Lucky Chapter 13. Spinal Cord and Spinal Nerves - PowerPoint

							Biology 315. Anatomy and Physiology I.
   Bones (vertebral column)
   Meninges, in layers
                   Epidural space
     Dura mater
                   Subdural space
     Arachnoid mater
          Subarachnoid space (contains CSF)
     Pia mater -- very vascular
Thickenings of
 the pia hold
the spinal cord
   in place
Lumbar enlargement
    T9-T12

Conus medullaris :
    L1/L2 interspace

    Cauda Equina

   Filum Terminale
              C1-C8
              T1-T12
              L1-L5
              S1-S5
   Note differential growth of vertebral column such
    that adult spinal cord ends at L1-L2 interspace.
 White
 commissure




Gray commissure
Posterior
Horns




            Anterior
            Horns
                      2
1.   __________
2.   __________
3.   __________
4.   __________
5.   __________
6.   __________
                      3

                  5
   Ascending tracts = sensory
       ▪Spino-thalamic




          Descending tracts = motor
           *Cortico-spinal
   Anterior and lateral spinothalamic tracts
     Pain
     Temperature
     Itching
     Tickling
     Deep pressure
     Crude touch
   Posterior column system
     Proprioception
     Discriminative touch
     2-point discrimination
     Light pressure
     Vibration
   Direct pathways: “Pyramidal”
     Lateral corticospinal tract
     Anterior corticospinal tract
     Corticobulbar tract
    These carry motor impulses that originate from the
      cerebral cortex and result in
    precise, voluntary movements of skeletal muscle.
   Indirect pathways (Extrapyramidal)
     Rubrospinal
     Tectospinal
     Vestibulospinal
    These carry impulses from brain stem,
      ▪ coordinate movements with visual stimuli
      ▪ Regulate muscle tone
      ▪ Maintain contraction of postural muscles
      ▪ Equilibrium
   A fast, involuntary, unplanned sequence of
    actions that occurs in response to a particular
    stimulus.
     Somatic: contraction of skeletal muscles
     Autonomic (visceral):urination, gastrocolic…
      ▪ (easy one to test: pupillary light reflex)


     Consider Newtons 3rd law: For every action there
     is an equal and opposite reaction.
   Sensory receptor
   Sensory neuron
   Integrating center (multisynaptic or
    monosynaptic; spinal cord or brain stem)
   Motor neuron
   Effector (skeletal muscle, smooth muscle,
    cardiac muscle, glands)
   Receptor: muscle spindle,monitors stretch
   Sensory nerve: from receptor through
    posterior root
   Integrating center: spinal cord; sensory
    neuron synapses with
   Motor neuron in the anterior gray horn
   Motor axon travels out anterior root to PNS
    to muscle
   If the agonist muscle contracts, the
   Antagonist muscle must _____________

   If not, the two muscle groups are in conflict
    and the appropriate movement can’t occur.
   Receptor: Golgi tendon organ detects
    increased muscle tension
   Nerve impulse carried through posterior root
    into posterior horn
   Integrating center: spinal cord, inhibitory
    neuron synapses with a motor neuron , which
    is hyperpolarized (inhibited)
   Effector muscle of that tendon relaxes and
    relieves excess tension.
Antagonist muscles of the arm,
          one flexor muscles, biceps brachii
         one extensor muscle, triceps brachii
 Stretch receptor: The arrow points at a spindle organ
         which senses stretch of muscles.
sensory neuron (red) transmits impulse to the
Integrating center, the spinal cord. Neuron synapses
with a
motor neuron (blue) which in turn innervates the
Effector: biceps muscle where the spindle organ is
located.
Sensory and motor neuron form a local circuit in form of
a feedback loop which functions in a subconscious
manner .Voluntary movements are mediated via
activation of excitatory interneurons (light brown, inter-
ex) in the primary motor cortex of the brain. These
neurons send processes into the spinal cord where they
form excitatory synapses onto local neurons. Here
shown are synaptic connections with a local inhibitory
interneuron (black, inter-in) and a motor neuron
innervating the extensor muscle.
   Receptor: pain receptors
   Sensory neuron to spinal cord
   Integrating center: spinal cord, various
    segments (intersegmental) ,multiple neurons
   Motor neurons send impulses to
   Neuromuscular junctions–
     ACh : flexors contract; others inhibited. You pull
     your foot back…..
   In spinal cord interneurons synapse with
    motor neurons on the opposite side of the
    spinal cord ( contralateral)
   Motor neurons carry nerve impulse to nerve
    ending,
   Effector: contraction of extensor muscles of
    the opposite side
   If a given reflex “works,” all the parts of that
    reflex must be intact. (receptor; sensory
    neuron; integrative center; motor neuron;
    effector).
   Various reflexes test specific spinal cord levels

