3rd class dr.ali boresliy

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3rd class dr.ali boresliy

  1. 1. Central Nervous System (CNS)Physiology 152 – Allied Health
  2. 2. What is the CNS? CNS Consists of Brain Spinal Cord CNS Receives input from Sensory Neurons Directs activity of Motor Neurons Associates motor response(s) with sensory stimuli through Association Neurons to maintain homeostasis
  3. 3. CNS in Vertebrates CNS of all vertebrates are at least capable of very basic forms of learning and memory Human CNS capabilities allow for:  Behavioral modification based on experience  Perceptions  Learning and Memory  Emotions  Self-awareness  Direct motor activity
  4. 4. Embryonic Development of the CNSFigure: http://faculty.washington.edu/chudler/dev.html
  5. 5. Embryonic Development of the CNS (for student reference) Ectoderm is the initial embryonic tissue that develops into the nervous system, the epidermis of skin as well as other structures (slide 4) At 2 weeks of embryonic development the neural plate is formed (slide- 4) A few days after the neural plate is formed, a groove is formed in the neural plate; creating the neural groove (slide 4) The part of the ectoderm where the fusion of the two ends of the neural groove occurs creates a separate structure called the neural crest (slide 4) Eventually, the neural tube will become the CNS and the neural crest will develop into the ganglia of the peripheral nervous system (PNS) (slide 4) By middle of week 4, since gestation, 3 distinct swellings are evident on the anterior end of the neural tube which will form the brain (forebrain, midbrain, and hindbrain) (slide 6) During the 5th week, a five-regioned brain develops and specific structures begin to form (slide 6)
  6. 6. Embryonic Development of the CNSFigure: http://faculty.irsc.edu/FACULTY/TFischer/AP1/AP%201%20resources.htm
  7. 7. Overview: Brain Development SequenceFigure: http://faculty.washington.edu/chudler/dev.html
  8. 8. CNS Composition Gray matter  Consists of neuron cell bodies and dendrites  Present in the surface layer (cortex) of the brain  Present deeper within the brain (subcortical) in aggregations called nuclei White matter  Consists of axon tracts  Underlie cortex and surround nuclei  Myelin Sheath give white matter the white color Adult brain  Contains ~100 billion neurons  Weighs approximately 1.5 kg  Receives 20% of total per minute body blood flow
  9. 9. Cerebrum  The only structure of the telencephalon  Accounts for 80% of brain’s mass  Primarily responsible for higher mental functions  Consists of right and left hemispheres (connected by corpus callosum)Figure: Alan Hoffring/National Cancer Institute
  10. 10. Cerebral Cortex  Is the outer layer of the cerebrum  Composed of 2-4 mm of gray matter and underlying white matter  Characterized by many convolutions  Gyriare the elevated fold of the convolutions  Sulciare the depressed grooves of the convolutions
  11. 11. Cerebral Cortex  Eachcerebral hemisphere is subdivided by deep sulci or fissures  Cerebral subdivisions:  Frontal lobe  Parietal lobe  Temporal lobe  Occipital lobe  Insula (insular lobe)
  12. 12. Cerebral Cortex  Frontal lobe  Anterior portion of each cerebral hemisphere  Central Sulcus (fissure) separates frontal lobe from parietal lobe  Functions: personality, higher intellectual processes, decision making
  13. 13. Cerebral Cortex  Parietal lobe  Positioned superior to the occipital lobe in both hemispheres  Parieto-occipital sulcus (fissure) separates parietal lobe from the occipital lobe  Lateral sulcus or Sylvian fissure separates the parietal lobe from the temporal lobe  Functions: understanding speech, formulating words, interpretation of textures and shapes
  14. 14. Cerebral Cortex  Occipital lobe  Is the rearmost and posterior part of the cerebral hemispheres  Functions: Focusing the eye, correlation of visual images, conscious perception of vision
  15. 15. Cerebral Cortex  Temporal lobe  Bordered by parietal lobe, frontal lobe, and occipital lobe in both hemispheres  Located beneath the lateral sulcus (Sylvian fissure)  Functions: processing of sensory inputs, language comprehension, memory
  16. 16. Cerebral Cortex  Insula  Situated deep within the lateral sulcus  Functions: Memory, integration of cerebral activities
  17. 17. Motor and Sensory Areas  Precentralgyrus is the motor area of the brain  Postcentralgyrusis the sensory area of the brain  Homunculus map is a representation of the contralateral sensory/motor side of the bodyFigure: http://med-review.blogspot.com/
  18. 18. Motor and Sensory Areas The size of the mapped body region in the precentral (motor) gyrus is reflective of the number of the motor innervations. For i.e. the largest areas in the motor cortex represent body regions with largest number of motor innervations. The size of the mapped body region in the postcentral (sensory) gyrus is reflective of the density of receptors. For i.e. the largest areas in the sensory cortex represent body regions with highest densities of receptors.
