Review Of Anatomy And Physiology Of The Nervous


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Review Of Anatomy And Physiology Of The Nervous

  1. 1. Review of Anatomy and Physiology of the Nervous System Anthony P. Toledo, MD, RN, MAN, FPAFP Chairman, MS2 Our Lady of Fatima University
  2. 2. Objectives <ul><li>Review the anatomy and physiology of the nervous system </li></ul><ul><li>Identify specific topics for consideration during health history assessment interview of the client with neurologic disorders. </li></ul><ul><li>Describe assessment of neurologic function, including examination of mental status, cranial nerves, sensory nerves, motor nerves, cerebellar dysfunction and reflexes. </li></ul><ul><li>Describe special neurologic examinations. </li></ul><ul><li>Identify abnormal findings that may indicate impairment of neurologic functions. </li></ul>
  3. 3. Nervous System <ul><li>initiates actions and coordinates the activity of the muscles </li></ul><ul><li>monitors the organs </li></ul><ul><li>constructs and also stops input from the senses </li></ul>
  4. 4. Parts of the Nervous System <ul><li>The nervous system is divided into the central nervous system (consisting of the brain and spinal cord) and the peripheral nervous system (consists of nerves made up of neurons that carry information to and from the central nervous system). </li></ul>Organization of the Nervous System Peripheral Somatic Autonomic Sympathetic Parasympathetic Enteric Central
  5. 5. Neuron Structure <ul><li>Cell body </li></ul><ul><ul><li>Large vesicular nucleus </li></ul></ul><ul><ul><li>Single prominent nucleolus </li></ul></ul><ul><ul><li>Mitochondria & other organelles </li></ul></ul><ul><ul><li>Abundant RER (Nissl substance) </li></ul></ul><ul><ul><li>Microtubules & neurofilaments </li></ul></ul>
  6. 6. Neuron Structure <ul><li>Dendrites </li></ul><ul><ul><li>Receive information and transmit it to the cell body </li></ul></ul>
  7. 7. Neuron Structure <ul><li>Axon </li></ul><ul><ul><li>Thin, cylindrical process arising from the axon hillock </li></ul></ul><ul><ul><li>Contain abundant microtubules and neurofilaments </li></ul></ul><ul><ul><li>Terminate as synaptic boutons which contain vesicles of neurotransmitter </li></ul></ul>
  8. 8. Neuron Structure <ul><li>Node of Ranvier </li></ul><ul><ul><li>Discontinuity in the myelin </li></ul></ul><ul><ul><li>Exposed to extracellular space </li></ul></ul><ul><ul><li>Action potential skips from node to node &quot;saltatory conduction&quot; </li></ul></ul>
  9. 9. Neuron Structure <ul><li>Myelin </li></ul><ul><ul><li>Unmyelinated axons </li></ul></ul><ul><ul><ul><li>Seen in peripheral nerves </li></ul></ul></ul><ul><ul><ul><li>Surrounded by cytoplasm of Schwann cells </li></ul></ul></ul><ul><ul><ul><li>Small diameter </li></ul></ul></ul><ul><ul><ul><li>Slow conduction velocity </li></ul></ul></ul><ul><ul><li>Myelinated axons </li></ul></ul><ul><ul><ul><li>Larger diameter </li></ul></ul></ul><ul><ul><ul><li>Ensheathed in myelin </li></ul></ul></ul><ul><ul><ul><li>Rapid conduction velocity </li></ul></ul></ul>
  10. 10. Neuron Structure <ul><li>Myelin Forming Cells </li></ul><ul><ul><li>Schwann Cells </li></ul></ul><ul><ul><ul><li>Myelin forming cells of the peripheral nervous system </li></ul></ul></ul><ul><ul><ul><li>Formed during fourth month of development </li></ul></ul></ul><ul><ul><ul><li>One Schwann cell myelinates only one axon </li></ul></ul></ul><ul><ul><li>Oligodendrocytes </li></ul></ul><ul><ul><ul><li>Myelin-forming cells of the CNS </li></ul></ul></ul><ul><ul><ul><li>Begin formation during fourth month of development and continue until second decade of life </li></ul></ul></ul><ul><ul><ul><li>Individual oligodendrocyte able to myelinate many axons </li></ul></ul></ul><ul><ul><ul><li>Degeneration results in multiple sclerosis </li></ul></ul></ul>
