Unit 7: 13-14 Somatic Motor System

Question 1

What is the Motor Unit?

Answer 1

Muscles and neurons that control muscles
*Skeletal muscle
*Recruitment- turning on or off more motor units

Question 2

What is the role of the Motor Unit?

Answer 2

generation of coordinated movements

Question 3

What is the Spinal cord in control of in the motor system?

Answer 3

control of coordinated muscle contraction

Question 4

What is the brain in control of in the motor system?

Answer 4

control of motor programs in the spinal cord

Question 5

What is the Basal Ganglia (nuclei) do in the motor system?

Answer 5

initiate and terminate
*Parkinsons disease
*times overshoot or undershoot
*volition

Question 6

What does the Cerebellum in the motor system?

Answer 6

coordinate
*proper fluid movement together

Question 7

What are the 5 main parts of the motor system?

Answer 7

Motor Unit
Spinal cord
Brain
Basal Ganglia (nuclei)
Cerebellum

Question 8

What is the direct motor pathway?

Answer 8

originates in the cerebral cortex.

Question 9

What is the Corticospinal Pathway?

Answer 9

to the limbs and trunk

Question 10

What is the Corticobulbar pathway?

Answer 10

to the head

Question 11

What is the indirect motor pathway?

Answer 11

balance coordination, position
originates in the brain stem
not consciously aware, involuntary
*various mytones of the body

Question 12

What pathways make up the indirect pathway?

Answer 12

Rubrospinal- tone of opposing muscle
Tectospinal- posturel of the head & neck
vestibulospinal- vestibular compensation
reticulospinal- series of midbrain nuclei (sleep to wake position) *sleep walking & paralysis

Question 13

What pathways make up the direct motor pathway?

Answer 13

Corticospinal
Corticobulbar

Question 14

What is Dysmetria?

Answer 14

the inability to control the distance, speed and range of motion necessary to perform smoothly coordinated movements

It can be seen in individuals with cerebellar damage due to brain trauma, brain tumors, metabolic diseases, and demyelinating or degenerative disorders.

Question 15

What is ataxia?

Answer 15

Ataxia means without coordination.

People with ataxia lose muscle control in their arms and legs. This may lead to a lack of balance, coordination, and trouble walking. Ataxia may affect the fingers, hands, arms, legs, body, speech, and even eye movements.

Question 16

What is kinesthesia?

Answer 16

Perception of movement over time
Kinesthetic sensation involves feeling the movement of limbs and joints. Kinesthesia examples include walking without looking at one’s feet, typing without looking at one’s hands, or moving limbs with one’s eyes closed.

Question 17

What are upper motor neurons?

Answer 17

Cell bodies in the cortex or brain stem
*Neural circuits involving BASAL GANGLIA and CEREBELLUM regulate activity of the upper motor neurons

(first-order neurons which are responsible for carrying the electrical impulses that initiate and modulate movement. Various descending UMN tracts are responsible for the coordination of movement. The major UMN tract that initiates voluntary movement is the pyramidal tract.)

Question 18

What somatic pathways are involved in upper motor neurons?

Answer 18

direct pathway
indirect pathway

Question 19

What are lower motor neurons?

Answer 19

Cell bodies in brain stem or spinal cord (SKELETAL MUSCLES)
retrieve info from upper motor neurons
*motor unit- need nerve on muscle fibers

(responsible for transmitting the signal from the upper motor neuron to the effector muscle to perform a movement. There are three broad types of lower motor neurons: somatic motor neurons, special visceral efferent (branchial) motor neurons, and general visceral motor neurons.)

Question 20

What is the lateral cerebrospinal fasciculus?

Answer 20

descussation of pyramids in medulla
*Corticospinal pathway

(The lateral corticospinal tract (LCST) is the largest descending motor pathway in the human body, it spans the entire length of the spinal cord, eventually supplying motor signals to all the skeletal muscles of our upper and lower limbs.)

Question 21

What is the anterior cerebrospinal fasciculus?

