Human Anatomy,  Second Edition McKinley & O'Loughlin Chapter 17 Lecture Outline: Pathways and Integrative Functions
General Characteristics of Nervous System Pathways <ul><li>CNS communicates with body structures via pathways.   </li></ul...
Nervous System Pathways <ul><li>Consist of a tract and a nucleus.  </li></ul><ul><li>Tracts  are groups or bundles of axon...
Nervous System Pathways <ul><li>Ascending pathways carry sensory information </li></ul><ul><li>Descending pathways transmi...
Nervous System Pathways <ul><li>Most exhibit a precise correspondence between receptors through axons to specific function...
Nervous System Pathways <ul><li>Tracts named for </li></ul><ul><ul><li>white column they are in </li></ul></ul><ul><ul><li...
Sensory Pathways <ul><li>Sensory pathways   </li></ul><ul><ul><li>conduct information about limb position and the sensatio...
Sensory Receptors <ul><li>Detect stimuli  and then conduct nerve impulses to the CNS  </li></ul><ul><li>Sensory pathway ce...
Functional Anatomy of Sensory Pathways <ul><li>Use  two or three neurons  to transmit stimulus information from the body p...
Primary (First-Order) Neuron  <ul><li>The dendrites are part of the receptor that detects a specific stimulus.  </li></ul>...
Secondary (Second-Order) Neuron <ul><li>The axon of the primary neuron projects to a secondary neuron within the CNS.  </l...
Tertiary (Third-Order) Neuron <ul><li>Also an  interneuron. </li></ul><ul><li>Its cell body resides within the thalamus.  ...
Posterior Funiculus-Medial Lemniscal Pathway <ul><li>Projects through the spinal cord, brainstem, and diencephalon to the ...
Anterolateral (Spinothalamic) Pathway <ul><li>Located in the anterior and lateral white funiculi of the spinal cord.  </li...
Spinocerebellar Pathway <ul><li>Conducts  subconscious proprioceptive information  to the cerebellum for processing to coo...
Integration of Sensory Information <ul><li>Sensory information joins a large pool of sensory input - not all acted upon. <...
Motor Pathways <ul><li>The motor response may initiate at any level. </li></ul><ul><li>Descending pathways in the brain an...
Motor Pathways <ul><li>At least two motor neurons in the somatic motor pathway: </li></ul><ul><ul><li>Upper motor neuron :...
Motor Pathways <ul><li>The cerebral motor cortex has the most control over precise skeletal muscle movements. </li></ul><u...
Direct (Pyramidal) Pathways <ul><li>Pyramidal tracts </li></ul><ul><ul><li>Corticobulbar -> head and neck </li></ul></ul><...
Corticobulbar Tracts <ul><li>Originate  from the facial region  of the motor homunculus within the primary motor cortex.  ...
Corticospinal Tracts <ul><li>The upper motor neurons descend from the cerebral cortex through the brainstem and form a pai...
Indirect (Extrapyramidal) Pathways <ul><li>Several nuclei within the brainstem initiate motor commands for activities that...
Functions of Indirect Pathways <ul><li>Program automatic movements </li></ul><ul><li>Help coordinate body movements with v...
Final Common Pathway <ul><li>There is a converging pathway of upper motor neurons to the lower motor neuron . </li></ul><u...
Role of the Cerebral Nuclei <ul><li>Receive impulses from the entire cerebral cortex </li></ul><ul><li>Most of the output ...
Role of the Cerebellum <ul><li>Active in learning and performing rapid, coordinated, highly skilled movements </li></ul><u...
Somatic Motor Control <ul><li>Several regions of the brain participate in the control of motor activities.  </li></ul><ul>...
Levels of Processing and Motor Control <ul><li>Simple reflexes that stimulate motor neurons represent the lowest level of ...
Cerebral Cortex <ul><li>Control highly variable and complex voluntary motor patterns.  </li></ul><ul><li>Occupy the highes...
Cerebrovascular Accident (CVA or Stroke) <ul><li>Most common brain disorder and the 3rd most common cause of death in the ...
Higher-Order Processing and Integrative Functions <ul><li>Higher-order mental functions:  </li></ul><ul><ul><li>consciousn...
Development and Maturation of Higher-Order Processing <ul><li>From infancy on, our motor control and processing capabiliti...
