Chapter8 Power Point Lecture

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  • Chapter8 Power Point Lecture

    1. 1. Chapter 8 Movement
    2. 2. The Control of Movement <ul><li>Three categories of vertebrate muscles include: </li></ul><ul><ul><li>Smooth muscles - control the digestive system and other organs </li></ul></ul><ul><ul><li>Skeletal muscles/striated muscles - control movement of the body in relation to the environment. </li></ul></ul><ul><ul><li>Cardiac muscles - heart muscles that have properties of skeletal and smooth muscles </li></ul></ul>
    3. 3. Fig. 8-1, p. 233
    4. 4. The Control of Movement <ul><li>Muscles are composed of many individual fibers. </li></ul><ul><ul><li>The fewer muscle fibers an axon innervates, the greater the precision of movement. </li></ul></ul><ul><li>A neuromuscular junction is a synapse where a motor neuron axon meets a muscle fiber. </li></ul><ul><ul><li>In skeletal muscles, axons release acetylcholine which excite the muscle to contract. </li></ul></ul>
    5. 5. The Control of Movement <ul><li>Movement requires the alternating contraction of opposing sets of muscles called antagonistic muscles . </li></ul><ul><li>A flexor muscle is one that flexes or raises an appendage. </li></ul><ul><li>An extensor muscle is one that extends an appendage or straightens it. </li></ul>
    6. 6. Fig. 8-3, p. 233
    7. 7. The Control of Movement <ul><li>Myasthenia gravis is an autoimmune disease in which the immune system forms antibodies that attack the acetylcholine receptors at neuromuscular junctions. </li></ul><ul><ul><li>Causes the progressive weakness and rapid fatigue of the skeletal muscles. </li></ul></ul>
    8. 8. The Control of Movement <ul><li>Skeletal muscle types range from: </li></ul><ul><ul><li>Fast-twitch - fibers produce fast contractions but fatigue rapidly. </li></ul></ul><ul><ul><li>Slow-twitch - fibers produce less vigorous contraction without fatiguing. </li></ul></ul><ul><li>People vary in their percentage of fast-twitch and slow-twitch muscles. </li></ul>
    9. 9. The Control of Movement <ul><li>Slow-twitch fibers are aerobic and require oxygen during movement and therefore do not fatigue. </li></ul><ul><ul><li>Nonstrenuous activities utilize slow-twitch and intermediate fibers. </li></ul></ul><ul><li>Fast-twitch fibers are anaerobic and use reactions that do not require oxygen, resulting in fatigue. </li></ul><ul><ul><li>Behaviors requiring quick movements utilize fast-twitch fibers. </li></ul></ul>
    10. 10. The Control of Movement <ul><li>The human anatomy is specialized for endurance in running. </li></ul><ul><ul><li>Reflected in the shape of our toes, leg bones, muscles and tendons and the high percentage of slow-twitch muscles in our legs. </li></ul></ul><ul><ul><li>Extensive sweat glands and reduced body hair improve temperature regulation. </li></ul></ul>
    11. 11. The Control of Movement <ul><li>Proprioceptors are receptors that detect the position or movement of a part of the body and help regulate movement. </li></ul><ul><li>A muscle spindle is a kind of proprioceptor parallel to the muscle that responds to a stretch. </li></ul><ul><ul><li>causes a contraction of the muscle . </li></ul></ul><ul><li>Stretch reflex occurs when muscle proprioceptors detect the stretch and tension of a muscle and send messages to the spinal cord to contract it. </li></ul><ul><ul><li>allows fluidity of movement. </li></ul></ul>
    12. 12. Fig. 8-5, p. 235
    13. 13. The Control of Movement <ul><li>The Golgi tendon organ is another type of proprioceptor that responds to increases in muscle tension. </li></ul><ul><li>Located in the tendons at the opposite ends of the muscle. </li></ul><ul><li>Acts as a “brake” against excessively vigorous contraction by sending an impulse to the spinal cord where motor neurons are inhibited. </li></ul>
    14. 14. The Control of Movement <ul><li>Reflexes are involuntary, consistent, and automatic responses to stimuli. </li></ul><ul><li>Infants have several reflexes not seen in adults: </li></ul><ul><ul><li>Grasp reflex - grasps objects placed in the hand. </li></ul></ul><ul><ul><li>Babinski reflex - extends big toe and fans others when the sole of the foot is stroked. </li></ul></ul><ul><ul><li>Rooting reflex - turns head and sucks when cheek is stimulated. </li></ul></ul>
    15. 15. Fig. 8-6, p. 236
    16. 16. The Control of Movement <ul><li>Few behaviors are purely reflexive or non-reflexive and movements vary in their sensitivity to feedback. </li></ul><ul><li>Ballistic movements are movement that once initiated can not be altered or corrected. </li></ul><ul><ul><li>Example: stretch reflex, dilation of the pupil. </li></ul></ul>
