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Nursing Case Study TB MeningitisDocument Transcript
CONTENTSIntroduction…………………………………………..Patient’s Profile…………………………………….Anatomy and Physiology……………………..Pathophysiology…………………………………..Medical Management…………………………..Laboratory Results……………………………….Drug Study……………………………………………Nursing Care Plan…………………………………
Tuberculous meningitis is also known as TB meningitis or tubercular meningitis. Tuberculousmeningitis is Mycobacterium tuberculosis infection of the meninges—the system of membraneswhich envelops the central nervous system. It is the most common form of CNS tuberculosis.Fever and headache are the cardinal features. Confusion is a late feature and coma bears a poorprognosis. Meningism is absent in a fifth of patients with TB meningitis. Patients may also havefocal neurological deficits.Causes are Tension headaches are due to contraction (tightness) of the muscles in yourshoulders, neck, scalp, and jaw. They are often related to stress, depression, or anxiety.Overworking, not getting enough sleep, missing meals, and using alcohol or street drugs canmake you more susceptible to headaches. Foods that can trigger a headache include chocolate,cheese, and monosodium glutamate (MSG), a flavor enhancer. People who drink caffeine canhave headaches when they dont get their usual daily amount.Mycobacterium tuberculosis of the meninges is the cardinal feature and the inflammation isconcentrated towards the base of the brain. Infection begins in the lungs and may spread to themeninges by a variety of routes.The signs and symptoms are: fever, seizures, restlessness, loss of appetite, severe headache,nausea and vomiting, stiff neck, sensitivity to light (photophobia) and loss of consciousness.Blood-borne spread certainly occurs and 25% of patients with miliary TB have TB meningitis,presumably by crossing the blood-brain barrier; but a proportion of patients may get TBmeningitis from rupture of a cortical focus in the brain; an even smaller proportion get it fromrupture of a bony focus in the spine. It is rare and unusual for TB of the spine to cause TB of thecentral nervous system, but isolated cases have been described. Diagnosis of TB meningitis ismade by analyzing CSF collected by lumbar puncture. When collecting CSF for suspected TBmeningitis, a minimum of 1ml of fluid should be taken (preferably 5 to 10ml).The CSF usuallyhas a high protein, low glucose and a raised number of lymphocytes. Acid-fast bacilli aresometimes seen on a CSF smear, but more commonly, M. tuberculosis is grown in culture. Aspider web clot in the collected CSF is characteristic of TB meningitis, but is a rare finding.More than half of cases of TB meningitis cannot be confirmed microbiologically, and thesepatients are treated on the basis of clinical suspicion only. The culture of TB from CSF takes aminimum of two weeks, and therefore the majority of patients with TB meningitis are started ontreatment before the diagnosis is confirmed.Imaging studies such as CT or MRI may show features strongly suggestive of TB meningitis, butcannot diagnose it.The treatment of TB meningitis is isoniazid, rifampicin, pyrazinamide and ethambutol for twomonths, followed by isoniazid and rifampicin alone for a further ten months. Steroids are alwaysused in the first six weeks of treatment (and sometimes for longer). A few patients may requireimmunomodulatory agents such as thalidomide. Treatment must be started as soon as there is areasonable suspicion of the diagnosis. Treatment must not be delayed while waiting forconfirmation of the diagnosis. Hydrocephalus occurs as a complication in about a third ofpatients with TB meningitis and will require a ventricular shunt.
Name: R.H.P.Address: Blk 15 Lot 20 Phase 3 Paliparan, Dasmariñas, CaviteDate of Birth: October 8, 1990Birthplace: ManilaAge: 18 years oldSex: FemaleCivil Status: SingleNationality: FilipinoReligion: CatholicOccupation: Sales ladyAdmission Date/Time: January 8, 2009 – 1:39 amAttending Physician: Dr. L.M.G.ADMITTING HISTORY This is a case of an 18 year old, female patient who was admitted at San Lazaro Hospitallast January 8, 2009 – 1:39 am with chief complaints of fever. • 21 days PTA: fever, low – mod grade, tolerable headache and vomiting • 14 days PTA: patient had a fever; consult was done at a private clinic. Patient was diagnosed to have UTI, was given unrecalled antibiotics. • 13 days PTA: (+) High grade fever 39°C, vomiting, colds. • 12 days PTA: Patient was confined at Emilio Aguinaldo Hospital in Cavite, and was diagnosed to have UTI and migraine, was discharged after 2 hospital days. • 11 days PTA: given Levofloxan once a day times 7 days →vomiting. • 8 days PTA: patient complains of pain on nape area with neck rigidity and headache, fever, no convulsion. • 5 days PTA: dizziness, anorexia, HA, with pain at her back characterized as pricking sensation. x-ray was done revealing ® apical densities. Tramadol, Metoclopromide, Vitaplus and Demachlor were given. Patient was then referred to this institution for evacuation and management. • Few hours PTC: generalized body weaknessPHYSICAL ASSESSMENT • GS: weak looking, conscious, coherent • Skin: (-) jaundice, (-) pallor, (-) cyanosis, no active dermatoses • HEENT: (+) dry lips, NAD • C/L: SCE, (-) retractions, (-) crackles, no wheezes noted • AP: no murmur • Heart: Normal Rate Regular Rhythm, (-) murmurs • Abdomen: (-) BM from 12-27-08 to present, no mass palpated, no tenderness • GUT: Unremarkable • IE: Unremarkable
• Extremities: no atrophy noted • Neuro: o (+) neck rigidity o (+) brudzinki’s sign o (+) kernig’s sign o (-) babinski reflex • Vital Signs: o B/P= 90/70 o PR=76 o RR=18 o T=38 OCAdmitting Impression: TB Meningitis t/c typhoid feverFinal Diagnosis: TB MeningitisFAMILY HISTORY FATHER MOTHERDIABETES (-) (-)HYPERTENSION (-) (-)ASTHMA (-) (-)PTB (-) (+) The patient had no family history of diabetes, hypertension, as well as respiratory diseasesuch as asthma but had family history of PTB on mother’s side.