  11. 11. Classification of Neurons by Neuronal Processes <ul><li>Unipolar neurons -- one axon, no dendrites; occur only during development </li></ul><ul><li>Bipolar neurons -- found in cochlear and vestibular ganglia, retina and olfactory mucosa </li></ul><ul><li>Multipolar neurons -- one axon and multiple dendrites, found in ventral horn *Most neurons in body are multipolar </li></ul><ul><li>Pseudounipolar neurons -- found in dorsal root ganglia and most cranial ganglia </li></ul>
  12. 12. Classification of Neurons by Functional Role <ul><li>Motor Neurons - Control effector organs and muscle fibers </li></ul><ul><li>Sensory Neurons - Receive sensory stimuli from internal or external environment; Relay them to CNS </li></ul>
  13. 13. Action Potential
  14. 14. Synapse <ul><li>Synapses - Specialized membrane junctions designed for unidirectional communication between neurons or between neurons and effector cells. Pre- and postsynaptic membranes separated by 20 nm. space called synaptic cleft. </li></ul>
  15. 15. Synaptic Vesicles <ul><li>Synaptic vesicles - Contain neurotransmitter. </li></ul><ul><li>Release NT into synaptic cleft when vesicles fuse with presynaptic membrane. NT may excite (depolarize) or inhibit (hyperpolarize) the postsynaptic membrane. </li></ul><ul><li>Certain NT are inactivated in synaptic cleft by Enzymatic degradation (e.g., ACh by AChE). Reuptake by presynaptic cell (e.g., NE) </li></ul>
  16. 16. Synaptic Transmission
  17. 17. Neuromuscular Junction <ul><li>Occurs at the motor end plate </li></ul><ul><li>Synapse between neurons and muscle cells </li></ul><ul><li>ACh released from axon depolarizes sarcolemma via the acetylcholine nicotinic receptors </li></ul><ul><li>Autoimmune response causes myasthenia gravis </li></ul>
  18. 18. Neuromuscular Junction
  19. 19. Neuroglia <ul><li>&quot;Nerve glue&quot; </li></ul><ul><li>In CNS: microglia, astrocytes, oligodendrocytes, and ependymal cells </li></ul><ul><li>In PNS: Schwann cells </li></ul>
  20. 20. Types of Neuroglia <ul><li>Astrocytes </li></ul><ul><ul><li>Important in controlling microenvironment of nerve cells </li></ul></ul><ul><ul><li>Participate in maintenance of the blood-brain barrier </li></ul></ul><ul><li>Oligodendrocytes </li></ul><ul><ul><li>Myelinate axons of the CNS </li></ul></ul><ul><li>Microglia </li></ul><ul><ul><li>Phagocytic, part of the mononuclear phagocyte system </li></ul></ul><ul><ul><li>Unlike other neuroglial cells which originate from neuroectoderm </li></ul></ul><ul><ul><li>Originate from mesoderm </li></ul></ul><ul><li>Ependymal cells </li></ul><ul><ul><li>Line the ventricular cavities of the brain and central canal of spinal cord </li></ul></ul><ul><ul><li>Cilia present on cells helps move cerebrospinal fluid through ventricles </li></ul></ul><ul><li>Schwann cells </li></ul><ul><ul><li>Myelinate peripheral axons </li></ul></ul>
  21. 21. Derivatives of the Brain Vesicles <ul><li>Forebrain </li></ul><ul><ul><li>Telencephalon — cerebral hemispheres and lateral ventricles </li></ul></ul><ul><ul><li>Diencephalon — thalamus, hypothalamus, and epithalamus including the pineal gland, mammilary bodies, retina, and optic nerve </li></ul></ul>
  22. 22. Derivatives of the Brain Vesicles <ul><li>Midbrain </li></ul><ul><ul><li>Mesencephalon — midbrain and cerebral aqueduct </li></ul></ul><ul><li>Hindbrain </li></ul><ul><ul><li>Metencephalon — pons and cerebellum </li></ul></ul><ul><ul><li>Myelencephalon — medulla </li></ul></ul>
  23. 23. The Brain