  19. 19. Language and Aphasiology  In the last century, understanding of brain function has been governed by study methodologies such as aphasiology  Aphasiologyis the study of language impairment through brain damage
  20. 20. Language and Aphasiology  Aphasiology research helped define two loosely defined brain regions in the left cortical hemisphere:  Broca’s area Function: speech production  Wernicke’s area Function: understanding written and spoken language
  21. 21. Language and Aphasiology Broca and Wernicke’s areas are connected by a fiber tract called arcuate fasciculus. It appears that the words form and are conceptualized in the Wernicke’s area and are communicated via Broca’s area
  22. 22. Cerebral Lateralization  Each cerebral cortex controls movement of the contralateral (opposite) side of the body  Somatesthetic sensation from each side of the body projects to the contraletralpostcentralgyru s  Right and left cerebral hemispheres communicate via a large fiber tract called the corpus callosum
  23. 23. Cerebral Lateralization Experiments have shown:  Right hemisphere has limited verbal ability  Right hemisphere is better at recognizing faces  Analytical and language abilities are characteristics of the left hemisphere  Visuospatial ability is a characteristic of the right hemisphere
  24. 24. Basal Nuclei  Are masses of gray matter situated deep within the white matter of the cerebrum  Prominent structure is the corpus striatum (composed of caudate nucleus and putamen)  Controls voluntary movementFigure: Brain E-Books brainmind.net
  25. 25. Thalamus  Situated between cerebral cortex and midbrain  Functions as a relay station to the cerebral cortex for sensory (except smell) signals  Is involved in regulation of sleep and consciousnessFigure: Brain E-Books brainmind.net
  26. 26. Limbic System  Amygdala  Involved in memory and emotional processing  Is part of the medial temporal lobe and is involved in consolidating short-term memory into long-term memory.  Note: When the consolidation process is over, long-term memory is independent of the medial temporal lobe  Septum  Involved in pleasure
  27. 27. Limbic System  Cingulate Cortex  Involved in pain and visceral response  Hippocampus  Is a critical part of the memory system  Is part of the medial temporal lobe and is involved in consolidating short-term memory into long-term memory  Fornix  Carries signals from hippocampus to hypothalamus
  28. 28. Hypothalamus  Involved in:  Reward processing  Punishment processing  Regulates:  Pituitary gland  Blood pressure  Hunger  Thirst  Metabolism  Heart rate
  29. 29. Emotion and Motivation Brain regions of paramount importance in emotion and motivation:  Hypothalamus  Limbic system Experiments have shown the hypothalamus and limbic system to be involved in the following feelings and behaviors:  Aggression  Stimulation of amygdala produces rage and aggression  Lesions of amygdala results in docility (docile: easily handled/taught)
  30. 30. Emotion and Motivation Experiments have shown the hypothalamus and limbic system to be involved in the following feelings and behaviors (con’t):  Fear  Produced by stimulation of amygdala and hypothalamus  Removal of limbic system results in absence of fear  Feeding  Hypothalamus contains both feeding center and satiety center  Stimulation of the feeding center will result in overeating  Stimulation of the satiety center results in stop of feeding behavior
  31. 31. Emotion and Motivation Experiments have shown the hypothalamus and limbic system to be involved in the following feelings and behaviors (con’t):  Sex  Hypothalamus and limbic system are involved in sexual drive and sexual behaviors  Goal-directed behavior (reward and punishment system)  Stimulation of certain parts of the hypothalamus can be more rewarding than food or sex in motivating behavior.  Stimulation of other parts of the hypothalamus stimulate a punishment system
  32. 32. Memory Amnesia (loss of memory) found to result from:  Damage to the temporal lobe  Damage to the hippocampus  Damage to the caudate nucleus (i.e. Huntington’s disease)  Damage to the dorsomedial thalamus (i.e. alcoholoics suffering from Koraskoff’s syndrome with thiamine/vitamin B1 deficiency)
