lecture 28 - motor systems: spinal cord and brain stem

Question 1

what are the 4 classifications of movement?

Answer 1

reflexive, postural balance, volitional (reaching for a cup), and repetitive (walking)

Question 2

list reflexive, volitional and postural balance in order from most automatic to least automatic

Answer 2

reflexive, postural balance, volitional

Question 3

what are two divisions of the motor system

Answer 3

lateral and medial motor systems

Question 4

describe the descending lateral pathway

Answer 4

cerebral cortex –>

1. cerebellum –> red nucleus
2. basal ganglia –> red nucleus
3. directly to the red nucleus
   - -> sc

Question 5

what is the descending lateral pathway?

Answer 5

rubrospinal

Question 6

what are the 3 descending medial pathways?

Answer 6

vestibulospinal, reticulospinal, tectospinal

Question 7

describe the descending medial pathways

Answer 7

cerebral motor cortex –> cerebellum/basal gang/direct –>

vestibulospinal: vestibular nuclei –> sc
reticulospinal: reticular formation –> sc
tectospinal: superior colliculus –> sc

Question 8

provide a general overview of the ascending pathways of the motor system

Answer 8

cerebellum/basal ganglia –> thalamus –> cerebral cortex

Question 9

what is a motor unit?

Answer 9

combination of a motor neuron and the muscle fibers it innervates

Question 10

what are the rules for motor units?

Answer 10

1. many motor neurons target each muscle
2. each motor neuron targets only one muscle
3. each muscle fibre is only innervated by one motor neuron
4. when a motor neuron fires, all its fibers contract

Question 11

what is a motor neuron pool?

Answer 11

collection of motor neurons whose axons all connect to the same muscle, although the neurons may be scattered across different levels of the sc

Question 12

describe changes between the normal state and neurogenic disorders

Answer 12

loss of motor neurons

Question 13

describe changes between the normal state and myogenic disorders

Answer 13

muscle fibre degeneration

Question 14

describe the muscle at rest in its normal state, in neurogenic disorders and in myogenic disorders

Answer 14

normal: at rest
neurogenic: fibrillation
myogenic: fibrillation

Question 15

describe the muscle during slight contraction in its normal state, in neurogenic disorders and in myogenic disorders

Answer 15

normal: regular, spaced out contractions
neurogenic: one giant contraction, lots of small irrgeular ones
myogenic: fibrillation: small polyphasic units (smaller and more irregular than normal)

Question 16

describe the muscle during maximal contraction in its normal state, in neurogenic disorders and in myogenic disorders

Answer 16

normal: regular
neurogenic: reduced inference pattern
myogenic: full inference pattern but not as much range

Question 17

describe histochemical changes from motor neuron loss

Answer 17

• motor neuron dies
• muscle fibres dennervated and die/atrophy
• axons of surviving neurons tend to sprout and innervate dennervated fibres
• muscle fibre types become clustered

Question 18

is neuronal regeneration in the PNS slow or fast

Answer 18

slow

Question 19

why can neuronal degernation occur in the motor system of the PNS?

Answer 19

because the targets are promiscuous

motor unit innervates multiple muscles, while sensory fields are less well-defined

Question 20

explain the process of neuronal regeneration in the PNS

Answer 20

• begins with injury to peripheral nerve
• macrophages arrive and rapidly remove myelin debris
• neuron expresses growth related genes
• proliferating schwann cells promote axon regeneration

Question 21

what are the two types of muscle spindles

Answer 21

primary and secondary

Question 22

describe primary muscle spindles

Answer 22

largely respond to velocity of stretch

Question 23

describe secondary muscle spindles

Answer 23

largely respond to muscle length

Question 24

gamma motor neurons change what with respect to muscle spindles?

Answer 24

the excitability of spindle responses

Question 25

describe the deep tendon reflex

Answer 25

monosynaptic excitation of the agonist, disynaptic inhibition of the antagonist (sensation immediately results in reflex)

Question 26

what would result in an increased deep tendon refelx?

Answer 26

upper motor neuron lesions

Question 27

what would result in a decreased deep tendon reflex?

Answer 27

- acute upper motor neuron lesions | - peripheral, sensory, motor neuron and/or muscle abnormalities

Question 28

what muscles/tendons are involved in the upper extremity deep tendon reflex?

Answer 28

biceps, brachioradialis, triceps, patellar, achilles tendon

Question 29

what is the corresponding nerve root for the biceps?

Answer 29

C5, C6

Question 30

what is the corresponding nerve root for the brachioradialis?

Answer 30

C6

Question 31

what is the corresponding nerve root for the triceps?

Answer 31

C7

Question 32

what is the corresponding nerve root for the patellar?

Answer 32

L4

Question 33

what is the corresponding nerve root for the achilles tendon?

Answer 33

S1

Question 34

what is the function of the flexor reflex?

Answer 34

acts to lift foot away from painful stimuli

Question 35

what is excited and what is inhibited during the flexor reflex?

Answer 35

``` flexors = excited extensors = inhibited ```

Question 36

what is the function of the crossed extensor reflex?

Answer 36

acts to support the body on the other leg (when lifting one up for flexor reflex)

Question 37

what is excited and what is inhibited during the crossed extensor reflex?

Answer 37

``` excited = extensors inhibited = flexors ```

Question 38

do the flexor and the crossed extensor reflex go hand in hand

Answer 38

yes

Question 39

what generates the pattern of muscle leg activity?

Answer 39

central pattern generator in the spinal cord

Question 40

is the lateral vestibular nucleus ipsilateral or bilateral?

Answer 40

ipsilateral

Question 41

is the medial vestibular nucleus ipsilateral or bilateral?

Answer 41

bilateral

Question 42

what is the function of the lateral vestibular nucleus?

Answer 42

maintaining equilibrium, posture and vision w movement

Question 43

what is the function of the medial vestibular nucleus?

Answer 43

head and neck position

Question 44

is the pontine reticular formation ipsilateral or bilateral?

Answer 44

ipsilateral

Question 45

is the medullary reticular formation ipsilateral or bilateral?

Answer 45

ipsilateral

Question 46

what is the function of the pontine reticular formation?

Answer 46

posture and gait-related movement

Question 47

what is the function of the medullary reticular formation?

Answer 47

posture and gait-related movement

Question 48

is there a relationship btwn voluntary motor action and whole-body postural control?

Answer 48

- yes - coordinate | - e.g., leg muscle turns on to stabilize the body before a voluntary arm movement

Question 49

is the superior colliculus ipsilateral or bilateral?

Answer 49

trick question! its contralateral

Question 50

what is the function of the superior colliculus?

Answer 50

coordination of the head and neck

Question 51

is the red nucleus ipsilateral or bilateral?

Answer 51

contralateral

Question 52

what is the function of the red nucleus?

Answer 52

coordination of sensorimotor info (limb control)

Question 53

2 posturing reflexes are associated with coma, true or false?

Answer 53

true

Question 54

describe flexor posturing during coma

Answer 54

patient flexes inwards (arms come into chest)

Question 55

describe extensor posturing during coma

Answer 55

patient flexes out (arms flex down at sides)

Question 56

flexor posturing is associated with what?

Answer 56

function above red nucleus (midbrain)

Question 57

extensor posturing is associated with what?

Answer 57

function below the red nucleus (midbrain)

Question 58

hint fot posturing during coma?

Answer 58

the higher the arms the higher the function