Wk 4

• Nerve roots to nerve terminals

  • C5 and C6: Musculocutaneous and Median (superior, anterior, lateral)
  • C7: Radial and Axillary (Middle, Posterior, Posterior)
  • C8 and T1: Median and Ulnar (Inferior, Anterior, Medial)
• Median Nerve injury


  Hand of benediction. Can't bend the first three fingers.
• Radial Nerve Injury


  Wristdrop. Effect all extensors, can't extend.
• Ulnar nerve injury


  Claw hand. Test is for the person to hold a piece of paper between their two fingers.
• Axillary Nerve


  Arises from the posterior cord, innervates teres minor and deltoid. Shoulder muscles
• Radial Nerve


  Innvervates all the extensor muscles in the upper limb (both proximal arm and forearm). For example the triceps brachii.
• Musculocutaneous Nerve


  Innervates biceps brachii, brachialis, coracobrachialis (proximal arm flexors). More medial
• Median Nerve


  Does not innervate any muscles in the proximal arm, innervates majority of the forearm flexor muscles. Supplies a few of the intrinsic muscles of the hand (those that are not innervated by the ulnar)
• Ulnar Nerve


  Does not innervate any muscles in the proximal arm, supplies two muscles in the forearm (flexor carpi ulnaris and half of the flexor digitorium produndus (on the ulnar half). Essentially innervates the intrinsic muscles of the hand.
• Spinal Nerves are part of the Peripheral Nervous System (PNS)
• Spinal Nerves


  • 31 pairs (attach to cord by paired roots)
• Cervical and Lumbar enlargements

  These are nerve serving upper and lower limbs. This is the are where these nerves emerge.
• Cervical


  Shoulder and upper limbs
• Lumbar


  Pelvis and lower limbs
• Conus medullaris


  End of the spinal cord proper (shaped like an upside down cone)
• Cauda Equina


  A collection of nerve roots at the inferior end of the vetebral canal. They are very soft.
• The general rule for a spinal cord injury is that anything below the lesion will be affected.
• The spinal cord is not aligned with the vertebral levels. The spinal cord grows slower than the vertebral column.
• Conus Medularis and Cauda Equina

  At birth the cord ends between L2-L3. At adult, the cord ends between L1-L2 but can be as high as T12 or as low as L3. It has important implications for lumbar punctures particularly between L3 and L4 vertebral bodies.
• Lumbar puncture


  Fluid drawn is CSF. Patient lies in fetal position. Drawn from the subarachnoid space by a hollow needle at L3-L4 (where spinal cord is not there). The needle won't puncture Cauda Equina because it's soft.
• Spinal Cord Protection


  • Epidural Space: Contains fat cushions the spinal cord
  • Spinal Meiniges
  • Intervertebral discs: fibrous cartilage cushion between vertebra (acting as a shock absorber and flexibility)
  • Intervertebral ligaments: tough, fibrous brands connecting vertebra providing stability and support
  • Denticulate Ligaments: extensions of pia mater that secure the spinal cord to the dura mater. Looks like teeth coming out of the pia mater.
• Lateral horns


  Mostly cells bodies from the sympathetic motor neuron division servng visceral (inner) organs. It is only apparent in thoracic (T1-T12) and superior lumbar (L1-L2) regions.
• Dorsal root ganglion


  Collection of cell bodies of unipolar sensory neurons. The dorsal horn often synapses with sensory neurons.
• Flow of sensory information

  Sensory root flows down the sensory root into the dorsal root ganglion. There is the integration of information via interneurons where then information is sent to the brain via the dorsal horn. In comparison, a multipolar motor root sends information from the brain to the body via the ventral horn.
• Spinal Cord diagram


  • White matter encloses grey matter (unlike brain where grey matter encloses white matter)
  • Composed of dorsal, ventral and sometimes lateral horns (on thoracic and superior lumbar) (ventral horns are larger than dorsal horns, think of a butterfly flying fowards)
  • Ventral white commisure; connecting the two hemisections of the spinal cord.
  • Lateral, ventral and dorsal funiculus: white matter tracts composed of projection fibres.
  • Dorsal median sulcus
  • Ventral median fissure.
• Motor output goes out of the ventral horns and sensory signlas come into the spinal cord via the dorsal horns.
• Funiculi