  24. 24. The Brain <ul><li>Cerebral Cortex </li></ul><ul><ul><li>Surface is highly convoluted with bulges referred to as gyri and spaces separating the gyri called sulci </li></ul></ul><ul><li>Two prominent sulci </li></ul><ul><ul><li>Sylvian fissure — divides the fontal and temporal lobes </li></ul></ul><ul><ul><li>Central sulcus of Rolando — separates the parietal and temporal lobes </li></ul></ul>
  25. 25. The Brain <ul><li>Frontal Lobe </li></ul><ul><ul><li>Primary motor cortex — damage causes contralateral spastic paresis. Located in the precentral gyrus </li></ul></ul><ul><ul><li>Premotor cortex —damage causes apraxias </li></ul></ul>
  26. 26. The Brain <ul><li>The motor homunculus in precentral gyrus </li></ul><ul><ul><li>Muscles of head represented most ventrally closest to lateral fissure </li></ul></ul><ul><ul><li>Dorsally, regions of neck, upper limb, and trunk on lateral aspect </li></ul></ul><ul><ul><li>Medial aspect motor representation for the pelvis and lower limb </li></ul></ul><ul><ul><li>Supplied by branches of anterior cerebral artery </li></ul></ul>
  27. 27. The Brain <ul><li>Prefrontal Cortex </li></ul><ul><ul><li>Located in front of premotor area </li></ul></ul><ul><ul><li>Represents ¼ of entire cerebral cortex in human brain </li></ul></ul><ul><ul><li>Involved in organizing and planning the intellectual and emotional aspects of behavior </li></ul></ul><ul><ul><li>Lesions to prefrontal area </li></ul></ul><ul><ul><ul><li>Cannot concentrate </li></ul></ul></ul><ul><ul><ul><li>Easily distracted </li></ul></ul></ul><ul><ul><ul><li>General lack of initiative, foresight, and perspective </li></ul></ul></ul><ul><ul><ul><li>Apathy </li></ul></ul></ul><ul><ul><ul><li>Suckling and grasp reflexes evident </li></ul></ul></ul>
  28. 28. The Brain <ul><li>Expressive Aphasia </li></ul><ul><ul><li>Area in left or dominant hemisphere affected. </li></ul></ul><ul><ul><li>Damage to Broca’s area produces a motor, nonfluent, or expressive aphasia that reflects a difficulty in piecing together words to produce expressive speech </li></ul></ul>
  29. 29. The Brain <ul><li>Parietal Lobe </li></ul><ul><ul><li>Primary Somatosensory Cortex </li></ul></ul><ul><ul><ul><li>Begins posterior to central sulcus with postcentral gyrus </li></ul></ul></ul><ul><ul><ul><li>Contains primary somatosensory cortex </li></ul></ul></ul>
  30. 30. The Brain <ul><li>The sensory homunculus in postcentral gyrus </li></ul><ul><ul><li>Similar somatotopic representation of body </li></ul></ul><ul><ul><ul><ul><li>Head, neck, upper limbs, and trunk laterally </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pelvis and lower limb medially </li></ul></ul></ul></ul>
  31. 31. The Brain <ul><li>Parietal Lobe </li></ul><ul><ul><li>Posterior Parietal Association Cortex </li></ul></ul><ul><ul><ul><li>Lesions here if in the dominant hemisphere result in apraxia </li></ul></ul></ul><ul><ul><ul><li>Deficit seems to reflect a lack of understanding how to organize the performance of a pattern of movements </li></ul></ul></ul><ul><ul><ul><li>Astereognosia (inability to recognize items by touch) may be present </li></ul></ul></ul><ul><ul><ul><li>No loss of tactile or proprioceptive sensation </li></ul></ul></ul>
  32. 32. The Brain <ul><li>Receptive Aphasia </li></ul><ul><ul><li>Cannot comprehend spoken language, May or may not be able to read (alexia), Characterized by fluent verbalization that lacks meaning, Generally unaware of deficit </li></ul></ul>
  33. 33. The Brain <ul><li>Occipital Lobe </li></ul><ul><ul><li>known as primary visual cortex </li></ul></ul><ul><ul><li>Retinal surface represented in orderly manner on surface of the area </li></ul></ul><ul><ul><ul><li>Damage to discrete area will produce scotoma in corresponding portion of visual field </li></ul></ul></ul><ul><ul><ul><li>Unilateral lesion in results in a contralateral homonymous hemianopsia with macular sparing </li></ul></ul></ul><ul><ul><li>Posterior cerebral artery supplies occipital lobe and splenium of corpus callosum </li></ul></ul>
