Cardiac Physiology

The heart is located within…

The mediastinum just above the diaphragm

The heart is enclosed in a…

Pericardium

The heart is a…

Hallow muscle double pump

The heart is divided into…

Four chambers

The left and right chambers of the heart have a…

Collecting chamber (an atrium) and a pumping chamber (a ventricle)

There are three principal circulatory divisions in the cardiovascular system:

• Systemic circulation

• Pulmonary Circulation

• Coronary Circulation

Systemic circulation carries…

Oxygenated blood from the left ventricle through the body, and returns venous blood to the right atrium

Pulmonary circulation carries…

Venous blood from the right ventricle through the lungs (blood undergoes oxygenation) and delivers oxygenated blood through four (4) pulmonary veins into the left atrium

Coronary circulation delivers…

Oxygenated blood for the heart through the coronary arteries

Venous blood from the heart through cardiac veins collects…

Collects into the coronary sinus and empties into the right atrium

Both pumps contract at…

The same time and both sides pump equal amounts of blood with each cycle of contraction and relaxation

Contraction

Systole

Relaxation

Diastole

General Organization of the Circulatory System

• Closed system

• Heart

• Arterial System

• Venous System

• Microcirculation

• Systemic circulation

• Pulmonary circulation

Blood movement through the heart goes from the systemic circulation (venous blood) to the…

Superior/ Inferior Vena Cava

From the superior vena cava the blood moves to…

The right atrium

From the right atrium the blood moves to…

Right ventricle

From the right ventricle the blood moves to…

Pulmonary Arteries (L/R)

From the pulmonary arteries the blood moves to…

Pulmonary circulation

From the pulmonary circulation the blood moves to…

The pulmonary veins

From the pulmonary veins the blood moves to…

The left atrium

From the left atrium the blood moves to…

The left ventricle

From the left ventricle the blood moves to…

The aorta

From the aorta the blood moves to…

The systemic circulation (arterial blood)

Heart Wall Morphology

• Pericardium

• Epicardium

• Myocardium

• Endocardium

Pericardium

Composed of fibrous pericardium + visceral and parietal layers

Epicardium

Superficial visceral layer of the serous pericardium

Myocardium

Composed of the contractile cells - part which actually contracts

Endocardium

Composed of epithelial and connective tissue + elastic fibers

Skeletal muscles are composed of…

A big number of muscle fibers (cells)

Each muscle fiber has…

The same length as a muscle

Skeletal muscle fibers have a signficant…

Number of nuclei (myonuclei), which are located beneath the sarcolemma

Cardiac muscle cells (myocytes) are arranged in…

Layers and are shorter than skeletal muscles

Cardiac muscles has properties of…

A skeletal muscle and of a smooth muscle

Cardiac muscle cell has only…

1-2 nuclei (myonuclei)

Cardiac muscle cells are connected through…

Intercalated discs

Gap junctions in the intercalated discs are…

Similar to those in the smooth muscles

Cardiac muscle is a…

Syncytium

Gap junctions in intercalated discs provide…

Low electrical resistance

Intercalated discs separate…

Cardiac Cells

The different syncytiums

• Artrial Syncytium

• Ventricular Syncytium

Myocyte is surrounded by…

The plasma membrane - sarcolemma

Cytoplasm of the cardiac cell contains…

Contractile proteins (Myofilaments)

Myofilaments are composed of…

Actin and Myosin

Actin and myosin have a…

Parallel orientation along the axis of the fiber/myocyte

Thin filament (actin) is anchored to the…

Z-Disc (Z-Line)

Distance between two Z-lines is a…

Functional unit of a cardiac cell -sarcomere

Between myofibrils…

Abundant mitochondria are found

The smooth endoplasmic reticulum is also known a…

Sarcoplasmic Reticulum

The smooth endoplasmic reticulum (sarcoplasmic reticulum) is a…

Storing site of calcium ions in the cell

Electrical Properties of the Cardiac Muscle

• Resting membrane potential in cardiac cells (-85 to -95 mV)

• Resting membrane potential in conductive fibers (-90 to -100 mV)

• Resting potential is stable

The resting membrane potential in cardiac cells…

-85 to -95 mV

The resting membrane potential in conductive fibers…

-90 to -100 mV

Phase 0

DEPOLARIZATION (Na+ enters in about 2 msec)

Phase 1

EARLY REPOLARIZATION (Na+ channels start to incativate)

