A&p I - Exam 4 (Spinal Cord)

Front 1

What does the spinal cord occupy?

Back 1

Spinal canal of the vertebral column

Front 2

Where does the spinal cord begin and terminate?

Back 2

Foramen magnum and conus medullaris

Front 3

At what level of vertrebrae is the conus medullaris?

Back 3

L1-L2

Front 4

How many spinal cord segments are there?

Back 4

31

Front 5

How are the spinal nerves connected to the cord?

Back 5

Via the posterior (dorsal) and anterior (ventral) roots

Front 6

Posterior (dorsal) Root

Back 6

Area where sensory (afferent) information enters the cord

Front 7

Ventral (anterior) Root

Back 7

Area that motor (efferent) activity leaves the cord

Front 8

Gray matter

Back 8

The H- or butterfly-shaped central region of the spinal cord

Front 9

What does gray matter contain?

Back 9

Nerve cell bodies

Front 10

Where are the lateral horns (in gray matter) found?

Back 10

segments T1-T12 and L1-L2

Front 11

Each segment of the cord has several million neurons in the gray matter including?

Back 11

Sensory relay neurons,
Anterior motor neurons, and
Interneurons

Front 12

Where are anterior motor neurons located?

Back 12

Anterior (ventral) horns of the gray matter

Front 13

When axons leave the cord via the anterior (ventral) roots, what do they innervate?

Back 13

Skeletal muscle fibers

Front 14

What are the two types of motor neurons?

Back 14

Alpha motor neurons &
Gamma motor neurons

Front 15

What gives rise to Large A-alpha nerve axons?

Back 15

Alpha motor neurons

Front 16

What do Large A-alpha nerve axons innervate?

Back 16

Extrafusal skeletal muscle fibers

Front 17

How much of the total motor neuron pool do alpha motor neurons make up?

Back 17

2/3

Front 18

What do gamma motor neurons give rise to?

Back 18

A-gamma axons

Front 19

What do A-gamma axons innervate?

Back 19

Intrafusal muscle fibers in muscle spindles

Front 20

What makes up about 1/3 of total motorneurons in the anterior horns?

Back 20

Gamma motor neurons

Front 21

Are gamma motor neurons smaller or larger than alpha motor neurons?

Back 21

Smaller

Front 22

Where does most of the input to the motor neurons come from?

Back 22

Interneurons

Front 23

Where are interneurons found?

Back 23

All areas of the gray matter

Front 24

What are the most numerous cells in gray matter?

Back 24

Interneurons
- 30x more than alpha motor neurons

Front 25

Are interneurons in the gray matter inhibitory or excitatory?

Back 25

Both

Front 26

Where is most motor activity descending from the brain directed to first?

Back 26

Interneurons

Front 27

Why is white matter white?

Back 27

Myelination

Front 28

What does white matter contain?

Back 28

Numerous bundles (tracts)

Front 29

What are examples of ascending tracts in white matter?

Back 29

Lateral spinothalamic &
Posterior spinothalamic tracts
-project to thalamus

Front 30

What are lateral spinothalamic tracts for?

Back 30

Principal pathway for pain and temperature transmission

Front 31

What is the prinicipal pathway for transmission of tactile and proprioceptive sensations?

Back 31

Posterior spinothalamic tracts (dorsal columns)

Front 32

Descending tracts

Back 32

Originate in the brain and travel down the cord

Front 33

Corticospinal (pyramidal) tracts

Back 33

Motor nerve tract that originates in the motor cortex and terminates primarily on interneurons in the spinal cord gray matter

Front 34

Where do nerve tracts associated with the sympathetic nervous system originate and terminate?

Back 34

Originate in the brainstem and terminate in spinal segments T1-T12 and L1-L2

Front 35

What are the three layers of connective tissue that surround the spinal cord?

Back 35

- Pia mater
- Arachnoid mater
- Dura mater

Front 36

How far do the dura and arachnoid extend?

Back 36

Level S2

Front 37

What does the subarachnoid space contain?

Back 37

CSF

Front 38

What does the epidural space contain?

Back 38

- Fat
- Connective tissue
- Venous plexuses

Front 39

Where does the epidural space extend from and go to?

Back 39

Foramen magnum to the sacral hiatus

Front 40

Ligaments

Back 40

- Ligamentum flavum
- Interspinous ligament
- Supraspinous ligament

Front 41

Where does the ligamentum flavum lie?

