Intro to Motor system Flashcards Preview

Physiology > Intro to Motor system > Flashcards

Flashcards in Intro to Motor system Deck (55):
1

What type of movement is walking, chewing etc?

Rhythmic motor pattern (subconscious usually)

2

What does the nervous system need to know in order to produce movement? (4)

1. Initial length of the muscle
2. Velocity of muscle length change
3. External loads acting to oppose movement
4. Visual and vestibular info

3

What type of fibers innervate GTOs?

Type Ib afferent

4

What type of fibers innervate muscle spindles?

Type Ia afferent

5

What is feedback control?

use of sensory information during movement to make corrections to the on-going movement.

6

What is feedforward control?

- Sensory information contributes to anticipating the effect of planed movement

7

What is the motor pathway?

Parietal/premotor/supplementary motor cortex to the

Primary motor cortex
Brainstem
Spinal cord

8

What are the two inputs to the thalamus that affect its output to the primary motor cortex?

Basal nuclei
Cerebellum

9

What are the two places that the cerebellum sends information to in the motor pathway?

Brainstem
Thalamus

10

What is the hierarchical organization of the motor control centers?

Cortical areas
Brainstem
Spinal cord

11

What two parts of the brain modify output from the motor cortex?

Basal ganglia
Cerebellum

12

What is the difference between UMNs and LMNs?

UMNs go to a ganglia/nucleus

LMNs symapse on effector muscle

13

What role do gamma motor neurons play in the nervous system?

Innervate intrafusal skeletal muscle fibers, the small muscle fibers within the muscle spindles

14

What are skeltal-fusimotor neurons?

Nerves that innervate both extrafusal and intrafusal muscle fibers: this is sometimes called beta activation

15

Where are LMNs found in the spinal cord?

Anterior horn of the gray matter, with their axons leaving the spinal cord via the ventral root

16

What are alpha motor neurons?

neurons that innervate muscles in the PNS

17

What is a motor neuron pool?

All the neurons that control one muscle

18

What is a motor unit?

one alpha motor neuron plus all the skeletal muscle fibers it innervates

19

What are the four functional components of a motor unit?

• cell body of motor neuron
• axon
• neuromuscular junction
• muscle fibers

20

Where are small motor units used in the body?

Where fine control is needed (oculomotor muscles in the eyes)

21

Where are large motor units used in the body?

In strong muscles that do not need fine control

22

What is the pathogenesis of post-polio syndrome?

surviving motor neurons “adopt orphaned” muscle fibers. This increases stress on these fibers, with repeated remodeling with denervation and reinnervation

23

What produces graded muscle contraction? (there are two options here)

recruitment of more and more muscle units and/or increase the rate at which the alpha motor neuron of each motor unit is firing.

24

What is Henneman's size principle?

order of recruitment of motor neurons = first recruit small neurons, and then larger neurons, since smaller ones will depolarize first

25

True or false: muscles need constant, low level stimulation. Why?

True, since need muscle protein gene expression

26

What are the symptoms of a LMN lesion?

Atrophy
Hypotonia
Hyporeflexia
Fibrillations/fasciculations

27

What causes the weak reflexes seen in a LMN damage?

Loss of alpha motor neurons to the muscle

28

What are fasciculations?

- visible twitches of muscle that can be seen as ripples under the skin

29

What are fibrillations?

spontaneous activity within single muscle fibers. They are not visible clinically since they are too small to be seen as movement through the skin

30

How do you detect fibrillations of muscle?

Electromyography

31

Fasciculations are a sign of what?

LMN disorder

32

What is the difference in innervation between fasciculations and fibrillations?

Fasciculations are when entire muscle groups are still connected after a lesion, so contract together.

Fibrillations are when fibers are not innervated together, thus single fibers twitch

33

What is an injury potential?

Potential generated at site of injury to a motor neuron axon.

34

What happens to muscles that are denervated that causes them to be super sensitive?

Increased number of Ach receptors

35

Flaccid paralysis results when what occurs with the nerves?

Total loss of innervation

36

What is paresis?

paresis refers to partial loss of voluntary contraction or voluntary muscle weakness.

37

Which type of lesion causes flaccid paralysis? Spastic?

Flaccid = LMN or initially with UMN
Spastic = UMN

38

A complete transection of the spinal cord will result in flaccid or spastic paralysis?

Initially flaccid, then spastic

39

What is spinal shock?

the temporary loss of spinal cord reflex activity that occurs below a total (or near total) spinal cord injury.

40

What are the three components/symptoms of spinal shock?

1. Flaccid paralysis
2. Areflexia
3. Loss of autonomic function below level of transection

41

How long do symptoms of spinal shock last? What then?

a few days to weeks

Progresses to hyperreflexia

42

Babinski sign it a test for what type of neuron lesion?

UMN

43

What is the MOA of spinal shock syndrome? (3)

Increased blood supply or loss of edema around spinal cord

Loss of inhibition of gamma motor neurons

44

What is an UMN?

a neuron in a higher motor area (e.g. motor cortex, premotor cortex, brainstem center) that synapses on a lower motor neuron or on an interneuron which synapses on a lower motor neuron.

45

Spinal cord lesions (e.g. those caused by a broken neck) damage what type of neurons?

LMNs at the site of injury
UMN if spinal tract involved

46

What are the two parts of the spinal cord that produce a multitude of symptoms if transected?

The cervical and lumbar enlargements

47

What is spasticity?

a motor disorder characterized by a velocity- dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, and is one component of the upper motor neuron syndrome.

48

The oculomotor and trochlear nuclei are UMN or LMNs?

LMNs

49

True or false: there can be LMNs above UMNs in the spinal cord

True, as long as they are not part of the same tract

50

True or false:Damage of the spinal cord can damage both LMNs and UMNs

True

51

True or false: spinal cord lesions always affect all of the descending motor tracts

False--can have only one

52

Upper motor neuron syndrome is what?

When all tracts of UMNs are lesioned

53

DTR are overactive in UMN or LMN lesions?

UMN

54

If a pt presents with both UMN and LMN signs, what should immediately be in your ddx?

ALS

55

What is the pathogenesis of ALS?

Loss of myelination of UMNs and LMN of unknown etiology