bio 2313, exam II study guide
bio 2313, exam II study guide Biology 2313
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This 15 page Study Guide was uploaded by Aylin Sanchez on Wednesday October 12, 2016. The Study Guide belongs to Biology 2313 at University of Texas at El Paso taught by Dr. Zaineb Al-Dahwi in Fall 2016. Since its upload, it has received 70 views. For similar materials see Human Anatomy & Physiology II in Anatomy and Physiology at University of Texas at El Paso.
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Date Created: 10/12/16
Anatomy and Physiology II: Exam II Chapter 18- The Cardiovascular System: The Heart 18.1 Heart Cone-shaped organ Located posterior to the sternum and anterior to the vertebral column Apex: Points inferior towards the left hip Apical pulse: cause by beating heart’s apex where it touches the chest wall Pericardium: Double-walled sac Loosely fitting superficial part of sac is the fibrous pericardium o Tough, dense connective tissue o Protects the heart o Anchors to surrounding structures o Prevents overfilling of the heart with blood Deep into the fibrous pericardium is the serous pericardium o Thin, slippery, 2-layer serous membrane forms closed sac around heart o Parietal layer lines the internal surface of the fibrous pericardium (outer layer of serous pericardium) o External heart surface visceral pericardium aka epicardium In between the parietal and visceral layers is a pericardial cavity Myocardium middle layer, composed of cardiac muscle cells not all are contractile modified do not contract 98-99% cardiac cells are contractile pacemakers 1% Cardiac muscle cells usually arranged in bundles arranged in a circular fashion Connected by connective tissue fibers- link cells and bundles together Fibrous cardiac skeleton fibrous connective tissue thicker in areas such as: around heart valves (because of blood pulsation) and around bases of large arteries Poor conductors of electrical impulse connective tissue Endocardium Sheet of endothelium simple squamous epithelial cells Inner most layer of wall of the heart Continuous with the endothelial linings of the blood vessels leaving and entering the heart 4 chambers- 2 superior atria and 2 inferior ventricles Interatrial septum internal partition that divides the heart longitudinally (where it separates the atria) Interventricular septum where it separates the ventricles Atria o receiving chambers for blood returning to the heart from the circulation (atrium = entryway) o Small, thin-walled only contract minimum to push blood to ventricles Ventricles o discharging chambers actual pumps of the heart o much larger walls than the atria o when they contract they push blood out to the circulation Right atrium o smooth posterior inside wall o Anterior: bundles of muscle tissue form ridges in the walls called pectinate muscles (look like the teeth of a comb & absent in left atrium) o The posterior and anterior regions of the right atrium are separated by C-shaped ridge crista terminalis Blood entryway to right atrium o Superior vena cava- collects blood from regions above the diaphragm o Inferior vena cava- collects blood from regions below the diaphragm o Coronary sinuses- collects blood draining from the myocardium Left atrium o Mostly smooth pectinate muscles only found in the auricle o Interatrial septum has a shallow depression fossa ovalis marks the spot where an opening foramen ovale existed in the fetal heart Blood entryway to left atrium o Pulmonary veins (4) transport blood from the lungs back to the heart Right ventricle o Pumps blood into the pulmonary trunk, guides blood to the lungs where gas exchange occurs Left ventricle o Ejects blood into the aorta largest artery in the body o Myocardium about 3x thicker Muscle that lines walls of the ventricular chambers trabeculae carneae Muscles involved in valve function are papillary muscles Chord-like structures- chordae temdima collagen fibers 18.2 Two atrioventricular (AV) valves o one located in each atrial-ventricular junction o Prevent backflow into atria when ventricles contract Right AV valve o tricuspid valve- 3 cusps Left AV valve o mitral valve- 2 cusps aka bicuspid valve Collagen cords that that attach the cusps to the papillary muscle are called chordae tendineae Semilunar (SL) Valves o Aortic and pulmonary valves guard bases of the larger arteries (aorta largest artery in the body and pulmonary trunk take blood to lungs) & prevent backflow into ventricles Open and close in response to differences in pressure When the interventricular pressure rises above the pressure in the aorta & pulmonary trunk, the SL valves force open and cusps against the walls, blood rushes There is no valves guarding the venae cavae and pulmonary veins into rt. & lt. atria = some blood goes back into vessel during atrial contraction (backflow is minimal) 18.3 Superior vena