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Functional Neuroanatomy > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

What are reflexes

A

rapid, stereotyped, involuntary

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2
Q

what are rhythmic motor patterns

A

voluntarily initiated and terminated
maintained through reflexes and central pattern generators
Ex. breathing, walking, running

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3
Q

what are voluntary movements

A

purposeful
learned
ex. Typing, piano

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4
Q

How do muscles work

A

muscles pull on bones to move them at joints; muscles CANNOT push on bones

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5
Q

what are flexors

A

decrease joint angle

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6
Q

what are extensors

A

increase joint angle

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7
Q

what are agonist muscles

A

main muscles that move bones

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8
Q

what are antagonist muscles

A

muscles that decelerate movement by agonist muscles and move limbs in opposing directions

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9
Q

what are axial muscles

A

move the trunk and maintain posture

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10
Q

what are proximal muscles

A

close to the trunk
control the shoulder, elbow, pelvis, and knee joint
critical for posture and locomotion

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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

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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

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13
Q

what is the lateral part of the ventral horn

A

motor neurons that control distal muscles
involved in fine manipulation

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14
Q

what is the dorsal part of the ventral horn

A

flexor muscles

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15
Q

what is the ventral part of the ventral horn

A

extensor muscles

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16
Q

what is a motor unit

A

one motor neuron and all the muscle fibers it innervates

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17
Q

what is paresis

A

partial paralysis

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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

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19
Q

what are upper motor neurons

A

cells bodies in the neocortex or brainstem nuclei
affect muscles indirectly

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20
Q

what are lower motor neurons

A

cell bodies in spinal cord or cranial nerve nuclei
directly contract muscles

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21
Q

what is the corticospinal tract

A

mainly involved in conscious control of movement

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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

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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

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24
Q

what is the pathway of the corticospinal tract

A

neocortex –> corona radiata –> internal capsule –> cerebral peduncle –> pons –> pyramids –> spinal cord

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25
Q

what is the corona radiata

A

descending axons from cortical neurons

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26
Q

what is the internal capsule

A

descending UMN axons in the corona radiata come together and mostly travel in the posterior limb of the i.c

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27
Q

where do axons of the corticospinal tract decussate

A

lower medulla (pyramidal decussation)

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28
Q

what is the lateral corticospinal tract

A

axons decussate in lower medulla
innvervates neurons that control distal muscles
synapse in ventral horn

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29
Q

what is the anterior corticospinal tract

A

axons decussate in the spinal cord near the level where they terminate
innervates neurons that control axial and proximal muscles

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30
Q

what is the corticobulbar tract

A

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

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31
Q

what is lower motor syndrome

A

caused by damage to lower motor neurons
characterized by:
weakness, paralysis
hypotonia
muscle atrophy
hyporeflexia

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32
Q

what is upper motor neuron syndrome

A

characterized by:
muscle weakness
hypertonia
no muscle atrophy
hyperreflexia

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33
Q

what are renshaw cells

A

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

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34
Q

what is tetanus

A

painful muscle spasms and rigidity
blocks release of glycine from renshaw cells

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35
Q

what is the medial pathway

A

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

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36
Q

what are the main tracts of the medial pathway

A

tectospinal, vestibulospinal, reticulospinal

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37
Q

what is the tectospinal pathway

A

originates in the tectum which orients reflexes
tectum receives visual, auditory, somatosensory input
innervates interneurons that control neck motor neurons and coarse eye movements

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38
Q

what is the vestibulospinal tract

A

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

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39
Q

what is the reticulospinal tract

A

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)

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40
Q

what are the types of proprioceptors

A

muscles spindles
golgi tendon organs

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41
Q

what are muscle spindles

A

maintain muscle length

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42
Q

what are golgi tendon organs

A

maintain muscle tension

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43
Q

what are the sensory neuron fibers

A

Ia sensory afferents (MS)
II sensory afferents (MS)
Ib sensory afferents (GTO)

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44
Q

what are the motor neuron fibers

A

alpha (to skeletal muscle)
gamma (to muscle spindles)

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45
Q

where are muscle spindles located

A

embedded in skeletal muscles
run parallel with extrafusal fibers

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46
Q

what are the phases of muscle stretch

A

static (constant length)
dynamic (muscle length is changing)

