Homeostatic Imbalances Bio 168 Ch 11, 12, 13

Syncope

* A brief loss of consciousness. * Indicates inadequate cerebral blood flow due to low blood pressure, and might follow hemorrhage or sudden emotional stress.

Absence Seizures / Petit Mal

1. Mild forms in which the expression goes blank for a few seconds as consciousness disappears. 2. Typically seen in young children & usually disappear by age 10.

Coma

* Significant unresponsiveness to sensory stimuli for an extended period. • Coma is not deep sleep. • Patient's oxygen use is always below normal resting level. • Factors that induce coma include: 1. Blows to the head that cause widespread cerebral or brain stem trauma. 2. Tumors or infections that invade the brain stem. 3. Metabolic disturbances such as hypoglycemia (abnormal low blood sugar levels) 4. Drug overdose. 5. Live or kidney failure 6. Strokes rarely cause coma unless they are massive and accompanied by extreme swelling of the brain, or located on the brain stem.

Brain Death

* when the brain has suffered irreparable damage, irreversible coma occurs, even though life support measures may restore vitality to other body organs. • Result is a dead brain in an otherwise living body. • Life support can be removed only after death, physicians must determine whether a patient in an irreversible coma is legally alive or dead.

High levels of Ca2 kill cells in two ways.

1. Damages mitochondria, causing them to produce the free radical superoxide, which damages cells directly and can also cause programmed cell death (apoptosis). 2. Turns to the synthesis of certain proteins. Some of these promote apoptosis while others are enzymes that produce the free radical NO and other powerful inflammatory agents.

Microcephaly

Congenital condition involving the formation of a small brain, as evidenced by reduced skull, most children are mentally retarded.

Anterograde Amnesia

Consolidated memories are not lost, but new sensory inputs cannot be associated with old, and the person lives in the here and now from that point on. *Examples= You could carry on an animated conversation with a person, excuse yourself, return five minutes later, and that person does not remember you.

Parkinson's disease

Degeneration of dopamine-releasing neurons of the substantia nigra. 1. Typically strike people in 50-60's. 2. Afflicted individuals have a persistent tremor at rest, forward bent walking posture and shuffling gait, and stiff facial expressions. 3. Destroy dopamine releasing neurons. 4. The drug L-dopa helps to alleviate some symptoms. It passes through the blood brain barrier and is then converted into dopamine.

Fainting

A brief loss of consciousness.

Insomnia

A chronic inability to obtain the amount or quality of sleep needed to function adequately during the day. • Drugs that block actions of orexin and promote sleep may treat. • Sleep requirements vary from four to nine hours a day in healthy people, no way to determine right amount of sleep. • They overestimate the extent of their sleeplessness, and some come to rely on hypnotics (sleep medications), which exacerbate the problem. • Often reflects normal age related changes but the most common cause is psychological disturbance. We have a hard time falling asleep when we are anxious or upset, and depression is often accompanied by early awakening.

Psychoses

A class of severe mental illness in which affected individuals lose touch with reality and exhibit bizarre behaviors. 1. Legal word is insanity. 2. Includes schizophrenia, bipolar, disorder, and some forms of depression.

Dyslexia

A learning disability in 5-15% of the population that specifically affects the ability of otherwise intelligent people to read. 1. Visual symbol and language processing is thought to result from errors arising in one hemisphere. 2. Can be acquired by brain injury or degeneration.

Neuroblastoma

A malignant tumor in children. 1. Arises from cells that retain a neuroblast like structure. 2. Sometimes arise in the brain. 3. Most occur in the PNS.

Alzheimer's Disease (AD)

A progressive degenerative disease of he brain, ultimately results in dementia (mental deterioration). 1. Represent nearly half of the people in nursing homes. 2. Between 5 -15% of people over 65 develop. 3. Half of those over 85 it is a major cause of their deaths. 4. Exhibit memory loss, shortened attention span, disorientation, and eventual language loss. 5. Irritable, moody, confused and hallucinations. 6. Plaque littering the brain like shrapnel between neurons. 7. Plaque consists of extracellular aggregations of beta-amyloid peptide 8. Neurofibrillary tangles are inside the neurons. Tangles involve a protein called tau, which function like railroad ties to bind microtubule tracks together. 9. Brain cells die and the Brain shrinks. 10. Shortage of the acetylcholine slightly enhance cognitive function.

