Chapter 16 B, Sp 10


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Chapter 16 B, Sp 10

  1. 1. Cervical Plexuses <ul><li>C 1 -C 4 , some of C 5 . </li></ul><ul><li>Deep to sternocleidomastoid muscle. </li></ul><ul><li>Serves muscles and skin of neck and shoulder and some head. </li></ul><ul><li>Phrenic nerve serves diaphragm , chief muscle for breathing. </li></ul><ul><ul><li>Irritation can give hiccups </li></ul></ul><ul><ul><li>Damage to the spinal cord above origin of phrenic nerves leads to respiratory arrest (“C 3 , C 4 , C 5 keep the diaphragm alive”). </li></ul></ul>16-
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  3. 3. Brachial Plexuses <ul><li>C5-T1 mainly </li></ul><ul><li>Serves shoulder, some thorax muscles, and upper limb </li></ul><ul><li>Roots (really rami) -> trunks -> divisions -> cords-> major nerves (Real tired, drink coffee black) </li></ul><ul><li>Injuries are common - often from stretching </li></ul>16-
  4. 4. Brachial Plexus: Major Nerves <ul><li>Axillary nerve </li></ul><ul><ul><li>Deltoid and teres minor </li></ul></ul><ul><ul><li>Sensory to superolateral arm </li></ul></ul><ul><ul><li>Damage: difficulty with abduction and anesthesia along the superolateral skin of the arm. </li></ul></ul><ul><li>Musculocutaneous nerve </li></ul><ul><ul><li>Elbow flexors </li></ul></ul><ul><ul><li>Sensory to lateral forearm </li></ul></ul><ul><li>Radial nerve </li></ul><ul><ul><li>Extensors </li></ul></ul><ul><ul><li>Posterior skin </li></ul></ul><ul><ul><li>Damage: wrist-drop </li></ul></ul>16-
  5. 5. Brachial Plexus: Major Nerves <ul><li>Median nerve </li></ul><ul><ul><li>Wrist and hand flexors </li></ul></ul><ul><ul><li>Sensory to hand </li></ul></ul><ul><ul><li>Damage: wrist slashing, carpal tunnel </li></ul></ul><ul><ul><ul><li>Characteristic “ape hand” deformity </li></ul></ul></ul><ul><li>Ulnar nerve </li></ul><ul><ul><li>Wrist and hand flexors </li></ul></ul><ul><ul><li>Sensory to hand </li></ul></ul><ul><ul><li>Damage: “funny bone”, clawhand </li></ul></ul>16-
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  9. 9. Brachial Plexus Injuries <ul><li>Fairly common esp. for persons 18-22 </li></ul><ul><li>Axillary nerve injury </li></ul><ul><li>Radial nerve injury </li></ul><ul><li>Posterior cord injury: crutch palsy and drunkard’s paralysis </li></ul><ul><li>Median nerve injury </li></ul><ul><li>Ulnar nerve injury </li></ul><ul><li>Superior trunk injury affects C5 and C6 anterior rami </li></ul><ul><li>Inferior trunk injury from excessive abduction. Involves the C8 and T1 anterior rami. </li></ul>16-
  10. 10. Lumbar Plexuses <ul><li>L1-L4, within the psoas major muscle </li></ul><ul><li>Motor supply to anterior and medial thigh muscles and cutaneous supply to anterior thigh and part of leg and muscles and skin of anteriolateral abdominal wall, genitals </li></ul>16-
  11. 11. Lumbar Plexuses <ul><li>Chief nerves </li></ul><ul><ul><li>Femoral </li></ul></ul><ul><ul><ul><li>Thigh flexors and leg extensors (anterior compartment of thigh, quadriceps) </li></ul></ul></ul><ul><ul><ul><li>Stab or gunshot would -> inability to extend leg and loss of sensation over anteriomedial thigh </li></ul></ul></ul><ul><ul><li>Obturator </li></ul></ul><ul><ul><ul><li>Adductor muscles (medial compartment) </li></ul></ul></ul><ul><ul><ul><li>Childbirth -> paralysis of adductor muscles and loss of sensation of medial thigh </li></ul></ul></ul>16-