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47
Q

describe Ia afferents

A

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
Q

describe II afferents

A

slowly adapting
firing rate during static phases is proportional to amount of stretch
senses amount of muscle stretch during static phases

49
Q

where is the golgi tendon organ located

A

capsule containing collagen fibers
attached to muscle on one end and to a tendon on the other
in series with extrafusal muscle fibers

50
Q

Describe how golgi tendon organs sense muscle tension

A

Tension on the GTO compresses the branches of the Ib afferents causing them to depolarize

51
Q

what is a difference between muscle spindles and GTO

A

with isometric contraction, GTO is activated because muscle tension has increased (despite no change in muscle length)

52
Q

what is the neuronal circuit for the stretch reflex

A

1) monosynaptic activation of agonist muscle
2) Disynaptic inhibition of the antagonist muscle

53
Q

what is the feedback correction circuit for an increased load

A

add weight –> Ia afferent from muscle spindle activated by stretch –> alpha motor neuron for agonist muscle act.–> Agonist muscle contracts

54
Q

what is the feedback correction circuit for a decreased load

A

reduce weight –> Ia afferent less active –> alpha motor neuron for agonist is less active –> agonist muscle relaxed

55
Q

what is alpha gamma coactivation

A

gamma neurons contract intrafusal fibers in muscle spindles

56
Q

what is the golgi tendon reflex

A

activation of Ib fibers excites Ib inhibitory interneuron in spinal cord which inhibit the alpha neurons to same muscle causing it to relax

57
Q

what is the withdrawal reflex

A

Adelta nociceptive afferents:
excite ipsilateral flexor muscle
inhibit ipsilateral extensor muscle

58
Q

what is the crossed extensor reflex

A

Side with painful stimulus:
extensors inhibited
flexors contract
Other side:
extensors contract
flexors inhibited

59
Q

what are the three parallel striatal cortical loops

A

motor circuit (motor control)
associative circuit (cognitive function)
limbic circuit (motivated behavior)

60
Q

what are the components of the basal ganglia

A

striatum (caudate + putamen)
globus pallidus (interna +externa)
subthalamic nucleus
substantia nigra (pars reticulata + pars compacta)

61
Q

what is the function of the striatum

A

receives excitatory input from cortical regions
sends inhibitory output to globus pallidus

62
Q

what is the function of the caudate

A

eye and head movments

63
Q

what is the function of the putamen

A

body movements

64
Q

what is the function of the globus pallidus

A

receives inhibitory input from the caudate and putamen
sends inhibitory output to the thalamus and subthalamic nucleus

65
Q

what is the function of the substantia nigra

A

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
Q

what is the function of the pars compacta

A

dopaminergic

67
Q

what is the function of the pars reticulata

A

GABAergic

68
Q

what is the function of the subthalamic nucleus

A

receives inhibitory input from GPe
sends excitatory input to GPi

69
Q

what is the function of the thalamus

A

receives inhibitory input from the GPi
When it is disinhibited, it excites MI for movement

70
Q

what are the regions that send excitatory (glutamatergic) input

A

cerebral cortex
thalamus
subthalamic nucleus

71
Q

what are the regions that send inhibitory (GABAergic) input

A

striatum
GPe
GPi
SNr

72
Q

what is the region that sends dopaminergic input to the striatum

A

SNc

73
Q

Describe Medium spiny neurons in the caudate and putamen

A

get input from cortical, thalamic, and brainstem structures
inhibit GPi, GPe, or SNr

74
Q

when are medium spiny neurons active

A

just before a movement starts and just before a movement ends

75
Q

describe striatal neurons

A

do not fire unless they receive excitatory drive from the cortex

76
Q

describe globus pallidus neurons

A
  • fire at high rates without requiring external drive
  • Inhibit thalamus under baseline conditions
  • have to be inhibited
77
Q

what are the two types of dopamine receptors in the striatum

A

D1: excitatory (depolarizing)
D2: inhibitory (hyperpolarizing)

78
Q

what is the effect of dopamine on the direct pathway in healthy individuals

A

increases disinhibition of the thalamus, which is permissive for movement

79
Q

what is the effect of dopamine in the indirect pathway in healthy individuals

A

prevents inhibition of the thalamus which is permissive for movement

80
Q

what are the motor symptoms of parkinsons disease

A

hypokinesia
bradykinesia (slow movements)
Akinesia (lack of movement)
resting hand tremor