Spinal Shock

A transient period of functional loss that follows the injury. 1. Immediately depresses all reflex activity caudal to the lesion site. 2. Bowell and bladder reflexes stop, blood pressure falls, and all muscles below the injury are paralyzed and insensitive. 3. Neural function usually returns within a few hours following injury. 4. If function does not resume within 48 hours, paralysis is permanent in most cases.

Peripheral Neuropathy

Disease of the peripheral nerves characterized by muscle weakness and atrophy, pain, and numbness. 1. Diabetes is a common cause. 2. Other causes, genetic metabolic disorders, infections or inflammation, and toxins.

Autism

Developmental neurological disorder. 1. Appears in the first three years of life. 2. Characterized by difficulty communicated, forming relationships with others, and responding appropriately to the environment. 3. Occurs in about two per 1000 people. 4. Early behavioral intervention is beneficial.

Dysarthria

Difficulty in articulating speech due to motor pathway disorders that result in weakness, uncoordinated motion, or altered respiration or rhythm. 1. Ex. Lesions of cranial nerves IX, X, and XII result in nasal, breathy speech, and lesion in upper motor pathways produce a hoarse strained voice.

Paresthesia

Abnormal sensations. Localized damage to the spinal cord or root it leads to some functional loss.

Amyotrophic Lateral Sclerosis (ALS)

Also known as Lou Gehrig's disease, is a neuromuscular condition that progressively destroys ventral horn motor neurons and fibers of the pyramidal tracts. 1. Symptoms = loses ability to speak, swallow, breathe, and death within 5 years. 2. Environmental and genetic factors interact to cause ALS. 3. 10% of cases mutation are inherited; spontaneous mutation are probably involved in the rest. 4. Recently the mutations have been localized to genes that involved in RNA processing. 5. Exact mechanism is not clear, presence of excess extracellular glutamate suggest that excitotoxic cell death is involved. 6. Riluzole is a drug that interferes with glutamate signaling, prolongs life treatment.

Paresthesia

An abnormal sensation (burnings numbness, tingling) in the absences of stimuli. Caused by a sensory nerve disorder.

Concussion

An alteration in brain function and usually temporary following a blow to the head. 1. May feel dizzy 2. May lose consciousness. 3. Typically mild and short lived. 4. Mild concussions can be damaging 5. Multiple concussions over time produce cumulative damage. 6. Contusion = Serious concussions can bruise the brain & cause permanent neurological damage. 7. Cortical Contusions = individual may remain conscious. 8. Brain Stem Contusions = always cause coma, lasting from hours to a lifetime because of injury to the reticular activating system.

Encephalopathy

Any disease or disorder of the brain.

Subdural or Subarachnoid Hemorrhage

Bleeding from ruptured vessels in those spaces. Death may result. 1. Hemorrhaging Intracranial if lucid & then begin to deteriorate neurologically. 2. Blood accumulating in the skull increases intracranial pressure and compresses brain tissue. 3. If the pressure forces the brain stem inferiorly through the foramen magnum, control of blood pressure, heart rate, & respiration is lost. 4. Intracranial hemorrhages are treated by surgically removing the hematoma (localized blood mass) and repairing the ruptured vessels.

Spinal Roots of the Lumbar Plexus Compressed

By a herniated disc, gait problems occur because the femoral nerve serves the prime movers that flex the hip and extend the knee. 1. Other symptoms of pain or numbness f the anterior thigh and of the medial thigh.

Hydrocephalus

Condition such as a tumor obstructs it circulation or drainage, CSF accumulates and exerts pressure on the brain. Also known as "Water on the brain". • Enlarges the head of a newborn baby because the skull bones have not yet fused. • In adults the skull is rigid and hard and is likely to damage the brain because accumulating fluid compresses blood vessels and crushes the soft nervous tissue. • Is treated by inserting a shunt into the ventricles to drain excess fluid into the abdominal cavity.

