Nervous system final


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by Daniel merga from KEAMED University college Ethiopia Finfinne

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Nervous system final

  2. 2. Functions of the Nervous System1. Sensory input – gathering information • To monitor changes occurring inside and outside the body (changes = stimuli)2. Integration – • to process and interpret sensory input and decide if action is needed.3. Motor output • A response to integrated stimuli • The response activates muscles or glands
  3. 3. Structural Classification of the Nervous System• Central nervous system (CNS) • Brain • Spinal cord• Peripheral nervous system (PNS) • Nerve outside the brain and spinal cord  Spinal nerves  Cranial nerves
  4. 4. Functional Classification of thePeripheral Nervous System Sensory (afferent) division  Nerve fibers that carry information to the central nervous system Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system  Two subdivisions  Somatic nervous system = voluntary  Autonomic nervous system = involuntary
  5. 5. Nervous Tissue: Neurons• Neurons = nerve cells • Cells specialized to transmit messages • Major regions of neurons • Cell body – nucleus and metabolic center of the cell • Processes – fibers that extend from the cell body (dendrites and axons)
  6. 6. Neuron Anatomy• Extensions outside the cell body • Dendrites – conduct impulses toward the cell body • Axons – conduct impulses away from the cell body
  7. 7. Axons and Nerve Impulses• Axons end in axonal terminals• Axonal terminals contain vesicles with neurotransmitters• Axonal terminals are separated from the next neuron by a gap • Synaptic cleft – gap between adjacent neurons • Synapse – junction between nerves
  8. 8. Functional Classification of Neurons• Sensory (afferent) neurons • Carry impulses from the sensory receptors to the CNS • Cutaneous sense organs • Proprioceptors – detect stretch or tension• Motor (efferent) neurons • Carry impulses from the central nervous system to viscera, muscles, or glands• Interneurons (association neurons) • Found in neural pathways in the central nervous system • Connect sensory and motor neurons
  9. 9. Neuron Classification
  10. 10. Structural Classification of Neurons• Multipolar neurons – many extensions from the cell body• Bipolar neurons – one axon and one dendrite• Unipolar neurons – have a short single process leaving the cell body
  11. 11. Central Nervous System (CNS)Regions of theBrain•Cerebralhemispheres(cerebrum)•Diencephalon•Brain stem•Cerebellum
  12. 12. Regions of the Brain: Cerebrum Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Includes more than half of the brain mass  The surface is made of ridges (gyri) and grooves (sulci)
  13. 13. Regions of the Brain: Cerebrum Lobes of the cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum  Frontal lobe  Parietal lobe  Occipital lobe  Temporal lobe
  14. 14. Regions of the Brain: Cerebrum Specialized areas of the cerebrum  Primary somatic sensory area  Receives impulses from the body’s sensory receptors  Located in parietal lobe  Primary motor area  Sends impulses to skeletal muscles  Located in frontal lobe  Broca’s area  Involved in our ability to speak
  15. 15. Regions of the Brain: Cerebrum
  16. 16. Specialized Area of the Cerebrum• Cerebral areas involved in special senses • Gustatory area (taste)[in insula] • Visual area[occipital lobe] • Auditory area • Olfactory area• Interpretation areas of the cerebrum • Speech/language region • Language comprehension region • General interpretation area
  17. 17. Layers of the Cerebrum Layers of the cerebrum  Gray matter—outer layer in the cerebral cortex  composed mostly of neuron cell bodies  White matter—fiber tracts inside the gray matter  Example: corpus callosum connects hemispheres Basal nuclei—islands of gray matter buried within the white matter
  18. 18. Diencephalon• Sits on top of the brain stem• Enclosed by the cerebral heispheres• Made of three parts • Thalamus • Hypothalamus • Epithalamus
  19. 19. Diencephalon
  20. 20. Thalamus• Surrounds the third ventricle• The relay station for sensory impulses• Transfers impulses to the correct part of the cortex for localization and interpretation
  21. 21. Hypothalamus• Under the thalamus• Important autonomic nervous system center • Helps regulate body temperature • Controls water balance • Regulates metabolism• An important part of the limbic system (emotions)• The pituitary gland is attached to the hypothalamus
  22. 22. Epithalamus• Forms the roof of the third ventricle• Houses the pineal body (an endocrine gland)• Includes the choroid plexus – forms cerebrospinal fluid
  23. 23. Brain Stem• Attaches to the spinal cord• Parts of the brain stem • Midbrain • Pons • Medulla oblongata
  24. 24. Brain Stem• Midbrain  Mostly composed of tracts of nerve fibers  Has two bulging fiber tracts—cerebral peduncles  Has four rounded protrusions- corpora quadrigemina  Reflex centers for vision and hearing  Cerebral aqueduct – 3rd-4th ventricles• Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing
  25. 25. Medulla Oblongata• The lowest part of the brain stem• Merges into the spinal cord• Includes important fiber tracts• Contains important control centers • Heart rate control • Blood pressure regulation • Breathing • Swallowing • Vomiting
  26. 26. Cerebellum• Two hemispheres with convoluted surfaces• Provides involuntary coordination of body movements
  27. 27. Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier
