BIOL 244 1nd Edition Lecture 8 Outline of Last Lecture I Valves of the Heart II Cardiac Cycle III Cardiac Muscle Fibers IV Cardiac Muscle Contraction V Self excitable Cardiac Cells VI Autonomic Innervation of the Heart VII Electrocardiogram VIII Heartbeat Outline of Current Lecture I Cardiac Output II Regulation of Cardiac Output III Sympathetic and Parasympathetic Nervous System Regulation of CO IV Factors that influence Cardiac Output V Three Main Types of Blood Vessels VI Structure of Blood Vessels Current Lecture I Cardiac Output a Amount of blood pumped out by each ventricle in one minute b Usually measure in mL minute c Determined by stroke volume SV and heart rate HR These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute i CO SV HR ii Heart rate beats minute iii Stroke volume mL beat 1 Amount of blood ejected from the ventricles when they contract how much blood is pushed out of the heart in one heartbeat d Sufficient cardiac volume necessary for blood volume and blood pressure i Drop in cardiac output can be compensated for by increase in stroke volume ii Drop in cardiac output can be compensated for by increase in heart rate e S EDV ESV i EDV end diastolic volume ii ESV end systolic volume f 3 major mechanisms that affect SV i Preload 1 Adjusted in body under normal circumstances from minute to minute 2 Degree to which cardiac muscle is already stretched before it contracts before systole a Amount of blood in ventricles determine the degree to which the muscle is stretched b Looking for optimal amount of overlap between thin and thick filaments to lead to the maximum amount of cross bridges to have the maximum possible contraction 3 Greater EDV will increase preload and increase the contraction a Will increase SV ii Contractility 1 Adjusted in body under normal circumstances from minute to minute 2 The strength of the contraction at a given muscle length a Manipulated by adjusting the amount of calcium that s available within the cardiac muscle fibers i Increase in calcium leads to increased cross bridge formation ii Decrease in calcium leads to decreased crossbridge formation 3 Increase in contractility leads to decrease in ESV a Will increase SV iii Afterload 1 Factor for people with abnormally high blood pressure 2 The amount of pressure present in the great vessels exiting the vesicles a Pressure within pulmonary trunk aorta 3 Tends to reduce stroke volume II Regulation of Cardiac Output a Increasing venous return amount of blood being returned to the heart i Exercising 1 Using the skeletal pump 2 As skeletal muscles contract veins are squeezed forces blood back to the heart 3 The more vigorously you move the more this is happening 4 Rate of breathing increases changes the volume of thoracic cavity ii Slow heart rate 1 Heart is beating more slowly 2 More time for ventricle to fill in diastole longer iii Increasing contractility 1 Epinephrine thyroxine b Increase heart rate i Increase in sympathetic activity ii Decrease in parasympathetic activity III Sympathetic and Parasympathetic Nervous System Regulation of CO a Sympathetic i Sympathetic fibers release norepinephrine at SA and AV nodes 1 Increase the frequency with which cells depolarize 2 Increase rate of action potentials spreading across heart ii Increases heart rate beyond 75 beats per minute iii Stimulate cardiac muscle fibers more directly 1 Enhance movement of calcium into muscle fibers a Elevates contractility b Parasympathetic i Parasympathetic fibers release acetylcholine 1 Causes hyperpolarization of cells in the SA and AV node 2 Rate of contraction of muscle decreases IV Factors that influence Cardiac Output a Age i Surface area volume ratio ii Smaller individual will have faster heart rate than individuals that are larger children vs adults men vs women b Sex i Males tend to have slower heart rate than females 1 Males are about 5 bigger than females on average c Exercise i As you move more your heart rate is elevated d Temperature i Heart beats faster at higher temperatures than at lower temperatures e Various hormones THIS IS THE END OF INFORMATION FOR EXAM 1 V Three Main Types of Blood Vessels a Arteries i Blood vessels that carry blood away from the heart ii Systemic circuit oxygenated blood iii Pulmonary circuit deoxygenated blood iv Examples aorta pulmonary trunk b Capillaries i Smallest blood vessels in body ii Gas nutrient and waste product exchange 1 Offload oxygen to all tissue cells 2 Take up carbon dioxide and waste products iii In lungs offload carbon dioxide and pick up oxygen c Veins i Blood vessels that carry blood towards the heart VI Structure of Blood Vessels a Central Lumen i Central space that is filled with blood 1 Can be adjusted b Blood vessel wall i Surrounds lumen ii Has several layers tunics 1 Tunica intima a Innermost layer b Endothelium epithelial tissue innermost i Squamous epithelial cells ii Continuous throughout blood vessels c Subendothelial layer middle i Not present in the smallest blood vessels ii Surrounds endothelium iii Made up of non cellular molecules d Internal elastic lamina outermost i Not in all vessels ii Provides structural support and elasticity 2 Tunica media a Smooth muscle b Arranged circularly around the circumference of the blood vessels c When muscle cells within tunica media contract blood vessels get more narrow make lumen smaller i Vasoconstriction d When muscle cells within tunica media relax blood vessel diameter gets bigger i Vasodilation e Layer of elastic fibers i Elastic lamina ii Provides structural support and elasticity 3 Tunica externa a Made up of collagen fibers i Tough connective tissue b Vasa vasorum i Blood vessels within the tunica externa itself