cava, inferior vena cava, coronary sinus right atrium right ventricle pulmonary trunk to lungs heart 4 pulmonary veins left atrium left ventricle aorta to body to heart Blue is oxygen-poor blood Red is oxygen-rich blood Pulmonary circulation- o right side of the heart o blood vessels to and from the lungs o Short, low resistance, low pressure o Right ventricular cavity, flattened- crescent shape Systemic circulation- o left side of the heart o blood vessels to systemic back to heart o long path, high resistance, high pressure o walls of lt. ventricle thicker than the right & cavity is almost circular o generates more pressure, more powerful Direction of blood flow- due to the valves they prevent backflow Atrium valve ventricle artery Pressure= driving force 18.4 Microscopic anatomy Cardiac muscle- o Similar to bone cells striated & arrangement – perfect alignment of I & A band in the myofibril contracts by the sliding of actin and myesin o differences skeletal muscle extremely long & cardiac is much shorter cell cardiac branches of cells, skeletal non-branching cardiac single nucleus, skeletal multi-nucleus cardiac is interdependent, skeletal is independent intercalated discs connect cardiac muscle cells cardiac muscle cells o myocytes (2 types)- 1 type is contractile and self- excitable o cardiac pacemakers cells- 2 type non-contractile spontaneously depolarize autorhythmicity, automaticity self-excitable heart contracts as a unit o contraction of all myocytes= effective pumping of heart tetanic contraction cannot occur in cardiac muscles o absolute refractory period period during an action potential when another action potential cannot be triggered o to prevent tetanic contractions the absolute refractory period is almost as long as the contraction o contraction Repolarization relaxation the heart relies almost only on aerobic respiration so it cannot work without oxygen for long 18.5 the activity of the heart is a function of (1) the presence of gap junctions and (2) the activity of the heart’s conduction system o intrinsic cardiac conduction system non- contractile cardiac cells special to initiate & distribute impulses in the heart pacemakers are part of this system- have unstable resting potential that continuously depolarize pacemakers potential, prepotentials; initiate action potentials that cause rhythmic contractions in the heart pacemaker potential o special properties of ion channels in sarcolemma depolarization o at threshold, Ca+ channels open repolarization o Ca+ channels inactive Sequence of excitation o Cardiac pacem o aker cells found in sinoatrial and atrioventricular nodes 1-sinoatrial (SA) node: located right atrial wall, typically generates impulses 75x every minute, set pace for the rest of heart because no other region depolarizes as fast or faster heart’s pacemaker, w. sinus rhythm= determines heart rate 2-Atrioventricular (AV) node: Impulse is delayed, allowing atria to respond and complete contractions before atria contracts, conducts impulses the slowest in the system 3- Atrioventricular (AV) bundle: Only electrical connection between the atria and ventricles Firbrous cardiac skeleton is nonconducting and insulates the rest of the AV junction 4- Right & left bundle branches Bundle splits into the right and left bundles 5- Subendocardial conducting network Aka purkinje fibers Completes pathway through interventricular septum Cardioacceleratory center o Projects sympathetic neurons in t1-t5 level of spinal cord Cardioinhibitory center o Sends impulses to the parasympathetic nucleus in the medulla impulses to heart Electrocardiography o ECG- graphic record of heart activity o Composite of all action potentials generated by nodal & contractile cells at a given time o 3 waves- P, QRS, & T P wave: lasts about 0.08s, results from movement of depolarization wave from SA node through atria QRS complex: ventricular depolarization ventricular contraction, produces corresponding changes in current direction T wave: caused by ventricular repolarization, repolarization is slower than depolarization, t wave Is spread out with a lower amplitude than QRS P-R interval is time from beginning of atrial excitation to the beginning of ventricular excitation. When visible the Q wave marks beginning ventricular excitation aka P-Q interval. S-T segment- action potentials of myocytes are in plateau phases, myocardium depolarized Q-T interval- beginning of ventricular depolarization through ventricular repolarization 18.6 Cardiac Cycle Systole: period of contraction Diastole: period of relaxation Cardiac cycle: all events associated with blood flow through heart in one complete heart beat atrial systole & diastole followed by ventricular systole and diastole o Marked by succession of pressure and blood volume changes Ventricular filling: mid-to-late diastole: pressure low, blood passing atria and open AV valve, ventricles