Exam 4 Flashcards
(115 cards)
1
Q
What are reflexes
A
rapid, stereotyped, involuntary
2
Q
what are rhythmic motor patterns
A
voluntarily initiated and terminated
maintained through reflexes and central pattern generators
Ex. breathing, walking, running
3
Q
what are voluntary movements
A
purposeful
learned
ex. Typing, piano
4
Q
How do muscles work
A
muscles pull on bones to move them at joints; muscles CANNOT push on bones
5
Q
what are flexors
A
decrease joint angle
6
Q
what are extensors
A
increase joint angle
7
Q
what are agonist muscles
A
main muscles that move bones
8
Q
what are antagonist muscles
A
muscles that decelerate movement by agonist muscles and move limbs in opposing directions
9
Q
what are axial muscles
A
move the trunk and maintain posture
10
Q
what are proximal muscles
A
close to the trunk
control the shoulder, elbow, pelvis, and knee joint
critical for posture and locomotion
11
Q
what are distal muscles
A
further from the trunk
control hands, feet, fingers, toes, eyes, face
used for fine manipulation of objects, binocular vision, and facial expression
12
Q
what is the medial part of the ventral horn
A
motor neurons that control proximal and axial/trunk muscles
involved in maintaining posture
13
Q
what is the lateral part of the ventral horn
A
motor neurons that control distal muscles
involved in fine manipulation
14
Q
what is the dorsal part of the ventral horn
A
flexor muscles
15
Q
what is the ventral part of the ventral horn
A
extensor muscles
16
Q
what is a motor unit
A
one motor neuron and all the muscle fibers it innervates
17
Q
what is paresis
A
partial paralysis
18
Q
what is the relationship between motor unit size and precision
A
inversely correlated
less precision –> Large motor units
more precision –> small motor units
19
Q
what are upper motor neurons
A
cells bodies in the neocortex or brainstem nuclei
affect muscles indirectly
20
Q
what are lower motor neurons
A
cell bodies in spinal cord or cranial nerve nuclei
directly contract muscles
21
Q
what is the corticospinal tract
A
mainly involved in conscious control of movement
22
Q
what are 40% of the corticospinal tract fibers
A
originate largely in the somatosensory cortex
terminate in the dorsal horn
modulate proprioception and nociception
23
Q
what are 60% of the corticospinal tract fibers
A
originate in motor and premotor cortical areas
terminate in the ventral horn of the spinal cord
control voluntary movements
24
Q
what is the pathway of the corticospinal tract
A
neocortex –> corona radiata –> internal capsule –> cerebral peduncle –> pons –> pyramids –> spinal cord
25
what is the corona radiata
descending axons from cortical neurons
26
what is the internal capsule
descending UMN axons in the corona radiata come together and mostly travel in the posterior limb of the i.c
27
where do axons of the corticospinal tract decussate
lower medulla (pyramidal decussation)
28
what is the lateral corticospinal tract
axons decussate in lower medulla
innvervates neurons that control distal muscles
synapse in ventral horn
29
what is the anterior corticospinal tract
axons decussate in the spinal cord near the level where they terminate
innervates neurons that control axial and proximal muscles
30
what is the corticobulbar tract
upper motor axons from the primary motor cortex projecting to cranial nerve nuclei in the brainstem
controls movements of the face, tongue, pharynx, and larynx
31
what is lower motor syndrome
caused by damage to lower motor neurons
characterized by:
weakness, paralysis
hypotonia
muscle atrophy
hyporeflexia
32
what is upper motor neuron syndrome
characterized by:
muscle weakness
hypertonia
no muscle atrophy
hyperreflexia
33
what are renshaw cells
spinal interneurons found in the ventral horn
activated by collaterals of motor neurons
prevent ongoing muscle contraction
inhibition of these cells increases the duration of muscle contractions
34
what is tetanus
painful muscle spasms and rigidity
blocks release of glycine from renshaw cells
35
what is the medial pathway
tracts travel primarily in the ventromedial column
controls proximal extensor motor neurons and trunk motor neurons
plays a large role in the descending control of posture
36
what are the main tracts of the medial pathway
tectospinal, vestibulospinal, reticulospinal
37
what is the tectospinal pathway
originates in the tectum which orients reflexes
tectum receives visual, auditory, somatosensory input
innervates interneurons that control neck motor neurons and coarse eye movements
38
what is the vestibulospinal tract
originates in the medial and lateral vestibular nuclei
relays info from vest. system
contributes to:
postural control, sensitivity of stretch reflexes, head and neck movements that compensates for changes in body position
39
what is the reticulospinal tract
originates in the reticular formation
receives vestibular, visual, auditory, somatosensory, cerebellar, and cortical inputs
controls functions such as:
posture, orienting movements, crude voluntary movements (e.g. reaching)
40