Central Nervous System The central nervous system (CNS) is the largest part of the nervous system, and includesthe brain and spinal cord. The spinal cavity holds and protects the spinal cord, while the headcontains and protects the brain. The CNS is covered by the meninges, a three layered protectivecoat. The brain is also protected by the skull, and the spinal cord is also protected by thevertebrae. The central nervous system (CNS) is the part of the nervous system that functions tocoordinate the activity of all parts of the bodies of multicellular organisms. In vertebrates, thecentral nervous system is enclosed in the meninges. The meninges (singular meninx) is thesystem of membranes which envelops the central nervous system. The meninges consist of threelayers: the dura mater, the arachnoid mater, and the pia mater. The primary function of themeninges and of the cerebrospinal fluid is to protect the central nervous system. It contains themajority of the nervous system and consists of the brain (in vertebrates which have them), andthe spinal cord.
The meninges (singular meninx) is the system of membranes which envelops the centralnervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, andthe pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protectthe central nervous system. The space between these membranes is bathed with a spinal fluidmuch like lymph, which serves as a protective cushion for the delicate nerve tissue, and allowssome expansion space for the brain when its blood supply is increased.3 layers of meninges: • Dura mater - (also rarely called meninx fibrosa, or pachymeninx) is a thick, durable membrane, closest to the skull. It consists of two layers, the periosteal layer, closest to the calvaria and the inner meningeal layer. It contains larger blood vessels which split into the capilliaries in the pia mater. It is composed of dense fibrous tissue, and its inner surface is
covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.The falx cerebri separates the hemispheres of the cerebrum. The falx cerebelli separates thelobes of the cerebellum.The tentorium cerebelli separates the cerebrum from the cerebellum.The epidural space is a potential space between the dura mater and the skull. If there ishemorrhaging in the brain, blood may collect here. Adults are more likely than children to bleedhere as a result of closed head injury.The subdural space is another potential space. It is between the dura mater and the middle layerof the meninges, the arachnoid mater. When bleeding occurs in the cranium, blood may collecthere and push down on the lower layers of the meninges. If bleeding continues, brain damagewill result from this pressure. Children are especially likely to have bleeding in the subduralspace in cases of head injury. • Arachnoid mater - The middle element of the meninges is the arachnoid membrane, so named because of its spider web-like appearance. It provides a cushioning effect for the central nervous system. The arachnoid mater exists as a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.The arachnoid and pia mater are sometimes together called the leptomeninges.The subarachanoid space lies between the arachnoid and pia mater. It is filled withcerebrospinal fluid. All blood vessels entering the brain, as well as cranial nerves pass throughthis space. The term arachnoid refers to the spider web like appearance of the blood vesselswithin the space. • Pia mater - The pia or pia mater is a very delicate membrane. It is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. As such it follows all the minor contours of the brain (gyri and sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.Cerebrospinal fluid - is a clear liquid produced within spaces in the brain called ventricles.Like saliva it is a filtrate of blood. It is also found inside the subarachnoid space of the meningeswhich surrounds both the brain and the spinal chord. In addition, a space inside the spinal chord
called the central canal also contains cerebrospinal fluid. It acts as a cushion for the neuraxis,also bringing nutrients to the brain and spinal cord and removing waste from the system.Choroid PlexusAll of the ventricles contain choroid plexuses which produce cerebrospinal fluid by allowingcertain components of blood to enter the ventricles. The choroid plexuses are formed by thefusion of the pia mater, the most internal layer of the meninges and the ependyma, the lining ofthe ventricles.The VentriclesThese four spaces are filled with cerebrospinal fluid and protect the brain by cushioning it andsupporting its weight.The two lateral ventricles extend across a large area of the brain. The anterior horns of thesestructures are located in the frontal lobes. They extend posteriorly into the parietal lobes and theirinferior horns are found in the temporal lobes.The third ventricle lies between the two thalamic bodies. The massa intermedia passes throughit and the hypothalamus forms its floor and part of its lateral walls.The fourth ventricle is located between the cerebellum and the pons.The four ventricles are connected to one another.The two foramina of Munro, which are also know as the interventricular foramina, link thelateral ventricles to the third ventricle.The Aqueduct of Sylvius which is also called the cerebral aqueduct connects the third andfourth ventricles.The fourth ventricle is connected to the subarachnoid space via two lateral foramina of Luschkaand by one medial foramen of Magendie.ANATOMY OF THE CNSBRAIN The center of the nervous system. The brain is located in the head, protected by the skulland close to the primary sensory apparatus of vision, hearing, balance, taste, and smell.