  • White matter columns.
  • Lateral (efferent) from the cortex.
  • Ventral (afferent) to the brain (thalamus)
  • Dorsal (afferent) to the brain
• Sensory tracts


  Afferent. Sensory neurons are long and have an "in-going axon" like a giant dendrite. There cell bodies are in the dorsal root ganglia. There are chains of successive neurons, first-roder neuron > second-order neuron > third-order neuorn. The order of the neuron changes when synapsing occurs.
• Types of sensory tracts (from sensory neurons to the brain)

  • Dorsal column-medial leminscal pathways: precise, straight-through transmission, proprioception. Needed for discriminative touch, vibrations and proprioception. Crosses over at the medulla oblongata. Terminates at the primary somatosensory cortex. Origin is mechanorecpotrs/proprioceptors.
  • Spinocerebellar pathways; proprioception (muscle and tendon stretch- where are body parts in space. to the cerebellum which regulates our posture and coordinates skeletal muscle movements. There is no crossover. Terminates at the cerebellum. Origin is proprioceptors
  • Spinothalamic pathways: pain, temperature, coarse touch and pressure. Cross over occurs at the spinal cord level of sensation Terminates at the thalamus, then the primary somatosensory cortex. Origin at nociceptors and thermoreceptors.
• Motor neurons


  Cell bodies in the ventral horns of the spinal cord.
• Types of Motor Tracts (from the brain to motor neurons)


  • Corticospinal tracts: direct from primary motor cortex to the spinal cord. Pyramidal tracts/direct pathways. Create direct pathways that bypass the thalamus. Controlling voluntary movements of skeletal muscles.
  • Lateral corticospinal tract crosses over at the medulla oblongata (distal limbs such as the legs, fingers and hands). Larger than ventral horn.
  • Ventral corticospinal tract crosses over at the spinal cord level of muscle (proximal muscles like trunk muscles). Terminates in the anterior horn of the spinal cord.
• Spinal Tract/Lesion-Injury


  • What function is lost? identify the specific function based on the affected spinal tract.
  • What body parts are affected? Everything below the lesion is affected. C1-C2 lesion= both upper and lower limbs affected, lower thoracic lesion: only lower limbs affected.
  • Which side is the symptom showing If the lesion is below the cross over (ipsilateral symptom), lesion is above cross-over= contralateral symptom.
• Brachial Plexus


  A network of nerves innervating upper limb muscles and skin.
• Injury to nerves

  Median Nerve injury: hand of benediction. Can’t bend the first three fingers.

  Radial Nerve Injury: Wristdrop. Effect all extensors, can’t extend.

  Ulnar nerve injury: claw hand. Test is for the person to hold a piece of paper between their two fingers.
• Axillary Nerve


  arises from the posterior cord, innervates teres minor and deltoid. Shoulder muscles
• Radial Nerve


  innvervates all the extensor muscles in the upper limb (both proximal arm and forearm). For example the triceps brachii.
• Musculocutaneous Nerve


  innervates biceps brachii, brachialis, coracobrachialis (proximal arm flexors). More medial
• Median Nerve


  does not innervate any muscles in the proximal arm, innervates majority of the forearm flexor muscles. Supplies a few of the intrinsic muscles of the hand (those that are not innervated by the ulnar)
• Ulnar Nerve


  does not innervate any muscles in the proximal arm, supplies two muscles in the forearm (flexor carpi ulnaris and half of the flexor digitorium produndus (on the ulnar half). Essentially innervates the intrinsic muscles of the hand.
• Nerve root to terminal nerves

  C5 and C6: Musculocutaneous and Median (superior, anterior, lateral)

  C7: Radial and Axillary (Middle, Posterior, Posterior)

  C8 and T1: Median and Ulnar (Inferior, Anterior, Medial)