  34. 34. The Brain <ul><li>Temporal Lobe </li></ul><ul><ul><li>Primary Auditory Cortex </li></ul></ul><ul><ul><ul><li>located on the two transverse gyri of Heschl </li></ul></ul></ul><ul><ul><ul><li>Cross the superior temporal lobe deep within the lateral sulcus </li></ul></ul></ul><ul><ul><ul><li>Patients with unilateral damage show little loss of auditory sensitivity but have some difficulty in localizing sounds in contralateral field </li></ul></ul></ul>
  35. 35. The Brain <ul><li>Cerebellum </li></ul><ul><ul><li>Derived from the Metencephalon </li></ul></ul><ul><ul><li>Located dorsal to the pons and medulla </li></ul></ul><ul><ul><li>Fourth ventricle found between cerebellum and dorsal aspect of pons </li></ul></ul><ul><ul><li>Involved in fine tuning and coordination of muscle movements </li></ul></ul>
  36. 36. The Brain <ul><li>Cerebellum </li></ul><ul><ul><li>Midline vermis and two lateral cerebellar hemispheres </li></ul></ul><ul><ul><ul><li>Vermis controls axial and proximal musculature of limbs </li></ul></ul></ul><ul><ul><ul><li>Intermediate part of hemisphere controls distal musculature </li></ul></ul></ul>
  37. 37. The Brain <ul><li>Cerebellum </li></ul><ul><ul><li>Midline vermis and two lateral cerebellar hemispheres </li></ul></ul><ul><ul><ul><li>Lateral part involved in motor planning and execution </li></ul></ul></ul><ul><ul><ul><ul><li>Also called the cerebrocerebellum due to input from cerebrum </li></ul></ul></ul></ul><ul><ul><ul><li>Flocculonodular lobe involved in control of balance and eye movements </li></ul></ul></ul><ul><ul><ul><ul><li>Also called the vestibulocerebellum </li></ul></ul></ul></ul>
  38. 38. Cerebellar Lesions <ul><li>Hallmark of cerebellar dysfunction is tremor with intended movement without paralysis or paresis </li></ul><ul><li>Symptoms associated are expressed ipsilaterally </li></ul><ul><li>Vermal region lesion </li></ul><ul><ul><li>Difficulty maintaining posture, gait, or balance </li></ul></ul><ul><ul><li>May be differentiated from those patients with lesion of dorsal columns by presence of a Romberg’s sign </li></ul></ul><ul><ul><ul><li>Cerebellar lesion will have patient sway with eyes open </li></ul></ul></ul>
  39. 39. Cerebellar Lesions <ul><li>Hemisphere lesions </li></ul><ul><ul><li>Intention tremor is seen when voluntary movements performed </li></ul></ul><ul><ul><li>Dysmetria — inability to stop a movement at the proper place </li></ul></ul><ul><ul><li>Dysdiadochokinesia — reduced ability to perform alternating movements </li></ul></ul><ul><ul><li>Scanning dysarthria </li></ul></ul><ul><ul><li>Gaze dysfunction occurs when eyes try to fix on a point </li></ul></ul><ul><ul><li>Hypotonia — occurs with acute insult </li></ul></ul><ul><ul><ul><li>Muscles feel flabby on palpation </li></ul></ul></ul><ul><ul><ul><li>Deep tendon reflexes diminished </li></ul></ul></ul>
  40. 40. The Brain <ul><li>Thalamus </li></ul><ul><ul><li>major sensory relay for ascending tactile, visual, auditory, and gustatory information that goes to neocortex </li></ul></ul>
  41. 41. The Brain <ul><li>Hypothalamus </li></ul>
  42. 42. The Brain <ul><li>Limbic System </li></ul><ul><ul><li>Involved in Feeding, Fighting, Feeling, Flight, and sex (5Fs) </li></ul></ul><ul><ul><li>Consists of cortical and diencephalic structures found on the medial aspect of the hemisphere </li></ul></ul><ul><ul><li>Prominent structure — hippocampal formation on medial aspect of the temporal lobe </li></ul></ul><ul><ul><li>Other limbic related structures </li></ul></ul><ul><ul><ul><li>Amygdala — deep in medial part of anterior temporal lobe rostral to hippocampus </li></ul></ul></ul><ul><ul><ul><li>Septal nuclei — medial between anterior horns of lateral ventricle </li></ul></ul></ul>
