Neuroanatomy (Chapter 7)


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Neuroanatomy (Chapter 7)

  1. 1. Neuroanatomy
  2. 2. Anatomical Reference Points <ul><li>Directions in the nervous system </li></ul><ul><li>Define how the animal is oriented </li></ul><ul><li>Three major orthogonal axes, each with two directions and one perpendicular plane: </li></ul><ul><ul><li>1. Longitudinal axis </li></ul></ul><ul><ul><ul><li>(anterior-posterior axis) </li></ul></ul></ul><ul><ul><li>2. Vertical axis </li></ul></ul><ul><ul><ul><li>(dorsal-ventral axis) </li></ul></ul></ul><ul><ul><li>3. Side-to-side axis </li></ul></ul><ul><ul><ul><li>(lateral-medial axis) </li></ul></ul></ul>
  3. 3. Longitudinal axis (anterior-posterior) <ul><li>Anterior or rostral </li></ul><ul><ul><li>toward the nose of the animal </li></ul></ul><ul><li>Posterior or caudal </li></ul><ul><ul><li>toward the tail of the animal </li></ul></ul><ul><li>Coronal sections </li></ul><ul><ul><li>perpendicular to the longitudinal axis </li></ul></ul><ul><ul><li>One coronal section is either anterior or posterior to another coronal section </li></ul></ul>
  4. 4. Coronal Sections
  5. 5. Vertical axis (dorsal-ventral) <ul><li>Dorsal ( superior) </li></ul><ul><ul><li>toward the top (back) of the animal </li></ul></ul><ul><li>Ventral ( inferior) </li></ul><ul><ul><li>toward the bottom (belly) of the animal </li></ul></ul><ul><li>Horizontal sections </li></ul><ul><ul><li>perpendicular to the vertical axis, parallel to the ground </li></ul></ul><ul><ul><li>One horizontal section is either dorsal or ventral to another horizontal section </li></ul></ul>
  6. 6. Dorsal View
  7. 7. Ventral View
  8. 8. Horizontal Sections
  9. 9. Side-to-side axis (lateral-medial) <ul><li>Lateral </li></ul><ul><ul><li>away from the midplane at the center of the animal toward the side of the animal </li></ul></ul><ul><li>Medial </li></ul><ul><ul><li>toward the midplane at the center of the animal </li></ul></ul><ul><li>Sagittal sections </li></ul><ul><ul><li>Perpendicular to the lateral-medial axis, parallel to the midplane </li></ul></ul><ul><ul><li>One sagittal section is either medial or lateral to another sagittal section </li></ul></ul>
  10. 10. Sagittal Section
  11. 11. Dorsal/Ventral & Lateral/Medial
  12. 12. Orientation Issues <ul><li>There are problems in deciding the standard orientation of an animal. </li></ul><ul><li>Humans are upright; most mammals are prone. </li></ul><ul><li>For the human brain, the orientation of the head is used </li></ul><ul><li>For the human spinal cord, the person is prone </li></ul><ul><li>Therefore, for the brain, dorsal is toward the top of your head, but for the spinal cord, dorsal is toward your back </li></ul>
  13. 13. Orientation of the Human Brain
  14. 14. Divisions of the Nervous System <ul><li>2 main subdivisions: </li></ul><ul><li>Central Nervous System </li></ul><ul><ul><li>the brain & spinal cord </li></ul></ul><ul><li>Peripheral Nervous System - </li></ul><ul><ul><li>groups of neurons called ganglia and peripheral nerves </li></ul></ul><ul><ul><li>provides pathways to & from the central nervous system for electrochemical signals (impulses) </li></ul></ul>
  15. 16. The Peripheral Nervous System <ul><li>Composed of 2 divisions: </li></ul><ul><li>Somatic </li></ul><ul><ul><li>Provides sensory information (voluntary) </li></ul></ul><ul><ul><li>Transmits impulses to and from skeletal muscles - usually conscious actions </li></ul></ul><ul><li>Autonomic </li></ul><ul><ul><li>motor system for viscera (smooth muscles & glands-involuntary) </li></ul></ul><ul><ul><li>Autonomic is further divided into 3 subdivisions </li></ul></ul>
