Who can put their washing out fastest? Peg up and place the cards in the right order – table vs table EXTENSION – name as many differences between right and left ventricle?

Learning Outcomes Compare the left and right ventricles Calculate cardiac output and compare output in different situations Identify the three stages in a heart beat

Left vs. Right Ventricle DESTINATION  The left ventricle and the right ventricle pump out blood from the heart going to the arteries to supply blood to the different parts of the body. BLOOD  The left ventricle receives oxygenated (oxygen-rich) blood and pumps it out to most of the systems in the body while the right ventricle receives deoxygenated (oxygen-poor) blood from the right atrium. EFFORT  There is also a difference between the effort exerted by the left and right ventricles. STRUCTURAL  Left ventricle is actually thicker than that of the right ventricle as the person reaches his teenage to adult years due to exertion requirements MISCONCEPTION!! No difference in volume pumped! The left and right ventricles pump the same volume of blood through the aorta and pulmonary artery.

Glossary Terms Heart Rate (pulse) (HR) Number of heartbeats that occurs per minute. Stroke Volume (SV) Volume of blood expelled by each ventricle on contraction. The stronger the contraction, the greater the stroke volume. Cardiac Output (CO) Volume of blood pumped out of the ventricle per minute. of the heart (creates the pulse) CO = HR x SV

Cardiac output = pulse rate x stroke volume 1.What is the cardiac output when oxygen uptake is litres per minute is the cardiac output with the stroke volume was 130, calculate the what is the oxygen uptake?

What way does blood pass through the heart? Why? What is causing that order? Hint – what moves blood around the body? What moves it back towards the heart?

Cardiac Cycle Name of the pattern of contraction (systole) and relaxation (diastole) in one complete heartbeat. DIASTOLE During diastole blood returning to the atria flows into the ventricles. In diastole the higher pressure in the arteries closes the SL valves

Cardiac Cycle ATRIAL SYSTOLE Atrial systole transfers the remainder of the blood through the atrioventricular (AV) valves to the ventricles. VENTRICULAR SYSTOLE Ventricular systole closes the AV valves and pumps the blood out through the semi lunar (SL) valves to the aorta and pulmonary artery.

Diastole Atrial systole Ventricular systole

Cardiac Cycle The opening and closing of the AV and SL valves are responsible for the heart sounds heard with a stethoscope.

A Atrioventricular (bicuspid / mitral) valve(s) closes (“snaps shut”– makes 1 st louder heart sound “LUB” B Semilunar valve(s) (aortic valve) opens C Semilunar valve(s) closes – makes second softer heart sound “DUB”- shut due to blood accumulating in their pockets D Atriioventricular (bicuspid) valve(s) opens “LUB” “DUB” Atrial Systole Ventricular Systole Diastole Cardiac cycle = 0.8 sec 60/0.8 bpm = 72 bpm

Glossary Definitions The chambers of the heart alternatively contract = SYSTOLE The chambers relax = DIASTOLE One complete sequence of filling and pumping blood = CARDIAC CYCLE During SYSTOLE, cardiac muscle contracts and the heart pumps blood. During DIASTOLE, the cardiac muscle relaxes and the chambers fill with blood.

So what causes the contraction?

Cardiac Conduction The heart beat originates in the heart itself, it is myogenic. However regulated by both nervous and hormonal control. Rate of contraction of cardiac by the autorhythmic cells of the sinoatrial node (SAN) or pacemaker

Cardiac Conduction The timing of cardiac cells contracting is controlled by the impulse from the SAN spreading through the atria and then travelling to the atrioventricular node (AVN) and then through the Bundle of His and Purkyne tissue to the ventricles.

Cardiac Conduction The timing of cardiac cells contracting is controlled by the impulse from the SAN spreading through the atria and then travelling to the atrioventricular node (AVN) and then through the ventricles. These impulses generate currents that can be detected by an electrocardiogram (ECG).

Electrocardiogram (ECG) P wave = electrical activity during atrial systole QRS complex = electrical activity during ventricular systole T wave = ventricular repolarisation (recovery of ventricular walls) Q-T interval – contraction time (ventricles contracting) T-P interval – filling time – ventricles relaxed and filling with blood Pattern are studied in different conditions and compared to the standard ECG in order to diagnose heart conditions, such as arrythmias and fibrillation. Fibrillation is stopped by passing a strong electric current through the chest wall – the heart stops for up to 5 seconds after which it begins to beat in a controlled way Electrodes are placed on the skin over opposite sides of the heart, and the electrical potentials generated recorded with time. The result is an ECG.