Cerebral Lateralization <ul><li>Each hemisphere tends to be specialized for certain tasks. </li></ul><ul><li>Higher-order ...
Cerebral Lateralization <ul><li>Left hemisphere is the categorical hemisphere and it functions in categorization and symbo...
Cerebral Lateralization <ul><li>Right hemisphere is called the representational hemisphere. </li></ul><ul><ul><li>concerne...
Cerebral Lateralization <ul><li>Use both hemispheres for most activities, share memories, look almost identical </li></ul>...
Hemispherectomies and Cerebral Lateralization <ul><li>Epilepsy usually originates in one hemisphere </li></ul><ul><li>Dras...
Language <ul><li>Higher-order processes involved in language include reading, writing, speaking, and understanding words <...
Language <ul><li>Wernicke’s area is in the categorical hemisphere </li></ul><ul><li>The corresponding area in the represen...
<ul><li>Include awareness, knowledge, memory, perception and thinking </li></ul><ul><li>Association areas (70% of cerebrum...
<ul><li>An inherited learning disability, characterized by problems with single-word decoding </li></ul><ul><li>May have p...
<ul><li>Different lengths of time and storage capacity </li></ul><ul><li>Sensory memory occurs when we form important asso...
<ul><li>Short-term memory  follows sensory memory, associations based on sensory input </li></ul><ul><ul><li>Limited capac...
Memory <ul><li>Brain must organize complex info into STM before storing it in LTM. </li></ul><ul><li>Conversion of STM to ...
<ul><li>Includes awareness of sensation, voluntary control of motor activities, and activities for higher mental processin...
<ul><li>The reticular formation is a functional brain system with motor and sensory components </li></ul><ul><ul><li>The m...
Consciousness <ul><li>Levels of consciousness are continuous from sleep to alertness </li></ul><ul><li>RAS processes visua...
<ul><li>Syncope or fainting </li></ul><ul><li>Stupor - hard to arouse </li></ul><ul><li>Coma - can’t arouse or respond to ...
<ul><li>Noticeable effects of aging on the brain and nervous system start about 30 yrs. </li></ul><ul><li>Decrease in the ...
<ul><li>Leading cause of dementia, loss of cognitive abilities.   </li></ul><ul><ul><li>11% of people over 65 yrs. </li></...
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Chapter 17, Sp 10

  1. 1. Human Anatomy, Second Edition McKinley & O'Loughlin Chapter 17 Lecture Outline: Pathways and Integrative Functions
  2. 2. General Characteristics of Nervous System Pathways <ul><li>CNS communicates with body structures via pathways. </li></ul><ul><ul><li>sensory or motor information </li></ul></ul><ul><ul><li>processing and integration occur continuously along them </li></ul></ul><ul><li>Pathways travel through the white matter of the spinal cord. </li></ul>17-
  3. 3. Nervous System Pathways <ul><li>Consist of a tract and a nucleus. </li></ul><ul><li>Tracts are groups or bundles of axons that travel together in the CNS. </li></ul><ul><ul><li>Each tract may work with multiple nuclei groups in the CNS. </li></ul></ul><ul><li>A nucleus is a collection of neuron cell bodies located within the CNS. </li></ul>17-
  4. 4. Nervous System Pathways <ul><li>Ascending pathways carry sensory information </li></ul><ul><li>Descending pathways transmit motor information </li></ul><ul><li>90% of pathways cross over from one side of the body to the other side at some point ( decussate ). </li></ul><ul><ul><li>The left side of the brain processes information from the right side of the body, and vice versa. </li></ul></ul>17-
  5. 5. Nervous System Pathways <ul><li>Most exhibit a precise correspondence between receptors through axons to specific functional areas of the cerebral cortex or between the primary motor cortex and specific body regions that it controls (somatotopy ). </li></ul><ul><li>All pathways are composed of paired tracts. Both left and right tracts are needed to innervate the body. </li></ul><ul><li>Pathways are a series of two or three neurons that work together. </li></ul>17-