Hyperalgesia

Caused by chronic pain and phantom limb pain due to Long lasting or vey intense pain inputs such as limb amputation.

Irritation of Phrenic Nerve

Causes spasms of the diaphragm, or hiccups. 1. Both phrenic nerves are severed, or if the C3-C5 region of the spinal cord is crushed or destroyed, the diaphragm is paralyzed and respiratory arrest occurs. 2. Mechanical respirators keep victims alive by forcing air into their lungs, breathing for them.

Bilateral Destruction

Causes widespread amnesia

Transient Ischemic Attacks (TIAs)

Common type of stroke lasting from 5-50 minutes and are characterized by temporary numbness, paralysis, or impaired speech. 1. Temporary episodes of reversible cerebral ischemia. 2. Deficits are not permanent, but do constitute "red flags" that warn of impending, more serious CVAs.

Hypersomnia

Condition in which affected individuals sleep as much as 15 hours daily.

Transection

Cross sectioning of the spinal cord at any level results in total motor and sensory loss in body regions inferior to the site of damage. 1. Paraplegia =If transection occurs between T1 and L1 bother lower limbs are affected. 2. Quadriplegia = If the injury occurs in the cervical region, all four limbs are affected.

Neuropathy

Disease of nervous tissue, but particularly degenerative disease of nerves.

Foot Drop

Drops into plantar flexion, dangling. 1. Lesions occurs below the knee, thigh muscles are spared. 2. The tibial nerve is injured, the paralyzed calf muscles cannot plantar flex the foot and a shuffling gait develops. 3. Common fibular nerve is susceptible to injury largely because of its superficial location at the head and neck of the fibula. 4. A tight leg cast, or lying too long on your side on a firm mattress can compress this nerve and cause foot drop.

Paralysis

Loss of motor function. Localized damage to the spinal cord or root it leads to some functional loss.

Glutamate

Main culprit of CVA's Glutamate biding to NMDA receptors opens NMDA channels that allow Ca2 to enter the stimulated neuron. After brain injury, neurons totally deprived of H2Obeign to disintegrate, unleashing the cellular equivalent of "buckets" of this.

Median Nerve Injury

Makes it difficult to use the pincer grasp (opposed thumb and index finger) to pick up small objects. 1. Because this nerve runs down the midline of the forearm and wrist, it is a frequent casualty of wrist slashing suicide attempts. 2. In carpal tunnel syndrome the medial nerve is compressed.

Hemiplegia

Paralysis of one side of the body, reflects brain injury, not spinal injury.

Huntington's Disease.

Fatal hereditary disorder strikes during middle age. 1. Mutant protein accumulates in brain cells and tissue dies, leads to massive degeneration of the basal nuclei and later of the cerebral cortex. 2. Symptoms = wild, jerky, almost continuous flapping movements called chorea. (Greek for dance). Mental deterioration. 3. Progressive and usually fatal within 15 years of onset symptoms. 4. Treated with drugs that block, dopamine's effects.

Spina Bifida

Forked spine. Incomplete formation of the vertebral arches and involves lumbosacral region. 1. Technical Definition = laminae and spinous processes are missing on at least one vertebra. 2. If severe, neural deficits occur as well.

Poliomyelitis

Gray matter; myelitis = inflammation of the spinal cord which results from the poliovirus, enters the body in feces contaminated water and destroys ventral horn motor neurons. 1. Early symptoms= fever, headache, muscle pain, weakness, and loss of certain somatic reflexes. 2. Later paralysis develops and muscles served atrophy. 3. May die from paralyzed respiratory muscles or from cardiac arrest. 4. Vaccines have nearly eliminated the disease and global effort is ongoing to eradicate it completely.

Traumatic Brain Injuries

Head Injuries are the leading cause of accidental death in North America.

Olfactory Nerves

I. Sensory; Sense of Smell Imbalance = Fracture of ethmoid bone or lesions of olfactory fibers may result in partial or total loss of smell, a condition known as anosmia.

Optic Nerves

II. Sensory; Afferent impulses for Vision Imbalance = Damage to optic nerve results in blindness in the eye served by the nerve. 1. Damage to visual pathway beyond the optic chiasma results in partial visual losses. 2. Visual defects are called anopsias.

