BIOS 1030 Exam 2 Study Guide
BIOS 1030 Exam 2 Study Guide 1748
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BIOS 1030 Exam 2 Study Guide CHAPTER 6 THE MUSCULAR SYSTEM 61 Muscles produce movement or generate tension Voluntary muscle movement we have conscious control over the movements they produce picking up an object Involuntary muscle movement beyond out conscious control heart beating 3 Types of muscle 1 2 3 Skeletal Cardiac Smooth All 3 types of muscle are excitable they contract in response to chemical and or electrical signals from other organ systems 0 All muscles have only one basic mechanism of action they contract shorten then relax returning to their original length Skeletal muscles interacts with the skeleton and causes bones to move or prevent them from moving relative to each other 0 Shivering lifting weights standing still 0 Synergistic muscles muscles that work together to create the same movement 0 Antagonistic muscles muscles that oppose each other Origin one end of a skeletal muscle that joins to a bone that remains relatively stationary Insertion the other end of the muscle attaches to another bone across a joint A single muscle is a group of individual muscle cells all with the same origin and insertion and all with the same function Muscles are arranged in bundles called fascicles each enclosed in a sheath of a type of fibrous connective tissue called fascia Individual muscle cells are tube shaped longer and larger than other cells Myo brils long cylindrical structures arranged in parallel o Actin contractile protein in muscle that forms the thin filaments in the myofibrils o Myosin contractile protein in muscle composed of thick filaments with crossbridges Zline dark line on a single myofibril o Sarcomere a segment of a myofibril from one Zline to the next 0 Actin filaments are structurally linked to the Zline myosin filaments are located entirely within sarcomeres 62 Individual muscle cells contract and relax 4 keys to understanding what makes a skeletal muscle cell contract and relax 1 A skeletal muscle must be activated by a nerve It does not contract on its own 2 Nerve activation increases the concentration of calcium in the vicinity of the contractile proteins 3 The presence of calcium permits contraction the absence of calcium prevents contraction 4 When a muscle cell is no longer stimulated by a nerve contraction ends Motor neurons nerve cells that stimulate skeletal muscle cells to contract Neurotransmitter a chemical released by nerve cells that has either an excitatory or inhibitory effect on another excitable cell another nerve cell or a muscle cell Neuromuscular junction the junction between a motor neuron and a skeletal muscle cell Sarcoplasmic reticulum membranebound chambers similar to endoplasmic reticulum except has a different shape because it must fit into a small amount of space in the cell not occupied by myofibrils Sliding filament mechanism process where muscle contract when sarcomeres shorten and sarcomeres shorten when the thick and thin filaments slide past each other 0 Contraction is inhibited unless calcium is present 0 Relaxation of a muscle cell occurs when nerve activity ends no more calcium is released from the sarcoplasmic reticulum Muscle cells use ATP for contraction o Myosin breaks down ATP into ADP and inorganic phosphate releasing energy to do work and undergo bending 0 At the end of the contractile period energy from the breakdown of ATP is used to transport calcium back into the sarcoplasmic reticulum so relaxation can occur Muscle fatigue a decline in muscle performance during exercise caused by insufficient energy to meet metabolic demands due to depletion of ATP creatine phosphate and glycogen stores within the muscle 63 The activity of muscles can vary 2 different types of muscle contraction isotonic and isometric o Isotonic contractions occurs whenever a muscle shortens while maintaining a constant force Parts of the skeleton have to actually move 0 Isometric contractions force is generated muscle tension increases muscle may shorten but bones and objects do not move Individual muscle cells are organized into groups of cells that all work together Motor unit the motor neuron and all of the muscle cells it controls It is the smallest functional unit of muscle contraction because when the motor neuron is activated all muscle cells in that unit are activated together Muscle tension the mechanical force that muscles generate when they contract Amount of tension depends on 3 factors 1 The number of muscle cells in each motor unit motor unit size 2 The number of motor units active at any one time 3 The frequency of stimulation of individual motor units Motor unit size can vary widely from one muscle to the next Allor none principle muscle cells are completely under the control of their motor neuron muscle cells never contract on their own 0 Twitch a complete cycle of contraction and relaxation every time they are stimulated by an electrical impulse or action potential Muscle tone intermediate level of force maintained by whole muscles 0 Some of the muscle s motor units are contracting while others are relaxed 0 Recruitment increasing tone by activating more motor units Stimulustwitch relationship has 3 stages 1 Latent period the time between stimulation and the start of contraction The time it takes for the nerve impulse to travel to the sarcoplasmic reticulum to release calcium and for the myosin heads to bind to the actin filaments 2 Contraction The time during which the muscle actually shortens Actin filaments are pulled toward the center of the sarcomere and myofibrils shorten 3 Relaxation Muscle returns to its original length Calcium is transported back into the sarcoplasmic reticulum sarcomere stretches passively back to its original length Summation increasing muscle force by increasing the rate of stimulation of motor units Humans have 2 types of skeletal muscle fibers 0 Slowtwitch fibers break down ATP slowly contracts slowly Contains many mitochondria and blood vessels draws more blood and oxygen 0 Fasttwitch fibers contracts more quickly than slowtwitch fibers because they break down ATP more quickly Have fewer mitochondria and fewer blood vessels stores large amounts of glycogen 2 primary types of exercise 0 Strength training exercises that strengthen specific muscles short and intense builds muscle mass and muscle strength but does not increase the number of muscle cells 0 Aerobic training involves activity in which the body increases its oxygen intake to meet the increased demands for oxygen by the muscles builds endurance 64 Cardiac and smooth muscles have special features Cardiac and smooth muscle are involuntary muscles because we generally do not have control over them and contracts entirely on their own without stimulation by nerves Cardiac muscles have intercalated discs containing gap junctions that permit one cell to electrically stimulate the next one Smooth muscle cells are also joined by gap junctions that permit the cells to activate each other so that the whole tissue contracts together in a coordinated fashion Speed and sustainability skeletal muscle is the fastest cardiac is of moderate speed and smooth muscle is very slow Skeletal and cardiac muscle are striated meaning that they have a regular array of thick and thin filaments arranged in sarcomeres 65 Diseases and disorders of the muscular system Muscular dystrophy a single defective gene results in the lack of a particular muscle cell protein The normal gene when present directs the cell to produce a protein called dystrophin that is part of the muscle cell membrane Tetanus caused by a bacterial infection infection is acquired by a