Anatomy and physiology of nervous system

Anatomy and physiology of nervous system

1. ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM PRESENTED BY: MISS. SHWETA SHARMA M.SC. NURSING 2 nd YEAR AIIMS JODHPUR

2. INTRODUCTION The nervous system is a highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. 01-09-2020 2

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6. Cells of the Nervous System 01-09-2020 6

7. The nervous system has approximately 10 million sensory neurons that send information about the internal and external environment to the brain and 500,000 motor neurons that control the muscles and glands. 01-09-2020 7

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11. Ganglia are ovoid structures containing cell bodies of neurons and glial cells supported by connective tissue. Ganglia function like relay stations - one nerve enters and an other exits. 01-09-2020 11

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15. ANATOMY OF THE BRAIN 01-09-2020 15

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17. The brain accounts for approximately 2% of the total body weight; it weighs approximately 1,400 g in an average young adult. In the elderly, the average brain weighs approximately 1,200 g. 01-09-2020 17

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20. Information transferred includes sensation, memory, and learned discrimination. Right-handed people and some left-handed people have cerebral dominance on the left side of the brain for verbal, linguistic, arithmetical, calculating, and analytic functions. The non-dominant hemisphere is responsible for geometric, spatial, visual pattern, and musical functions. 01-09-2020 20

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25. The basal ganglia are masses of nuclei located deep in the cerebral hemispheres. 01-09-2020 25

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28. The thalamus lies on either side of the third ventricle and acts primarily as a relay station for all sensation except smell. All memory, sensation, and pain impulses also pass through this section of the brain. 01-09-2020 28

29. The hypothalamus is located anterior and inferior to the thalamus. The hypothalamus lies immediately beneath and lateral to the lower portion of the wall of the third ventricle. 01-09-2020 29

30. It includes the optic chiasm (the point at which the two optic tracts cross) and the mamillary bodies (involved in olfactory reflexes and emotional response to odors). The infundibulum of the hypothalamus connects it to the posterior pituitary gland. 01-09-2020 30

31. Plays an important role in the endocrine system because it regulates the pituitary secretion of hormones that influence metabolism, reproduction, stress response, and urine production. 01-09-2020 31

32. Maintain fluid balance Maintains temperature regulation by promoting vasoconstriction or vasodilatation Site of the hunger center and is involved in appetite control 01-09-2020 32

33. Centers for regulating the sleep–wake cycle, blood pressure, aggressive and sexual behavior, and emotional responses (i.e., blushing, rage, depression, panic, and fear) Controls and regulates the autonomic nervous system 01-09-2020 33

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37. Nerve fibers from all portions of the cortex converge in each hemisphere and exit in the form of a tight bundle of nerve fibers known as the internal capsule. Having entered the pons and the medulla, each bundle crosses to the corresponding bundle from the opposite side. 01-09-2020 37

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40. The midbrain connects the pons and the cerebellum with the cerebral hemispheres; it contains sensory and motor pathways and serves as the center for auditory and visual reflexes. Cranial nerves III and IV originate in the midbrain. 01-09-2020 40

41. The pons is situated in front of the cerebellum between the midbrain and the medulla and is a bridge between the two halves of the cerebellum, and between the medulla and the cerebrum. Cranial nerves V to VIII connect to the brain in the pons. The pons contains motor and sensory pathways. Portions of the pons also control the heart, respiration, and blood pressure. 01-09-2020 41

42. The medulla oblongata contains motor fibers from the brain to the spinal cord and sensory fibers from the spinal cord to the brain. Most of these fibers cross, or decussate, at this level. Cranial nerves IX through XII connect to the brain in the medulla. 01-09-2020 42

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44. The cerebellum is separated from the cerebral hemispheres by a fold of dura mater, the tentorium cerebelli. The cerebellum has both excitatory and inhibitory actions and is largely responsible for coordination of movement . It also controls fine movement, balance, position sense (awareness of where each part of the body is), and integration of sensory input. 01-09-2020 44

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46. Structures protecting the brain The meninges (fibrous connective tissues that cover the brain and spinal cord) provide protection, support, and nourishment to the brain and spinal cord. 01-09-2020 46

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49. Dura mater It is the outermost layer and covers the brain and the spinal cord. It is tough, thick, inelastic, fibrous, and gray. There are four extensions of the dura: The falx cerebri, which separates the two hemispheres in a longitudinal plane. 01-09-2020 49

50. The tentorium, which is an infolding of the dura that forms a tough membranous shelf. The falx cerebelli, which is between the two lateral lobes of the cerebellum. The diaphragm sellae , which provides a “roof” for the sella turcica. 01-09-2020 50

51. 01-09-2020 51 When excess pressure occurs in the cranial cavity, brain tissue may be compressed against the tentorium or displaced downward, a process called herniation.