    17. 17. The Control of Movement <ul><li>Many behaviors consist of rapid sequences of individual movements. </li></ul><ul><li>Central pattern generators are neural mechanisms in the spinal cord or elsewhere that generate rhythmic patterns of motor output. </li></ul><ul><ul><li>Example: wing flapping in birds. </li></ul></ul>
    18. 18. The Control of Movement <ul><li>A motor program refers to a fixed sequence of movements that is either learned or built into the nervous system. </li></ul><ul><ul><li>once begun, the sequence is fixed from beginning to end. </li></ul></ul><ul><ul><li>Automatic in the sense that thinking or talking about it interferes with the action. </li></ul></ul><ul><ul><li>Example: Mouse grooming itself, skilled musicians playing a piece, or a gymnast’s routine. </li></ul></ul>
    19. 19. Brain Mechanisms of Movement <ul><li>The primary motor cortex is located in the precentral gyrus located in the frontal lobe. </li></ul><ul><li>Axons from the precentral gyrus connect to the brainstem and the spinal cord which generate activity patterns to control the muscles. </li></ul>
    20. 20. Fig. 8-7, p. 240
    21. 21. Brain Mechanisms of Movement <ul><li>Specific areas of the motor cortex are responsible for control of specific areas of the body. </li></ul><ul><ul><li>some overlap exists. </li></ul></ul>
    22. 22. Fig. 8-9, p. 241
    23. 23. Fig. 8-10, p. 242
    24. 24. Brain Mechanisms of Movement <ul><li>The motor cortex can: </li></ul><ul><ul><li>Direct contraction of specific muscles. </li></ul></ul><ul><ul><li>Direct a combination of contractions to produce a specified outcome. </li></ul></ul>
    25. 25. Brain Mechanisms of Movement <ul><li>Other areas near the primary motor cortex also contribute to movement: </li></ul><ul><li>Posterior parietal cortex- respond to visual or somatosensory stimuli, current or future movements and complicated mixtures of a stimulus and an upcoming response. </li></ul><ul><ul><li>Damage to this area causes difficulty coordinating visual stimuli with movement. </li></ul></ul><ul><li>Primary somatosensory cortex- integrates touch information and movement. </li></ul>
    26. 26. Brain Mechanisms of Movement <ul><li>Cells in the following areas are involved in the preparation and instigation of movement: </li></ul><ul><li>Prefrontal cortex : </li></ul><ul><ul><li>Responds to lights, noises and other sensory signals that lead to movement. </li></ul></ul><ul><ul><li>Calculates predictable outcomes of actions and plans movement according to those outcomes. </li></ul></ul>
    27. 27. Brain Mechanisms of Movement <ul><li>Premotor cortex: </li></ul><ul><ul><li>is active during preparation for movement and receives information about a target in space. </li></ul></ul><ul><ul><li>integrates information about position and posture of the body and organizes the direction of the movement in space. </li></ul></ul><ul><li>Supplementary motor cortex: </li></ul><ul><ul><li>Important for organizing a rapid sequence of movements. </li></ul></ul>
    28. 28. Fig. 8-8, p. 241
    29. 29. Brain Mechanisms of Movement <ul><li>The conscious decision to move and the movement itself occur at two different times. </li></ul><ul><li>A readiness potential is a particular type of activity in the motor cortex that occurs before any type of voluntary movement. </li></ul><ul><ul><li>Begins at least 500 ms before the movement itself </li></ul></ul><ul><ul><li>Implies that we become conscious of the decision to move after the process has already begun. </li></ul></ul>
    30. 30. Fig. 8-12, p. 246
    31. 31. The Control of Movement <ul><li>Damage to the primary motor cortex of the right hemisphere leads to the inability to make voluntary movements with the left side. </li></ul><ul><li>Some individuals with this condition experience anosognosia and insist they can and do make voluntary movements. </li></ul><ul><ul><li>In the absence of the motor cortex, the premotor cortex fails to receive feedback if an intended movement was executed. </li></ul></ul>
    32. 32. The Control of Movement <ul><li>Messages from the brain must reach the medulla and spinal cord to control the muscles. </li></ul><ul><li>Axons from the brain are organized into two pathways: </li></ul><ul><ul><li>Dorsolateral tract. </li></ul></ul><ul><ul><li>Ventromedial tract. </li></ul></ul>
