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Exam 4 Flash Cards > Chapter 13 - Spinal Cord & Reflexes > Flashcards

Chapter 13 - Spinal Cord & Reflexes Flashcards

1
Q

4 Functions of the Spinal Cord

A
  • Conduction
  • Neural Integration
  • Locomotion
  • Reflexes
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2
Q

Conduction

A

nerve fibers send sensory and motor information ↑ and ↓ the spinal cord.

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3
Q

Neural integration

A

spinal neurons receive input from multiple sources, integrate (compute!) it, and execute appropriate output (e.g., bladder control)

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4
Q

Locomotion

A

spinal cord contains central pattern generators. Ex. groups of neurons that coordinate repetitive sequences of contractions for walking.

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5
Q

Reflexes

A

involuntary responses to stimuli that are vital to posture, coordination, and protection.

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6
Q

Spinal Cord

A

cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull.
– Occupies the upper 2/3 of vertebral canal
– Inferior margin of SC ends at the L1 vertebral bone or slightly beyond!!!!

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7
Q

The Spinal Cord

A
  • Cervical 8
  • Thoracic 12
  • Lumbar 5
  • Sacrum 5
    1 Coccygeal nerve
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8
Q

Why are there 8 cervical nerves, but only 7 cervical vertebrae (bones) ?

A

Cl nerve comes out between the skul and first vertebrae. Then there numbered after that

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9
Q

Why is there little risk of spinal cord damage with these procedures?

A

The spinal cord does not extend lower than L1/L2

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10
Q

Surface Anatomy

A

31 pairs of spinal nerves enter/exit between the vertebrae on both sides.

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11
Q

Cervical Enlargement

A
  • nerves to upper limb
  • takes care of the arm
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12
Q

Lumbar enlargement

A
  • nerves to pelvic region and lower limbs
  • for your legs, sensory and motor regions make this place larger
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13
Q

Medullary cone

A
  • cord tapers to a point inferior to lumbar enlargement
  • tip of spinal cord
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14
Q

Cauda equina

A
  • bundle of nerve roots that occupy the vertebral canal from L2 to S5
  • horse tail. bunch of nerves coming down from cone
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15
Q

Where are the Enlargements?

A

In the cervical & Lumbar regions
- skinner in thoracic because you have neuron that controls posture, core muscles.
- in very large motor unit groups

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16
Q

P.A.D.

A

-Pia mater
- Arachnoid mater
- Dura mater
- These same 3 fibrous membranes surround the spinal cord

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17
Q

Dural sheath

A

surrounds spinal cord and is separated from vertebrae by epidural space.

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18
Q

Arachnoid

A

membrane adheres to dura and is separated from pia by fibers spanning the subarachnoid space that is filled with cerebrospinal fluid (CSF)

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19
Q

Lumbar puncture

A

spinal tap) takes sample of CSF

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20
Q

Pia

A

delicate membrane that follows contours of spinal cord.

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21
Q

Safe place to do lumbar puncture

A

L3/L4 or L4/L5

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22
Q

Spina Bifida

A

congenital defect in which one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord.

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23
Q

Prevention of Spina Bifida

A

Folic acid (a B vitamin now added to flour), also in prenatal vitamins
– Note:
Defect occurs during the first 4 wks of devel., so folic acid supplements for mothers must begin 3 mo. before conception.

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24
Q

Gray Matter

A

neuron cell bodies with little myelin
– Site of information processing, synaptic integration

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25
Q

White matter

A

abundantly myelinated axons
– Carry signals from one part of the CNS to another

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26
Q

Gray Matter

A

Pair of posterior (dorsal) horns
– Posterior (dorsal) root of spinal nerve carries only sensory fibers (afferent)
Pair of thicker anterior (ventral) horns
– Anterior (ventral) root of spinal nerve carries only motor fibers (efferent)
* Gray commissure connects R & L sides
* Central canal lined with ependymal cells and filled with CSF

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27
Q

White Matter

A

Consists of myelinated axons that course up (ascending) and down (descending) the cord providing communication between different levels of the CNS.
* Columns (funiculi) —three pairs of these white matter bundles – Posterior (dorsal), lateral, and anterior (ventral) columns
– Tracts or fasciculi = subdivisions of each column

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28
Q

Spinal Tracts

A

Fibers in a given Tract have similar origin, destination and function.
– Ascending tracts—carry sensory information up
– Descending tracts—carry motor information down

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29
Q

Decussation

A

crossing of the midline that occurs in many tracts so that brain senses and controls contralateral side of body

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30
Q

Contralateral

A

when the origin and destination of a tract are on opposite sides of the body

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31
Q

Ipsilateral

A

when the origin and destination of a tract are on the same side of the body; does not decussate

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32
Q

Where are ascending and descending tracts found?