52. Arachnoid It is the middle membrane; an extremely thin, delicate membrane that closely resembles a spider web (hence the name arachnoid). It appears white because it has no blood supply. The arachnoid layer contains the choroid plexus , which is responsible for the production of cerebrospinal fluid (CSF). 01-09-2020 52

53. This membrane also has unique fingerlike projections, arachnoid villi, that absorb CSF. In the normal adult, approximately 500 mL of CSF is produced each day but 125 to 150 mL is absorbed by the villi. 01-09-2020 53

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55. When blood enters the system (from trauma or haemorrhagic stroke), the villi become obstructed and hydrocephalus (increased size of ventricles) may result. Pia mater —It is the innermost membrane; a thin, transparent layer that lies closely to brain and extends into every fold of the brain’s surface. 01-09-2020 55

56. Cerebrospinal fluid Clear and colorless fluid with a specific gravity of 1.007 01-09-2020 56

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58. The ventricular and subarachnoid system contains approximately 125 to 150 mL of fluid, while 15 to 25 mL of CSF is located in each lateral ventricle. The composition of CSF is similar to other extracellular fluids (such as blood plasma), but the concentrations of the various constituents are different. 01-09-2020 58

59. The analysis and laboratory report of CSF usually contains information on color, specific gravity, protein count, white blood cell count, glucose, and other electrolyte levels; it may also be tested for immunoglobulins or lactate. Normal CSF contains a minimal number of white blood cells and no red blood cells. 01-09-2020 59

60. Cerebral circulation The cerebral circulation receives approximately 15% of the cardiac output. The brain does not store nutrients and has a high metabolic demand that requires the high blood flow. 01-09-2020 60

61. In contrast to other organs that may tolerate decreases in blood flow because of their adequate collateral circulation, the brain lacks additional collateral blood flow, which may result in irreversible tissue damage when blood flow is occluded for even short periods of time. 01-09-2020 61

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64. 01-09-2020 64 Cerebral veins and sinuses are unique because, unlike other veins in the body, they do not have valves to prevent blood from flowing backward and depend on both gravity and blood pressure.

65. Blood–brain barrier The CNS is inaccessible to many substances that circulate in the blood plasma (e.g., dyes, medications, and antibiotics). After being injected into the blood, many substances cannot reach the neurons of the CNS because of the blood–brain barrier. This barrier is formed by the endothelial cells of the brain’s capillaries , which form continuous tight junctions, creating a barrier to macromolecules and many compounds. 01-09-2020 65

66. All substances entering the CSF must filter through the capillary endothelial cells and astrocytes. Often altered by trauma, cerebral oedema , and cerebral hypoxemia, the blood–brain barrier has implications in the treatment and selection of medication for CNS disorders as well as serving a protective function. 01-09-2020 66

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68. Brain waves are rhythmic fluctuation of electric potential between parts of the brain as seen on an electroencephalogram (EEG). To measure brain waves electrodes are placed onto the scalp using the EEG. 01-09-2020 68

69. Anatomy of the spinal cord Approximately 45 cm (18 in) long and about the thickness of a finger, it extends from the foramen magnum at the base of the skull to the lower border of the first lumbar vertebra, where it tapers to a fibrous band called the conus medullaris. 01-09-2020 69

70. Continuing below the second lumbar space are the nerve roots that extend beyond the conus, which are called the cauda equina because they resemble a horse’s tail. Similar to the brain, the spinal cord consists of gray and white matter. 01-09-2020 70

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74. Vertebral Column 01-09-2020 74

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76. 01-09-2020 76 The vertebrae are separated by disks, except for the first and second cervical, the sacral, and the coccygeal vertebrae.

