal dural sheath
  • Does not attach to bone
  • Epidural space
  • Fat and veins
  • Between dura mater and vertebra
  • Subdural space
  • Between dura mater and arachnoid

Meninges of Spinal Cord
  • Arachnoid mater (middle)
  • Impermeable layer barrier
  • Raised off pia mater by rootlets
  • Subarachnoid space
  • Between arachnoid and pia mater
  • Contains CSF
  • Pia mater (deep)
  • Highly vascular
  • Adheres to brain/spinal cord tissue

Regions of Spinal Cord
  • Cervical
  • Thoracic
  • Lumbar
  • Sacral
  • Coccygeal
  • Cervical Lumbar enlargements
  • Cauda equina
  • Conus medullaris
  • Filum terminale

Gray Matter
  • Consists of neuron cell bodies, unmyelinated
    axons, dendrites, and neuroglia
  • Shaped like an H
  • Gray commissure (crossbar)
  • Central canal
  • Posterior horns
  • Anterior horns

Gray Matter
  • Posterior horns
  • Consist of interneurons that transmit in from
    outside spinal cord into it
  • Dorsal root contain sensory fibers
  • Somatic Sensory (SS)
  • Visceral Sensory (VS)
  • Dorsal root ganglia - swelling in dorsal root
    that these interneurons pass through
  • Anterior horns
  • Cell bodies of motor neurons send info out of
    spinal cord to muscles and glands
  • Ventral Root contains Motor Fibers
  • Visceral Motor
  • Somatic Motor

White Matter
  • Surrounds gray matter
  • Composed of myelinated and unmyelinated axons
  • Divided into white columns (funiculi)
  • Posterior funiculus
  • Anterior funiculus
  • Lateral funiculus
  • Allow for communication between
  • Parts of the spinal cord
  • Spinal cord and brain

White Matter
  • 3 types of nerve fibers
  • Ascending
  • Carry sensory info from sensory neurons of body
    to brain
  • touch, pressure, pain, temperature
  • Descending
  • Carry motor instructions from brain to spinal
  • Contraction of muscles and secretion of glands
  • control precise, skilled movement writing,
    maintain balance, create movement
  • Commissural
  • Cross from one side of cord to the other

Spinal Nerves (31 Pairs)
  • Part of the PNS (Somatic)
  • Lie in intervertebral foramina
  • Send lateral branches to body
  • Named according to their point of issue from the
    vertebral column
  • 8 pairs of cervical spinal nerves C1-C8
  • 12 pairs of thoracic spinal nerves T1-T12
  • 5 pairs of lumbar spinal nerves L1-L5
  • 5 pairs of sacral spinal nerves S1-S5
  • 1 pair of coccygeal spinal nerves C01

Spinal Nerves
  • Each spinal nerve connected to spinal cord via
    dorsal (sensory) and ventral (motor) root
  • Spinal nerves branch into dorsal ramus and
    ventral ramus
  • Ventral ramus
  • Connects to rami communicates, which then lead to
    sympathetic chain ganglia
  • Supply anterior and lateral regions of the neck,
    trunk, and limbs
  • Dorsal ramus
  • Supply the dorsum of the neck and trunk (back)

The Big Picture
  • Just lateral to intervertebral foramen, each
    spinal nerve then splits in 2
  • Dorsal Rami
  • Ventral Rami
  • Contain BOTH Sensory and Motor fibers!!

Autonomic Nervous System
  • Visceral Motor Function
  • Not easily controlled by will
  • Get nervous and sweat
  • Innervate smooth muscle, cardiac muscle, glands
  • Regulate visceral function
  • Heart rate, blood pressure, digestion, urination
  • Has 2 divisions
  • Parasympathetic
  • Sympathetic

  • Parasympathetic
  • Enables body to unwind and calm down
  • Most active when body at rest
  • Routine maintenance functions
  • Craniosacral division
  • Fibers emerge from brain and sacral spinal cord
  • Sympathetic
  • fight or flight
  • Mobilizes the body during extreme situations
  • Becomes active when extra metabolic effort needed
  • Thoracolumbar division
  • Fibers arise from thoracic and lumbar parts of
    spinal cord

Somatic Nervous System
  • Innervates skeletal muscle
  • Neurons runs from CNS directly to muscle
  • Consists of single neuron plus skeletal muscle
  • Voluntary control
  • Running, moving limbs, typing on a computer!
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