puncture wound to a muscle The bacteria produces a toxin that overstimulates the nerves controlling muscle activity resulting in tetanic contractions Muscle cramps painful uncontrollable re exmediated muscle contractions Caused by the dehydration and ion imbalances that sometimes occur with heavy exercise Pulled muscles results from stretching a muscle too far causing some of the fibers to tear apart Fasciitis in ammation of the connective tissue sheath or fascia that surrounds a muscle Usually caused by straining or tearing the fascia CHAPTER 7 BLOOD 71 The components and functions of blood Blood specialized connective tissue consisting of specialized cells and cell fragments suspended in a watery solution of molecules and ions Blood carries out 3 crucial tasks for the body 1 Transportation transports all substances needed anywhere by the body oxygen hormones nutrients waste 2 Regulation regulates body temperature the volume of water in the body and the pH of body uids 3 Defense contains specialized defense cells that helps protect against infections and illness prevents excessive blood loss through clotting Composition of blood 45 formed elements 55 plasma Formed elements 0 Red blood cells also called erythrocytes transports oxygen to body tissues transports carbon dioxide away from tissues 0 White blood cells defend the body against invading organisms abnormal cells 0 Platelets take part in blood clotting as part of the body s defense mechanisms Plasma pale yellow liquid is the transport medium for blood cells amp platelets 0 Water primary constituent of blood plasma 0 Electrolytes ions contributes to the control of cell function and volume to the electrical charge across cells and to the function of excitable cells sodium potassium calcium etc 0 Proteins I Albumins maintain blood volume and transport electrolytes hormones and wastes I Globulins serve as antibodies and transport substances I Clotting proteins clots blood minimizing blood loss and helping maintain homeostasis after injury 0 Hormones chemical messenger molecules that provide information needed to regulate specific body functions insulin testosterone estrogen etc o Gases I Oxygen needed for metabolism I Carbon Dioxide waste product of metabolism 0 Nutrients and wastes transported by blood throughout the body glucose urea etc Hemoglobin oxygenbinding protein consisting of 4 polypeptide chains each containing a heme group An iron atom in the heme group readily forms a bond with an oxygen molecule 0 Must be a temporary bond so that the oxygen can be released from the cells that need it o Oxyhemoglobin hemoglobin with 4 oxygen molecules attached 0 Deoxyhemoglobin hemoglobin that has given up its oxygen 0 Transports carbon dioxide Hematocrit the percentage of blood that consists of red blood cells relative measure of the oxygencarrying capacity of blood All blood cells originate from stem cells 0 Stem cells cells in the red marrow of certain bones divides repeatedly throughout our lives continually producing immature blood cells Macrophages large cells that destroy old and damaged red blood cells that are removed from the circulating blood Phagocytosis the process of macrophages surrounding engulfing and digesting red blood cells Regulation of red blood cell production is a negative feedback control loop that maintain homeostasis If oxygen availability falls the kidneys secrete a hormone called erythropoietin that is transported into the blood to the red bone marrow where it stimulates stem cells to produce more red blood cells Blood doping injecting erythropoietin to increase red blood cell production and blood oxygencarrying capacity used by some athletes 2 major categories of white blood cells 0 Granular leukocytes neutrophils eosinophils and basophils I Neutrophils 60 of white blood cells surrounds and engulfs foreign cells targets bacteria and fungi I Eosinophils 24 of white blood cells defends the body against large parasites such as worms releases chemicals that moderate the severity of allergic reactions I Basinophils 05 of leukocytes contains histamine which initiates the in ammatory response by causing adjacent blood vessels to release blood plasma into the injured area 0 Agranular leukocytes monocytes and lymphocytes I Monocytes largest white blood cells and makes up 5 filters out of the bloodstream into tissues where they differentiate into the macrophages that engulf invaders and dead cellular debris by phagocytosis active during chronic infections I Lymphocytes 30 of white blood cells B lymphocytes give rise to the plasma cells that produce antibodies defending against microorganisms T lymphocytes targets and destroys specific threats such as bacteria viruses and cancer cells Platelets are essential for blood clotting Once bleeding stops platelets participate in the repair process by releasing proteins that promote blood vessel growth and repair 72 Hemostasis stopping blood loss Hemostasis the natural process of stopping the ow or loss of blood Proceeds in 3 stages 1 Vascular spasm or intense contraction of blood vessels in the area 2 Formation of a platelet plug 3 Blood clotting coagulation Vascular spasms constrict blood vessels to reduce blood ow intense contractions constrict the vessels Platelets stick together to seal a ruptured vessel by swelling developing spiky extensions and clumps together A blood clot forms around the platelet plug formation of a blood clot blood changes from a liquid to a gel 0 Damage to blood vessels stimulates the vessels and nearby platelets to release prothrombin activator converts prothrombin to an enzyme called thrombin requires calcium ions o Thrombin facilitates the conversion of a soluble plasma protein fibrinogen into long insoluble threads of a protein called fibrin 73 Human blood types Blood type classification of blood based on the presence of surface antigens on red blood cells and the presence of antibodies to surface antigens other than one s own 0 Antigen a nonself cell protein that stimulates the immune system of an organism to defend the organism immune system produces an body o Antibody belongs to the class of plasma proteins gamma globulins mount a counterattack on antigens they recognize as nonself Red blood cells are classified according to the ABO blood group system 0 A has A antigens o B has B antigens 0 AB has both A and B antigens o O has neither A nor B antigens If someone is type A they can only receive type A or type 0 blood If given B or AB their antibodies would be provoked to mount an attack against the B antigen of the donated red blood cells causing them to agglutinate or clump together Rh factor red blood cell surface antigen important in blood transfusions o 85 of Americans are Rh positive meaning they carry the Rh antigen on their red blood cells 0 15 are Rh negative meaning they do not have an Rh antigen and their immune systems respond to any foreign Rh antigen by making antibodies against it Blood typing and crossmatching ensure blood compatibility o quot is the presence of the Rh factor I B 2 type B blood and positive for the Rh factor 0 is the absence of the Rh factor I O type 0 blood and negative for the Rh factor AB individuals are called universal recipients because they can receive blood from any type 0 individuals are called universal donors because their blood can be donated to any other type 74 Blood disorders Blood poisoning septicemia or toxemia microorganisms invade the blood overwhelm its defenses and multiply rapidly in blood plasma T o The organisms may be poisonous or may secrete poisonous chemicals 0 May develop from infected wounds severe burns urinary system infections or major dental procedures Mononucleosis a contagious