Term
| Consists of a single alpha motor neuron, including all branches of the axon, and all the muscle fibers innervated by that alpha motor neuron. |
|
Definition
|
|
Term
| Does more muscle fibers result in a larger or smaller motor unit? |
|
Definition
|
|
Term
| Name the 3 primary muscle types |
|
Definition
|
|
Term
| This type of muscle is multinucleated, striated, and helps to move bones. |
|
Definition
|
|
Term
| Innervated by a single motor neuron |
|
Definition
|
|
Term
| Does 1 motor neuron innervated more than one muscle fiber? |
|
Definition
|
|
Term
| Each muscle fiber is innervated by what? |
|
Definition
|
|
Term
| A single motor neuron can innervate one or more muscle fibers? |
|
Definition
|
|
Term
| The size of what is dependent on the number of muscle fibers contained within it? |
|
Definition
|
|
Term
| Motor unit size varies for each ___ |
|
Definition
|
|
Term
| Muscle involved in skilled movements requiring fine control have a very low ratio of what? |
|
Definition
| Muscle fibers to motor neuron |
|
|
Term
| Muscles requiring fine control have large or small sized motor units? |
|
Definition
|
|
Term
| List a few examples of muscles requiring fine control. |
|
Definition
| The muscles of the middle ear (stapedius, tensor tympani) and the extraocular muscles of the eye which may contain as few as 1-5 muscle fibers per motor neuron. |
|
|
Term
| Muscles involved in less precise, more forceful movements have very high ratios of what? |
|
Definition
| Muscle fibers to motor neurons |
|
|
Term
| Do muscles used for forceful movements have larger or smaller motor units? |
|
Definition
|
|
Term
| Name a few muscles that are used for forceful movements. |
|
Definition
Gastroc
Quads
Tibialis Anterior |
|
|
Term
| These types of muscles can contain as many as 500 to 1000 muscle fibers per motor neuron. |
|
Definition
| Forceful movement (Gross) muscles |
|
|
Term
| Activation of how many motor neurons results in contraction of ALL muscle fibers within that motor unit? |
|
Definition
|
|
Term
| Activation of one motor neuron results in contraction of all muscle fibers within what? |
|
Definition
|
|
Term
| Name 2 characterizations of muscle fibers |
|
Definition
1. Type of myosin present
2. Type of energy metabolism used |
|
|
Term
| Are all muscle fibers in a motor unit of the same fiber type? |
|
Definition
|
|
Term
| A combination of motor neuron and all of the muscle cells that it innervates. |
|
Definition
|
|
Term
| Each muscle cell is innervated by how many alpha motor neurons? |
|
Definition
|
|
Term
| How many muscle cells can 1 alpha motor neuron innervate within the same muscle? |
|
Definition
|
|
Term
| There are several different muscle fiber types found in skeletal muscle. They are distinguished how? (3) |
|
Definition
Histochemically
Metabolically
Morphologically |
|
|
Term
| Name the 3 types of muscle fibers |
|
Definition
|
|
Term
| How are muscle fibers classified? |
|
Definition
| Based upon the form of myosin |
|
|
Term
|
Definition
|
|
Term
| This muscle fiber type is designated for endurance activities and utilized for aerobic metabolism |
|
Definition
|
|
Term
| This muscle fiber type is found in motor unites which are fatique resistant, slow to contract, and produce low levels of tension. |
|
Definition
|
|
Term
| This type of muscle fiber is utilized for anaerobic (glucose) metabolism and are designed for rapid, powerful activities. |
|
Definition
|
|
Term
| What type of muscle fiber is found in motor units which are quite fatiguable, and produce very rapid, high tension contractions? |
|
Definition
|
|
Term
| Which muscle fiber type has heavy chain myosin, small diameter fibers, and a rich capillary supply? |
|
Definition
|
|
Term
| Which muscle fiber type has abundant mitochondria, aerobic metabolism, red in color, and slow to contract? |
|
Definition
|
|
Term
| Oxidative phosporylation is part of what type of metabolism? |
|
Definition
|
|
Term
| Why is Type I muscle fibers red in color? |
|
Definition
|
|
Term
| This muscle fiber type has low levels of tension and is fatigue reststant. |
|
Definition
|
|
Term
| Give an example of muscles that are made primarily of Type I muscle fibers. |
|
Definition
|
|
Term
| Which muscle fiber type has heavy chain myosin, large diameter fibers, large somas, and a sparse capillary supply? |
|
Definition
|
|
Term
| Which type of muscle fiber has few mitochondria, anaerobic metabolism, rich glycogen stores, white in color, and rapid, high tension contractions. |
|
Definition
|
|
Term
| Why are Type IIb muscle fibers white in color? |
|
Definition