Oculomotor Nerves

III. Motor nerves to the eye Imbalance = This nerve paralysis, eye cannot move up, down, or inward. 1. At rest it rotates laterally because the actions of the two extrinsic eye muscles not served by cranial nerves III are unopposed 2. Upper eyelid droops (ptosis), and the person has double vision and trouble focusing on close objects.

Trochlear Nerves

IV. Motor nerves; supply somatic motor fibers to eye muscles. Imbalance = Damage to a trochlear nerve results in double vision and impairs ability to rotate eye inferolaterally.

Glossopharyngeal Nerves

IX. Mixed Nerves that innervate part of tongue and pharynx. Imbalance = Injured or inflamed glossopharyngeal nerves impaired swallowing and taste.

Dystonia

Impaired muscle tone.

Myelitis

Inflammation of the spinal cord.

Shingles

Inflammation of virally infected sensory neurons serving the skin. 1. Caused by varicella zoster virus (chicken pox). 2. Initial infection the virus is transported from the skin lesions to the sensory cell bodies in the sensory ganglia. 3. The immune system holds the virus in check. Remains dormant until the immune system is weakened, often by stress. 4. Viral particles multiply causing nerve pain (neuralgia) and traveled back to the skin, producing scaly blisters. 5. Usually confined to one side of the trunk. 6. Last several weeks, alternating between periods of healing and relapse. 7. Mostly in those over 50. 8. Vaccinations can prevent occurrence and minimize pain.

Sciatic Nerve

Injury to the proximal part of the sciatic nerve, might follow a fall, disc herniation or badly placed injection into the buttock, can impair the lower limbs in a variety of ways depending on the nerve root injured. 1. Characterized by stabbing pain radiating over the course of the sciatic nerve, is common. 2. When nerve is transected, the leg is nearly useless. Cannot flex and the foot and ankle cannot move at all. 3. Foot drops into plantar flexion, a condition called foot drop. 4. Recovery is usually slow and incomplete.

NMDA Receptors

Intense or long lasting pain activates, and is the same receptors that strengthen neural connections during certain kinds of learning. Long Lasting or Very Intense Pain Inputs

Spina Bifida Occulta

Least serious type, only effecting one or a few vertebrae and causes not neural problems. 1. A small dimple or tuft of hair over the site of nonfusion, it has no external manifestations.

Neuroses

Less debilitating class of mental illness. 1. Ex. Severe anxiety (panic attacks), phobias, obsessive compulsive behaviors. 2. Affected individual retains contact with reality.

Coup Injury

Localized injury at the site of the blow

Spina Bifida Cystica

More common and severe form. Saclike cyste protrudes dorsally from the child's spine. 1. Cyst may contain meninges and cerebrospinal fluid (ameningocele) or even portions of the spinal cord and spinal nerve roots (a myelomeningocele, spinal corn in a meningeal sac) 2. Hydrocephalus accompanies in 90% of cases.

Cerebral Palsy

Neuromuscular disability which voluntary muscles are poorly controlled or paralyzed as a result of brain damage. 1. Maybe caused by lack of oxygen during a difficult delivery. 2. Symptoms = spasticity, speech difficulties, seizures, mentally retarded, 1/3 have some deafness, visual impairments, and other motor impairments. 3. Does not get worse over time, but is irreversible. 4. Largest single cause of physical disability in children affecting three out of every 1000 births.

Damage to the hippocampus and surrounding medial temporal lobe structures on either side results in...

Only slight memory loss

Phantom limb pain

Pain perceived in tissue that is no long present. Long Lasting or Very Intense Pain Inputs

Cerebrospinal Fluid (CSF)

Produced and drained at a constant rate.

Stretch Reflexes

Tend to be hypoactive or absent in cases of peripheral nerve damage or ventral horn injury involving the tested area. 1. Reflexes are absent in those with chronic diabetes mellitus or neurosyphilis and during coma. 2. They are hyperactive when lesions of the corticospinal tract reduce the inhibitory effect of the brain on the spinal cord (stroke patients)

Analgesia

Reduced ability to feel pain, but without losing consciousness. An analgesic is a pain relieving drug.

