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BIOL 223 Lecture > CH 12 - Spinal Cord and Spinal Reflexes > Flashcards

CH 12 - Spinal Cord and Spinal Reflexes Flashcards

1
Q

Describe the spinal cord physically.

A

18” long, 0.5” wide, ends at L2 vertebra, bilaterally symmetrical, located in vertebral foramen

Two-way conduction pathway to/from brain

Stops growing at age 4-5

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2
Q

Posterior (dorsal) median sulcus

A

Groove on the posterior/dorsal side of the spinal cord

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3
Q

Anterior (ventral) median fissure

A

Deeper groove on the anterior/ventral side of the spinal cord

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4
Q

What are spinal cord enlargements caused by?

A

The amount of grey matter in the segment

Involvement with sensory/motor nerves of limbs

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5
Q

Innervate

A

To supply or control

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6
Q

Cervical enlargement

A

Spinal nerves that innervate the shoulder and upper limbs

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7
Q

Lumbar enlargement

A

Spinal nerves that innervate the pelvis and lower limbs

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8
Q

Conus medularis

A

The thin, conical spinal cord below the lumbar enlargement

Where the spinal cord ends

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9
Q

Filum terminale

A

The thin thread of fibrous tissue inferior to the conus medularis that anchors the spinal cord to the coccyx

Fusion of the spinal meninges beyond sacral vertebra S2

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10
Q

Cauda equina

A

The long dorsal/ventral roots that extend below the conus medularis/filum terminale

“The horse’s tail”

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11
Q

How many spinal cord segments are there?

How many nerves in each?

A

31 segments, each with 2 nerves

*Each segment is the same length, but the position changes with age

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12
Q

How are cervical spinal nerves named?

A

Named for their inferior vertebra

*First nerve is above C1 vertebra, and eighth nerve is below C7

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13
Q

How are all spinal nerves besides cervical named?

A

Named for their superior vertebra

*First nerve is below T1 vertebra

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14
Q

Where do the C01, S5, and the filum terminale nerves enter/leave the spinal column?

A

Inside the sacral hiatus

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15
Q

What makes up a spinal nerve?

A

Dorsal and ventral roots join to form a spinal nerve (on each side of the spine)

Contains mixed nerves (sensory and motor axons)

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16
Q

What kind of axons do ventral roots contain?

A

Axons of motor neurons (motor output)

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17
Q

Where do ventral roots carry information?

A

Away from the spinal cord to effectors

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18
Q

What kind of axons do dorsal roots contain?

A

Axons of sensory neurons (sensory input)

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19
Q

Where do dorsal roots carry information?

A

Into the spinal cord from sensory receptors

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20
Q

What does a dorsal root ganglion contain?

A

Cell bodies of sensory neurons

*Unipolar neurons

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21
Q

What are spinal meninges?

Name them.

A

Specialized membranes that isolate the spinal cord from its surroundings

Dura mater, arachnoid mater, pia mater

*Continuous with cranial meninges

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22
Q

What are the functions of spinal meninges?

A

Protect the spinal cord and provide blood supply

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23
Q

Meningitis

A

A viral or bacterial infection of the meninges

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24
Q

List the layers from a vertebra to the spinal cord.

A 
Bone
Periosteum
Epidural space 
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
Pia Mater
Spinal cord
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25
Q

How does the dura mater of the spinal cord differ from that of the brain?

A

The spinal dura mater has only one layer, whereas the cranial dura mater has two layers

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26
Q

Describe the superior, inferior, and lateral aspects of the spinal dura mater.

A

Superiorly continuous with cranial dura mater

Inferiorly tapers into filum terminale in the coccygeal ligament

Laterally fuses with the epineurium of the spinal cord

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27
Q

What is found within the epidural space of the spinal cord?

A

Adipose tissue & blood vessels

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28
Q

Epidural

A

A procedure that injects a local anesthetic into the epidural space

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29
Q

Lumbar puncture (spinal tap)

A

A procedure in which a needle is inserted into the subarachnoid space between vertebrae L4 and L5 to withdraw CSF

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30
Q

What is the pia mater of the spinal cord made of?

A

Collagen and elastic fibers

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31
Q

What are denticulate ligaments and where are they found?

A

Ligaments that anchor the spinal cord along its length at each side to stabilize side-to-side movements

Fused from the pia mater to the dura mater

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32
Q

Where are the blood vessels of the spinal cord located?

A

Along the surface of the pia mater within the subarachnoid space

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33
Q

What type of nuclei are found in posterior grey horns?

A

Somatic and visceral sensory nuclei

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34
Q

What type of nuclei are found in lateral grey horns?

Describe them.

A

Visceral motor nuclei

*Two neurons- a myelinated preganglionic neuron and an unmyelinated postganglionic neuron

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35
Q

Which segments of the spinal cord have lateral grey horns?

A

Thoracic and lumbar segments T1-L2

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36
Q

What type of nuclei are found in anterior grey horns?

A

Somatic motor nuclei

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37
Q

What do commissures (transverse tracts) contain?

A

Commissural fibers that cross from one side of the spinal cord to the other

*Needed for contralateral control

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38
Q

Name the three connective tissue layers that surround spinal nerves.