  16. 17. The Autonomic Nervous System <ul><li>3 subdivisions of Autonomic: </li></ul><ul><li>Sympathetic </li></ul><ul><ul><li>participates in body’s response to stress; fight or flight </li></ul></ul><ul><li>Parasympathetic </li></ul><ul><ul><li>returns body to resting state & conserves resources </li></ul></ul><ul><li>Enteric </li></ul><ul><ul><li>controls smooth muscles of the gut </li></ul></ul>
  17. 20. Orientation of the PNS <ul><li>Dorsal roots carry sensory info to the spinal cord </li></ul><ul><li>Ventral roots carry outgoing motor axons </li></ul><ul><li>Peripheral nerves formed from dorsal & ventral roots </li></ul><ul><li>Symmetry of PNS </li></ul><ul><ul><li>Arranged on 2 axis: </li></ul></ul><ul><ul><li>longitudinal: rostral to caudal ( head to tail) </li></ul></ul><ul><ul><li>dorsal to ventral (back to front) </li></ul></ul><ul><li>Segmented: </li></ul><ul><ul><li>31 pairs of spinal nerves </li></ul></ul><ul><ul><li>12 pairs of cranial nerves </li></ul></ul>
  18. 21. The Central Nervous System <ul><li>Consists of 7 Main Regions: </li></ul><ul><ul><li>Spinal Cord </li></ul></ul><ul><ul><li>Medulla </li></ul></ul><ul><ul><li>Pons </li></ul></ul><ul><ul><li>Midbrain </li></ul></ul><ul><ul><li>Cerebellum </li></ul></ul><ul><ul><li>Diencephalon </li></ul></ul><ul><ul><li>Cerebral Hemispheres </li></ul></ul>
  19. 22. The Spinal Cord <ul><li>Column of tissue from the brain thru the spinal column </li></ul><ul><ul><li>From base of skull thru 1 st lumbar vertebra; not entire length of spinal column </li></ul></ul><ul><ul><li>Thickness of a pencil; about 17&quot; long </li></ul></ul><ul><li>Links brain with nerves to all parts of the body </li></ul><ul><li>Contains ascending pathways through which sensory info reaches the brain & descending pathways that relay motor commands from the brain </li></ul>
  20. 23. The Reflex Arc <ul><li>Some involuntary movements are known as reflexes </li></ul><ul><li>Controlled by a pathway that goes only to the spinal cord, not the brain </li></ul><ul><li>Reflex arc </li></ul><ul><ul><li>just 2 or 3 neurons that form a loop to the spinal cord </li></ul></ul><ul><li>Faster – often defense mechanisms </li></ul>
  21. 24. Picturing the Reflex Arc
  22. 25. The Brain <ul><li>Remaining 6 areas of the CNS are part of the brain </li></ul><ul><li>The control center of the body </li></ul><ul><ul><li>Regulates body activity; enables you to think  </li></ul></ul><ul><li>Surface is gray matter - 6 x 10 6 cell bodies / cc </li></ul><ul><li>Under gray matter is white matter - formed of myelinated axons. </li></ul><ul><li>  Surface of the brain (neocortex) is convoluted </li></ul><ul><ul><li>Increases surface area </li></ul></ul><ul><ul><li>ridges = gyri </li></ul></ul><ul><ul><li>grooves = sulci </li></ul></ul>
  23. 27. Protection of the Brain & CNS <ul><li>The skull & spinal column </li></ul><ul><li>The Meninges </li></ul><ul><ul><li>3 layers of tissue protecting brain </li></ul></ul><ul><ul><li>Dura mater </li></ul></ul><ul><ul><ul><li>outer tough layer </li></ul></ul></ul><ul><ul><ul><li>Subdural space – normally small </li></ul></ul></ul><ul><ul><li>Arachnoid membrane </li></ul></ul><ul><ul><ul><li>next to dura mater </li></ul></ul></ul><ul><ul><ul><li>Subarachnoid space - spongy layer filled with cerebrospinal fluid and blood vessels </li></ul></ul></ul><ul><ul><li>Pia mater </li></ul></ul><ul><ul><ul><li>membrane that covers the brain </li></ul></ul></ul><ul><li>Cerebrospinal fluid (CSF) - cushions brain; circulates around the brain & spinal cord </li></ul>