• The frontal lobe is concerned with higher intellectual functions, such as abstract thought and reason, speech (Brocas area in the left hemisphere only), olfaction, and emotion. Voluntary movement is controlled in the precentral gyrus (the primary motor area).• The parietal lobe is dedicated to sensory awareness, particularly in the postcentral gyrus (the primary sensory area). It is also concernes with abstract reasoning, language interpretation and formation of a mental egocentric map of the surrounding area.• The occipital lobe is responsible for interpretation and processing of visual stimuli from the optic nerves, and association of these stimuli with other nervous imputs and memories.• The temporal lobe is concerned with emotional development and formation, and also contains the auditory area responsible for processing and discrimination of sound. It is also the area thought to be responsible for the formation and processing of memories.The brain can be subdivided into several distinct regions:1. Brainstem – consists of medulla oblongata, pons and midbrain. • Medulla oblongata - is the lower portion of the brainstem. It deals with autonomic functions, such as breathing and blood pressure. The cardiac center is the part of the medulla oblongata responsible for controlling the heart rate. • Pons - relays sensory information between the cerebellum and cerebrum; aids in relaying other messages in the brain; controls arousal, and regulates respiration (see respiratory centres). In some theories, the pons has a role in dreaming. • Midbrain (mesencephalon) - The mesencephalon is considered part of the brain stem. Its substantia nigra is closely associated with motor system pathways of the basal ganglia.The human mesencephalon is archipallian in origin, meaning its general architecture is sharedwith the most ancient of vertebrates. Dopamine produced in the substantia nigra plays a role inmotivation and habituation of species from humans to the most elementary animals such asinsects.2. Cerebellum - is a region of the brain that plays an important role in the integration of sensory perception, coordination and motor control. In order to coordinate motor control, there are many neural pathways linking the cerebellum with the cerebral motor cortex (which sends information to the muscles causing them to move) and the spinocerebellar tract (which provides proprioceptive feedback on the position of the body in space). The cerebellum integrates these pathways, like a train conductor, using the constant feedback on body position to fine-tune motor movements.3. Diencephalon - (or interbrain) is the region of the brain that includes the thalamus, hypothalamus, epithalamus, prethalamus or subthalamus and pretectum. The diencephalon is located at the midline of the brain, above the mesencephalon of the brain stem. The diencephalon contains the zona limitans intrathalamica as morphological boundary and signalling center between the prethalamus and the thalamus. • Thalamus - plays an important role in regulating states of sleep and wakefulness. Thalamic nuclei have strong reciprocal connections with the cerebral cortex, forming thalamo-cortico-thalamic circuits that are believed to be involved with consciousness.
The thalamus plays a major role in regulating arousal, the level of awareness, and activity. Damage to the thalamus can lead to permanent coma. • Epithalamus – is a dorsal posterior segment of the diencephalon (a segment in the middle of the brain also containing the hypothalamus and the thalamus) which includes the habenula, the stria medullaris and the pineal body. Its function is the connection between the limbic system to other parts of the brain. • Hypothalamus - is a small part of the brain located just below the thalamus on both sides of the third ventricle. Lesions of the hypothalamus interfere with several vegetative functions and some so called motivated behaviors like sexuality, combativeness, and hunger. The hypothalamus also plays a role in emotion. Specifically, the lateral parts seem to be involved with pleasure and rage, while the medial part is linked to aversion, displeasure, and a tendency to uncontrollable and loud laughing. However, in general the hypothalamus has more to do with the expression of emotions4. Cerebrum - or top portion of the brain, is divided by a deep crevice, called the longitudinal sulcus. The longitudinal sulcus separates the cerebrum in to the right and left hemispheres. In the hemispheres you will find the cerebral cortex, basal ganglia and the limbic system. The two hemispheres are connected by a bundle of nerve fibers called the corpus callosum. The right hemisphere is responsible for the left side of the body while the opposite is true of the left hemisphere.PHYSIOLOGY OF THE CNSMedullaThe medulla is the control center for respiratory, cardiovascular and digestive functions.PonsThe pons houses the control centers for respiration and inhibitory functions. Here it will interactwith the cerebellum.CerebrumThe cerebrum, or top portion of the brain, is divided by a deep crevice, called the longitudinalsulcus. The longitudinal sulcus separates the cerebrum in to the right and left hemispheres. In thehemispheres you will find the cerebral cortex, basal ganglia and the limbic system. The twohemispheres are connected by a bundle of nerve fibers called the corpus callosum. The righthemisphere is responsible for the left side of the body while the opposite is true of the lefthemisphere. Each of the two hemispheres are divided into four separated lobes: the frontal incontrol of specialized motor control, learning, planning and speech; parietal in control of somaticsensory functions; occipital in control of vision; and temporal lobes which consists of hearingcenters and some speech. Located deep to the temporal lobe of the cerebrum is the insula.