what are the types of proprioceptors
muscles spindles
golgi tendon organs
41
what are muscle spindles
maintain muscle length
42
what are golgi tendon organs
maintain muscle tension
43
what are the sensory neuron fibers
Ia sensory afferents (MS)
II sensory afferents (MS)
Ib sensory afferents (GTO)
44
what are the motor neuron fibers
alpha (to skeletal muscle)
gamma (to muscle spindles)
45
where are muscle spindles located
embedded in skeletal muscles
run parallel with extrafusal fibers
46
what are the phases of muscle stretch
static (constant length)
dynamic (muscle length is changing)
47
describe Ia afferents
rapidly firing
firing rate changes during dynamic
firing during static is proportional to amount of stretch
senses both velocity of stretch and amount of muscle stretch
48
describe II afferents
slowly adapting
firing rate during static phases is proportional to amount of stretch
senses amount of muscle stretch during static phases
49
where is the golgi tendon organ located
capsule containing collagen fibers
attached to muscle on one end and to a tendon on the other
in series with extrafusal muscle fibers
50
Describe how golgi tendon organs sense muscle tension
Tension on the GTO compresses the branches of the Ib afferents causing them to depolarize
51
what is a difference between muscle spindles and GTO
with isometric contraction, GTO is activated because muscle tension has increased (despite no change in muscle length)
52
what is the neuronal circuit for the stretch reflex
1) monosynaptic activation of agonist muscle
2) Disynaptic inhibition of the antagonist muscle
53
what is the feedback correction circuit for an increased load
add weight --> Ia afferent from muscle spindle activated by stretch --> alpha motor neuron for agonist muscle act.--> Agonist muscle contracts
54
what is the feedback correction circuit for a decreased load
reduce weight --> Ia afferent less active --> alpha motor neuron for agonist is less active --> agonist muscle relaxed
55
what is alpha gamma coactivation
gamma neurons contract intrafusal fibers in muscle spindles
56
what is the golgi tendon reflex
activation of Ib fibers excites Ib inhibitory interneuron in spinal cord which inhibit the alpha neurons to same muscle causing it to relax
57
what is the withdrawal reflex
Adelta nociceptive afferents:
excite ipsilateral flexor muscle
inhibit ipsilateral extensor muscle
58
what is the crossed extensor reflex
Side with painful stimulus:
extensors inhibited
flexors contract
Other side:
extensors contract
flexors inhibited
59
what are the three parallel striatal cortical loops
motor circuit (motor control)
associative circuit (cognitive function)
limbic circuit (motivated behavior)
60
what are the components of the basal ganglia
striatum (caudate + putamen)
globus pallidus (interna +externa)
subthalamic nucleus
substantia nigra (pars reticulata + pars compacta)
61
what is the function of the striatum
receives excitatory input from cortical regions
sends inhibitory output to globus pallidus
62
what is the function of the caudate
eye and head movments
63
what is the function of the putamen
body movements
64
what is the function of the globus pallidus
receives inhibitory input from the caudate and putamen
sends inhibitory output to the thalamus and subthalamic nucleus
65
what is the function of the substantia nigra
receives inhibitory input from striatum and excitatory input from subthalamic nucleus
located in midbrain
GABAergic output to the thalamus and dopaminergic output to the striatum
66
what is the function of the pars compacta
dopaminergic
67
what is the function of the pars reticulata
GABAergic
68
what is the function of the subthalamic nucleus
receives inhibitory input from GPe
sends excitatory input to GPi
69
what is the function of the thalamus
receives inhibitory input from the GPi
When it is disinhibited, it excites MI for movement
70
what are the regions that send excitatory (glutamatergic) input
cerebral cortex
thalamus
subthalamic nucleus
71
what are the regions that send inhibitory (GABAergic) input
striatum
GPe
GPi
SNr
72
what is the region that sends dopaminergic input to the striatum
SNc
73
Describe Medium spiny neurons in the caudate and putamen
get input from cortical, thalamic, and brainstem structures
inhibit GPi, GPe, or SNr
74
when are medium spiny neurons active
just before a movement starts and just before a movement ends
75
describe striatal neurons
do not fire unless they receive excitatory drive from the cortex
76
describe globus pallidus neurons
- fire at high rates without requiring external drive
- Inhibit thalamus under baseline conditions
- have to be inhibited
77
what are the two types of dopamine receptors in the striatum
D1: excitatory (depolarizing)
D2: inhibitory (hyperpolarizing)
78
what is the effect of dopamine on the direct pathway in healthy individuals
increases disinhibition of the thalamus, which is permissive for movement
79
what is the effect of dopamine in the indirect pathway in healthy individuals
prevents inhibition of the thalamus which is permissive for movement