  24. 28. Ventricles <ul><li>Chambers in the brain filled with CSF </li></ul><ul><ul><li>CSF is made cells of the choroid plexus in the ventricles </li></ul></ul><ul><ul><li>circulates to subarachnoid space; absorbed into the blood </li></ul></ul><ul><li>Lateral ventricles </li></ul><ul><ul><li>telencephalon (anterior forebrain) </li></ul></ul><ul><li>Third ventricle </li></ul><ul><ul><li>diencephalon (posterior forebrain) </li></ul></ul><ul><li>Cerebral aqueduct </li></ul><ul><ul><li>mesencephalon (midbrain) </li></ul></ul><ul><li>Fourth ventricle </li></ul><ul><ul><li>metencephalon and myelencephalon (hindbrain) </li></ul></ul><ul><li>Spinal canal </li></ul><ul><ul><li>spinal cord </li></ul></ul>
  25. 29. Brain Terminology <ul><li>Cortex </li></ul><ul><ul><li>thin sheet of neurons, usually at the surface </li></ul></ul><ul><li>Nucleus </li></ul><ul><ul><li>clearly separated group of neurons inside CNS </li></ul></ul><ul><li>Substantia </li></ul><ul><ul><li>like a nucleus, but less clearly delineated </li></ul></ul><ul><li>Locus </li></ul><ul><ul><li>a small, well defined group of cells in the CNS </li></ul></ul>
  26. 30. More Brain Terminology <ul><li>Ganglion </li></ul><ul><ul><li>collection of somata in the PNS </li></ul></ul><ul><ul><li>one group in the CNS - basal ganglia </li></ul></ul><ul><li>Tract </li></ul><ul><ul><li>bundle of CNS fibers with a common origin and destination </li></ul></ul><ul><li>Bundle </li></ul><ul><ul><li>CNS fibers that have more than one origin and destination </li></ul></ul><ul><li>Capsule </li></ul><ul><ul><li>fibers connecting cerebrum with the brain stem </li></ul></ul><ul><li>Commissure </li></ul><ul><ul><li>group of fibers crossing the midline </li></ul></ul>
  27. 31. The Hindbrain <ul><li>Developmental Division </li></ul><ul><li>Metencephalon </li></ul><ul><ul><li>Cerebellum (dorsal structure) </li></ul></ul><ul><ul><li>Pons (ventral structure) </li></ul></ul><ul><ul><li>Fourth ventricle </li></ul></ul><ul><li>Myelencephalon </li></ul><ul><ul><li>Medulla </li></ul></ul><ul><ul><li>Fourth ventricle </li></ul></ul>
  28. 32. The Medulla Oblongata & Pons <ul><li>Medulla Oblongata </li></ul><ul><ul><li>Bottom (rostral) region of the brainstem </li></ul></ul><ul><ul><li>Regulates blood pressure and respiration; controls breathing, swallowing, digestion, heart & blood vessels. </li></ul></ul><ul><li>Pons </li></ul><ul><ul><li>Above medulla </li></ul></ul><ul><ul><li>links cerebellum to cerebrum; relays info from cerebral hemispheres to cerebellum </li></ul></ul>
  29. 33. The Cerebellum <ul><li>Dorsal to the pons & medulla </li></ul><ul><li>Mostly white matter covered with a thin layer of gray matter </li></ul><ul><li>Pleated surface; divided into several lobes </li></ul><ul><li>Receives sensory input from the spinal cord, motor info from the cerebral cortex & input about balance from receptors in the inner ear </li></ul><ul><li>Therefore, can coordinate planning & timing of voluntary muscle movement & maintain balance </li></ul>
  30. 34. The Midbrain <ul><li>Mesencephalon </li></ul><ul><ul><li>Tectum (roof) </li></ul></ul><ul><ul><ul><li>superior colliculus + inferior colliculus </li></ul></ul></ul><ul><ul><li>Tegmentum (floor) </li></ul></ul><ul><ul><li>Cerebral aqueduct </li></ul></ul><ul><li>Controls responses to sight (e.g. eye movements) </li></ul><ul><li>Relay station of auditory & visual signals </li></ul><ul><li>Motor control of some skeletal muscles </li></ul>