A

ventral horn

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33
Q

Sensory nerves

A

Carry signals from sensory receptors to the CNS

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34
Q

Motor nerves

A

Carry signals from CNS to muscles and glands

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35
Q

Mixed nerves

A

Consists of both afferent and efferent fibers

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36
Q

Both sensory and motor fibers can also be described as:

A
  • Somatic or visceral
    – General or special
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37
Q

Epineurium

A

dense irregular CT that wraps entire nerve

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38
Q

Perinerium

A

layers of overlapping squamous cells that wrap fascicles: bundles of nerve fibers

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39
Q

Endoneurium

A

loose CT external to neurilemma (mb of one axon)

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40
Q

Nerve

A

a cord-like organ composed of numerous nerve fibers (axons) bound together by CT.

41
Q

The nerve fibers of PNS are surrounded by what?

A

Schwann cells forming neurilemma and myelin sheath around the axon.

42
Q

Blood vessels penetrate CT coverings

A

Provide plentiful blood supply

43
Q

Ganglion

A
  • cluster of neurosomas (cell bodies) in the PNS
  • Enveloped in an endoneurium CT continuous with that of the nerve
  • Bundles of nerve fibers leading into, thru, & out of the ganglion.
  • Posterior (dorsal) root ganglion (DRG) associated with spinal nerves. Sensory!
44
Q

Which connective tissue wraps each nerve fiber

A

endoneurium

45
Q

3 Diseases of Motor Neurons

A
  • Destruction of motor neurons
  • Leads to skeletal muscle atrophy from lack of innervation.
46
Q

Poliomyelitis & Iron Lungs

A
  • spreads by fecal contamination of water
  • Destroys motor neurons in brainstem & ventral horn of SC
  • Symptoms: muscle pain, weakness, & loss of some reflexes
  • Then paralysis, muscular atrophy, & possibly respiratory arrest (diaphragm is skel muscle!)
47
Q

ALS

A
  • Destruction of motor neurons and muscular atrophy
    – Also sclerosis (scarring) of lateral regions of the spinal cord
    – Astrocytes fail to reabsorb the neurotransmitter glutamate from the tissue fluid
  • Accumulates to toxic levels
  • Early signs: muscular weakness; difficulty
    speaking, swallowing, and using hands
    – Sensory and intellectual functions remain unaffected
48
Q

Shingles

A
  • Disease of sensory nerves
  • caused by the virus traveling down the sensory nerves by fast axonal transport (anterograde) when immune system is compromised
  • Prevention: Vaccination
49
Q

Mixed spinal nerves

A

become roots which become rootlets before joining the spinal cord

50
Q

What are the two enlargements of the spinal cord

A

cervical and lumbar

51
Q

Anterior ramus

A
  • In thoracic region, it gives rise to intercostal nerve.
  • In other regions, anterior rami form plexuses.
52
Q

Posterior ramus

A

innervates the muscles and joints in that region
of the spine and the skin of the back

53
Q

Meningeal branch

A

reenters the vertebral canal and innervates the meninges, vertebrae, and spinal ligaments.

54
Q

Cervical plexus

A
  • in the neck, C1 to C5
  • Supplies neck and phrenic nerve to the diaphragm
55
Q

Brachial plexus

A
  • near the shoulder, C5 to T1
  • Supplies upper limb and some of shoulder and neck
  • Median nerve—carpal tunnel syndrome
56
Q

Lumbar plexus

A
  • in the lower back, L1 to L4
  • Supplies abdominal wall, anterior thigh, and genitalia
57
Q

Sacral plexus

A
  • in the pelvis, L4, L5, and S1 to S4
  • Supplies remainder of lower trunk and lower limb
58
Q

