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Neural Bases Exam II
Neuromotor Control of Speech and Movement (Lecture 4)
| Question | Answer |
|---|---|
| All motor activity is regulated by interaction among | higher and lower levels of the nervous system |
| HIGHER LEVELS of the nervous system | Cerebral cortex, Basal ganglia, Thalamus, Cerebellum |
| LOWER LEVELS of the nervous system | Brainstem and Spinal cord |
| In general, NEURAL impulses from higher levels may ________, ________, or ________ functions at the brainstem and spinal cord | initiate, inhibit, or facilitate |
| The 5 components of motor control | Final Common Pathway (LMN), Direct Control System (pyramidal, UMN, corticobulbar and corticospinal tracts), Indirect Control System (extrapyramidal), Basal Ganglia Control Circuit and Cerebellar Control Circuit |
| Final common pathway is also known as | lower motor neuron |
| Major players of the Lower motor neuron (efferent) | Alpha motor neurons,Gamma motor neurons, Neuromuscular junction, Muscle fibers (Extrafusal and Intrafusal), Sensory receptors and afferents, Muscle Spindles, Golgi Tendon Organs |
| Alpha and gamma-motor neurons receive motor impulses directly from | the motor centers in the forebrain and brainstem |
| Alpha motor-neurons (α-MNs) are | large lower motor neurons of the brainstem and spinal cord. |
| The primary output of α-MNs is to | extrafusal fibers of skeletal muscle and are directly responsible for initiating their contraction. |
| Other fibers from α-MNs synapse on Renshaw cells which are | inhibitory interneurons that synapse on the α-MN and limit its activity in order to prevent muscle damage |
| Alpha motor neurons receive input from a number of sources, including | upper motor neurons, sensory neurons, and interneurons. |
| Gamma motor neurons | innervate intrafusal muscle fibers of muscle spindles |
| The primary role of gamma lower motor neurons | to regulate the length of the muscle spindle fibers |
| Gamma motor-neurons are controlled by | synaptic input from the brainstem reticular formation and the vestibular system |
| The gamma-efferent fibers contract | the end portions of the intrafusal muscle fibers, passively stretching the central parts of the muscle spindles that are inside |
| As the spindles stretch, a surge of sensory input (afferent projections) is directed to the alpha motor neurons, which in turn | reflexively contracts the muscle mass (extrafusal muscle fiber)to progressively decrease the muscle length |
| Renshaw Cells (Interneurons) are | mostly inhibitory, association cells interconnecting cell bodies within sensory and motor neuron pools |
| The Renshaw cell receives axonal collaterals from nearby motor neurons, inhibiting the activity of the same or related adjacent alpha motor neurons to | cease muscle contraction |
| The recurrent inhibition by the Renshaw cell | facilitates and sharpens the activity of the projecting motor neuron |
| Muscle spindles | detect the degree and rate of change in muscle length and help maintain muscle tone |
| Muscles consist of | extrafusal and intrafusal fibers |
| Extrafusal fibers make up the large mass of the skeletal muscle; they are | attached to bone by fibrous tissue extensions called tendons and are controlled by alpha motor neurons |
| Intrafusal fibers, which contained in muscle spindles, are | attached to the extrafusal fibers and are controlled by gamma-motor neurons |
| True or False: Both ends of the intrafusal fibers contract, but the central region does not | true |
| Golgi tendon organs | innervate the tough tissues that attach muscles to bones and permits the muscle to stretch and prevents injury caused by excessive contraction |
| Muscle spindles are buried among | the extrafusal fibers of the muscle |
| Muscle spindles send information about muscle stretch to | the CNS |
| Intrafusal fibers are found in | muscle spindles |
| Gamma-motor neurons from CNS innervate | intrafusal fibers |
| One way to initiate a muscle contraction is through the stimulation of | alpha-motor neurons. |
| Activating alpha motor neurons causes | the extrafusal muscle fibers to contract. With contraction of the extrafusal fibers of the muscle, the intrafusal fibers become slack and consequently |
| To correct this impaired spindle sensitivity, the ______, ______, ______ reflexively discharge gamma-motor neurons | rubrospinal, reticulospinal, and vestibulospinal |
| Gamma-motor neurons,which contract the end portions of the intrafusal fibers | straighten the spindles and restore their sensitivity to muscle length(stretch). |
| The alpha motor neuron sends impulses to contract (shorten) the extrafusal muscle fibers via | the neuromuscular junction |
| Gamma-motor neurons prevent slackening of intrafusal fibers in response to | contraction of extrafusal fibers |
| Stimulated alpha-motor neuron contracts | extrafusal fibers |
| Activation of gamma-motor neuron contracts intrafusal fibers | restoring spindle sensitivity |
| The common element in all stretch reflexes is | that the stretched muscle contracts after a brief delay |
| Stretch or Myotactic Reflex | 1. Sensory from the stretched muscle spindles send afferent projections to activate the a-mns in L3 in the spinal cord. 2. The a-mns efferent fibers to the muscle cause a quick contraction of the extrafusal muscle fibers restoring it to resting position |
| Patellar Tendon reflex | Stretch or Myotactic Reflex |
| protective response to pain or painful stimuli seen when one touches a hot pan or steps on a nail | Withdrawl or Flexor Reflex |
| The neural mechanism of the limb-withdrawal reflex involves | pain receptors in the skin, afferent pain fibers, substantia gelatinosa, interneurons and alpha-motor neurons |
