1. gathers sensory input (sense organs via Peripheral NS) --> info in 2. integrates information (CNS - brain & spinal cord) 3. responds with motor output (effector organs via PNS - muscles) The basic structural and functional units of the nervous system are called nerve cells or neurons . Communications between the billions of nerve cells in our nervous systems are what allow us to sense the outside world, think and plan, and make voluntary movement s. Therefore, nerve cells are specialized for communication; they receive, integrate, and transmit information within the brain . Each neuron has 3 main parts: a cell body containing the cytoplasm, the cell nucleus, and numerous organelles; dendrites, which act like antennae for the cell , receiving incoming information; and an axon, which transmits nerve impulses away from the cell body. The axons of nerve cells may be up to a yard long, and the messages they carry, in the form of pulses of electricity, allow one part of the brain to communicate with another. Although messages are carried along axons in the form of pulses of electricity , the pulses of electricity DO NOT cross over from the end of the axon to the next cell in line. At the end of the axon is a swollen knob known as the axon terminal . The axon terminal usually lies closely adjacent to, but not touching, the cell membrane of some part of the next cell in line (the next cell in line is known as the postsynaptic cell ). In between the axon terminal and the membrane of the postsynaptic cell is a gap, known as the synaptic gap . Collectively, these 3 elements, the axon terminal, synaptic gap, and the membrane of the postsynaptic cell, make up the structure of a synapse . Other key players at synapses: neurotransmitters (chemicals released from the axon terminal that diffuse across the synaptic gap to carry the "message" to the postsynaptic cell) receptors (molecules that stick off the postsynaptic membrane). Each receptor has a specific shape . In order for a neurotransmitter to have any effect on a postsynaptic cell, it must be able to fit onto a receptor, as a key fits into a lock.) When a nerve impulse gets to the end of an axon, it triggers release of chemicals called neurotransmitters into the synaptic gap . Acetylcholine ; excitatory (muscle contraction; wakefulness, attention, anger, aggression, sexuality, thirst) Alzheimers Dopamine ; inhibitory (movement, posture, mood) Parkinson’s GABA gamma aminobutyric acid; inhibatory (motor control, vision) Huntington’s Glutamate ; excitatory (learning & memory) Alzheimer’s Norepinephrine (attentiveness, emotions, sleeping, dreaming, learning, and as hormone: vessels contract, heart rate increase) manic depression Serotonin (regulate temp., sleep, mood, appetitie, pain) Depression, impulsive behavior
Lumbar puncture : Find a cause for symptoms possibly caused by an infection (such as meningitis ), inflammation, cancer, or bleeding in the area around the brain or spinal cord (such as subarachnoid hemorrhage ). Diagnose certain diseases of the brain and spinal cord, such as multiple sclerosis or Guillain-Barré syndrome . Measure the pressure of cerebrospinal fluid (CSF) in the space surrounding the spinal cord.. A lumbar puncture may also be done to: Put anesthetics or medicines into the CSF (treat leukemia and other types of cancer). Put a dye in the CSF to visual x-ray ( myelogram ) (disc or a cancer is bulging) Reflexes : The usual set of deep tendon reflexes tested, involving increasingly higher regions of the spinal cord, are: ankle knee abdomen forearm biceps triceps Another type of reflex test is called the Babinski test , (stroking the sole of the foot to assess proper development of the spine and cerebral cortex in babies). Weak or absent response may indicate damage to the nerves outside the spinal cord ( peripheral neuropathy ), damage to the motor neurons just before or just after they leave the spinal cord (motor neuron disease), or muscle disease (urinary incontinence, Guillian-Barr, (autoimmune attacks nerves) hypercalcemia, Cauda equina (nerve roots) EMG Needle inserted into muscle (or use of sensor) …computer reads signal sent from 1 point to another; measures electrical activity
Meningitis is infection of the fluid of a person’s spinal cord and the fluid that surrounds the brain. It is also known as spinal meningitis . Can be caused by bacteria or virus . Viral meningitis less severe . Bacterial meningitis can be quite severe and may result in brain damage, hearing loss or learning disability . Before 1990’s Haemophilus influenzae type b (Hib) was leading cause of bacterial meningitis. Today, leading causes are Streptococcus pneumoniae and Neisseria meningitidis are leading bacterial causes. High fever, headache and stiff neck are common symptoms over age 2 . Symptoms can develop over several hours or 1-2 days . Other symptoms are N & V, sensitivity to looking into bright lights, confusion and sleepiness . Infants may only appear slow or inactive and irritable. Seizures can occur as disease progresses. Diagnosis is made from bacterial culture taken from sample of spinal fluid. Bacterial meningitis is treated with antibiotics . Cultures (C & S) can determine appropriate agent. Antibiotics can reduce risk of dying from meningitis to below 15%. The bacterial are spread through the exchange of respiratory and throat secretions (Coughing, kissing) or close or prolonged contact with someone known to have meningitis caused by Neisseria meningitidis. There is a vaccine against this type of meningitis to control outbreaks (daycare, college dorms).
