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Neuroscience > Lab 4 - Internal Anatomy of the Spinal Cord and Peripheral Nerves > Flashcards

Lab 4 - Internal Anatomy of the Spinal Cord and Peripheral Nerves Flashcards

1
Q

what do axons from sensory and motor roots do before leaving/upon entering vertebral canal?

A

form a single mixed spinal nerve for each segment

-further fuse and intermingle to form nerve plexues and nerve branches, to form peripheral nerves

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2
Q

what is a dermatome?

A

sensory region of skin innervated by an individual nerve root

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3
Q

what is a myotome?

A

muscles that receive motor innervation from a given spinal nerve

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4
Q

what are the intercostal nerves? what do they innervate?

A

ventral rami of thoracic spinal nerves (except T1/2) that remain as individual entities
-innervate skin and muscles of thoracic and abdominal walls

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5
Q

what are somatic nerve plexi? where are they?

A

network of ventral rami of spinal nerves that come together and redistribute themselves w/ a different arrangement of peripheral nerves
-in all regions of the body except intercostal (thoracic spinal) nerves

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6
Q

what are the 4 somatic nerve plexi, where are they, and what do they innervate?

A
  1. cervical (C1-4) - neck
  2. brachial (C5-T1) - upper limb
  3. lumbar plexus (L1-L4) - lower abdominal wall of inguinal region, and anterior/medial compartments of thigh
  4. (lumbo)sacral (L4-S4) - gluteal region, posterior compartment of thigh, all of leg and foot
    - includes sciatic nerve as a branch

remember, they innervate both skin AND muscles

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7
Q

what is the largest nerve in the body and which plexus is it in?

A

sciatic nerve, in the (lumbo)sacral plexus

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8
Q

at what vertebral level does the trachea divide?

A

4th thoracic vertebrae

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9
Q

at what vertebral level is the umbilicus located?

A

3rd lumbar vertebrae

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10
Q

where does the adult spinal cord end and what are the consequences?

A

ends at the level of the 1st lumbar vertebrae

  • although the lumbar and sacral spinal roots exit at appropriate vertebral level, the spinal segments themselves are between 10-12th thoracic vertebrae
  • why injuries to lower lumbar vertebrae don’t cause direct spinal cord injury, although spinal roots from each segment pass thru vertebral canal prior to exiting, and may be damaged before exiting canal
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11
Q

what are the motor functions and regions of sensory loss for the radial nerve?

A

motor: extend arm, wrist (wrist drop), finger joints, supinate forearm, abduct thumb
sensory: posterior lateral arm, posterior strip on forearm, dorsal surface of thumb, lateral surface of hand, dorsum of first 3.5 digits

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12
Q

what are the motor functions and regions of sensory loss for the median nerve?

A

motor: flex and oppose thumb, flex digits 2/3, flex/abduct wrist (ape hand), pronate forearm
sensory: lateral palm, ventral thumb and digits 2/3, dorsal tip thumb and digits 2/3

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13
Q

what are the motor functions and regions of sensory loss for the ulnar nerve?

A

motor: adduct and abduct digits 2-5, flex digits 4/5 (claw hand), flex and adduct wrist
sensory: medial palm, all of the 5th digit and medial side of 4th digit

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14
Q

what are the motor functions and regions of sensory loss for the axillary nerve?

A

motor: abduct arm at shoulder beyond 15 degrees
sensory: spot on lateral arm over deltoid

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15
Q

what are the motor functions and regions of sensory loss for the musculocutaneous nerve?

A

motor: flex arm at elbow, supinate forearm
sensory: lateral forearm

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16
Q

what are the motor functions and regions of sensory loss for the femoral nerve?

A

motor: flex leg at hip, extend knee
sensory: portion of anterior thigh, knee, and medial leg

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17
Q

what are the motor functions and regions of sensory loss for the obturator nerve?

A

motor: adduct thigh
sensory: spot on medial thigh

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18
Q

what are the motor functions and regions of sensory loss for the sciatic nerve?

A

motor: flex knee, extend hip
sensory: lateral leg and most of foot

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19
Q

what are the motor functions and regions of sensory loss for the tibial nerve? what does it branch from?

A

motor: plantar (ventri) flex or invert foot, flex toes
sensory: bottom of foot and toes, lateral edge dorsum foot, and tips of toes 2-5

branches from sciatic nerve

20
Q

what are the motor functions and regions of sensory loss for the superficial fibular/peroneal nerve? what does it branch from?

A

motor: evert foot
sensory: dorso-lateral leg, most of dorsal foot

branches from sciatic nerve

21
Q

what are the motor functions and regions of sensory loss for the deep fibular/peroneal nerve? what does it branch from?

A

motor: dorsiflex foot, extend toes (dorsiflexion)
sensory: spot between big and 2nd toe

branches from sciatic nerve

22
Q

what are the 2 major branches of the sciatic nerve?

A

tibial and common fibular nerves

-common fibular later divides to superficial and deep fibular nerves

23
Q

what make up the hamstring muscles? what are they innervated by?

A

semitendinosus, semimembranosus, biceps femoris

-innervated by sciatic before it divides into tibial and common fibular

24
Q

what do peripheral mononeuropathies refer to?