infection of lymphocytes in blood and lymph tissues caused by the EpsteinBarr virus a relative of the virus that causes herpes 0 Symptoms can mimic those of the u fever headache sore throat fatigue and swollen tonsils and lymph nodes 0 Many lymphocytes enlarge and begin to resemble monocytes Anemia reduction in the oxygencarrying capacity of blood 4 major types 0 Irondeficiency anemia when the body is deficient in iron hemoglobin cannot be synthesized properly can be caused by inability of the digestive tract to properly absorb iron 0 Hemorrhagic anemia anemia due to blood loss may be caused by injuries bleeding ulcers excessive menstrual ow or parasites o Pernicious anemia caused by a deficiency of Vitamin B12 absorption by the digestive tract B12 is important for the production or normal red blood cells 0 Hemolytic anemia the result of rupture or early destruction of red blood cells Can be caused by sicklecell disease sickle red blood cells become damaged as they travel through small blood vessels Leukemia uncontrolled production of abnormal white blood cells crowding out the normal white blood cells red blood cells and platelets leukemia cells enter and circulate in the blood 2 categories 0 Acute develops rapidly 0 Chronic Multiple myeloma uncontrolled production of abnormal plasma cells impairs the production of other antibodies and leaving the body vulnerable to infections destroying bone tissue and high levels of calcium in the blood Thrombocytopenia reduction in platelet number can occur due to viral infection anemia leukemia other blood disorders exposure to Xrays or radiation or a reaction to certain drugs 0 Symptoms include easy bruising or bleeding nosebleeds bleeding in the mouth and urine and heave menstrual periods CHAPTER 8 HEART AND BLOOD VESSELS 81 Blood Vessels Transport Blood Cardiovascular system the heart and blood vessels supplies every region of the body with just the right amount of blood 3 types of blood vessels arteries capillaries veins Arteries transports blood away from the heart 0 Muscular and thickwalled so it can stretch under pressure 0 Stores blood with each beat of the heart and provides it to capillaries o Composed of 3 layers I Endothelium attened squamous epithelial cells keep friction to a minimum and promotes smooth blood ow I Layer of smooth muscle thickest layer stiffens arteries and helps them to resist high pressures I Layer of connective tissue outermost layer anchors vessels to surrounding tissues and helps protect them from injury 0 Aneurysm when endothelium becomes damaged and blood seeps through the injured area working its way between the two outer layers and splitting them apart 0 Arterioles the smallest arteries blood pressure falls when owing through the helps regulate the amount of blood that ows into each capillary o Precapillary Sphincter a band of smooth muscle where an arteriole joins a capillary serves as gates that control blood ow into individual capillaries Figure 82 in textbook pg 166 I Vasodilation relaxation of vascular smooth muscle I Can be produced by nerves hormones and conditions of the arterioles and precapillary sphincters Capillaries smallest blood vessels blood exchanges substances with tissues 0 Capillary beds smallest network of capillaries o Capillaries have thin porous walls that allows blood to exchange oxygen carbon dioxide nutrients and waste with tissue cells 0 Functions as biological strainers that permit selective exchange of substances I Lymphatic capillaries picks up excess plasma uid not filtered by the capillaries then transports them to larger lymphatic vessels that return the uid to the veins Veins returns blood back to the heart 0 3 layers but thinner than arteries because blood pressure is low 0 Serve as a blood volume reservoir for the entire cardiovascular system 0 3 mechanisms assist the veins in returning blood to the heart I Contractions of skeletal muscles muscles contract and relax pressing against veins and collapsing them pushing blood toward the heart I Oneway valves inside veins structure of these valves allows blood to ow in one direction only toward the heart I Movements associated with breathing Inhaling causes an increase in abdominal pressure and squeezes abdominal veins pushing blood from the abdomen into the chest and toward the heart 82 The heart pumps blood through the vessels The heart is located in the thoracic cavity between the lungs and behind the sternum chest bone Pericardium tough fibrous sac that encloses the heart protects it anchors it to surrounding structures and prevents it form overfilling with blood Pericardial cavity space that separates the heart and pericardium The heart s walls consist of 3 layers 0 Epicardium outermost layer made of epithelial and connective tissue 0 Myocardium thick middle layer of cardiac muscle contracts every time the heart beats o Endocardium innermost layer endothelial layer resting on a layer of connective tissue lines the blood vessels The heart has 4 chambers left and right atria left and right ventricles 0 Blood returning to the heart from body tissues enters right atrium passes into right ventricle 0 Blood returning from the lungs to the heart enters left atrium passes into left ventricle I Left ventricle is the most muscular of the 4 chambers generates very high pressures to pump blood 0 Septum muscular partition separating left and right sides of the heart The heart has 4 valves left and right atrioventricular valves AV left and right semilunar valves pulmonary and aortic o Tricuspid valve right AV valve has 3 aps o Bicuspid or mitral valve left AV valve has 2 aps o Semilunar valves prevent back ow into the ventricles from the main arteries leaving the heart when the heart relaxes Pulmonary circuit pumping blood through the lungs 1 Blood returning to the heart from the veins enters right atrium 2 Passes through right atrioventricular valve into right ventricle 3 Pumps blood through pulmonary semilunar valve into pulmonary trunk leading to the lungs 4 Enters pulmonary capillaries receives oxygen 5 Flows into pulmonary veins enters left atrium ows through atrioventricular valve into left ventricle Systemic circuit pumps blood to the rest of the body 1 Left ventricle pumps blood through aortic semilunar valve into aorta largest artery 2 Travels through branching arteries and arterioles into capillaries delivering oxygen and nutrients to tissues and removes waste 3 Flows to venules small veins veins then again to right atrium Coronary arteries the heart s own set of blood vessels that supply the heart muscle Cardiac veins collects blood from capillaries in the heart muscle and channel it back to the right atrium The cardiac cycle the sequence of contraction and relaxation o Systole period of contraction o Diastole period of relaxation Consists of three steps 1 Artial systole contraction of the heart begins with the atria both atria contract raising blood pressure and filling ventricles 2 Ventricular systole both ventricles contract simultaneously causing the 2 AV vales to close preventing blood from owing backward into the atria and veins Semilunar valves open and blood is ejected into pulmonary trunk and aorta 3 Diastole both atria and ventricles are relaxed Once ventricular pressure falls below arterial pressures the semilunar valves close AV valves open and blood ows into the heart The sounds of the heart re ect closing heart valves 0 lubDUBlubDUBquot caused by vibrations in the heart I lubquot signals the two AV vales closing during ventricular systole I DUBquot occurs when semilunar valves close during ventricular diastole I murmur when blood ow encounters an obstruction causes unusual heart sounds Cardiac conduction