Neurology s2010
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Transcript

  • 1. The Nervous System Mindy Milton, MPA, PA-C July 15, 2010
  • 2. Neurological Anatomy• Neurons – Functional units of the nervous system • Fuel source is glucose • Does not require insulin for cellular uptake • Structure – Cell body: contains nucleus, neurofilaments, and neurotubules. Mitochondria active due to high energy needs, contain Nissl bodies that are responsible for the grey color of the neuron tissue – Dendrites: fine highly branched structures that are responsible for receiving information and transmitting to cell body – Axon: long projection that is capable of propagating an action potential
  • 3. • Neurons – Neuronal structure • Anaxonic: small with no anatomical clues to identify dendrite from axon • Unipolar: single dendrite and axon that are essentially fused with cell body that lies off to the side • Bipolar: two distinct processes ie axon and dendrite • Multipolar: have two or more dendrites and a single axon
  • 4. NEURON TYPES
  • 5. Types of neuronal structure
  • 6. Multipolar Neuron
  • 7. Neuroglia OligodendrocytesAstrocyte EpendymalMicroglia Cellscells
  • 8. Neurological Anatomy• Synapse – Definition: specialized site where the neuron communicates with another cell – Components • Pre-synaptic cell: neuron that sends the message • Post- synaptic cell: neuron or muscle cell that receives a message • Neurotransmitters: chemical substances that are released by the pre-synaptic cell and cause a change in electrical activity of the post-synaptic cell i.e stimulation of an impulse
  • 9. SYNAPTIC TRANSMISSION
  • 10. NEUROMUSCULAR JUNCTION• Anatomy: – Axon terminal contains large numbers of mitochondria that are important in the synthesis of acetylcholine – Acetylcholine is stored in multiple vesicles – Synaptic cleft: area between the axon and the muscle fiber – Sub neural cleft: invagination of the muscle fibers that increases surface area
  • 11. Neurotransmitters These have either excitatory functions, inhibitory or both• Acetylcholine• Norepinephrine• Serotonin• Dopamine• Histamine• Gamma aminobutyric acid (GABA)• Glycine• Glutamate and Aspartate• Endorphin• Substance P
  • 12. Cerebral Cortex• General Principles – Each cerebral cortex receives information from and sends motor commands to the opposite side of the body – Two hemispheres have different functions – Assignment of specific functions to a specific region of the brain is imprecise at this time
  • 13. Neurological Anatomy
  • 14. Pre-Frontal Function• Alertness and orientation• Mood• Attention• Perception• Memory• Thought content• Thought process• Insight• Judgment• Language
  • 15. Examination of pre-frontal function• Observation of alertness, dress, hygiene, manor.• Coma scale, e.g. Glascow• General conversation and history-taking• Mental status examinations• Special scales, e.g., depression, alcohol
  • 16. CEREBRUM• FRONTAL LOBE • PARIETAL LOBE – Contains somatic motor – Contains somatic sensory areas areas • Voluntary • Primary • Premotor area • Association • Eye fields – Important in the interpretation of sensory – Important in the control data of body movements – Loss is associated with – Loss is associated with difficulty recognizing inability to direct and objects, forms, or having a program movements sense of body parts
  • 17. Homunculus
  • 18. CEREBRUM• TEMPORAL LOBE – Hearing and speech is located in the dominant hemisphere – Responsible for the interpretation and understanding of speech – Major area of long term memory storage – “General Interpretative or Wernicke’s area” – Vestibular sense
  • 19. CEREBRUM• OCCIPITAL LOBE – Vision and the visual interpretative area• CORPUS CALLOSUM – Connects the two hemisphere’s and helps coordinate activities between them. Transfers learned descrimination, experiences, and memories
  • 20. Neurological Anatomy• Cerebral Cortex – Association areas: storage, analysis and interpretation of sensory data • Somatic association area • Visual association area • Auditory association area
  • 21. Neurological Anatomy• Integrative Areas – Integrate information from multiple association areas and direct complex motor activity – General Interpretive Area: (Wernike’s Area) • Present in the left hemisphere • Receives information from all of the sensory association areas • Provides the ability to interpret what is seen and heard, coordinates access to complex visual and auditory memories – Broca’s area: • Motor neurons in the general interpretative area that coordinate the activity of the respiratory, pharyngeal, and muscles of the tongue, cheeks, and jaws
  • 22. Anatomy
