Heart Structure and Function The gross structure of the human heart and its associated blood vessels in relation to function. Heart Structure, Cardiac Cycle, ECG.

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Heart Structure.Structure The gross structure of the human heart and its associated blood vessels in relation to function. Pressure and volume changes and associated valve movements during the cardiac cycle. Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His. Cardiac output as the product of heart rate and stroke volume. Candidates should be able to analyse and interpret data relating to pressure and volume changes during the cardiac cycle.

Look at Right/Left Ventricles Wall Thickness? Explain why?

Chambers Right Atrium Right Ventricle Left Atrium Left Ventricle

Cardiac Muscle The heart itself is made from cardiac muscle. It has an endothelium lining the inside and an epithelium on the outside. The heart muscle is myogenic.

Cardiac Muscle Histological sectionDiagram

Heart Valves Pressure and volume changes and associated valve movements during the cardiac cycle. Septum ; Division between left and right side Bicuspid - left with two flaps Tricuspid – right with three flaps Heart strings (Chordae tendinae) – Stops valves inverting. Semi-lunar valve (aorta opening) – half moon shape Semi-lunar valve (Pulmonary artery opening) – half moon shape.

The cardiac cycle Pressure and volume changes and associated valve movements during the cardiac cycle. Describing the sequence of events in one heart beat

Definitions Systole = period of contraction (generally refers to ventricular systole). Diastole = period of relaxation (generally Ventricular systole). NOTE: Normally diastole is longer than systole.

Cardiac cycle General Principles. Contraction of the myocardium generates pressure changes which result in the orderly movement of blood. Blood flows from an area of high pressure to an area of low pressure, unless flow is blocked by a valve. Events on the right and left sides of the heart are the same, but pressures are lower on the right. Same volumes of blood is pumped from the two sides.

Atrial systole The heart is full of blood and the ventricles are relaxed Both the atria contract and blood passes down to the ventricles The atrio-ventricular valves open due to blood pressure 70% of the blood flows passively down to the ventricles so the atria do not have to contract a great amount.

Ventricular systole part 1. The atria relax. The ventricle walls contract, forcing the blood out The pressure of the blood forces the atrio- ventricular valves to shut (producing the heart sound ‘lub’)

Ventricular systole part 2 The pressure of blood opens the semi-lunar valves. Blood passes into the aorta and pulmonary arteries.

Diastole The ventricles relax Pressure in the ventricles falls below that in the arteries Blood under high pressure in the arteries causes the semi lunar valves to shut. This produces the second heart sound, ‘dub’. During diastole, all the muscle in the heart relaxes.

Blood from the vena cava and pulmonary veins enter the atria. The whole cycle starts again.

Cardiac cycle Match the letter on the graph provided to the following events (Annotate). Semi-lunar valves open Atrio-ventricular valves close, Semi-lunar valves close Atrio-ventricular valves open

atrio-ventricular valves open

atrio-ventricular valves close

atrio-ventricular valves openatrio-ventricular valves close semi-lunar valves open

atrio-ventricular valves openatrio-ventricular valves close semi-lunar valves open semi-lunar valves close

Candidates should be able to analyse and interpret data relating to pressure and volume changes during the cardiac cycle.

The cardiac cycle diagram shown depicts changes in aortic pressure (AP), left ventricular pressure (LVP), left atrial pressure (LAP), left ventricular volume (LV Vol). Heart sounds during a single cycle of cardiac contraction and relaxation are shown. These changes are related in time to the electrocardiogram (ECG)

Calculate heart rate (pulse). One full heart beat takes 0.8s in this example. What is the pulse rate of this person?

Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His. Purkyne (Purkinje) Fibres; long fibres through the septum to the apex of the ventricles. Bundle of His; Fibres from the AV node to the septum Sinoatrial (SAN) node; Pace Maker causes atrial contraction and stimulates AVN. Atrioventricular Node (AVN); causes ventricular contraction by fast tracking an impulse to the heart apex.

Cardiac Muscle The heart itself is made from cardiac muscle. It has an endothelium lining the inside and an epithelium on the outside. The heart muscle is myogenic. This means that the heart tissue generates the cardiac muscle contraction or beating within itself. This is initiated at the pace maker or Sinoatrial node (SAN).

Cardiac Cycle Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His.

Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Line of insulation stops the wave going to the ventricles from the top. Atrio-ventricular node bridges the insulation. Purkyne fibres and bundles of His take the impulse to the apex of the heart to cause an upward wave of ventricular systole.

Systole=Contraction (systems go!!!!) Diastole=Relaxation. A single cycle of cardiac activity can be divided into two basic stages. The first stage is diastole, which represents ventricular filling and a brief period just prior to filling at which time the ventricles are relaxing. The second stage is systole, which represents the time of contraction and ejection of blood from the ventricles. SYSTOLE IS FURTHER DIVIDED INTO ATRIAL SYSTOLE then VENTRICULAR SYSTOLE.

In together Down together Out together.

Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His. Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. electrical activity.

Describe how heart action is co-ordinated with reference to the sino-atrial node (SAN), and the atrio-ventricular node (AVN) and the purkyne tissue (bundles of His).

Pacemaker Ion imbalance at the SAN initiates a wave of depolarisation across the atria.

Interpret and explain electrocardiogram (ECG), traces, with reference to normal and abnormal heart activity. The spread of the electrical wave across the heart varies in speed. Prominent waves in the ECG indicate the synchronized start (or finish) of activity in significant fractions of the heart

(h) Interpret and explain electrocardiogram (ECG), traces, with reference to normal and abnormal electrocardiogram (ECG), abnormal The most basic feature of the ECG is that the time from any one such ‘peak’ to the same one in the next cycle indicates precisely how long the heart cycle is taking. At slow rates, the timing of the waves can be easily correlated to the heart sounds heard with the stethoscope.heart sounds

The P-wave indicates the electrical activity associated with contraction of the cardiac atria, the heart's upper chambers.

The P-R interval is the delay between the beginning of activity in the atria and the ventricles (atrio- ventricular conduction time). In adults, normal P-R intervals range between 120 and 200 milliseconds, occasionally being shorter in children and slightly longer in the aged.

The QRS complex indicates the onset of contraction of the ventricles. The shape of the QRS complex may be modified by a number of physiological factors (e.g. body position and breathing pattern). In normal adults, the duration of the QRS complex varies between 60 and 100 milliseconds; in children it tends to be shorter.

(h) Interpret and explain electrocardiogram (ECG), traces, with reference to normal and abnormal The Q-T interval is measured from the beginning of the QRS complex to the end of the T- wave and represents the time between activation of electrical activity in the ventricles and their return to the resting state. Like the P-R interval, the Q- T interval shortens at high heart rates and increases at lower rates.

Normal ECG The T-wave indicates when the electrical activity associated with the cells in the cardiac ventricle returns to the resting state after electrical activation. Thus, it signals the start of relaxation of the ventricle walls. It tends to be longer lasting than QRS because the onset of relaxation across the ventricle is less tightly synchronized than that of contraction.

Study the annotations on the graph and diagram on the next page transfer to your diagrams as much supplementary detail about the cardiac cycle as possible. Interpret and explain electrocardiogram (ECG), traces, with reference to normal and abnormal

Cardiac output as the product of heart rate and stroke volume. HR = Heart Rate Cardiac Output = HR x SV. SV = Stroke Volume (from one ventricle). The volume is the same from each ventricle.