| True or False: A withdrawal reflex generally begins even before one is aware of the painful stimulus because the afferent information triggers a spinal response before the ascending signal of pain reaches the forebrain | True |
| Arm flexion | Example of Withdrawl or Flexor Reflex |
| Reciprocal inhibition is when | one muscle contracts while the paired muscle extends because it is inhibited from simultaneous contraction |
| Crossed Or Intrasegmetal Extensor Reflex is considered a genetically programmed protective behavior for survival because | it moves the entire body away from the painful stimulus |
| Crossed Or Intrasegmetal Extensor Reflex is a complex movement pattern in which | withdrawal(contract) of the limb on one side is accompanied by the activation of motor neurons to extend the agonistic muscle on the opposite side (ipsilateral) of the body |
| Large lesions result in LMN Syndrome in which | muscle fibers are disconnected from motor efferents and thus cannot receive descending cortical impulses and reflexive sensory input. |
| Clinical signs of LMN Syndrome occur | unilateral to the lesion for both reflexes and voluntary motor movements |
| flaccid paralysis, absent reflexes, muscular fibrillation (spontaneous firing)/ fasciculations, atrophy (silence of firing and shrinking of the muscle), paresis are clinical signs of | LMN Syndrome |
| Sudden onset of paralysis of all ipsilateral upper and lower facial muscles; a LMN syndrome that paralyzes the entire side of the face | Bell's palsy |
| Glossopharyngeal nerve (CV IX) serves | both sensory and motor functions |
| Direct, voluntary skilled movement | DIRECT ACTIVATION PATHWAY (Pyramidal System) |
| Corticospinal and Corticobular tracts are associated with | DIRECT ACTIVATION PATHWAY (Pyramidal System) |
| One of the major descending pathways originating in the motor cortex of the brain to terminate at the α-MNs of the spinal cord | The corticospinal tract |
| Provides a mechanism for the cerebral cortex mediate voluntary movements of the skeletal muscles | The corticospinal tract of the DIRECT ACTIVATION PATHWAY (Pyramidal System) |
| Where 90% of the corticospinal fibers cross and form the lateral corticospinal tract | at the medulla |
| Where 10% of the coriticospinal fibers cross in the spinal cord before synapsing on the ventral horn with alpha motor neuron and internuncial cells is called | the anterior corticospinal tract |
| Cortex-Corona Radiata-Post. limb of internal capsule-Pes Pedunculi-Ventral pons-Pyramids of the medulla-a. Lateral corticospinal tract (90%)-b. Anterior corticospinal tract (10%)-Synapse alpha motor neurons to regulate muscle activity | ORDER OF CORTICOSPINAL TRACT |
| Originates in the cortex and terminates in the bulbar area (medulla and adjacent brainstem areas) | The corticobulbar tract |
| It controls skilled and fine movements but exclusively for the head and face | The corticobulbar tract |
| Fibers arise from the lower 1/3 of the motor cortex-Corona Radiata-through genua of internal capsule-Pes Pedunculi-Cross midline, (decussate) at vaious points-Terminate on specific motor nuclei in brainstem | ORDER OF CORTICOBULBAR TRACT |
| Maintains balanced posture, smooth and coordinated movement, muscle tone, supportive to voluntary movement, regulates reflexes | INDIRECT ACTIVATION PATHWAY (Extrapyramidal System) |
| Multiple synapses before providing input to LMN, EVENTUALLY INFLUENCES GAMMA MOTOR NEURONS | INDIRECT ACTIVATION PATHWAY (Extrapyramidal System) |
| Damage results in increased tone, increased reflexes, spasticity and loss of skilled movements | INDIRECT ACTIVATION PATHWAY (Extrapyramidal System) |
| Speech: unilateral UMN dysarthria and spastic dysarthria is result of damage to | INDIRECT ACTIVATION PATHWAY (Extrapyramidal System) |
| Vestibulospinal, Corticorubral, and Corticoreticular Tracts are associated with | INDIRECT ACTIVATION PATHWAY (Extrapyramidal System) |
| Vestibular nuclei(on floor of 4th ventricle)-terminate on Alpha Motor Neurons and Gamma Motor Neurons | order of the Vestibulospinal tract of Indirect Activation pathway |
| Function: keeps head stable | Vestibulospinal tract of Indirect Activation pathway |
| Cortex–red nucleus (midbrain)-it becomes the rubrospinal tract-spinal or Cranial Nerve | order of the Corticorubral Tract of the Indirect Activation Pathway |
| Function: Keeps upright against gravity | Corticorubral Tract of the Indirect Activation Pathway |
| Projects from cortex (motor, premotor and sensory areas) to midbrain to reticular formation | Corticoreticular Tract of the Indirect Activation Pathway |
| A field of cells in midbrain, pons and medulla crucial for muscle tone | The reticular formation |
| Results in increased muscle tone | Stimulation of facilitory reticular areas (midbrain, pons, medulla) |
| Results in decreased muscle tone | Stimulation of inhibitory reticular area (lower medial medulla) |
| Reticulospinal tract synapses on | gamma motor neurons in cranial and spinal nerve nuclei |
| It regulates swallowing by integrating the sensorimotor functions of the trigeminal nerve (CN V), facial nerve (CN VII), glossopharyngeal nerve (CN IX), vagus nerve (CN X) and hypoglossal nerve (CNXI) | Reticulospinal tract of Indirect Activation Pathway (Extrapyramidal System) |
| Gives movement force, timing and precision | Cerebellar Circuit |
| Refines movement | Basal Ganglia Circuit |
| Akinesia, Bradykinesia, Decreased excursion of movement, Tremor? result from | too much inhibition (hypokinetic) in the Basal Ganglia Circuit |
| Athetosis, Ballism, Chorea, Dyskinesia | Too much excitation (hyperkinetic) in the Basal Ganglia Circuit |
| Ataxia, Dysdiadochokinesis, Ataxic dysarthria, Dysmetria, Intention tremor, Hypotonia, Rebounding, Disequilibrium | Cerebellar issues |
Created by:
jrschwa1
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