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66 Cards in this Set

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what is a motor unit/
one motor neuron together with all the skeletal muscle fibers this neuron innervates.
What is a motor neuron pool?
all the motor neurons that supply a given muscle
what type of contractions do most skeletal muscles execute?
isometric
in motor control hierarchy, what is the "higher" centers"? what structures are involved?
forms complex plans according to individual's intention and communicates with middle level via "command neurons";
structures involved include areas of memory, emotions, association cortex.
in motor control hierarchy, what is middle level? what structures are involved?
convert plans received fom highest level to small motor programs; program transmitted through descending pathways to lowest control level. structures include sensorimotor cortex, cerebellum, basal nuclei, brainstem nuclei
SPECIFY INDIVIDUAL POSTURES AND MOVEMENTS NEEDED TO CARY OUT INTENDED ACTION. ALSO RECEIVE AFFERENT SIGNALS.
in motor control hierarchy, what is lowest level? what structures are involved?
aka local level
specifies tension of muscles and angle of joints at specific times to carry out program.
structures include the level of brainstem or spinal cord from which motor neurons exit.
where do the descending pathway to the local level arise?
only in sensorimotor cortex and brainstem.
what is proprioceptions? what level of hierarchy is it involved?
afferent information about the position of the body and its parts in space. the middle level is constandly updated afferently about the movement taking place.
is motor behavior voluntary or involuntary? how can voluntary become involuntary?
both. increase frequency of action
besides relaying instructions to motor neurons from higher motor control centers, what else do local control systems do?
play a major role in adjusting motor unit activity to unexpected obstacles to movement and to painful stimuli in surrounding environment.
where do local control centers get information about the local environment?
from afferent fibers froom sensory receptors in muscles, tendons, joints, and skin
where do MOST synaptic inputs to motor neurons from descending pathway and afferent neurons come from?
do no directly go to motor neurons but interneurons
where are the sensory receptors from where the afferent fibers bring information?
1. in muscles controlled by motor neurons
2. nearby muscles, such as those having antagonistic axns
3. in tendons, joints, skin
what type of informations is relayed by sensory receptors on afferent neurons?
length and tension of muscles, movement of joints, and effect of movement on overlying skin
what do stretch receptors monitor? where are they found?
absolute muscle length and changes in muscle length. found in muscle spindle.
what is a muscle spindle?
a receptor organ made up of specialized muscle fibers (muscle cells) that detects stretch of skeletal muscles.
what are intrafusal fibers?
the modified muscle cells within the muscle spindle
what are extrafusal fibers?
skeletal muscle cells that form the bulk of the muscle and generate its force and movement
what are the two types of stretch receptors in a muscle spindle?
nuclear chain fibers: responds in direct proportion to muscle length
nuclear bag fibers: responds to magnitude of strect and speed with which it occurs
what is the physical relationship between intrafusal and extrafusal fibers? how does the physical relationship explain how they work?
the muscle spindles with the intrafusal fibers are PARALLEL to extrafusal fibers: an external force stretching the muscle also pulls on intrafusal fibers, stretching them and activiation their receptor endings
what increase or decreases the rate of firing in stretch receptors?
the more or faster the muscle is stretched, the greater the rate of reeptor firing. contraction of the extrafusal fibers and the resultant shortening of the muscle remove tension on the spindle and slow the rate of firing in the stretch receptor.
what is a stretch flex? give an example.
a monosynaptic reflex mediated by the stretch receptor in which muscle stretch causes contraction of that muscle: direct relationship
example: knee jerk
what is reciprocal innervation?
inhibition of motor neurons activating muscles wose contraction would oppose an intended movement
what are synergistic muscles?
muscles whose contraction assists the intended motin
what type of pathway provides information about the conscious perception of the position of the limb?
ascending pathway (neural pathway that goes to the brain)
during contraction the stretch receptors greatly reduce the axn potential and there can be no indication of any further changes in muscle length the whole time the muscle is shortening. describe the mechanism the exists to prevent this loss of information.
the two ends of each intrafusal muscle cells are stimulated to contract during the shortening of the extrafusal fibers. this maintains tension in the central region of the intrafusal fiber where the stretch receptors are located. different motor neurons supply the intra and extra-fusal fibers in response to activation but they are coactivated.
what are alpha motor neurons? what are gamma motor neurons?
alpha are motor neurons controlling the extrafusal muscle fibers and are larger while gamma innervate intrafusal fibers and are smaller
name factors the influence muscle tension.
muscle length
the load on the muscles
degree of muscle fatigue
how is feedback related to muscle tension relatyed to motor control system?
vision
receptors that monitor tension
what are the Golgi tendon organs and where are they located?
receptors that monitor tension; located in tendons near their junction with muscles
what is a muscle spindle?
a receptor organ made up of specialized muscle fibers (muscle cells) that detects stretch of skeletal muscles.
what are intrafusal fibers?
the modified muscle cells within the muscle spindle
what are extrafusal fibers?
skeletal muscle cells that form the bulk of the muscle and generate its force and movement
what are the two types of stretch receptors in a muscle spindle?
nuclear chain fibers: responds in direct proportion to muscle length
nuclear bag fibers: responds to magnitude of strect and speed with which it occurs
what is the physical relationship between intrafusal and extrafusal fibers? how does the physical relationship explain how they work?