Contrecoup Injury

Ricocheting effect as the brain hits the opposite end of the skull

Flaccid Paralysis

Severe damage to the ventral root or ventral horn cells of the skeletal muscles served. 1. Nerve impulses do not reach these muscles, which cannot move either voluntarily or involuntarily. 2. Without stimulation, the muscles atrophy.

Neuralgia

Sharp spasm like pain along the course of one or more nerves. Maybe caused by inflammation or injury to the nerve(s).

Cerebrovascular Accidents (CVA)

Strokes or brain attacks. 1. Single most common nervous system disorder and the third leading cause of death in North America. 2. Occurs when blood circulation to a brain are is blocked and brain tissue dies. 3. Ischemia = (to hold blood back), deprivation of blood supply to any tissue, impairs the delivery of oxygen and nutrients to cells. 4. Most Common Cause = blood clot that blocks the cerebral artery. A clot can originate outside the brain or form on roughened interior wall of a brain artery narrowed by atherosclerosis. 5. Hemiplegia= paralyzed on one side of the body / common result if someone survives. 6. Most exhibit sensory deficits or have difficulty understanding or vocalizing speech.

Postpolio Syndrome

Survivors from polio epidemic in the 40-50's have begun experiencing extreme lethargy, sharp burning pains in their muscles, and progressive muscle weakness and atrophy. 1. Cause is unknown, but may be because the victims like all people continue to loss neurons throughout their life.

Cerebral edema

Swelling of the brain. 1. Aggravates the injury. 2. At worst it can be fatal in or of itself.

Wrist Drop

Trauma to the radial nerve result, with inability to extend the hand at the wrist. 1. Improper use of a crutch or Saturday night paralysis, in which an intoxicated person falls asleep with an arm draped over the back of a chair or sofa edge, can compress the radial nerve and impair its blood supply.

Primary Visual Cortex Damage

• Damage to the primary visual cortex results in functional blindness. • Individuals with a damaged visual association area can see, but they do not comprehend what they are looking at.

Meningitis

• Inflammation of the meninges, is a serious threat to the brain because a bacterial or viral meningitis may spread to the CNS. • Encephalitis = brain inflammation. • Diagnosing = obtain a sample of the cerebrospinal fluid via a lumbar tap and examining it for microbes.

Rabies

Viral infection of the nervous system transmitted by the bite of an infected mammal. 1. After entry the virus travels via axonal transport in PNS to the CNS where it causes brain inflammation, delirium, and death. 2. A vaccine and antibody based treatment is effective if given before symptoms appear. 3. Rabies in humans is very rare in the US.

During sleep

The brain remains active and oxygen consumption resembles that of the waking state.

Retrograde Amnesia

The loss of memories formed in the distant past.

The CNS is plagued by a number of other congenital malformations triggered by genetic or environment factors during early development.

The most serious are congenital hydrocephalus, anencephaly, and spina bifida.

Spastic Paralysis

Upper motor neurons of the primary motor cortex are damaged. 1. Spinal motor neurons stay intact and spinal reflex activity continues to stimulate the muscles irregularly.

Trigeminal Nerves

V. Fibers run to Orbital Tissue, Sensory Impulses from Nasal Cavity; Sensory Impulses from Anterior Tongue. Imbalance = also called tic douloureux caused by inflammation of the trigeminal nerve. 1. Considered to produce most excruciating pain known, 2. Stabbing pains last for a few seconds to a minute, but it can be relentless, occurring a hundred times a day. 3. Proved by some sensory stimulus such as burning teeth, or even a passing breeze hitting the face. 4. Caused by a loop of artery or vein that compresses the trigeminal nerve near its exit from the brain stem. 5. Analgesics and carbamazepine are only partially effective. 6. Severe cases, surgery relieves the agony, either by moving the compressing vessel or by destroying the nerve. 7. Nerve destruction results in loss of sensation on the side of the face.

Abducens Nerves

VI. Motor; Somatic Motor Fibers to Lateral Rectus Muscle then to the brain. Imbalance= Abduces nerve paralysis, eye cannot be moved laterally. 1. At rest, eyeball rotates medially.