  6. 6. Nervous System Pathways <ul><li>Tracts named for </li></ul><ul><ul><li>white column they are in </li></ul></ul><ul><ul><li>where cell bodies originate </li></ul></ul><ul><ul><li>where axons terminate </li></ul></ul><ul><ul><li>Examples </li></ul></ul><ul><ul><ul><li>Anterior spinothalamic tracts </li></ul></ul></ul><ul><ul><ul><ul><li>Ascending or descending? </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sensory or motor? </li></ul></ul></ul></ul><ul><ul><ul><li>Corticospinal tracts </li></ul></ul></ul><ul><ul><ul><ul><li>Ascending or descending? </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sensory or motor? </li></ul></ul></ul></ul>17-
  7. 7. Sensory Pathways <ul><li>Sensory pathways </li></ul><ul><ul><li>conduct information about limb position and the sensations such as touch, temperature, pressure, and pain </li></ul></ul><ul><ul><li>Somatosensory pathways </li></ul></ul><ul><ul><ul><li>process stimuli received from receptors within the skin, muscles, and joints </li></ul></ul></ul><ul><ul><li>Viscerosensory pathways </li></ul></ul><ul><ul><ul><li>process stimuli received from the viscera </li></ul></ul></ul>17-
  8. 8. Sensory Receptors <ul><li>Detect stimuli and then conduct nerve impulses to the CNS </li></ul><ul><li>Sensory pathway centers within either the spinal cord or brainstem process and filter the incoming sensory information. </li></ul><ul><ul><li>More than 99% of incoming impulses do not reach the cerebral cortex and our conscious awareness! </li></ul></ul>17-
  9. 9. Functional Anatomy of Sensory Pathways <ul><li>Use two or three neurons to transmit stimulus information from the body periphery to the brain </li></ul>17-
  10. 10. Primary (First-Order) Neuron <ul><li>The dendrites are part of the receptor that detects a specific stimulus. </li></ul><ul><li>The cell bodies reside in the posterior root ganglia of spinal nerves or the sensory ganglia of cranial nerves. </li></ul>17-
  11. 11. Secondary (Second-Order) Neuron <ul><li>The axon of the primary neuron projects to a secondary neuron within the CNS. </li></ul><ul><li>It is an interneuron. </li></ul><ul><li>The cell body resides within either the posterior horn of the spinal cord or a medulla oblongata nucleus. </li></ul><ul><li>The axon projects to the thalamus , where it synapses with the tertiary neuron. </li></ul><ul><li>The second-order neuron is the one that crosses to the other side! </li></ul>17-
  12. 12. Tertiary (Third-Order) Neuron <ul><li>Also an interneuron. </li></ul><ul><li>Its cell body resides within the thalamus. </li></ul><ul><li>The thalamus is the central processing and coding center for almost all sensory information. </li></ul><ul><li>It extends to the cerebral cortex . </li></ul>17-
  13. 13. Posterior Funiculus-Medial Lemniscal Pathway <ul><li>Projects through the spinal cord, brainstem, and diencephalon to the cerebral cortex. </li></ul><ul><ul><li>Tracts within the spinal cord (posterior funiculus or column)) </li></ul></ul><ul><ul><li>Tracts from the brainstem to the thalamus (medial lemniscus) </li></ul></ul><ul><li>Conducts sensory stimuli concerned with conscious proprioceptive information about limb position and discriminative (fine) touch, precise pressure, and vibration sensations. </li></ul><ul><ul><li>Fasciculus gracilis - lower body </li></ul></ul><ul><ul><li>Fasciculus cuneatus - upper body </li></ul></ul>17-
  14. 14.
  15. 15.
  16. 16. Anterolateral (Spinothalamic) Pathway <ul><li>Located in the anterior and lateral white funiculi of the spinal cord. </li></ul><ul><ul><li>anterior spinothalamic tract - itch, tickle, crude touch, pressure </li></ul></ul><ul><ul><li>lateral spinothalamic tract - pain and temperature </li></ul></ul><ul><li>Axons projecting from primary neurons enter the spinal cord and synapse on secondary neurons within the posterior horns. </li></ul><ul><li>Axons of the secondary neurons cross over to the opposite side of the spinal cord through the anterior white commissure before ascending toward the thalamus. </li></ul>17-
  17. 17.
  18. 18. Spinocerebellar Pathway <ul><li>Conducts subconscious proprioceptive information to the cerebellum for processing to coordinate body movements. </li></ul><ul><li>Information on proprioception stays on the same side </li></ul><ul><li>These are different from the other sensory pathways in that they do not use tertiary neurons. </li></ul><ul><ul><li>only primary and secondary neurons </li></ul></ul>17-
  19. 19.
