Introduction to Behavioral Neuroscience - PSYC 211 Lecture PDF

Introduction to Behavioral Neuroscience PSYC 211 Lecture 20 of 24 – Neurological problems Textbook Chapter 15 Professor Jonathan Britt Questions? Concerns? Please write to [email protected]  STROKE Worldwide, st...

Introduction to Behavioral Neuroscience PSYC 211 Lecture 20 of 24 – Neurological problems Textbook Chapter 15 Professor Jonathan Britt Questions? Concerns? Please write to [email protected]  STROKE Worldwide, strokes are the second most frequent cause of death, and they are associated with ischemic heart disease (the most frequent cause of death). 1 in 4 adults experience a stroke in their lifetime. The likelihood of having a stroke is related to age – chances double each decade after the age of 45 and reach 1 to 2% per year by age 75. Atherosclerosis Process in which linings of arteries develop a layer of plaque: deposits of cholesterol, fats, calcium, and cellular waste products. Risk factors include age, high blood pressure, smoking, diabetes, high cholesterol levels, obesity, poor diet, and lack of exercise. Precursor to heart attacks (myocardial infarction) and strokes  ATHEROSCLEROSIS Atherosclerotic plaques often form in the internal carotid artery, which supplies blood to the cerebral hemispheres. Plaques cause narrowing of the artery, greatly increasing the risk of a stroke. Narrowing can be visualized in an angiogram, produced by injecting a radiopaque dye into the blood and examining the artery with an X-ray.  ISCHEMIC STROKE Thrombus Blood clot that forms within a blood vessel, which reduces blood flow to the affected area. It can directly cause a stroke or pieces can break off, forming an embolus. Embolus When a piece of tissue (blood clot, fat, or bacterial debris) dislodges from its site of origin and occludes an artery. An embolus can cause a stroke. Ischemic strokes  STROKES Ischemic stroke Hemorrhagic stroke Blockage of a cerebral blood Rupture of a cerebral blood vessel vessel 87% of strokes are ischemic Hemorrhagic strokes  STROKES Depending on size of the affected blood vessel, the amount of brain damage can vary from negligible to massive. Strokes often cause permanent brain damage, but physical therapy, occupational therapy, and speech therapy over days, months, and years often produce dramatic improvements in brain function. Researchers have sought ways to minimize amount of brain damage caused by strokes. One approach for ischemic strokes is to administer drugs that dissolve blood clots to reestablish circulation. “Clot-busting” drugs are called thrombolytics. A popular one is tPA (tissue plasminogen activator). It works best if given within 3-4 hours of an ischemic stroke.  RISK REDUCTION & TREATMENT Various strategies are used to secure and/or remove occlusions. Devices are often thread through the vascular system to the site of an occlusion. These devices include coils (a), aspiration devices (b), and stents (c). After strokes, treatments include… – Drugs that reduce swelling and inflammation – Physical, speech, and/or occupational therapy – Exercise and sensory stimulation (constraint-induced movement therapy)  TUMORS Tumor Mass of cells whose growth is uncontrolled and that serves no useful function. Non-malignant Noncancerous (“benign”) tumor. tumor Has distinct border and cannot metastasize. Malignant Cancerous (“harm-producing”) tumor. tumor Lacks distinct border and may metastasize. Metastasis Process by which cells break off from a tumor, travel through the vascular system, and grow elsewhere in the body  MALIGNANT VS NON-MALIGNANT The major distinction between malignancy and non-malignancy is whether the tumor is encapsulated (whether there is a distinct border between the mass of tumor cells and the surrounding tissue) If there is such a border, the tumor is non-malignant; the surgeon can cut it out, and it will not regrow However, if the tumor is cancerous it grows by infiltrating the surrounding tissue, and there will be no clear-cut border between tumor and normal tissue When surgeons remove malignant tumors, some cancer cells are missed, and they produce new tumors  TUMORS Any tumor growing in the brain, malignant or benign, can produce neurological symptoms and threaten the patient's life Tumors damage brain tissue by two means: compression and infiltration. Even a benign tumor occupies space and thus pushes against the brain Compression can directly destroy brain tissue, or it can do so indirectly by blocking flow of cerebrospinal fluid and causing hydrocephalus (water brain).  