Motor system: neuro lecture 2

movement is orchestrated by coordinated action of what (5)

movement is orchestrated by coordinated action of what (5)

1. peripheral

2. spinal

3. brain stem

4. cerebellar

5. cerbebral regions

*movement is shaped by a specific context and directed by intentions of the performer

what amount of the nervous system is directly involved in motor performace

more than half

what is the most common manifestation of disease in the nervous system

disruption of motor control

what are the 2 types of lower motor neurons

1. alpha motor neurons

2. gamma motor neurons

alpha motor neurons:

1. cell body… (1)

2. exits spinal cord… (1)

3. innervates… (1)

4. neurotransmitter… (1)

5. axons… (1)

1. ventral horn of spinal cord

2. ventral root

3. extrafusal skeletal muscle

4. Ach

5. large myelinated Aa (fast)

gama motor neurons

1. cell body… (1)

2. exits… (1)

3. innervates… (1)

4. axons (1)

1. ventral horn

2. ventral root

3. intrafusal fibers of muscle spindle

4. medium myelinated Ay

what is a motor unit

single alpha motor neuron and the muscle fibers it innervates

• small motor units in hands due to doing fine movements and need lots of motor neuron innervating small motor units

• quads have big motor units by generating power… one motor neuron innervates it

• motor neuron pool = all alpha motor neuron contribute to it

what is slow twitch - type 1 used for (2)

postural and slowly contracting muscles

• low fatigue; stabilization/background

what is fast twitch - type IIA, IIB

phasic, power producing muscles

• dependent on its innervation

• slow twitch muscle fibers fire first during movements because their smaller cell bodies in anterior horn depolarize faster

peripheral sensory input to motor neurons:

• sensory information from GTO and muscle spindles give information regarding ____ (3)

1. tension

2. muscle length

3. rate of change in length

*info can be processed at multiple levels to adjust activity of motor output

what is the importance of the alpha-gamma coactivation

maintain stretch on central region of muscle spindle

* maintains stretch on central region of muscle spindle intrafusal fibers by contracting at the ends of the intrafusal fibers when the extrafusal fibers actively contract

* the purpose is to maintain the stretch sensitivity of the muscle spindle when the extrafusal muscle fibers are contracted

*during most movements the alpha and gamma motor neuron systems function simultaneously

myotome: elbow flexion

C5

myotome: wrist extension

C6

myotome: elbow extension

C7

myotome: flexion of tip of middle finger

C8

myotome: finger abduction

T1

myotome: hip flexion

L2

myotome: knee flexion

L3

myotome: ankle dorsiflexion

L4

myotome: great toe extension

L5

myotome: ankle plantar flexion

S1

what is a myotome

groups of muscle innervated by a single spinal nerve

what are motor neuron pools

group of alpha motor neurons innervating a single muscle

• axons from a motor pool project to one muscle

• cell bodies whose axons project to a single muscle are clustered in motor pools

what makes up the medial pool (2)

axial and proximal musles

what makes up the lateral pools

distal musculature

what makes up the anterior pools

extensors

what makes up the posterior pools

flexors

what 4 things make up the spinal region coordination

1. muscle synergies = when bicep and bronchialis work together to get same effect

2. stepping pattern generators = reciprocal movement is spinal cord feature (conscious start walking to automatic walking)

3. reflexed = deep tendon reflexes

4. reciprocal inhibition = when fire bicep you turn down tricep… sometimes want stability when doing plank so both on to keep elbow stable

what is thought to be the sole basis of movement by early neuroscientists

reflexes

• most movement is voluntary with some contributions of reflexive movement

• reflex examination can give some idea of the integrity of the motor system at the peripheral and spinal cord level

• too low reflexes = PNS problem

stretch reflexes: (5)