  20. 20. Integration of Sensory Information <ul><li>Sensory information joins a large pool of sensory input - not all acted upon. </li></ul><ul><li>Integration in many regions with the help of association neurons (spinal cord, brain stem, cerebellum, cerebrum) </li></ul>17-
  21. 21. Motor Pathways <ul><li>The motor response may initiate at any level. </li></ul><ul><li>Descending pathways in the brain and spinal cord control the activities of skeletal muscles. </li></ul><ul><li>Formed from the cerebral nuclei, the cerebellum, descending projection tracts, and motor neurons </li></ul>17-
  22. 22. Motor Pathways <ul><li>At least two motor neurons in the somatic motor pathway: </li></ul><ul><ul><li>Upper motor neuron : within either the cerebral cortex or a nucleus within the brainstem. Axons of the upper motor neuron synapse either directly on lower motor neurons or on interneurons that synapse directly on lower motor neurons. May be excitatory or inhibitory on lower motor neuron. </li></ul></ul><ul><ul><li>Lower motor neuron : the cell body is in the anterior gray horn of the spinal cord or within a brainstem cranial nerve nucleus. Always excitatory on skeletal muscle fibers. </li></ul></ul>17-
  23. 23. Motor Pathways <ul><li>The cerebral motor cortex has the most control over precise skeletal muscle movements. </li></ul><ul><li>Most regulation of involuntary activities by the ANS originates in the brain stem and hypothalamus </li></ul><ul><li>After integration, there are 2 major descending tracts: </li></ul><ul><ul><li>Direct pathways responsible for conscious control of skeletal muscle activity </li></ul></ul><ul><ul><li>Indirect pathways responsible for unconscious control of skeletal muscle activity </li></ul></ul>17-
  24. 24. Direct (Pyramidal) Pathways <ul><li>Pyramidal tracts </li></ul><ul><ul><li>Corticobulbar -> head and neck </li></ul></ul><ul><ul><li>L ateral corticospinal -> L imbs </li></ul></ul><ul><ul><li>A nterior corticospinal -> A xial muscles </li></ul></ul>17-
  25. 25. Corticobulbar Tracts <ul><li>Originate from the facial region of the motor homunculus within the primary motor cortex. </li></ul><ul><li>Axons extend to the brainstem, where they synapse with lower motor neuron cell bodies that are housed within brainstem cranial nerve nuclei. </li></ul><ul><li>Axons of these lower motor neurons help form the cranial nerves . </li></ul>17-
  26. 26. Corticospinal Tracts <ul><li>The upper motor neurons descend from the cerebral cortex through the brainstem and form a pair of thick bulges in the medulla called the pyramids . </li></ul><ul><li>Continue into the spinal cord to synapse on lower motor neurons in the anterior horn of the spinal cord. </li></ul><ul><li>L ateral corticospinal tracts serve the l imbs </li></ul><ul><ul><li>cross in the medulla oblongata (90% of fibers) </li></ul></ul><ul><li>A nterior corticospinal tracts serve the a xial muscles </li></ul><ul><ul><li>cross in the spinal cord at the level of the lower motor neuron </li></ul></ul>17-
  27. 27.
  28. 28.
  29. 29. Indirect (Extrapyramidal) Pathways <ul><li>Several nuclei within the brainstem initiate motor commands for activities that occur at an unconscious level . </li></ul><ul><li>Multisynaptic and exhibit a high degree of complexity and circuitous routes. </li></ul><ul><li>Names do not include cortico!!! </li></ul><ul><ul><li>(Examples: rubrospinal, tectospinal, vestibulospinal, lateral reticulospinal, and medial reticulospinal) </li></ul></ul>17-
  30. 30.