|
|
Term
| This type of muscle fatigues quickly but produces rapid, high tension contractions. |
|
Definition
|
|
Term
| Give an example of muscles that use primarily Type IIb muscle fibers. |
|
Definition
| Gastroc, quads "Power Ms" |
|
|
Term
| This type of muscle fiber has heavy chain myosin, medium diameter fibers, a rich capillary supply, and moderate amounts of mitochondria. |
|
Definition
|
|
Term
| Which muscle fiber type uses aerobic/anaerobic metabolism depending on which one is needed? |
|
Definition
|
|
Term
| Which type of muscle fiber is rich is glyogen stores and is intermediate in tension and fatigue. |
|
Definition
|
|
Term
| Name the 3 categories in which motor units classified. |
|
Definition
Slow Twitch
Fast Twitch Fatigable
Fast Twitch Resistant |
|
|
Term
| The neuron innervating the motor unit determines the motor unit and what? |
|
Definition
|
|
Term
| This type of motor unit contains small, slowly discharging motorneurons that innervate slow, oxidative myofibers (Type I) that are involved in functions such as maintaining posture. |
|
Definition
|
|
Term
| When an activity requires only slight tension, varying numbers of ___ myofibers are activated by the motoneuron. |
|
Definition
|
|
Term
| What type of motor unit contains Type IIa myofibers? |
|
Definition
| Fast Twitch fatigue resistant |
|
|
Term
| What type of motor unit contains Types IIb myofibers? |
|
Definition
|
|
Term
| With an increased demand for tension, speed and power, these large motoneurons begin to fire first. |
|
Definition
| Fast Twitch fatigue resistant |
|
|
Term
| Which an increased demand for tension, speed and power, fast twitch fatigue resistant motor units are fired first then followed by what type? |
|
Definition
|
|
Term
| When a muscle in denervated, what do the muscle fibers tend to convert to? |
|
Definition
|
|
Term
| Which motor unit type consists of slow oxidative skeletal muscle that responds well to repetitive stimulation without getting fatigued. |
|
Definition
|
|
Term
| Give an example of a slow twitch motor unit muscle? |
|
Definition
|
|
Term
| This type of motor unit consists of fast oxidative skeletal muscles which respond well to repetitive stimulation without getting fatigued. |
|
Definition
| Fast Twitch Fatigue Resistant |
|
|
Term
| Give an example of a fast twitch fatigue resistant muscle. |
|
Definition
|
|
Term
| This motor unit type is made of fast glycolytic skeletal muscle that is used for quick bursts of strong activation. |
|
Definition
|
|
Term
| What would you use fast twitch fatiguable motor units for? |
|
Definition
|
|
Term
| Slow twitch motor units innervate what type of muscle fiber? |
|
Definition
|
|
Term
| Fast twitch fatige resistant innervates what muscle fiber? |
|
Definition
|
|
Term
| Fast twitch fatiguable motor units innervate what muscle fiber type? |
|
Definition
|
|
Term
| Name 3 things about motor unit size. |
|
Definition
1. Number of fibers
2. Varies for each muscle
3. Affects function of muscles |
|
|
Term
| Are large motor units for gross or fine motor skills? |
|
Definition
|
|
Term
| Are small motor units for gross or fine motor skills? |
|
Definition
|
|
Term
| In skeletal muscle, ATP production via substrate phosphorylation is supplemented by the availability of what? |
|
Definition
|
|
Term
| Skeletal muscles' capacity to produce ATP via __ __ is further supplemented by the availability of molecular oxygen bound to intracellular myoglobin. |
|
Definition
| Oxidative Phosphorylation |
|
|
Term
|
Definition
|
|
Term
| What do you lose when you increase the size of the motor unit? |
|
Definition
|
|
Term
| What does loss of motor innervation to a motor unit result in? |
|
Definition
| It results in the remaining nerve fibers sending collateral processes to the denervated motor unit |
|
|
Term
| When there is a loss of motor innervation to a motor unit, what ultimately happens? |
|
Definition
| There is an increase of muscle fibers in the motor unit. Muscular function is retained at the expense of control. |
|
|
Term
| What type of muscle fibers are recruited first? |
|
Definition
|
|
Term
| A state of continued contraction of the muscle fiber. |
|
Definition
|
|
Term
| Type of tetanus that occurs when there is no relaxation whatsoever. |
|
Definition
|
|
Term
| Type of tetanus that occurs when there are tiny bits of relaxation that occurs. |
|
Definition
|
|
Term
| Increased number of motor units involved in contraction |
|
Definition
| Summation/Recruitment of motor units |
|
|
Term
| Name 2 things that recruitment allows |
|
Definition
Increased tension
