Session 5: Neuroanatomy and Physiology of the Spinal Cord Flashcards
(108 cards)
1
Q
How long is the spinal cord in males? In females?
A
Males: 45 cm
Females: 42 cm
2
Q
What is the approximate diameter of the spinal cord?
A
1.0-1.5 cm
3
Q
At what vertebral level does the spinal cord end?
A
L1-L2
4
Q
The disparity in length of the spinal cord is due to what?
A
The differential growth of the spinal cord versus the vertebral column.
5
Q
There are two observable enlargements along the length of the spinal cord. Where are they?
A
one in the cervical region, one in the lumbar/sacral regions.
6
Q
What are the observable enlargements of the spinal cord?
A
Their occurrence marks the ares of the spinal cord that contain the neurons concerned with the upper and lower extremities.
7
Q
Rostrally, the cord is continuous with what?
A
The medulla
8
Q
Caudally, the spinal cord tapers into what?
A
The conus medullaris.
9
Q
What happens to the dorsal and ventral roots after the conus medullaris?
A
They continue caudally through the lower lumbar and sacral segments, exiting their appropriate intervertebral foramina.
10
Q
What is the cauda equina?
A
The collection of long dorsal and ventral roots of the lower lumbar and sacral segements.
11
Q
What are the roots in the cauda equina long?
A
Due to the differential growth of the cord versus the spine.
12
Q
What 3 layers cover the spinal cord?
A
3 layers of meninges:
- Dura mater
- Arachnoid mater
- pia mater.
13
Q
How is the dura covering the spinal cord different than the dura covering the brain? Where does it make this transition?
A
Spinal cord dura: only a meningeal layer.
Periosteal layer ends at the foramen magnum.
14
Q
What fills the epidural space in the spinal cord?
A
Fat
15
Q
True or false. The arachnoid is arranged differently in the spinal cord.
A
False.
The organization of the arachnoid is much the same, acting as the limiting component for CSF containment.
16
Q
How does CSF enter the subarachnoid space of the spinal canal?
A
From the foramina of luschka and Magendie
17
Q
What is the lumbar cistern?
A
A large pocket of subarachnoid space below the caudal tip of the cord. Exists because the cord ends at vertebral levels L1-L2.
18
Q
What procedure is routinely done at the lumbar cistern.
A
Lumbar punctures (spinal taps). It is safe to make punctures in this region.
19
Q
What are the two layers of the pia?
A
pia intima
layer that forms detniculate ligaments
20
Q
What are denticulate ligaments?
A
The extensions that protrude from the lateral sides of the cord and pierce the arachnoid to attach to the dura.
21
Q
What is the purpose of denticulate ligaments?
A
Help anchor and stabilize the cord in the vertebral canal.
22
Q
What is located at the caudal end of conus medullaris?
A
The filum terminale ligament
23
Q
What makes up the filum terminale?
A
pia, glial elements and some remnants of coccygeal neuronal elements.
24
Q
What is the coccygeal (sacral) ligament a continuation of?
A
The filum terminale
25
Where does the filum terminale become the coccygeal ligament?
Where the ligament extends through/and is encased with teh dura to attach to the coccyx.
26
What is the purpose fo the coccygeal ligament?
Anchors the end of the cord in the spinal canal.
27
How does the spinal cord develop?
Segmentally
28
What structures develop segmentally besides the spinal cord?
Somites, dermatomes, myotomes and sclerotomes
29
How many pairs of spinal nerves are there? How many per region of the spine? (cervical, thoracic, lumbar, sacral, coccygeal)
```
31(32) pairs
8 cervical
12 thoracic
5 lumbar
5 sacral
1(2) coccygeal
```
30
During spinal cord development is the segmental arrangement visible?
No- obscured.
31
What evidence is there of spinal cord segmental arrangement?
The rootlets of the spinal nerves
32
What two places is the segmental arrangement of the spinal cord represented?
1. Dermatomal maps
| 2. multisegmental innervation of muscles.
33
What is the clinical significance of spinal cord segmentation?
Important in discerning the extent and/or location of a deficit, by documenting the loss of certain sensations or changes in motor activity, following damage to the central nervous system.
34
What are the two main subdivisions of the spinal cord?
gray matter
| white matter
35
What is the central butterfly shaped area of the spinal cord?
Gray matter
36
What makes up the gray matter of the spinal cord?
neuron cell bodies and their dendritic processes and glial cells
37
What surrounds the gray matter in the spinal cord?
White matter
38
What makes up the white matter of the spinal cord?
Myelinated axons
39
What is contained in the white matter of spinal cord?
ascending and descending fiber tracts or pathways
40
What are funiculi? How many general locations are they divided into?