  31. 31. Functions of Indirect Pathways <ul><li>Program automatic movements </li></ul><ul><li>Help coordinate body movements with visual stimuli </li></ul><ul><li>Maintain skeletal muscle tone and posture </li></ul><ul><li>Major role in equilibrium by regulating muscle tone in response to head movements </li></ul>17-
  32. 32. Final Common Pathway <ul><li>There is a converging pathway of upper motor neurons to the lower motor neuron . </li></ul><ul><li>These neurons may be excitatory and inhibitory from the direct and indirect pathways </li></ul><ul><li>The total determines the response </li></ul>17-
  33. 33. Role of the Cerebral Nuclei <ul><li>Receive impulses from the entire cerebral cortex </li></ul><ul><li>Most of the output goes to the primary motor cortex . </li></ul><ul><li>No direct control over lower motor neurons. </li></ul><ul><li>Provide the patterned background movements needed for conscious motor activities by adjusting the motor commands issued in other nuclei. </li></ul><ul><ul><li>Program habitual or automatic sequences and sets the appropriate muscle tone </li></ul></ul><ul><ul><li>Also selectively inhibit other motor neuron circuits </li></ul></ul>17-
  34. 34. Role of the Cerebellum <ul><li>Active in learning and performing rapid, coordinated, highly skilled movements </li></ul><ul><li>Maintains proper posture and equilibrium </li></ul><ul><li>Comparator function </li></ul><ul><ul><li>Monitors intentions (motor cortex, basal ganglia) </li></ul></ul><ul><ul><li>Monitors actual movement (proprioceptors) </li></ul></ul><ul><ul><li>Compares </li></ul></ul><ul><ul><li>Provides corrective feedback (nuclei of brainstem and motor cortex via thalamus) </li></ul></ul>17-
  35. 35. Somatic Motor Control <ul><li>Several regions of the brain participate in the control of motor activities. </li></ul><ul><li>Motor programs require conscious directions from the frontal lobes. </li></ul><ul><li>Movement is initiated when commands are received by the primary motor cortex from the motor association areas. </li></ul><ul><li>The cerebellum is critically important in coordinating movements because it specifies the exact timing of control signals to different muscles. </li></ul>17-
  36. 36. Levels of Processing and Motor Control <ul><li>Simple reflexes that stimulate motor neurons represent the lowest level of motor control. </li></ul><ul><li>The nuclei controlling these reflexes are located in the spinal cord and the brainstem. </li></ul><ul><li>Brainstem nuclei also participate in more complex reflexes. </li></ul><ul><li>Initiate motor responses to control motor neurons directly. </li></ul><ul><li>Oversee the regulation of reflex centers elsewhere in the brain . </li></ul>17-
  37. 37. Cerebral Cortex <ul><li>Control highly variable and complex voluntary motor patterns. </li></ul><ul><li>Occupy the highest level of processing and motor control. </li></ul><ul><li>Motor commands may be conducted to specific motor neurons directly. </li></ul><ul><li>May be conveyed indirectly by altering the activity of a reflex control center. </li></ul>17-
  38. 38. Cerebrovascular Accident (CVA or Stroke) <ul><li>Most common brain disorder and the 3rd most common cause of death in the US </li></ul><ul><li>Two types </li></ul><ul><ul><li>Ischemic from thrombus or embolus is most common </li></ul></ul><ul><ul><li>Hemorrhagic from ruptured blood vessel especially serious </li></ul></ul><ul><li>Consequences depend on location and duration </li></ul><ul><li>Transient ischemic attack (TIA), a “mini-stroke,” a temporary, but serious warning </li></ul><ul><li>Risk factors: age, family history, race and gender </li></ul><ul><li>Lifestyle changes and treatment can help </li></ul>17-
  39. 39. Higher-Order Processing and Integrative Functions <ul><li>Higher-order mental functions: </li></ul><ul><ul><li>consciousness, learning, memory, and reasoning </li></ul></ul><ul><ul><ul><li>occur within the cortex and involve multiple brain regions connected by complicated networks and arrays of axons </li></ul></ul></ul><ul><ul><ul><li>conscious and unconscious processing of information are involved in higher-order mental functions </li></ul></ul></ul><ul><ul><ul><li>may be continually adjusted or modified </li></ul></ul></ul>17-