Coccygeal plexus

A
  • S4, S5, and Co1
59
Q

Phrenic nerve

A

keeps you alive
- controls the diaphragm, major muscle of respiration

60
Q

Median nerve

A

innervate the arm

61
Q

Femoral nerve

A

innervates the leg

62
Q

sciatic nerve

A

supplies remainder of lower trunk and lower limb

63
Q

Reflexes

A

lead to stimulation of glands or muscle

64
Q

Reflexes require stimulation

A

Not spontaneous actions, but responses to sensory input

65
Q

Reflexes are quick

A

Involve few, if any, interneurons and minimum synaptic delay

66
Q

Reflexes are involuntary

A

Occur without intent and are difficult to suppress

67
Q

Reflexes are stereotyped/automated

A

Occur essentially the same way every time

68
Q

Somatic receptors

A
  • In skin, muscles, or tendons
  • Skin - touch or nociception
  • Proprioceptors— in muscles or tendons, sense monitor body position and movement of body parts
    Ex. muscle spindle, GTO
69
Q

Afferent nerve fibers

A

Carry information from receptors to dorsal (posterior) horn of spinal cord or to the brainstem

70
Q

Intergrating center

A

One or more synapses in the CNS

71
Q

Efferent nerve fibers

A

Carry motor impulses to muscles

72
Q

Effectors

A

The muscles that carry out the response

73
Q

Somatic Reflexes

A

for skeletal muscle.

74
Q

Visceral reflexes

A

for skeletal muscles and cardiac muscles + glands

75
Q

Muscle spindle

A
  • stretch receptors embedded in skeletal muscles.
  • Enables brain to send motor commands back to the muscles that control coordinated movement, corrective reflexes, muscle tone, and posture.
76
Q

Speed of change

A

sense muscle length and body movement

77
Q

A spindle contains:

A

intrafusal muscle fibers within it
– Rest of the muscle’s fibers (those generating force for movement) are extrafusal fibers

78
Q

gamma motor neuron

A

innervates the ends of an
intrafusal fiber and keeps it taut

79
Q

The midportion of the intrafusal fiber contains

A
  • Primary afferent fibers– monitor fiber length and speed of length
    changes
  • Secondary afferent fibers – monitor length only
80
Q

Ex. of spindle function

A

help you to keep upright when standing on a boat

81
Q

Myotatic reflex

A

when a muscle is stretched, it “fights back” and contracts.

82
Q

Myotactic helps:

A
  • helps maintain equilibrium and posture
  • Head starts to tip forward as you fall asleep
  • Muscles contract to raise the head
83
Q

patellar reflex

A

monosynaptic reflex
- one synapse between the afferent and efferent neurons

84
Q

Reciprocal inhibition

A

reflex phenomenon that prevents
muscles from working against each other by inhibiting antagonist when agonist is excited (see next slide, what color is the inhibiting neuron?)

85
Q

Withdrawal reflex

A

triggers contraction of the flexors and relaxation of the extensors in that limb.

86
Q

Flexor reflex

A

the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus (nociceptor used)

87
Q

Polysynaptic reflex arc

A

pathway in which signals travel over many synapses on their way to the muscle.

88
Q

Crossed extension reflex

A

contraction of extensor muscles in limb opposite of the one that is withdrawn
- Maintains balance by extending other leg

89
Q

Intersegmental reflex

A

one in which the input and output occur at different levels (segments) of the spinal cord
– Pain in foot causes contraction of abdominal muscles

90
Q

Golgi Tendon Organs

A

proprioceptors in a tendon near its junction with a muscle
– Golgi tendon organ: 1 mm long, nerve fibers entwined in collagen fibers of the tendon

91
Q

Tendon reflex

A

in response to excessive tension on the tendon.
– Inhibits muscle from contracting strongly (recall the video about the climber).
– Moderates muscle contraction before it tears a tendon or pulls it loose from the muscle or bone.
Nerve fibers
Golgi Tendon Organ
Tendon bundles
Muscle fibers

92
Q

Complete transection

A

complete severance of cord

93
Q

Spinal shock

A

loss of sensory & motor function below injury

94
Q

Spinal cord trauma Above C4

A

poses threat of respiratory failure

95
Q

Hemiplegia

A

paralysis on one side of the body

96
Q

Paraplegia

A

Paralysis of both lower limbs

97
Q

Quadriplegia

A

paralysis of all four limbs

98
Q

Paresis

A

partial paralysis or weakness of the limbs

Exam 4 Flash Cards (4 decks)

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