    33. 33. Brain Mechanisms of Movement <ul><li>Dorsolateral tract - a set of axons from the primary motor cortex to surrounding areas and the red nucleus and allows control of peripheral areas of the body. (hands, fingers, toes) </li></ul><ul><ul><li>Red nucleus - a midbrain area with output mainly to the arm muscles. </li></ul></ul><ul><li>Axons extend directly to their target neurons in the spinal cord and crosses from one side of the brain to the opposite side of the spinal cord. </li></ul>
    34. 34. Fig. 8-13, p. 246
    35. 35. Brain Mechanisms of Movement <ul><li>Ventromedial tract - set of axons from the primary cortex, supplementary motor cortex, and other parts of the cortex. </li></ul><ul><li>Axons go to both sides of the spinal cord and allow control of: </li></ul><ul><ul><li>muscles of the neck. </li></ul></ul><ul><ul><li>shoulders and trunk. </li></ul></ul><ul><li>Enables movements such as walking, turning, bending, standing up and sitting down. </li></ul>
    36. 36. Brain Mechanisms of Movement <ul><li>The ventromedial tract also includes axons from the midbrain tectum, reticular formation, and the vestibular nucleus. </li></ul><ul><ul><li>Vestibular nucleus - brain area that receives input from the vestibular system. </li></ul></ul>
    37. 37. Brain Mechanisms of Movement <ul><li>The cerebellum is a structure in the brain often associated with balance and coordination. </li></ul><ul><li>Damage to the cerebellum causes trouble with rapid movement requiring aiming and timing. </li></ul><ul><ul><li>Examples: clapping hands, speaking, writing, etc. </li></ul></ul>
    38. 38. Brain Mechanisms of Movement <ul><li>Studies suggest that the cerebellum is important for the establishment of new motor programs that allow the execution of a sequence of actions as a whole. </li></ul><ul><ul><li>The cerebellum may be linked to habit forming and damage may impair motor learning. </li></ul></ul><ul><li>The cerebellum also seems critical for certain aspects of attention such as the ability to shift attention and attend to visual stimuli. </li></ul>
    39. 39. Brain Mechanisms of Movement <ul><li>The cerebellum contains more neurons than the rest of the brain combined and high capacity for information processing. </li></ul><ul><li>The cerebellar cortex is the surface of the cerebellum. </li></ul><ul><ul><li>The cerebellum receives input from the spinal cord, from each of the sensory systems, and from the cerebral cortex and sends it to the cerebellar cortex. </li></ul></ul>
    40. 40. Brain Mechanisms of Movement <ul><li>Neurons in the cerebellar cortex are arranged in precise geometrical patterns: </li></ul><ul><ul><li>Purkinje cells are flat cells in sequential planes. </li></ul></ul><ul><ul><li>Parallel fibers are axons parallel to one another and perpendicular to the plane of Purkinje cells. </li></ul></ul><ul><li>The regular pattern of arrangement allows outputs of well-controlled duration and the greater the number of excited Purkinje cells, the greater their collective duration of response. </li></ul>
    41. 41. Fig. 8-14, p. 248
    42. 42. The Control of Movement <ul><li>The basal ganglia is a group of large subcortical structures in the forebrain important for initiation of behaviors. </li></ul><ul><li>Comprised of the following structures: </li></ul><ul><ul><li>Caudate nucleus. </li></ul></ul><ul><ul><li>Putamen. </li></ul></ul><ul><ul><li>Globus pallidus. </li></ul></ul>
    43. 43. The Control of Movement <ul><li>Caudate nucleus and putamen receive input from the cerebral cortex and send output to the globus pallidus. </li></ul><ul><li>Globus pallidus connects to the thalamus which relays information to the motor areas and the prefrontal cortex. </li></ul><ul><li>Basal ganglia selects the movement to make by ceasing to inhibit it. </li></ul>
    44. 44. The Control of Movement <ul><li>The learning of new skills requires multiple brain areas involved in the control of movement. </li></ul><ul><ul><li>Basal ganglia is critical for learning motor skills, organizing sequences of movement, and learning “automatic” behaviors. </li></ul></ul><ul><ul><ul><li>Example: driving a car </li></ul></ul></ul><ul><ul><li>Relevant neurons in the motor cortex also increase their firing rate and the pattern of activity becomes more consistent as the skill is learned. </li></ul></ul>
    45. 45. Fig. 8-15, p. 249
    46. 46. Disorders of Movement <ul><li>Parkinson’s disease is a neurological disorder characterized by muscle tremors, rigidity, slow movements and difficulty initiating physical and mental activity. </li></ul><ul><li>Associated with an impairment in initiating spontaneous movement in the absence of stimuli to guide the action. </li></ul><ul><li>Symptoms also include depression and memory and reasoning deficits. </li></ul>
