Neuromodulation of the Central Nervous System Flashcards
1
Q
Name the six components of the central nervous system
A
Spinal cord, brain stem, cerebellum, midbrain, diencephalon, and cerebrum
2
Q
Name the components of the brainstem
A
medulla, pons, and midbrain
3
Q
What is the function of the medulla?
A
digestion, breathing, heart rate control
4
Q
What is the function of the pons?
A
movement of information from hemispheres to the cerebellum
5
Q
What is the function of the cerebellum?
A
motor tasks, learning, force-range of movement
6
Q
What is the function of the midbrain?
A
sensory-motor functions, eye movement, visual-auditory reflexes
7
Q
What are the two components of the diencephalon?
A
thalamus and the hypothalamus
8
Q
What is included in the cerebrum?
A
cerebral cortex, basal ganglia, hippocampus, and amygdaloid nuclei
9
Q
The medial lemniscus links __ receptors and __ __ for all modalities-sensations except __
A
sensory, cerebral cortex
smell
10
Q
Sensory decussation occurs at the ___
A
medulla
11
Q
Fibers that originate in the primary motor cortex and terminate in the __ horn of the __ __ constitute a significant part of the __ tract engaged in ___
A
ventral; spinal cord
corticospinal
movement
12
Q
Describe the descending lateral corticospinal pathway
A
In the cerebral cortex (primary motor cortex) thru internal capsule
Down to midbrain (cerebral peduncle)
Pons
Medulla
Medulla/ spinal cord junction - pyramidal decussation to contralateral side)
Lateral corticospinal tract
Spinal cord to lateral motor muscle
13
Q
Describe the ascending pathway of sensation
A
Sensation in thru dorsal root ganglion to medulla
Medulla - sensory decussation to contralateral side
Pons (medulla + pons = medial laminiscus)
Midbrain
Ventral posterior lateral nucleus
Somatosensory cortex
14
Q
__, __, and __ are involved in the control of simple tasks, including walking
A
motor cortex, brain stem, and spinal cord
15
Q
The right lobe receives signals from the __ side of the body
A
left
16
Q
Sensory information regulates __
A
movement
17
Q
Reflexes are __ and __ based on the task
A
flexible and adapted
18
Q
Reflexes are integrated by centrally generated __ commands into __, __ movements
A
motor
complex, adaptive
19
Q
Where do the sensory stimuly for spinal reflexes arise from?
A
receptors in muscles, joints, and skin
20
Q
The neural circuitry responsible for the motor response is contained where?
A
Entirely within the spinal cord
21
Q
What are two types of spinal reflex pathways?
A
Polysynaptic and monosynaptic
22
Q
Spinal reflexes produce __ patterns of __ contraction
A
coordinated; muscle
23
Q
Cutaneous reflexes produce __ movements that serve __ and __ functions
A
complex
protective; postural
24
Q
The __-__ reflex is purely spinal
A
flexion-withdrawal
25
The stretch reflex is purely __, it __ the muscle lengthening
spinal; resists
26
What are Renshaw cells?
interneurons whose primary role is recurrent inhibition of the same motor neurons which they are excited by
27
Modulation of spinal reflexes is __ dependent
task
28
Neural signalign in reflex pathways is adjusted according to the __ __
motor task
29
The state of the reflex pathways for any task is referred to as?
The function set; establishment unknown
30
Sensory input from a localized source generally produces ___ reflex responses in __ __ at once, some of which may be __ from the stimulus
coordinated; many muscles
distant
31
Supraspinal centers play an important role in __ and __ spinal reflexes, even to the extent of __ __ when appropriate
modulating; adapting
reversing movements
32
Local spinal circuits contribute to the __ of __ responses
coordination; reflex
33
T/F: la fibers make indirect connections to the alpha motorneurons
False! Direct connections
34
La fibers from a muscle __ not only the __ innervating the __ (homonymous) muscle, but also those innervating __ (heteronymous) muscles with a __ __ action
excite
motor neurons
same; other
similar mechanical
35
What is the basis for reciprocal innervation?
