8.5: The Heart Flashcards
What type of muscle is the heart made of?
Cardiac muscle.
What supplies the cardiac muscle with oxygenated blood?
Coronary arteries.
What is the function of the coronary arteries?
To supply the cardiac muscle with the oxygenated blood that it needs to continue contracting and relaxing
What is the name of the membrane that the heart is surrounded by?
Inelastic Pericardial Membranes
What is the purpose of the inelastic pericardial membrane?
To prevent the heart from over-filling and over-stretching
Do the atria have thick or thin muscle walls?
Thin
Which side of the heart pumps oxygenated blood?
Left side
What is the function of the atrio-ventricular valves?
-Open to let blood pass into the ventricles from the atria
-Close to prevent backflow of blood back to atria.
What is the alternate name for bicuspid and tricuspid valves?
Atrioventricular valves
What is the alternate name for atrioventricular valves?
Bicuspid and tricuspid valves
Is the bicuspid valve in the left or right side of the heart?
Left
How are atrioventricular valves attached to the walls of the ventricles?
By tendons
What is the function of tendinous cords?
-Connects the atrioventricular valves to the ventricles
-Makes sure the valves are not turned inside out by the pressure exerted when the ventricle contracts
Which side of the heart’s muscular wall is thicker: left or right?
Left
Why does the left side of the heart’s muscular wall need to be thicker?
To provide sufficient force to:
-Overcome the resistance of the aorta and arterial systems of the whole body
-Move the blood under pressure to all the extremities of the body
Why is the right side of the heart’s muscular wall not thick?
-Because the right side of the heart passes blood to the lungs, which are smaller than the rest of the body, and closer to the heart.
-The right side of the heart only has to overcome the resistance of pulmonary circulation
What is the septum?
The inner dividing wall of the heart
What is the function of the septum?
To prevent the mixing of oxygenated and deoxygenated blood
When does the right atrioventricular valve open?
When slight pressure builds up in the right atrium
When does the right atrioventricular valve close?
When the right ventricle starts to contract
When does the atrium contract?
Once both the atrium and ventricle are filled
When does the ventricle contract?
When there is no more blood in the atrium
When does the semi-lunar valve open?
When the ventricle contracts
What do semi-lunar valves do?
Prevent the backflow of blood back into the heart
What is the cardiac cycle?
The events in a single heartbeat
What are the two key parts of the cardiac cycle?
Diastole and Systole
What happens during diastole?
The heart relaxes
-Atria and ventricles fill with blood
-Volume increases, pressure decreases (of blood)
-Pressure in arteries is at a minimum
What are the two parts of systole?
Atrial systole and ventricular systole
What is cardial output?
Volume of blood pumped out of the heart during one minute
What happens during systole
-First the atria contract (atrial systole), then the ventricles contract (ventricular systole)
-Pressure inside the heart increases drastically, and blood is forced out of the heart.
-Volume of blood in heart decreases
-Pressure in the arteries is at a maximum
By the end of systole, is the volume of blood in the heart high or low?
Low
What is stroke volume?
The volume of blood pumped out by hte left ventricle in each beat.
What is the equation for Cardial Output?
Cardian Output = Stroke Volume x Heartrate
What is mass flow?
The bulk movement of blood from one part of the body to another as a result of pressure difference between the two points
Which valve opens/closes when the pressure in the atrium is greater than the pressure in the ventricle?
The atrioventricular valve opens
Which valve opens/closes when the pressure in the ventricle is greater than the pressure in the atrium?
The atrioventricular valve closes
Which valve opens/closes when the pressure in the ventricle is greater than the pressure in the arteries?
The semilunar valve opens
Which valve opens/closes when the pressure in the arteries is greater than the pressure in the ventricle?
The semilunar valve closes
What is the general sound of the heart?
“Lub-dub”
What does the “lub” sound of a heartbeat represent?
Blood is being forced against the atrioventricular valves as the ventricles contract
What does the “dub” sound of a heartbeat represent?
Backflow of blood closes the semilunar valves in the aorta and pulmonary artery as the ventricles relax
Why is the pressure in the atrium lower than the pressure in the left ventricle? (for what purpose)
-Because the ventricle has a thicker muscle wall and has to generate more force to force blood around the whole body
-The atrium only has to force blood into the ventricle, aided by gravity (so less force is required)
How does the structure of the aorta help to maintain a minimum pressure?
-Has strong elastic tissue, allowing it to stretch and recoil.
-Recoiling reduces volume and increases pressure, creating a pulse and pushing the blood
Why is atrial pressure relatively low?
Because the thin walls of the atrium cannot create much force
Why does aortic pressure initially increase?
When the ventricles contract as blood is forced into the aorta
What are the contractions of the cardiac muscle?
Myogenic
What is the purpose of the cardiac muscle being myogenic?
Prevents the body wasting resources maintaining the basic heart rate
What is the basic rhythm of the heart maintained by?
A wave of electrical excitation
What does AVN stand for?
Atrioventricular node
What does SAN stand for?
Sinoatrial node
Where is the sinoatrial node located?
Wall of the right atrium
State the process of electrical excitation of the heart (long answer)
-Sino-atrial node produces a wave of electrical excitation
-Impulse spreads across both atria making them contract
-Excitation transmitted to the atrioventricular node, and is delayed slightly
-Electrical impulse passes from the AVN to the bundle of His, made of Purkyne fibres that pass through the septum
-Bundle of His splits into 2 branches and conducts the wave to the bottom of the heart
-Excitement spreads across both ventricles from the bottom to the top
-Ventricles contract from the bottom upwards
Why do the ventricles contract from the bottom upwards?
To ensure all the blood is forced out
What is an alternative name to the bottom of the heart?
The apex
What is the bundle of His made up of?
Purkyne fibres
Why is there a layer of non-conducting tissue between the atria and the ventricles?
To ensure that the excitation is not passed onto the ventricles before the atria have fully contracted and emptied
Why is the SAN called the natural pacemaker?
Because the rate at which the SAN produces the waves of electrical excitement determines the rate of the heartbeat
What is an electrocardiogram?
A recording of the electrical activity of the heart
What does an electrocardiogram measure?
Tiny electrical differences in your skin, which result from the electrical activity of the heart
What are ECGs used for?
Recording electrical activity of the heart and diagnosing heart problems
What does ECG stand for?
Electrocardiogram
What are the letters representing different segments of an ECG?
P, Q, R, S, T
What does the P wave of an ECG represent?
Wave of excitation passing to the atria, causing them to contract
What does the QRS complex of an ECG represent?
Wave of excitation passing to the ventricles, causing them to contract
What does the T wave of an ECG represent?
The heart relaxeing before the next heart beat, returning to its original state
What does arrhythmia mean?
Abnormal rhythm of the heart
What is Tachycardia?
Rapid heartbeat, still evenly spaced out
What is the term for when your heartbeat is rapid?
Tachycardia
What is bradycardia?
Slow heartbeat, still evenly spaced out
What is the term for when your heartbeat is very slow?
Bradycardia
What is an ectopic heartbeat?
When there are extra heartbeats that are out of the normal rhythm
What is the term for when you have extra heartbeats that are out of the normal rhythm?
Ectopic heartbeat
What is atrial fibrillation?
When rapid electrical impulses generated in the atria prevent atria from contracting properly and make the heart not pump blood efficiently