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  15. 15. Sacral Plexuses <ul><li>L4-S4 </li></ul><ul><li>Posterior muscles, buttocks, pelvis, and skin of lower limb </li></ul><ul><li>Principal nerve: sciatic nerve </li></ul><ul><ul><li>Thickest and longest </li></ul></ul><ul><ul><li>Tibial and common peroneal usually split near the knee </li></ul></ul><ul><ul><li>Damage: footdrop (fibular nerve damage), sciatica (usually from herniated disc, also from dislocated hip, osteoarthritis of spine, PG, gluteal injection) </li></ul></ul>16-
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  20. 20. Reflexes <ul><li>Rapid, automatic, involuntary reactions of muscles or glands to a stimulus. </li></ul><ul><li>All reflexes have similar properties. </li></ul><ul><ul><li>a stimulus is required to initiate a response to sensory input </li></ul></ul><ul><ul><li>a rapid response requires that few neurons be involved and synaptic delay be minimal </li></ul></ul><ul><ul><li>an automatic response occurs the same way every time </li></ul></ul><ul><li>Awareness of the stimulus occurs after the reflex action has been completed, in time to correct or avoid a potentially dangerous situation. </li></ul><ul><li>Spinal vs. cranial reflexes </li></ul><ul><li>Somatic vs. autonomic reflexes </li></ul>16-
  21. 21. Components of a Reflex Arc <ul><li>The neural “wiring” of a single reflex. </li></ul><ul><li>Always begins at a receptor in the PNS. </li></ul><ul><li>Communicates with the CNS. </li></ul><ul><li>Ends at a peripheral effector (muscle or gland) cell. </li></ul>16-
  22. 22. Ipsilateral and Contralateral Reflex Arcs <ul><li>Ipsilateral is when both the receptor and effector organs of the reflex are on the same side of the spinal cord. </li></ul><ul><ul><li>for example, an ipsilateral effect occurs when the muscles in your left arm contract to pull your left hand away from a hot object </li></ul></ul><ul><li>Contralateral is when the sensory impulses from a receptor organ cross over through the spinal cord to activate effector organs in the opposite limb. </li></ul><ul><ul><li>for example, contralateral effect occurs when you step on a sharp object with your left foot and then contract the muscles in your right leg to maintain balance as you withdraw your left leg from the damaging object </li></ul></ul>16-
  23. 23. Monosynaptic Reflexes <ul><li>The simplest of all reflexes. </li></ul><ul><li>Interneurons are not involved in this reflex. </li></ul><ul><li>The patellar (knee-jerk) reflex is a monosynaptic reflex that physicians use to assess the functioning of the spinal cord. </li></ul><ul><li>By tapping the patellar ligament with a reflex hammer, the muscle spindles in the quadriceps muscles are stretched. </li></ul><ul><li>Produces a noticeable kick of the leg. </li></ul>16-
  24. 24. Polysynaptic Reflexes <ul><li>Have more complex neural pathways that exhibit a number of synapses involving interneurons within the reflex arc. </li></ul><ul><li>Because this reflex arc has more components, there is a more prolonged delay between stimulus and response. </li></ul>16-
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  27. 27. Examples of Spinal Reflexes 16-
  28. 28. Withdrawal (Flexor) Reflex <ul><li>Polysynaptic reflex initiated by a painful stimulus </li></ul>16-
  29. 29. Stretch Reflexes <ul><li>Monosynaptic reflex that monitors and regulates skeletal muscle length . </li></ul><ul><li>When a stimulus results in the stretching of a muscle, that muscle reflexively contracts. </li></ul><ul><li>The patellar (knee-jerk) reflex is an example of a stretch reflex. </li></ul><ul><li>The stimulus (the tap on the patellar tendon) initiates contraction of the quadriceps femoris muscle and extension of the knee joint. </li></ul>16-
