Lecture 16 Flashcards
(127 cards)
1
Q
What are the 4 main functions of the spinal cord?
A
- Conduction
- Neural Integration
- Locomotion
- Reflexes
2
Q
How does the spinal cord use conduction?
A
Nerve fibers conduct sensory and motor information up and down the spinal cord
3
Q
How does the spinal cord use neural integration?
A
It can integrate the stretch sense action from a full bladder with cerebral input concerning the appropriate time and place to urinate and execute control of the bladder accordingly
4
Q
How does the spinal cord use locomotion?
A
Simple repetitive muscle contractions - coordinated by groups of neurons: central pattern generators (CPGs)
E.G. put 1 foot in front of another, over and over while walking
5
Q
What are central pattern generators (CPGs)?
A
Circuits of interneurons present within different spinal cord segments
6
Q
What happens when central pattern generators (CPGs) are activated?
A
They produce the patterns of neural activity that underlie rhythmic motor behaviors such as walking, breathing, flying, and swimming
7
Q
What are reflexes in the spinal cord?
A
Involuntary responses to stimuli that are vital to posture, motor coordination and protective responses to pain of injury
8
Q
What is the filum terminate?
A
Portion of the pia mater that supports the cauda equina
9
Q
What is the cervical enlargement for?
A
For the brachial plexus
10
Q
What is the lumbosacral enlargement for?
A
For lumbosacral plexus
11
Q
What is the gross structure of the spinal cord?
A
Cylindrical structure
12
Q
What is the foramen magnum?
A
Opening in occipital bone for the spinal cord
13
Q
What is the medullary cone (conus medullaris)?
A
Lower end of the spinal cord
At L1 level
14
Q
What it the cauda equina?
A
“Horse’s tail” in Latin
Bundle of spinal nerves
15
Q
What does the central canal contain?
A
CSF
16
Q
What is gray matter?
A
Butterfly or “H” shaped neuron cell bodies
17
Q
What are the 3 meninges layers from most inner to most outer?
A
Pia mater
Arachnoid mater
Dura mater
18
Q
What does the 3 layers of meninges protect?
A
The brain and the spinal cord
19
Q
What is white matter?
A
Myelinated axons
Organized in tracts
20
Q
Which root is sensory in a spinal nerve?
A
Posterior root of spinal nerve
21
Q
Which root is motor in a spinal nerve?
A
Anterior root of spinal nerve
22
Q
Why isn’t there any anterior root ganglion?
A
Somas of these neurons are in the gray matter of the spinal cord
23
Q
What is the white matter divided into?
A
3 columns (funiculi)
24
Q
What is the gray matter subdivided into?
A
Into regions that are referred to as horns
25
What does the lateral gray horn contain?
Bodies of autonomic motor neurons: these innervate cardiac muscle, smooth muscle, and glands (sympathetic NS)
Only through T1-L2
26
What are within regions of gray matter?
Various functional groups of neuron cell bodies (nuclei)
27
What does the dorsal root ganglion contain?
Contains the cell bodies of the (1st order) sensory neurons
28
What does the ventral root allow for?
(Anterior root) allow motor neuron to exit the spinal cord
29
What does the dorsal root allow for?
(Posterior roots) allow sensory neurons axons to enter the spinal cord
30
What are tracts in the spinal cord?
Bundles of CNS axons that share a common origin, destination, and function
31
What are ascending tracts also known as?
Somatosensory pathways or systems
32
What are the 3 primary types of ascending pathways on each side of the spinal cord?
- Spinothalamic (or anterolateral) pathway
- Spinocerebellar pathway
- Dorsal column-medial lemniscus pathway
33
What is it called when the origin and destination of a tract are on the same side of the body?
Ipsilateral
34
What is is allied when the origin and destination of a tract are on the opposite sides of the body?
Contralateral
35
What is the decussation?
The point at which some tracts cross over from left side of the body to right side, or vice versa
36
How many tracts are in the spinothalamic (or anterolateral) system?
2 seperate tracts
37
What is the function of the lateral tract in the spinothalamic system?
Temperature
Pain
38
What is the function of the anterior tract in the spinothalamic system?
Crude touch (non-discriminative)
Pressure
39
What is the substantia gelatinosa?
Synapse at the tip of the dorsal horn
40
Although the tracts are functionally different in the spinothalamic system, they run along side each other. So what are they considered?