Back 41

Just posterior to the epidural space

Front 42

What supplies blood to the spinal cord?

Back 42

Vertebral arteries and thoracic and abdominal aorta

Front 43

What is the single midline vessel that supplies the anterior 2/3 of the cord?

Back 43

Anterior spinal artery
- originates from the vertebral arteries

Front 44

What paired vessels supply the posterior 1/3 of the cord?

Back 44

Posterior spinal arteries
- arise from the posterior cerebellar arteries

Front 45

Where does the anterior spinal artery originate?

Back 45

Vertebral arteries at base of skull

Front 46

Where do the posterior spinal arteries originate from?

Back 46

Posterior cerebellar arteries

Front 47

What supplies BOTH the anterior and posterior spinal arteries?

Back 47

Radicular arteries

Front 48

What is the single branch of the aorta that almost always arises on the left side?

Back 48

Artery of Adamkiewicz

Front 49

Where is the artery of adamkiewicz in 15% of individuals?

Back 49

T5-T8

Front 50

Where is the origin of the artery of adamkiewicz in 60% of individuals?

Back 50

T9-T12

Front 51

Where is the artery of adamkiewicz in 25% of individuals?

Back 51

L1-L2

Front 52

What does the artery of adamkiewicz supply?

Back 52

Nearly all the blood flow to the lower thoracic and lumbar cord

Front 53

What may result from injury to the artery of adamkiewicz?

Back 53

Spinal cord ischemia

Front 54

What can result from spinal cord ischemia?

Back 54

Paraplegia

Front 55

Give examples of how spinal cord ischemia can happen?

Back 55

Surgical dissection or aortic cross-clamping

Front 56

Spinal nerves

Back 56

Formed by the joining of the anterior and posterior roots at each spinal cord segment

Front 57

Where do spinal nerves exit the vertebral column?

Back 57

Intervertebral foramina, between the vertebrae

Front 58

How many pairs of spinal nerves are there?

Back 58

31

Front 59

How many cervical spinal nerves?

Back 59

8

Front 60

How many thoracic spinal nerves?

Back 60

12

Front 61

How many lumbar spinal nerves?

Back 61

5

Front 62

How many sacral spinal nerves?

Back 62

5

Front 63

How many coccygeal spinal nerves?

Back 63

1

Front 64

Where do the lower lumbar and sacral nerves descend before they exit the vertebral column?

Back 64

Cauda equina

Front 65

Why are spinal nerves called mixed nerves?

Back 65

They contain somatic (sensory and motor) and autonomic nerve fibers

Front 66

What does each spinal segment supply?

Back 66

A specific region of skin (dermatome) and skeletal muscle

Front 67

What are the two major branches of spinal nerves?

Back 67

Anterior and posterior ramus

Front 68

What supplies long muscles of the back and tissue overlying them?

Back 68

Posterior primary division (posterior ramus)

Front 69

What is the main portion of the spinal nerve called?

Back 69

Anterior primary division (anterior ramus)

Front 70

Plexus

Back 70

An intermingling collection of nerves that emanate from different cord segments

Front 71

What joins to form the cervical plexus in the neck?

Back 71

Anterior rami of spinal nerves C1-C4

Front 72

What do peripheral nerves emerging from the cervical plexus supply?

Back 72

Skin and muscles of the neck and posterior scalp

Front 73

What emerges to innervate the diaphragm?

Back 73

Phrenic nerve, C3-C5

Front 74

What joins to form the brachial plexus?

Back 74

Anterior rami of spinal nerves C5-C8 and T1

Front 75

Peripheral nerves from the brachial plexus innervate what?

Back 75

Upper limbs

Front 76

What joins to form the lumbosacral plexus?

Back 76

Anterior rami of spinal nerves L1-L5 and S1-S4

Front 77

Peripheral nerve emerge from the lumbosarcral plexus to innervate what?

Back 77

The lower limbs and pelvis

Front 78

What provides continuous feedback information to the CNS with respect to muscle length and tension and the rate of change of muscle length and tension during movement?

Back 78

Muscle receptors (proprioceptors)

Front 79

Where is feedback information for muscle receptors directed to?

Back 79

- Spinal cord
- Cerebellum
- Motor cortex

Front 80

What are the two types of muscle receptors?

Back 80

Muscle spindles &
Golgi tendon organs

Front 81

What do muscle spindles function as?

Back 81

Stretch receptors and they detect changes in muscle length

Front 82

What are muscle spindles made up of?