system a group of specialized cardiac muscle cells that initiate and distribute electrical impulses throughout the heart Sinoatrial SA node begins the stimulus that starts a heartbeat a small mass of cardiac muscle cells located near the junction of the right atrium and the superior vena cava Atrioventricular AV node located between atria and ventricles temporarily slows the rate at which the impulse travels giving atria time to contract and empty blood into the ventricles before they contract From the AV node the impulse goes to the atrioventricular AV bundle a group of fibers between ventricles that branch out to Purkinje fibers smaller fibers that carry the impulse to all cells in the myocardium of the ventricles Electrocardiogram ECG or EKG a record of the electrical impulses in the cardiac conduction system Series of 3 formations o P wave electrical impulse traveling across the atria o QRS complex the spread of the impulse down the septum and around the ventricles in the Purkinje fibers 0 T wave the end of electrical activity relaxation of ventricles Arrhythmia abnormality of the rhythm or rate of the heartbeat Ven tricular brillation rapid irregular ventricular contraction 83 Blood exerts pressure against vessel walls Blood pressure the force that blood exerts on the wall of a blood vessel as a result of the pumping action of the heart 0 Systolic pressure the highest pressure of the cycle reached during ventricular systole o Diastolic pressure the lowest pressure occurs during ventricular diastole when the ventricles relax Hypertension when blood pressure is higher than normal Significant risk factor for cardiovascular disease the greater the pressure the greater the strain on the cardiovascular system Increases the risk of heart attacks heart failure strokes kidney damage or even damage to tissues inside the eyes Risk factors include I Heredity I Race I Age I Sex I Obesity I Smoking I Oral contraceptives Hypotension when blood pressure is too low 0 Hypotension is only a problem if blood pressure falls enough to reduce blood ow to the brain causing dizziness and fainting 84 How the cardiovascular system is regulated Homeostatic regulation of the cardiovascular system centers on maintaining a constant arterial blood pressure A constant arterial blood pressure is achieved by regulating the heart rate and force of contraction adjusting the ow into the arteries and by regulating the diameters of all the body s arterioles as a whole adjusting overall ow out of the arteries With arterial blood pressure held relatively constant local blood ows are adjusted to meet local requirements Baroreceptors regions of the large arteries that regulate arterial blood pressure 0 O O Arterial blood vessels are stretched when blood pressure rises Stretched baroreceptors send signals via nerves to the cardiovascular center of the brain Cardiovascular center responds by sending signals via nerves to the heart and blood vessels Lowers heart rate and force of contraction Reduces cardiac output the amount of blood that the heart pumps into the aorta each minute Vasodilation occurs in arterioles increases blood ow through all tissues Reducing cardiac output and increasing ow through the tissues returns arterial pressure to normal Cardiovascular center sends nerve signals to the heart in two sets of nerves 0 O Sympathetic nerves stimulates the heart causing it to beat faster Parasympathetic nerves inhibit the heart causing it to beat slower Hormones epinephrine and norepinephrine also stimulate the heart 85 Cardiovascular disorders a major health issue Angina a sensation of pain and tightness in the chest 0 Warns of impaired blood ow shortness of breath sensation of choking or suffocating o Arteries become narrowed so blood ow to the heart may not be sufficient for the heart s demands Heart attack myocardial infarction sudden death of an area of heart tissue due to oxygen starvation o Happens if blood ow to an area of the heart is impaired for too long 0 Causes permanent damage to the heart the body cannot replace cardiac muscle cells Heart failure when the heart becomes weaker and less efficient at pumping blood occurs when the heart muscle becomes damaged for ant reason 0 When the heart pumps less blood blood backs up in the veins and pressure in the veins and capillaries rises o Congestive heart failure when high capillary blood pressure cause more uid than usual to filter out of the capillaries and into the interstitial space causing uid congestion Embolism sudden blockage of a blood vessel by material oating in the bloodstream 0 Most often is a blood clot that has broken away from a larger clot o Embolism conditions are named according to the area of the body that is affected I Pulmonary embolism blocks blood supply to lungs I Cerebral embolism blocks blood supply to brain I Cardiac embolism blocks blood supply to heart Stroke damage to part of the brain caused by an interruption to its blood supply 0 Brain equivalent of a heart attack 0 Most common cause of brain injury 86 Reducing your risk of cardiovascular disease Do not smoke smokers have twice the risk of heart attacks Watch cholesterol levels high cholesterol increases risk Keep moving regular moderate exercise reduces risk If you have high blood pressure seek treatment Maintain a healthy weight overweight people have higher risk of heart disease and strokes Keep diabetes under control untreated diabetes damages blood vessels Avoid chronic stress association between a person s perceives stress and development of cardiovascular disease CHAPTER 9 THE IMMUNE SYSTEM AND MECHANISMS OF DEFENSE 91 Pathogens Cause Disease Pathogens organisms that cause disease come from outside the body General defense mechanisms of the body 0 Barriers to entry or ways of expelling or neutralizing pathogens before they can do harm skin stomach acid tears vomiting 0 Nonspecific defense mechanisms respond to generalized tissue damage and many of the more common or obvious pathogens including most bacteria and some viruses 0 Specific defense mechanisms enables the body to recognize and kill specific bacteria and other foreign cells and to neutralize Viruses Immune system a complex group of cells proteins and structures of the lymphatic and circulatory systems Pathogens can include o Bacteria o Viruses o Fungi o Protozoa o Prions Bacteria singlecelled organisms that do not have a nucleus or membrane bound organelles 0 Uses ATP as an energy source obtains raw materials from breaking down raw sewage or obtaining nutrients from soil and air 0 Life would not be possible without bacteria 0 Can cause pneumonia tonsillitis tuberculosis botulism toxic shock syndrome syphilis or Lyme disease 0 Antibiotics chemotherapeutic agents that inhibit or abolish the growth of bacteria fungi and protozoa Viruses extremely small infectious agents consisting of a small piece of genetic material RNA or DNA surrounded by a protein coat 0 Cannot grow and reproduce o Enters a living cell takes it over uses cell s organelles to make more viruses 0 Viruses can cause AIDS hepatitis encephalitis rabies colds warts or chicken pox o Antibiotics generally do not work against Viral infections Prions a misfolded form of a normal brain cell protein that can trigger the misfolding of nearby normal forms of the protein as well 0 So many prions can accumulate within affected brain cells that the cells can die and burst releasing prions to affect other brain cells 0 No known cure for prion infection 0 Can cause mad cow disease Factors that determine the danger of a particular pathogen include o Transmissibility how easily it is passed form one person to another 0 Mode of transmission how it is transmitted o