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BS IV, Module II > 9. Motor Systems > Flashcards

9. Motor Systems Flashcards

1
Q

Somatomotor function is the activation of ____ muscle fibers (including those of head and neck of pharyngeal arch origin).

Somatomotor function can be characterized based on whether a movement occurs ____ or ____ – typically, movements are combinations of both.

All necessary interconnections in the CNS for such somatomotor function share a common final segment – terminating in a ____ located in either ____ or ____

A 
skeletal
automatically
deliberately
LMN
brainstem
spinal cord
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2
Q

Voluntary contraction of skeletal muscle requires the interaction of 2 neurons:
• an ____ and
• a ____

  • Recall that the ____ motor neuron causes muscle contractions which generate movement, whereas the ____ motor neuron, independent of concrete movement, regulates normal muscle tone.
A

UMN
LMN
alpha
gamma

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3
Q

Upper Motor Neurons in ____ (primary motor cortex)

Descending axons forming the cortical output from M1 arise from the ____ in cortical layer ____

A

M1
pyramidal cells
5

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4
Q

Upper motor neurons
Responsible for:
• the initiation of ____ movement
• the maintenance of muscle ____ for support of the body against gravity
• the regulation of ____ to provide a stable background upon which to initiate voluntary activity

A

voluntary
tone
posture

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5
Q

In the spinal cord, cell bodies of two 2 sets of LMNs are found in ____ of the ventral horn of the spinal cord:
• Alpha motor neurons innervate ____ fibers in skeletal muscle at neuromuscular junctions.
• Gamma motor neurons innervate ____ fibers (muscle spindles) in skeletal muscle.

Alpha (and gamma) LMNs in the cord always lie on the ____ side of the midline of the skeletal muscles innervated by their axons

A

lamina IX
extrafusal
intrafusal
same

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6
Q

Let’s examine somatic spinal and brainstem reflexes and the involuntary contraction of skeletal muscle

A ____ is any response that occurs automatically without conscious effort.

The neural pathway involved in accomplishing reflex activity is known as a reflex arc, which typically includes five basic components:

  1. ____
  2. Afferent pathway
  3. ____
  4. Efferent pathway
  5. ____
A

reflex
sensory receptor
integrating center
efferent organ

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7
Q

Very simple (involuntary) motor processes such as reflexes may be executed directly in the ____ (spinal reflex) or ____ without involvement of ____ in higher centers of the CNS

The simplest of these involuntary processes is the ____

A

spinal cord
brainstem
UMN
monosynaptic stretch reflex

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8
Q

Monosynaptic Reflexes
• An afferent neuron originating at a stretch-detecting receptor in skeletal muscle terminates directly on an efferent neuron innervating the same skeletal muscle - causing ____ to counteract the stretch

• The integrating center is the ____ synapse within spinal cord or brainstem between the afferent and efferent pathways. The output of this system (whether or not the muscle contracts in response to passive stretch) depends on the extent of ____ of EPSPs at the cell body of the efferent neuron.

  • Stretch reflex is a ____ (“one synapse”) reflex because the only synapse in the reflex arc is the one between the ____ neuron and the ____ neuron and serves as the integrating center.
  • All other somatic reflexes are ____
A 
contraction
single
summation
monosynaptic
afferent
efferent
polysynaptic
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9
Q

MONOSYNAPTIC REFLEX ARC

Changes in muscle stretch
• Activates an ____ muscle spindle fiber, that…
• Inputs to a ____ afferent neuron in a DRG that…
• Excites an ____ motor neuron in the ____ horn of the same cord segment that…
• Produces muscle contraction

A

intrafusal
proprioceptive
alpha
ventral

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10
Q

Deep Tendon
Reflexes (DTRs)
in both upper and
lower extremities employ ____ reflex arcs to assess both afferent and efferent pathway components

As each DTR involves specific spinal cord segments, an abnormal reflex can help localize a lesion to a specific levels of the cord.

* \_\_\_\_
* Quadriceps
* \_\_\_\_ reflex

DTR GRADING!