    47. 47. Disorders of Movement <ul><li>Caused by gradual and progressive death of neurons, especially in the substantia nigra. </li></ul><ul><li>Substantia nigra sends dopamine-releasing axons to the caudate nucleus and putamen. </li></ul><ul><li>Loss of dopamine leads to less stimulation of the motor cortex and slower onset of movements. </li></ul>
    48. 48. Fig. 8-17, p. 255
    49. 49. Disorders of Movement <ul><li>Studies suggest early-onset Parkinson’s has a genetic link. </li></ul><ul><li>Genetic factors are only a small factor to late on-set Parkinson’s disease (after 50). </li></ul>
    50. 50. Fig. 8-18, p. 255
    51. 51. Disorders of Movement <ul><li>Exposure to toxins are one environmental influence. </li></ul><ul><ul><li>MPTP is converted to MPP which accumulates and destroys neurons that release dopamine. </li></ul></ul><ul><ul><li>MPTP found in some illegal drugs and pesticides. </li></ul></ul>
    52. 52. Disorders of Movement <ul><li>Cigarette smoking and coffee drinking are related to a decreased chance of developing Parkinson’s disease. </li></ul><ul><li>Research suggests marijuana use increases the risk of Parkinson’s disease. </li></ul><ul><li>Damaged mitochondria of cells seems to be common to most factors that increase the risk of Parkinson’s disease. </li></ul>
    53. 53. Disorders of Movement <ul><li>The drug L-dopa is the primary treatment for Parkinson’s and is a precursor to dopamine that easily crosses the blood-brain barrier. </li></ul><ul><ul><li>Often ineffective and especially for those in the late stages of the disease. </li></ul></ul><ul><li>Does not prevent the continued loss of neurons. </li></ul><ul><li>Enters other brain cells producing unpleasent side effects. </li></ul>
    54. 54. Disorders of Movement <ul><li>Other possible treatments for Parkinson’s include: </li></ul><ul><ul><li>Antioxidants. </li></ul></ul><ul><ul><li>Drugs that stimulate dopamine receptors or block glutamate. </li></ul></ul><ul><ul><li>Neurotrophins. </li></ul></ul><ul><ul><li>Drugs that decrease apoptosis. </li></ul></ul><ul><ul><li>High frequency electrical stimulation of the globus pallidus. </li></ul></ul><ul><ul><li>Transplant of neurons from a fetus. </li></ul></ul>
    55. 55. Disorders of Movement <ul><li>Implantation of neurons from aborted fetuses remains controversial and only partially effective. </li></ul><ul><li>Most patients show little or no benefit a year after surgery. </li></ul><ul><li>Patients with only mild symptoms showed the benefit of failing to deteriorate further. </li></ul><ul><li>Stem cells are immature cells grown in tissue culture that are capable of differentiating and are an attractive alternative. </li></ul>
    56. 56. Disorders of Movement <ul><li>Huntington’s disease is a neurological disorder characterized by various motors symptoms. </li></ul><ul><ul><li>affects 1 in 10,000 in the United States </li></ul></ul><ul><ul><li>usually appears between the ages of 30 and 50. </li></ul></ul><ul><li>Associated with gradual and extensive brain damage especially in the caudate nucleus, putamen, globus pallidus and the cerebral cortex. </li></ul>
    57. 57. Disorders of Movement <ul><li>Initial motor symptoms include arm jerks and facial twitches. </li></ul><ul><li>Motors symptoms progress to tremors and writhing that affect the persons walking, speech and other voluntary movements. </li></ul><ul><li>Also associated with various psychological disorders: </li></ul><ul><ul><li>Depression, memory impairment, anxiety, hallucinations and delusions, poor judgment, alcoholism, drug abuse, and sexual disorders. </li></ul></ul>
    58. 58. Disorders of Movement <ul><li>Presymptomatic tests can identify with high accuracy who will develop the disease. </li></ul><ul><ul><li>Controlled by an autosomal dominant gene on chromosome #4. </li></ul></ul><ul><ul><li>The higher the number of consecutive repeats of the combination C-A-G, the more certain and earlier the person is to develop the disease. </li></ul></ul><ul><li>No treatment is effective in controlling the symptoms or slowing the course of the disease. </li></ul>
    59. 59. Fig. 8-22, p. 260
    60. 60. Disorders of Movement <ul><li>A variety of neurological diseases are related to C-A-G repeats in genes. </li></ul><ul><li>For a variety of disorders, the earlier the onset, the greater the probability of a strong genetic influence. </li></ul>
    61. 61. Fig. 8-23, p. 260

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