L12-structure Of The Cardiac Muscle Flashcards
Layers of the heart
Pericardium
Myocardium
Endocardium
Features of cardiac muscle
Involuntary muscle
Rhythmic contraction
Striated under the microscope
Structure of the cardiac muscle
▪️formed of long cylindrical fibers
▪️branch and anastomose
▪️formed of myocytes joined by intercalated discs
What is the intercalated disc formed of
Transverse portion
Desmosomes(cadherin)
Longitudinal portion
Gap junction
Functional significance of intercalated discs
Provides physical attachment of myocytes
Electrical communication
What is the pathway of depolarization
SA node—internodal pathway—AV node—AV bundle—bundle branches—purkinje fibers
What are the components of the muscular tissue
Myocytes
Sarcoplasm
Sarcolemma
Function of muscular components
Contraction and relaxation so it needs:
Contractile protein filaments(myofilaments, ATP, calcium ions)
Ultrastructure of cardiac muscle fibers
Intercalated discs The myofibrils T-tubules Sarcoplasmic reticulum Other sarcoplasmic constituents
Describe the myofibrils
are grouped myofilaments
Dark A bands thick and thin
Light I bands only thin
Why do cardiac muscle fibers appear striated
A bands alternate with I bands regularly along each myofibril
What is the sarcomere
▪️Area from z line of I band to z line of next I band
▪️functional unit of myofibril (interaction between actin and myosin)
Describe the arrangement of myofilaments in sarcomere
Types of myofilaments 1-thick Limited to A band Free from both sides 2-thin Actin Tropomyosin Troponin complex
Describe the molecular structure structure of thin myofilaments
Actin: G actin—fibrillar actin—double helix
Tropomyosin:long rope like protein filament situated in the space between the 2 strands of actin filament
Troponin complex:Tn C,TnT,TnI
What are the 3 subunits of troponin and what do they bind to
Tn-A:binds to actin
Tn-T:binds to Tropomyosin
Tn-C:binds to calcium ions