MALIGNANT TUMORS Gliomas Glioma is an example of a malignant brain tumor. The tumor initiating cells originate from the neural stem cells that make glia. They rapidly proliferate and are more resistant to chemotherapy and radiation than most tumor cells. The survival rate from malignant gliomas is very low. Basal ganglia glioma Hindbrain glioma  NON-MALIGNANT TUMOR Meningioma is an example of a non- malignant (encapsulated) tumor. It is composed of cells that constitute the meninges – the dura mater or arachnoid membrane – often right between the two cerebral hemispheres. A PROBLEMATIC BUT TECHNICALLY NON-MALIGNANT MENINGIOMA This meningioma (tumor of the meninges) is encapsulated, but it still caused massive brain damage.  INFECTIOUS BRAIN DISEASES (GENERAL TERMINOLOGY) Encephalitis Inflammation of the brain caused by infection (bacterial or viral), toxic chemicals, or allergic reaction The first symptoms are headache, fever, and nausea Meningitis Inflammation of meninges caused by viruses or bacteria The first symptoms are headache and stiff neck  WELL-KNOWN VIRUSES Polio Viral disease that destroys motor neurons of the (acute anterior brain and spinal cord poliomyelitis) Rabies Viral disease that causes brain damage and death; usually transmitted through the bite of an infected animal Herpes Virus that normally causes cold sores near the lips or simplex virus genitals. In rare cases, it enters the brain causing encephalitis and brain damage  TRAUMATIC BRAIN INJURY Closed-Head Injury (Concussion) The brain then recoils in The brain comes into Caused by a blow to the the opposite direction violent contact with the head with a blunt object and smashes against the inside of the skull (coup) skull again (contrecoup)  TRAUMATIC BRAIN INJURY Open Head Injuries Increased pressure in the Caused by penetrating brain Damaged blood vessels brain due to blood loss and injuries (open head injuries) exacerbate the injury inflammation can cause further damage.  TRAUMATIC BRAIN INJURY Traumatic brain injuries (TBI) are a serious health problem In the United States, approximately 1.4 million people visit an emergency room for TBI, 270,000 people are hospitalized, and 52,000 people die from it. Almost a third of deaths caused by injury involve TBI. In survivors, scarring often forms within the brain, around the sites of injury, which increases risk of developing seizures. Even mild, undiagnosed cases of TBI (mTBI) greatly increase a person's risk of developing brain problems down the road. The likelihood of Alzheimer's disease is much higher in a person who has received blows to the head earlier in life.  SEIZURE DISORDERS Seizures have many causes The most common cause of seizures is Other causes include high fevers scarring, which often relates to an (especially in young children) and injury, a stroke, a growing tumor, or a withdrawal from GABA agonists, such developmental brain abnormality as alcohol and barbiturates. Many cases are idiopathic (of unknown causes). Some contributing gene mutations have been identified. These mutations cause neural network instability by affecting… the amount/function of different ion channels in the brain the reciprocal wiring of excitatory and inhibitory neurons the rules that govern synaptic plasticity  SEIZURE DISORDERS Seizure disorder Preferred term for epilepsy Most seizures do not involve convulsions of the body. The ones that do activate neurons in the motor system. Convulsion Violent sequence of uncontrollable muscle movements caused by a seizure Partial (focal) Seizure that begins at a focus and remains localized, not generalizing to rest of brain seizure A simple partial seizure is a seizure that does not produce loss of consciousness. A complex partial seizure is a seizure that produces a loss of consciousness. Generalized Seizure that involves most of the brain (a non-localized seizure). seizure Includes tonic-clonic seizures, atonic seizures, and absence seizures.  SEIZURE DISORDERS Seizures can spread across neighboring areas of the brain within and across episodes.  