Motor systems overview

Activated muscles work in two ways - ______ (____)
_____ (____)

Phasically (dynamic)

Tonically (static)

Afferent info like _____ and ____ ___ are critical in ____ control

Afferent info like proprioception and special sense are critical in motor control

Central pattern generators (____ ____) activate ____ motor responses that do ____ _____ ____ feedback

Central patter generators (neural oscillators) activate complex motor responses that do not require afferent feedback

Patterned movements are ____ that elicit movement without _____

These include ______ or ______ ____

Complex motor activities like _____ and _____ using ______ ___ _____

Patterned movements are circuits that elicit movement without volition

These include static or dynamic postural control

Complex motor activities like walking and scratching using central pattern generators

Volitional activities are driven by the ____ ____ - they become ______ ______ _____

Initially very _____ and use ____ and _____ until _____

Once _____ movements become too fast there is no ____

Volitional activities are driven by the cerebral cortex - they become learned motor behaviors

Initially very intentional and use feedback and guidance until programmed

Once programmed movements become too fast there is no feedback

Direct pathways for motor control include ______ ______ to _______ ____

Indirect include the ____ - ____ - _____ pathway

Direct pathways for motor control include corticospinal tracts to interneuron pools

Indirect include the cortico-brainstem-spinal pathway

A motor unit is a ____ ___ and all ____ ____ it innervates

______ _____ is the lowest integration point in ____ ___ - AP generation depends on ____ ___ of all ____ and _____ inputs at that time

A motor unit is a motor neuron and all muscle fibers it innervates

Alpha motorneuron is the lowest integration point in motor control - AP generation depends on algebraic sum of all excitatory and inhibitory inputs at that time

As demand for motor strength increases, there is _____ recruitment of ____ ___ - smaller diameter motor neurons fire more ____ than ______ ____ motor ____ (because...)

As demand for motor strength increases there is progressive recruitment of motor units - smaller diameter motor neurons fire more easily than larger diameter motor neurons (because smaller neurons have higher resistance therefore current change produces larger voltage)

As the frequency of nerve input increases, there is a shift from a ____ to a ____ response - tension development is greater during a _____ ____

As the frequency of nerve input increases, there is a shift from a twitch to a tetanic response - tension development is greater during a tetanic response

Twitch fibers are low ____ and not much ____

Low fatigue and not much force

The corticospinal and rubrospinal tract terminate in ______ _____ ____ and regulate motor neurons that innervate ____ ____ muscle groups

These are located ______

The corticospinal and rubrospinal tracts terminate in contralateral ventral horns and regulate motor neurons that innervate volitional distal muscle groups

These are located laterally

The vestibular and reticular formation motor nuclei terminate in ______ _____ components of the ____ ___ - these regulate motor neurons that innervate ______, _____ muscles

These are located ____

The vestibular and reticular formation motor nuclei terminate in ipsilateral medial components of the ventral horn - these regulate motor neurons that innervate axial, proximal muscles

These are located medially

Afferent fibers branch when inside the ____ ___ and innervate ____ ____ - this is ____

Afferent fibers branch when inside the spinal cord and innervate multiple targets - this is divergence

______ and ______ determine the discharge and _______ zones

_____ zones (______ ____) are excited to ____
______ fringe are not

Convergence of afferents can shift from a _____ ___ to a _____ if multiple afferents are _____ ______

Convergence and divergence determine the discharge and facilitated zones

Discharge zones (Liminal fringe) are excited to threshold

Subliminal fringe are not

Convergence of afferents can shift from a facilitated zone to a discharge if multiple afferents are recruited simultaneously

In reflexes, reciprocal innervation coordinates ______ ___ around a ____ - ____ are essential for this organization

In reflexes, reciprocal innervation coordinates muscle activity around a joint - interneurons are essential for organizing movement

In the muscle spindles, there is a dynamic nuclear bag which detects ___ of ____ in ____

A static nuclear bag which detects ______ ____ ____

There is no _____ in ______ fibers

In the muscle spindles, there is a dynamic nuclear bag which detects rate of change in length

A static nuclear bag which detects final muscle length

There is no actin in intrafusal fibers

The 1a afferent in stretch reflex have a ____ and ____ phase of ____ discharge

They can monitor ____ ___ and ___ of _____

Go to alpha motor neuron and do ____ ___ of ___

There is _____ excitation of ____ _____ which are ____ to muscle

_____ of _____ muscles through an _____ _____

Diverges to the ______ ___ _____ for ______ _____

Diverges to the _____ ____ - by using these two pathways there is ____ of ____ ____

The 1a afferent in stretch reflex have a dynamic and static phase of AP discharge

They can monitor muscle length and rate of change

Go to alpha motor neuron and do liminal activation of muscle

There is subliminal excitation of motor neurons which are synergistic to muscle

Inhibition of antagonizing muscles though an inhibitory interneuron

Diverges to the column of clarke for unconscious proprioception

Diverges to the dorsal columns - by using these two pathways there is conservation of afferent info

Descending input to a ____ cell can affect _____ of motor neurons around a ____

Limb muscle reflexes can have both ____ and _____ components

Descending input to a renshaw cell can affect excitability of motor neurons around a joint