  33. 33. Modern-day techniques for studying brain function Magnetoencephlography (MEG)  Measures brain activity through transmitted magnetic fields produced by electrical currents in the brain Electroencephlography (EEG)  Measures brain activity through direct measurement of electrical activity of the brain  Able to discern REM sleep (Rapid-eye movement sleep stage when dreams occur)
  34. 34. Modern-day techniques for studying brain function Four types of EEG patterns:  Alpha waves  Best recorded from parietal and occipital regions  Person is awake and relaxed with eyes closed  Frequency: 10-12 cycles/second  Child < 8 years old; Frequency : 4-7 cycles/second  Beta waves  Are strongest from the frontal lobes, especially the area near precentralgyrus  Frequency: 13-25 cycles/second
  35. 35. Modern-day techniques for studying brain function Four types of EEG patterns (Con’t):  Theta waves  Emitted from the temporal and occipital lobes  Frequency: 5-8 cycles/second  Delta waves  Emitted in a general pattern from the cerebral cortex  Frequency: 1-5 cycles/second
  36. 36. Modern-day techniques for studying brain function Positron Emission Tomography (PET)  Is a functional neuroimaging technique that uses injection of radioisotopes in the bloodstream to measure brain activity Functional Magnetic Resonance Imaging (fMRI)  Is a functional neuroimaging technique that measures brain activity by measuring associated changes in blood flow to any respective part of the brain or the brain as a whole
  37. 37. Modern-day techniques for studying brain function
  38. 38. Recap
  39. 39. Midbrain: Regions and Functions Corpora quadrigemina  Involved in visual reflex  Relay center for auditory information Cerebral peduncles  Pair of structures composed of ascending and descending fiber tracts Red nucleus  Area of gray matter deep in the midbrain  Maintains connections with cerebrum and cerebellum  Involved in motor coordination
  40. 40. Midbrain: Regions and Functions Substantianigra  Part of the Nigrostriatal system  Nigrostriatal system projects from the substantianigra to the corpus striatum of the basal nuclei  Nigrostriatal system is required of motor coordination  Degeneration of nigrostriatal fibers result in Parkinson’s Disease
  41. 41. Dopaminergic pathways  Mesolimbic dopamine system  Reward pathway  Axons use dopamine as a neurotransmitter (dopaminergic axons)  Axons leave the midbrain to the nucleus accumbens and prefrontal cortex
  42. 42. Dopaminergic pathways  Nigrostriatal dopamine system  Motor control pathway  Axons use dopamine as a neurotransmitter (dopaminergic axons)  Axons leave the substantianigra of the midbrain and synapse in the corpus striatum
  43. 43. Recap
  44. 44. Regions, Subregions, and Functions  Metencephelon  Pons  Surface fibers connect to the cerebellum  Deeper fibers are part of motor and sensory tracts passing from medulla oblongata  Holds nuclei associated with cranial nerves  Holds nuclei involved in breathing regulationFigure: http://www.knowabouthealth.com/normal-brain-communication-found-in-people-with-agenesis-of-the-corpus-callosum/8844/
  45. 45. Regions, Subregions, and Functions  Metencephelon (con’t)  Cerebellum  Second largest structure of the brain  Contains outer gray and inner white matter (like cerebrum)  Holds fibers that pass from cerebellum, pass through the red nucleus to the thalamus, and then to motor areas of the cerebral cortex
  46. 46. Regions, Subregions, and Functions  Metencephelon (con’t)  Cerebellum (con’t)  Holds fiber tracts that connect the cerebellum with the pons, medulla oblongata, and spinal cord  Recieves input from proprioceptors (joint,tendon, muscel receptors)  Heavily involved in coordination of movement
  47. 47. Hindbrain: Regions,Subregions, and Functions  Myelencephalon  Composed of only the Medulla Oblongata  Medulla Oblongata  Continuous between the pons and the spinal cord  All ascending and descending fiber tracts between spinal cord and brain pass through the medulla  Contains the pyramids where decussation of fibers occur  Contains nuclei involved in motor control, regulation of breathing and cardiovascular response