A

Epineurium, perineurium, endoneurium

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39
Q

Describe the epineurium.

A

The outermost layer, continuous with the dura mater

Made of dense collagenous CT

40
Q

Describe the perineurium.

A

The middle layer that divides nerves into fascicles (bundles of axons)

41
Q

Describe the endoneurium.

A

The inner layer that surrounds individual axons

42
Q

Name the layers surrounding a myelinated axon from innermost to outermost.

A

Axon
Myelin sheath
Neurolemma
Endoneurium

43
Q

Peripheral nerves

A

The terminal end of branched spinal nerves that form pathways to innervate organs and tissues

Surrounded by the same CT sheaths as the spinal nerves

44
Q

What are rami communicantes?

Name them.

A

“communicating branches”

White ramus communicans & grey ramus communicans

45
Q

Which spinal cord segments contain white rami communicans?

A

Spinal cord segments T1-L2

46
Q

Describe the size of the dorsal (posterior) ramus.

What does it innervate?

A

Smaller branch

Innervates the posterior region of the body

47
Q

Describe the size of the ventral (anterior) ramus.

What does it innervate?

A

Larger branch

Innervates the anterior/lateral regions of the body

48
Q

Describe the meningeal branch’s location and function.

A

A small branch off of the dorsal ramus that re-enters the vertebral cavity though the intervertebral foramen

Supplies nerve function to the vertebrae, vertebral ligaments, spinal cord blood vessels, spinal meninges

49
Q

Spinal nerve plexuses

A

Complex networks of nerve fibers formed from the ventral rami of spinal nerves

50
Q

What makes up the cervical plexus?

A

Ventral rami of spinal nerves C1-C5

51
Q

What structures does the cervical plexus innervate?

A

Skin and skeletal muscles of the head, neck, shoulders, chest, and diaphragm

52
Q

Which major peripheral nerve (terminal branch) belongs to the cervical plexus?
What does it control?

A

Phrenic nerve

Controls muscles of the diaphragm

53
Q

What makes up the brachial plexus?

A

Ventral rami of spinal nerves C5-T1

54
Q

What are the 5 major groups of the brachial plexus?

A 
Ventral rami (roots)
Trunks
Divisions
Cords
Peripheral nerves (terminal branches)
55
Q

What structures does the brachial plexus innervate?

A

Skin and skeletal muscles of the pectoral girdle and upper limbs

56
Q

Which major peripheral nerves (terminal branches) belong to the brachial plexus?

A 
Musculocutaneous nerve
Axillary nerve
Median nerve
Radial nerve
Ulnar nerve
57
Q

What makes up the lumbar plexus?

A

Ventral rami of spinal nerves T12-L4

58
Q

What structures does the lumbar plexus innervate?

A

Anterolateral abdominal wall, external genitalia, and parts of the lower limbs

59
Q

Which major peripheral nerves (terminal branches) belong to the lumbar plexus?

A

Genitofemoral nerve
Lateral femoral cutaneous nerve
Femoral nerve
Obturator nerve

60
Q

What makes up the sacral plexus?

A

Ventral rami of spinal nerves L4-S4

61
Q

What structures does the sacral plexus innervate?

A

Buttocks, perineum, and lower limbs

62
Q

Which major peripheral nerves (terminal branches) belong to the sacral plexus?

A

Sciatic nerve (which branches into the tibial nerve and common fibular nerve) and the pudendal nerve

63
Q

Which spinal nerves make up the intercostal (thoracic) nerves?

A

Spinal nerves T2-T12

These do not form branches

64
Q

Describe the ventral (anterior) rami of the intercostal (thoracic) nerves.

A

Spinal nerves T2-T12 do not form plexuses

Instead the nerves directly innervate the intercostal muscles and the anterior/lateral skin of the thorax (between neck and abdomen)

65
Q

Describe the dorsal (posterior) rami of the intercostal (thoracic) nerves.

A

Spinal nerves T2-T12 innervate the deep muscles of the back and posterior skin of the thorax (between neck and abdomen)

66
Q

Describe the ventral ramus of the T12 spinal nerve.

A

The ventral ramus splits, with one part forming the intercostal nerve and the other forming part of the lumbar plexus

67
Q

Peripheral neuropathy

A

Damage to the spinal nerves due to compression, trauma, or diabetes

Results in the loss of sensation/motor function in the associated body region

68
Q

Dermatome

A

An area of skin supplied by peripheral nerve fibers originating from a single dorsal root ganglion

Loss of sensation in a dermatome can indicate the level of spinal cord damage

69
Q

Hypoesthesia

A

Partial loss of sensation in a dermatome caused by a severed dorsal root

70
Q

Dermatomal anesthesia

A

Complete loss of sensation caused by damage to at least three overlapping dermatomes

71
Q

Why does spinal nerve C1 not have a dermatome?