  40. 40. Development and Maturation of Higher-Order Processing <ul><li>From infancy on, our motor control and processing capabilities increase in complexity . </li></ul><ul><ul><li>First year: increase number of cortical neurons </li></ul></ul><ul><ul><li>Most CNS neurons continue to myelinate during first 2 yrs. </li></ul></ul><ul><ul><li>Brain growth 95% complete by age 5 </li></ul></ul><ul><ul><li>Some CNS axons don’t myelinate until teens (e.g., in prefrontal cortex) </li></ul></ul><ul><ul><li>PNS neurons generally continue to myelinate past puberty </li></ul></ul><ul><li>The ability to carry out higher-order mental functions is a direct result of the level of nervous system maturation. </li></ul>17-
  41. 41. Cerebral Lateralization <ul><li>Each hemisphere tends to be specialized for certain tasks. </li></ul><ul><li>Higher-order centers in both hemispheres tend to have different but complementary functions . </li></ul>17-
  42. 42. Cerebral Lateralization <ul><li>Left hemisphere is the categorical hemisphere and it functions in categorization and symbolization . </li></ul><ul><ul><li>contains Wernicke’s area and the motor speech area </li></ul></ul><ul><ul><li>specialized for language abilities </li></ul></ul><ul><ul><li>important in performing sequential and analytical reasoning tasks (science and mathematics) </li></ul></ul><ul><ul><li>appears to direct or partition information into smaller fragments for analysis </li></ul></ul><ul><li>Speech-dominant hemisphere . </li></ul><ul><ul><li>controls speech in almost all right-handed people as well as in many left-handed ones </li></ul></ul>17-
  43. 43. Cerebral Lateralization <ul><li>Right hemisphere is called the representational hemisphere. </li></ul><ul><ul><li>concerned with visuospatial relationships and analyses </li></ul></ul><ul><ul><li>the seat of imagination and insight, musical and artistic skill, perception of patterns and spatial relationships, and comparison of sights, sounds, smells, and tastes </li></ul></ul><ul><li>Both cerebral hemispheres remain in constant communication through commissures , especially the corpus callosum, which contains hundreds of millions of axons that project between the hemispheres. </li></ul>17-
  44. 44.
  45. 45. Cerebral Lateralization <ul><li>Use both hemispheres for most activities, share memories, look almost identical </li></ul><ul><li>Cerebral dominance refers to language dominance, about 90% are left dominant </li></ul><ul><li>Usually, right-handed, but about 10% are reversed or shared. Lefties are more often male. </li></ul><ul><li>If shared dominance, then increased dexterity and strength in non-dominant hand and ambidexterity or cerebral confusion and learning disabilities, e.g., dyslexia </li></ul><ul><li>Each side exerts control over the other. Communication is good and fast through fiber tracts. Integrate functions well. </li></ul>17-
  46. 46. Hemispherectomies and Cerebral Lateralization <ul><li>Epilepsy usually originates in one hemisphere </li></ul><ul><li>Drastic removal of the hemisphere is used in some very severe cases </li></ul><ul><li>High success rate in stopping epilepsy but brain function not returned to normal </li></ul><ul><li>Remaining hemisphere can take over some functions of removed hemisphere especially in younger patients </li></ul>17-
  47. 47. Language <ul><li>Higher-order processes involved in language include reading, writing, speaking, and understanding words </li></ul><ul><li>Wernicke’s area key to ability to recognize written and spoken language </li></ul>17-
  48. 48. Language <ul><li>Wernicke’s area is in the categorical hemisphere </li></ul><ul><li>The corresponding area in the representational hemisphere recognizes the emotional content of speech . A lesion here results in an inability to understand emotional nuances in speech. </li></ul><ul><li>A lesion in the representational area opposite Broca’s area results in speech without emotional content </li></ul>17-
  49. 49. <ul><li>Include awareness, knowledge, memory, perception and thinking </li></ul><ul><li>Association areas (70% of cerebrum) are responsible for cognition and processing and integration of info between sensory input and motor output areas </li></ul><ul><li>The frontal association area, prefrontal cortex, integrates info from sensory, motor, and association areas to enable thinking, planning and executing appropriate behavior (remember Phineas Gage) </li></ul>Cognition 17-
  50. 50. <ul><li>An inherited learning disability, characterized by problems with single-word decoding </li></ul><ul><li>May have problems with reading, writing and spelling accurately </li></ul><ul><li>Occasionally, the ability to recognize and interpret the meaning of pictures and objects is also impaired. </li></ul><ul><li>May improve in many over time. </li></ul><ul><li>Some researchers think it is a form of disconnect syndrome where information transfer through the corpus callosum is impaired </li></ul>Dyslexia 17-