A bundle of nerve tracts that make up the white matter of the spinal cord.
Can be divided into 3 general locations.
41
What are the 3 funiculi of the spinal cord?
1. Dorsal (posterior) funiculus
2. Lateral funiculus
3. Ventral (anterior) funiculus
42
What are the specific named tracts or pathways that make up each funiculus called?
Fasciculi
43
How are specific pathways named? Give an example.
- Descriptive of location within the transverse section of the spinal cord
- may also give an indication of what areas within the CNS the pathway is connecting.
Example: Lateral corticospinal tract. 1)located in the lateral funiculus 2)originates in the cortex of the cerebral hemisphere, ending in the spinal cord
44
True or false.
Gray matter of the spinal cord was set up developmentally.
True.
45
The alar plate is (VENTRALLY/DORSALLY) located and is concerned with (SENSORY/MOTOR) components of the cord
Dorsally
| Sensory (afferent)
46
The basal plate is located (VENTRALLY/DORSALLY) and is concerned with the (SENSORY/MOTOR) components of the cord.
Ventrally
| Motor (efferent)
47
What is the butterfly shaped gray area divided into?
```
Dorsal horn (sensory)
Ventral horn (motor)
```
48
The lateral horn (intermediolateral cell column) is present in what spinal cord segments?
Spinal cord segment T1-L2.
49
What is located in the lateral horn?
preganglionic sympathetic neurons (a component of the ANS)
50
What is found in sacral segments (S1-S3)?
Lateral horn contaning preganglionic parasympathetic neurons for the lower parts of the body- the other part of the ANS
51
The gray matter is divided into various nuclei or divisions as a result of what? (2)
cellular (cytoarchitecture) and connectional studies
52
What is Lamina of Rexed?
A system of 10 layers of gray matter (indicated by roman numerals)
53
What is Lissauer's Tract?
Dorsolateral tract present in the entirety of the spinal column. Carry pain and temperature information.
54
What is the substantia gelatinosa (Lamina II)?
Located in the dorsal horn of the spinal cord, the substantia gelatinosa where first order neurons of the spinothalamic tract synapse.
55
What is the nucleus proprius (Lamina III, IV)?
Located in the dorsal horn. It constitutes the first synapse of the spinothalamic tract carrying pain and temperature sensations from peripheral nerves.
56
What is the dorsal nucleus of Clarke?
A group of interneurons in the the medial part of the base of the dorsal column. Serves as a relay center for unconscious proprioception.
57
At what spinal cord segmental levels would you find the dorsal nucleus of clarke?
T2-L2
58
What is the intermedilateral cell column (lateral horn)?
Area of the spinal cord that contains the autonomic motor neurons that give rise to the preganglionic fibers of the sympathetic nervous system.
59
Where is the intermediolateral cell column/lateral horn found in the spinal cord?
Segmental levels C8/T1-L2, also segmental levels S1-S3
60
What is located in the ventral horn?
Lower motor neurons
61
Why do several areas and nuclei need to be identified in the dorsal horn?
Because it is concerned with incoming sensory information.
62
What does nuclei refer to, in regards to spinal cord organization?
Refers to a group of cells with similar properties/connections
63
True or False. Fibers that enter the cord via the dorsal roots are organized anterior to posterior.
False.
| Organized medially to laterally.
64
The most medially situated fibers are (SMALL/LARGE) diameter, (HEAVILY/LIGHTLY) myelinated, __, ___ and ____ type fibers
Large
Heavily
Ia/b, a-alpha, II
65
The more laterally placed fibers are the (SMALL/LARGE) diameter, (MYELINATED/NONMYELINATED), type ___ fibers.
Small
Non-myalinated
Type C
66
Intermediate fibers in the dorsal root are (HEAVILY/LIGHTLY) myelinated, type ___ fibers.
Lightly
| A-delta
67
Where do the axons from the cell bodies found in the ventral horn travel? What do they innervate?
Leave the spinal cord
| Innervate muscles.
68
What are lower motor neurons?
The cell bodies with axons that leave the spinal cord and innervate muscles.
69
What is the final common pathway?
Concept that all motor control signals ULTIMATELY synapse on α-motor neurons.
70
What two types of lower motor neurons are found in the ventral horn?
alpha motor
| gamma motor
71
How are the cell bodies of alpha and gamma motor neurons arranged within the ventral horn?
Those situated most medially are concerned with axial musculature (trunk, neck, etc)
72
True or False. The cell column involving axial musculature extends throughout the entire length of the cord.
True
73
The LMNs situated more laterally innervate what?
Muscles of the extremities.