Virulence how damaging the resulting disease is Ebola is one of the most virulent pathogens known killing more than 80 of an exposed population in less than two weeks 92 The lymphatic system defends the body Lymphatic system performs 3 important functions 0 Helps maintain the volume of blood in the cardiovascular system 0 Transports fats and fatsoluble vitamins absorbed from the digestive system to the cardiovascular system 0 Defends the body against infection Most of the cells of the immune system are housed in the lymphatic system but can also circulate in blood and enter interstitial uid Basic components of the lymphatic system 0 Network of lymph vessels throughout the body 0 The lymph nodes 0 The spleen o The thymus gland o Tonsils and adenoids Lymphatic vessels transport lymph a milky body uid that contains white blood cells proteins fats and occasional bacteria and viruses 0 Lymphatic capillaries takes up substances including bacteria that are too large to enter a blood capillary o Lymphatic vessels formed by lymphatic capillaries consisting of 3 layers contains oneway valves to prevent back ow of lymph o 2 lymphatic ducts right lymphatic duct thoracic duct Lymph nodes located at intervals along the lymphatic vessels removes microorganisms cellular debris and abnormal cells from the lymph before returning it to the cardiovascular system 0 There are hundreds of lymph nodes clustered in areas of the digestive tract neck armpits and groin Spleen soft fistsized mass located in the upper left abdominal cavity 0 2 types of tissue Red pulp white pulp I Red pulp breaks down microorganisms and old or damaged red blood cells and platelets stores cleansed blood I White pulp contains lymphocytes searching for foreign pathogens does not store blood 0 2 main functions I Controls the quality of circulating red blood cells by removing the old and damaged ones I Helps fight infection 0 Spleen cleanses the blood lymph nodes cleanse lymph 0 We can live without a spleen because its functions are shared by lymph glands liver and red bone marrow Thymus gland located in the lower neck behind sternum and just above the heart secretes hormones thymosin and thymopoietin that cause certain lymphocytes T lymphocytes or T cells to mature and take an active role in specific defenses 0 Size and activity level varies with age most active and largest during childhood then stops growing and slowly shrinks Tonsils masses of lymphatic tissue near the entrance to the throat gathers and filters out many of the microorganisms that enter the throat in food or air 0 Adenoids located in the back of the nasal passages enlarge during childhood 93 Keeping pathogens out the first line of defense Skin effective barrier 4 key attributes 0 Its structure 0 It is constantly being replaced 0 Its acidic pH 0 Production of an antibiotic by sweat glands Pathogen entry in areas not covered by the skin Tears saliva and earwaX tears and saliva contain lysozyme an enzyme that kills bacteria Earwax traps small particles and microorganisms Mucus microorganisms that come in contact with mucus becomes mired and cannot gain access to the cells beneath Digestive and vaginal acids undiluted digestive acid is strong enough to kill nearly all pathogens that enter the digestive tract on an empty stomach Vomiting urination and defecation vomiting rids the body of toxic or infected stomach contents increased acidity of urine inhibits bacterial growth defecation helps remove microorganisms form the digestive tract Resident bacteria beneficial bacteria lives in mucous membranes lining the vagina and digestive tract controls population levels of more harmful organisms by competing successfully against them for food 94 Nonspecific defenses the second line of defense Called nonspecific because they do not target specific pathogens Nonspecific defenses include o Phagocytes 0 Natural killer cells 0 In ammatory response 0 Complement system 0 Interferons o Fever Phagocytes white blood cells that destroy foreign cells through the process of phagocytosis Phagocytosis 6 steps Phagocyte approaches and captures bacterium Phagocyte surrounds bacterium Bacterium becomes enclosed in vesicle Vesicle fuses with lysosomes Lysosomal enzymes digest bacterium Wastes and debris are discarded Neutrophils the first white blood cells to respond to infection They digest and destroy bacteria and some fungi in the blood and tissue uids 0 Macrophages engulfs and digests large numbers of foreign cells especially viruses and bacterial parasites o Eosinophils cluster around large parasites and bombard them with digestive enzymes In ammation triggered when any type of tissue is injured 4 outward signs redness warmth swelling pain 0 Mast cells connective tissue cells specialized to release histamine o Histamine promoted vasodilation of neighboring small blood vessels 0 Basophils white blood cells that also secrete histamine Natural killer NK cells a group of white blood cells lymphocytes that destroy tumor cells and cells infected by viruses able to recognize certain changes that take place in the plasma membranes of tumor cells and virus infected cells Complement system comprises at least 20 plasma proteins that circulate in the blood and assist other defense mechanisms Interferons group of proteins that diffuse to nearby healthy cells bind to their cell membranes and stimulate the healthy cells to produce proteins that interfere with the synthesis of viral proteins making it harder for the viruses to infect the protected cells Fever abnormally high body temperature A modest fever can be beneficial because it makes our internal environment less hospitable to pathogens and enhances the body s ability to fight infections 9195 er 95 Specific defense mechanisms the third line of defense Immune response the activities of the immune system collectively Has 3 characteristics 0 Recognizes and targets specific pathogens or foreign substances 0 Has a quotmemoryquot the capability to store information from past exposures so that it can respond more quickly to later invasions by the same pathogen o Protects the entire body the resulting immunity is not limited to the site of infection Antigen any substance that mobilizes the immune system and provokes an immune response they are generally large protein or polysaccharide molecules The immune system produces specific antibodies to inactivate and attack antigens o All antigens are located only on the outer surface of a cell or virus which is why the immune system cannot detect viruses once they are inside a human cell Major Histocompatibility Complex MHC proteins proteins on the surface of a cell that the immune system uses to recognize that the cells belong to you 2 types of lymphocytes 0 B Cells mature in bone marrow responsible for antibodymediated immunity by producing and releasing antibodies into the blood lymph and tissue uid 0 T Cells mature in thymus gland responsible for cellmediated immunity by not producing antibodies but some directly attack foreign cells that carry antigens and some release proteins that help coordinate other aspects of immune response Plasma cells cloned cells derived from B cells secretes antibodies into the lymph uid and ultimately into the blood plasma Memory cells long lived cells that remain inactive until the same antigen reappears in the body at some future date in time Antibodies belong to the class gamma globulins o Immunoglobin lg 5 classes I IgG 75 of Ig activates the complement system and neutralizes many toxins I IgM 540 first to be released during immune responses activates complement system and causes foreign cells to aggulinate I IgA 15 enters areas of the body with mucous membranes digestive reproductive