81
Q

what is the cause of parkinsons

A

loss of dopaminergic neurons

82
Q

how is dopamine effected in parkinsons in the direct pathway

A

loss of DA prevents disinhibition of the thalamus which is not permissive for movement

83
Q

how is dopamine effected in parkinsons in the indirect pathway

A

increases inhibition of the thalamus, which is not permissive for movement

84
Q

what are the movement symptoms of huntingtons disease

A

hyperkinesia
largely in limbs
chorea (dance)

85
Q

what are other symptoms of huntingtons

A

mood changes
impaired cognition
dementia

86
Q

what is the pathology of huntingtons disease

A

– 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
Q

what are the functions of the cerebellum

A

motor planning
comparator
motor learning

88
Q

what do cerebellar lesions cause

A

uncoordinated movements
impaired balance
inability to change/update motor programs

89
Q

what are the lobes of the cerebellum

A

anterior
posterior
flocculonodular lobe

90
Q

what are folia

A

parallel fold running along the outer surface of the cerebellar cortex

91
Q

what are the deep cerebellar nuclei

A

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
Q

What are the cerebellar peduncles

A

cerebellum is connected to the brainstem via three of them (superior, middle, inferior)

93
Q

what are the deep cerebellar nuclei

A

dentate nuclei, interposed nuclei, fastigial nuclei

94
Q

what are the three input/output pathways of the cerebellum

A

vestibulo-cerebellar
spino-cerebellar
cerebro-cerebellar

95
Q

what is the vestibulo cerebellar pathway

A

receives input from: CN VIII and vestibular nuclei
Output to Deep nuclei:
- Oculomotor brainstem nuclei
- vestibular nuclei

96
Q

what does damage to the vestibulo cerebellar pathway cause

A

nystagmus
disturbances of equilibrium
truncal ataxia

97
Q

what is the spino cerebellar pathway (vermis division)

A

receives input from: proximal musculature
Output to: fastigial nuclei

98
Q

what is the function of the spino cerebellar pathway

A

error correction during movement of proximal muscles

99
Q

what does damage to the spinocerebellar pathway cause

A

gait ataxia
dysarthria (slowed/slurred speech)
hypotonia

100
Q

what is the spinocerebellar pathway (intermediate division)

A

receives input from: distal musculature and motor cortex
output to: interposed nuclei

101
Q

what is the function of the intermediate division of the spino cerebellar pathway

A

error correction during movement of distal muscles

102
Q

what does damage do to the intermediate division of the spinocerebellar pathway

A

limb ataxia
dysmetria
intention tremor
hypotonia

103
Q

what is dysmetria

A

errors in smoothness and direction of targeting movements

104
Q

what is the cerebro-cerebellar pathway

A

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
Q

what is the function of the cerebro cerebellar pathway

A

skilled movements
dexterous movements
complex movements
assists premotor cortical regions in selecting efficient motor programs

106
Q

what does damage to the cerebro cerebellar pathway do

A

delayed initiation and termination of movement
dysmetria
dysdiadochokinesia

107
Q

what is dysdiadochokinesia

A

the inability to perform a series of rapid alternating movements

108
Q

what are purkinje cells

A

inhibitory projection neurons
large, flat dendritic tree
parallel to one another along folia
sole output of cerebellar cortex

109
Q

what are granule cells

A

excitatory interneurons
innermost layer of cerebellar cortex
axons are the parallel fibers which run along folia
form weak synapses onto purkinje neurons

110
Q

what are golgi cells

A

cell bodies in granule cell layer
excited by parallel fibers
provide feedback inhibition to granule cells

111
Q

what are basket cells

A

cell bodies in molecular layer
excited by parallel fibers
provide feedforward inhibition to purkinje cells

112
Q

what are climbing fibers

A

provide input to: inferior olivary nuclei
Send projection to: purkinje cells and deep cerebellar nuclei
excitatory

113
Q

what are mossy fibers

A

provide excitatory input from: vestibular nuclei, spinal cord, trigeminal brainstem nuclei, pontine nuclei
send projections to: deep cerebellar nuclei and granule cells

114
Q

what is the function of the cerebellar circuitry

A

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
Q

what are the layers of the cerebellar cortex

A

Molecular layer (outermost layer)
Purkinje Cell Layer (middle layer)
Granule Cell Layer (innermost layer)

Functional Neuroanatomy (12 decks)

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