Peshawar Medical College NWFP Pakistan 1 2 Peshawar

Peshawar Medical College NWFP Pakistan 1

2 Peshawar Medical College NWFP Pakistan

CARDIAC MUSCLE OBJECTIVES At the end of this lecture you should be able to know types of cardiac muscle and its anatomical location. • Arrangement of myofilaments and sarcoplasmic reticulum • Steps involved in Contraction • Functional differences Peshawar Medical College NWFP Pakistan

CARDIAC MUSCLES • Cardiac muscle is found only in heart. • Shape = Rectangular shape. Short branched cells • Diameter = 20 um Length = 100 um • Single nucleus • Regeneration of cardiac muscle fiber is controversial. Recent studies suggest that cardiac muscle cells have mild proliferative property. Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

Cardiac muscle • • Thick myosin filaments. Thin actin filaments (Troponin present) Striated appearance. T-Tubule system associated with calcium loaded sarcoplasmic retculum. • Contraction occurs by sliding filament mechanism. Peshawar Medical College NWFP Pakistan

Intercalated Disks • Structures between adjacent cells. • Myofibrils attached to desmosomes. • Gap junctions present. Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

Input influencing Cardiac muscle contractile activity. 1. Sinoatrial node (SA node-Pacemaker) Location=Superior posterolateral wall of right atrium. Hormones. Neurotransmitters Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

• EXCITATION CONTRACTION COUPLING IN CARDIAC MUSCLE Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

Sources of Cytosolic Calcium • L-Type calcium channels (modified DPR) (L= long lasting current )—Cardiac muscle cannot under go tetanic contractions. • ECF calcium 1. Depolarization of plasma membrane. 2. Slight Increase in cytosolic Ca 3. Triggers release of Ca from SR. • Rynaodine receptors (Ca channels) Peshawar Medical College NWFP Pakistan

• Thin filament activation • Cross- bridge cycling • Force generation • Same as SKELETAL MUSCLE Peshawar Medical College NWFP Pakistan

Action Potential in Cardiac Muscle. Peshawar Medical College NWFP Pakistan

• Steps involved in contraction of Cardiac muscle Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan

• Contraction ends • Cytosolic Ca conc is restored Ca-ATPase pumps Na/Ca countertranspoters Peshawar Medical College NWFP Pakistan

• Contraction ends • Cytosolic Ca conc is restored. Ca-ATPase activity Na/Ca countertranspoters Peshawar Medical College NWFP Pakistan

Peshawar Medical College NWFP Pakistan