  48. 48. Reticular Formation  Complex network of nuclei within: medulla, pons, midbrain, thal amus, and hypothalamus  Functions as a reticular activating system (RAS)  Filters background stimuli  Regulates sleep-wake cycle  Regulates consciousness and sleep
  49. 49. 60 Minute episode on fMRI http://www.youtube.com/watch?v=8jc8URRxPIg
  50. 50. Spinal Cord  Runs in the vertebral column  Made up of white and gray matter  Gray matter is centrally located and surrounded by white matter (unlike the brain)
  51. 51. Spinal Cord  Gray matter forms an H in the center of the spinal cord with two dorsal horns and two ventral horns  White matter is made up of ascending and descending fiber tracts  Fiber tracts are arranged in 6 columns called funiculi
  52. 52. Spinal Cord Tracts Two types: Ascending and Descending Tracts Terminology:  Ascending tract names start with a prefix spino- and end with the brain region where the fibers first synapse (i.e. spinothalamic)  Descending tract names start with a prefix reflecting the brain region where the fibers start and ends with the suffix –spinal (i.e. corticospinal)
  53. 53. Spinal Cord Tracts Ascending Tracts  Fiber tracts that convey sensory information to the brain from receptors throughout the body  Two types of information  Exteroceptive: Arise from external environment of the body (i.e. pain, touch, temperature)  Proprioceptive: Arise from the internal environment of the body (i.e. muscles, joints)  Usually, sensory information from the right side of the body end up in the left hemisphere of the brain  Usually, sensory information from the left side of the body end up in the right hemisphere of the brain
  54. 54. Spinal Cord Tracts Ascending tracts (con’t)  Three types of neurons in ascending pathways  1st order sensory neurons  2nd order neurons cross to the opposite side (decussate) and travel to higher level of CNS  3rd order neurons situated in the thalamus and extends to sensory regions of the cortex
  55. 55. Spinal Cord Tracts Descending Tracts  Originate from the brain  Relay motor activity from the brain to the rest of the body  Two groups of fiber tracts  Corticospinal/pyramidal tracts : Motor tracts that descend without synaptic interruption from cerebrum to spinal cord; Originate primarily from motor cortex  Extrapyramidal tracts: Motor tract projections that carry autonomic motor impulses (i.e. for speech and swallowing); Originate in the midbrain and brain stem
  56. 56. Spinal Cord Tracts  Two groups of fiber tracts  Corticospinal/pyramid al tracts : Motor tracts that descend without synaptic interruption from cerebrum to spinal cord; Originate primarily from motor cortex  Extrapyramidal tracts: Motor tract projections that carry autonomic motor impulses (i.e. for speech and swallowing); Originate in the midbrain and brain stem
  57. 57. Cranial and Spinal Nerves CNS communicates with the body via nerves that exit the CNS from:  Brain (Cranial nerves)  Spinal cord (Spinal nerves) Cranial and Spinal nerves, and cell bodies outside the CNS make up the PNS
  58. 58. Cranial and Spinal Nerves Cranial Nerves  Count : 12 pairs  2 pairs arise from neuron cell bodies in the forebrain  10 pairs arise from the midbrain and hindbrain  Designated by Roman numerals, which reflect order of position (numbered from front to the back of brain)  Names indicate the structure innervated by these nerves (i.e. Facial)  Most cranial nerves are mixed nerves which indicates that the nerve contains both sensory and motor fibers
  59. 59. Cranial and Spinal Nerves Spinal Nerves  Count: 31 pairs  Groups:  8 cervical  12 thoracic  5 lumbar  5 sacral  1 coccygeal  All are mixed Nerves
  60. 60. Spinal Nerves Fibers are packaged together in the nerve and separate near the attachment of nerve to spinal cord Two “roots” to each nerve:  Dorsal root (sensory)  Ventral root (motor)
  61. 61. Reflex Arc Stimulation of sensory receptors evokes action potentials that are conducted into the spinal cord by sensory neurons A Sensory neuron synapses with an association neuron Association neuron synapses with a somatic motor neuron Somatic motor neuron then conducts impulses out of the spinal cord to the muscle and stimulates a reflex contraction
  62. 62. Textbook ReferenceHuman Physiology (6th edition) by Stuart Ira Fox

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