Facial nerve resembles a telephone cable and contains 7,000 individual nerve fibers. Each fiber carries electrical impulses to a specific facial muscle . Information passing along the fibers of this nerve allows us to laugh, cry, smile, or frown, so it is called “the nerve of facial expression”. When half or more of these nerve fibers are irritated then movements of the facial muscles appear to spasm or twitch. The facial nerve also to tear glands, saliva glands, taste from the front of the tongue and muscle of the stapes in the middle ear. Bell’s Palsy is probably due to the body’s response to a virus that inflames and swells the facial nerve within the temporal bone, and this presses on the nerve in the bony canal it travels through. Common tests are: hearing test : see if cause of damage to nerve has involved hearing nerve or inner ear; balance test ; tear test to measure eye’s ability to produce tears (diminished blinking and absence of tearing can dry the eye out); imaging such as CT or MRI to determine if there is infection, tumor bone fracture or other abnormalities; and electrical test which stimulates the facial nerve to asses extent of damage. If infection is cause, then antibiotics or antivirals used to fight infection. If simple swelling is believed to be cause, steroids often prescribed. Certain circumstances surgical removal of bone around nerve (decompression) may be performed
Each year in the United States, there are more than 700,000 strokes. Stroke is the third leading cause of death in the country. And stroke causes more serious long-term disabilities than any other disease. Nearly three-quarters of all strokes occur in people over the age of 65 and the risk of having a stroke more than doubles each decade after the age of 55. For African Americans, stroke is more common and more deadly - even in young and middle-aged adults - than for any ethnic or other racial group in the United States. Learning about stroke can help you act in time to save a co-worker, friend, or relative. And making changes in your lifestyle can help you prevent stroke. Why is Stroke an Emergency? New treatments are available that greatly reduce the damage caused by a stroke. But you need to arrive at the hospital within 60 minutes after symptoms start to prevent disability. Knowing stroke symptoms, calling 911 immediately, and getting to a hospital are critical. What is a stroke? A stroke is serious - just like a heart attack. A stroke is sometimes called a "brain attack." Most often, stroke occurs when blood flow to the brain stops because it is blocked by a clot. The brain cells in the immediate area begin to die because they stop getting the oxygen and nutrients they need to function. What causes a stroke? There are two kinds of stroke. The most common kind of stroke, called ischemic stroke, is caused by a blood clot that blocks or plugs a blood vessel in the brain. The other kind of stroke, called hemorrhagic stroke, is caused by a blood vessel that breaks and bleeds into the brain.