  43. 43. The Brain <ul><li>Basal Ganglia </li></ul><ul><ul><li>Initiate and provide gross control over skeletal muscle movements </li></ul></ul><ul><ul><li>Disorders result in uncontrolled, excessive movements or hypokinesia </li></ul></ul>
  44. 44. The Brain <ul><li>Basal Ganglia </li></ul><ul><ul><li>Major components </li></ul></ul><ul><ul><ul><li>Striatum—caudate nucleus and putamen </li></ul></ul></ul><ul><ul><ul><li>External and internal segments of globus pallidus </li></ul></ul></ul><ul><ul><ul><li>Substantia Nigra (midbrain) </li></ul></ul></ul><ul><ul><ul><li>Subthalamus (ventral to thalamus) </li></ul></ul></ul>
  45. 45. Vascular Supply to the Head <ul><li>Supplied by the two internal carotid arteries and the two vertebral arteries </li></ul>
  46. 46. Circle of Willis
  47. 47. Cerebral Arteries Distribution <ul><li>Internal carotid arteries </li></ul><ul><ul><li>Arises from bifurcation of common carotid artery and enters skull through carotid canal </li></ul></ul><ul><ul><li>Branch of ophthalmic artery comes off just before it enters the subarachnoid space and terminates as middle and anterior cerebral arteries </li></ul></ul>
  48. 48. Cerebral Arteries Distribution <ul><li>Middle cerebral artery </li></ul><ul><ul><li>Supplies bulk of lateral surface of hemispheres </li></ul></ul><ul><ul><li>Supplies the posterior limb of internal capsule and basal ganglia </li></ul></ul><ul><ul><li>Occlusion results in spastic paresis of contralateral lower face and upper limb and anesthesia of contralateral face and upper limb </li></ul></ul><ul><ul><li>If left middle cerebral artery branches involved Wernicke’s or Broca’s areas may be affected resulting in aphasia </li></ul></ul>
  49. 49. Cerebral Arteries Distribution <ul><li>Anterior cerebral artery </li></ul><ul><ul><li>Smaller terminal branch of internal carotid </li></ul></ul><ul><ul><li>Supplies the medial surface of frontal and parietal lobes </li></ul></ul><ul><ul><li>Includes motor and sensory cortical areas for the pelvis and lower limbs </li></ul></ul><ul><ul><li>Supplies anterior 4/5 of corpus callosum </li></ul></ul><ul><ul><li>Approximately one inch of frontal and parietal cortex </li></ul></ul><ul><ul><li>Occlusion will results in spastic paresis and anesthesia of contralateral lower limb </li></ul></ul><ul><ul><li>Urinary incontinence may be present if bilateral damage </li></ul></ul>
  50. 50. Cerebral Arteries Distribution <ul><li>Posterior cerebral artery </li></ul><ul><ul><li>Formed by terminal bifurcation of basilar artery </li></ul></ul><ul><ul><li>Supplies occipital and temporal cortex on inferior and lateral surfaces of hemisphere </li></ul></ul><ul><ul><li>Supplies occipital lobe and posterior 2/3 of temporal lobe on medial surface of hemisphere </li></ul></ul><ul><ul><li>Supplies thalamus and subthalamic nucleus </li></ul></ul><ul><ul><li>Occlusion - results in homonymous hemianopsia of contralateral visual field with macular sparing </li></ul></ul>
  51. 51. Dural Venous Sinuses
  52. 52. Ventricular System <ul><li>Brain and spinal cord float within a protective bath of CSF </li></ul><ul><li>Produced continuously by choroids plexus </li></ul><ul><li>Four ventricles </li></ul><ul><ul><li>Two lateral ventricles deep within each cerebral hemisphere </li></ul></ul><ul><ul><li>Third ventricle located in midline within diencephalons </li></ul></ul><ul><ul><li>Fourth ventricle located on dorsal surface of pons and upper medulla </li></ul></ul><ul><li>Ventricles connected resulting in flow of CSF </li></ul>
  53. 53. Flow of CSF <ul><li>CSF flows from lateral ventricles -> interventricular foramen of Monro -> third ventricle -> cerebral aqueduct -> fourth ventricle -> subarachnoid space either throught the foramen of Magendie or foramina Luschka </li></ul>