and aortic and pulmonary valves closed, following depolarization (P wave) atria contract, slight rise in atrial pressure residual blood from atria to ventricles, last part of diastole, maximum volume they will contain in cycle end diastolic volume atria relax and the ventricles depolarize (QRS) atrial diastole Ventricular systole: atria relax, ventricles contract, ventricular pressure rises closing AV valves. Isovolumetric contraction second between when the ventricles are completely closed and when the blood volume in chambers remains constant as the ventricles contract. When pressure exceeds the large arteries, the isovolumetric stage ends. Isovolumetric relaxation: (early diastole) brief period following the T wave ventricles relax, ESV is no longer compressed, pressure drops & blood from aorta and pulmonary truck goes back to the heart closes SL valves Blood flow through the heart is completely controlled by pressure changes and blood flows through pressure gradient through any opening Pulmonary artery systolic and diastolic 24 and 10 mm Hg Aorta systolic and diastolic pressure of 120 and 80 mm Hg Both eject same blood volume with each heartbeat 18.7 Cardiac output (CO) o Amount blood pumped out by each ventricle in 1 min o Product of heart rate (HR) and stroke volume (SV)CO = HR x SV o CO varies directly with HR and SV o CO increases when SV increases or HR increases or both ( it decreases when one or both decrease) o Cardiac reserve difference between resting and maximal CO Stroke volume o Volume of blood pumped out by 1 ventricle with each beat o Normal adult volume 5L o Represents difference between end diastolic volume (EDV), amount blood collects in ventricle during diastole and end systolic volume (ESV) the volume blood remaining in ventricle after contraction SV= EDV-ESV Preload- degree at which cardiac muscle cells are stretched before they contract controls SV o Higher preload, higher SV o Relationship between SV and preload Frank Starling law of heart o Venous return amount of blood returning to the heart and distending its ventricles o Increase in venous return increase EDV increase SV increases CO Contractility o Contractility is contractile strength achieved at a given muscle length o Extrinsic factors increase heart muscle contractility can increase SV o Substances that increase contractility positive inotropic agents such as 2+ epinephrine, thyroxine, and glucagon, drug digitalis and high levels of Ca + o Negative inotropic agents decrease contractility such as acidosis, extracellular K levels and drugs called Ca channel blockers Afterload pressure the ventricles have to overcome to eject blood Regulation of the Heart o Factors that increase HR are called positive chronotropic o Factors that decrease HR are negative chronotropic factors Autonomic nervous system has the extrinsic controls affecting HR Stressors activate sympathetic nervous system- nerve fibers release norepinephrine @cardiac synapses- binds to beta 1 adrenergic receptors causing quicker threshold SA fires rapidly, increasing HR Enhanced contractility lowers ESV, SV does not lower if only HR increased Other factors that regulate HR o Age, gender, exercise, body temperature o Less important that neural factors 19- Introduction Blood vessels- arteries, capillaries, & veins Arteries o Carry blood away from the heart o Branch into smaller divisions o Sympathetic circulation always carry oxygenated blood Veins o Carry blood toward the heart o Join and merge into larger vessels approaching the heart o Sympathetic circulation always carry oxygen poor blood 19.1 Vessel lumen- surround a central blood-containing space Innermost tunic is the tunica intima o Endothelium simple squamous epithelial that lines lumen of all vessels Middle tunic- tunica media o Circularly arranged smooth muscle cells and sheets of elastin o Small changes in vessel diameter greatly influence blood flow and blood pressure o Bulkiest layer in arteries Vasoconstriction- lumen diameter decreases as lumen contracts Vasodilation- lumen diameter increases as smooth muscle contracts Outermost layer of blood vessel wall Tunica externa o Composed of loose collagen fibers protect and reinforce and anchor to surroundings o Larger vessels contain vasa vasorum- vessels of the vessels 19.2 Elastic arteries thick-walled arteries near the heart o Aorta & major branches o Large lumens low resistance pathways o Contain more elastin than any other vessel type o In all 3 tunics- but tunica media the most o Pressure reservoirs Muscular Arteries o Blood to specific organs o Thickest tunica media vessels o More smooth muscle, less elastin Arterioles o Smallest of the arteries o Arteriolar diameter- varies in response to changing neural, hormonal, local chemical influences Changing diameter changes resistance called resistance vessels
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