A movement to be continuous and smooth |
|
|
Term
| During motor unit recruitment, do motor units fire in synchrony? |
|
Definition
| No, they fire asynchronously |
|
|
Term
| What does it mean to say that motor units fire asynchronously? |
|
Definition
| While one is contracting, another one may be relaxing |
|
|
Term
| The normal recruitment order begins with the motor unit producing the ___ tension |
|
Definition
|
|
Term
| What is the last of the motor units to be recruited? |
|
Definition
|
|
Term
| How do you decrease the force? |
|
Definition
| By going in reverse order. So starting with the highest tension to the lowest tension |
|
|
Term
| In some rapid movements, that motor units type may not be used? |
|
Definition
|
|
Term
| Increasing stimulus frequency of a single motor neuron |
|
Definition
|
|
Term
| Can be increased by increasing the firing frequency of the motor neuron (and hence the motor unit) |
|
Definition
|
|
Term
| Application of a single action potential results in what in the motor unit? |
|
Definition
| A signle contraction-relaxation cycle |
|
|
Term
| If a second stimulus is applied during the relaxation phase of a twitch what happens? |
|
Definition
| a second contraction-relaxation cycle is immediately initiated |
|
|
Term
| Is the maximum force developed in the second cycle greater or smaller than that developed during the first cycle? |
|
Definition
|
|
Term
| Can 2 contractions summate? |
|
Definition
|
|
Term
| The summation of contractions occurs when stimulation frequencies reach what per second? |
|
Definition
|
|
Term
| As the frequency of stimulation is increased, the developed force continues to sum until what is reached? |
|
Definition
|
|
Term
| Once a maximum developed force is reached, the individual contraction-relaxation cycles fuse to produce a single smooth curve called what? |
|
Definition
|
|
Term
| Occurs in skeletal muscle because the refractory period is short relative to the contraction time. |
|
Definition
|
|
Term
| The time during which the tissue does not respond to a second stimulus. |
|
Definition
|
|
Term
| Where a muscle can be stimulated to contract again before it relaxes from the previous contraction. |
|
Definition
|
|
Term
| Is it rare in a muscle that either multiple motor unit summation or wave summation occur separately from one another? |
|
Definition
|
|
Term
| Since it is rare that multiple motor unit summation occurs separately from one another, what usually occurs? |
|
Definition
| reflex mechanism in the spinal cord normally increase both the impulse rate and the number of motor units firing at the same time. |
|
|
Term
| Even when motor units twitch at very low frequencies, the resulting muscle contraction is smooth although ___. |
|
Definition
|
|
Term
| Fibers in the muscle spindle are in parallel with what? |
|
Definition
|
|
Term
| What is the simplest of all the spinal cord reflexes? |
|
Definition
| Monosynaptic Stretch Reflex |
|
|
Term
| Another term for monosynaptic stretch reflex |
|
Definition
|
|
Term
| What is the peripheral receptor for the monosynaptic stretch reflex? |
|
Definition
|
|
Term
| A sensory receptor found in the skeletal muscle that monitors and assists in regulating muscle movements. |
|
Definition
|
|
Term
| A sensory receptor for the muscle that makes you contract and is enclosed in connective tissue. |
|
Definition
|
|
Term
| Where are infrafusal muscle fibers? |
|
Definition
| Within the muscle spindle |
|
|
Term
| Sends afferent informaiton to the dorsal horn and receives information from the ventral horn from alpha motor neurons and gamma motor neurons. |
|
Definition
|
|
Term
| How many muscle fibers is contained within one muscle spindle? |
|
Definition
|
|
Term
| What is a muscle spindle enclosed in? |
|
Definition
| a connective tissue capsule |
|
|
Term
| Since the fibers of a muscle spindle are enclosed within a capsule, they are called what? |
|
Definition
|
|
Term
| Each muscle spindle is attached at both ends to what? |
|
Definition
|
|
Term
| Each muscle spindle lies in parallel with what? |
|
Definition
|
|
Term
| One end of the muscle spindle is attached to the ___ of the extrafusal fiber, and the other end is attached to the ___. |
|
Definition
|
|
Term
| Does all connective tissue of the muscle blend together and extend to the muscle tendon? |
|
Definition
|
|
Term
| A stretch to the extrafusal muscle with cause the muscle spindle to be stretched. Why? |
|
Definition
| Because they are attached and run parallel with one another |
|
|
Term
| Sensitive to changes in length and the rate of change in length of extrafusal fibers |