They are considered as a single pathway
41
What does the fibers (tracts) do in the spinothalamic system?
These fibers decussate within the spinal cord (cross to the other side)
42
How many neurons are in the spinocerebellar tracts?
2
43
What type of sensation does the spinocerebellar tracts provide?
Unconscious sensation
44
What is the proprioceptive input from the Golgi tendon organism muscles, spindles, and joint capsules for?
For the control of posture and coordination of movements
45
What sensory modalities does the dorsal column-medial leminscus (DCML) pathway carry?
Fine (discriminative) touch
Proprioception (movement & joint position)
These are conscious sensation
46
What are the 2 fascicles does the DCML contain?
Fascilusus cuneatus
Fasciculus gracilis
47
What sensations are the fasciculus cuneatus from?
Sensations from upper limb and chest
(T6 and above travel here)
48
What sensation are the fasciculus gracilis from?
From lower limbs and lower trunk
(Below T6 travel here)
49
What is the second-order neuron of the DCML?
The medial lemniscus
50
Where is the medial lemniscus formed?
In the medulla as fibers form the posterior column nuclei cross the midline
51
Dorsal column = ____
Posterior funiculus (spinal cord)
52
How many major groups is the spinal cord functionally divided into?
2
53
What is the cerebral motor cortex responsible for?
Responsible for the voluntary (conscious) control of the musculature
54
What is the corticobulbar tract?
Musculature of the head and neck
55
What is the corticospinal tract?
Musculature of the limbs and trunk
56
Where are pyramidal tracts originated in?
Cerebral motor cortex
57
Where are extrapyramidal tracts (EPTs) originated in?
Brainstem
58
What are the 2 groups of descending motor tracts in the spinal cord?
Pyramidal (voluntary)
Extrapyramidal (involuntary)
59
What is the brainstem responsible for?
Responsible for the involuntary and automatic control of the musculature
60
What are the 4 extrapyramidal tracts?
Vestibulospinal tract
Reticulospinal tract
Tectoospinal tract
Rubrospinal tract
61
What does the vestibulospinal tract do?
Help maintain balance
62
What does the reticulospinal tract do?
Transmission of pain signals
(Also involved in analgesic pathways)
63
What does the tectospinal tract do?
Head-turning reflex in response to visual and auditory stimuli
64
What does the rubrospinal tract do?
Regulation of muscle tone
65
What kind of muscles do corticospinal pathways control?
Contralateral muscle
(Involve 2 motor neurons: lower and upper)
66
What does the posterior root in a spinal nerve contain?
Sensory axons only
67
Where are cell bodies of sensory neurons located in the posterior root?
The cell bodies are located in a posterior root ganglion
68
How is a single anterior root (or ventral root) formed?
Multiple anterior rootless arise from the spinal cord and merge to form it
69
What do anterior roots contain?
Motor axons only
70
Where do motor axons in anterior roots arise from?
From cell bodies in the anterior and lateral horns of the spinal cord
71
What does a typical peripheral nerve consist of?
Several axon bundles, or fascicles
72
What is each fascicle in a peripheral nerve composed of?
Motor, sensory and sympathetic fibers
73
What is fused to form a spinal nerve?
The dorsal and ventral nerve
74
What are the 3 connective tissue layers in a spinal nerve?
Epineurium
Perineurium
Endoneurium
75
What is the epineurium?
Covers peripheral nerve
76
What is the perineurium?
Around one fascicle
77
What is the endoneurium?
The intrafascicular connective tissue
78
A spinal nerve also contains unmyelinated what?
Unmyelinated nerve fibers in the same fascicle
79
What are the 5 nerve sections in the spinal cord from top to bottom?
Cervical (C1-C8)
Thoracic (T1-T12)
Lumbar (L1-L5)
Sacral (S1-S5)
Coccygeal (Co1)
80
How many pairs (mixed nerves) are there in the spinal cord?
31
81
What does each segmental region of the spinal cord innervate?
A specific region of the skin, muscle, or organ group
82
What can damage to the spinal cord result in?
In partial or complete loss of function below the level of the injury
83
What is a dermatome map?
A diagram of the cutaneous regions innervated by each spinal nerve
84
What can a clinician do following a traumatic injury?
They can test dermatomes to determine the presence and the extent of a spinal cord lesion
85
What are dermatomes?
Areas of sensation
86
What is a nerve plexus?