A

monosynaptic
patellar
knee jerk

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11
Q

Quadriceps
tendon reflex: ____

Calcaneal (Achilles) tendon reflex: ____

Biceps tendon reflex: ____

Triceps tendon reflex: ____

A

L3/L4
S1/S2
C5/C6
C6/C7

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12
Q

Review:
How does a muscle contract reflexively?

Reflex contraction of skeletal muscle requires:
• ____
• ____ neuron
• ____

Stimulus: Muscle ____

But note: UMNs have a net ____ effect on such reflexes act like “brakes”

A 
muscle
sensory
LMN
stretch
inhibitory
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13
Q

Recall the Jaw Jerk reflex

NOTES!

A

YA

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14
Q

LMN Lesion:
• Suppressed deep tendon reflexes (____)
• Muscle tone ____
• Muscle ____
• Ipsilateral____ as muscle is limp and unable to contract
• Spontaneous ____

The symptoms of ____ results from a loss of LMNs in the ventral horn caused by poliovirus

A 
hyporeflexia
decreased
atrophy
flaccid paralysis
fasciculation

poliomyelitis

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15
Q

UMN Lesion:

• Elevated muscle stretch reflexes (____)

A

hyperreflexia

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16
Q

POLYSYNAPTIC REFLEX ARC

Noxious cutaneous stimulus

Information from cutaneous receptors act via ____ to excite ____ motor neurons and stimulate muscle contraction

A

interneurons

alpha

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17
Q

A classic polysynaptic spinal reflex is the ____ intended to protect the body from painful, damaging stimuli

Stimulation of ____ and ____ induces rapid contraction of ____ muscles to withdraw the body part in under .5 seconds

A

withdrawal reflex
thermoreceptors
nociceptors
flexor

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18
Q

How does a muscle contract voluntarily?

Voluntary contraction
of skeletal muscle requires two neurons: ____ + ____

UMN cell body is ____ to the LMN

The UMN axon must cross the ____ as it descends from the brain to the LMN

LMN is ____ to the innervated muscle

A 
UMN
LMN
contralateral
midline
ipsilateral
19
Q

The pyramidal system originates in ____ cortex and controls ____ movement (voluntary motor activity)
It is the most important pathway for ____ motor function!

All three components
• \_\_\_\_
• Corticonuclear (Corticobulbar)
• \_\_\_\_
pass through the \_\_\_\_ from the telencephalon, continuing to brainstem or spinal cord.

Corticonuclear fibers are distributed to to the motor nuclei of the ____

Corticospinal fibers descend to pyramids of the ____ and below

Corticoreticular fibers terminate in the diffusely distributed ____ of the brainstem and are involved in postural control and locomotor function.

A

motor
conscious
voluntary

corticospinal
corticoreticular
internal capsule

cranial nerves
caudal medulla

reticular formation

20
Q

Primary motor cortex in the precentral gyrus (M1) is also known as ____ (based on cytoarchitectonic studies).

Its upper motor neurons encode for the ____, force, and velocity of a movement, and control individual muscles used in the execution of ____, deliberate movements.

As you will recall,
the primary motor cortex is arranged ____…

A

brodmann’s area 4
direction
skilled
somatotopically

21
Q

The precentral gyrus contains a ____, which is a distorted orderly map of the skeletal muscles controlled by upper motor neurons in the ____ limbs and trunk.

In the homunculus, upper motor neurons that control cranial nerve-innervated muscles are represented close to the ____.

____-innervated musculature and muscles of the ____ are most heavily represented in the homunculus.

Proceeding ____ on the lateral aspect of the hemisphere are upper motor neurons that control neck, upper limb, and trunk muscles.

On the ____ aspect of the hemisphere is an extension of the primary motor cortex containing upper motor neurons that control pelvic and lower limb muscles.