   E.g. patellar reflex: L2-L4
   Achilles: lumbosacral levels
   Terms to review
     Anterior root
     Posterior root
     Spinal nerve
     Ramus
     Plexus
   Dorsal ramus: supplies muscles and skin of
    back
   Ventral ramus: extremities, lateral and
    ventral trunk (the big one)
     Ventral rami of T2-T12 = intercostal nerves
   Ramus (pl. rami) communicantes: part of
    ANS
   Ventral rami of spinal nerves branch and form
    networks
   Cervical plexus = C1-C4
     Innervates skin, muscles of neck, head,shoulder
      region plus diaphragm.
     Connects with XI (spinal accessory) and XII
       (Hypoglossal)
    THE NERVE to know = Phrenic:
                          C3,C4,C5
   Ventral rami of spinal nerves branch and form
    networks
   Brachial = C5-T1
     Upper extremity
     Some neck/ shoulder areas
     Complicated structure (trunks/ divisions/cords)
    THE NERVES to know
   Axillary nerve: deltoid, teres major

   Musculocutaneous nerve: flexors of arm and
    forearm

   Radial nerve: muscles of posterior arm and forearm
     Damage to radial nerve: “wrist drop”
   Median Nerve: muscles of anterior forearm and
    palm thumb
     Damage = numbness, tingling pain in fingers, weak
     thumb movements, inability to pronate forearm
   Ulnar nerve : anteromedial muscles of forearm and
    fingers
     Damage: difficulty holding/picking up piece of paper;
     inability to flex and adduct the wrist
   Long thoracic nerve: serratus anterior
     Damage: “winged” scapula
   Femoral nerve: flexors of the thigh and extensors
    of the legs (quads; iliopsoas; sartorius);skin over
    anterior and medial aspect of thigh and medial side
    of leg and foot
   Know that these nerves are part of the lumbar
    plexus:
     Iliohypogastric
     Ilioinguinal
     Genitofemoral
     Lateral cutaneous nerve of the thigh
     Obturator nerve
   Buttocks, perineum, lower extremity
   Sciatic nerve : largest nerve; composed of tibial
    and common fibular/peroneal nerve
     Tibial nerve: posterior compartment muscles; medial
      and lateral plantar nerves
     Common Fibular/Peroneal nerve : anterior
      compartment, lateral compartment of leg
     Pudendal nerve = muscles of perineum, skin over
      external genitalia, vagina
   Damage: “foot drop”
New idea for
Halloween…..
   Helpful for determining general level of
    injury or anesthesia
   Herpes zoster follows the dermatomes
   Same organization for MYOTOMES
   Try to memorize a few….
     Shoulder C3-C4
     Nipple T4
     Umbilicus T10
   1. Permanent loss of sensation in
    dermatomes distal to the injury



   2. Permanent loss of voluntary muscle
    contraction distal to the injury
   Polio
   Meningitis
   Nerve block
   Epidural block
   Neuralgia
   Neuritis
   Paresthesia
   Shingles