Back 82

Intrafusal muscle fibers

Front 83

What are the muscle spindles attached to?

Back 83

Glycocalyx of surrounding extrafusal fibers

Front 84

The central region of the spindle is innervated by what types of sensory nerves?

Back 84

Types Ia & II
- the central region is extremely sensitive to stretch

Front 85

The end portions of the intrafusal fibers contain actin and myosin and are innervated by?

Back 85

A-gamma motor fibers from the brain stem

Front 86

Golgi tendon organs

Back 86

Sensory receptors located in the muscle tendons near the point of attachment of the tendons to the skeletal muscle fibers

Front 87

What are golgi tendon organ receptors sensitive to?

Back 87

Tension developed within the muscle

Front 88

What sensory nerves transmit information from the golgi tendon organs to the CNS?

Back 88

Type Ib

Front 89

Where are Type Ib signals directed to?

Back 89

- Spinal cord
- Cerebellum
- Cerebral cortex

Front 90

What is unique to the monosynaptic reflex?

Back 90

Very little delay

Front 91

What do the knee-jerk reflex and other muscle jerk reflexes test?

Back 91

Excitability of motor neurons

Front 92

What is elicited most often by a painful stimulus?

Back 92

Flexor (withdrawal) reflex

Front 93

Flexion of one limb is accompanied by extension of the opposite limb is called?

Back 93

Crossed extension

Front 94

What acts over long distances of the spinal cord to control reciprocal limb movements during locomotion?

Back 94

Crossed extension

Front 95

What does crossed extension prevent?

Back 95

Disturbance of equilibrium

Front 96

What represents a reflex response to irritations of muscle?

Back 96

Muscle spasm

Front 97

What can cause contraction (spasm) of abdominal mucsles?

Back 97

Peritonitis

Front 98

What can cause local muscle spasms or cramps?

Back 98

Ischemia

Front 99

Lesion to the spinal cord can result from a variety of insults:

Back 99

- Trauma
- MS
- ALS
- Tumors
- Infections
- Ischemia

Front 100

What happens during spinal cord transection during the initial period of spinal shock?

Back 100

Both somatic and autonomic reflexes below the lesion are temporarily interrupted - decrease in blood pressure

Front 101

Spinal neurons below the lesion (in spinal transection) regain excitability and some reflex activity, but what is still lost?

Back 101

Sensation and voluntary movement below the transection

Front 102

What is overactivity of the sympathetic nervous system?

Back 102

Autonomic hyperreflexia

Front 103

With whom is autonomic hyperreflexia commonly seen?

Back 103

Patients with cord transections at T5 or above (but unusual with lesions below T10)

Front 104

What can trigger strong autonomic responses below the level of transection?

Back 104

Cutaneous (incision) or visceral (distended bladder) stimulation

Front 105

What does sympathetic discharge below the lesion cause?

Back 105

Intense vasoconstriction (increase BP)

Front 106

What does sympathetic discharge above the lesion cause?

Back 106

Reflex bradycardia and vasodilation, resulting in hypertension

Front 107

Spinal block

Back 107

Local anesthetics are injected into the subarachnoid space of the spinal cord

Front 108

Where is a spinal block injection usually performed?

Back 108

Below the end of the spinal cord (L3-L4 or L4-L5)

Front 109

Where is the uptake of local anesthetics into?

Back 109

- Spinal nerve roots
- Dorsal root ganglia
- Spinal cord

Front 110

What does not affect distribution of local anesthetic in CSF?

Back 110

CSF circulation

Front 111

What are the two complications associated with spinal blocks?

Back 111

Hypotension &
Postspinal headache

Front 112

What occurs as a result of CSF leakage from puncture site?

Back 112

Postspinal headache

Front 113

What is caused by a reduction of CSF pressure in the subarachnoid space that causes tension in the meninges?

Back 113

Post-spinal headache

Front 114

What is the result of venous pooling and decreased venous return caused by sympathetic nervous system blockade?

Back 114

Hypotension

Front 115

What is placement of local anesthetics into the epidural space of the spinal cord?

Back 115

Epidural block
Typically at the lumbar level

Front 116

Where is the major site of action for epidural blocks?

Back 116

Spinal nerve roots

Front 117

Is onset of epidural block faster or slower than spinal block?

Back 117

Slower
No free-moving fluid

Front 118

What nerves are blocked during epidurals?

Back 118

- Sympathetic
- Sensory
- Motor