Answer 21

decussation in spinal cord
*corticospinal pathway

(The anterior corticospinal tract (also called the ventral corticospinal tract, “Bundle of Turck”, medial corticospinal tract, direct pyramidal tract, or anterior cerebrospinal fasciculus) is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord.)

(The anterior corticospinal tract is an example of a descending motor tract. It comprises of upper motor neurons which helps adjust the posture by controlling the voluntary movements of the axial or truncal body musculature. Within the brain, it runs in close proximity to the lateral corticospinal tract.)

Question 22

What is Hyporeflexia?

Answer 22

Decreased muscle stretch reflex
*Damage to lower motor neuron
*FLACCID PARALYSIS
*same (IPSILATERAL) side
*corticospinal pathway

(Hyporeflexia happens when your skeletal muscles have a decreased or absent reflex response. An absent reflex response is also called areflexia. A reflex is an involuntary (automatic) action your body does in response to something. Reflexes protect your body from things that can harm it.)

Question 23

What is Hyperreflexia?

Answer 23

the presence of hyperactive stretch reflexes of the muscles.
*Damage to upper motor neuron
*SPASTIC PARALYSIS
*opposite (CONTRALATERAL) side
*corticospinal pathway

Question 24

Critical thinking question:

A person suffered a CVA (stroke) and now has
difficulty moving her right arm, and she also has speech problems.
What areas of the brain were damaged by the stroke?

A) Right parietal lobe
B) Left parietal lobe
C) Left frontal lobe
D) Right frontal lobe

Answer 24

C) Left frontal lobe

*Speech: left lateralized
*Right arm: left lateralized
*Frontal lobe: motor, broca’s area arm

Question 25

The Corticobulbar pathways is…

Answer 25

*Descending
*IPSILATERAL vs CONTRALATERAL
*Jaw devastates completely
* Skeletal muscle in the head (nine pairs of cranial nerves)

Question 26

Critical thinking question:

How will a doctor determine whether a patient with facial paralysis is due to lesion to upper motor neuron (stroke) or lower motor neuron (CN VII: facial nerve)? Is it a stroke or facial nerve paralysis (Bell’s palsy)?

Answer 26

*Stroke: paralysis –> bilateral (paralysis in random parts of face)
*Bell’s Palsy: lesions –> no muscles work (Facial nerve CNV II)

(To differentiate between upper motor neuron (UMN) and lower motor neuron (LMN) facial paralysis, doctors may conduct a thorough physical examination and use various diagnostic tests:

1. Physical Examination:
   
   • UMN Signs: If the forehead is spared (due to bilateral UMN innervation), but the lower face is affected, it suggests UMN lesion.
   • LMN Signs: If the entire half of the face is affected, including the forehead (due to unilateral LMN innervation), it suggests LMN lesion.
2. Electromyography (EMG): EMG can help determine the extent and location of nerve damage. In Bell’s palsy (LMN lesion), EMG typically shows decreased nerve conduction.
3. Imaging:
   
   • MRI: Magnetic resonance imaging can help identify structural abnormalities such as tumors or strokes.
   • CT Scan: Computed tomography can also identify structural issues like fractures or tumors but may be less sensitive for strokes.
4. Blood Tests: Blood tests can rule out infections or other systemic conditions that might cause facial paralysis.
5. History and Symptoms: The timing of onset and associated symptoms (such as weakness in other parts of the body) can provide clues. Bell’s palsy often presents with a rapid onset of symptoms and may be associated with a viral illness.

In summary, a combination of physical examination, EMG, and imaging studies can help differentiate between UMN (stroke) and LMN (Bell’s palsy) facial paralysis.)

Question 27

Critical thinking question:

Bell’s Palsy vs Upper Motor Neuron Lesion?

Answer 27

*Stroke: paralysis –> bilateral (paralysis in random parts of face)
*Bell’s Palsy: lesions –> no muscles work (Facial nerve CNV II)

Question 28

*** add questions from objective and summary