respiratory tracts neutralizes infectious pathogens I IgD less than 1 function is not clear but may play a role in activating B cells Found in blood lymph and B cells I IgE approx 01 activate in ammatory response by triggering the release of histamine also involved in allergic reactions Antigenpresenting cells APCS certain cells that engulf particles partially digest them and display fragments of the antigens on their surfaces Helper T cells stimulates other T cells undergoes mitosis and quickly produces clones of helper T cells Cytokines a mass of signaling molecules secreted by helper T cells proteins that stimulate the actions of T cells and macrophages and substances that promote development of other immune cells Cytotoxic T cells killer T cells directly attack and destroy other cells circulates through blood lymph and lymphatic tissues in search of cells that display the antigens they recognize 96 Immune memory creates immunity Your first exposure to a particular antigen generates a primary immune response involving recognition of the antigen and production and proliferation of B and T cells Memory cells are the basis for immunity from disease Subsequent exposure to the pathogen elicits a secondary immune response that is faster longer lasting and more effective than the first 97 Medical assistance in the war against pathogens Immunization helps the body resist specific pathogens the production of monoclonal antibodies and the discovery of antibiotics Active immunization the process of activating the body s immune system in advance involving a vaccine 0 Vaccine an antigencontaining preparation produced from dead or weakened pathogens Has limitations of safety time and expense Passive immunization prepared in advance from a human or animal donor with immunity to that illness fights existing or even anticipated infections Monoclonal antibodies antibodies produced in the laboratory from cloned descendants of a single hybrid B cell specific for a single antigen Antibiotics kills bacteria or inhibits their growth Takes advantage of the following differences between bacteria and human cells 0 Bacteria have a thick wall human cells do not 0 Bacterial DNA is not safely enclosed in a nucleus human DNA is 0 Bacterial ribosomes are smaller than human ribosomes 0 Bacterial rate of protein synthesis is very rapid as they grow and divide Broadspectrum antibiotics effective against several groups of bacteria while some antibiotics combat only certain types of bacteria 98 Tissue rejection a medical challenge Tissue rejection when the immune system attacks foreign human tissues To perform an organ transplant the donor and recipient s tissues are tested to compare MHC antigens ABC and other blood group antigens Immunosuppressive drugs must be taken by the patient to block the immune response to suppress in ammation or kill rapidly dividing cells 3 factors have made organ transplants a viable option 0 Improvements in immunosuppressive drugs 0 Better techniques for crossmatching tissue 0 National sharing of information and donor organs through organ bank systems allowing patients to receive the best possible matches 99 Inappropriate immune system activity causes problems Allergy an inappropriate response of the immune system to an allergen o Allergen any substance that causes an allergic reaction 0 Allergens are not dangerous pathogens the body just acts as if it were Allergic reactions happen when the same allergen enters the body a second time and binds to the IgE antibodies on mast cells and basophils causing them to release histamine 0 Results in typical in ammatory response including warmth redness swelling and pain in the area of contact with the allergen Some allergens only affect the exposed areas some are absorbed into the bloodstream Symptoms of a severe allergic reaction include Difficulty breathing caused by constricted airways Severe stomach cramps muscle contractions Swelling throughout the body increased capillary permeability Circulatory collapse with a lifethreatening fall in blood pressure anaphylactic shock dilated arterioles Autoimmune disorders when the immune system produces antibodies and cytotoxic T cells that target its own cells Lupus Erythematosus in amed connective tissue 0 Discoid lupus erythematosus primarily affects areas of the skin exposed to sunlight 0 Systemic lupus erythematosus more serious affects various tissues and organs including the heart blood vessels lungs kidneys joints and brain Rheumatoid arthritis in amed synovial membranes 0 B cells produce antibodies against a protein in the cartilage of synovial membranes 0 Resulting immune response releases in ammatory chemicals that cause further tissue damage 0 O O O 910 Immune deficiency the special case of AIDS AIDS acquired immune de ciency syndromeJHI V human immunode ciency virus HIV enters a cell and uses the cell s machinery to reproduce targeting helper T cells Classified as retroviruses attaches to CD4 receptor of helper T cell fuses the retrovirus s envelope with the cell s membrane releasing the viral RNA and enzymes into the cell 0 Makes DNA strands complementary to the viral RNA HIV is transmitted through body uids 0 Blood semen breast milk and vaginal secretions 0 NOT urine feces saliva perspiration tears or nasal secretions unless they contain blood AIDS develops slowly in 3 phases 0 Phase 1 brief spike of HIV in the blood ulike symptoms T cells population may decline then rebound as they produce more cells and antibodies against the virus Presence of antibodies against the virus is known as being HIV positive but does not yet have AIDS 0 Phase 2 virus wipes out more and more helper T cells making the person more vulnerable to infections that take advantage of the weakened immune system to establish themselves in the body 0 Phase 3 Number of helper T cells of an HIV positive person falls below 200 per cubic millimeter of blood and has an infection or type of cancer associated with HIV the person is said to have AIDS I Pneumonia meningitis tuberculosis encephalitis etc Risky behaviors increase your chance of getting AIDS 0 Abstain from sex Reduce your number of sexual partners Choose a sexual partner with lowrisk behavior Avoid certain highrisk practices analgenital sex Use condoms or other barriers Use nonoxynol9 a spermicidal agent 0 Get both you and your partner tested There is not cure for AIDS but there are hundreds of drugs that can treat the condition Maraviroc inhibits entry of the virus into healthy T cells The production of vaccines is complicated by the fact that AIDS mutates rather quickly can be so dangerous that is it considered too risky to produce vaccines from whole but weakened viruses the way many other vaccines are produced OOOOO CHAPTER 10 THE RESPIRATORY SYSTEM 101 Respiration takes place throughout the body Respiratory system primary function is to exchange gases oxygen and carbon dioxide with the air The term respiration encompasses 4 processes Breathing ventilation the movement of air into and out of lungs External respiration exchange of gases between inhaled air amp blood Internal respiration exchange of gases between blood amp tissue uids Cellular respiration process of using oxygen to produce ATP within cells Generates carbon dioxide as a waste product Breathing is facilitated by the respiratory system and its associated bones muscles and nerves External respiration takes place in the lungs Internal respiration and cellular respiration take place in body tissues 0000 102 The respiratory system consists of upper and lower respiratory tracts The respiratory system consists of o A system of passageways for getting air to and from the lungs o The lungs themselves where