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PTH9111 > Lecture 13 - Descending Tracts > Flashcards

Lecture 13 - Descending Tracts Flashcards

1
Q

Name the 4 descending pathways

A
  1. Corticospinal (Pyramidal) tract
  2. Corticoreticulospinal tract
  3. Corticorubrospinal tract
  4. Vestibulospinal tract
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2
Q

Function of corticospinal tract

A

Skilled movement of limbs

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3
Q

3 functions of corticoreticulospinal tract

A
  1. Posture
  2. Locomotion
  3. Autonomic functions (respiration, shivering, sweating, circulation, etc)
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4
Q

Function of the corticorubrospinal tract

A

Similar to corticospinal so skilled movements of limbs

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5
Q

2 functions of vestibulospinal tract

A

1.Postural reactions
2. Standing balance

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6
Q

[blank] and [blank] feed input to the brain to regulate descending systems

A

Basal ganglia and cerebellum

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7
Q

What 4 areas of the brain are important for planning movements and what area are they found in?

A

They are found in area 4 (primary motor cortex):
1. Somatosensory Cortex
2. Prefrontal cortex
3. Premotor cortex
4. Supplementary motor cortex

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8
Q

Where is area 4/primary motor cortex of the brain located

A

Precentral gyrus and paracentral lobule of frontal lobe

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9
Q

What is another name for area 4

A

Primary motor cortex

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10
Q

T or F: The left strip of the primary motor cortex controls the left side, and the right controls the right side

A

F, left controls right and right controls left

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11
Q

What 2 somatosensory tracts feed into the primary motor cortex/area 4?

A
  1. Spinothalamic tract
  2. Dorsal-column medial lemniscus
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12
Q

What is area 6 also called

A

Motor Associations Area

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13
Q

What 2 areas comprise the motor associations area/area 6?

A
  1. Premotor Area
  2. Supplementary Area
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14
Q

Function of the premotor area

A

Input is primarily visual and neuronal activity is triggered by external events

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15
Q

Is the premotor area lateral or medial

A

Lateral

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16
Q

Function of the supplementary motor area

A

Input is primarily somatosensory and its neuronal activity is triggered by internal representations

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17
Q

What does internal representations of the supplementary motor area mean

A

It is memorized sequences or manual tasks/procedures that we do often

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18
Q

What two methods were used to discover somatotopic organization and explain how

A
  1. Electrical stimulation
  2. Transcranial Magnetic Stimulation

How: Stimulate certain areas of brain to see what body part reacted

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19
Q

Which parts of the body are represented more medial in the motor cortex

A

lower extremities

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20
Q

Which parts of the body are represented more lateral in the motor cortex

A

Face

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21
Q

Somatotopy

A

How the brain is organized (Where each body part is found in the brain)

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22
Q

Describe what is meant by movement vectors of neurons

A

Neurons are specialized to move in a particular direction (ex. movement in flexion or extension)

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23
Q

Homunculus

A

How much of the brain is dedicated to each body part

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24
Q

Explain what is meant by larger areas of a homonculus

A

These areas are larger because they are dedicated to fine motor control

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25
Q

What two neurons make up descending pathways

A
  1. Upper motor neuron
  2. Lower motor neuron
26
Q

T or F: The upper motor neuron regulates the lower motor neuron

A

T

27
Q

What would happen if there was a lesion to the upper motor neuron

A

The lower motor neuron would be unregulated resulting in spasticity or paralysis

28
Q

Where are cell bodies of lower motor neurons found

A

Ventral horn of spinal cord

29
Q

Where do lower motor neurons innervate

A

Muscle fibers

30
Q

Dorsal and ventral roots fuse to form a

A

spinal nerve

31
Q

Why do we have cervical and lumbar enlargements

A

Where innervation of nerves from upper and lower extremities is found

32
Q

Axial muscles are closer or farther from spine

A

closer

33
Q

Flexor muscles are closer or farther form spine

A

farther

34
Q

The origin of the corticospinal tract is

A

The sensorimotor cortex

35
Q

What 3 areas of the brain make up the sensorimotor cortex

A
  1. Primary motor cortex
  2. Supplementary Motor Area
  3. Parietal Lobe
36
Q