A branching network of intersecting nerves
87
What are the 5 plexuses of the spinal cord from top to bottom?
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
Coccygeal plexus
88
What do nerves emerging from a plexus contain?
Contain fibers from various spinal nerves which are now carried together to some target location
89
What is the sciatic nerve?
A combination of 5 nerve roots that exit from inside the lower lumbar and upper sacral spine (L4, L5, S1, S2, S3)
90
What is the largest branch of the sacral plexus?
The sciatic nerve
91
What does ‘Sciatica’ refer to?
Refers to symptoms related to compression of the sciatic nerve
- Herniated disc (disc moves out of place)
- Muscle spasm
92
What can the sciatic nerve produce?
Pain that radiates from the lower back along the path of the sciatic nerve
93
What are the 3 properties of a reflex?
Quick
Involuntary
Stereotyped
94
What does quick mean in reflexes?
Involve few, if ay, interneurons and minimum synaptic delay
95
What does involuntary mean in reflexes?
Occur without intent and are difficult to suppress
96
What does stereotyped mean in reflexes?
Occur essentially the same way every time (automatic)
97
What are visceral reflexes?
Involve a glandular or non-skeletal muscular response carried out in internal organs such as the heart, blood vessels, or structures of the GI tract
98
What are somatic reflexes?
Relaxes involving the somatic nervous system innervating skeletal muscle
99
What are the steps in a reflex arc?
1. Stimulus activates receptor
2. Nerve impulse travels though sensory neuron to the spinal cord (afferent fibers)
3. Nerve impulse is processed in the integration center by interneurons
4. Motor neuron transmits nerve impulse to effector (efferent)
5. Effector responds to impulse from motor neuron
100
What is a reflex arc?
The neural “wiring” (pathway) of a single reflex
101
The simplest reflexes do not involve what?
Do not involve interneurons
102
What is the 5th step in a reflex arc intended to do?
Intended to counteract or remove the original stimulus
103
What is a MONOsynaptic reflex?
Direct communication between sensory and motor neuron
(Presence of a single chemical synapse)
104
What is a POLYsynaptic reflex?
Interneuron(s) facilitates sensory-motor communication
105
Monosynaptic reflexes have very ___ and very ___
Very minor synaptic delay
Very prompt reflex response
106
What is a stretch (myotactic reflex) reflex?
Monosynaptic reflex that monitors and regulates skeletal muscle length
107
What is a stretch in a muscle monitored by?
A stretch receptor called a muscle spindle
108
What happens when a stimulus results in the stretching of a muscle?
The muscle reflexively contracts
109
What happens in the patellar reflex?
The stimulus stretches the quadriceps fermoris muscle and initiates contraction of the muscle, thereby extending the knee joint
110
What are muscle spindles?
Stretch receptors embedded in skeletal muscle that primarily detect changes in the length of the muscle
111
What are gamma motor neurons?
Innervate the muscle spindle at each end
112
What are alpha motor neurons?
Innervate the extramural muscle fibers
113
What shape are muscle spindles?
Fusiform (spindle shaped)
114
Where do muscle spindles receive sensory innervation?
In the middle
115
What are extrafusal muscle fibers?
The normal, contractile muscle fibers found in skeletal muscles
They are outside of the spindle
116
What are intrafusal muscle fibers ?
The specialized fibers that make up the muscle spindle
117
What is the golgi tendon reflex?
A response to excessive tension on the tendon
118
The golgi tendon reflex has interneurons that do what?
They inhibit alpha motor neurons to the muscle: muscle relaxation
119
What does the golgi tendon reflex protect the muscle from?
Protects the muscle from extensively heavy loads by causes the muscle to relax and drop the load
120
Where are nerve ending located in the golgi tendon?
Within the tendons
121
What happens when muscle contraction pulls on the tendon?
The collagen fibers come together and squeeze the nerve (sensory) endings between them
122
What is the flexor (withdrawal) reflex?
The quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus
123
Flexor ____ Extensor ____
Contraction
Relaxation
124
How are pain receptors initiated?
Initiated by painful stimulus
125
What happens simultaneously in the flexor reflex?
Antagonist (extensor) muscles are inhibited
126
What is the crossed extensor reflex?
Extends and stiffens that limb and enables you to keep your balance
127
Motor neurons will be stimulated or inhibited depending on what?
Depending on the muscle
