1 / 118

Chapter 50 Disorders of Motor Function

Chapter 50 Disorders of Motor Function. Motor Cortex. Highest level of motor function Precise, skillful, intentional movements Speech, flexor muscles of limbs, etc. Controlled by the primary, premotor and supplementary motor cortices in the frontal lobe

robyn
Download Presentation

Chapter 50 Disorders of Motor Function

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 50Disorders of Motor Function

  2. Motor Cortex • Highest level of motor function • Precise, skillful, intentional movements • Speech, flexor muscles of limbs, etc. • Controlled by the primary, premotor and supplementary motor cortices in the frontal lobe • Receives information from the Thalamus, cerebellum and basal ganglia

  3. Motor Cortex Primary motor cortex Responsible for execution of a movement. Adjacent to central sulcus Motor Humunculus Premotor cortex (areas 6 and 8) Generates intricate plan of movement. Throwing a ball or picking up a fork

  4. Motor Cortex Supplementary motor cortex • Involved in the performance of complex, skillful movements • (areas 6 and 8)

  5. Homunculus

  6. Basal Ganglia • A group of deep, interrelated subcortical nuclei that play an essential role in control of movement • Receives indirect input from the cerebellum and from all sensory systems, including vision, and direct input from the motor cortex • Functions in the organization of inherited and highly learned and rather automatic movement programs • Also involved in cognitive and perception functions

  7. Structural Components of the Basal Ganglia • Caudate nucleus • Putamen • Globuspallidusin the forebrain • SubstantiaNigra (midbrain) • Subthalamic nucleus

  8. Structural Components of the Basal Ganglia • Caudate + Putamen =Striatum • Putamen + GlobusPallidus = Lentiform nucleus

  9. Motor System Overview • Cortex sends messages to the caudate and putamen of the basal ganglia • Acts on the Thalamus • Then to the supplementary motor cortex for review and editing • Then to the primary motor cortex, premotor cortex and primary somatosensory cortex • Then to the brain stem and spinal cord • The cerebellum – ensures the desired movements occur smoothly

  10. Basal Ganglia • Basal Ganglia monitors sensory information coming into the brain • sends it to the right place to be stored as a memory

  11. Four Functional Pathways Involving Basal Ganglia • A dopamine pathway from the substantianigra to the striatum • A γ-aminobutyric acid (GABA) pathway from the striatum to the globuspallidus and substantianigra • Acetylcholine-secreting neurons, which are important in networks within the neostriatum • Multiple general pathways from the brain stem that secrete norepinephrine, serotonin, enkephalin, and several other neurotransmitters in the basal ganglia and the cerebral cortex

  12. Thalamus • It relays to the cerebral cortex information received from other regions of the brain and spinal cord. • Sends information down spinal cord to the body • a brain “switching station”

  13. Thalamus • The cerebral cortex is interconnected with the Thalamus • Excitatory circuit • If unmodulated would cause hyperactivity = stiffness and rigidity with a continuous tremor (tremor at rest) • Basal Ganglia modulates the Thalamic excitability by an inhibitory loop

  14. The cerebellum receives continuous information about the sequence of muscle contractions from the brain • Receives sensory information from the peripheral parts of the body • Proprioception • sequential changes in the status of each body part

  15. Brain Stem Midbrain • Associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation Pons • Nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture

  16. Brain Stem Medulla • Contains the cardiac, respiratory, vomiting and vasomotor centers dealing with autonomic, involuntary functions • Breathing, heart rate and blood pressure

  17. Spinal Cord Structure and Function • White Matter Pathways • Myelinated axons surrounding gray matter = cell bodies and their synaptic interconnections • Central Butterfly of Gray Matter • Collections of motor neurons with related function in the anterior horns • Sensory relay neurons in the posterior horn

  18. Dorsal Ventral

  19. Ascending (Sensory) Pathways • AnterolateralSpinothalamic Tract • Carries information from pain, temperature and crude touch receptors to the thalamus (relay station of the brain) • First neuron synapses in the dorsal horn • Second neuron crosses the cord to the region ventral to the central canal and travels in the spinothalamic tract to the thalamus

  20. Ascending Pathways

  21. Ascending (Sensory) PathwaysDorsal Columns • Medial Leminiscal Pathways • Carries information from the skin of the lower and upper limbs (light touch, vibration, ability to discriminate between adjacent stimuli, pressure) • Carries information from shoulder, arm and finger on position and tension in muscles and tendons, movement, etc. • Dorsal root ganglion to the cord, to the dorsal column of white matter, to a nucleus in the medulla to the thalamus to the cortex for conscious perception

  22. Descending Pathway

  23. Descending (Motor) Pathways • Lateral Corticospinal Tract (Pyramidal Tract) • Carries movement signals from the cerebral cortex to the motor neurons in the spinal cord • Crosses over in the medulla • Travels down the cord in a lateral position • Passes into the gray matter in the cord to synapse with the motor neuron

  24. Descending (Motor) Pathway • Extrapyramidal Pathways (Multineuronal Pathways) • Provides for the support of movements of the lateral corticospinal tract • Movements of the trunk, proximal limb muscles, balance, posture, orienting to sight or sound and more.