CVA/TIA: CVA (cerebrovascular accident, stroke) sudden impairment of consciousness and subsequent paralysis. Caused by occlusion or hemorrhage due to thrombosis or embolism in blood vessels supplying blood to brain; loss of blood/oxygen causes necrosis. TIA (transient ischemic attack, little strokes) temporary, recurrent episodes of impairment of consciousness caused by small emboli or ischemia of small portion of the brain; traveling emboli do not cause permanent blockage. Sometimes symptoms of a stroke are difficulty to identify. The stroke victim may suffer brain damage when people nearby fail to recognize the symptoms of a stroke. Now YOU can recognize a stroke by asking three simple questions. Ask the individual to SMILE Ask him or her to RAISE BOTH ARMS Ask the person to SPEAK A SIMPLE SENTENCE (it is a sunny day). If he or she has trouble with any of these tasks, call 9-1-1 immediately. These questions can help to identify facial weakness, arm weakness and speech problems which are hallmark in signs and symptoms of a stroke. Sometimes neurologists can totally reverse the effects of a stroke if treatment is started within 3 hours. There are 3 easy SYMPTOMS to look for to tell if a person has just had a stroke : 1. A twisted face best seen when the person smiles. 2. Slurred speech . 3. Ask the person to stretch out their arms and close their eyes. One side will drift down in a stroke. If you find any one of these symptoms in a person that never had it before, the chance that they've had a stroke is 72%!!!!
MS thought to be autoimmune disease that affects CNS. Surrounding and protecting the nerve fibers of the CNS is a fatty tissue called myelin, which helps nerve fibers conduct electrical impulses. In MS, myelin is lost in multiple areas, leaving scar tissue called sclerosis (plaques, lesions). When myelin or the nerve fiber is destroyed or damaged, the ability of the nerves to conduct electrical impulses to and from the brain is disrupted , and this produces the various symptoms of MS. Comes in 4 clinical courses: Relapsing-Remitting Characteristics (clearly defined flare-ups (relapses, attacks, exacerbations). Episodes of acute worsening of neurologic function, followed by partial or complete recovery periods. (85%) Secondary-Progressive Characteristics (initial period of relapsing-remitting disease followed by steadily worsening disease course with or without flare-ups) 50% developed this form within 10 years of initial diagnosis Primary-Progressive Characteristics (slow but nearly continuous worsening of disease from onset, with no distinct relapses) 10% Progressive-Relapsing Characteristics (steadily worsening disease form onset but also have clear acute relapses with or without recovery) 5% 400,000 Americans diagnosed with MS. Most are diagnosed between ages of 20 and 50, 2-3 times more women than men, mostly of northern European ancestry. Diagnosis is made through complete medical history, nervous system function (reflexes,) and diagnostic tests such as MRI (brain scan), evoked potential tests and spinal tap. 2 basic signs are required to confirm MS: 1. sign of disease in different parts of nervous system 2. signs of at least 2 separate flare-ups Symptoms of MS are unpredictable and vary from person to person. For example, one person may experience abnormal fatigue, while another might have severe vision problems. A person with MS could have loss of balance and muscle coordination making walking difficult, another person with MS could have slurred speech, tremors, stiffness and bladder problems. Some symptoms will come and go over course of disease, others may be more lasting. Evoked Potential Test An evoked potential test measures the brain’s response to various kinds of stimulation. Responses are plotted on a sheet of paper and reviewed by neurologist. There are 3 tests and they are painless. Patient preparation would be hair that is clean and without hairspray. The technologist will measure and mark your head to ensure that accurate placement of small metal discs that will be placed on your scalp. During the visual evoked potential test , you will be asked to focus on the center of a checkerboard pattern that is shifting back and forth. You will have one eye tested at a time and need to stay alert. During the brain stem auditory evoked potential test , the patient would have a brief hearing test followed by a series of clicks in each ear, one at a time. During the somatosensory evoked potential test , the patient will feel a slight tingling in hand or foot that may cause fingers or toes to wiggle.