  31. 35. The Brainstem <ul><li>Anatomically, from the bottom up: </li></ul><ul><ul><li>Medulla Oblongata </li></ul></ul><ul><ul><li>Pons </li></ul></ul><ul><ul><li>Midbrain </li></ul></ul><ul><li>Taken together = brainstem </li></ul><ul><ul><li>Contains all the nerves that connect the spinal cord with the cerebrum </li></ul></ul><ul><ul><li>Receives sensory info from head, face, & neck </li></ul></ul><ul><ul><li>Motor neurons control muscles of head & neck </li></ul></ul><ul><ul><li>12 pairs of cranial nerves carry input & output </li></ul></ul><ul><ul><li>Also involved in hearing, taste & balance </li></ul></ul>
  32. 36. The Reticular Formation <ul><li>A complex network of fibers that runs through the brain stem & thalamus. </li></ul><ul><li>Turns on the rest of the brain when a message is received </li></ul><ul><li>Acts as a filter (e.g. you sleep through noise) </li></ul><ul><li>Important role in consciousness, awareness, &quot;self&quot;, sleep </li></ul>
  33. 37. Visualizing the Reticular Formation
  34. 38. The Forebrain <ul><li>Telencephalon </li></ul><ul><ul><li>Olfactory bulb </li></ul></ul><ul><ul><li>Cerebral cortex </li></ul></ul><ul><ul><li>Basal telencephalon (basal ganglia) </li></ul></ul><ul><ul><li>Corpus callosum </li></ul></ul><ul><ul><ul><li>commissure between cerebral hemispheres </li></ul></ul></ul><ul><ul><li>Internal capsule </li></ul></ul><ul><ul><ul><li>connections with brain stem </li></ul></ul></ul><ul><ul><li>Lateral ventricles </li></ul></ul><ul><li>Diencephalon </li></ul>
  35. 39. Diencephalon <ul><li>Thalamus & hypothalamus taken together </li></ul><ul><li>Important structures found in the cerebrum </li></ul><ul><li>Between the midbrain & cerebral hemispheres </li></ul><ul><ul><li>Thalamus </li></ul></ul><ul><ul><li>Hypothalamus </li></ul></ul><ul><ul><li>Third ventricle </li></ul></ul><ul><li>Retina and optic nerves </li></ul><ul><ul><li>develop from optic vesicle that pouches off from diencephalon during development </li></ul></ul>
  36. 40. The Thalamus & Hypothalamus <ul><li>Thalamus </li></ul><ul><ul><li>relay center - processes & distributes almost all sensory & motor info going to the cerebral cortex </li></ul></ul><ul><ul><li>links nervous & endocrine system </li></ul></ul><ul><ul><li>emotional control </li></ul></ul><ul><li>Hypothalamus </li></ul><ul><ul><li>under the thalamus </li></ul></ul><ul><ul><li>regulates autonomic nervous system </li></ul></ul><ul><ul><li>connects to thalamus, midbrain & some cortical areas </li></ul></ul><ul><ul><li>Controls body temperature, thirst, hunger, emotional behavior </li></ul></ul>
  37. 41. Forebrain, Midbrain, Hindbrain
  38. 42. The Limbic System <ul><li>A functional & evolutionary division, rather than anatomical </li></ul><ul><li>Group of structures in center of the brain above the brainstem: </li></ul><ul><ul><li>hypothalamus </li></ul></ul><ul><ul><li>pituitary </li></ul></ul><ul><ul><li>hippocampus </li></ul></ul><ul><ul><ul><li>important role in memory </li></ul></ul></ul><ul><ul><li>hippocampal gyrus </li></ul></ul><ul><ul><li>amygdala </li></ul></ul><ul><ul><ul><li>coordinates actions of the autonomic & endocrine systems </li></ul></ul></ul><ul><ul><ul><li>involved in emotions </li></ul></ul></ul>