  25. Pyramidal motor system • Originates in the motor cortex • Controls all of our voluntary movements • Consists of upper motor neurons in the Primary Motor Cortex and lower motor neurons in the anterior horn of the spinal cord Extrapyramidal motor system • Originates in the basal ganglia • Includes the substantianigra, caudate, putamen, globuspallidus, thalamus, and subthalamic nucleus. • Provides background for the more crude, supportive movement patterns

  26. Amyotrophic Lateral Sclerosis (ALS) • Rapidly progressive weakness, muscle atrophy, spasticity, dysphagia • Early symptoms: muscle weakness in an arm or leg, twitching, slurred speech • Death within 2-3 years due to respiratory compromise • Sensory and cognitive function are unaffected

  27. Locations of MotorneuronsAffected by ALS • The anterior horn cells of the spinal cord are affected • Death of LMNs leads to denervation, with subsequent shrinkage of musculature and muscle fiber atrophy. • The UMNsof the cerebral cortex are affected later • Lastly the motor nuclei of the brain stem, particularly the hypoglossal nuclei are affected Lou Gehrig

  28. xv Steven Hawking

  29. http://vimeo.com/27944955 http://www.youtube.com/watch?v=-qFSMXEYC3c

  30. Spinal Cord Trauma • Often leads to paraplegia or quadriplegia depending on the location and extent of the injury • Hyperextension Injury • When the forehead is struck and driven posteriorly • Diving impact in shallow water • May tear the anterior spinal ligament and spinal cord may contact the vertebral body

  31. Trauma to the Spinal Cord • Hyperflexion Injury • When the head of shoulders are struck from behind by an object of considerable weight or from a fall

  32. Spinal Cord Trauma • Concussion • Mild injury, transient and reversible • Contusion • Severe trauma with hemorrhagic necrosis, edema and softening of the cord – Myelomalacia, • or blood in the cord – Hematomyelia • Laceration or Tansection

  33. Cervical Contusion

  34. Disorders Arising in the Basal Ganglia • Characteristics of Disorders of the Basal Ganglia • Involuntary movements • Alterations in muscle tone • Disturbances in body posture

  35. Characteristics of Disorders of the Basal Ganglia • Involuntary movements • Alterations in muscle tone • Disturbances in body posture

  36. Types of Involuntary Movement Disorders • Tremor = Trembling or vibrating • Tics = A habitual spasmodic contraction of the muscles, most often in the face • Chorea = Irregular writhing movements • Athetosis = Wormlike twisting of limb • Ballismus = Violent flinging motion of limbs • Dystonia = Abnormal posture • Dyskinesias = Bizarre wriggling movements • TardiveDyskinesia • Develops due to use of antipsychotic medications

  37. Parkinson Disease • Characteristics • 0.3% of the general population has Parkinson Disease = 80,000 people • Usually begins after 50 years of age • Affects men twice as often as women • Course of the disease is 10-20 years • Clinical syndrome • Parkinsonism • James Parkinson, 1817 = ‘shaky palsy’

  38. Parkinson Disease • Degeneration of pigmented neurons (containing dopamine) in the substantianigra • Cause unknown: May be environmental/genetic • Early symptoms: tremor, rigidity, slow movement • Later: cognitive problems, dementia, dyskinesia • Gross: atrophy of substantianigra • Microscopic: Lewy bodies (inclusions in neurons)

  39. Parkinson Disease • Cogwheel-type motion • Ratchet-like movements • Bradykinesia • Slowness initiating and performing movements • Difficulty walking • Neuropsychiatric disorders

  40. xv Parkinson disease (R) : atrophy of substantianigra

  41. xv Parkinson disease: Lewy body

  42. xv Michael J. Fox and Muhammad Ali

  43. http://www.youtube.com/watch?v=xuVY7wS25rc&feature=related

  44. Huntington Disease • Degeneration of basal ganglia and cerebral cortex • Early symptoms: lack of coordination, unsteady gait • Later: chorea (involuntary writhing), psychiatric symptoms, dementia • Autosomal dominant mutation on chromosome 4 • Begins in 30s-40s; slow progression over 10-20 years

More Related