1. Chapter 13 The Central Nervous System
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2. Chapter 13: The Central Nervous System
The Central Nervous System (CNS) is the major control center for the body
In about 3 pounds of tissue, the CNS has 100 billion neurons
The brain collects sensory information, evaluates it, and sends instructions to effectors to direct appropriate responses
The spinal cord serves two major roles
Serves as a pathway for information to and from the brain
It controls rapid reactions (reflexes) to specific stimuli
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3. CNS Overview: The Main Parts of the CNS
The CNS consists of
The brain
Cerebrum
Diencephelon
Brainstem
Cerebellum
The spinal cord
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4. CNS Overview: The Main Parts of the CNS
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5. CNS Overview: The Main Parts of the CNS
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6. CNS Overview: Protection of the CNS
The CNS is protected by
Bone
Cranial bones protect the brain
Vertebrae protect the spinal cord
Three meninges (layers of connective tissue surrounding the CNS)
Cerebrospinal fluid (CSF) - the CNS is cushioned by a thin layer of fluid
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7. CNS Overview: Protection of the CNS
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8. CNS Overview: Protection of the CNS
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9. CNS Overview: The Meninges and the Brain
The meninges are three connective tissue layers that surround the brain and spinal cord
Dura mater
Epidural space
Dural sinuses
Arachnoid mater
Subarachnoid space
Pia mater
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10. CNS Overview: The Meninges and the Brain
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11. CNS Overview: The Meninges and the Brain
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12. CNS Overview: Meninges and the Spinal Cord
The meninges also surround the spinal cord, and the cranial and spinal meniniges form a single unified protective covering for the CNS.
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13. CNS Overview: Meninges and the Spinal Cord
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14. CNS Overview: Blood Flow to the Brain
Blood supply to the brain is a crucial source of O2 and nutrients
The brain receives much greater blood supply than expected based on its size and mass
Blood flow to active areas of the brain increases during higher levels of metabolic activity
Interruptions in blood flow have very serious consequences (unconsciousness, stroke, death)
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15. CNS Overview: Blood Flow to the Brain
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16. CNS Overview: Blood Flow to the Brain
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17. CNS Overview: Blood Flow to the Brain
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18. CNS Overview: The Blood-Brain Barrier
The blood-brain barrier (BBB) prevents pathogens and harmful chemicals from entering the brain
The BBB consists of 3 components
Tight junctions between capillary endothelial cells
A thick basement membrane underlying the endothelium
A layer of astrocytes that cover the capillaries
The BBB helps prevent polar chemicals from entering the brain (but small, nonpolar chemicals enter easily)
Damage to the BBB exposes the brain to changes in blood chemistry and to pathogens
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19. CNS Overview: Cerebrospinal Fluid
Cerebrospinal fluid (CSF) is a nutrient-rich fluid that circulates within and around the CNS
CSF serves three key homeostatic functions in the CNS
Mechanical protection
Chemical protection
Circulation
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20. CNS Overview: Cerebrospinal Fluid
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21. CNS Overview: Cerebrospinal Fluid
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22. CNS Overview: Production of CSF
CSF is produced in each ventricle
Ependymal cells control which chemicals pass into CSF
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23. CNS Overview: Circulation Pattern of CSF
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24. CNS Overview: Circulation Pattern of CSF
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25. The Cerebrum: Introduction
The cerebrum is by far the largest part of the brain
All conscious activities of the brain occur in the cerebrum - this involves massive amounts of neural processing
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26. The Cerebrum: Introduction
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27. The Cerebrum: Terminology
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28. The Cerebrum: Terminology
Key structural terms
Gyrus
Sulcus
Sissure
Cerebral cortex
Gray and white matter
Cerebral hemispheres
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29. The Cerebrum: Lobes of the Cerebrum
Each cerebral hemisphere has several regions known as lobes:
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
The insula (deep to temporal lobe)
Major grooves in cerebral surface
Central sulcus
Lateral sulcus
Parieto-occipital sulcus
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30. The Cerebrum: Lobes of the Cerebrum
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31. The Cerebrum: Lobes of the Cerebrum
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32. The Cerebrum: Cerebral White Matter
Most of the cerebral white matter consists of fiber tracts - major groups of axons connecting distant regions of cerebral neurons
Association tracts connect gyri in the same hemisphere
Commissural tracts connect areas in opposite hemispheres
Corpus callosum