gas exchange actually occurs Upper respiratory tract includes the nose nasal cavity and pharynx Lower respiratory tract includes larynx trachea and lungs The upper respiratory track filters warms and humidifies air The nose Contains receptors for the sense of smell Filters inhaled air and screens out some foreign particles Moistens and warms incoming air Provides a resonating chamber that helps gives you voice its characteristic tone External nose the visible portion of the nose Internal nose the nasal cavity External nose and nasal cavity are divided into 2 chambers by nasal septum 0 Air enters through nostril is filtered by nose hairs then ows into the nasal cavity Pharynx throat connects the mouth and nasal cavity to the larynx o Larynx voice box maintains open airway routes food and air into the appropriate channels assists in the production of sound Epiglottis exible ap of cartilage located at the opening to the larynx Vocal cords two folds of connective tissue that extend across the airway 0 Sounds produce by vibration of vocal cords Glottis The opening to the airway Trachea the windpipe that extends from the larynx to the left and right 0000 bronchi o Consists of Cshaped rings of cartilage held together by connective tissue Bronchi airways that branch off the trachea entering into the lung cavity Bronchioles smaller airways that lack cartilage o Cleans the air transports air warm it to body temperature The lungs consist of supportive tissue enclosing the bronchi bronchioles blood vessels and the areas where gas exchange occurs 0 Pleural membranes thin epithelial membranes enclosing each lung outer lung surface and lining thoracic cavity Alveoli airfilled sacs at the end of branching airways 0 One layer of squamous epithelial cells 0 Cells secrete surfactant that coats the interior of alveoli and reduces surface tension Pulmonary capillaries brings blood and air into close contact so that venules and veins collect the blood returning it to the heart 103 The process of breathing involves a pressure gradient Diaphragm broad sheet of muscle that separates the thoracic cavity from the abdominal cavity Inspiration brings in air expiration expels it 0 Gas pressure is caused by colliding molecules of gas 0 When the volume of a closed space increases gas pressure decreases When volume decreases gas pressure increases 0 Gases ow from areas of higher pressure to lower pressure Cycle of inspiration and expiration 1 Relaxed state diaphragm and intercostal muscles are relaxed 2 Inspiration diaphragm and intercostal muscles contract lungs expand as pressure is reduced allowing air to rush in 3 Expiration muscles relax lungs become smaller as pressure rises Tidal volume a breath of air approximately 500 ml or a pint Vital capacity maximum volume that you can exhale after a maximum inhalation about 4800 ml 104 Gas exchange and transport occur passively Partial pressure a gas s pressure that is proportional to its percentage of the total gas composition 0 Gases always fuse down its partial pressure gradient from a region of higher partial pressure to lower partial pressure 0 The partial pressures of alveolar air are not the same as those of inspired air The body s cells get oxygen for cellular respiration from the interstitial uid surrounding them Oxygen enters capillaries then diffuses back into interstitial uid Oxygen is transported in 2 ways 0 Bound to hemoglobin in red blood cells each hemoglobin molecule can bind to 4 oxygen molecules at a time forming oxyhemoglobin o Dissolved in blood plasma Most carbon dioxide is transported in plasma as bicarbonate 70 20 of carbon dioxide binds with hemoglobin to produce carbaminohemoglobin 105 The nervous system regulates breathing Respiratory center area near the base of the brain medulla oblongata where groups of nerve cells automatically generate a cyclic pattern of electrical impulses every 45 seconds causing us to inhale Chemical receptors monitor C02 H and 02 levels mostly C02 We can regulate breathing by conscious control 106 Disorders of the respiratory system Asthma spasmodic contraction of bronchi Emphysema alveoli become permanently impaired Bronchitis in ammation of the bronchi Cystic fibrosis inherited condition a single infected gene causes the mucus producing cells in the lungs to produce a thick sticky mucus Lungs are prone to infections because they are moist warm and covered in a thin layer of uid Diseases causes by microorganisms o Colds and the u Viral respiratory tract infections o Pneumonia infection in ames the lungs o Tuberculosis infection scars the lungs o Botulism poisoning by bacterial toxin Lung cancer caused by proliferation of abnormal cells Pneumothorax and atelectasis failure of gas exchange Congestive heart failure impairs lung function CHAPTER 11 THE NERVOUS SYSTEM 4 Characteristics of the nervous system 1 Receives information from many different sources simultaneously 2 Integrates information assembles different pieces into a whole 3 Very fast receives integrates information and produces a response in 110 of a second 4 Can initiate specific responses 111 The nervous system has 2 principle parts Central nervous system CNS brain and spinal cord 0 Receives processes stores and transfers information Peripheral nervous system PNS o Sensory division of PNS carries information to brain and spinal cord 0 Motor division of PNS carries information from CNS to other parts of the body I Somatic division controls skeletal muscles I Autonomic division controls smooth muscles cardiac muscles and glands Sympathetic Parasympathetic divisions oppose each other works antagonistically to accomplish homeostasis 112 Neurons are the communication cells of the nervous system Neurons specialized for communication generate and conduct electrical impulses action potentials from one part of your body to another 3 types of neurons 0 Sensory neurons part of PNS responds to a certain type of stimulus and transmits information about it to the CNS as impulses o Interneurons part of the CNS transmits impulses between components of the CNS 0 Motor neurons part of the PNS transmits impulses away from the CNS All neurons consist of a cell body an axon and dendrites 0 Cell body contains nucleus mitochondria and other organelles o Axon long slender tube of cell membrane containing cytoplasm conducts electrical impulses o Dendrites extensions of the cell body receive information from receptors 113 Neurons initiate action potentials The function of a neuron is to transmit information from one part of the body to another in the form of electrical impulses Sodiumpotassium pump controls cell volume by removing osmotic particles sodium ions from the cell 0 Transports 3 sodium ions out of the cell for every 2 potassium ions transported in Membrane potential small but measurable difference in voltage across the cell membrane 0 Resting potential normal membrane potential at rest 70 millivolts I The resting potential of a neuron undergoes a change when an impulse arrives from another neuron I Can depolarize membrane move the voltage closer to O I Or can hyperpolarize make it even more negative Graded potentials transient local changes in resting potential varies in size 0 Occur only at a single region on the membrane Summation when incoming signals from neurons add up in space and time Threshold a certain triggering membrane voltage Action potential sudden temporary reversal of the voltage difference across the cell membrane also known as an impulse occurs as a sequence of 3 events 0 Depolarization sodium moves into the axon o Repolarization potassium moves out of the axon o Reestablishment of the resting potential An action potential does not occur unless a certain