CerebellumThe cerebellum is the part of the brain that is located posterior to the medulla oblongata andpons. It coordinates skeletal muscles to produce smooth, graceful motions. The cerebellumreceives information from our eyes, ears, muscles, and joints about what position our body iscurrently in (proprioception). It also receives output from the cerebral cortex about where theseparts should be. After processing this information, the cerebellum sends motor impulses from thebrainstem to the skeletal muscles. The main function of the cerebellum is coordination. Thecerebellum is also responsible for balance and posture. It also assists us when we are learning a new motor skill, such as playing a sport or musical instrument. The Limbic System The Limbic System is a complex set of structures found just beneath the cerebrum and on both sides of the thalamus. It combines higher mental functions, and primitive emotion, into one system. It is often referred to as the emotional nervous system. It is not only responsible for our emotional lives, but also our higher mental functions, such as learning and formation of memories. The Limbic system explains why some things seem so pleasurable to us, such as eating and why some medical conditions are caused by mental stress, such as high blood pressure. There are two significant structures within the limbic system and several smaller structures that are important as well. They are: 1. The Hippocampus 2. The Amygdala 3. The Thalamus 4. The Hypothalamus 5. The Fornix and Parahippocampus 6. The Cingulate GyrusStructures of the Limbic SystemHippocampusThe Hippocampus is found deep in the temporal lobe, shaped like a seahorse. It consists of twohorns that curve back from the amygdala. It is situated in the brain so as to make the prefrontalarea aware of our past experiences stored in that area. The prefrontal area of the brain consultsthis structure to use memories to modify our behavior. The hippocampus is responsible formemory.AmygdalaThe Amygdala is a little almond shaped structure, deep inside the anteroinferior region of thetemporal lobe, connects with the hippocampus, the septi nuclei, the prefrontal area and themedial dorsal nucleus of the thalamus. These connections make it possible for the amygdala toplay its important role on the mediation and control of such activities and feelings as love,
friendship, affection, and expression of mood. The amygdala is the center for identification ofdanger and is fundamental for self preservation. The amygdala is the nucleus responsible forfear.ThalamusLesions or stimulation of the medial, dorsal, and anterior nuclei of the thalamus are associatedwith changes in emotional reactivity. However, the importance of these nuclei on the regulationof emotional behavior is not due to the thalamus itself, but to the connections of these nuclei withother limbic system structures. The medial dorsal nucleus makes connections with cortical zonesof the prefrontal area and with the hypothalamus. The anterior nuclei connect with the mamillarybodies and through them, via fornix, with the hippocampus and the cingulated gyrus, thus takingpart in what is known as the Papezs circuit.HypothalamusThe Hypothalamus is a small part of the brain located just below the thalamus on both sides ofthe third ventricle. Lesions of the hypothalamus interfere with several vegetative functions andsome so called motivated behaviors like sexuality, combativeness, and hunger. Thehypothalamus also plays a role in emotion. Specifically, the lateral parts seem to be involvedwith pleasure and rage, while the medial part is linked to aversion, displeasure, and a tendency touncontrollable and loud laughing. However, in general the hypothalamus has more to do with theexpression of emotions. When the physical symptoms of emotion appear, the threat they posereturns, via the hypothalamus, to the limbic centers and then the prefrontal nuclei, increasinganxiety.The Fornix and ParahippocampalThese small structures are important connecting pathways for the limbic system.The Cingulate GyrusThe Cingulate Gyrus is located in the medial side of the brain between the cingulated sulcus andthe corpus callosum. There is still much to be learned about this gyrus, but it is already knownthat its frontal part coordinates smells and sights, with pleasant memories of previous emotions.The region participates in the emotional reaction to pain and in the regulation of aggressivebehavior.Memory and LearningMemory is defined as: The mental faculty of retaining and recalling past experiences, the act orinstance of remembering recollection. Learning takes place when we retain and utilize pastmemories.Overall, the mechanisms of memory are not completely understood. Brain areas such as thehippocampus, the amygdala, the striatum, or the mammillary bodies are thought to be involvedin specific types of memory. For example, the hippocampus is believed to be involved in spatiallearning and declarative learning (learning information such as what youre reading now), whilethe amygdala is thought to be involved in emotional memory. Damage to certain areas in patientsand animal models and subsequent memory deficits is a primary source of information.However, rather than implicating a specific area, it could be that damage to adjacent areas, or to
a pathway traveling through the area is actually responsible for the observed deficit. Further, it isnot sufficient to describe memory, and its counterpart, learning, as solely dependent on specificbrain regions. Learning and memory are attributed to changes in neuronal synapses, thought tobe mediated by long-term potentiation and long-term depression.There are three basic types of memory: 1. Sensory Memory 2. Short Term Memory 3. Long Term MemorySensory MemoryThe sensory memories act as a buffer for stimuli through senses. A sensory memory retains anexact copy of what is seen or heard: iconic memory for visual, echoic memory for aural andhaptic memory for touch. Information is passed from sensory memory into short term memory.Some believe it lasts only 300 milliseconds, it has unlimited capacity. Selective attentiondetermines what information moves from sensory memory to short term memory.Short Term MemoryShort Term Memory acts as a scratch pad for temporary recall of the information under process.For instance, in order to understand this sentence you need to hold in your mind the beginning ofthe sentence as you read the rest. Short term memory decays rapidly and also has a limitedcapacity. Chunking of information can lead to an increase in the short term memory capacity,this is the reason why a hyphenated phone number is easier to remember than a single longnumber. The successful formation of a chunk is known as closure. Interference often causesdisturbance in short term memory retention. This accounts for the desire to complete a task heldin short term memory as soon as possible.Within short term memory there are three basic operations: 1. Iconic memory - the ability to hold visual images 2. Acoustic memory - the ability to hold sounds. Can be held longer than iconic. 3. Working memory - an active process to keep it until it is put to use. Note that the goal is not really to move the information from short term memory to long term memory, but merely to put it to immediate use.The process of transferring information from short term to long term memory involves theencoding or consolidation of information. This is not a function of time, that is, the longer thememory stays in the short term the more likely it is to be placed in the long term memory. Onorganizing complex information in short term before it can be encoded into the long termmemory, in this process the meaningfulness or emotional content of an item may play a greaterrole in its retention in the long term memory. The limbic system sets up local reverberatingcircuits such as the Papazs Circuit.Long Term MemoryLong Term Memory is used for storage of information over a long time. Information from shortto long term memory is transferred after a short period. Unlike short term memory, long termmemory has little decay. Long term potential is an enhanced response at the synapse within the
