NERVOUS SYSTEM

1. NERVOUS SYSTEM RITA CAREY-NITA

2. Anatomy & Physiology Nervous system is the major communicating system in the body. 2 Divisions: • Central Nervous System: Brain & Spinal Cord • Peripheral Nervous System: Spinal & Cranial nerves as well as nerves from the Autonomic Nervous System

4. Nerve Cells Neuron Neuroglia: • Oligodendrocytes • Microglial • Astrocytes • Ependymal

5. Neuron • Most important for transmission of information • Vary in shape & size • Three parts: • Dendrite: tree like projections receives information from other neurons & sends impulse to body • Body: contains nucleus • Axon: long extension that transmits information away from the cell body which branch off to axon terminals

6. Neuroglia Cells • Astrocytes: form protective barrier around neuron blocking toxins in blood from entering the CNS • Ependymal: line inside cavity of brain & assist with formation of CSF • Microglia: participates in phagocytosis of pathogens • Oligodendrocytes: form CNS myelin sheath

7. Neurons • Sensory neuron: • carries information from the periphery to CNS • AKA afferent neuron • Found in CNS & PNS • Motor neuron: • carries information from the CNS to the periphery • AKA efferent neuron • Found in CNS & PNS • Interneuron: • form connections between sensory & motor neurons • Only located in the CNS • Play role in thinking, learning & memory

8. Synapse • Synapse is a junction or space between two neurons which information is transmitted across • Process: • The impulse travels along first neuron to its end at the axon terminal • Neurotransmitters diffuse across the synapse & binds with the receptor site on the dendrite of the next neuron (new neuron now stimulated) • Once the neurotransmitter has stimulated the neuron it is terminated by inactivator substance (acetylcholinesterase) on the dendrite

9. Nerve Impulse • Polarization: • resting state of the neuron; cell quiet & resting • inside of neuron is negative charge & outside is positive • No nerve impulse is transmitted • More K inside & negative ions & more Na outside • Depolarization: • Neuron is stimulated • Rush of Na ions into cell • Change inside cell to positive charge • Repolarization: • K is pumped into cell & Na is pumped outside • Quick change inside cell back to negative charge • Need to repolarize in order to be stimulated again

10. Nerves Nerves are a group of axons, dendrites or both with blood vessels & wrapped with a connective tissue. • Nerves from PNS are mixed nerves • Cranial nerves that originate in the brain can be sensory, motor or mixed • Autonomic nerves are motor

11. Spinal Cord Spinal Cord: • Located in the vertebral column • Extends from foramen magnum to L1-L2 • Considered part of CNS • Transmits impulses to & from the brain • Integrating center for spinal cord reflexes • Spinal nerves emerge from intervertebral foramina • Cross-section is butterfly shaped gray matter surrounded by white matter • Ascending tracts & Descending tracts • Central canal is continuation of ventricles in brain & contains CSF

12. Spinal Nerves Spinal Nerves: • 31 pairs • 8 cervical—12thoracic—5 lumbar—5 sacral— 1 coccygeal • All mixed nerves • Form plexuses • Dorsal route contains sensory neurons that carry impulses to SC • Ventral route contains motor neurons that carry impulses from SC to muscles or glands

13. Spinal Cord Reflex Reflexes • Involuntary response to stimuli that occurs at the level of the spinal cord; does not include brain • 4 parts: • Stimuli • Sensory neuron • Motor neuron • Response organ

14. Spinal Cord Reflexes Reflexes include: • Patellar reflex: tap patellar tendon & knee jerks • Achilles tendon reflex: tap Achilles tendon should have plantar flexion • Withdrawl reflex • Pupillary reflex • Baroreceptor reflex: If BP changes heart & blood vessels respond to maintain BP • Babinski reflex: stroke lateral foot heel to toe; an adult should curl their toes: plantar flexion • Gag reflex: prevents aspiration

16. Cerebrum • Largest part of brain • Contains right & left hemisheres • Joined together by corpus callosum • Each hemisphere has 4 major lobes • Frontal • Parietal • Temporal • Occipital

17. Cerebrum • Contains both gray & white matter • Gray matter forms outer layer called cerebral cortex & is composed of cell bodies & interneurons. This allows us to perform higher mental tasks such as reasoning, learning, language & memory • White matter is located below the cortex & is composed of myelinated axons that form connections between spinal cord & brain • There are patches of gray matter scattered throughout

18. Cerebrum Structures of the surface of cerebrum: • Convolutions or gyri: elevations along the surface of the cerebrum • The more convolutions the greater the intelligences • Sulci: grooves that separate gyri • Fissures: deep sulcus • Sulcus & Fissures seperate the lobes of the brain

