3. Cardiac Muscle Structure & Function Flashcards
When does state 4 end?
hydrolysis of ATP
What are the major regulatory proteins in the cross bridge?
the troponins
What is the inhibitory filament- inhibits myosin binding to actin- has a special N-terminal sequence for beta-adrenergic responsiveness?
troponin-I
What causes diastolic heart failure?
usually titin mutations or dysfunction
What regulates Ca++ sensitivity?
Troponin-I phosphorylation**, isoform composition, and sarcomere length
The elastic properties of ____ allows sarcomeres to stretch and contract over large distances.
titan
What binds tropomyosin and may be involved in the developmental regulation of isoform expression?
troponin-T
What is titin?
one of the major proteins responsible for passive elastic properties of the cell (forms an elastic springs)
What is the A band?
thick filaments
What is the active state?
the force-generating state during contraction
What are end-to-end arrays of identical sarcomeres called?
myofibrils
The thin filament proteins seem to regulate ____ whereas thin filament proteins regulate ____.
force; relaxation
What is myosin composed of?
2 heavy chains and 4 light chains
What is the Frank-Starling Law of the Heart?
increasing preload volume increases the force of contraction
How many Ca++ binding sites to troponin-C does cardiac muscle have? How many does skeletal muscle have?
1; 2
Name 5 specialized features of cardiac muscle cells that allow it’s contractility.
- they’re striated 2. not under direct neural control 3. they’re shorter, narrower, and richer in mitochondria 4. slower ATPase activity 5. Ca++/troponin regulates actomyosin
What is aortic pressure?
afterload on the left side of the heart
What is the overlap of thick filaments called
the Z line
_____ provide adhesion and assure that force generated by one cell is passed to the other.
Desmosomes
What is the only alpha-isoform in the heart?
tropomyosin
What is the transition state?
Ca++ enters the myocyte, binds to troponin-C, conformational change occurs and moves tropomyosin out of the way (non-force generating)
What are the thick filaments collectively called?
the A band
What is troponin-T?
binds tropomyosin; developmental regulation of isoform expression
What is the H zone?
only actin, no thick filaments
What is the unit of contractile activity composed of actin and myosin extending from Z line to Z line in a myofibril?
a sarcomere
Beta-myosin has a ____ ATPase than alpha-myosin.
slower
The elastic properties of titan allows sarcomeres to ____ and _____ over large distances.
stretch; contract