  51. 51. <ul><li>Different lengths of time and storage capacity </li></ul><ul><li>Sensory memory occurs when we form important associations on sensory input - unlimited capacity </li></ul><ul><li>Working memory is necessary when we are trying to perform several different mental activities simultaneously </li></ul>Memory 17-
  52. 52. <ul><li>Short-term memory follows sensory memory, associations based on sensory input </li></ul><ul><ul><li>Limited capacity (7 bits of info) </li></ul></ul><ul><ul><li>Brief duration (seconds to hours) </li></ul></ul><ul><li>Long-term memory </li></ul><ul><ul><li>May last limitless time </li></ul></ul><ul><ul><li>Needs to be retrieved occasionally or be “lost” </li></ul></ul><ul><li>Ability to store and retrieve information decreases with age </li></ul>Memory 17-
  53. 53. Memory <ul><li>Brain must organize complex info into STM before storing it in LTM. </li></ul><ul><li>Conversion of STM to LTM is called encoding, or memory consolidation </li></ul><ul><ul><li>Requires proper functioning of amygdala and hippocampus </li></ul></ul><ul><li>Long-term memories are stored in the association areas </li></ul><ul><li>Different anatomic structures so the loss of the ability to form STM does not affect the maintenance or accessibility of LTM </li></ul>17-
  54. 54. <ul><li>Includes awareness of sensation, voluntary control of motor activities, and activities for higher mental processing </li></ul><ul><li>Reticular formation is in the brain stem and a bit in the diencephalon and spinal cord </li></ul>Consciousness 17-
  55. 55. <ul><li>The reticular formation is a functional brain system with motor and sensory components </li></ul><ul><ul><li>The motor component communicates with the spinal cord and regulates muscle tone esp. at rest and helps with autonomic motor functions </li></ul></ul><ul><ul><li>The reticular activating system (RAS) is the sensory component. Alerts the sensory cortex to incoming information through neurons. Responsible for maintaining a state of awareness (or consciousness), i.e., the physical basis for consciousness . </li></ul></ul>Consciousness 17-
  56. 56. Consciousness <ul><li>Levels of consciousness are continuous from sleep to alertness </li></ul><ul><li>RAS processes visual, auditory, and touch stimuli and uses this information to keep cortex alert </li></ul><ul><li>Filters and selects what info is sent on to the conscious mind: essential, unusual, dangerous </li></ul><ul><li>RAS arouses us from sleep. Lack of stimuli to RAS allows us to sleep. </li></ul><ul><li>Damage can lead to a coma </li></ul><ul><li>General anaesthetics suppress reticular activating system </li></ul>17-
  57. 57.
  58. 58.
  59. 59. <ul><li>Syncope or fainting </li></ul><ul><li>Stupor - hard to arouse </li></ul><ul><li>Coma - can’t arouse or respond to environment </li></ul><ul><li>Persistent vegetative state - may follow a coma, may look somewhat normal and have spontaneous movements but unable to speak and do not respond to commands </li></ul>Pathologic States of Unconsciousness 17-
  60. 60. <ul><li>Noticeable effects of aging on the brain and nervous system start about 30 yrs. </li></ul><ul><li>Decrease in the number of neurons and, therefore, number of synapses and decrease in sensory info </li></ul><ul><li>Decreased blood flow so less nutrients and less waste removal </li></ul><ul><li>Above lead to impaired cognitive capacity </li></ul>Aging and the Nervous System 17-
  61. 61. <ul><li>Leading cause of dementia, loss of cognitive abilities. </li></ul><ul><ul><li>11% of people over 65 yrs. </li></ul></ul><ul><ul><li>4th leading cause of death in elderly </li></ul></ul><ul><li>Cause: ? Genetics and environment may play a role </li></ul><ul><li>Changes in brain: </li></ul><ul><ul><li>Cerebral atrophy, neurofibrillary tangles, amyloid precursor protein seen at autopsy </li></ul></ul><ul><ul><li>Histological changes esp. in hippocampus </li></ul></ul><ul><ul><li>Decreased neurotransmitter, acetylcholine </li></ul></ul><ul><li>Symptoms: </li></ul><ul><ul><li>Memory loss, confusion, disorientation, episodes of paranoia, hallucination, or violent changes in mood </li></ul></ul><ul><li>No cure yet but some treatments help </li></ul>Alzheimer Disease: The “Long Goodbye” 17-

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