  28. 28. Meninges• Dura mater • Double-layered external covering • Periosteum – attached to surface of the skull • Meningeal layer – outer covering of the brain • Folds inward in several areas• Arachnoid layer- Middle layer • Web-like• Pia mater- Internal layer • Clings to the surface of the brain
  29. 29. Cerebrospinal Fluid• Similar to blood plasma composition• Formed by the choroid plexus• Forms a watery cushion to protect the brain• Circulated in arachnoid space, ventricles, and central canal of the spinal cord
  30. 30. Ventricles and Location of the Cerebrospinal Fluid
  31. 31. Blood Brain Barrier• Includes the least permeable capillaries of the body• Excludes many potentially harmful substances• Useless against some substances • Fats and fat soluble molecules • Respiratory gases • Alcohol • Nicotine • Anesthesia
  32. 32. Spinal Cord• Extends from the medulla oblongata to the region of T12• Below T12 is the cauda equina (a collection of spinal nerves)• Enlargements occur in the cervical and lumbar regions Extends from the foramen magnum of the skull to the first or second lumbar vertebra 31 pairs of spinal nerves arise from the spinal cord Cauda equina is a collection of spinal nerves at the inferior end
  33. 33. Spinal Cord Anatomy Internal gray matter is mostly cell bodies  Dorsal (posterior) horns  Anterior (ventral) horns  Gray matter surrounds the central canal  Central canal is filled with cerebrospinal fluid Exterior white mater—conduction tracts  Dorsal, lateral, ventral columns
  34. 34. Spinal Cord Anatomy Meninges cover the spinal cord Spinal nerves leave at the level of each vertebrae  Dorsal root  Associated with the dorsal root ganglia— collections of cell bodies outside the central nervous system  Ventral root  Contains axons
  35. 35. Spinal Cord Anatomy
  36. 36. Peripheral Nervous System• Nerves and ganglia outside the central nervous system• Nerve = bundle of neuron fibers• Neuron fibers are bundled by connective tissue• The PNS functions to convey impulses to and from the brain or spinal cord.• The nerves of the PNS are classified as • cranial nerves or • spinal nerves
  37. 37. Structure of a Nerve• Endoneurium surrounds each fiber• Groups of fibers are bound into fascicles by perineurium• Fascicles are bound together by epineurium
  38. 38. Classification of Nerves• Mixed nerves – both sensory and motor fibers• Afferent (sensory) nerves – carry impulses toward the CNS• Efferent (motor) nerves – carry impulses away from the CNS
  39. 39. • Cranial nerves – 12 pairs of nerves that mostly serve the head and neck – The cranial nerves are designated by roman numerals – Their names indicate the structures innervated or the principal functions of the nerves – Only the pair of vagus nerves extend to thoracic and abdominal cavities 39
  40. 40. I. Olfactory Nerve .Sense of smell.Damage causes impaired sense of smell 40
  41. 41. II. Optic Nerve -Provides vision-Damage causes blindness in visual field 41
  42. 42. III. Oculomotor Nerve Eye movement, opening of eyelid, constriction of pupil, focusingDamage causes drooping eyelid, dilated pupil, doublevision, difficulty focusing and inability to move eye in certain directions 42
  43. 43. IV. Trochlear Nerve -Eye movement (superior oblique muscle)-Damage causes double vision and inability to rotate eye inferolaterally 43
  44. 44. V. Trigeminal Nerve ..Sensory to face (touch, pain and temperature) and muscles of mastication ..Damage produces loss of sensation and impaired chewing 44
  45. 45. VI. Abducens Nerve-Provides eye movement (lateral rectus m.) -Damage results in inability to rotate eye laterally and at rest eye rotates medially 45
  46. 46. VII. Facial Nerve• Motor - facial expressions; salivary glands and tear, nasal and palatine glands• Sensory - taste on anterior 2/3’s of tongue• Damage produces sagging facial muscles and disturbed sense of taste (no sweet and salty)
  47. 47. VIII. Vestibulocochlear Nerve-Provides hearing and sense of balance-Damage produces deafness, dizziness,nausea, loss of balance and nystagmus 47
  48. 48. IX. Glossopharyngeal Nerve• Swallowing, salivation, gagging and respiration• Sensations from posterior 1/3 of tongue• Damage results in loss of bitter and sour taste and impaired swallowing
  49. 49. X. Vagus Nerve• Swallowing, speech, regulation of viscera• Damage causes hoarseness or loss of voice, impaired swallowing and fatal if both are cut
  50. 50. XI. Accessory Nerve• Swallowing, head, neck and shoulder movement – damage causes impaired head, neck, shoulder movement; head turns towards injured side
  51. 51. XII. Hypoglossal Nerve• Tongue movements for speech, food manipulation and swallowing – if both are damaged – can’t protrude tongue – if one side is damaged – tongue deviates towards injured side
  52. 52. Spinal Nerves• There is a pair of spinal nerves at the level of each vertebrae.
  53. 53. Autonomic Nervous System• The involuntary branch of the nervous system• Consists of only motor nerves• Divided into two divisions • Sympathetic division • Parasympathetic division
  54. 54. Autonomic Functioning• Sympathetic – “fight-or-flight” • Response to unusual stimulus • Takes over to increase activities • Remember as the “E” division = exercise, excitement, emergency, and embarrassment
  55. 55. Autonomic Functioning• Parasympathetic – housekeeping activites • Conserves energy • Maintains daily necessary body functions • Remember as the “D” division - digestion, defecation, and diuresis