  54. 54. Cerebrospinal Fluid <ul><li>Adults produce 90 – 150 mL of total CSF </li></ul><ul><li>About 70 % secreted by choroids plexus located in parts of the lateral, third, and fourth ventricles, lined by highly vascularized ependymal cells </li></ul><ul><li>Almost all CSF returns to venous system by draining through arachnoid granulations into superior sagittal dural venous sinus </li></ul><ul><li>Concentration of protein is much lower compared to serum </li></ul><ul><li>Few lymphocytes present; presence of PMN’s always abnormal </li></ul><ul><li>RBCs may be present after traumatic spinal tap or subarachnoid hemorrhage </li></ul>
  55. 55. CSF Abnormalities <ul><li>Hydrocephalus caused by excess volume or pressure of CSF </li></ul><ul><li>Communicating hydrocephalus </li></ul><ul><ul><li>Caused by oversecretion of CSF without obstruction in the ventricles or by problems with absorption in subarachnoid space </li></ul></ul><ul><li>Noncommunication hydrocephalus </li></ul><ul><ul><li>Caused by obstruction of CSF flow inside ventricular system at foramen of Monro, cerebral aqueduct, or fourth ventricle </li></ul></ul><ul><ul><li>Could also be obstruction at foramina Magendie or Luschka </li></ul></ul><ul><li>Normal Pressure hydrocephalus </li></ul>
  56. 56. Blood Brain Barrier <ul><li>Formed by capillary endothelium connected by tight junctions </li></ul><ul><li>Astrocytes participate in maintenance of BBB </li></ul><ul><li>Numerous long processes with expanded vascular end-feet that attach to walls of capillaries </li></ul><ul><li>Water diffuses across BBB readily; glucose must be actively transported across </li></ul>
  57. 57. Meninges
  58. 58. Brain Stem <ul><li>Divisible into three continuous parts: midbrain, pons, medulla </li></ul><ul><li>Home of origins of the sites or termination of fibers in 9/12 CNs </li></ul>
  59. 59. Brain Stem <ul><li>Midbrain site of origin for </li></ul><ul><ul><li>CN III and CN IV </li></ul></ul><ul><li>Pons site of entrance or exit </li></ul><ul><ul><li>CN V, CN VI, CN VII, and CN VIII </li></ul></ul><ul><li>Medulla site of entrance or exit </li></ul><ul><ul><li>CN IX, X, and XII </li></ul></ul><ul><li>Useful in diagnosing brain stem injury </li></ul>
  60. 60. Midbrain <ul><li>Located between pons and diencephalon </li></ul><ul><li>Cerebral aqueduct passes through </li></ul>
  61. 61. Pons <ul><li>Located between medulla and midbrain; cerebellum overlies </li></ul><ul><li>Fourth ventricle found between dorsal surface and cerebellum </li></ul><ul><li>Ventral surface dominated by fibers forming a ventral enlargement carrying pontine fibers to middle cerebellar peduncle (key feature of pons) </li></ul>
  62. 62. Pons <ul><li>Aides in relaying messages in the brain, and contains the pneumotaxic centres that help regulate respiration. </li></ul><ul><li>There are two main domains in the pons for control of respiration </li></ul><ul><ul><li>apneustic center - lower pons (promote inspiration) </li></ul></ul><ul><ul><li>pneumotaxic center - upper pons (inhibiting effect) </li></ul></ul>
  63. 63. Pons <ul><li>Blood to the pons supplied by a number of arteries. </li></ul><ul><ul><li>Pontine arteries </li></ul></ul><ul><ul><li>Anterior inferior cerebellar artery (AICA) </li></ul></ul><ul><ul><li>Superior cerebellar </li></ul></ul>
  64. 64. Medulla <ul><li>Above the spinal cord, below the pons, and anterior to the cerebellum. </li></ul>
