Week 12 Arterial Blood pressure & Heart sounds

Systole: ventricle contraction Diastole: ventricle relaxation Systole and diastole = one cardio cycle

BLOOD PRESSURE Blood pressure is defined as the pressure of the blood exerts against the blood vessel walls (arteries). The highest blood pressure that results from contraction of the ventricles of the heart is the systolic pressure the force of blood in your arteries as the heart contracts and pushes it out The lowest blood pressure that results from relaxation of the ventricles is the diastolic pressure the force of your blood between heartbeats A measurement of 130 / 85 reflects a systolic pressure of 130 and diastolic pressure of 85.

MEASURING BLOOD PRESSURE To measure blood pressure, place the blood pressure cuff, sphygmomanometer, and stethoscope as shown in the diagram. measured as the brachial artery compressed by a blood pressure cuff A stethoscope is used to hear sounds that result from the compression and release of pressure on the blood vessel. Pronounced (sfig’-mo-ma-nom-e-ter)

Blood pressure reading Place the cuff so that it just fits the arm, and is neither too tight nor too loose. Inflate the cuff so that the sphygmomanometer reads at least 160. You should not hear any sounds at this point. Slowly deflate the cuff, and note the reading when you begin to hear thumping/sharp tapping sounds through the stethoscope. This reading is the systolic pressure (the first sound of Korotkoff). Continue deflating the cuff until the thumping sound stops/muffles, and note the reading. This is the diastolic pressure (the second sound of Korotkoff). Finish deflating the cuff, and remove it from the arm. Wait ten minutes before attempting to take a second blood pressure reading on the same person.

Sounds of Korotkoff Sound is created by turbulent flow of blood through the compressed vessel Sound disappear when the vessel is no longer compressed by the pressure cuff and normal (non-turbulent) laminar flow resumes turbulent flow,   type of fluid (gas or liquid) flow in which the fluid undergoes irregular fluctuations, or mixing, in contrast to laminar flow, in which the fluid moves in smooth paths or layers. 

Factors that affect BP Genetics Age Body weight State of physical activity Level of salt, caffeine, or drugs

Closed circulatory system Arterial system is connected to the venous system by means of capillaries Allows for gas exchange to occur Pulmonary circulation: (Lungs) Pick up O2 and drop off CO2 Systemic circulation: (Tissues) Pick up CO2 and drop off O2

Relationship between flow, pressure & resistance F = P/R F = flow P = pressure R= resistance

Average rate of blood flow (pressure) Mean Arterial Pressure = pulse pressure + diastolic pressure 3 *Pulse Pressure= systolic pressure – diastolic pressure OR (systolic pressure + 2x diastolic pressure)

MAP 120mmHg 75mmHg

Heart sounds

Pathway of blood flow (from tissues) dO2 blood enters R. atrium via superior & inferior vena cava  tricuspid valve  R. ventricle  pulmonary semilunar valve  pulmonary (trunk) arteries  lungs  drop off dO2 blood & pick up O2 blood (from lungs) O2 blood enters L. atrium via pulmonary veins  bicuspid valve  L. ventricle  aortic semilunar valve  aorta  rest of the body

Auscultation areas using a stethoscope. SL valves: Aortic valve Pulmonary valve AV valves Tricuspid valve Bicuspid valve 14

Four major heart sounds Heart Sounds: “lub” and “dup” First Sound (S1): occurs during ventricular systole. Under low pressure, closure of the atrioventricular (AV) valves and opening of the semilunar (SL) valves  “lup” Second Sound (S2): occurs during ventricular diastole. Under high pressure, closure of the SL valves and opening of the AV valves  “dup” Third Sound (S3): turbulence associated with rapid filling of the ventricles shortly after opening of the AV valves Forth Sound (S4): turbulence associated with the passage of blood from the atria into the ventricles during atrial systole

Ventricles Diastole: the period of ventricular filling (relaxation), the AV valve open; SL valves are closed to prevent arterial blood from re-entering the heart Systole: when the ventricles contract & compress the blood in their chambers, closes the AV valves (prevents backflow into atria); SL valves are forced open as the ventricles discharge the blood into the large arteries

Phases of the Cardiac Cycle Fig. 12-18 on p 374 End-Diastolic Volume Isovolumetric contraction rising atrial pressure pushes blood into the ventricle ATRIAL SYSTOLE the end-diastolic volume (EDV) of blood is in the ventricles ATRIAL DIASTOLE / VENTRICAL SYSTOLE Isovolumetric contraction of the ventricles: ventricles are contracting but there is no blood flow Ventricular pressure increases forcing blood through the semilunar valves VENTRICAL DIASTOLE the end-systolic volume (ESV) of blood is in the ventricles The period of isovolumetric relaxation when all heart valves are closed Atrial pressure forces the AV valves open Isovolumetric relaxation End-Systolic Volume Stroke Volume

Fig. 12-19 (a) Atrial contraction begins (S4) Atria eject blood into ventricles (b) Atrial systole ends; AV valves close (S1) (c) ventricular contraction (d) Ventricular ejection occurs Semilunar valves close (S2) (e) relaxation occurs (f) AV valves open; passive ventricular filling occurs (S3)

stroke volume (SV) is the volume of blood pumped from one ventricle of the heart with each beat