A

motor homunculus
contralateral

lateral sulcus

cranial nerve
hands

dorsally

medial

22
Q

BUT muscle contractions induced by ____ in M1 are only a small aspect of complex movement - other cortical regions, such as ____, are involved in and help coordinate such motor activity…

In fact, of the roughly 1 million fibers in the corticospinal tract, only ____ arise from primary motor cortex:
____ arise from premotor cortex and ____ from the parietal lobe

A 
UMNs
premotor cortex
30%
30%
40%
23
Q

Descending pathways convey the axons of these upper motor neurons directly to lower motor neurons via the ____, Corticoreticular and ____ tracts

A

corticospinal

corticonuclear (corticobulbar)

24
Q

In the pyramidal system, axons leaving the cerebral cortex begin their descent toward the
brainstem by way of the
____
They then converge and descend through the ____ limb of the ____

A

corona radiata
posterior
internal capsule

25
Q

These fibers in the
POSTERIOR LIMB of the internal capsule are also arranged ____

The internal capsule is a common
site of ischemic ____ lesions resulting
from interruption of penetrating arteries supplying deep structures

The most common type of stroke - associated with elevated ____

A

somatotopically
lacunar stroke
blood pressure - hypertension

26
Q

Corticospinal fibers are shown as red dots in the posterior limb of the capsule

If blood flow to the internal capsule is interrupted by a ____, these descending fibers undergo irreversible damage producing:

  • Contralateral ____
  • ____ and dysphagia may also result
A

lacunar stroke
hemiparesis/hemiplegia
dysarthria

27
Q

In the pyramidal system, axons leaving the cerebral cortex begin their descent toward the
brainstem by way of the
CORONA RADIATA

They then converge and descend through the POSTERIOR LIMB
of the
INTERNAL CAPSULE

These axons then pass through and contribute to formation of the ____ to reach the brainstem

A

cerebral peduncle

28
Q

Axons of the pyramidal tract continue their descent through the ____, pons and ____ of the brainstem

The corticonuclear (corticobulbar) fibers terminate in the ____ motor nuclei providing direct control of the ____ in these nuclei

A

midbrain
medlla
cranial nerve
LMN

29
Q

Corticobulbar innervation of most cranial nerve lower motor neurons is predominantly ____!

A

bilateral

30
Q 
CORTICOBULBAR (Corticonuclear) fibers arise from cortical
upper motor neurons
and synapse with
lower motor neurons
in the following nuclei:
	• \_\_\_\_ nucleus
	• Facial motor nucleus
	• \_\_\_\_
	• Hypoglossal nucleus
	• \_\_\_\_ nucleus

Lower motor neurons in each masticator nucleus and nucleus ambiguus are innervated by axons
Descending from ____ in both ____ and ____ hemispheres

Lower motor neurons
in each hypoglossal and accessory nucleus are innervated by axons
Descending from ____ in the ____ hemispheres

A

trigeminal
nucleus ambiguus
accessory

UMN
left
right

UMN
contralateral

31
Q

CORTICOBULBAR innervation of the facial motor nucleus is
• ____ for certain LMNs
• ____ for other LMNs

A

bilateral

contralateral

32
Q

Corticobulbar innervation of the facial motor nucleus
Is BILATERAL for certain lower motor neurons
and CONTRALATERAL for others

Corticobulbar innervation is ____ to lower motor neurons that innervate muscles of the upper face

Corticobulbar innervation is exclusively ____ to lower motor neurons that innervate muscles of the lower face …including muscles that act as ____ and ____ of the nostrils and mouth

A

bilateral
contralateral
sphincters
dilators

33
Q

CORTICOBULBAR innervation of the facial motor nucleus is bilateral for certain lower motor neurons and contralateral for others…

Corticobulbar innervation is BILATERAL to LMNs
that innervate muscles of the ____ face, most notably
• ____ which wrinkles the skin of the forehead
• ____ which “closes” the eye

Corticobulbar innervation is exclusively CONTRALATERAL to LMNs that innervate muscles of the ____ face…
including those that act as ____ and ____ of the nostrils and mouth.