|
Definition
|
|
Term
| Each intrafusal muscle fiber is composed to 2 regions. |
|
Definition
Contractile Region
Equatorial Region |
|
|
Term
| Striated muscle located on each end of the fiber |
|
Definition
|
|
Term
| Non-contractile region located in the center of each fiber; cell nuclei are located here |
|
Definition
|
|
Term
| 2 different types of intrafusal fibers exist structurally. |
|
Definition
Nuclear bag fiber
Nuclear chain fiber |
|
|
Term
| How are nuclear bag and nuclear chain fibers differentiated? |
|
Definition
| based upon the shape of the equatorial region |
|
|
Term
| What does the equatorial region look like in the nuclear bag fibers? |
|
Definition
|
|
Term
| What does the equatorial region of a nuclear chain fiber look like? |
|
Definition
|
|
Term
| Each muscle spindle has both __ and __ innervation |
|
Definition
Afferent (sensory)
Efferent (motor) |
|
|
Term
| This type of innervation is supplied by type Ia and type II sensory neurons |
|
Definition
|
|
Term
| What 2 types supply the sensory innervation to the muscle spindle |
|
Definition
|
|
Term
| Axons of the sensory neurons can either wrap around the center (Type __) or terminate near the edges (Type __) of the equatorial region of the intrafusal fibers. |
|
Definition
|
|
Term
| Do the intrafusal fibers stretch when the extrafusal fibers are stretched? |
|
Definition
|
|
Term
| When the intrafusal fibers stretch, what does this compress? |
|
Definition
|
|
Term
| When the intrafusal fibers are stretched, what does this discharge? |
|
Definition
|
|
Term
| This type of neuron responds to changes in length and the rate of change in length of the extrafusal muscle. |
|
Definition
|
|
Term
| This type is most responsive to a quick stretch of the extrafusal muscle |
|
Definition
|
|
Term
| What happens with activation of a Type Ia fiber? |
|
Definition
| A quick, strong contraction of the stretched muscle |
|
|
Term
| This type of fiber innervates the very end of the capsule |
|
Definition
|
|
Term
| This type of fiber comes from the central part of the muscle spindle |
|
Definition
|
|
Term
| The non-contractile part of the muscle spindle |
|
Definition
|
|
Term
| The contractile part of the muscle spindle |
|
Definition
|
|
Term
| This type of fiber is responsive to changes in muscle length and are activated by a slower stretch of the muscle near its physiological limits |
|
Definition
|
|
Term
| What does activation of Type II fibers result in? |
|
Definition
| A maintained contraction of a stretched muscle which lasts as long as the muscle stretch |
|
|
Term
| What are the motor neurons innervating the muscle spindle? They are small neurons with small myelinated axons. |
|
Definition
|
|
Term
| Where are the cell bodies of the gamma motor neurons located? |
|
Definition
| Ventral horn of spinal cord |
|
|
Term
| Where do the axons of gamma motor neurons terminate? |
|
Definition
| On the contractile regions of the intrafusal muscle fibers |
|
|
Term
| Are gamma motor neurons afferent or efferent? |
|
Definition
|
|
Term
| What happens when the gamme motor neurons innervating the muscle spindle are activated? |
|
Definition
| the intrafusal muscle fiber of the spindle contracts and shortens the length of the spindle |
|
|
Term
| What is the role of the gamma system? |
|
Definition
| to permit the muscle spindle to maintain its sensitivity over a wide range of muscle lengths |
|
|
Term
| When the alpha motor neuron fires, causing contraction and shortening of the extrafusal muscle, what happens to the gamma motor neuron? |
|
Definition
| It is activated simultaneously to shorten the muscle spindle |
|
|
Term
| What contracts and shortens when the alpha motor neuron fires? |
|
Definition
|
|
Term
| What contracts and shortens when the gamma motor neuron fires? |
|
Definition
|
|
Term
| True/False: The spindle maintains a length which is proportional to the extrafusal muscle so that the spindle remains sensitive to stretch the extrafusal muscle, regardless of the starting length of the muscle. |
|
Definition
|
|
Term
| Type Ia and II bring sensory information thru ____ then onto the ___ to then synapse on alpha and gamma motor neurons. |
|
Definition
DRG (dorsal root ganglion)
dorsal root |
|
|
Term
|
Definition
|
|
Term
| What is another term for a deep tendon reflex? |
|
Definition
| myotatic or muscle stretch reflex |
|
|
Term
| What does monosynaptic mean? |
|
Definition
|
|
Term
| Composed of sensory (afferent) limb and motor (efferent) limb with a synapse between the two limbs in the ventral horn of the spinal cord |
