Question

What are the three types of specialized cells that can initiate the contraction cycle? Describe in detail the conduction pathway of each. What is the resulting heart rate for each?

NOTE: THIS QUESTION HAS DO TO WITH THE CARDIOVSACULAT SYSTEM AND NOT THE MUSCULAR SYSTEM. THANK YOU

Answer 1

• The muscle cells of heart are contractile cells.
• The myocardial contractile unit consist of sacromeres that contains thick and thin filaments.
• Thick filaments are myosin filaments and thin filaments are actin filaments.
• In skeletal muscles, shortening of cardiac muscle occur by the sliding filament mechanism.

The conducting system of heart consists of sinoartrial(SA)node,Internodal pathways,Atrioventricular(AV)node,His bundle,bundle branches and purkinje fibers.

• The SA node is the primary pacemaker which contains pacemaker cells.The pacemaker cells generate the impulse,which is transmitted in conducting system for exitation and contraction.
• There are three internodal pathways that connect SA ode and AV node. (1)The anterior internodal pathway,middle internodal pathway and posterior internodal pathway.
• In AV node the rate of impulse conduction is slow,usually a delay of 0.1 sec and it is termed as AV nodal delay and it is shortened by sympathetic stimulation and lenghthened by parasympathetic stimulation.
• His bundle is a small bundle of fibers that arises from AV node and terminates in the purkinje system.
• Purkinje fibers is a network of small bundles of conducting fibers that are present throughout the subendocardial region of right and left ventricles.