77. THE PERIPHERAL NERVOUS SYSTEM The peripheral nervous system includes the cranial nerves, the spinal nerves, and the autonomic nervous system. 01-09-2020 77

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79. Three are entirely sensory (I, II, VIII), five are motor (III, IV, VI, XI, and XII), and four are mixed (V, VII, IX, and X) as they have both sensory and motor functions. 01-09-2020 79

80. SPINAL NERVES 01-09-2020 80

81. AUTONOMIC NERVOUS SYSTEM The autonomic nervous system regulates the activities of internal organs such as the heart, lungs, blood vessels, digestive organs, and glands. Maintenance and restoration of internal homeostasis is largely the responsibility of the autonomic nervous system. 01-09-2020 81

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83. Sympathetic stimuli are mediated by nor-epinephrine and parasympathetic impulses are mediated by acetylcholine . Sympathetic neurons are located in the thoracic and the lumbar segments of the spinal cord; their axons, or the pre-ganglionic fibers, emerge by way of anterior nerve roots from the eighth cervical or first thoracic segment to the second or third lumbar segment. 01-09-2020 83

84. Sympathetic Syndromes Dilation of the pupil of the eye on the same side as a penetrating wound of the neck (evidence of disturbance of the cervical sympathetic cord ) Temporary paralysis of the bowel (indicated by the absence of peristaltic waves and the distention of the intestine by gas) after fracture of any one of the lower dorsal or upper lumbar vertebrae with hemorrhage into the base of the mesentery Marked variations in pulse rate and rhythm that often follow compression fractures of the upper six thoracic vertebrae. 01-09-2020 84

85. MOTOR SYSTEM FUNCTION 01-09-2020 85 Cortical homunculus

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88. Coordination of Movement. The smoothness, accuracy, and strength that characterize the muscular movements of a normal person are attributable to the influence of the cerebellum and the basal ganglia. 01-09-2020 88

89. SENSORY SYSTEM FUNCTION Integrating Sensory Impulses The thalamus integrates all sensory impulses except olfaction. It plays a role in the conscious awareness of pain and the recognition of variation in temperature and touch. The thalamus is responsible for the sense of movement and position and the ability to recognize the size, shape, and quality of objects. 01-09-2020 89

90. Receiving Sensory Impulses Afferent impulses travel from their points of origin to their destinations in the cerebral cortex via the ascending pathways directly, or they may cross at the level of the spinal cord or in the medulla, depending on the type of sensation that is registered. Sensory information may be integrated at the level of the spinal cord or may be relayed to the brain. 01-09-2020 90

91. Sensory Losses Destruction of a sensory nerve results in total loss of sensation in its area of distribution. Transection of the spinal cord yields complete anesthesia below the level of injury. Selective destruction or degeneration of the posterior columns of the spinal cord is responsible for a loss of position and vibratory sense in segments distal to the lesion, without loss of touch, pain, or temperature perception. 01-09-2020 91

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93. CONCLUSION As discussed throughout the presentation, learning about anatomy and physiology of brain and spinal cord will help nurses to understand the functioning of nervous system and various neurological disorders. Nurses can do neurological assessment of patients, observe the sign and symptoms, provide the necessary nursing care, prevent any complications and support the patient psychologically. 01-09-2020 93

94. REFERENCES 1.Janice L. Hinkle, Kerry H. Cheever. Brunner and Suddarth’s Textbook of Medical Surgical Nursing. 2015. New Delhi. Wolters Kluwer.13th Edition. Volume 1. Pg. no.1821-1834. 2.Lewis. Medical Surgical Nursing Assessment and Management of clinical problems.2015. New Delhi. Elsevier. 2nd Edition. Volume II. Pg. no.1391-1400. 3.Joyce M. Black, Jane Hokanson Hawks. Medical Surgical Nursing Clinical Management of Positive Outcomes.2015. New Delhi. Reed Elsevier India Private Limited. Volume II. Pg. No. 1330-1331. 4.B D Chaurasia . HUMAN ANATOMY Regional and applied dissection and clinical. 2010. New Delhi. CBS Publishers. 5th edition. Volume 3. Pg. no. 315-449. 01-09-2020 94

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