  • 23. CEREBRUM• BASAL GANGLION – Exerts regulating, controlling influences on motor integration – Numerous pathways from the motor cortex – Dopamine and GABA found here and are responsible for inhibition of tone
  • 24. DIENCEPHLON• THALAMUS – Receives sensory information for somatic senses, taste, hearing, and relays to cerebral cortex – System of connecting nuclei• HYPOTHALAMUS – Temperature regulation, thirst center, ADH release – Behavior: affective nature of sensory stimuli – Hormonal control
  • 25. BRAIN STEM• MIDBRAIN – Located between the Pons and diencephalon – Contains both motor and sensory pathways – Contains the nuclei for the third and fourth cranial nerves• MEDULLA – Located between the Pons and spinal cord – Center for vegetative functions – Cranial nerve tracts for 8,9,10,11,12
  • 26. Reticular Activating System
  • 27. CEREBELLUM• CEREBELLUM – Important in synchronization of muscle movement – Monitors and makes corrective movements – Receives information from the motor and sensory cortex, and peripheral sensory receptors – Serves as feedback regulator – “Damping” of movement
  • 28. Neurological Anatomy: CSF• Produced by the choroid plexus in the lateral, third and fourth ventricles• Flow pathway – Lateral ventricle – Foramen of Monroe – Third ventricle – Aqueduct of Sylvius – Fourth ventricle – Foramina of Luschka, Foramen of Magendi
  • 29. CSF• Allows passage of nutrients between the blood and extracellular fluid of the brain• Reabsorbed by the arachnoid villi• Blood brain barrier: selective ability for substances to enter the brain through the capillaries of the choroid plexus.
  • 30. CSF• Cerebral Spinal Fluid – Reabsorbed by the arachnoid villa secondary to pressure gradient – Arachnoid villa act as one way valve that moves CSF fluid out into blood – Obstruction of flow of CSF fluid will increase pressure within cranial cavity. – Hydrocephalus is the result of increased CSF
  • 31. Hydrocephalus
  • 32. MENINGES• Dura mater: tough outer meningeal membrane that lies directly below the skull. The epidural space lies between the dura and the skull• Arachnoid: middle meningeal membrane with tissue arranged in a web like fashion. Cross the subdural space and reabsorb CSF
  • 33. MENINGES• PIA MATER: is a vascular thin membrane that covers the brain and the spinal cord – Vessels pass between the pia and the arachnoid through the subarachnoid space
  • 34. Neurological Anatomy:Meninges
  • 35. Spinal Cord• Spinal Cord Nerves – Vertebrae • 8 cervical • 12 thoracic • 5 lumbar • 5 Sacral • 1 coccygeal – Divided into sensory and motor pathways
  • 36. MOTOR SYSTEM• SPINAL CORD – Automatic reflex control – Thirty one pairs of spinal nerves with a sensory and motor root – Anterior Horn cells are large myelinated motor neurons that terminate on skeletal muscle
  • 37. Spinal Cord View
  • 38. SENSORY SYSTEM• Afferent transmission through posterior (dorsal) horns of the spinal cord• Sensory tracts – Spinothalamic • Small myelinated/non-myelinated fibers • Poorly localized sensation of crude touch, pain, temperature • Fibers synapse quickly on entering the spinal cord and cross over to the opposite side
  • 39. SENSORY TRACTS• POSTERIOR COLUMN – Larger fibers that are myelinated with increased degree of spatialization – Carries fibers for touch requiring localization, vibratory sense, and position sense – Travels up same side of cord and synapses with second order neuron that travels to thalamus – Well spatialized: organized for increased ease of sensory interpretation and localization
  • 40. • Sensory Pathways• Pain and temperature• Cross at Cord level.• Touch crosses at• Medulla
  • 41. Neuro Anatomy: Sensory Tracts
  • 42. Neuro Anatomy: Sensory Tracts
  • 43. MOTOR SYSTEM• MOTOR CORTEX – Initiation of the pyramidal tract in the large Betz cells within the motor cortex – Impulses sent down to the motor tracts with collateral messages to the cerebellum, basal ganglia, and reticular activating system
  • 44. Motor pathways• Lower motor• Upper motor – Pyramidal • Fine discrete – Extrapyramidal • Coordination- cerebellar • Tone- mid-brain
  • 45. MOTOR TRACTS• CORTICOSPINAL - PYRAMIDAL – UMN Fibers pass from the cell body of the Betz cell in the motor cortex through the brain stem down the opposite side of the cord – Responsible for fine discrete motor movement – Synapse with inter-neurons or anterior horn cells in the spinal cord – Necessary for voluntary movement – Excitatory in nature
  • 46. MOTOR TRACTS• BASAL GANGLIA - EXTRAPYRAMIDAL – All tracts outside the corticospinal system – Controls body tone and gross body movements• Cerebellum – Sensory and motor input – Controls posture and coordination
  • 47. Motor Pathways• Most cross at Medulla in pyramid-shaped pathways. – Some don’t crossSo whole tract is calledPyramidal tract.