  39. 43. Functions of the Limbic System <ul><li>Sometimes called the “mammalian brain because most highly developed in mammals </li></ul><ul><li>One of the oldest areas of brain from an evolutionary standpoint </li></ul><ul><li>Maintains homeostasis: e.g. helps maintain temperature, blood pressure, heart rate, blood sugar </li></ul><ul><li>Also involved in emotional reactions needed for survival </li></ul><ul><li>4 F’s: fleeing, fighting, feeding & . . . </li></ul>
  40. 44. Visualizing the Limbic System
  41. 45. The Cerebral Hemispheres <ul><li>Largest region of brain; 7/8 by weight - Includes: </li></ul><ul><ul><li>Cerebral cortex – outer surface of gray matter </li></ul></ul><ul><ul><li>underlying white matter </li></ul></ul><ul><ul><li>3 nuclei (clusters of related neurons): </li></ul></ul><ul><ul><ul><li>the basal ganglia </li></ul></ul></ul><ul><ul><ul><li>the hippocampal formation </li></ul></ul></ul><ul><ul><ul><li>the amygdala </li></ul></ul></ul><ul><ul><ul><li>these are masses of gray matter at the base of the cerebrum that serve the motor cortex </li></ul></ul></ul><ul><ul><li>paired cavities =   lateral ventricles </li></ul></ul><ul><ul><li>Divided into 2 ‘half spheres’ = hemisheres </li></ul></ul>
  42. 46. The Cerebral Cortex <ul><li>The convoluted outer surface </li></ul><ul><ul><li>grooves = sulci </li></ul></ul><ul><ul><li>elevated regions = gyri </li></ul></ul><ul><li>Composed of gray matter </li></ul><ul><li>2-5 mm thick </li></ul><ul><li>Contains ~ 12 billion neurons </li></ul><ul><li>Most of the cerebral cortex is concerned with processing sensory information or motor commands </li></ul><ul><li>2 bands of tissue – one sensory, one motor </li></ul><ul><li>Divided into primary, secondary, & tertiary </li></ul>
  43. 47. The Primary Sensory & Motor Cortex <ul><li>Primary Motor Cortex: </li></ul><ul><ul><li>controls voluntary movements of limbs & trunk </li></ul></ul><ul><ul><li>contains neurons that project directly to spinal cord to activate somatic motor neurons </li></ul></ul><ul><li>Primary Sensory Areas </li></ul><ul><ul><li>receive information from peripheral receptors with only a few synaptic relays interposed </li></ul></ul>
  44. 48. Brodmann Areas <ul><li>Cytoarchitectural areas of neocortex </li></ul><ul><li>Regions with similar cell structure </li></ul><ul><li>Numbered </li></ul><ul><ul><li>each represents a functionally distinct area </li></ul></ul><ul><li>Examples: </li></ul><ul><ul><li>Area 17 is the primary visual cortex </li></ul></ul><ul><ul><ul><li>at the caudal pole of the occipital lobe </li></ul></ul></ul><ul><ul><li>Area 4 is the primary motor cortex </li></ul></ul><ul><ul><li>primary auditory cortex on left side of temporal lobe near language center </li></ul></ul>
  45. 49. Secondary & Tertiary Areas <ul><li>Surrounding primary areas are higher order ( secondary & tertiary ) sensory & motor areas </li></ul><ul><ul><li>Process & integrate info coming from the primary sensory areas. </li></ul></ul><ul><li>Higher order motor areas send complex info required for motor actions to primary motor areas </li></ul><ul><li>  </li></ul>
  46. 50. Association Areas <ul><li>Three other large regions of cortex surround the primary, secondary & tertiary areas </li></ul><ul><li>Called association areas </li></ul><ul><li>In primates, association areas are majority of cortex </li></ul>
  47. 51. Localization of Cortical Functions