A

upper
frontalis
orbicularis oculi

lower
sphincters
dilators

34
Q

In contrast to the ipsilateral
deficits in BOTH upper and lower face seen in LMN lesions/Bell’s palsy…

A patient with an
UMN lesion demonstrates:
____ of facial muscles in the ____ upper quadrant and complete ____ of muscles in the ____ lower quadrant

Classic examples of such CN VII UMN lesions include:
• Tumor or stroke in the ____
• Lacunar stroke in the ____

A

weakness
contralateral
paralysis
contralateral

precentral gyrus
internal capsule

35
Q

Lesions of the Facial Nerve (CN VII) vs. lesions of Corticobulbar fibers to the Facial Motor Nucleus
In patients with facial weakness, one may be able to differentiate between a lesion of CN VII and a lesion of the corticobulbar fibers
to the facial motor nucleus.

Patients with a facial nerve lesion (as in Bell’s palsy) may have a complete paralysis of muscles of facial expression ____ to the side of the lesioned nerve with an ____ to wrinkle the forehead, shut the eye and flare a nostril, and with a drooping of the corner of the mouth.

A unilateral corticobulbar lesion may result in ____ face paralysis only, as evidenced by
a drooping of the corner of the mouth on the side of the face ____ to the lesioned corticobulbar fibers. These patients ____ be able to wrinkle their forehead and shut their eyes and ____ have an intact blink reflex.

A

ipsilateral
inability

lower
contralateral
will
will

36
Q

Corticobulbar fibers
also synapse
with interneurons in ____ in the midbrain and pons that project to the oculomotor, trochlear, and abducens nuclei via the ____

____ connects these nuclei
and integrates movements directed by the gaze centers (frontal eye fields) with inputs concerning head movement from CN ____. MLF is an integral component of the ____ discussed previously

A

conjugate gaze centers
medial longitudinal fasciculus

MLF
VIII
vestibulo-ocular reflex (VOR)

37
Q 
So to summarize..
 As a rule,
UMN innervation to LMN in
spinal nerves
is \_\_\_\_

UMN innervation to LMNs in cranial nerves is ____!*

A

contralateral

bilateral

38
Q

Corticospinal tract fibers form the ____

on the ventral aspect of the medulla oblongata

A

pyramids

39
Q

Corticospinal fibers descend to the decussation of the pyramids in the ____, where ____ of the fibers cross the midline

The remaining 10- 20%
continue to descend ____ to the spinal cord

A

caudal medulla
80-90%
ipsilaterally

40
Q

The fibers that decussate here enter the lateral funiculus of spinal cord form the ____

The lateral corticospinal tract has a ____ organization (cervical cord fibers ____;
sacral cord fibers ____)

The fibers that continue to descend ipsilaterally form the ____ TRACT and cross at the appropriate segmental level to terminate on the same ____
as the lateral corticospinal tract.

A

lateral corticospinal tract
somatotopic
medial
lateral

anterior corticospinal
LMNs

41
Q

Corticospinal fibers terminate on LMNs in the nuclei of the ventral horn of the spinal cord, either directly or indirectly through ____.

LMNs in lamina IX that innervate axial (proximal) muscles are ____ to motor neurons that innervate more distal muscles in the limbs.

LMNs in lamina IX that innervate flexor muscles are ____ to motor neurons that innervate extensor muscles.

A

interneurons
medial
dorsal

42
Q

Note: direct innervation of alpha motor neurons by ____ axons is mainly to ____ muscles and is associated with the ability to execute ____, precise movements

A

pyramidal tract
distal
fine

43
Q

Note that ____ lesions or interruptions of the ____ produce immediate
loss or reduction
of voluntary function in ____ muscles corresponding to the region of injury and spastic paralysis

But…
frequently there is some ____ of function
with time

A

primary motor cortex
corticospinal tract
contralateral
recovery

44
Q

Recall that
UMN have a net ____ effect on reflexes

UMN Lesion:
	• \_\_\_\_ or paresis
	• Hyperreflexia
	• Altered \_\_\_\_ reflexes (i.e. \_\_\_\_ and \_\_\_\_)
	• Disuse atrophy
	• \_\_\_\_
LMN Lesion:
	• Suppressed \_\_\_\_
	• Muscle atrophy
	• \_\_\_\_
	• Spontaneous fasciculation
A

inhibitory

spastic paralysis
cutaneous
cremasteric
babinski
clonus

reflexes
ipsilateral flaccid paralysis

BS IV, Module II (9 decks)

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