Movement quiz notes PDF

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Movement Vertebrate muscles fall into three categories: Smooth muscles- control the digestive system and other organs Skeletal or striated muscles- control movement of the body in relation to the environment Cardiac muscle- control the heart -although each muscle fiber receives information from only one axon, a given axon may innervate more than one muscle fiber Neuromuscular junction- a synapse between a motor neuron axon and a muscle fiber -In skeletal muscles, every axon releases ACH at the neuromuscular junction, and ACH always excites the muscle to contract -the muscle simply relaxes when it receives no message to contract Antagonistic muscles- opposing sets of muscles Example: Flexor- brings hand toward your shoulder, Extensor- straightens the arm Fast twitch fibers- fast contractions and rapid fatigue -anaerobic using reactions that do not require oxygen at the time, but need oxygen for recovery Slow twitch fibers- less vigorous contractions and no fatigue -rely on slow twitch and intermediate fibers for nonstrenuous activities -do not fatigue because they are aerobic using oxygen during their movements Proprioceptor- a receptor that detects the position or movement of a part of the body -muscle proprioceptor detect the stretch and tension of a muscle and send messages that enable the spinal cord to adjust its signals One kind of proprioceptor is a muscle spindle- a receptor parallel to the muscle that responds to a stretch. When stretched, its sensory nerve sends a message to a motor neuron in the spinal cord which in turn sends a message back to the muscles surrounding the spindle, causing a contraction -this reflex provides for negative feedback -Proprioceptors not only control important reflexes, but also provide the brain with information Golgi tendon organs- also proprioceptors, respond to increases in muscle tension. -located in the tendons at opposite ends of a muscle, they act as a brake against an excessively vigorous contraction -their impulses travel to the spinal cord, where they excite interneurons that inhibit the motor neurons Stretch reflex- caused by a stretch, it does not produce one Reflexes- consistent automatic responses to stimuli Ballistic movement- such as a reflex, it is executed as a whole: once initiated, it cannot be altered Central pattern generators- neural mechanisms in the spinal cord that generate rhythmic patterns of motor output -the stimulus that activates a central pattern generator does not control the frequency of the alternating movements

Motor program- fixed sequence of movements -yawning Primary motor cortex- the precentral gyrus of the frontal cortex, just anterior to the central sulcus, direct electric stimulation elicits movement -the motor cortex does not send messages directly to the muscles, its axons extend to the brainstem and spinal cord, which generate the impulses that control the muscles Cerebral cortex -particularly important for complex actions such as talking or writing -the output of a given neuron influences movements of the hand, wrist, and arm, and not just a single muscle -the motor cortex orders an outcome and leaves it to the spinal cord and other areas to find the right combination of muscles Posterior parietal cortex- one of the first areas to become active in planning a movement -monitors the position of the body relative to the world Supplementary motor cortex- also important for planning and organizing a rapid sequence of movements Premotor cortex- most active immediately before a movement -receives information about the target to which the body is directing its movement, as well as information about the bodies current position and posture Prefrontal cortex- also active during a delay before a movement -stores sensory information relevant to a movement, also important for considering the probable outcomes of possible movements Anti-saccade task- a voluntary eye movement from one target to another -performing this task gradually improves over age, and requires sustained activity in parts of the prefrontal cortex and basil ganglia before seeing the wiggling finger Mirror neurons- active in both during preparation for a movement and while watching someone else perform the same or similar movement -idea that they might be important for understanding other people, and identifying with them and imitating them Corticospinal tracts- paths from the cerebral cortex to the spinal cord -we have two tracts: lateral and medial corticospinal tracts, both contribute in some way to nearly all movements, but a movement may rely on one tract more than the other Lateral corticospinal tract- pathway of axons from the primary motor cortex, surrounding areas, and the red nucleus -axons of the lateral tract extend directly form the motor cortex to their target neurons in the spinal cord. In bulges of the medulla called pyramids, the lateral tract crosses to the contralateral side of the spinal cord and controls movement sin peripheral areas such as hand and feet Red nucleus- a midbrain area that is primarily responsible for controlling arm muscles

Medial corticospinal tract- includes axons from many parts of the cerebral cortex, not just the primary motor cortex and its surrounding areas -also includes axons from the midbrain tectum, reticular formation, and the vestibular nucleus -axons of the medial tract go to both sides of the spinal cord, not just the contralateral side -controls mainly the muscles of the neck, shoulders, trunk and therefore bilateral movements as walking, turning, bending Vestibular nucleus- a brain area that receives input from the vestibular system Cerebellar damage does not impair continuous motor activity -trouble with initial rapid movement however -damage to this area resembles alcohol intoxication: clumsiness, slurred speech and inaccurate eye movements -Cerebellum appears critical for certain aspects of attention Basal ganglia- applies collectively to a group of large subcortical structures in the forebrain -particularly important for spontaneous, self initiated behaviors, critical for learning new habits -includes caudate nucleus, putamen, and globus pallidus -Caudate nucleus and putamen are known as the striatum or dorsal striatum Striatum- receives input from the cerebral cortex and substantia nigra and sends its outputs to the globus pallidus, which then sends output to the thalamus which relays it to the frontal cortex Many cells in the basil ganglia respond to the reward value of a possible action, they respond more strongly in the presence of signals indicating that responding will produce a larger or more certain reward -stimulating dopamine type 1 receptors in the direct pathway of the striatum produces the same behavioral effects that an increase in reward does Readiness potential- motor cortex produces this kind of activity before any voluntary movement Parkinson’s disease- main symptoms include muscle tremors, slow movements, and difficulty initiating physical and mental activity, results from a dopamine deficiency -immediate cause is the gradual loss of neurons in the substantia nigra and therefore a loss of dopamine releasing axons to the striatum -with the loss of this input, the striatum decreases its inhibition of the globus pallidus which therefore increases its inhibitory input to the thalamus resulting in less vigorous voluntary movements MPTP- a chemical that the body converts to MPP, which accumulates in and then destroys neurons that release dopamine, partly by impairing the transport of mitochondria from the cell body to the synapse L- Dopa- a precursor to dopamine that does cross the barrier, might be a good treatment for Parkinson’s

-does not replace other transmitters that are also depleted Huntington’s disease- severe neurological disorder -motor symptoms usually begin with arm jerks or facial twitches, then tremors spread to other parts of the body and develop into writhing -people loss the ability to learn or improve motor skills -this disorder is associated with gradual, extensive brain damage especially in the basal ganglia but also in the cerebral cortex Huntingtin- protein coded that is throughout the body although its mutant form produces no harm outside of the brain -within the brain it occurs inside neurons, not on their membranes, and it impairs the neuron in several ways...