|
Definition
|
|
Term
| This limb of the DTR is composed of type Ia sensory neuron from the muscle spindle which responds to a quick stretch of the muscle |
|
Definition
|
|
Term
| These fibers synapse in the area of the spinal cord of the ventral horn on alpha motor neurons innervating the stimulated muscle and its agonists |
|
Definition
|
|
Term
| Where a muscle that is already partially stretched is activated by a quick stretch |
|
Definition
|
|
Term
| Where Type Ia fibers synapse on alpha motor neurons innervating the stimulated muscle and its agonists (efferent limb) to get a quick contraction of the muscle |
|
Definition
|
|
Term
| Where in the spinal cords are interneurons located? |
|
Definition
|
|
Term
| During activation of the monosynaptic stretch reflex, a second mechanism is activated. What is it called. |
|
Definition
|
|
Term
| Mediated by collaterals of the Ia afferent and serves to protect the antagonist muscle from being suddenly stretched and opposing the agonist. |
|
Definition
|
|
Term
| At the same time the Ia afferent activates the alpha motor neurons, ___ from the Ia afferent activate Ia inhibitory interneurons in the ventral horn. |
|
Definition
|
|
Term
| Once the inhibitory interneurons are activated what happens? |
|
Definition
| They inhibit the alpha motor neurons of the antagonist muscle |
|
|
Term
| So if the biceps brachii muscle tendon is tapped quickly with a reflex hammer, the biceps muscle (agonist) ___ while the triceps muscle (antagonist) ____. |
|
Definition
|
|
Term
| A second sensory receptor in the muscle |
|
Definition
|
|
Term
| Provides proprioceptive information from skeletal muscle and mediates a reflex whcih protects the muscle from excessive tension which could result in a tear injury |
|
Definition
|
|
Term
| Located at the musculotendinous junction |
|
Definition
|
|
Term
| Composed of a connective tissue capsule through which travel several extrafusal muscle fibers |
|
Definition
|
|
Term
| What registers tension in the muscle (like a contraction or a stretch near the physiological limits of motion) |
|
Definition
|
|
Term
| Once tension is registered by GTO, where is the information conveyed to? |
|
Definition
| inhibitory interneurons in the spinal cord by Ib afferents |
|
|
Term
| Inhibitory interneurons inhibit the alpha motor neurons to the same muscle, resulting in inhibition of the muscle which is known as what? |
|
Definition
|
|
Term
| Anytime you are trying to maintain stability what are you doing? |
|
Definition
|
|
Term
| Walking and stepping on a tack is a situation for what type of reflex? |
|
Definition
|
|
Term
| The flexor withdrawal reflex is initiated by cutaneous input which activates what 2 types of pain fibers? |
|
Definition
| A delta and C pain fibers |
|
|
Term
| Are A delta and C pain fibers afferent or efferent? |
|
Definition
|
|
Term
| A delta and c pain fibers transmit pain information to what? |
|
Definition
|
|
Term
| When the pain fibers send information to the dorsal horn what eventually happens? |
|
Definition
| Activation of excitatory interneurons to synapse on motor neurons to ipsilateral flexor muscles and activation of inhibitory interneurons to synapse on motor neurons of the ipsilateral extensory muscles |
|
|
Term
| Flexion of ipsilateral limb away from the sourse of pain. Inhibition of the extensors on the ipsilateral side. |
|
Definition
|
|
Term
| Brings in sensory information to the dorsal horn to tell flexors to activate and to inhibit the extensory |
|
Definition
|
|
Term
| This reflex occurs simultaneously with the flexor withdrawal reflex |
|
Definition
|
|
Term
| Is the crossed extension reflex necessary if a flexor withdrawal reflex is activated? |
|
Definition
| YES, if it is a weight bearing limb |
|
|
Term
| Activation of the crossed extension reflex are the same or different nociceptors stimulated in the flexor withdrawal reflex? |
|
Definition
|
|
Term
| Nociceptors that activate interneurons in the ipsilateral spinal cord also cause activation of interneurons on the ___ side of the spinal cord |
|
Definition
|
|
Term
| Activation of both ____ interneurons innervating contralateral extensors and ___ interneurons innervating contralateral flexors occurs. |
|
Definition
|
|
Term
| What is the result of the crossed extension reflex? |
|
Definition
| Extension of the contralateral limb to provide support to the body as the ipsilateral limb is flexed away from the pain |
|
|
Term
| Loss of reciprocal inhibition results in co-contraction of muscles. This can be seen in what disorder. |
|
Definition
|
|