19. Cerebral Lobes • Frontal lobe: • Located at front of cranium • Controls voluntary motor activity for opposite side of body • Personality • Emotions • Behavior • High level tasks such as learning & thinking • Motor speech called Broca’s area

20. Cerebral Lobes Parietal Lobe: • Located behind central sulcus • Primarily receives sensory information from the body esp. Skin & muscle • Allows you to experience pain, touch, temperature & proprioception • AKA primary somatosensory area • Because of crossover fibers has role in reading, speech & taste

21. Cerebral Lobes Temporal: • Located inferior to lateral fissure in an area above the ear • Auditory area controls hearing • Olfactory area controls smell • Taste is interpreted • Wernicke’s area is located in the posterior temporal lobe & controls comprehension of speech

22. Cerebral Lobes Occipital Lobe • Located at the back of head • Contains the visual cortex which interprets sight • Allows us to read, interpret what we see, judge distance or see in three dimension

23. Cerebral Cortex Association Area: • Large area of cerebral cortex • Area of analyzing, interpreting & integrating information • Has large stores of knowledge to help interpret information received in an area of the brain. • This allows us to perform higher mental tasks such as reasoning, learning, language & memory • Helps to form personality

24. Cerebrum Patches of Gray: • Located deep within the cerebral white matter • Called Basal Nuclei • Control subconscious: • voluntary movement • facial expression • muscle tone • Dopamine is neurotransmitter responsible for activity

25. Diencephalon Diencephalon Located beneath the cerebrum & above the brain stem • Contains the: • Thalamus • Hypothalamus

26. Hypothalamus Hypothalamus located below the thalamus & above the pituitary gland: • Produces ADH & oxytocin • Produces releasing-hormones affecting the anterior pituitary gland • helps regulate temperature, water balance & metabolism • Also affects autonomic nerves that control BP, HR & respirations

27. Thalamus Thalamus • is located above the hypothalamus & below the cerebrum • sorts out sensory information from lower brain & spinal cord and sends it to the appropriate area in the cerebrum • Allows for more rapid interpretation by the cerebrum

28. Brain Stem Midbrain: • Superior to Pons & extends to the Hypothalamus • Primary reflex center • Regulates visual reflex—coordinated eye movement • Auditory reflex center—turning ear toward sound • Keeps head upright & contributes to balance • Relays sensory & motor information

29. Brain Stem Pons • Superior to Medulla • Acts as bridge for information to travel to and from brain structures • 2 respiratory centers that regulate respiratory rate & rhythm

30. Brain Stem Medulla Oblongata • Connects spinal cord with Pons • Called vital center because of control of HR, BP & respiration • Contains cardiac centers that regulate HR • Contains respiratory centers that regulate respirations • Contains vasomotor center that affects diameter of blood vessels therefore blood pressure • Reflex center for coughing—vomiting—sneezing--swallowing • Relay for sensory & motor information

31. Cerebellum Cerebellum • Located posterior to the medulla & pons & protrudes under the occipital lobe • concerned with involuntary aspects of coordinated voluntary movements • Posture & balance & equilibrium • Uses sensory information from receptors of inner ear to detect movement & changes in head position • Receives information from many areas of body, integrates & produces smooth coordinated muscle response

32. Ventricles Ventricles • Four cavities in the brain • Two lateral within the cerebral hemisphere • Third is midline within the thalamus • Fourth is midline between brainstem & cerebellum • Each contains a capillary network called choroid plexus which forms CSF from blood plasma

33. Protection for Brain Meninges: • Dura Mater: • outermost layer • thick & tough • Arachnoid layer • middle layer • Resembles a spider web • Contain arachnoidvilli which are specialized projections • Pia Mater: • Innermost layer • Soft layer containing many blood vessels

34. Protection for Brain Cerebrospinal fluid: • Third layer of protection • Allows for the exchange of nutrients & waste between blood & CNS neurons • Acts as cushion or shock absorber • Formed from blood within brain within the ventricles by the choroid plexus • Clear fluid containing water, glucose, protein & several ions (Na & Cl) • Adult circulate ½ cup of CSF • Rate of reabsorption is equal to the rate of production • Reabsorb through the arachnoidvilli into the venous sinus of brain & back into systemic circulation

35. Protection for Brain Blood Brain Barrier • Arrangement of cells associated with blood vessels that supply the brain & spinal cord • Selects substances that are allowed to enter the CNS • Prevents certain harmful substances from entering • Not all toxic substances are blocked. i.e alcohol • Some antibiotics do not cross the barrier

36. Cranial Nerves • 12 pairs • Roman Numeral & name according to exit from brain & function • Some are sensory while others are mixed • Carry sensory information for special senses: smell, taste, vision & hearing • Carry sensory information for pressure, pain, temperature & vibration • Carry motor information resulting in voluntary skeletal muscle control • Carry motor information resulting in secretion of glands & contraction of cardiac & smooth muscle