A normal ECG trace compared with others indicating an unhealthy heart During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm. A heartbeat that is too fast is called tachycardia. A heartbeat that is too slow is called bradycardia. Atrial flutter

SUMMARY Regulation of the Heart Atria relaxed – fill with blood RA with deoxygenated blood from vena cava LA with oxygenated blood from pulm vein SAN sends out 72 impulses/min over atrial wall – atria contract 72 times/min Atria contract to force blood into ventricles Atria relax Impulse reaches AVN Delayed momentarily Impulse travels through nerve fibres of the atrioventricular bundle and its branches into walls of the ventricles Ventricles contract – from apex upwards to force blood into arteries Oxygenated blood from LV to aorta – to body Deoxygenated blood from RV to pulmonary artery – to lungs (to be oxygenated)

Nervous Regulation of SAN The medulla regulates the rate of the SAN through the antagonistic (working oppositely - both increase and decrease – for fine control similar to a car with a brake and accelerator) action of the autonomic nervous system (ANS) (involuntary control – however some can be controlled).

Nervous Regulation of SAN Sympathetic accelerator nerves release adrenaline (epinephrine) and slowing parasympathetic nerves release acetylcholine. Actual rate is determined by which system exerts greatest influence at the time.

Hormonal Regulation of SAN If stressed or during exercise the sympathetic nervous system acts on the adrenal glands, causing the release of adrenalin which increases the heart rate.

Demonstration Place the cards into the correct category

Review The cardiac cycle is initiated and controlled by the heart itself. Cardiac muscle is said to be since it will contract and relax of its own accord. The beat is initiated by the which is situated in the wall of the Waves of depolarisation travel through the atria causing atrial The waves of depolarisation can only travel to the ventricles via the situated at the top of the ventricular septum. From here the waves travel to the apex of the heart through the which is made of specialised conducting cells called These then carry the waves of depolarisation through the ventricle walls causing both ventricles to contract simultaneously. At this stage the are open and the are shut so that blood can be forced into the arches.

Review The cardiac cycle is initiated and controlled by the heart itself. Cardiac muscle is said to be..myogenic... since it will contract and relax of its own accord. The beat is initiated by the.sinoatrial node (SAN).which is situated in the wall of the.right atrium.... Waves of depolarisation travel through the atria causing atrial.systole.. The waves of depolarisation can only travel to the ventricles via the..atroventricular node (AVN).. situated at the top of the ventricular septum. From here the waves travel to the apex of the heart through the.. bundle of His... which is made of specialised conducting cells called.. Pukinje fibres..These then carry the waves of depolarisation through the ventricle walls causing both ventricles to contract simultaneously. At this stage the...semilunar valve.. are open and the...atrioventricular valves... are shut so that blood can be forced into the arches.

Cardiac Conduction The heart beat originates in the heart itself but is regulated by both nervous and hormonal control. The autorhythmic cells of the sinoatrial node (SAN) or pacemaker set the rate at which cardiac muscle cells contract. The timing of cardiac cells contracting is controlled by the impulse from the SAN spreading through the atria and then travelling to the atrioventricular node (AVN) and then through the ventricles. These impulses generate currents that can be detected by an electrocardiogram (ECG).

Cardiac Cycle Name of the pattern of contraction (systole) and relaxation (diastole) in one complete heartbeat. During diastole blood returning to the atria flows into the ventricles. In diastole the higher pressure in the arteries closes the SL valves Atrial systole transfers the remainder of the blood through the atrioventricular (AV) valves to the ventricles. Ventricular systole closes the AV valves and pumps the blood out through the semi lunar (SL) valves to the aorta and pulmonary artery.. The opening and closing of the AV and SL valves are responsible for the heart sounds heard with a stethoscope.

1.ATRIAL SYSTOLE: Blood under low pressure flows into the atria from the pulmonary veins and vena cava. As the atria fill, the pressure of blood against the atrioventricular (AV) valves pushes them open and blood leaks into ventricles. The atria walls contract, forcing blood into ventricles.

2.VENTRICULAR SYSTOLE: The ventricles contract from the bottom of the heart upwards, increasing the pressure in the ventricles. Blood is pushed through the arteries. The pressure of the blood against the AV valves closes them, preventing back flow.

3.DIASTOLE; (atria and ventricles relax). Pressure in atria and ventricles is lowered by the relaxation of cardiac muscles. Blood under high pressure in the arteries is drawn back towards the ventricles, closing the semi-lunar valves, preventing back flow. The coronary arteries fill during diastole.