1. O NS O rganization of the Nervous System Joselito B. Diaz, MD, FPNA College of Rehabilitation Sciences

2. Introduction The Nervous and Endocrine systems together control and coordinate functions of all body systems –Coordinated as an interlocking system termed the Neuroendocrine system –Nervous system performs short term crisis management –Endocrine system regulates long term ongoing metabolic activities

3. Nervous System CORRELATION COORDINATION MEMORY SENSORY STIMULI AfferentEfferent MUSCLES GLANDS Etc.

4. Overview of Neural Integration

6. Functional Organization of the Nervous System

7. Anatomical Organization of the Nervous System

8. Terminologies

9. Nervous Tissue Specialized tissue for rapid conduction of electrical impulses that convey information from one part of the body to another –98% nervous tissue concentrated in brain and spinal cord Neurons = functional units transmit information in the form of electrical current at their cell membranes Neuroglia = “nerve glue” provide physical support for neurons represent 90% of a cells in brain Nerve Cells and Astrocyte (SEM x2,250). Nervous tissue contains two basic cell types

10. The neuron is the functional unit of the nervous system DendritesDendrites receive information from another cell or receptor and transmit the message to the cell body The cell body contains the nucleus, mitochondria and other organelles typical of eukaryotic cellscell body The axon conducts messages away from the cell bodyaxon

13. Central nervous system Consists of the brain located within the skull and the spinal cord located within the vertebral foramen Integration and command center of the body Covered by meninges and surrounded by cerebrospinal fluid

14. Central nervous system BRAIN Forebrain –Cerebrum –Diencephalon Midbrain Hindbrain –Pons –Medulla –Cerebellum SPINAL CORD Cervical segments Thoracic segments Lumbar segments Sacral segments Coccygeal segments

15. Central nervous system

16. Meninges and CSF The meninges are 3 connective tissue membranes that lie external to the brain and the spinal cord –Dura mater, arachnoid mater, pia mater –Cover and protect the CNS –Hold cerebrospinal fluid (CSF) –Prevents harmful substances from entering CSF

17. Meninges and CSF The CSF is the extracellular fluid found in the ventricles of the brain and subarachnoid space –Surrounds the brain and spinal cord in the subarachnoid space –Cushions and protects the CNS from trauma –Provides mechanical buoyancy and support the brain –Nourishes the CNS and removes metabolites

18. Meninges

22. Central nervous system - Brain

23. Brain

24. Fissures and gyri

25. Surface contains gyri and sulci or fissures Longitudinal fissure separates two cerebral hemispheres Central sulcus of Rolando separates the frontal and parietal lobes Lateral Sylvian fissure separates the temporal lobe from the frontal and parietal lobes Line drawn from the parieto-occipital sulcus down to the preoccipital notch delineate the occipital lobe from the temporal and parietal lobes The cerebral cortex

26. Lobes of the cerebrum

29. The Cerebral Hemispheres PLAY

30. White and gray matter

31. White Matter of the Cerebrum Association fibers –connections from gyrus to gyrus and from lobe to lobe in the same hemisphere –Superior longitudinal fasciculus Commissural fibers –Connections occur between homologous areas of the two hemisperes –Corpus callosum Projection fibers –Connects the cerebral cortex to the subcortical, brainstem and spinal cord nuclei

32. Subcortical nuclei

33. Diencephalon and Brainstem

34. Composed of: Epithalamus Hypothalamus Subthalamus Thalamus Diencephalon

35. Thalamus Final relay point for ascending sensory information Coordinates the activities of the cerebral cortex, basal nuclei and cerebellum

36. Hypothalamus Controls somatic motor activities at the subconscious level Controls autonomic function Coordinates activities of the endocrine and nervous systems Secretes hormones Produces emotions and behavioral drives Coordinates voluntary and autonomic functions Regulates body temperature Coordinates circadian cycles of activity

37. The Hypothalamus in Sagittal Section

38. Medulla Connects the brain with the spinal cord Contains relay stations reflex centers and cranial nerve nuclei –Olivary nuclei –Cardiovascular and respiratory rhythmicity centers Reticular formation begins in the medulla oblongata and extends into more superior portions of the brainstem

39. Brainstem - Medulla

40. Pons Sensory and motor nuclei for four cranial nerves Nuclei that help control respiration Nuclei and tracts linking the cerebellum with the brain stem, cerebrum and spinal cord Ascending, descending and transverse tracts

41. Brainstem - Pons

42. Midbrain The tectum (roof) contains the corpora quadrigemina – Superior and inferior colliculi The mesencephalon contains many nuclei and tracts –Red nucleus –Substantia nigra –Cerebral peduncles –RAS headquarters

43. Brainstem - Midbrain

44. Adjusts postural muscles and tunes on-going movements Cerebellar divisions –Flocculonodular, anterior and posterior lobes –Vermis and cerebellar hemispheres Superior, middle and inferior cerebellar peduncles link cerebellum with brain stem, diencephalon, cerebrum, and spinal cord Cerebellum

45. The Cerebellum

47. Cranial Nerves 12 pairs of cranial nerves –Each attaches to the ventrolateral surface of the brainstem near the associated sensory or motor nuclei

48. PLAY Cranial Nerves

49. PLAY Cranial Nerves

50. Spinal cord The adult spinal cord ends between L 1 and L 2 Locate the: –Shallow posterior median sulcus –Deep anterior median fissure