hippocampus. It is essential to memory storage. The limbic system isnt directly involved in longterm memory necessarily but it selects them from short term memory, consolidates thesememories by playing them like a continuous tape, and involves the hippocampus and amygdala.There are two types of long term memory: 1. Episodic Memory 2. Semantic MemoryEpisodic memory represents our memory of events and experiences in a serial form. It is fromthis memory that we can reconstruct the actual events that took place at a given point in ourlives. Semantic memory, on the other hand, is a structured record of facts, concepts, and skillsthat we have acquired. The information in the semantic memory is derived from our own episodememory, such as that we can learn new facts or concepts from experiences.There are three main activities that are related to long term memory: 1. Storage 2. Deletion 3. RetrievalInformation for short term memory is stored in long term memory by rehearsal. The repeatedexposure to a stimulus or the rehearsal of a piece of information transfers it into long termmemory. Experiments also suggest that learning is most effective if it is distributed over time.Deletion is mainly caused by decay and interference. Emotional factors also affect long termmemory. However, it is debatable whether we actually ever forget anything or whether it justsometimes becomes increasingly difficult to retrieve it. Information may not be recalledsometimes but may be recognized, or may be recalled only with prompting. This leads us to thethird operation of memory, information retrieval.There are two types of information retrieval: 1. Recall 2. RecognitionIn recall, the information is reproduced from memory. In recognition the presentation of theinformation provides the knowledge that the information has been seen before. Recognition is oflesser complexity, as the information is provided as a cue. However, the recall may be assistedby the provision of retrieval cues which enable the subject to quickly access the information inmemory.
ANATOMY OF THE PNSThe peripheral nervous system includes 12 cranial nerves 31 pairs of spinal nerves. It can besubdivided into the somatic and autonomic systems. It is a way of communication from thecentral nervous system to the rest of the body by nerve impulses that regulate the functions of thehuman body.The twelve cranial nerves are I Olfactory Nerve for smell II Optic Nerve for vision III Oculomotor for looking around IV Trochlear for moving eye V Trigeminal for feeling touch on face VI Abducens to move eye muscles VII Facial to smile, wink, and help us taste VIII Vestibulocochlear to help with balance, equilibrium, and hearing IX Glossopharengeal for swallowing and gagging X Vagus for swallowing, talking, and parasympathetic actions of digestion XI Spinal accessory for shrugging shoulders XII Hypoglossal for tongue more divided into different regions as musclesThe 10 out of the 12 cranial nerves originate from the brainstem, and mainly control thefunctions of the anatomic structures of the head with some exceptions. CN X receives visceralsensory information from the thorax and abdomen, and CN XI is responsible for innervating thesternocleidomastoid and trapezius muscles, neither of which is exclusively in the head.Spinal nerves take their origins from the spinal cord. They control the functions of the rest of thebody. In humans, there are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral
and 1 coccygeal. The naming convention for spinal nerves is to name it after the vertebraimmediately above it. Thus the fourth thoracic nerve originates just below the fourth thoracicvertebra. This convention breaks down in the cervical spine. The first spinal nerve originatesabove the first cervical vertebra and is called C1. This continues down to the last cervical spinalnerve, C8. There are only 7 cervical vertebrae and 8 cervical spinal nerves.Peripheral nervous systemThe PNS is a regional term for the collective nervous structures that do not lie in the CNS. Thebodies of the nerve cells lie in the CNS, either in the brain or the spinal cord, and the longer ofthe cellular processes of these cells, known as axons, extend through the limbs and the flesh ofthe torso. The large majority of the axons which are commonly called nerves, are considered tobe PNS.The peripheral nervous system (PNS) resides or extends outside the central nervous system(CNS), which consists of the brain and spinal cord. The main function of the PNS is to connectthe CNS to the limbs and organs. Unlike the central nervous system, the PNS is not protected bybone or by the blood-brain barrier, leaving it exposed to toxins and mechanical injuries. Theperipheral nervous system is divided into the somatic nervous system and the autonomic nervoussystem.Physiological divisionA less anatomical but much more functional way of dividing the human nervous system isclassification according to the role that the different neural pathways play, regardless of whetheror not they cross through the CNS/PNS: • The somatic nervous system is responsible for coordinating voluntary body movements (i.e. activities that are under conscious control). • The autonomic nervous system is responsible for coordinating involuntary functions, such as breathing and digestion.In turn, these divisions of the nervous system can be further divided according to the direction inwhich they conduct nerve impulses: • Afferent system by sensory neurons, which carries impulses from a somatic receptor to the CNS • Efferent system by motor neurons, which carries impulses from the CNS to an effector • Relay system by interneurons (also called "relay neurons"), which transmit impulses between the sensory and motor neurons (both in the CNS and PNS). • The junction between two neurons is called a synapse. There is a very narrow gap (about 20nm in width) between the neurons called the synaptic cleft. This is where an action potential (the "message" being carried by the neurons, also known as the nerve impulse) is transmitted from one neuron to the next. This is achieved by relaying the message across the synaptic cleft using neurotransmitters, which diffuse across the gap. The neurotransmitters then bind to receptor sites on the neighboring (postsynaptic) neuron, which in turn produces its own electrical/nerve impulse. This impulse is sent to the next synapse, and the cycle repeats itself.