GRAND MAL SEIZURE Aura Sensation that precedes a seizure. Its exact nature depends on the location of the seizure focus Tonic-clonic A generalized, grand mal seizure typically starts with an aura, followed seizure by a tonic phase and then a clonic phase. This type of seizure involves convulsions. Tonic phase First phase of tonic-clonic seizure, in which all of patient's skeletal muscles are contracted Clonic phase Second phase of a tonic-clonic seizure, in which patient shows rhythmic jerking movements  SEIZURE DISORDERS Children are especially susceptible to seizure disorders Many do not have tonic-clonic episodes but instead have brief seizures that are referred to as spells of absence. Absence seizures (also known as petite mal seizures) are generalized complex seizures. People stop what they are doing, stare off into the distance, and often blink their eyes repeatedly. Most absence seizures are less than 15 seconds.  SEIZURE DISORDERS Seizure disorders are treated with anticonvulsant drugs, such as benzodiazepines, many of which work by increasing effectiveness of inhibitory synapses Most seizure disorders respond well enough to medications that the patient can lead a normal life In a few instances drugs provide little or no help and the seizure foci remain so irritable that brain surgery is required  DISORDERS OF DEVELOPMENT Exposure to certain toxins, viruses, and drugs during pregnancy can impair fetal brain development and cause intellectual disability. Dangerous toxins include organophosphates (from insecticides) and heavy metals such as lead and mercury. Famous viruses that alter brain development include the rubella virus (German measles) and the Zika virus (which spread fast in Brazil several years ago).  DISORDERS OF DEVELOPMENT Alcohol is one of the most dangerous drugs during pregnancy. Babies born to alcoholic women are typically smaller than average and develop more slowly. A particularly serious condition associated with alcohol consumption during the 3rd and 4th week of pregnancy is fetal alcohol syndrome, which is associated with certain facial anomalies and severe intellectual disabilities.  DISORDERS OF DEVELOPMENT Inherited Metabolic Disorders There are hundreds of known inherited metabolic disorders that disrupt normal brain development. “Errors of metabolism” are genetic abnormalities in which the instructions for a particular protein are in error. Typically, an enzyme is not synthesized on account of mutations in both copies of the gene. Phenylketonuria Hereditary disorder caused by the absence of enzyme that (PKU) converts the amino acid phenylalanine to tyrosine Accumulation of phenylalanine causes brain damage unless a special diet is implemented soon after birth Tay-Sachs Heritable, fatal, metabolic storage disorder disease Lack of an enzyme in lysosomes causes accumulation of waste produces and swelling of cells within the brain  DISORDERS OF DEVELOPMENT: DOWN SYNDROME Down syndrome is the result of having an extra twenty-first chromosome. It is congenital, meaning there from birth, but it is not necessarily hereditary. It is characterized by moderate to severe intellectual disability and physical abnormalities After age 30, the brains of people with Down syndrome begin to degenerate in a manner similar to that of Alzheimer's disease.  AUTOIMMUNE DISORDER Multiple sclerosis (MS) An autoimmune demyelinating disease that usually starts in people’s late twenties. Certain genes increase one’s risk for getting MS, but it is generally a sporadic disease - one that is not obviously caused by an inherited gene mutation or an infectious agent. At scattered locations within the central nervous system, myelin sheaths are attacked by the person’s own immune system, leaving behind hard patches of debris called sclerotic plaques Action potentials do not successfully propagate down demyelinated axons Damage occurs in white matter (axon paths) throughout the brain and spinal cord, resulting in a wide variety of neurological disorders  MULTIPLE SCLEROSIS Symptoms of multiple sclerosis often go through cycles (flare ups) and then recede for varying periods of time In most cases, this remitting-relapsing MS is followed by progressive MS. Progressive MS is characterized by a slow, continuous increase in symptoms. There is not yet an effective treatment for multiple sclerosis, but some drugs help a little, including – interferon β - a protein that modulates immune system activity – glatiramer acetate – peptides that mimic myelin (the decoy approach) People who grew up far from equator are more likely to develop MS. One hypothesis is that a childhood disease disrupts the immune system, causing it to attack healthy myelin later in life.