12.2 Monitoring the Human Circulatory System

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1 12.2 Monitoring the Human Circulatory System Video 1: 3D Animation of Heart Pumping Blood blood flow through the heart... Video 2: Hank Reviews Everything on the Heart 1

A) Control of Heartbeat The impulse that triggers the heartbeat comes from within the heart itself (not the brain) The sinoatrial node (SA node), found in the wall of the Right Atrium, is a bundle of

As atria contract, the impulse reaches another node called the atrioventricular node (AV node) This node, located between the ventricles, transmits an electrical signal through a bundle of

2 A) Control of Heartbeat The impulse that triggers the heartbeat comes from within the heart itself (not the brain) The sinoatrial node (SA node), found in the wall of the Right Atrium, is a bundle of muscle tissues that stimulates the muscle fibres to contract and relax rhythmically SA node is commonly called the pacemaker SA node sends electrical impulses causing atria to contract simultaneously As atria contract, the impulse reaches another node called the atrioventricular node (AV node) This node, located between the ventricles, transmits an electrical signal through a bundle of specialized fibres called the bundle of His These fibres relay the signal through two branches of bundles that divide into fast conducting Purkinje fibres The Purkinje fibres initiate the almost simultaneous contraction of both ventricles 2

In 1893, he discovered the bundle of His the specialized tissue in the heart that transmits the electrical impulses and

3 text p489 SA Node AV Node bundle of His Purkinje fibres Purkinje fibres Why is it called the "bundle of His"? "Wilhelm His Jr. ( ) was a Swiss born cardiologist and anatomist. In 1893, he discovered the bundle of His the specialized tissue in the heart that transmits the electrical impulses and helps synchronize contraction." Why is it called the "Purkinje fibres"? "Named after Jan Evangelista Purkinje (Czech Purkyně) ( ), Czech physiologist, who discovered the fibers in 1839." 3

4 Electrical signals transmission: SA node AV node 4

Ch 12.2 Monitoring the Human Circulatory System.

referred to as "lub DUB, lub DUB" Two sounds are heard as different heart valves close The first heart sound is the closing of the AV valves, as

the arteries An electrocardiogram, or ECG is used to record the electrical impulses generated by a beating heart Electrodes are placed on the skin

5 Ch 12.2 Monitoring the Human Circulatory System.notebook B) Hearing & Measuring Heartbeat A stethoscope is used to listen to the heart beat Normal heart sound is a repeated double beat, commonly referred to as "lub DUB, lub DUB" Two sounds are heard as different heart valves close The first heart sound is the closing of the AV valves, as blood is pumped from the atria to the ventricles The second sound is closing of the semilunar valves, as blood is pumped from the ventricles into the arteries An electrocardiogram, or ECG is used to record the electrical impulses generated by a beating heart Electrodes are placed on the skin of the chest The electrodes record voltage changes (only a few millivolts) produced by nerve signals that control the heartbeat Doctors can determine whether a person's heart is generating signals with a normal frequency, strength, and duration text p490 5

R T P contraction of atria (atrial depolarization) P Q S Q S contraction of ventricles (ventricular depolarization) T ventricle relaxes from contraction (precedes the next firing of the SA node)

6 R T P contraction of atria (atrial depolarization) P Q S Q S contraction of ventricles (ventricular depolarization) T ventricle relaxes from contraction (precedes the next firing of the SA node) (ventricular repolarization) Noradrenaline (epinephrine) increases the firing of the SA node, while acetylcholine (Ach) slows it down During periods of physical activity, the brain releases noradrenaline, which stimulates the SA node This increase in blood pressure fuels your activity, but causes the brain to release Ach to slow down the firing of the SA node 6

B) Measuring Blood Pressure Healthy blood pressure: 120 mm Hg 80 mm Hg Video 3: What do the numbers represent? https://www.youtube.com/watch?

7 B) Measuring Blood Pressure Healthy blood pressure: 120 mm Hg 80 mm Hg Video 3: What do the numbers represent? A sphygmomanometer, or blood pressure cuff, is used to measure blood pressure of an artery in the arm A blood pressure reading shows how much pressure the blood exerts against the vessel walls and indicates the condition of the heart and arteries As the cuff is inflated and exerts pressure on the arm, blood flow temporarily stops; then as air is slowly released out of the cuff, the blood begins to flow again and the pressure of the blood against the walls of the artery in the arm is measured Video 4: What is Blood Pressure? U 7

8 Blood pressure consists of two measurements: Systolic Pressure highest pressure in the cardiac cycle; generated by the contraction of the ventricles sending blood to pulmonary arteries and aorta 120 mm Hg Diastolic Pressure lowest pressure in the cardiac cycle; when the ventricles relax and the pressure drops (occurs immediately before another contraction of the ventricles) 80 mm Hg Video 5: Systole & Diastole Explained 8

9 C) Cardiac Output & Stroke Volume Cardiac output a measure of the volume of blood pumped out by the heart per unit time (ml/min) Therefore, is also an indicator of the level of O 2 delivery to body Cardiac output is affected by two factors: heart rate and stroke volume Heart Rate number of heartbeats per minute Stroke volume amount of blood forced out of heart with each heartbeat Cardiac output = heart rate x stroke volume 9

10 Stroke volume is determined by two factors: How easily heart fills with blood (related to volume of blood returning to the heart from veins and the distensibility or stretchiness of ventricles) How easily the blood empties from the heart (related to strength of ventricular contraction and the pressure exerted by artery walls) Video 6: Humber College Prof (Uni of Guelph) explains Cardiac Output & Stroke Volume 10

Cardiovascular fitness is the capacity of the heart, lungs, and blood vessels to deliver oxygen to working muscle tissues so that they can maintain prolonged phsical work

only thickens ventricle walls, which could limit stroke volume by reducing the elasticity of the ventricles A good indicator of cardiovascular fitness is the length of

11 Cardiovascular fitness is the capacity of the heart, lungs, and blood vessels to deliver oxygen to working muscle tissues so that they can maintain prolonged phsical work Cardio exercise enlarges the ventricles, increases their elasticity, and strengthens their walls together, these changes increase stroke volume Strength training alone only thickens ventricle walls, which could limit stroke volume by reducing the elasticity of the ventricles A good indicator of cardiovascular fitness is the length of time it takes the heart to recover to its resting heart rate after strenuous exercise the more fit the heart is, the shorter the time it takes to return to resting heart rate 11

12 Ch 12.2 Monitoring the Human Circulatory System.notebook Let's have some fun! Try this activity... "Sphygmomanometer What's your blood pressure?" Sit down and relax... :) Video 7: Steps in Using a Sphygmomanometer 12

13 Review & Learning Check Read p Answer Q's 1 7,9 p493 13

The Mammalian Circulatory System

The Mammalian Heart The Mammalian Circulatory System Recall: What are the 3 cycles of the mammalian circulatory system? What are their functions? What are the three main vessel types in the mammalian circulatory