Projection tracts connect the cerebrum to other brain regions
Internal capsule
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33. The Cerebrum: Cerebral White Matter
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34. The Cerebrum: Basal Nuclei
Deep within the cerebrum are areas of gray matter called basal nuclei
Major basal nuclei include
Globus pallidus
Putamen
Caudate nucleus
Basal nuclei are involved in the coordination of motor output, learning and many other functions
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35. The Cerebrum: Basal Nuclei
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36. The Cerebrum: Basal Nuclei
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37. The Cerebrum: The Limbic System
This ring-like set of structures (aka the “emotional brain”) lies along the border of the cerebrum and diencephelon
The limbic system mediates behaviors and emotions
Pleasure and pain
Fear/rage
Affection
The limbic system also has a major role in memory
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38. The Cerebrum: The Limbic System
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39. Functional Areas of the Cerebral Cortex
Regions of the cerebral cortex specialize in different types of information processing
Sensory areas receive and process sensory impulses
Motor areas initiate voluntary movements
Association areas perform integrative functions
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40. Functional Areas of the Cerebral Cortex
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41. Sensory Areas of the Cerebral Cortex
Major sensory regions of the cerebral cortex include
Primary somatosensory area
Primary visual area
Primary auditory area
Primary gustatory area
Primary olfactory area
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42. Sensory Areas of the Cerebral Cortex
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43. Motor Areas of the Cerebral Cortex
Major motor regions of the cerebral cortex include
Primary motor area
Broca’s area
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44. Motor Areas of the Cerebral Cortex
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45. Integrative Areas of the Cerebral Cortex
Major integrative regions of the cerebral cortex include
Somatosensory association area
Prefrontal cortex
Visual association area
Wernicke’s area
Common integrative area
Premotor area
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46. Integrative Areas of the Cerebral Cortex
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47. Hemispheric Lateralization of the Cerebral Cortex
There is functional asymmetry between the two cerebral hemispheres
Sensory information passes to the opposite side on its way in
Signals to voluntary muscles pass to the opposite side on their way out
Many integrative functions are localized in one of the hemispheres, leading to terms such as “left brain” and “right brain” functions
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48. Hemispheric Lateralization of the Cerebral Cortex
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49. Copyright 2010, John Wiley & Sons, Inc.
Diencephelon
The diencephelon is a small but crucial brain region that sits below and is surrounded by the cerebrum
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Diencephelon
Thalamus: Relays almost all sensory input to the cerebral cortex. Contributes to motor functions by transmitting information from the cerebellum and basal ganglia to the primary motor area of the cerebral cortex. Also plays a role in the maintenance of consciousness.
Hypothalamus: Controls and integrates activities of the autonomic nervous system and pituitary gland. Regulates emotional and behavioral patterns. Controls body temperature and regulates eating and drinking behavior. Helps maintain the waking state and establishes patterns of sleep. Produces hormones.
Pineal gland: Secretes melatonin, sets the body’s biological clock.
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51. Diencephelon: The Thalamus
The thalamus has paired masses of gray matter, organized into many nuclei, located on either side of the third ventricle
The thalamus is a major relay center for information entering and leaving the brain, as well as for information moving within the brain
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52. Diencephelon: The Thalamus
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53. Diencephelon: The Thalamus
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54. Diencephelon: The Hypothalamus
The hypothalamus is a small but critical brain region
Specific nuclei are involved in the control of
Production of hormones
Emotions and behavior
Eating and drinking
Body temperature
Circadian rhythms and consciousness
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55. Diencephelon: The Hypothalamus
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56. Diencephelon: The Pineal Gland
This small region of the diencephelon secretes the hormone melatonin, and is involved in regulation of circadian rhythms and sleep
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57. Diencephelon: The Pineal Gland
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58. Copyright 2010, John Wiley & Sons, Inc.
Brainstem
Brainstem fiber tracts connect the spinal cord, the diencephelon, and the cerebellum to each other
Brainstem nuclei control many critical autonomic body functions
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Brainstem
Midbrain: Relays motor impulses from the cerebral cortex to the pons and sensory impulses from the spinal cord to the thalamus. Superior colliculi coordinate movements of the head, eyes, and trunk in response to visual stimuli, and the inferior colliculi coordinate movements of the head, eyes, and trunk in response to auditory stimuli. Contributes to control of movements.