• Nerve impulses are a change in ion balance between the inside and outside of a neuron. Because the nervous system uses a combination of electrical and chemical signals, it is incredibly fast. Although the chemical aspect of signaling is much slower than the electrical aspect, a nerve impulse is still fast enough for the reaction time to be negligible in day to day situations. Speed is a necessary characteristic in order for an organism to quickly identify the presence of danger, and thus avoid injury/death. For example, a hand touching a hot stove. If the nervous system was only comprised of chemical signals, the nervous system would not be able to signal the arm to move fast enough to escape dangerous burns. Thus, the speed of the nervous system is evolutionarily valuable, and is in fact a necessity for life.The Somatic SystemThe somatic nervous system is that part of the peripheral nervous system associated with thevoluntary control of body movements through the action of skeletal muscles, and also receptionof external stimuli. The somatic nervous system consists of afferent fibers that receiveinformation from external sources, and efferent fibers that are responsible for muscle contraction.The somatic system includes the pathways from the skin and skeletal muscles to the CentralNervous System. It is also described as involved with activities that involve consciousness.The basic route of the efferent somatic nervous system includes a two neuron sequence. The firstis the upper motor neuron, whose cell body is located in the precentral gyrus (Brodman Area 4)of the brain. It receives stimuli from this area to control skeletal (voluntary) muscle. The uppermotor neuron carries this stimulus down the corticospinal tract and synapses in the ventral hornof the spinal cord with the alpha motor neuron, a lower motor neuron. The upper motor neuronreleases acetylcholine from its axon terminal knobs and these are received by nicotinic receptorson the alpha motor neuron. The alpha motor neurons cell body sends the stimulus down its axonvia the ventral root of the spinal cord and proceeds to its neuromuscular junction of its skeletalmuscle. There, it releases acetylcholine from its axon terminal knobs to the muscles nicotinicreceptors, resulting in stimulus to contract the muscle.The somatic system includes all the neurons connected with the muscles, sense organs and skin.It deals with sensory information and controls the movement of the body.The Autonomic SystemThe Autonomic system deals with the visceral organs, like the heart, stomach, gland, and theintestines. It regulates systems that are unconsciously carried out to keep our body alive andwell, such as breathing, digestion (peristalsis), and regulation of the heartbeat. The Autonomicsystem consists of the sympathetic and the parasympathetic divisions. Both divisions workwithout conscious effort, and they have similar nerve pathways, but the sympathetic andparasympathetic systems generally have opposite effects on target tissues (they are antagonistic).By controlling the relative input from each division, the autonomic system regulates manyaspects of homeostasis. One of the main nerves for the parasympathetic autonomic system isCranial Nerve X, the Vagus nerve.Ten out of the twelve cranial nerves originate from the brainstem, and mainly control thefunctions of the anatomic structures of the head with some exceptions. The nuclei of cranial
nerves I and II lie in the forebrain and thalamus, respectively, and are thus not considered to betrue cranial nerves. CN X (10) receives visceral sensory information from the thorax andabdomen, and CN XI (11) is responsible for innervating the sternocleidomastoid and trapeziusmuscles, neither of which is exclusively in the head.Spinal nerves take their origins from the spinal cord. They control the functions of the rest of thebody. In humans, there are 31 pairs of spinal nerves: 7 cervical, 12 thoracic, 5 lumbar, 5 sacraland 1 coccygeal. In the cervical region, the spinal nerve roots come out above the correspondingvertebrae (i.e. nerve root between the skull and 1st cervical vertebrae is called spinal nerve C1).From the thoracic region to the coccygeal region, the spinal nerve roots come out below thecorresponding vertebrae. It is important to note that this method creates a problem when namingthe spinal nerve root between C7 and T1 (so it is called spinal nerve root C8). In the lumbar andsacral region, the spinal nerve roots travel within the dural sac and they travel below the level ofL2 as the cauda equina.Cervical spinal nerves (C1-C4)The first 4 cervical spinal nerves, C1 through C4, split and recombine to produce a variety ofnerves that subserve the neck and back of head.Spinal nerve C1 is called the suboccipital nerve which provides motor innervation to muscles atthe base of the skull. C2 and C3 form many of the nerves of the neck, providing both sensory andmotor control. These include the greater occipital nerve which provides sensation to the back ofthe head, the lesser occipital nerve which provides sensation to the area behind the ears, thegreater auricular nerve and the lesser auricular nerve. See occipital neuralgia. The phrenic nervearises from nerve roots C3, C4 and C5. It innervates the diaphragm, enabling breathing. If thespinal cord is transected above C3, then spontaneous breathing is not possible.Brachial plexus (C5-T1)The last four cervical spinal nerves, C5 through C8, and the first thoracic spinal nerve,T1,combine to form the brachial plexus, or plexus brachialis, a tangled array of nerves, splitting,combining and recombining, to form the nerves that subserve the arm and upper back. Althoughthe brachial plexus may appear tangled, it is highly organized and predictable, with littlevariation between people.NeurotransmittersThe main neurotransmitters of the peripheral nervous system are acetylcholine andnoradrenaline. However, there are several other neurotransmitters as well, jointly labeled Non-noradrenergic, non-cholinergic (NANC) transmitters. Examples of such transmitters include non-peptides: ATP, GABA, dopamine, NO, and peptides: neuropeptide Y, VIP, GnRH, Substance Pand CGRP.