disynaptic inhibitory pathway
36
Explain the disynaptic inhibitory pathway in lamends terms
When a muscle is stretched, its antagonists relax
37
Divergence in reflex pathways __ __ inputs and __ __ movements
amplifies sensory
coordinates muscle
38
In all reflex pathways in the spinal cord, the __ neurons form divergent connections with a __ number of target neurons through extensive __ __
sensory
large
axonal branching
39
T/F: Stimulation of a small number of sensory axons from a small area of skin is sufficient to cause contractions of widely distributed muscles and thus to produce a coordinated motor pattern
true
40
Individual la axons make __ synapses with all __ __ neurons innervating the medial gastrocnemius of the cat-autogenic excitation
excitatory
homonymous motor
41
T/F: convergence of inputs on Ib interneurons decreases flexibility of reflex responses
False, increases flexibility
42
Describe how the convergence of inputs on Ib interneurons increases reflex response flexibility
Ib inhibitory interneuron receives input from tendon organs, muscle spindles, joint and cutaneous receptors, and descending pathways
action of Ib sensory fibers on extensor motor neurons is REVERSED from Inhbition to excitation when walking is initiated
43
T/F: Central motor commands and cognitive processes can alter synaptic transmission in spinal reflex pathways
true
44
__ and __ of synaptic transmission in spinal reflex pathways can be altered during __ acts
strength; sign
behavioral
45
The __ of the __ reflex declines as we progress from standing to walking to running (__-__ reflex reversal)
strength monosynaptic
state-dependent
46
What are the three sites in the reflex pathway which central neurons can regulate the strength of spinal reflexes?
Synaptic transmission can be modified at
1. alpha motor neurons
2. interneurons in all reflex circuits EXCEPT monosynaptic pathways
3. presynaptic terminals of the afferent fibers
47
Gamma motor neurons adjust the __ of __ spindles
sensitivity; muscle
48
Where do gamma motor neurons innervate?
the intrafusal muscle fibers of muscle spindles
49
The __ of the intrafusal fibers by the __ motor neurons keeps the spindle under __, maintaining the __ __ of the Ia fibers within an optimal range for signaling changes in __
contraction; gamma
tension
firing rate
length
50
What is the function of the alpha-gamma co-activation?
stabilizes the sensitivity of the muscle spindles, used in many voluntary movements
51
What else, aside from axons of gamma motor neurons, innervate the intrafusal fibers?
axon collaterals of alpha motor neurons
52
Define beta axons
axons that innervate both intrafusal and extrafusal muscle fibers
53
Reflexes involving limb movements are mediated through __ and __ pathways
spinal; suprapinal
54
What does M1 represent?
short-latency, monosynaptic, spinal
55
MC is for __; subcortical is for __
distal; proximal
56
What does M2 represent?
long-latency, long-loop pathway involving motor cortex
57
Reflexes of the limbs are mediated by __ __ pathways and __ __ pathways that involve the __ cortex
spinal reflex; long-loop
motor
58
What happens in Klippel-Fell syndrome?
Motor response is generated at both sides of the body
59
What do co-activation of alpha and gamma motor neurons by a cortical motor command allow for?
Feedback from muscle spindles to reinforce activation in the alpha motor neurons
60
The discharge rate in the Ia sensory fiber of a spindle increases during __ __ of a finger
slow flexion
61
The increase of a discharge rate in the Ia sensory fiber of a simple is dependent on?
The alpha-gamma co-activation
62
If the gamma motor neurons were not active, the spindle would __, and its discharge rate would __ as the muscle __
slacken, decrease, shortened
63
When are alpha and gamma motor neurons co-activated?
During voluntary movements
64
Damage to the CNS produces characteristic alterations In __ __ and __ __
reflex response; muscle tone
65
Interruption of descending pathways to the spinal cord frequently produces __
spasticity
66
What happens during transection of the spinal cord in humans?
A period of spinal shock followed by hyperreflexia
67
Define cell body
metabolic center of the cell
nucleus with genes and endoplasmic reticiulum that synthesizes the proteins
aka soma
68
Define the function of the dendrites
receive incoming signals from other cells
69
Define the function of axons
carries signals to other neurons
70
What is the size of axons?
0.1 mm to 2m
71
Where can presynaptic terminals terminate?
dendrites, soma, or axons
72
What are the 9 categories of perception?
Vision
Smell
Taste
Touch
Thermal senses
Pain
Hearing
Balance
Proprioception
73
Define a reflex
coordinated, involuntary motor response initiated by a stimulus applied to peripheral receptors
74
The actual response evoked by a reflex is dependent on?
