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Physiology - Cardiovascular > The Heart > Flashcards

Flashcards in The Heart Deck (33)
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Where is the precise location of the heart?

The thoracic cavity - in the mediastinum (space between lungs). Apex is 9 cm to the left of the midline at the level of the 5th intercostal space.


What are the 3 layers of tissue that comprise the heart wall?

Pericardium (has a fluid gap within it)
Myocardium (largest)
Endocardium (innermost tissue)


How is the pericardium divided?

Outer sac is the fibrous pericardium.

Inner sac is the serous pericardium.


What are the properties of the fibrous pericardium?

Is continuous with the tunica adventitia of the great blood vessels above and it is inelastic, which prevents over distension of the heart.


How is the serous pericardium subdivided?

Outer layer: parietal pericardium (borders fibrous pericardium).

Inner layer: visceral pericardium (adherent to the heart muscle).


What is produced in the serous membrane?

Flattened epithelial cells secrete serous fluid, (pericardial fluid) into the space between the visceral and parietal layers. This allows smooth movement when the heart beats.


Name the factors affecting heart rate

Autonomic activity
Baroreceptor reflex
Emotional State


State the Cardiac Cycle (simplified)

SA node triggers
Atrial depolarization
AV node introduces delay of 0.1 seconds
AV node triggers
Down bundle of his into left and right branches
Purkinjie fibres
Ventricle Depolarization
Complete cardiac diastole (0.4 seconds)


What is the lub sound from a heart caused by?

Closure of the AV valves (biscupid and mitral)


What is the dup sound from a heart caused by?

Closure of the Semi-Lunar valves (Aortic and Pulmonary)


What does the ECG show?

The Electrocardiogram shows the spread of electrical activity generated by the SA node as it travels through the atria, and the AV node as it travels to ventricles.


What are the 5 waves of an ECG called?

P,Q,R,S and T


Explain the P Wave

The 1st wave on the ECG, medium in size - it represents when impulse from SA node sweeps over atria (atrial depolarization)


Explain the QRS complex

Represents the rapid spread of the impulse from the AV node down the septum to the purkinjie fibres causing ventricular depolarization.


Explain the T Wave

Represents the relaxation of the ventricular muscle.


What is cardiac output?

The amount of blood ejected from each ventricle every minute


What is stroke volume?

The volume of blood ejected from each ventricle per contraction


What is the equation for Cardiac Output?

Stroke Volume * Heart rate


What is the healthy stroke volume at rest?



What is an increase in cardiac output (for e.g during exercise) called?

cardiac reserve


What is the volume of blood in a ventricle before contraction called?

VEDV: Ventricular end diastolic volume
also known as preload.


What is the equation for blood pressure?

Cardiac Output * Peripheral Resistance


Explain the properties and function of the myocardium.

Myocardium is the middle layer of the 3 layers of the heart. It is composed of specialized striated muscle, which is not under voluntary control. These muscles are arranged into fibres, (with nuclei) which branch off. The joints at where different branches meet are called intercalated discs and appear as thick dark lines. These joints ensure a separate nerve supply is not needed.


What is secreted in the walls of the atria?

ANP (atrial natriuretic peptide) is secreted by specialized muscle cells in the walls of the atria.


What supports the myocardium?

The Fibrous Skeleton of the heart.


What is the endocardium?

A layer that lines the chambers and valves of the heart. It is a smooth membrane, and consists of flattened epithelial cells, and is continuous with the endothelial lining the blood vessels.


How many cusps do the right and left AV valves have?

The right (tricuspid) valve has 3 cusps, and the left (mitral) valve has 2 cusps.


What are cordae tendinae?

Strong cords which stop the valves opening the wrong way. They are supported by papillary muscles.


How is the heart supplied with blood?

Left and right coronary arteries which branch from the aorta. They recieve about 5% of the blood pumped from the heart.


How is the heart's blood supply drained?

Venous drainage, venous blood is collected into a number of cardiac veins which later join the cornary sinus which opens into the right atrium.