Describe the path of the corticospinal tract

A

1.Passes through the corono radiata/internal capsule
2. Through the base of the cerebral peduncle in midbrain
3. Enters basilar portion of pons
4. Forms a medullar pyramid as it enters the medulla
5. Decussation of pyramids occurs at the caudal medulla
6. 90% form lateral corticospinal tract while the rest remains uncrossed and is called the ventral corticospinal tract

37
Q

Does the lateral or ventral corticospinal tract stay ipsilateral

A

ventral

38
Q

Another name for the lateral corticospinal tract

A

Lateral funiculus

39
Q

The lateral corticospinal tract synapse on

A

Lower motor neurons and motor neurons that innervate distal extremities (hands, feet)

40
Q

Where does the lateral corticospinal tract terminate and why

A

Ventral, intermediate, and dorsal horn

Why: To modulate multiple things like reflexes and responses, allowing movement to occur

40
Q

What do corticospinal tracts that synapse on interneurons in the dorsal horn influence

A

Local reflex arcs

41
Q

What happens if the corticospinal tract was damaged in terms of reflexes

A

Spasticity and increased muscle tone

42
Q

What would happen if the corticospinal tract was damaged in terms of skilled, voluntary movements

A
  1. Cant use tools
  2. Play competitive sports
  3. Loss of hand and finger movements
  4. Reaching
  5. Loss of regulation of reflex
43
Q

Why does some of the corticospinal tract not decussate

A

Redundancy to ensure movement occurs still if there is damage

44
Q

Pathway of the corticorubrospinal tract

A
  1. Same cortical areas as cortico spinal but also the cerebellum (corona radiata)
  2. Projects to ipsilateral red nucleus of midbrain
  3. Decussates in pons
  4. Projects to ventral horns
45
Q

Does the corticospinal or corticorubrospinal tract decussate higher up

A

corticorubrospinal tract

46
Q

What does the corticorubrospinal tract control

A
  1. Extrinsic muscles of hand, wrist, elbow and shoulder
  2. Muscles at multiple joints
47
Q

What is the role of corticorubrospinal tract

A

Reaching and coordinated action of hand/arm positioning during task

48
Q

Pathway of the corticoreticulospinal tract

A
  1. Starts at reticular formation which receives sensory info and links cerebellum and limbic system
  2. Corticoreticular fibers terminate bilaterally in the brain stem and form the pontine(medial) reticulospinal tract and the medullary (lateral) reticulospinal tract
49
Q

Function of the pontine (medial) reticulospinal tract (4)

A
  1. Influences posture
  2. Locomotion
  3. Gross limb movements
  4. rapid postural reactions
50
Q

Does the pontine (medial) reticulospinal tract have larger or smaller axons than medullary (lateral) spinal tract

A

larger axons

51
Q

Function of the medullary (lateral) reticulospinal tract (2)

A
  1. Autonomic functions
  2. Involved in spinal central pattern generator for locomotion
52
Q

Does the reticulospinal tract display redundancy?

A

Yes

53
Q

Pathway of vestibulospinal tract

A
  1. Originates in vestibular nuclei of medulla
  2. Projects down spinal cord to neck and lumbar levels by forming the medial and lateral vestibulospinal tracts
54
Q

Function of the medial vestibulospinal tract

A

Head movements

55
Q

Function of the lateral vestibulospinal tract

A

Postural reactions

56
Q

Refresher card to go over spinal cord schematic pathways

A
57
Q

Name 3 ways a lesion could occur to the corticospinal tract

A
  1. Vascular damage
  2. Trauma
  3. Demyelinating diseases
58
Q

What happens if a lesion occurs above decussation

A

Symptoms detected of opposite side of lesion

59
Q

What happens if lesion is below decussation

A

Symptoms detected on same side of lesion

60
Q

What are 3 characteristic signs of upper motor neuron lesions (corticospinal tract)

A
  1. Spastic paralysis: No input to reflex arc
  2. Clonus: Beat movement that is repeated (uncontrolled reflex)
  3. Babinski sign: Toes fan or flare (flare = positive result, curl = negative result)
61
Q

What happens if there is a lesion to the corticospinal tract in the left capsular region?

A

There will be a right side spastic hemiplegia (paralysis on one side) and hypertonia because lesion is above decussation

PTH9111 (15 decks)

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