Physiology Lecture 17: Cardiac Muscle

What is the value used to measure cardiac function?

Cardiac Output (CO or Q)

How can you calculate cardiac output?

Stroke Volume x Heart Rate

What is the value used to measure cardiac function that takes body surface area into account?

Cardiac Index

How can you calculate cardiac index?

Cardiac Output / Body Surface Area

Which side of the heart pumps deoxygenated blood and which one pumps oxygenated blood?

Deoxygenated - Right

Oxygenated - Left

Does deoxygenated blood and oxygenated blood have high or low pressure?

Deoxygenated - Low

Oxygenated - High

Which cardiac layer is the fibrosis layer that surrounds the heart?

Pericardium

What are the functions of the pericardium?

1. Anchor

2. Protect

3. Prevent overfill

What is the space between the pericardium and the heart?

Pericardial Space

What is the function of the pericardial space?

Reduce friction

What is the outermost layer of the heart?

Epicardium

What is the main feature of the epicardium?

Coronary arteries

Which layer of the heart is the muscle layer?

Myocardium

What is the function of the myocardium?

Contractility

What features of the myocardium allows synchronized contraction with low electrical resistance?

Intercalated Discs

Can the myocardium give a partial response?

No (All or None)

How does the AV node prevent the myocardium from always being contracted?

Sending delayed action potentials

What is the innermost layer of the heart?

Endocardium

What are the main features of the endocardium?

1. Conduction System

2. Valvular System

Does atrial or ventricular depolarization happen first?

Atrial Depolarization

What are the ways the cardiac muscle differs from the skeletal muscle?

1. Less, but wider T tubules

2. Closer T tubules to sarcoplasmic reticulum

3. T tubules open to extracellular space

How does the T tubules being open to extracellular space help with contraction in cardiac muscles?

Gives access to Ca to assist with contraction (All or None)

How does the action potential of myocardial tissue differ from other muscle tissue?

Longer with plataeu

What are the two ion channels that cause depolarization in myocardial tissue?

1. Fast sodium channels

2. Slow calcium channels (Plateau)

Which ion channel causes repolarization in myocardial tissue?

Potassium Channel

What are the main cardiac electrical properties?

1. Automaticity

2. Excitability

3. Conductivity

4. Contractility

5. All or None

Which side of the heart performs pulmonary circulation for gas exchange?

Right

Which side of the heart performs systemic circulation for peripheral perfusion?

Left

What is the pressure in the right atria called and what is the normal value?

Central Venous Pressure (CVP): 3 - 8 mmHg

What is the pressure in the left atria called and what is the normal value?

Pulmonary Capillary Wedge Pressure (PCWP): 4 - 12 mmHg

What is the pressure in the right ventricle called and what is the normal value?

Pulmonary Arterial Pressure (PAP): 8 - 15 mmHg

What is the pressure in the left ventricle called and what is the normal value?

Systemic Pressure: 60 - 90 mmHg

What is the catheter used to measure volume of blood circulating in the heart?

Swan Ganz Catheter (Pulmonary Arterial Catheter)

What is stroke volume?

Volume of blood ejected per contraction

How does a slow and fast heart rate affect ejection volume?

Slow - More ejection

Fast - Less ejection

How does a slow and fast heart rate affect oxygen consumption?

Slow - Decreased oxygen consumption

Fast - Increased oxygen consumption

Does excessive heart rate lead to a decrease or increase in cardiac output?

Decrease

How can you calculate stroke volume?

End Diastolic Volume - End Systolic Volume

What is end diastolic volume?

Volume of blood in chamber right before ejection

What is end systolic volume?

Volume of blood in chamber right after ejection

What is ejection fraction?

Percentage of EDV ejected per cardiac cycle

How can you calculate ejection fraction?

SV / EDV

What is heart rate extrinsically influenced by?

Autonomic Nervous System

What is the resting and filling phase of the heart called?

Diastole

What is the ejecting and contracting phase of the heart called?

Systole

What are the steps of ventricular contraction?

1. Passive Filling (Preload)

2. Atrial Kick

3. Isovolumetric Contraction

4. Ventricular Ejection

What does passive filling (preload) lead to?

AV valves open

What is the contraction of the atria to pump blood into the ventricles called?

Atrial Kick

What is the Frank Starling Law and why is atrial kick important?

Atrial kick delivers more volume into ventricles for sufficient myocardial stretch and contractile strength

What occurs after atrial kick?

AV valves close

What is the contraction of the ventricles that goes against the closure of all valves?

Isovolumetric Contraction

Does the volume of blood in the ventricles change during isovolumetric contraction?

No

Which contraction has the highest O2 consumption?

Isovolumetric Contraction

What occurs after isovolumetric contraction?

Semilunar valves open

What occurs after ventricular ejection?

Semilunar valves close

How can you calculate external work of the heart?

Stroke Volume x Mean Arterial Pressure

How can you calculate cardiac minute work of the heart?

Cardiac Output x Mean Arterial Pressure

If heart rate is fast, is diastole and systole shorter or longer?

Shorter

Starting from the inferior vena cava, what is the pathway of blood?

1. Inferior Vena Cava

2. Right Atrium

3. Right Ventricle

4. Pulmonary Artery

Starting from the pulmonary vein, what is the pathway of blood?

1. Pulmonary Veins (Lung)

2. Left Atrium

3. Left Ventricle

4. Aorta

What are features of fetal circulation that aren't in adult circulation?

1. Foramen Ovale

2. Ductus Arteriosus

What are the two AV valves?

Tricuspid and Mitral

What is the function of AV valves?

Prevent backflow during ventricular systole

What are the papillary muscles that support the AV valves?

Chordae Tendineae

What is the function of Chordae Tendineae?

Prevent valve from bunging into atrial during ventricular systole

What are the two semilunar valves?

Pulmonic and Aortic

Do the semilunar or AV valves have faster closure?

Semilunar Valves (Higher pressure changes)

Do the semilunar or AV valves have faster velocity?

Semilunar Valves (Smaller diameter)

In which interspace can you hear the AV valves best?

5th ICS

In which interspace can you hear the semilunar valves best?

2nd ICS

What are the normal heart sounds caused by valves closing?

S1 and S2

What causes S1 sound?

AV valves closing (Atrial Kick)

What does S1 sound represent?

Beginning of ventricular systole

What causes S2 sound?

Semilunar valves closing (Ventricular Ejection)

What does S2 sound represent?

Beginning of ventricular diastole

What causes S3 and S4 sounds?

Alterations in filling (Abnormal)

What causes murmur sounds?

Alterations in valve structures (Abnormal)

What is the amount of blood coming back to the heart called?

Preload

What is the resistance that the heart needs to overcome to pump blood out of the ventricles?

Afterload