Term
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Definition
All movement is directed and controlled by centers in the Brain and Spinal Cord
The cell bodies of the neurons that plan, initiate, and direct voluntary movements are located in the motor cortex. |
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| Brainstem centers in the midbrain, pons, and medulla |
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Definition
| Brainstem centers in the midbrain, pons, and medulla control some basic movements and regulate posture |
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| Basal ganglia and cerebellum |
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Definition
| Neurons in the basal ganglia are thought to be involved in the proper initiation of movement, and the cerebellum is involved in the coordination and timing of movements. Both basal ganglia and cerebellum influence the motor cortex via the thalamus. |
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Definition
| are located in the brainstem (for cranial nerve nuclei), and in the spinal cord. The cell bodies of lower motor neurons give rise to axons that form motor nerves and innervate muscles directly |
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| Three principal sources of input converge on the motor neurons: |
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Definition
The supraspinal or descending motor pathways.
Spinal neurons (segmental interneurons and intersegmental neurons).
Primary afferent (sensory) fibers.
the motor neurons are considered the final common path. |
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| The laminae can be grouped into three dorsoventral zones |
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Definition
Dorsal horn (sensory neurons; laminae I-VI)
Intermediate zone (terminations of descending and sensory neurons; upper portion of lamina VII)
Ventral horn (interneurons and motor neurons; lower portion of lamina VII, and laminae VIII and IX). The motor neurons are localized to the motor nuclear columns in lamina IX. |
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Definition
| represented dorsally (posteriorly); extensor muscles ventrally (anteriorly). |
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Definition
| represented laterally; proximal muscles medially. |
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| Cerebral cortical motor areas |
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Definition
| critically involved in voluntary motor behavior as well as in modulating (through brainstem pathways) postural and reflex motor patterns. |
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Definition
| located in several distinct centers in the frontal lobe, and integrate information from somatosensory areas and visual and auditory association areas of the parietal and temporal lobes |
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| four main cortical motor areas located in the frontal lobe |
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Definition
1) Primary Motor Cortex (M1; area 4
2) Supplementary motor area (SMA or M2; a medial part of area 6(b)
3) Lateral premotor cortex (PM; lateral part of area 6(a)):
4) Cingulate motor area (CMA or M3; areas 24 and 25): |
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Term
| 1) Primary Motor Cortex (M1; area 4 |
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Definition
| located at caudal precentral gyrus and into anterior bank of central sulcus (and this is the most important region for Brain and Behavior 2011) |
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Term
| 2) Supplementary motor area (SMA or M2; a medial part of area 6(b) |
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Definition
| located mostly on the medial surface of the hemisphere, above the cingulate sulcus. |
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| 3) Lateral premotor cortex (PM; lateral part of area 6(a |
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Definition
| located just anterior to primary motor cortical strip of precentral gyrus. |
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| 4) Cingulate motor area (CMA or M3; areas 24 and 25 |
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Definition
| located on the medial surface of the hemisphere in the limbic cortex. |
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| The parietal lobe (Somatosensory areas 3, 1, 2, and 5 |
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Definition
| also contributes to the corticospinal tracts but is not located in the frontal lobe) |
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| output of the network of local circuits to motor neurons |
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Definition
| directly coordinates the spatial and temporal patterns of muscular contractions in individual muscle groups. |
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| Common features of cortical motor areas |
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Definition
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Term
| primary motor cortex has a somatotopic representation |
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Definition
| control of the lower extremity is represented medially, the upper extremity is represented on the lateral convexity, and the face mostly laterally. There is a disproportionately large representation of hands, face and mouth. |
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Definition
most immediately related to aspects of motor execution (i.e. muscular contractions).
possess either cutaneous or deep (tendon, joint) somatosensory receptive fields. |
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Term
| two types of corticospinal neuron in layer V of the motor cortex |
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Definition
Large Betz Cells
Small pyramidal cells |
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Term
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Definition
| are involved with ballistic, bidirectional movements; they show all or none firing and are uninfluenced by sensory feedback. They constitute approx. 10% of the pyramidal tract axons |
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Definition
| are involved with slow, accurate, controlled, unidirectional movements, and are under tight somatic sensory control. They show graded firing proportional to the force exerted. These constitute 90% of the pyramidal tract axons |
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Term
| corticomotoneuronal (CM) cells |
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Definition
The majority of corticospinal neurons synapse on interneurons
innervate distal limb musculature such as intrinsic muscles of the hand that are involved in highly skilled movements |
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Term
| primary motor cortex plays essential roles in? |
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Definition
regulating force production
steering movement direction
individuation of finger movements
accurate foot placement during locomotion. |
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Term
| supplementary motor area (M2), lateral premotor cortex (PM), and cingulate motor area (M3) |
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Definition
| higher-order motor areas that receive strong inputs from other higher-order cortical association areas, particularly somatosensory areas (i.e. information concerning extrapersonal space) and visual and auditory assoociation cortices via converging corticocortical inputs |
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| supplementary motor area (M2), lateral premotor cortex (PM), and cingulate motor area (M3) |
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Definition
receive heavy inputs from the basal ganglia via the thalamus.
heavily interconnected with M1, and are engaged in "instructing" M1
project directly to the spinal cord (and brainstem cranial nerve nuclei) via the corticospinal tract |
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Term
| The supplementary motor area (SMA) |
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Definition
located predominantly on the medial surface of the frontal lobe, in Brodmann’s area 6b.