  • 48. Neuro Anatomy: Motor Tracts
  • 49. Cerebellar Function
  • 50. Test Motor pathways• DTRs• Active range of motion (include CN III, IV, VI, VII, XI, XII)• Gait• Romberg• Coordination
  • 51. Blood Supply: CNS• General Concepts – 20% of cardiac output per minute – Blood supply controlled largely by changes in the level of carbon dioxide• Arterial Blood Flow – Internal carotids enter through the skull, branch into the anterior and middle cerebral arteries – Vertebral arteries: originate from the subclavian, enter the skull through the foramen magnum, join to form the basilar artery, that will then divide and form the posterior cerebral arteries
  • 52. Blood Supply: CNS• Circle of Willis – Formed by posterior cerebral arteries, posterior communicating arteries, internal carotid arteries, anterior cerebral arteries, and anterior communicating arteries – Ring shaped anastomosis allows for protection of blood flow interruption from the vertebral or carotid arteries
  • 53. Blood Supply: CNS
  • 54. Blood Supply: CNS
  • 55. Peripheral Nervous System• Two Components – Spinal and cranial nerves – Autonomic Nervous system• Spinal Nerves – Mixed nerves as they contain both sensory and motor neurons – Divide and form posterior and anterior rami – Anterior rami then form plexuses • Brachial plexus: C 5-8 and T1 innervates the nerves of the arm, wrist, and hand • Lumbar plexus: L2-4 and sacral plexus: L5-S5 innervate the anterior and posterior portions of the lower body – Posterior rami form dermatomes that are distributed to specific areas of the body – Cranial Nerves: Most are mixed nerves that arrive from nuclei in the brain or brain stem
  • 56. Neurological Anatomy• Peripheral Nervous System – All nervous tissue outside of the central nervous system – Important in the delivery of sensory data to the CNS and transmission of motor commands from the CNS – Two divisions • Afferent: brings sensory data into CNS • Efferent: transmits motor information from CNS – Somatic nervous system: skeletal muscles – Autonomic nervous system: visceral motor system
  • 57. Sensory System• Smell• Vision• Hearing• Taste• Touch• Pain• Temperature• Pressure• Position• Vibration
  • 58. Testing the Sensory System• Cranial nerves I, II, V, VII, VIII, IX, X• Body sensory touch, pain, temperature• DTRs• Vibratory• Position• Romberg
  • 59. Cranial Nerve: Olfactory
  • 60. Cranial Nerve: Optic
  • 61. Optic Nerve• The visual signalsof the right half ofboth eyes goesto left visual cortex
  • 62. Cranial Nerve: Trigeminal
  • 63. Cranial Nerve: Facial
  • 64. Cranial Nerve: Acoustic
  • 65. Cranial Nerve: Glossopharyngeal
  • 66. Cranial Nerve: Vagus
  • 67. • DermatomeDistribution
  • 68. • Peripheral NerveDistribution
  • 69. Lower Motor Neuron Pathway
  • 70. Reflexes• Test sensory perception• Sensory pathway• Sensory-motor connection• Motor nuclei• Motor pathway• Muscle function• Neurotransmitters.• Flexible joint
  • 71. Autonomic system• Sympathetic• Parasympathetic• Test largely by history• Note skin temp, moisture,• Vital signs• Pupillary response to light, accommodation
  • 72. The End