Limb muscle reflexes can have both spinal and supraspinal components

The gamma efferent in stretch reflex increases the discharge of ______ ____

the gamma efferent in stretch reflex increases the discharge of Ia afferent

Golgi tendon provides information about _____ ____ in motor units arranged in ____ with the receptor - the nerve ending within the tendon (_____) is arranged in _____ with ___-____ motor units

Golgi tendon provides information about muscle tension in motor units arranged in series with the receptor - the nerve ending within the tendon (flowerspray) is arranged in series with 5-15 motor units

Golgi tendon organs 1b afferent are less sensitive to ____ ____

Inhibits via a _____ ____

Facilitates ____ pathways to activate ____ ____ through the ____ __ ____

During walking the central program reduces the effect of the _____ ____ while activating the ____ ____ - state-dependent ____ _____

golgi tendon organs 1b afferent are less sensitive to passive stretch

Inhibits via a disynaptic pathway

Facilitates multisynaptic pathways to activate heteronymous antagonists through the column of clarke

During walking the central program reduces the effect of the inhibitory interneuron while activating the excitatory interneuron - state-dependent reflex reversal

Withdrawal reflex is removal of a limb from ___ ___

Receptors are _____ ____ nociceptors

Terminal projections to ____ ___, ___ fibers

Diverge _____ to give info to ___

_____ pathway

Crossed ____ ___ mediated by _____ and _____ circuits

Withdrawal reflex is removal of a limb from harmful stimuli

Receptors are unmyelinated cutaneous nociceptors

Terminal projections to Group III, C fibers

Diverge anterolaterally to give info to CNS

Multisynaptic pathway

Crossed extension reflex mediated by segmental and intersegmental circuits

Activation of _____ sensitive channels in muscle spindles leads to generation of _____ _____ in the _____ nerve. This senses muscle ____ and ___ of ____ in _____

Descending inputs ( ______) ____ ___ and ____ motor neurons to avoid ____ ___ - ____ ____ neuron activates ____ fibers that ____ the ____ causing ____ activity

Stimulation of only _____ would cause ____ to ____ - muscle ____ would lead to loss of ____ ___ activity (_____ period)

Co activation of ____ and ____ motor neurons avoids a ____ ___

______ neurons are smaller and fire first so they can _____ _____ activation

Activation of stretch sensitive channels in muscle spindles leads to generation of action potentials in the sensory nerve. This senses muscle stretch and rate of change in length

Descending inputs (corticospinal) coactivate alpha and gamma motor neurons to avoid silent period - gamma motor neuron activates intrafusal fibers that stretch the spindle causing 1a activity

Stimulation of only alpha would cause spindle to shorten - muscle twitch would lead to loss of 1a afferent activity (silent period)

Co activation of alpha and gamma motor neurons avoids a silent period

Gamma neurons are smaller and fire first so they can precede alpha activation

Types of gamma motor neurons include ____ which influence the response to _____ stretch of muscle (____ and ___)

_____ which influence response to ____ ___ (____ and ____)

Types of gamma motor neurons include dynamic which influence the response to phasic stretch of muscle (quick and brief)

Static which influence response to static stretch (slow and maintained)

The fusimotor system ensures _____ information about muscle length is continuously forwarded to _____ ____ centers

This is important because muscle ____ and ______ _____ depend on integrity of the ____ reflex - ____ is due to low level ___ of ___ ___ by the ____ ____

The fusimotor system ensures afferent information about muscle length is continuously forwarded to CNS motor center

This is important because muscle tone and reflex state depend on integrity of the stretch reflex - tone is due to low level activation of motor units by the stretch reflex

Changes in deep tendon reflex can reflect changes in _____ of ______ _____

Directly modulated by activation of _____

Indirectly modulated by activation of ____ ____

There is no _____ input to ____

Changes in deep tendon reflex can reflect changes in excitability of alpha motorneuron

Directly modulated by activation of alpha

Indirectly modulated by activation of gamma loop

There is no 1a input to gamma

Spasticity is a sign of ____ disease that reflects a change in ____ of the _____ ____

Enhanced resistance to ____ _____

Increase in _____ of ____ muscles
Decrease in _____ muscles

Loss of _____ ____ and overactive ____ ___

_____ _____ leads to gamma motor neuron _____ - dynamic ____ ___ leads to increased ______ and an increase in ____ ___ firing leading to _____ ____

Spasticity is a sign of UMN disease that reflects a change in properties of stretch reflex

Enhanced resistance of passive extension

Increase in DTR of antigravity muscles
Decrease in antagonistic muscles

Loss of descending inhibition and overactive alpha motor neurons

1a Hypersensitivity leads to gamma motor neuron overactivity - dynamic gamma firing leads to increased DTRs and an increase in static gamma firing leading to increased tone

Spasticity can result from alteration in either ____ or ____ -reflex pathway can be enhanced by background _____ ____

Spasticity can result from alteration in either alpha or gamma - reflex pathway can be enhanced by background excitatory tone

Spinal central pattern generators can be initiated in absence of ____ or _____ ____ inputs

Direct activation of ____ ___ ____ in the ____

Locomotor circuits can be activated by ____ ___ from ____ ___ and _____ ___

Peripheral sensory information can modify _______ ______

Spinal central pattern generators can be initiated in absence of descending or local sensory inputs

Direct activation of central pattern generators in the CNS

Locomotor circuits can be activated by descending information from brainstem nuclei and cerebral cortex

Peripheral sensory information can modify locomotor circuits