may be two separate motor representations in each SMA representing the two sides of the body (bilateral representation). |
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Definition
| planning and initiating self-generated movements. Its neurons become active not only before actual movement onset or performance but also when one only “thinks” about an upcoming movement |
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Definition
| cause impairment in planning "self-initiated" motor tasks, and, especially, in carrying out motor tasks which involve bimanual coordination (e.g, manipulating the fingers of both hands in order to button a shirt |
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Definition
| cause permanent loss of fine motor control (e.g.of digits), including loss of fractionated (independent) finger movements |
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| The lateral premotor cortex (PM) location |
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Definition
| is located in Broadmann’s area 6a, on the surface of the precentral gyrus, and further rostrally into the precentral sulcus |
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| The lateral premotor cortex (PM) |
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Definition
| at least two distinct motor sub-regions within lateral area 6, the dorsal and ventral premotor cortical areas |
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Term
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Definition
at least two distinct motor sub-regions within lateral area 6, the dorsal and ventral premotor cortical areas
motor representation is mostly contralateral |
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Definition
| cause impairment in planning externally-cued motor tasks, and are called apraxias. |
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Term
| The cingulate motor area (CMA)location? |
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Definition
Located on the medial brain surface, in the limbic association cortex, corresponding to Brodmann’s areas 24 and 25.
Contains at least two motor representations organized into rostral and caudal CMA’s |
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Term
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Definition
process reward information for motor selection
-Contains the upper motor neurons of the facial motor nucleus (dorsal cell columns) that innervates the upper half of the face bilaterally (receives blood supply from the anterior cerebral artery). Therefore, the upper half of the face is spared in patients with central facial palsy after middle cerebral artery strokes (involve internal capsule). |
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Term
| The corticospinal tract (CST) |
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Definition
Fibers arise from many cortical areas (sensory and motor).
Travels through the posterior limb of the internal capsule, the cerebral peduncle, the basis pontis, and the ipsilateral medullary pyramid. |
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Definition
| cross the midline at the pyramidal decussation in the lower medulla and form the lateral corticospinal tract, which extends the entire length of the cord |
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Definition
| small fraction (20%) remains uncrossed or ipsilateral and forms the anterior corticospinal tract. These fibers cross the midline locally via spinal cord commissures, but are situated medially in the spinal cord white matter |
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Definition
| Most axons terminate onto spinal interneurons. Direct monosynaptic connections –called corticomotoneuronal (CM) connections – do exist between corticospinal axons and alpha-motoneurons that control very fine movements, such as individual movements of the fingers, and precision grip |
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Term
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Definition
the basic units of movement
A motor neuron and all of the muscle fibers to which it connects |
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| motor neuron pools for a muscle |
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Definition
| grouped together into rod-shaped clusters that run parallel to the long axis of the cord for one or more spinal cord segments. |
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| the size principle of motor neuron recruitment. |
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Definition
| The motor units are activated (or recruited) in an orderly manner, according to size. Small motor units are recruited first, followed by large ones. |
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Term
| Skeletal muscle is comprised of two types of muscle fibers |
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Definition
Extrafusal, which are force-generating
Intrafusal , which have no direct role in force generation, but rather are part of the muscle spindle |
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Term
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Definition
innervate extrafusal muscle fibers
regulate skeletal muscle contraction
to produce movement |
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Term
| Gamma (or fusimotor) motor neurons |
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Definition
innervate intrafusal muscle fibers of muscle spindles.
play no direct role in force-generation, but control the sensitivity of one type of sensory receptor in the muscle – the muscle spindle, a sensory receptor that monitors changes in muscle length. |
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Term
| two complex sensory receptors (Muscle spindles and Golgi Tendon organs) |
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Definition
| constantly monitor length and tension changes of muscle during movement and provide feedback to the alpha motor neuron for adjustment of muscle contraction. Both are mechanoreceptors, and are intimately concerned with reflex regulation of muscular activity. |
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Term
| Muscle spindles are stretch receptors |
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Definition
| activated by changes in muscle length and rate of change of length. Muscle spindles are fusiform (spindle-shaped) structures which are arranged in parallel with the extrafusal muscle fibers surrounding them. |
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Term
| The muscle spindles have two functional regions |
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Definition
polar regions are composed of intrafusal muscle fibers and are contractile. They receive motor innervation from gamma-motoneurons
-equatorial region is non-contractile and receives sensory innervation from
Group Ia and Group II sensory afferent fibers |
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Term
| Contraction of the polar intrafusal fibers (via gamma-motoneuron activation |
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Definition
| changes the tension on the central region, and in this way, gamma motoneurons can control the sensitivity of the spindle. |
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Term
| Golgi Tendon Organs (GTOs) |
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Definition
Respond to changes in tension at the myotendinous junction during muscle contraction
Discharge frequency is proportional to the degree of force exerted on the myotendinous junction |
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Term
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Definition
connected in series with the extrafusal muscle fibers
result GTOs are exquisitely sensitive to increases in muscle tension that arise from muscle contraction but, unlike spindles, are relatively insensitive to passive stretch |
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Term
| Alpha-gamma co-activation |
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Definition
| preserve the sensitivity of the muscle spindle (and therefore, its usefulness as a detector of muscle length and its rate of change) by maintaining tension on the spindle even when a muscle is shortening (during contraction). |
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Term
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Definition
| a motor response to a sensory stimulus, and does not normally require “volition”. A sensory stimulus produces impulses in sensory (afferent) fibers that ultimately, through direct synaptic action ("monosynaptic") or indirectly via interneurons ("di- or multisynaptic") activates a pool of motor neurons to contract the muscle. |
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Term
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Definition
| (also known as stretch or myotactic reflex) is a simple reflex involving an excitatory pathway between sensory nerve fibers from a muscle spindle (form the afferent arc) and alpha motor neurons (form the efferent arc) that innervate the same muscle |
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