A

injuries to individual peripheral nerve directly from plexus

-complete or incomplete (entrapment of nerve w/in muscle, compression w/in bony tunnel)

25
Q

what do plexopathies refer to?

A

plexus lesions that are more extensive than peripheral mononeuropathies, but restricted distribution of symptoms relating to innervation of components of plexus that are damaged

26
Q

what do radiculopathies refer to?

A

lesions to a spinal nerve, dorsal/ventral root
-associated with burning or tingling pain radiating down limb in dermatome of affected nerve root
-diminished sensation over dermatome served by root, and/or reduced strength in muscles; imprecise dermatomes due to overlap
-

27
Q

what are these examples of?

  • herniated intervertebral disc
  • motorcycle accident, or grabbing a limb while falling out of a tree
  • carpal or cubital tunnel syndromes
A
  • radiculopathy
  • plexopathy
  • peripheral mononeuropathy
28
Q

for which nerve roots are disc herniations most common?

A

radiculopathies most common for C6, C7, L5, and S1

-lumbosacral more common than cervical

29
Q

what is the straight-leg-raising test helpful for?

A

diagnosis of nerve root compression in lumbosacral region b/c causes traction of nerve roots
-if positive, there is typical radicular pain and sensory abnormalities

30
Q

what is the crossed straight-leg-raising test helpful for?

A

typical symptoms in the other limb if that limb is on the side of the radiculopathy

31
Q

what are the main weaknesses, decreased reflexes, and sensory loss for C5 nerve root?

A

MW: deltoid, infraspinatus, biceps
DR: biceps
SL: shoulder, upper lateral arm

32
Q

what are the main weaknesses, decreased reflexes, and sensory loss for C6 nerve root?

A

MW: wrist extensors, biceps
DR: biceps, brachioradialis
SL: lateral arm and forearm, skin of thumb and index finger

33
Q

what are the main weaknesses, decreased reflexes, and sensory loss for C7 nerve root?

A

MW: triceps
DR: triceps
SL:posterior arm and forearm, skin of index and middle fingers

34
Q

what are the main weaknesses, decreased reflexes, and sensory loss for L1-L2 nerve root?

A

MW: illiopsoas, psoas major, hip flexion
DR: none
SL: around hip (front and back)

35
Q

what are the main weaknesses, decreased reflexes, and sensory loss for L2-3 nerve root?

A

MW: adduction of thigh (waddling gait), knee extension
DR: patellar (knee jerk)
SL: around hip (front and back), anterior and medial thigh

36
Q

what are the main weaknesses, decreased reflexes, and sensory loss for L4 nerve root?

A

MW: tibialis anterior and posterior, foot inversion
DR: none
SL: medial leg, lateral and anterior thigh

37
Q

what are the main weaknesses, decreased reflexes, and sensory loss for L5 nerve root?

A

MW: foot dorsiflexion, hip abduction, heel walk (“Trendelenberg sign”)
DR: none
SL: dorsum and sole of foot, lateral leg

38
Q

what are the main weaknesses, decreased reflexes, and sensory loss for S1 nerve root?

A

MW: foot plantarflexion, tip-toe walk
DR: Achelles tendon (ankle jerk)
SL: lateral foot, small toe plantar surface, sole of foot

39
Q

what is the difference between gray and white matter?

A

gray: centrally located, where cell bodies (perikarya) located
white: peripherally located, where ascending/descending axons of brain/SC, and propriospinal axons which interconnect different segments of SC

40
Q

where do peripheral sensory axons enter cord from? what happens afterwards? where do large and small diameter axons enter from?

A

dorsal/posterior root

  • larger (more myelinated) enter medially w/in dorsal funiculus and carry epicritic info
  • -may ascend cord w/o synapse as dorsal columns, but some synapse onto neurons in dorsal horn
  • smaller (less myelinated) enter laterally from dorsal root carrying nociceptive and temperature (protopathic)
  • -may pass one or two spinal segments rostral/caudal to entry via Lissauer’s tract before synapsing onto dorsal horn neurons
41
Q

what are reflex arcs comprised of? what are 3 examples of reflexes?

A

simple, w/o info from brain

  • sensory muscle –> afferent axon –> interneuron –> efferent axon –> motor muscle
  • Babinski, knee jerk, and biceps jerk
42
Q

where do axons of motor neurons of each motor nucleus project?

A

via anterior/ventral root of one or more spinal nerves to innervate same muscle
-damage to individual nerve root may weaken, but not cause complete paralysis, b/c motor axons that innervate individual muscles may contribute to several adjacent spinal nerves

43
Q

what will damage to the individual nerve that innervates a muscle cause?

A

complete paralysis of muscle (and fasciculations and rapid atrophy)

44
Q

where is the amount of gray matter greatest?

A

greatest in regions that innervate limbs

-cervical/brachial (C5-T1) and lumbosacral (L3-S2) enlargements have large dorsal and venral horns

45
Q

what happens to the gray:white matter ratio as you ascend rostrally through SC?

A

white matter increases b/c tracts of ascending (sensory) axons get new incoming axons at more rostral levels, and descending axons are thicker b/c fewer axons have terminated than at lower levels

Neuroscience (39 decks)

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