Postural control and locomotion Flashcards Preview

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Flashcards in Postural control and locomotion Deck (57):
1

Motor neurons innervating axial and proximal muscles are in the medial or lateral part of the anterior horn of the spine?

Medial

2

Motor neurons innervating distal muscles are in the lateral or medial part of the anterior horn of the spine?

Lateral

3

What is the function of the lateral corticospinal tract?

Voluntary control of the flexors of the hands and digits

4

What is the function of the rubrospinal tract?

Recall this is the ape one--flexion of the hands and the digits

5

What is the function of the ventromedial pathway?

Posture and locomotion via axial extensor muscle excitation

6

What is the origin, route, and termination of the lateral vestibulospinal tract?

Origin = vestibular nuclei
Route = all spinal cord
Terminates on extensor and flexor muscles of the limbs and girdle

7

What is the function of the lateral vestibulospinal tract?

provides way for vestibular input to affect posture

8

What is the origin, route, and termination of the medial vestibulospinal tract?

•origin – vestibular nuclei
•only descends as far as upper thoracic cord
Terminates in the muscles of the head and neck

9

What is the function of the medial vestibulospinal tract?

•main function is mediation of reflex head movements in response to vestibular stimuli. It helps adjust the position of the head in response to postural changes

10

What is the origin and route of the medial (pontine) reticulospinal tract?

• origin - pontine reticular formation
• descends to all levels of the spinal cord

11

What is the function of the medial (pontine) reticulospinal tract?

Facilitate muscle tone of lateral extensors via the gamma motor neuron loop

12

Summarize the gamma motor neuron loop. (this is in case you have forgotten)

Stimulation of gamma motor neurons produces stretch on muscle spindles. These activate type Ia fibers, which synapse on alpha motor neurons to produce muscle tone

13

What is the origin and route of the lateral (medullary) reticulospinal tract?

• origin - medullary reticular formation
Terminates at all spinal cord levels

14

What is the function of the lateral (medullary) reticulospinal tract?

Excites flexors, inhibits extensors

15

The lateral and medial reticulospinal tracts have opposing functions. Which excites extensors and inhibits flexors?

medial excites extensors, inhibits flexors.

Lateral is opposite

16

What is the function of the reticulospinal system?

can modulate reflex action during movement

17

What is the overall function of the reticulospinal tract?

Muscle tone

18

What is the overall function of the vestibulospinal tract?

Posture and balance

19

True or false: the reticulospinal tract is heavily influenced by projections from the cortex via cortico reticulo tract

True--integrates vestibular and other sensory input with motor commands from cerebral cortex

20

What is the origin and route of the the tectospinal tract?

Origin = superior colliculus
Route = projects to cervical spinal cord

21

What is the function of the tectospinal tract?

Reticulospinal tracts important in coordinating head and eye movements

(the "look that way" reflex)

22

What is the function of the superior and inferior colliculi?

Superior = visual integration and reflexes

Inferior = auditory integration and reflexes

23

What is posture?

overall position of the body and limbs relative to each other and
orientation of body and limbs in space.

24

What is postural stability?

“the ability to control the center of mass in relationship to the base of support.”

25

What is the purpose of postural adjustments? (3)

1. Support head
2. Maintain center of gravity
3. Stabilize supporting parts of the body during movement

26

What are the two mechanisms that posture can make use of to keep things stable (think proprioceptive things)?

Feedforward and feedback

27

What system of the body that plays a role in posture senses sway?

Vestibular

28

What are the four systems of the body that play a role in posture (think romberg)? (4)

1. Vision
2. Proprioception
3. Vestibular
4. Cutaneous tactile receptors

29

What is vection?

The perception of self-motion induced by visual stimuli

30

What is visual kinesthesis?

Feeling of body movement when large part of a person's visual field is moving

31

What are the postural reflexes that maintains the head in an upright position? (3)

-Vestibulocollic (vestibular)
-Cervicocollic (proprioception)
-Visual

32

What is the asymmetrical tonic neck reflex?

Infants will extend limbs toward the side the head/neck is turned--this is normal until 6 months-ish

33

Vestibular and neck reflexes can have opposing actions on limb muscles. Why is this desirable?

This is desirable since otherwise voluntary movement of the head would stimulate vestibulospinal reflexes which would change posture every time head was turned or tilted

34

What is the symmetrical tonic neck reflex?

When the neck is extended the upper limbs extend and the lower limbs flex

35

When is the symmetrical tonic neck reflex normal or abnormal?

appears in infants around 4-6 months and disappears before 1 year of age

Can appear in cerebral/vestibular damage

36

Why does the tonic neck reflex present in pts with vestibular damage?

Normally the vestibular postural reflexes (tonic labyrinthine reflex) on the limbs are opposite to those caused by neck proprioceptors. When vestibular reflexes are lost with vestibular damage, the unopposed tonic neck reflexes become visible.

37

What is the labyrinthine reflex?

When the neck is extended the upper limbs flex and the lower limbs extend (opposite that of the tonic neck reflex)

38

What is decerebrate posturing?

Extension of all four limbs and the neck

39

True or false: decerebrate posturing can be intermittent

True

40

What causes decerebrate posturing?

If there is a lesion below the red nucleus but above the vestibular nuclei, the lateral vestibulospinal tracts increase their facilitation of extensor motor neurons.

41

What is decorticate posturing?

Arms flexed and legs extended

42

What causes decorticate posturing?

lesions of the internal capsule that release both vestibulospinal and tonic neck reflexes from cortical control. Can also be caused by lesions in the upper midbrain/diencephalon.

43

What is produced by turning a pt who has decorticate posturing when you turn their neck?

Asymmetrical tonic neck reflexes in the arms

44

A lesion in the supratentorial space will produce what: decerebrate or decorticate posturing?

Decorticate

45

How is postural stability maintained?

Through continuously monitoring posture and making appropriate adjustments

46

True or false: reflexes are not able to be modified

False

47

What are the two results of the series of experiments she described in lecture?

1. Reflexes are modifiable
2. The body can retrain reflexes if doing so increases postural balance

48

What is the feedforward control mechanism?

Apply corrective action before there is error in controlled variable

49

What is the feedback control mechanism of reflexes?

Appropriate correction is applied after error (e.g. loss of balance) is detected

50

What allows decerebrate cats to regain walking motion?

Stepping pattern generators in the spinal cord

51

True or false: newborn infants show a stepping reflex?

true

52

Do humans have stepping pattern generators?

Yes, but does not function as well as in cats

53

How do stepping pattern generators work?

the actions of both legs are coordinated through commissural fibers and LMNs.

54

Why doesn't the stepping pattern generator not work in humans as well as in cats?

Human walking requires cortical control of ankle dorsiflexion and general postural control to maintain balance. Afferent information is used to adjust the timing of the step cycle and to facilitate the transition from stance to swing phase of gait.

55

What is the MOA of selective dorsal rhizotomy?

Loss of gamma motor neuron loop by eliminating the Ia fibers

56

Why does cutting the dorsal roots decrease muscle tone in a subject with decerebrate rigidity?

Loss of gamma motor neuron loop by eliminating the Ia fibers

57

Which type of rigidity is also known as gamma ridigity?

Decerebrate