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  31. 31. Golgi Tendon Reflex <ul><li>Prevents skeletal muscles from tensing excessively . </li></ul><ul><li>Golgi tendon organs are nerve endings located within tendons near a muscle–tendon junction. </li></ul><ul><ul><li>activation of the Golgi tendon organ signal interneurons in the spinal cord, which in turn inhibit the actions of the motor neurons </li></ul></ul><ul><li>The associated muscle is allowed to relax, thus protecting the muscle and tendon from excessive tension damage. </li></ul>16-
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  33. 33. Reflex Testing in a Clinical Setting <ul><li>Reflexes can be used to test specific muscle groups and specific spinal nerves or segments of the spinal cord. </li></ul><ul><li>Consistently abnormal reflex response may indicate damage to the nervous system or muscles. </li></ul><ul><li>A reflex response may be normal, hypoactive, or hyperactive. </li></ul>16-
  34. 34. Spinal Cord Injury <ul><li>Many causes: tumors, herniated discs, clots, trauma </li></ul><ul><li>Possible consequences </li></ul><ul><ul><li>Paralysis: total loss of voluntary motor functions from nerve or muscle damage </li></ul></ul><ul><ul><ul><li>Monoplegia: one limb </li></ul></ul></ul><ul><ul><ul><li>Diplegia: upper or lower limbs </li></ul></ul></ul><ul><ul><ul><li>Paraplegia: lower limbs </li></ul></ul></ul><ul><ul><ul><li>Hemiplegia: one side </li></ul></ul></ul><ul><ul><ul><li>Quadriplegia: upper and lower limbs </li></ul></ul></ul>16-
  35. 35. Spinal Cord Injury <ul><li>Following transection, spinal shock , that lasts a few days to a few weeks </li></ul><ul><ul><li>Areflexia temporarily below the lesion </li></ul></ul><ul><ul><ul><li>Usually, lasts a few hours </li></ul></ul></ul><ul><ul><ul><li>If 48 hours or longer, then permanent paralysis usually </li></ul></ul></ul><ul><ul><li>Anti-inflammatory drug, methylprednisolone, may help if given within 8 hours </li></ul></ul>16-
  36. 36. Spinal Cord Injury <ul><li>Complete transection </li></ul><ul><ul><li>All tracts cut -> lose all sensation and voluntary movement below cut (paraplegia or quadriplegia, spastic paralysis) </li></ul></ul><ul><li>Hemisection </li></ul><ul><ul><li>Partial transection -> partial loss below transection </li></ul></ul><ul><ul><li>Posterior column-medial lemniscus pathway: loss on same side </li></ul></ul><ul><ul><li>Lateral corticospinal tracts: loss on same side </li></ul></ul><ul><ul><li>Anterior corticospinal tracts: loss on opposite side </li></ul></ul><ul><ul><li>Spinothalamic tracts: loss on opposite side </li></ul></ul>16-
  37. 37. Poliomyelitis (Polio) <ul><li>Most serious form is Bulbar -> paralysis from destruction of cell bodies of motor neurons in anterior horn and nuclei of cranial nerves in medulla </li></ul><ul><li>Death may occur from respiratory arrest or heart failure if virus invades vital medullary centers </li></ul><ul><li>Salk and Sabin vaccine eradicated it </li></ul>16-
  38. 38. Spinal Cord Development <ul><li>The central nervous system forms from the embryonic neural tube. </li></ul><ul><li>Cranial and spinal nerves form from neural crest cells that have split off from the developing neural tube. </li></ul><ul><li>The cranial (superior) part of the neural tube expands and develops into the brain. </li></ul><ul><li>The caudal (inferior) part of the neural tube forms the spinal cord. </li></ul>16-