  48. 52. Lobes of the Cerebrum <ul><li>2 sides called hemispheres </li></ul><ul><li>Joined by a bridge = Corpus Callosum </li></ul><ul><li>Separated by a deep fissure front to back </li></ul><ul><li>Like 2 mirror images (but not quite) </li></ul><ul><li>Divided into 4 lobes </li></ul><ul><ul><li>1. Frontal </li></ul></ul><ul><ul><li>2. Parietal </li></ul></ul><ul><ul><li>3. T emporal </li></ul></ul><ul><ul><li>4. O ccipital </li></ul></ul>
  49. 53. Lobes of the Brain & Associated Regions
  50. 54. The Frontal Lobe <ul><li>intellectual functioning </li></ul><ul><li>reasoning </li></ul><ul><li>aggression </li></ul><ul><li>sexual behavior </li></ul><ul><li>speech </li></ul><ul><li>smell </li></ul><ul><li>voluntary movements </li></ul>
  51. 55. The Parietal Lobe <ul><li>body sensory awareness (including taste) </li></ul><ul><li>language </li></ul><ul><li>abstract thought, especially math </li></ul><ul><li>body imaging </li></ul>
  52. 56. The Temporal Lobe <ul><li>includes part of limbic system* </li></ul><ul><li>emotion* </li></ul><ul><li>interpretation of language </li></ul><ul><li>hearing </li></ul><ul><li>memory </li></ul>
  53. 57. The Occipital Lobe <ul><li>receiving, interpreting, & discriminating visual stimuli </li></ul><ul><li>association of visual stimuli with memory </li></ul>
  54. 58. Integration of Brain Functions <ul><li>Interactions of all areas sensory, motor & motivational systems is essential for behavior. </li></ul><ul><li>Example: throw a ball - info about motion of ball, impact of ball, position of arms, legs, hands, etc. - sensory, motor, motivational systems </li></ul><ul><li>Anatomical organization of each major functional system (sensory, motor, motivational) follows 4 principles </li></ul>
  55. 59. Principles of Anatomical Organization <ul><li>Each system contains relay centers </li></ul><ul><ul><li>These don’t just transmit info; also modify it </li></ul></ul><ul><ul><li>Most important relay center is the thalamus </li></ul></ul><ul><ul><li>almost all sensory info to cerebral cortex processed by thalamus </li></ul></ul><ul><li>Each system is composed of several distinct pathways </li></ul><ul><ul><li>Example: touch & pain </li></ul></ul>
  56. 60. Principles of Anatomical Organization (Cont.) <ul><li>Each pathway is topographically organized </li></ul><ul><ul><li>neural map - clustered functions </li></ul></ul><ul><li>Most pathways cross the body’s midline </li></ul><ul><ul><li>Thus each hemisphere controls the actions/sensations of the opposite side. </li></ul></ul><ul><ul><li>Left side dominates language; right side -spatial perception, musical ability </li></ul></ul>
  57. 61. Ipsilateral/Contralateral <ul><li>The cerebral hemispheres are involved with inputs and outputs from the contralateral side of the body </li></ul><ul><ul><li>Damage to neocortex causes problems on the opposite side </li></ul></ul><ul><ul><li>In patients with epilepsy, surgeons occasionally cut corpus callosum to relieve seizures. Flash different pictures in each eye, patients could describe what they saw with right eye, but not left, but could pick out object - example: Heart = ART. </li></ul></ul><ul><li>The cerebellum is involved with the control of movement on the ipsilateral side of the body. </li></ul><ul><ul><li>Damage to the cerebellum causes motor deficits on the same side. </li></ul></ul>
  58. 62. Use it or Lose it! <ul><li>It is the neocortex that makes us humans </li></ul><ul><li>Genetics has much to do with neocortical circuitry </li></ul><ul><li>Environment and experience, however, modify neocortical circuitry </li></ul><ul><li>Like your body, failing to exercise your mind modifies it (and not for the better) </li></ul>