Facial Nerves

VII. Mixed nerves that are chief motor nerves of face. Imbalance = Bells palsy is characterized by paralysis of facial muscles on affected side and partial loss of taste sensation. 1. May develop rapidly, often overnight. 2. Caused by inflamed and swollen facial nerve, possible due to herpes simplex 1 viral infection. 3. Lower eyelids droops, corner of mouth sags, tears drip continuously from eye and eye cannot be completely closed. 4. Treated with corticosteroids. Recovery is complete in 70% cases.

Vestibulocochlear Nerves

VIII. Sensory; Hearing Imbalance= Lesion of cochlear nerve or cochlear receptors result in central, or nerve, deafness. 1. Damage to vestibular division produces dizziness, rapid involuntary eye movement, loss of balance, nausea, and vomiting.

Injured Brachial Plexus

Very Common and when severe, they weaken or paralyze the entire upper limb. 1. Such injuries occurs when the upper limb is pulled hard, stretching the plexus or by blows to the top of the shoulder that force the humorous inferiorly.

Ulnar Nerve Injury

Very vulnerable to injury. 1. Striking the funny bone, the so where this nerve rests against the medial epicondyle makes the little finger tingle. 2. Severe or chronic damage can lead to sensory loss, paralysis, and muscle atrophy. 3. Affected individuals have trouble making a fist and gripping objects. 4. Clawhand= the little and ring fingers become hyperextended at the knuckles and flexed at the distal interphalangeal joints, the hand contorts.

Myoclonus

Violent motion. Sudden contraction of a muscle or muscle part, usually involving muscles of the limbs. 1. Jerks can occur in normal individuals as they are falling asleep. 2. Others due to diseases of the reticular formation of cerebellum.

Anencephaly

Without brain. The cerebrum and part of the brain stem never develop because the neural folds fail to fuse rostrally. 1. Child is totally vegetative, unable to see, hear, or process sensory inputs. 2. Muscles are flaccid, and no voluntary movement is possible. 3. Mental life does not exist. 4. Death occurs soon after birth.

Vagus Nerves

X. Mixed Nerves. Swallowing, breathing, Liver, Lungs, MAJOR ORGANS Imbalance = Vagal nerve paralysis can lead to hoarseness or loss of voice. 1. Other symptoms = difficulty swallowing and impaired digestive system motility. 2. These parasympathetic nerves are important for maintaining the normal state of visceral organ activity. 3. Without their influence, the sympathetic nerves, which mobilize and accelerate vital body processes would dominate and shut down digestion.

Accessory Nerves

XI. Mixed Nerves. Primarily Motor in Function. Motor Fibers to neck and shoulder muscles. Imbalance = Injury to one accessory nerve causes head to turn toward injury side as result of sternocleidomastoid muscle paralysis. 1. Shrugging that shoulder becomes difficult.

Hypoglossal Nerves

XII. Mixed nerves; Motor function; Tongue to the brain stem. Imbalance = Damage to hypoglossal nerves causes difficulties in speech and swallowing. 1. If both nerves are impaired, the person cannot protrude tongue. 2. If only one side is affected, tongue deviates (points) toward affected side, eventually paralyzed side begins to atrophy.

Tonic-Clonic Seizures / Grand Mal

a. The most severe, convulsive form of epileptic seizures. b. Person loses consciousness, often breaking bones during the intense convulsions, showing the incredible strength of these muscle contractions. c. Loss of bowl and bladder control. d. Severe biting of the tongue are common. e. Lasts for a few minutes. f. Then the muscles relax and the person awakens but remains disoriented for several minutes.

Except for during sleep, unconsciousness

is always a signal that brain function is impaired.

Sleep Apnea

• A temporary cessation of breathing during sleep, is scary. • The victim awakes abruptly due to hypoxia (lack of oxygen) a condition that may occur several hundred times per night.

