Cardiac Muscle

Dr. Mohammed Abdul Dr. Mohammed Abdul Hannan HazariHannan Hazari

Assistant Professor,Assistant Professor,Department of Physiology,Department of Physiology,Deccan College of Medical Deccan College of Medical

Sciences, HyderabadSciences, Hyderabad

Heart

Coronary Arteries

Anterior View Posterior View

Heart Location In The Chest

Precordium

Weight: 300g

Work: 72beats/min

Pumps: 70mL/beat

The busy and hard working heart!

Heart

Heart Chambers

Left atrium

Right atrium

Left ventricle

Right ventricle

Heart Pump

• The heart pumps blood by contraction and relaxation.

• Contraction is called systole.• Relaxation is called diastole.• The Cardiac Cycle is the cycle

through one systole and one diastole.

Heart Pump

2. Left Heartreceives oxygenated blood from pulmonary veinspumps blood into systemic circulation

1. Right Heart

receives venous blood from systemic circulation via superior and inferior vena cava into right atrium

pumps blood to pulmonary circulation from right ventricle

Direction Of Flow In The Heart

Heart Valves

1. Atrioventricular Tricuspid

• between RA and RV

• three leaflets Mitral

• between LA and LV

• two leaflets

2. Semilunar

Pulmonic--three leaflets

Aortic--three leaflets

Cardiac Muscle

Myocardial cells

1. Working myocardial cells• Contraction & relaxation (Heart

Pump)

2. Pacemaker cells• Impulse generation & conduction

(Conducting system of the heart)

Cardiac Muscle

•Striated

•Sarcomere is the functional unit.

•Nuclei - centrally located.

•Abundant mitochondria.

Cardiac Muscle

• SR is less abundant than in skeletal muscle.

• Sarcolemma has specialized ion channels that skeletal muscle does not voltage-gated Ca2+ channels.

The Sarcomere

1.6 – 1.7 μ

Cardiac Muscle

Functional Syncitium

• Fibers are branched; connect to one another at intercalated discs.

• The discs contain several gap junctions providing cytoplasmic continuity.

• Rapid transmission of impulse.• 2 syncitia

– Atrial syncitium– Ventricular syncitium

*Separated by fibrous ring

Ventricular Action Potential

Conducting System Of The Heart

Sinoatrial node (SAN) – pacemaker

Internodal pathways –fast conduction

Atrioventricular node (AVN) – nodal delay

Bundle of His – fast conduction

Rt. & Left bundle branches

Purkinje’s fibers

Atrial muscle

Ventricular muscle

Direction Of Spread Of Impulse

Membrane Potential Of SAN

L-type

T-type

Conduction Speeds In Cardiac Tissue

Tissue Conduction Rate (mts/s)

SA node 0.05

Atrial pathways 1

AV node 0.05

Bundle of His 1

Purkinje system 4

Ventricular muscle 1

Questions?

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