1. myotactic reflex

2. deep tendon reflex

3. monosynaptic

4. autogenic facilitation

5. phasic vs tonic

what is the role of the GTO

info regarding tendon tension

• helps to modulate muscle contraction/tension of tendon

• works with other proprioceptors

• may facilitate or inhibit based on task (stance vs swing can tell tension being applied to it - excitatory/inhibitory)

what 4 items make up the cutaneous reflexes

1. flexor withdrawal reflex = multisynaptic; hand on hot stove and moves it

2. crossed extension = lift R leg from nail and extend L leg to balance

3. abdominal reflex = scrape abdominal with reflex hammer and causes it to contract so when stimulate skin on muscle

4. plantar reflex = babinski

what is the H reflex

electrical equivalent of stretch reflex = quantifiable tells you excitability of stretch reflex

• can be used to quantify excitability (or lack of) of alpha motor nerves

medical activation system: posture and gross movement

1. where does it tend to synapse

2. what movement is it biased for

1. tend to synapse on motor neurons located medially in ventral horn (which supply proximal postural muscles)

2. tend to be extensor biased

*all descending pathways of posture and gross movements

* 4 tracts brain stem; 1 cortex

major pathways of the medial system (5)

1. medial corticospinal tract

2. lateral vestibulospinal tract

3. medial vestibulospinal tract

4. tectospinal tract

5. pontine (medial) reticulospinal tract: reticulospinal tract

what is the function of the medial (anterior/ventral) corticospinal tract

axial and proximal joint control of neck, shoulder, trunk

what is the motor homonculus

• posterior limb internal capsule = all sensory and motor fibers run same path

• motor fibers run down in crus cerebri

• crossing over to lateral and if not its medial corticospinal tract

what is the function of the medial vestibulospinal tract

regulates activity of upper back and neck muscles in response to vestibular input

what is the function of the lateral vestibulospinal tract

fascilitate antigravity muscles of ipsilateral extremities and inhibits non-antigravity muscles

what is the function of the tectospinal tract

mediates reflexive movement of head and neck to visuli stimuli

what is the function of the pontine (medial) reticulospinal tract

activates ipsilateral lower motor neurons of postural muscles and limb extensors

*functions normally with minimal input from cortex

what is the lateral activation pathway

• where does it descend

• where does it synapse with

• descend in lateral spinal cord

• synapses with motor neurons in lateral portion of ventral horn

fine movement, fractionation of movement (lateral activation pathways) = x3 tracts

1. lateral corticospinal

2. medullary (lateral) reticulospinal tract

3. rubrospinal

what is the function of the lateral corticospinal tract

fractionation of movement (ability to activate individual muscles independently of other muscles)

what is the function of the medullar (lateral) reticulospinal tract

• regulation of tone (more inhibitory than facilitory) requires input from cortex to function appropriately

• facilitates flexors and inhibits extensors

  • during walking this effect is reversed

what is the function of the rubrospinal tract

closely associated with lateral corticospinal tract, flexors of UE; more developed in monkeys

where does the corticobulbar tract motor supply go to

from cortex to cranial nerves innervating musculature of head and neck

the corticobular tract pathways end when _____

all are crossed

the corticobulbar tract gives innervation to what

upper face recieve bilateral innervation

what are 2 nonspecific activating pathways

1. cerulospinal tract

2. raphespinal tract

the nonspecific activating pathways have general effects on what (2)

1. motor performance

2. motivation

*doesnt innervate specific muscles

*choking patterns = stressed/nervous think youll fail; overactive and turns on all muscles so tighten up… fine distal control (basketball) is not good with this

what is the primary motor area 4

• movement _____ and ______

• more than ________…

• movement execution and fractionation

• more than 50% hand and speech

*store programs of tasks you do all the time

what is the supplementary motor area 6

• activate prior to _____ and _____

activate prior to bimanual tasks and sequential movements

*ex. buttoning your shirt… need both hands and steps

what is the premotor area 6

• generates patterns of movement involving _______ and _______

generates patterns of movement involving multiple muscle groups and joints

*rowing motion → repetitive pattern movement