The Sympathetic SystemThe Sympathetic DivisionThe sympathetic nervous system activates what is often termed the fight or flight response, as itis most active under sudden stressful circumstances (such as being attacked). This response isalso known as sympathetico-adrenal response of the body, as the pre-ganglionic sympatheticfibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine,which activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline(norepinephrine) from it. Therefore, this response that acts primarily on the cardiovascularsystem is mediated directly via impulses transmitted through the sympathetic nervous system andindirectly via catecholamines secreted from the adrenal medulla.NeuronsNeurons are electrically excitable cells in the nervous system that process and transmitinformation. Neurons are the core components of the brain, the vertebrate spinal cord, theinvertebrate ventral nerve cord, and the peripheral nerves. A number of different types ofneurons exist: sensory neurons respond to touch, sound, light and numerous other stimulieffecting sensory organs and send signals to the spinal cord and brain, motor neurons receivesignals from the brain and spinal cord and cause muscle contractions and affect glands,Interneurons connect neurons to other neurons within the brain and spinal cord.
There are three types of directions of the neurons: • Sensory system by sensory neurons, between the sensory and motor neurons. However, there are relay neurons in the CNS as well. • By function, the peripheral nervous system is divided into the somatic nervous system, autonomic nervous system and the enteric nervous system. The somatic nervous system is responsible for coordinating the body movements, and also for receiving external stimuli. It is the system that regulates activities that are under conscious control. The autonomic nervous system is then split into the sympathetic division, parasympathetic division, and enteric division. The sympathetic nervous system responds to impending danger or stress, and is responsible for the increase of ones heartbeat and blood pressure, among other physiological changes, along with the sense of excitement one feels due to the increase of adrenaline in the system. The parasympathetic nervous system, on the other hand, is evident when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and genitourinary systems. The role of the enteric nervous system is to manage every aspect of digestion, from the esophagus to the stomach, small intestine and colon.Glial cellsGlial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, formmyelin, and participate in signal transmission in the nervous system. In the human brain, glia areestimated to outnumber neurons by about 10 to 1.Glial cells provide support and protection for neurons. They are thus known as the "glue" of thenervous system. The four main functions of glial cells are to surround neurons and hold them inplace, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and todestroy pathogens and remove dead neurons.OrganizationSympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord inthe intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of thespinal cord and extending into the second or third lumbar segments. Because its cells begin in thethoracic and lumbar regions of the spinal cord, the SNS is said to have a thoracolumbar outflow.Axons of these nerves leave the spinal cord in the ventral branches (rami) of the spinal nerves,and then separate out as white rami (so called from the shiny white sheaths of myelin aroundeach axon) which connect to two chain ganglia extending alongside the vertebral column on theleft and right. These elongated ganglia are also known as paravertebral ganglia or sympathetictrunks. In these hubs, connections (synapses) are made which then distribute the nerves to majororgans, glands, and other parts of the body.In order to reach the target organs and glands, the axons must travel long distances in the body,and, to accomplish this, many axons link up with the axon of a second cell. The ends of theaxons do not make direct contact, but rather link across a space, the synapse.In the SNS and other components of the peripheral nervous system, these synapses are made atsites called ganglia. The cell that sends its fiber is called a preganglionic cell, while the cell