threshold is triggered Action potentials are selfpropagating events continues to propagate itself in the next region of the axon 114 Neurological cells support and protect neurons Neurological cells cells in the nervous system that are not neurons provides physical support and protection to neurons and maintains healthy concentrations of chemicals in uids around them 0 Do not generate or transmit impulses Schwann cells specialized neurological cells in the PNS 0 Produce myelin fatty insulating material 0 Myelin sheath when Schwann cells create a shiny white protective layer around the axon myelinated neurons I Myelin sheath saves the neuron energy I Speeds up transmission of impulses I Helps damage or severed axons of the PNS regenerate In the CNS myelin sheaths are produced by another type of neurological cell called an oligodendrocyte o Degenerates once the axon is destroyed 0 Do not regenerate after injury Multiple sclerosis myelinated neurons in the brain and spinal cord become progressively damaged until they form hardened sclerotic scar tissue 0 Symptoms include muscle weakness visual impairment and urinary incontinence Amyotrophic lateral sclerosis sclerotic areas begin in regions of the spinal cord involved in motor control 0 Main symptom is progressive weakening and wasting of skeletal muscle tissue 115 Information is transferred from a neuron to its target Action potential causes the release of a chemical that crosses a specialized junction between the two cells called a synapse 0 Chemical substance is called a neurotransmitter because it transmits a signal from a neuron to its target 0 Entire process is called synaptic transmission Presynaptic membrane cell membrane of the neuron that is sending the information Postsynaptic membrane membrane of the cell that is about to receive the information Synaptic cleft small uidfilled gap that separates the presynaptic and postsynaptic membranes Each axon terminal of the presynaptic neuron ends in an axon bulb that contains neurotransmitters stored in membranebound vesicles Synaptic transmission follows a pattern 0 Action potential arrives at the axon bulb diffusing calcium into the bulb 0 Calcium causes the vesicles to fuse with presynaptic membrane and releases neurotransmitters into synaptic cleft o Neurotransmitters bind to receptors on postsynaptic membrane causing certain gated channels to open 0 Sodium ions diffuse inward producing a graded depolarization of the postsynaptic membrane in the area of the synapse Excitatory neurotransmitters depolarize postsynaptic cell causing threshold to be approached or exceeded Inhibitory neurotransmitters causes postsynaptic cell to hyperpolarize preventing the generation of action potentials Postsynaptic neurons integrate and process information 116 The PNS relays information between tissues and the CNS Nerve consists of the axons of many neurons all wrapped together in a protective sheath of connective tissue and all coming and going to the same place PNS contains cranial nerves and spinal nerves 0 Cranial nerves 12 pairs carries action potentials between the brain and muscles glands and receptors of the head neck thoracic and abdominal cavities o Spinal nerves 31 pairs connects with spinal cord from two short branches called the dorsal root and ventral root Sensory neurons provide information to the CNS Somatic division controls voluntary and involuntary skeletal muscle movement Spinal re exes involuntary responses that are mediated primarily by the spinal cord and spinal nerves with little or no involvement of the brain Autonomic division carries signals from the CNS to the periphery that control automatic functions of the body s internal organs 117 The brain and the spinal cord constitute the CNS Brain and spinal cord is where integrating processing of information occurs CNS is enclosed by 3 membranes of connective tissue called meninges 0 From outermost to innermost dura mater arachnoid pia mater Cerebrospinal uid fills the space between arachnoid and pia mater secreted from specialized capillaries into 4 ventricles in the brain Bloodbrain barrier functional barrier between blood and brain Spinal cord serves as the superhighway for action potentials traveling between the brain and the rest of the body 118 The brain processes and acts on information Brain command center of the body receives information in the form of action potentials from various nerves and the spinal cord integrates it and generates the appropriate response 3 divisions of the brain 0 Hindbrain coordinates basic automatic and vital tasks I Medulla oblongata controls automatic functions I Cerebellum coordinates basic movements I Pons aids information ow 0 Midbrain coordinates muscle groups and responses to sights and sounds o Forebrain receives and integrates sensory input from the external environment and determines most of our more complex behavior I Hypothalamus and thalamus maintain homeostasis and process information I Limbic system involved in emotions and memory I Cerebrum deals with higher functions language decision making conscious thought I Cerebral cortex outer layer of cerebrum 119 Brain activity continues during sleep Levels of sleep and wakefulness are controlled by the reticular activating system RAS a group of neurons in the reticular formation Electroencephalograms EEGs are recordings of the brain s electrical activity as measured at the body s surface 0 Stage 1 transitional phase between wakefulness and sleep pupils constrict breathing slows heart rate slows 0 Stage 2 Skeletal muscles relax eye and body movements cease Stage 3 Sleep deepens as heart rate and respiration slow even more 0 Stage 4 heart rate and respiration at their slowest body temperature falls 0 REM rapid eye movement when we dream heart rate respiration and blood ow to the brain increase 0 1110 The limbic system is the site of emotions and basic behaviors Limbic system all the neuronal structures that together control emotional behavior and motivational drives When different areas of the limbic system are stimulated we experience strong emotions such as fear anger sorrow or love 1111 Memory involves storing and retrieving information Memory involves storing information and retrieving it later as needed 0 Shortterm memory retrieves information stored within the last few hours 0 Longterm memory retrieves information days or years later 1112 Psychoactive drugs affect higher brain functions Psychoactive drugs affect states of consciousness emotions or behavior or the higher brain functions All psychoactive drugs are able to cross the bloodbrain barrier they work by in uencing the concentrations or actions of brain neurotransmitters o Dopamine neurotransmitter associated with pleasure Psychoactive drugs can lead to psychological dependence or craving the feelings associated with a drug and alter their behavior to obtain it 1113 Disorders of the nervous system Trauma o Concussion disrupts electrical activity of brain neurons 0 Spinal cord injuries impair sensation and function Infections o Encephalitis in ammation of the brain O O Meningitis in ammation of the meninges Rabies infectious Viral disease multiplies and kills brain cells Brain tumors abnormal growths O O Rising pressure disrupts normal brain function Some originate from the brain itself or seeded by cancer that spreads from other parts of the body Disorders of neural and synaptic transmission 0 O O Epilepsy recurring episodes of abnormal electrical activity Alzheimer s disease shortage of acetylcholine memory loss Parkinson s disease loss of dopaminereleasing neurons impairs ability to perform smooth coordinated motions
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