The Heart Flashcards
(33 cards)
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
Gender Autonomic activity Age Hormones Exercise Temperature 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?
70ml
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.