whose fiber leaves the ganglion is called a postganglionic cell. As mentioned previously, thepreganglionic cells of the SNS are located between the first thoracic segment and the second orthird lumbar segments of the spinal cord. Postganglionic cells have their cell bodies in theganglia and send their axons to target organs or glands.The ganglia include not just the sympathetic trunks but also the superior cervical ganglion(which sends sympathetic nerve fibers to the head), and the celiac and mesenteric ganglia (whichsend sympathetic fibers to the gut).Relationship to sympatheticWhile an oversimplification, it is said that the parasympathetic system acts in a reciprocalmanner to the effects of the sympathetic nervous system; in fact, in some tissues innervated byboth systems, the effects are synergistic.The Parasympathetic DivisionThe parasympathetic nervous system is part of the autonomic nervous system. Sometimes calledthe rest and digest system or feed and breed. The parasympathetic system conserves energy as itslows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in thegastrointestinal tract.ReceptorsThe parasympathetic nervous system uses only acetylcholine (ACh) as its neurotransmitter. TheACh acts on two types of receptors, the muscarinic and nicotinic cholinergic receptors. Mosttransmissions occur in two stages: When stimulated, the preganglionic nerve releases ACh at theganglion, which acts on nicotinic receptors of the postganglionic nerve. The postganglionic nervethen releases ACh to stimulate the muscarinic receptors of the target organ.The three main types of muscarinic receptors that are well characterised are: • The M1 muscarinic receptors are located in the neural system. • The M2 muscarinic receptors are located in the heart, and act to bring the heart back to normal after the actions of the sympathetic nervous system: slowing down the heart rate, reducing contractile forces of the atrial cardiac muscle, and reducing conduction velocity of the atrioventricular node (AV node). Note, they have no effect on the contractile forces of the ventricular muscle. • The M3 muscarinic receptors are located at many places in the body, such as the smooth muscles of the blood vessels, as well as the lungs, which means that they cause vasoconstriction and bronchoconstriction. They are also in the smooth muscles of the gastrointestinal tract (GIT), which help in increasing intestinal motility and dilating sphincters. The M3 receptors are also located in many glands that help to stimulate secretion in salivary glands and other glands of the body.Nervous TissueThe nervous system coordinates the activity of the muscles, monitors the organs, constructs andalso stops input from the senses, and initiates actions. Prominent participants in a nervous systeminclude neurons and nerves, which play roles in such coordination.Our nervous tissue only
consists of two types of cells. These cells are neurons and neuroglia cells. The neurons areresponsible for transmitting nerve impulses. Neuroglia cells are responsible for supporting andnourishing the neuron cells.Types of neuronsThere are three types of neurons in the body. We have sensory neurons, interneurons, and motorneurons. Neurons are a major class of cells in the nervous system. Neurons are sometimes callednerve cells, though this term is technically imprecise, as many neurons do not form nerves. Invertebrates, neurons are found in the brain, the spinal cord and in the nerves and ganglia of theperipheral nervous system. Their main role is to process and transmit information. Neurons haveexcitable membranes, which allow them to generate and propagate electrical impulses. Sensoryneuron takes nerve impulses or messages right from the sensory receptor and delivers it to thecentral nervous system. A sensory receptor is a structure that can find any kind of change in itssurroundings or environment.Structure of a neuronNeurons have three different parts to them. They all have an axon, a cell body and dendrites. Theaxon is the part of the neuron that conducts nerve impulses. Axons can get to be quite long.When an axon is present in nerves, it is called a nerve fiber. A cell body has a nucleous and italso has other organelles. The dendrites are the short pieces that come off of the cell body thatreceive the signals from sensory receptors and other neurons.Myelin SheathSchwann cells contain a lipid substance called myelin in their plasma membranes. Whenschwann cells wrap around axons, a myelin sheath forms. There are gaps that have no myelinsheath around them; these gaps are called nodes of Ranvier. Myelin sheathes make excellent
insulators. Axons that are longer have a myelin sheath, while shorter axons do not. The diseasemultiple sclerosis is an autoimmune disease where the body attacks the myelin sheath of thecentral nervous system.Information transmissionMessages travel through the SNS in a bidirectional flow. Efferent messages can trigger changesin different parts of the body simultaneously. For example, the sympathetic nervous system canaccelerate heart rate; widen bronchial passages; decrease motility (movement) of the largeintestine; constrict blood vessels; increase peristalsis in the esophagus; cause pupil dilation,piloerection (goose bumps) and perspiration (sweating); and raise blood pressure. Afferentmessages carry sensations such as heat, cold, or pain.The first synapse (in the sympathetic chain) is mediated by nicotinic receptors physiologicallyactivated by acetylcholine, and the target synapse is mediated by adrenergic receptorsphysiologically activated by either noradrenaline or adrenaline. An exception is with sweatglands which receive sympathetic innervation but have muscarinic acetylcholine receptors whichare normally characteristic of PNS. Another exception is with certain deep muscle blood vessels,which have acetylcholine receptors and which dilate (rather than constrict) with an increase insympathetic tone. The sympathetic system cell bodies are located on the spinal cord excludingthe cranial and sacral regions. The preganglonic neurons exit from the vertebral column andsynapse with the postganglonic nerouns in the sympathetic trunk.The parasympathetic nervous system is one of three divisions of the autonomic nervous system.Sometimes called the rest and digest system, the parasympathetic system conserves energy as itslows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in thegastrointestinal tract.