Pons: Relays impulses between cerebral cortex and cerebellum and between the medulla and midbrain. Pneumotaxic and apneustic area, together with the medulla oblongata, help control breathing.
Medulla oblongata: Relays motor and sensory impulses between other parts of the brain and the spinal cord. Vital centers regulate heartbeat, breathing (together with pneumotaxic and apneustic area of pons), and blood vessel diameter. Other centers coordinate swallowing, vomiting, coughing, sneezing, and hiccuping.
Reticular formation: Helps maintain consciousness, causes awakening from sleep, filters repetitive sensory input, and contributes to regulation of muscle tone.
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Brainstem: Midbrain
Major midbrain structures include the cerebral peducles, the corpora quadrigemina, and the cerebral aqueduct
The midbrain includes major fiber tracts, as well as nuclei involved in responses to visual and auditory stimuli
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Brainstem: Midbrain
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62. Copyright 2010, John Wiley & Sons, Inc.
Brainstem: Midbrain
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63. Copyright 2010, John Wiley & Sons, Inc.
Brainstem: Midbrain
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64. Copyright 2010, John Wiley & Sons, Inc.
Brainstem: Pons
Major pons fiber tracts connect the cerebral cortex to the cerebellum
The pneumotaxic and apneustic areas help regulate breathing
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Brainstem: Pons
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Brainstem: Pons
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67. Brainstem - Medulla Oblongata
Large fiber tracts in the medulla connect the spinal cord to the brain
The medulla includes control centers for respiration, heart rate, blood pressure, and other functions (e.g., coughing, vomiting, etc.)
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68. Brainstem - Medulla Oblongata
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69. Brainstem - Medulla Oblongata
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70. Brainstem: Reticular Formation
The reticular formation is a diffuse collection of small nuclei in the brainstem - they act together to help maintain consciousness, and to regulate muscle tone
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71. Brainstem: Reticular Formation
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72. Copyright 2010, John Wiley & Sons, Inc.
The Cerebellum
The cerebellum is 10% of brain mass but contains almost 50% of all brain neurons
The cerebellum is critical to coordinated movements, and provides constant feedback to motor areas
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The Cerebellum
Compares intended movements with what is actually happening to smooth and coordinate complex, skilled movements. Regulates posture and balance. May have a role in cognition and language processing.
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74. The Cerebellum: Internal Structures
Major structures and regions of the cerebellum are
Cerebellar hemispheres
Vermis
Arbor vitae
Cerebellar peduncles
Vitae
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75. The Cerebellum: Internal Structures
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76. The Cerebellum: Internal Structures
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77. Copyright 2010, John Wiley & Sons, Inc.
The Spinal Cord
The spinal cord is the pathway taken by information traveling between our brains and our bodies
The spinal cord includes interneurons mediating spinal reflexes, as well as the cell bodies of all somatic motor neurons
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78. Copyright 2010, John Wiley & Sons, Inc.
The Spinal Cord
Conducts sensory nerve impulses toward the brain and motor nerve impulses from the brain toward skeletal muscles and other effector tissues. Integrates spinal reflexes.
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79. The Spinal Cord: Gross Anatomy
The spinal cord has several distinctive features
Cervical enlargement
Lumbar enlargement
Conus medullaris
Filum terminale
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80. The Spinal Cord: Gross Anatomy
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81. The Spinal Cord: Spinal Nerves
The spinal cord gives rise to the spinal nerves
Anterior root
Posterior root
Posterior root ganglion
Spinal nerve
The most inferior of the spinal nerves form the
Cauda equina
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82. The Spinal Cord: Internal Structure
The spinal gray matter has a distinctive pattern
Anterior gray horns
Lateral gray horns
Posterior gray horns
Gray commissure
Central canal
The spinal white matter has 3 sets of columns
Anterior columns
Lateral columns
Posterior columns
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83. The Spinal Cord: Internal Structure
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84. The Spinal Cord: Sensory and Motor Tracts
The spinal cord has a number of well understood fiber tracts and columns, that are named according to their origins and destinations.
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85. The Spinal Cord: Sensory and Motor Tracts
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86. Somatic Sensory and Motor Pathways Interactions Animations
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End of Chapter 13
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