Multiple Sclerosis (MS)

• An autoimmune disease that affects mostly young adults. • Gradually destroys myelin sheaths in the CNS. • Reduces myelin sheaths to nonfunctional hardened lesions called scleroses. • Loss of myelin results in the immune system's attach of myelin proteins which 1. Shunts and short circuits the current so that successive gaps are excited more and more slowly. 2. Eventually impulse conduction ceases. • Axons are not damaged & growing numbers of Na+ channels appear in the demyelinated fibers. This may account for: 1. Variable cycles of remission (symptom free periods) 2. Relapse (disability) • Symptoms include: 1. Visual disturbances (including blindness) 2. Problems controlling muscles (weakness, clumsiness, and ultimately paralysis) 3. Speech disturbances 4. Urinary incontinence

Hypothalamic Disturbances

• Cause a number of disorders including: 1. Severe body wasting 2. Obesity 3. Sleep disturbances 4. Dehydration 5. Emotional imbalances • Example: • The hypothalamus is implicated in failure to thrive, which is a condition characterized by delay in growth or development that occurs when a child is deprived of a warm, nurturing relationship.

Damaged Primary Motor Cortex

• Damage to localized areas of the primary motor cortex (as from a stroke) paralyzes the body muscles controlled by those areas. • If the lesion is in the right hemisphere, the left side of the body will be paralyzed. • Only voluntary control is lost, however the muscles can still contract reflexively. • Destruction of the premotor cortex or part of it, results in loss of the motor skill(s) programmed by that region, but does not impair muscle strength and the ability to perform the discrete individual movements. • Example: The premotor area controlling the flight of your fingers over a computer keyboard were damaged. You could not type with your usual speed, but you could still make the same movements with your fingers. Reprogramming the skill into another set of premotor neurons would require practice, just as the initial learning process did.

Narcolepsy

• Lapse abruptly into REM sleep from the awake state. 1. Episodes last about 15 minutes 2. Can occur without warning 3. Are often triggered by a pleasurable event such as a good joke, or a game of poker. 4. An emotional intense experience can also trigger cataplexy, which is a sudden loss of voluntary muscle control similar to that seen during REM sleep. What occurs during a cataplexy attack: a. Can last seconds or minutes b. Patients remains fully conscious but unable to move c. Hazardous if driving or swimming • Cells in the hypothalamus that secrete peptides called orexins (wake up chemical and also called hypocretins) are selectively destroyed probably by own immune system. • Replacing orexins could be a key to future treatments.

Anterior and Posterior Association Area Tumors or Other Lesions

• May cause mental & personality disorders such as: 1. Loss of judgment 2. Attentiveness 3. Inhibitions 4. Oblivious to social restraints 5. Careless about personal appearance 6. Maybe attack somebody larger than them instead of running • Different problems arise for individuals with lesions in the part of the posterior association area that provides awareness of self in space, such as: 1. Refuse to wash or dress the side of their body opposite to the lesion because, "that does not belong to me."

Viruses & Bacterial Toxins

• Neural tissues use retrograde axonal transport to reach the cell body. • This transport mechanism has been demonstrated for 1. Polio 2. Rabies 3. Herpes Simplex Viruses 4. Tetanus Toxin • Researchers are investigating use of retrograde transport to treat genetic diseases by introducing viruses containing "corrected" genes or microRNA to suppress effective genes.

Impaired Impulse Propagation

• No Na+ entry then no AP (action potential) • Cold & continuous pressure interrupt blood circulation, which hinders the delivery of oxygen & nutrients to neuron processes and impairing their ability to conduct impulses. • Example: Your fingers get numb when you hold an ice cube Your foot goes to "sleep" when you sit on it. When you remove the cold object or pressure, impulses are transmitted again, leading to an unpleasant prickly feeling.

Epileptic Seizures

• Without warning a person with epilepsy may lose consciousness and fall stiffly to the ground, wracking by uncontrollable jerking. • Epileptic seizures reflect a torrent of electrical discharges by groups of brain neurons, and during their uncontrolled activity no other messages can be through. • Epilepsy manifested by one out of 100 of us, is not associated with, nor does it cause, intellectual impairment. • Genetic factors induce some cases, but epilepsy can also result from brain injuries caused by blows to the head, stroke, infections, or tumors. • Epileptic seizures vary in their expression and severity.