80
what are the motor symptoms of parkinsons disease
hypokinesia
bradykinesia (slow movements)
Akinesia (lack of movement)
resting hand tremor
81
what is the cause of parkinsons
loss of dopaminergic neurons
82
how is dopamine effected in parkinsons in the direct pathway
loss of DA prevents disinhibition of the thalamus which is not permissive for movement
83
how is dopamine effected in parkinsons in the indirect pathway
increases inhibition of the thalamus, which is not permissive for movement
84
what are the movement symptoms of huntingtons disease
hyperkinesia
largely in limbs
chorea (dance)
85
what are other symptoms of huntingtons
mood changes
impaired cognition
dementia
86
what is the pathology of huntingtons disease
-- loss of GABAergic striatal neurons in the indirect pathway
-- Overactivation of the thalamus
-- Late in HD, overall dopamine tone is also reduced which leads to akinesia
87
what are the functions of the cerebellum
motor planning
comparator
motor learning
88
what do cerebellar lesions cause
uncoordinated movements
impaired balance
inability to change/update motor programs
89
what are the lobes of the cerebellum
anterior
posterior
flocculonodular lobe
90
what are folia
parallel fold running along the outer surface of the cerebellar cortex
91
what are the deep cerebellar nuclei
groups of cell bodies (gray matter) inside the white matter of the cerebellum
-- Receive input from collaterals of axons projecting to the cerebellar cortex
-- output from the cerebellar cortex goes to these nuclei
92
What are the cerebellar peduncles
cerebellum is connected to the brainstem via three of them (superior, middle, inferior)
93
what are the deep cerebellar nuclei
dentate nuclei, interposed nuclei, fastigial nuclei
94
what are the three input/output pathways of the cerebellum
vestibulo-cerebellar
spino-cerebellar
cerebro-cerebellar
95
what is the vestibulo cerebellar pathway
receives input from: CN VIII and vestibular nuclei
Output to Deep nuclei:
- Oculomotor brainstem nuclei
- vestibular nuclei
96
what does damage to the vestibulo cerebellar pathway cause
nystagmus
disturbances of equilibrium
truncal ataxia
97
what is the spino cerebellar pathway (vermis division)
receives input from: proximal musculature
Output to: fastigial nuclei
98
what is the function of the spino cerebellar pathway
error correction during movement of proximal muscles
99
what does damage to the spinocerebellar pathway cause
gait ataxia
dysarthria (slowed/slurred speech)
hypotonia
100
what is the spinocerebellar pathway (intermediate division)
receives input from: distal musculature and motor cortex
output to: interposed nuclei
101
what is the function of the intermediate division of the spino cerebellar pathway
error correction during movement of distal muscles
102
what does damage do to the intermediate division of the spinocerebellar pathway
limb ataxia
dysmetria
intention tremor
hypotonia
103
what is dysmetria
errors in smoothness and direction of targeting movements
104
what is the cerebro-cerebellar pathway
receives input from:
- primary somatosensory cortex
- supplementary and pre motor cortices
- primary motor cortex
- primary visual cortex and parts of the parietal cortex visual areas
Output: dentate nuclei
105
what is the function of the cerebro cerebellar pathway
skilled movements
dexterous movements
complex movements
assists premotor cortical regions in selecting efficient motor programs
106
what does damage to the cerebro cerebellar pathway do
delayed initiation and termination of movement
dysmetria
dysdiadochokinesia
107
what is dysdiadochokinesia
the inability to perform a series of rapid alternating movements
108
what are purkinje cells
inhibitory projection neurons
large, flat dendritic tree
parallel to one another along folia
sole output of cerebellar cortex
109
what are granule cells
excitatory interneurons
innermost layer of cerebellar cortex
axons are the parallel fibers which run along folia
form weak synapses onto purkinje neurons
110
what are golgi cells
cell bodies in granule cell layer
excited by parallel fibers
provide feedback inhibition to granule cells
111
what are basket cells
cell bodies in molecular layer
excited by parallel fibers
provide feedforward inhibition to purkinje cells
112
what are climbing fibers
provide input to: inferior olivary nuclei
Send projection to: purkinje cells and deep cerebellar nuclei
excitatory
113
what are mossy fibers
provide excitatory input from: vestibular nuclei, spinal cord, trigeminal brainstem nuclei, pontine nuclei
send projections to: deep cerebellar nuclei and granule cells
114
what is the function of the cerebellar circuitry
Mossy fiber/parallel fiber inputs:
- weak excitatory synapses
- many together trigger simple spikes in purkinje cells
Climbing fiber inputs:
- strong excitatory synapses
- Trigger complex spikes in purkinje cells
115
what are the layers of the cerebellar cortex
Molecular layer (outermost layer)
Purkinje Cell Layer (middle layer)
Granule Cell Layer (innermost layer)