the muscle spindles with the intrafusal fibers are PARALLEL to extrafusal fibers: an external force stretching the muscle also pulls on intrafusal fibers, stretching them and activiation their receptor endings
what increase or decreases the rate of firing in stretch receptors?
the more or faster the muscle is stretched, the greater the rate of reeptor firing. contraction of the extrafusal fibers and the resultant shortening of the muscle remove tension on the spindle and slow the rate of firing in the stretch receptor.
what is a stretch flex? give an example.
a monosynaptic reflex mediated by the stretch receptor in which muscle stretch causes contraction of that muscle: direct relationship
example: knee jerk
what is reciprocal innervation?
inhibition of motor neurons activating muscles wose contraction would oppose an intended movement
what are synergistic muscles?
muscles whose contraction assists the intended motin
what type of pathway provides information about the conscious perception of the position of the limb?
ascending pathway (neural pathway that goes to the brain)
during contraction the stretch receptors greatly reduce the axn potential and there can be no indication of any further changes in muscle length the whole time the muscle is shortening. describe the mechanism the exists to prevent this loss of information.
the two ends of each intrafusal muscle cells are stimulated to contract during the shortening of the extrafusal fibers. this maintains tension in the central region of the intrafusal fiber where the stretch receptors are located. different motor neurons supply the intra and extra-fusal fibers in response to activation but they are coactivated.
what are alpha motor neurons? what are gamma motor neurons?
alpha are motor neurons controlling the extrafusal muscle fibers and are larger while gamma innervate intrafusal fibers and are smaller
name factors the influence muscle tension.
muscle length
the load on the muscles
degree of muscle fatigue
how is feedback related to muscle tension relatyed to motor control system?
vision
receptors that monitor tension
what are the Golgi tendon organs and where are they located?
receptors that monitor tension; located in tendons near their junction with muscles
what effects can the branches of Golgi tendon organ have?
they can cause widesprad inhibitin of the contracting muscle via interneurons and they can stimulate the motor neurons of the antagonistic muscles.
what is the difference between muscle spindle and Golgi tendon organ? what type of information does he convey?
muscle spindle provides local homeostatic control of muscle LENGTH while the Golgi tendon organ provides local homeostatic control of muscle TENSION. both convey afferent information from the activated muscle and to local motor control systems.
what are the functions of the cerebral cortex and in what level of motor control hierarchy does it play a role?
functions in planning and ongoing control of voluntray movements, function in both the highest and middle levels of motor control hierarchy.
what is the sensorimotor cortex?
all areas of cerebral cortex that play a role in skeletal muscle control
what parts of the brain are involved in learning skilled movements?
subcortical and brainstem nuclei
what part of the brain is the basal nuclei a part of? what is its function?
subcortical nuclei:
associated with body movement
what is the major physiological deformity in Parkinson's disease?
input to the basal nuclei and substantia nigra is diminished
what is substantia nigra
region in subcortical nucleus that releases dopamine and suppresses extraneous muscle activity
what happens to the substantia nigra during Parkinson's disease?
substantia nigra neurons degenerate and the amount of dopamine they deliver to the basal nuclei is reduced. this decreases the subsequent activation of the sensorimotor cortex.
what are the types of drugs used to treat Parkinson's disease?
1.agonists of dopamine inhibitor
2.inhibitors of enzymes that metabolize dopamine at synapse
3.precursors of dopamine (L-dopa)
why can't dopamine be utilized as a medicine against Parkinson's disease?
cannot cross the blood-brain barrier and has many side effects
what physiological process is the cerebellum involved? from where does it receive information?
influences posture and movement; receives info from sensorimotor cortex and vestibular system (eyes, ears, skin, muscles, joint, tendons)
what is the specific role of the cerebellum in motor function?
1. provide timing signals to the cerebral cortex and spinal cord
2. helps coordinate movements that involve several joints
3. compares information about what muscles should be doing with what they are doing
what are the symptoms of a cerebellar disease?
movement cannot be made smoothly
unstable posture
difficulty in learning new motor skill
describe where the nerve fibers of the corticospinal pathways have their cell bodies and where they terminate.
cell bodies in sensorimotor cortex and terminate in spinal cord.
describe the anatomical structure that explains how the left side of the body control the right of the body.
the corticospinal pathway passes over the medulla oblongata near the junction of the spinal cord and brainstemwhere the corticospinal fibers cross the spinal cord to descend on the opposite side.
where does the corticobulbar pathway begin and end? what does this pathway control?
begins in the sensorimotor cortex and ends in the brainstem. either directly or indirectly via interneurons, the pathway innervates the muscles of the eye, face, tongue, and throat.
what are the major body parts that are controlled by the corticobulbar and corticospinal pathways?
corticobulbar controls voluntary movement of the muscles of the head and neck and the corticospinal pathway controls muscles in the rest of the body.
what structures are regulated by the brainstem pathway?
muscles of the trunk for upright posture, balance and walking
what is the greatest difference between the corticospinal pathway and brainstem pathway?
corticospinal pathway controls muscles involved in fine, isolated movements (fingers) while brainstem pathway is involved with coordingation of the large muscle groups used in maintenance of upright posture
define muscle tone how does it originate?
resistance of skeletal muscle to stretch and is due bot to the passive elastic properties of muscles and joints and to the degree of ongoing alpha motor neuron activity