Central Nervous System

1. Central Nervous System Brain and Cranial Nerves

2. Brain • 20 billion neurons • Carries out the most complex functions • Contains 98% of the neurons in the body • Weight of the brain is on average 3 lbs • About 1200cc in size • NO correlation between brain size and intelligence

3. Brain Regions

4. Cerebrum • Two large hemispheres divided by the longitudinal fissure • Important functions: • Thought processes • Memory storage and retrieval • Intellectual function • Complex motor patterns

5. Diencephalon • Deep portion of the brain attached to the cerebrum • Three major regions • 1. Epithalamus – pineal gland-secretes melatonin (regulation of the “body clock”) • 2. Thalamus – sensory information relay and processing • 3. Hypothalamus – visceral control center. Involved in emotions, autonomic function and hormone production

6. Mesencephalon(Midbrain) • Part of the brain stem • Important functions: • 1. Processing of visual and auditory information • 2. Generation of involuntary somatic motor responses • 3. Maintenance of consciousness

7. Pons • Inferior to mesencephalon • Somatic motor and visceral control • Relay of sensory information to thalamus and cerebellum • Connects cerebellum to brain stem

8. Cerebellum • Two small hemispheres • Posterior to pons • Function of cerebellum is to automatically adjust motor activities based on sensory information and memories of past learned patterns of movement

9. Medulla Oblongata • Connection of brain to spinal cord • Functions of the medulla are: • 1. Relay sensory information to thalamus and other brain regions • 2. Centers concerned with autonomic regulation of heart rate, blood pressure, and digestive activities

10. Gray matter and White matter • Outer layer of superficial gray matter • Neural cortex • Neuron cell bodies • Internal white matter • Myelinated connections • Isolated areas of gray matter called NUCLEI

11. Ventricles of the brain • Fluid filled cavities of the brain • Filled with cerebral spinal fluid (CSF) • Two lateral ventricles separated by the septum pellucidum • Third ventricle in the diencephalon • Cerebral aqueduct (Aqueduct of midbrain) • Fourth ventricle

12. Ventricles of the brain

14. Ventricles (coronal section)

15. Cranial Meninges • Membranes that surround the brain • Help protect the brain from the surrounding bone • Three cranial meninges • Dura – tough outer layer • Arachnoid – middle layer • Pia – inner layer that adheres to the surface of the brain

16. Meninges

17. Special regions of dura mater • Falx cerebri • Transverse fissure • Tentorium cerebelli • Falx cerebelli

18. Cerebrospinal fluid • Fills the ventricles of the brain • Cushions the neural tissue • Supports the brain • Transports nutrients, chemical messages, and waste products

19. Production of CSF • Choroid plexus • Floor of lateral ventricles • Roof of third ventricle • Roof of 4th ventricle • 500ml/day produced • Total volume 150ml

21. Cerebrum • Largest region of the brain • Paired cerebral hemispheres • Processing of sensory and motor information • Cerebral neurons exert direct and indirect control over somatic motor neurons

22. Cerebral Hemispheres • Outer layer of neural cortex – gray matter • Longitudinal fissure separates hemispheres • Elevated ridges – gyri • Shallow depressions are called sulci • Deeper grooves are fissures

23. Cerebral lobes • 1. Frontal – primary motor cortex • 2. Parietal – primary sensory cortex • 3. Occipital – visual cortex • 4. Temporal – auditory and olfactory cortex • 5. Insula – control of visceral functions, integration of autonomic information

24. Cerebral lobes

25. Cerebral cortex

26. Primary Motor Cortex • Cerebral cortex anterior of the central sulcus • Precentral gyrus • Neurons of this region direct the voluntary movement of skeletal muscles • These neurons are called pyramidal cells • Pyramidal system provides voluntary motor control • Amyotrophic lateral sclerosis (ALS)

27. Primary Sensory Cortex • Cortex posterior to central sulcus • Postcentral gyrus of parietal lobe • Neurons receive information on touch, pressure, pain, taste, and temperature • Occipital lobe is primary visual cortex • Temporal lobe receives information dealing with hearing and smelling • Insula receives sensory information dealing with taste

28. Association areas • Regions of the cortex connected to the primary sensory and motor regions of the brain • INTEGRATION regions • Plan, prepare, coordinate motor output based sensory input from others areas of the cerebral cortex

29. Integrative Centers • Receive and process information from many different association areas • Direct complex motor activities and perform complicated analytical functions • PRE-FRONTAL CORTEX • Integrates information from sensory association areas • Performs abstract intellectual functions

30. White Matter • Covered by the gray matter • Myelinated fibers that connect various regions of the brain together • Association fibers – interconnect areas of neural cortex within the same hemisphere • Commissural fibers – fiber tracts that connect the two cerebral hemispheres • Projection fibers – tracts that link the cerebrum with other regions of the brain and spinal cord

32. Diencephalon • Thalamus – switching and relay center for sensory and motor information • Information filter • Hypothalamus – emotions and visceral processes • Autonomic functions

34. Limbic System • Nuclei (neuron cell bodies) and tracts (white fibers) that border the cerebrum and diencephalon • Functions: • Emotional states and related behavior • Links conscious intellectual functions of brain to unconscious and autonomic functions of the brain • Memory storage and retrival

35. Limbic System

36. Mesencephalon(Midbrain) • Nuclei that process visual and auditory information • Corpora quadrigemina consists of the: • Superior colliculus – visual inputs • Inferior colliculus – auditory data

37. Pons • Origin of cranial nerves V, VI, VII, and VIII • Involuntary control of respiration • Relay and processing center for cerebellar commands

38. Cerebellum • Two hemispheres each with 2 lobes • Internal white matter is called the arbor vitae (tree of life) • Cerebellum is responsible for: • Maintenance of balance and equilibrium • Fine-tuning voluntary and involuntary movements

39. Cerebellum

40. Medulla Oblongata • Connection of brain and spinal cord • Medulla functions: • Relay station along sensory and motor pathways • Origin of cranial nerves VIII, IX, X, XI, and XII • Autonomic functions related to heart rate, contraction strength of heart, blood flow, pace of respiratory movements

41. Cranial Nerves (PNS)

42. Cranial Nerves • Components of the PNS • Twelve pairs of cranial nerves connected to the brain • Numbered I through XII • Have either motor, sensory or mixed functions

43. I Olfactory II Optic III Oculomotor IV Trochlear V Trigeminal VI Abducens VII Facial VIII Vestibulocochlear IX Glossopharyngeal X Vagus XI Spinal Accessory XII Hypoglossal Sensory Sensory Motor Motor Mixed Motor Mixed Sensory Mixed Mixed Motor Motor Cranial Nerves