The mechanisms that set the strength and pattern of responses according to the task and the behavioral state, or functional set
75
T/F: modification of synaptic transmission in spinal reflex pathways by descending signals from the brain is thought to be an important factor
True
76
Many groups of __ in spinal reflex pathways are also involved in producing __ __ such as walking and transmitting voluntary commands from the __
interneurons
complex movements
brain
77
Why does injury to or disease of the CNS often result in significant alternations in the strength of spinal reflexes?
role of supraspinal centers in spinal reflex pathways
78
Neurons receive both __ and __ inputs via __ receptors in the __ __
excitatory, inhibitory
ionotropic
postsynaptic membrane
79
What applies to the synaptic connection between the __ __ and the __ __ also applies to the CNS but is also more __ __ __
motor neuron; skeletal muscle
complex non specific
80
T/F: Muscle fibers are innervated by many motor neurons
False, only one
81
T/F: spinal cord motor neurons receive connections from hundreds/ thousands of other neurons
true
82
Muscle fibers receive only __; central neurons receive __/__ inputs
excitatory
excitatory/ inhibitory
83
All synaptic actions on muscle fibers are mediated only by __ which activates only __ type of __ __ __ ___
ACh; one
specific ionotropic-metabotropic receptors
84
What is a role of central neurons?
they integrate diverse inputs into a single coordinated activity
85
T/F: every action potential in the motor neuron produces an action potential in the muscle fiber
true
86
How many excitatory neurons must fire together to produce a synaptic potential?
50-100 excitatory
87
Tendon tap does not produce __ __ of the muscle spindle afferents, thus __ stimulation is preferred
synchronized depolarization
electrical
88
Unitary EPSP =
one sensory neuron
89
Increasing the current results in __ __ of sensory __ fibers and the ___ of neurons produced by the EPSP becomes larger
synchronized activation
afferent
depolarization
90
Stimulation of __ __-__ neuron produces IPSPs in the motor neurons that ___ the flexor muscle, which is __ to the extensor
extensor stretch-receptor
innervate
antagonistic
91
The hyperpolarizating action is mediated by an __ __, known as, reciprocal Ia ___ ___, and the circuit constitutes the __ unit for physiological alternated __ __
inhibitory interneuron (IN)
inhibitory interneuron
phasic movement
92
Central synaptic inhibition is __ in most neurological disorders
decreased
93
T/F: Experience refines sensory-motor function
true
94
The shape of myelin can be __ dependent
experience
95
Formation of new myelin was found to be required for...
motor learning in adult mice
96
How do ballerinas differ from typically developing people?
significantly faster long-latency neuromuscular responses than controls
Significantly more consistent in muscle activation
Superior postural control mechanism
Spinal H-reflexes are smaller
97
Name three impacts of the CNS after spinal cord injury (SCI)
impaired function of spinal circuitry and corticospinal drive
impaired processing of afferent input by spinal circuits
decline in transmission of uninjured fibers
98
Most rehabilitation interventions of SCI rely heavily on __ __ __ __ because of the weak or impaired __ -_
compromised spared neuronal pathways
synaptic connections
99
Name three efforts of rehabilitation after SCI
development of targeted neuromodulation interventions
use neuromodulation as a biomarker of motor recovery
use a combination of training interventions to optimize recovery
100
The spinal cord serves as a hub center that integrates and translates __, __, and __ neuronal signals
descending, ascending, segmental
101
T/F: Transspinal evoked potentials (TEPs) are not similar in animals and humans
False - they are similar
102
Describe the TEP recruitment curve
sigmoid shape as the MEP, M-wave, H-reflex
103
Soleus TEPs have nearly the __ __ of soleus H-reflexes in both animals and humans
half latency
104
Define orthodromic
flow of current on afferent inputs and efferent output signals
105
Define antidromic
flow of current on afferents following transspinal stimulation
106
Transspinal stimulation __ motor evoked potentials (MEPs) during __
depresses; walking
107
At the step that transspinal stimulation occurs, locomotor EMG activity is completely __ but fully recovers at the step __ __ __
suppressed
after transspinal stimulation
108
TEPs are likely the result of both __ and __-__ neurons events
synaptic; non-synaptic events
109
Describe four synaptic/ non-synaptic neuronal events that TEPs are likely the result of
1. antidromic discharges of muscle afferents
2. primary afferent depolarization-induced spikes that propagate orthodromic to afferent terminals that subsequently depolarize alpha neurons
3. activation of spinal interneuronal circuits including recurrent and reciprocal Ia inhibition
4. orthodromic excitation of motor axons
110
T/F: transspinal stimulation is a promising neuromodulation modality
true
111
The CNS __ and __ continuously based on __ __ and __
adapts; reorganizes
motor experience; use
112
Reorganization occurs in a __-__ manner throughout the neuro-axis (__,__,__)
task-dependent
cortex, cerebellum, spinal cord
113
What is the key to neuroplasticity?
proprioceptive feedback
114
Describe self-reported changes and clinical assessment outcomes for cervicothoracic and thoracolumbar transspinal stimulation
increased voluntary muscle strength, sweating returned, decrease in leg spasms and decrease in ankle clonus
115
Describe self-reported changes and clinical assessment outcomes for thoracolumbar transspinal stimulation
improved bladder control, improvement in pain, increased walking distance
116