51. Spinal cord Enlargements are composed of numerous gray matter dealing with sensory and motor control of the limbs Cervical enlargement - nerves to the shoulder girdles and upper limbs Lumbar enlargement – innervations to the pelvis and lower limbs Conus medularis is the end of the spinal cord

52. Spinal cord is divided into 31 segments Dorsal root ganglia – contain the cell bodies of sensory neurons Dorsal root – composed of sensory axons which bring sensory information into the spinal cord Ventral roots – axons of motor neurons; control somatic and visceral effectors Sensory and motor roots are bound together into a single spinal nerve (distal to the root ganglion) Spinal nerves are mixed nerves – contain both afferent (sensory) and efferent (motor) fibers Spinal cord

53. Gross Anatomy of the Adult Spinal Cord

54. Spinal meninges Membranes surround and protect the spinal cord Provide physical stability and shock absorption Blood vessels branching within these layers deliver oxygen and nutrients to the spinal cord Three layers: –Dura mater –Arachnoid –Pia mater

55. The Spinal Cord and Spinal Meninges

56. Sectional anatomy of the spinal cord White matter is composed of myelinated and unmyelinated axons Gray matter dominated by nerve cell bodies and neuroglia Gray matter surrounds the central canal Projections of gray matter called horns

57. The Sectional Organization of the Spinal Cord

59. Sectional anatomy of the spinal cord Organization of Gray Matter –Organized into function groups called nuclei –Posterior horns are sensory Posterior gray horn contains somatic and visceral sensory nuclei –Anterior horns are motor Anterior gray horns deal with somatic motor control Lateral gray horns contain visceral motor neurons –Gray commissures join the lateral sides together; axons pass from one side of the spinal cord to the other through the gray commissure

60. Sectional anatomy of the spinal cord Organization of White Matter –Divided into six columns (funiculi) containing tracts –All axons within a tract relay the same type of information (sensory or motor) in the same direction –Ascending tracts relay information from the spinal cord to the brain –Descending tracts carry information from the brain to the spinal cord Ascending pathways Descending pathways

61. Peripheral Nervous System The PNS consists of 12 pairs of cranial nerves originate from the brain and 31 pairs of nerves are attached to the spinal cord Sensory (afferent) –all axons carry impulses from sensory receptors via the PNS to the CNS Motor (efferent) –all axons carry impulses via the PNS from CNS Mixed –a mixture of sensory and motor neurons that carry impulses via the PNS to and from CNS – most common type of nerve in the body

62. Functional Organization of the Nervous System

63. Sensory division - made of afferent neurons somatic –sensory neurons send information from skin, skeletal muscles, and joints visceral –sensory neurons send information from organs within the abdominal and thoracic cavities Sensory Division of the PNS

64. Motor Division of the PNS Motor division made of efferent neurons control the action of muscles and glands –somatic motor neurons send APs to voluntary skeletal muscle –visceral motor neurons send APs to involuntary cardiac muscle, smooth muscle and glands –a.k.a. the Autonomic Nervous System (ANS) –2 antagonistic (opposing) divisions Sympathetic Parasympathetic –the two divisions control the same effectors but create opposite responses in the effectors

65. 31 pairs of spinal nerves Nerve sheath consists of: –Epineurium –Perineurium –Endoneurium

66. Dorsal ramus (sensory and motor innervation to the skin and muscles of the back) Ventral ramus (supplying ventrolateral body surface, body wall and limbs) Rami communicantes –White ramus (myelinated axons) –Gray ramus (unmyelinated axons that innervate glands and smooth muscle) Each pair of nerves monitors one dermatome Spinal nerves

67. Peripheral Distribution of Spinal Sensory Nerves

68. Peripheral Distribution of Spinal Motor Nerves

69. Dermatomes

70. Complex interwoven network of nerves Four large plexuses –Cervical plexus –Brachial plexus –Lumbar plexus –Sacral plexus Nerve plexus

71. The Cervical Plexus

72. The Brachial Plexus

74. The Lumbar and Sacral Plexuses

76. Peripheral Nerves and Nerve Plexus

77. Coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions Two divisions: –Sympathetic division (thoracolumbar, “fight or flight”) Preganglionic fibers leaving the thoracic and lumbar segments –Parasympathetic division (craniosacral, “rest and repose”) Preganglionic fibers leaving the brain and sacral segments Autonomic Nervous System

78. Preganglionic neurons between segments T1 and L2 Ganglionic neurons in ganglia near vertebral column –Sympathetic chain ganglia (paravertebral ganglia) –Collateral ganglia (prevertebral ganglia) Specialized neurons in adrenal glands Sympathetic division anatomy

79. Organization of the Sympathetic Division of the ANS

80. Organization of the Sympathetic Division

81. Preganglionic neurons in the brainstem and sacral segments of spinal cord –Preganglionic fibers leave the brain as cranial nerves III, VII, IX, X –Sacral neurons form the pelvic nerves Ganglionic neurons in peripheral ganglia located within or near target organs Parasympathetic division

82. Organization of the Parasympathetic Division of the ANS

83. Organization of the Parasympathetic Division

84. Organization of the Nervous System Joselito B. Diaz, MD, FPNA College of Rehabilitation Sciences