  65. 65. Medulla <ul><li>It controls autonomic functions and relays nerve signals between the brain and spinal cord. </li></ul><ul><li>The Medulla oblongata is responsible for controlling several major autonomic functions of the body: </li></ul><ul><ul><li>respiration (via dorsal respiratory group and ventral respiratory group) </li></ul></ul><ul><ul><li>blood pressure </li></ul></ul><ul><ul><li>heart rate </li></ul></ul><ul><ul><li>reflex arcs </li></ul></ul><ul><ul><li>vomiting </li></ul></ul>
  66. 66. Medulla <ul><li>Blood to the medulla is supplied by a number of arteries. </li></ul><ul><ul><li>Anterior spinal artery </li></ul></ul><ul><ul><li>Posterior inferior cerebellar artery (PICA) </li></ul></ul><ul><ul><li>Direct branches of the vertebral artery </li></ul></ul>
  67. 67. CRANIAL NERVES IV Trochlear III Oculomotor VII Facial VI Abducens V Trigeminal CEREBRAL HEMISPHERE MIDBRAIN PONS MEDULLA II Optic I Olfactory VIII Acoustic XII Hypoglossal XI Accessory X Vagus IX Glossopharyngeal
  68. 68. Cranial Nerves
  69. 69. Cranial Nerves
  70. 70. Spinal Cord <ul><li>The spinal cord lies within the spinal cavity, consisting of the vertebral column , the meninges, spinal nerves, spinal fluid, blood vessels, and a cushion of adipose/fat tissue. </li></ul>
  71. 71. Spinal Cord <ul><li>Thirty-one pairs of nerves connect to the spinal cord. They have no special names, but are numbered according to the level of the spinal column from which they emerge. There are 8 cervical (C1-C8), 12 thoracic (T1-T12), 5 lumbar (L1-L5), 5 sacral (S1-S5), and 1 coccygeal pairs of spinal nerves. </li></ul>
  72. 72. Spinal Cord <ul><li>The spinal cord has two general functions: </li></ul><ul><li>1) It provides the two-way conduction routes to/from ( afferent/efferent ) the brain </li></ul><ul><li>2) it serves as the reflex center for all spinal reflexes. </li></ul>
  73. 73. Spinal Cord and Tracts
  74. 74. Spinal Cord and Tracts <ul><li>Spinothalamic tract , carrying pain and temperature impulses to the thalamus and the parietal lobe (sensory) </li></ul><ul><li>Dorsal columns , carrying position and pressure sense to the thalamus and the parietal lobe (sensory) </li></ul><ul><li>Corticospinal (or pyrimidal ) tract , carrying impulses to initiate muscle activity from the frontal lobe. (motor) </li></ul>
  75. 75. Spinothalamic Tract
  76. 76. Dorsal Column
  77. 77. Reflex Arc <ul><li>A reflex is an automatic, i.e.&quot;involuntary,&quot; response of the body to some stimulus, e.g. pupil dilation, to collect more light, at night. Reflexes have afferent (signals to the CNS) and efferent (signals from the CNS) components and may involve one nerve/synapse ( monosynaptic reflex ) or multiple synapses ( polysynaptic reflex ).  The simplest spinal reflex is the tendon reflex , a monosynaptic reflex. </li></ul>
  78. 78. Reflex Arc
  79. 79. Peripheral Nervous System
  80. 80. Spinal Nerves <ul><li>All cervical spinal nerves control movement of the shoulder and arm muscles and receive all sensory input from the skin, muscles, bones, and joints. After leaving the vertebral canal, they merge to form peripheral nerves . The merger of the spinal nerves in the neck region is called the brachial plexus . </li></ul>
  81. 81. Brachial Plexus
  82. 82. Sensory Innervation of the Hand
  83. 83. Spinal Nerves <ul><li>The thoracic spinal nerves do not recombine into plexuses. The anterior roots control the muscles of the abdomen and back; the posterior roots receive information from the abdomen, skin, and muscles and joints of the chest and upper back. </li></ul>
  84. 84. Spinal Nerves <ul><li>The lumbar and sacral nerves , like the cervical, do combine after leaving the vertebral canal. This merger, occuring in the pelvis, is called the lumbosacral plexus , which controls the movement of, and receives information from, the lower extremities, bladder, and bowel. </li></ul>
  85. 85. Lumbo Sacral Plexus
  86. 86. Sensory Innervation of the Foot
  87. 87. The End Thank you