74
LMNs situated posteriorly in the ventral horn are concerned with what?
Muscles of flexion
75
LMNs situated anteriorly in the ventral horn are concerned with what?
Muscles of extension
76
What is formed by the merging of the dorsal and ventral roots away from the spinal cord?
The spinal nerve
77
Prior to their merging, the dorsal root is (SENSORY/MOTOR/MIXED) and the ventral root is (SENSORY/MOTOR/MIXED.
Dorsal: sensory
Ventral: motor
78
Once the dorsal and ventral roots combine the spinal nerve becomes (SENSORY/MOTOR/MIXED)
Mixed.
79
True or False. The spinal nerve is a component of the PNS.
True.
80
Each spinal nerve branches into a number of other branches to reach one of 2 areas:
1. specific dermatomal segment
| 2. muscle of innervation
81
What is associated with spinal nerves at levels T1-L2?
A series of autonomic ganglia.
82
What is located at the ganglia of T1-L2?
postganglionic cell bodies for the SNS.
83
Where are the preganglionic cell bodies located?
The lateral horn in the spinal cord (intermediolateral cell column)
84
What are reflexes?
Specific, stereotyped motor responses to an adequate (appropriate) stimulus.
85
Reflexes require a series of structures consisting of a minimum of what 4 components? (complex reflexes may contain more connections in the CNS)
1. Receptor
2. Afferent limb
3. Efferent limb.
4. Effector organ
86
What type of receptors are involved in reflexes?(2)
1. Muscle spindles
| 2. GTOs
87
What type of nerve endings are involved in reflexes? (2)
1. encapsulated
| 2. Free nerve endings
88
What is the role of the afferent limb in reflexes? Name a part of the nervous system involved in this.
Carries the impulse (stimulus) into the CNS
Example: dorsal root fibers
89
What is the role of the efferent limb in reflexes? Name a part of the nervous system involved in this.
Carries the impulse for the response out of the CNS
Example: lower motor neuron (alpha motor)
90
Give 2 examples of effector organs involved in reflexes.
Skeletal muscle
| Glands
91
What is an example of a stretch reflex or deep tendon reflex?
Patellar ligament/knee jerk
92
What two concepts are demonstrated in a stretch reflex?
1. Autogenic facilitation
| 2. Reciprocal inhibition
93
What is autogenic facilitation?
The process of inhibiting the muscle that generated a stimulus while providing an excitatory impulse to the antagonist muscle.
94
What is reciprocal inhibition?
The process of muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint.
95
What is the golgi tendon organ sensitive to?
tension when the associated muscle is conracted.
96
At a certain point of increased tension on the GTO, what occurs? What is this known as?
The stimulus generates an inhibitory influence to the alpha motor neurons that are driving the contracting muscle
Known as autogenic inhibition
97
What occurs once autogenic inhibition occurs?
The muscle can relax, releasing the tension.
98
What is reciprocal facilitation?
Through the interneuronal pool, the antagonistic muscle can be activated to facilitate the release of tension.
99
What reflexes are more complex than the tendon organ reflex?
1. Flexor withdrawal reflex
| 2. Crossed extension reflex.
100
What is the flexor withdrawal reflex?
is a spinal reflex intended to protect the body from damaging stimuli.
It is polysynaptic, causing stimulation of sensory, association, and motor neurons.
101
What is the crossed extension reflex?
Occurs on the contralateral side of a the flexor withdrawal reflex, so that it can support the body when the flexor withdrawal reflex occurs.
102
What must occur with the flexor withdrawal reflex and crossed extension reflex?
Reciprocal inhibition of antagonist or opposing muscle masses.
103
What inhibitory circuits function in the flexor withdrawal and crossed extension reflexes? (3)
1. Reciprocal inhibition
2. Recurrent inhibition
3. Non-reciprocal inhibition
104
Reciprocal inhibition occurs where during the Flexor withdrawal/crossed extension reflex?
Antagonistic muscle
105
Recurrent inhibition occurs where during the Flexor withdrawal/crossed extension reflex?
Same muscle and synergists via Renshaw cells (inhibitory interneurons)
106
Non-reciprocal inhibition occurs where during the Flexor withdrawal/crossed extension reflex?
Agonists, synergists and antagonists (coordination of various movements)
107
What structures are involved in segmental loss of the spinal cord. Be specific.
Involves the structures present at the specific segmental level. Includes:
- gray matter areas of the cord
- to some extent the dorsal and ventral root components that are bringing in sensory information and/or sending out motor information
108
What is also involved but generally not included in the definition of segmental loss?
- additional involvement of ascending and descending white matter pathways
- in the real world, segmental losses will most likely include some involvement of this white matter