concussion/contusion: Concussion is immediate loss of consciousness with amnesia due to blunt trauma to brain (strike and rebound) Contusion is injury to tissue just beneath surface of brain (bruise) with broken blood vessels (may cause swelling) The brain is composed of soft, delicate structures that lie within the rigid skull. Surrounding the brain is a tough, leathery outer covering called the dura (door-a). The brain is cushioned by blood and spinal fluid. There is very little extra room within the skull cavity. An injury to the head causes the brain to bounce against the rigid bone of the skull . This force may cause a tearing or twisting of the structures and blood vessels of the brain, which results in a breakdown of the normal flow of messages within the brain. The damage to the brain generally is found deep within the brain tissue . Because of this damage, the normal function of the brain signals are interrupted. Concussion categories Grade 1 The mild concussion occurs when the person does not lose consciousness (pass out) but may seem dazed. Grade 2 The slightly more severe form occurs when the person does not lose consciousness but has a period of confusion and does not recall the event. Grade 3 The classic concussion, which is the most severe form, occurs when the person loses consciousness for a brief period of time and has no memory of the event. Evaluation from a health-care provider should be performed as soon as possible after the injury. A concussion can happen to anyone, at any time. The most common causes of concussion include a blow to the head from a motor vehicle crash, fall or assault. People at higher risk are those who have difficulty walking and fall often, those who are active in high impact contact sports and those who are taking blood thinners, such as coumadin. Mild head injury, such as concussion is a frequent cause for hospital admission, with an estimate of more than 600,000 cases per year in the United States. Signs and symptoms The signs and symptoms of a concussion include severe headache, dizziness, vomiting, increased size of one pupil or sudden weakness in an arm or leg. The person may seem restless, aggitated or irritable. Often, the person may have memory loss or seem forgetful. These symptoms may last for several hours to weeks, depending on the seriousness of the injury. Any period of loss of consciousness or amnesia of the head injury should be evaluated by a health-care professional. As the brain tissue swells, the person may feel increasingly drowsy or confused. If the person is difficult to awaken or passes out, medical attention should be sought immediately. This could be a sign of a more severe injury.
Shaken baby syndrome (SBS) is a collective term for the internal head injuries a baby or young child sustains from being violently shaken. Shaken baby syndrome was first described in medical literature in 1972. Physicians earlier labeled these injuries as accidental, but as more about child abuse became known, more cases of this syndrome were properly diagnosed. Every year, nearly 50,000 children in the United States are forcefully shaken by their caretakers. More than 60% of these children are boys. The victims are on average six to eight months old, but may be as old as five years or as young as a few days. Men are more likely than women to shake a child; typically, these men are in their early 20s and are the baby's father or the mother's boyfriend. Women who inflict SBS are more likely to be babysitters or child care providers than the baby's mother. The shaking may occur as a response of frustration to the baby's inconsolable crying or as an action of routine abuse. Causes and symptoms Infants and small children are especially vulnerable to SBS because their neck muscles are still too weak to adequately support their disproportionately large heads, and their young brain tissue and blood vessels are extremely fragile. When an infant is vigorously shaken by the arms, legs, shoulders, or chest, the whiplash motion repeatedly jars the baby's brain with tremendous force, causing internal damage and bleeding. While there may be no obvious external signs of injury following shaking, the child may suffer internally from brain bleeding and bruising (called subdural hemorrhage and hematoma); brain swelling and damage (called cerebral edema); mental retardation; blindness, hearing loss, paralysis, speech impairment, and learning disabilities; and death. Nearly 2,000 children die every year as a result of being shaken. Physicians may have difficulty initially diagnosing SBS because there are usually few witnesses to give a reliable account of the events leading to the trauma, few if any external injuries, and, upon close examination, the physical findings may not agree with the account given. A shaken baby may present one or more signs, including vomiting; difficulty breathing, sucking, swallowing, or making sounds; seizures; and altered consciousness. Diagnosis To diagnose SBS, physicians look for at least one of three classic conditions: bleeding at the back of one or both eyes (retinal hemorrhage), subdural hematoma, and cerebral edema. The diagnosis is confirmed by the results of either a computed tomography scan (CT scan) or magnetic resonance imaging (MRI).
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