A

It is the only spinal nerve that does not contain a dorsal root

72
Q

Shingles

A

A disease caused by Varicella-Zoster Virus (VZV) that remains dormant within the dorsal root ganglia

A type of herpes virus that attacks sensory neurons in the dorsal root of spinal nerves, and sensory ganglia of cranial nerves

Skin eruptions follow the distribution of the dermatomal innervation

73
Q

Reflex

A

A rapid, involuntary, automatic response to a stimulus

74
Q

Which effectors do somatic reflexes travel to?

A

Skeletal muscle

75
Q

Which effectors do visceral (autonomic) reflexes travel to?

A

Smooth/cardiac muscle or glands

76
Q

Reflex arc

A

The wiring of a single reflex that begins at a sensory receptor and ends at an effector (with some using interneurons)

Generally opposes the original stimulus (negative feedback)

77
Q

List and describe the 5 steps involved in a reflex arc.

A

Step 1: stimulus & activation of sensory receptors
-physical or chemical changes; graded potential

Step 2: activation of sensory (unipolar) neurons
-AP at trigger zone of sensory neuron

Step 3: integration at CNS
-sensory neuron synapses with interneuron

Step 4: activation of motor neurons
-interneurons synapse with motor neurons

Step 5: effector response
-motor neuron synapses with effector

78
Q

What are the 4 main classes of reflexes?

Describe their subtypes.

A

Developmental

  • Innate (genetic)
  • Acquired (learned)

Response

  • Somatic (skeletal muscle)
  • Visceral/autonomic (smooth/cardiac muscle, glands)

Complexity of circuit

  • Monosynaptic (one synapse, no interneurons)
  • Polysynaptic (multiple synapses, interneurons, EPSP/IPSP)

Processing site

  • Spinal reflexes (spinal cord)
  • Cranial reflexes (brain)
79
Q

Muscle spindles

A

Proprioceptors involved in the stretch reflex that primarily detect changes in the length of skeletal muscle

Contribute to fine motor control and provide body position information to CNS

80
Q

What are intrafusal muscle fibers?

What are they innervated by?

A

Small bundles of specialized skeletal muscle fibers surrounded by dendrites of sensory neurons

Forms muscle spindle

Innervated by somatic sensory/motor neurons (gamma motor neurons)

81
Q

What are extrafusal muscle fibers?

What are they innervated by?

A

Contracting muscle fibers that surround intrafusal muscle fibers

Innervated by somatic motor neurons (alpha motor neurons)

82
Q

Golgi tendon organs

A

Proprioceptors involved in the tendon reflex

Location- within tendons
Neuron- dendrites of somatic sensory neuron
Function- monitor tendon stretching

83
Q

Name examples of monosynaptic reflexes.

A

Stretch reflex: patellar reflex & postural reflex

84
Q

Name examples of polysynaptic reflexes.

A

Tendon reflex, withdrawal reflex, crossed extensor reflex

85
Q

Reciprocal inhibition (reciprocal innervation)

A

A polysynaptic reflex that prevents conflict between opposing muscles by utilizing EPSP/IPSP’s

Allows agonist to contract and antagonist to relax

86
Q

Does an AP frequency increase or decrease during stretching of the patellar reflex? Why?

A

The AP frequency increases

The rubber hammer tap stretches the patellar tendon, causing the muscle spindles to stretch as well

87
Q

Does an AP frequency increase or decrease during contraction of the patellar reflex? Why?

A

The AP frequency decreases

If this were not the case, our knee would stay contracted/extended

88
Q

Describe postural reflexes.

A

Stretched muscle responds by contracting automatically to maintain normal upright posture and balance

Many stretch reflexes are postural reflexes

89
Q

Describe the stretch reflex.

A

Stimulus: stretching of muscle and muscle spindle

Stretch reflex: contraction of agonist

Reciprocal inhibition: relaxation of antagonist

90
Q

Describe the tendon reflex.

A

Stimulus: intense/excessive contraction of agonist

Tendon reflex: relaxation of agonist

Reciprocal inhibition: contraction of antagonist

91
Q

Describe the withdrawal (flexor) reflex.

A

Stimulus: pain/pressure on a limb

Withdrawal (flexor) reflex: contraction of agonist (flexors)

Reciprocal inhibition: relaxation of antagonist (extensors)

92
Q

Describe the crossed extensor reflex.

A

Stimulus: balance or defense

Crossed extensor reflex: contraction of agonist (extensors)

Reciprocal inhibition: relaxation of antagonist (flexors)

*Reflex occurs on opposite body side as stimulus, and occurs simultaneously with the withdrawal reflex

93
Q

Ipsilateral reflexes

A

Reflexes that occur on the same side of the body that received the stimulus

*Stretch, tendon, and withdrawal reflexes

94
Q

Contralateral reflexes

A

Reflexes that occur on the opposite side of the body to where the stimulus was received

*Crossed extensor reflex

95
Q

Superficial reflexes

A

Reflexes elicited by cutaneous stimulation

  • Dependent on functional upper motor pathways and spinal reflex arcs
  • Plantar (Babinski) reflex
96
Q

What does the plantar (Babinski) reflex test for?

A

Tests integrity of spinal cord L4-S2

Determines if the primary motor cortex & corticospinal tracts are functioning properly

*Normal result is negative (no fanned toes)

BIOL 223 Lecture (26 decks)

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