PHIS 206 1st EditionLecture 12Outline of Last Lecture I. Muscle Mechanics―Skeletal MusclesII. Smooth MusclesIII. Cardiac MusclesIV. Atrial and VentricularV. Mechanism of Stimulation―Cardiac MuscleVI. Cardiac CycleOutline of Current Lecture I. How The Blood Works―MechanicalII. How The Blood Works―Blood Flow III. External Factors that Modify Cardiac OutputIV. Electrical Properties of the Heart V. Conductive FibersCurrent LectureI. How The Blood Works―Mechanical-Blood is a fluid Fluids always flow downhill (high to low pressure)-Heart valves: only 1 way valves Valves will open when pressure pushing in is greater than pressure pushing back From pulmonary, it goes down Left Atrial, and down Left Ventricular to systemic From systemic, it goes down Right Atrial, and down Right Ventricular to pulmonary-Systole: heart contracting-Diastole: heart relaxing soon will be 0 mmHg heart fills passively; expands where heart is closed in membrane at the end: heart begins to contract (1st : atrial contracts)o 70% of volume that enters ventricles before atrial contractso Ventricular (thicker + stronger) begins to contract exceeds atrial pressure, so valve b/w a+v get pushed up-Period of isometric contraction: volume stays same, only pressure is increased by ventricles-As LV reaches 80 mmHg, valve opens and blood flows from LV to aorta -Period of ejection: blood is being ejected from ventriclesThese 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. from time of 80 mmHg to ≈ 120 mmHg heart begins to relax (0 mmHg) and back to diastoleo happens EVERY second!-End-Systolic ≈ 50 mL-End-Diastolic ≈ 125 mL-Stroke 75 mL-Normal Cardiac Output = 5 L/minute 5 L in left will soon go to 5 L in rightII. How The Blood Works―Blood Flow -Starling Law of Heart: harder; you heart ejects in stroke = heart entering in diastole Summary: cardiac output = return Length/Tension relationship gives heart the unique property of having input = output III. External Factors that Modify Cardiac Output-Parasympathetic: decreases heart activity/output-Sympathetic: increases heart activity/output*Sterling’s Law is an INTERNAL factor!-Autoregulation: if you exercise a muscle, O2 increases, arterials dilate smooth muscle relaxes when O2 increaseso blood flows through o Venus return increases, so heart pumps extra volumeIV. Electrical Properties of the Heart -Since the stroke volume = difference b/w end systole and end diastole, the heart gains efficiency if there is a time when every cell simultaneously relaxes or contracts-Excitation every piece of heart muscle can spontaneously depolarize/contract Fastest contraction: S-A Node S-A Node: depolarize with highest frequency spontaneously than any other heartcell Atrium: have simultaneous relaxation/contraction; will stay that way until 1st cell that generated the action potential goes back to relaxationo cells are in the S-A NodeV. Conductive Fibers-carry action potentials from atria to ventricles, since they cannot directly transfer to each other-What happens in atria occurs in ventricles, but only timing is
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