Phase 2

PLATEAU (Ca2+ enters about 200 msec)

Phase 3

REPOLARIZATION (K+ channels open)

Phase 4

ION DISTRIBUTION RESTORED (Na+/K+ pump)

Action Potential in the Cardiac Muscle

• Prolonged action potential and plateau in cardiac muscle

• Opening of fast sodium channels (open 1/1000 s) - Phase 0

• Opening of slow calcium channels (open 1/10 s) - Phase 2

• Maintained a prolonged period of depolarization

• Very long (250 ms) refractory period (Impossible to cause stimulation of contractions)

Excitation-Contraction Coupling

• Action Potential

• Calcium Transients

  • Resting cytosolic calcium is increased

  • 10% of calcium enters via calcium influx through T-tubules into the sarcoplasmic reticulum

  • Calcium is released from the sarcoplasmic reticulum

• Calcium combines with troponin

• Tropomyosin’s inhibition is removed

• Criss-bridges are formed

• Contraction

Sarcoplasmic reticulum of cardiac cells is…

Less developed than of skeletal muscles

T-Tubules of cardiac cells have…

large diameter (5 times more than of skeletal muscles)

Electronegative mucopolysaccharides bind…

Calcium ions in T-Tubules

T-tubules open directly…

To the outside of the cardiac cells

Extracellular calcium significantly affects…

Cardiac cell contraction

Systole

250-300 ms

Diastole

500-550 ms

Atrial Contraction is initiated by…

Generation of action potential in the sinus node

Atrial Contraction (A-B)

• Mitral valve is opened

• Aortic valve is closed

• 75% of blood flows directly from atrias into ventricles

• 25% of blood flows into ventricles due to atrias contraction

Isovolumic (Isometric) Ventricular Contraction

• Mitral valve is closed

• Aortic valve is closed

• Volume of blood in ventricles remains constant

• Ventricles contract. Pressure in the ventricles is building

Ventricular Ejection (Rapid Ejection Period and Slower Ejection Period)

• Mitral valve is closed

• Aortic valve is opened

• Ventricles continue contracting

Isovolumic (Isometric) Ventricular Relaxation

• Mitral valve is closed

• Aortic valve is closed

• Ventricles relaxing

• Pressure rapidly drops to diastolic values

Passive Ventricular Filling

• Mitral valve is opened

• Aortic valve is closed

• Blood collects in atrias

• Blood fills the ventricles

End Systolic Pressure (ESP)

120 mmHg

End Diastolic Pressure (EDP)

0 mmHg

These volumes are found within the heart…

• End Systolic Volume (ESV)

• End Diastolic Volume (EDV)

Stroke Volume

65 mL

Sound travels through the…

Chest

When valves close…

Pressure gradient develops

During the cardiac cycle the surrounding tissue, fluids, and blood vessels…

Vibrate

Frequency of heart sounds during the cardiac cycle

3 Hz - 40 Hz - 500 Hz

Normal sounds consists of…

• First Heart Sound (S1)

• Second Heart Sound (S2)

• Third Heart Sound (S3)

Abnormal Sounds

Murmurs of the Heart

The first heart sound (S1) has a…

“LUB” (A-V valves vibration at the beginning of systole) 0.14

The two components of the first heart sound…

• Mitral

• Tricuspid

The second heart sound (S2) is a…

Higher frequency than the first sound

The second heart sound (S2) has this type of sound…

“DUP” (Aortic valves vibration at the end of systole) 0.11s

The two components of the second heart sound (S2)

• Aortic

• Pulmonic

Third heart sound (S3)

Occasional weak sound, recorded in the phonocardiogram

Dr. Rene Lannec

Discovered the stethoscope (1816)

Cardiac output is…

The amount of blood ejected from the heart

Cardiac Output equals…

Heart Rate x Stroke Volume

Heart Rate is…

68-72 per min

Cardiac Output is determined by…

The autonomic effects upon the SA node

Stroke Volume is…

65-75 mL

The two different controls of the Cardiac Output…

• Intrinsic Control (Venous Return)

• Extrinsic Control (Sympathetic Stimulation)

Blood Pressure equals…

Heart Rate x Stroke Volume x Resistance

Parasympathetic N.S has…

No effect on stroke volume

The venous return can…

Increase or decrease stroke volume

Autonomic Effects are due to…

Sympathetic and Parasympathetic N.S