37. Autonomic Nervous System • Part of the PNS • Consists of motor portion of some cranial & spinal nerves • Affects smooth muscle, cardiac muscle & glands • 2 Divisions • Sympathetic • Parasympathetic • Function in opposition • Hypothalamus integrates activity

38. Sympathetic Division • The cell bodies of the sympathetic preganglionic neurons are from the thoracic & lumbar segment of the spinal cord • The axons extend to the sympathetic ganglia in two chains just lateral to the spinal column • Axons of the postganglionic innervate the viscera • One preganglionic neuron synapses with many postganglionic neurons to many effectors creating a widespread effect

39. Sympathetic Division • Neurotransmitters for Sympathetic Division • Acetycholine released by the preganglionic neurons with acetylcholinesterase as an inactivator • Norepinephrine released by the postganglionic neurons with catechol-O-methyltransferase as an inactivator

40. Sympathetic Division • Sympathetic • “Fight or flight” • Active under stress—fear—anger—anxiety-exercise • Manifested by: •  HR & contraction • Dilation of bronchioles • Dilate pupils • Constrict blood vessels • Stimulate sweat glands •  GI motility • Stimulate epinephrine & norepinephrine • Stimulate thick secretions • Vasodilation in skeletal muscles • Conversion of glycogen to glucose

41. Parasympathetic Division • The cell bodies of the parasympathetic preganglionic neurons are in the brainstem & sacral segment of spinal cord • The axons of these neurons are in cranial nerve pairs III, VII, IX, X & extend to the parasympathetic ganglia • The ganglia have a close proximity to visceral effector • One preganglionic neuron synapses with just a few postganglionic neurons to only one effector • Permits more localized response

42. Parasympathetic Division • Acetylcholine is the neurotransmitter to all parasympathetic synapses—preganglionic & postganglionic • Acetylcholineterase is the inactivator

43. Parasympathetic Division • Parasympathetic • “Feed & Breed” • Normal conditions • Manifested by: • Normal resting heart rate • Constricted bronchial tubes • Smaller pupils • No vessel constriction • No stimulation of sweat glands • Normal digestion & peristalisis • No affect on epi or norepi • Stimulates watery secretions

44. Aging & the Nervous System • Decreased blood flow to brain causes decrease in mental function & increase in syncope • Deposit of lipofusion in nerve cells & amyloid in blood vessels impairs cognition—memory—reasoning—orientation • Decrease in norepinephrine alters sleep pattern • Decrease acetycholine impairs short-term memory • Progressive loss of dendrites impairs short-term memory • Decrease in dopamine affects smooth motor function • Decrease in postural ability cause more falls

45. Health History Health History • Need thorough history for baseline • Will determine care • Subjective Data • Current signs & symptoms • Current daily medication • History of recreational drug use or alcohol • Past surgeries or illnesses • Lifestyle—exercise or sedentary • Family history • Recent stressful events

46. History Health History • Once general history is reviewed the nurse will do a focused history related to the nervous system • Some neurological disorders will make it difficult to obtain a history • Question significant other is patient is unable to answer.

47. Subjective Assessment Some questions include: • Orientation: • What is your name? Where are you now? What year is it? • Intellectual Function: • Have patient subtract numbers in a series of 7 • Judgment: • What would you do if you smelled smoke • Perception: • Show a familiar object & to determine if patient can recognize it • Language ability: • Can the patient read a sentence • Memory: • Have patient repeat 4-5 words—repeat in 5 minutes • Pain: • On scale from 0-10 what is pain level

48. Physical Assessment Level of Consciousness • First assessment • From awake & alert to unresponsive • Glasgow Coma Scale • Utilized by many facilities • Internationalized • Simple & clear parameters to assess • 3 areas of assessment • Eye opening • Verbal response • Motor response • Score of 15 is fully alert & oriented • Less than 7 indicates comatose

49. Mental Status • Many neurological disorders & injuries can affect mental status. • Two tool are available to assess cognitive ability • Mini-Mental State Examination • Confusion Assessment Method • Assess a person ability to problem solve—attention span—concentrate—judgement—motor function—memory—orientation • Mental status can be determined just by interacting with the patient with routine nursing care • Take note of hygiene—grooming—mood—choice of dress—behavior

50. Pupils • Important neurological assessment & cranial nerve assessment • Pupils should be equal, round & reactive to light • PERRL • Note size of pupils prior to assessment with pen light • Measured in millimeter • Note abnormally large pupils or small pupils • Medication can affect pupil size • The pupils should be equal • If unequal determine if this is a new finding or history of • Report immediately to physician is new finding