1C: Cardiac Muscle Contraction Flashcards
What is the thin filaments called?
Actin, Tropomyosin, and Troponin
What is the thick filaments called?
Myosin
What is the sliding filament theory and cross bridge cycling ?
Explains that thick and think filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere.
What are the steps in cardiac muscle excitation-contraction coupling ?
1) Cardiac muscle cell (myocyte) action potential spreads from the sarcolemma in to the T-tubules.
2) During the plateau phase of this action potential, Ca++ channels open and Ca++ enters the cell from the ECF
3) This Ca++ entry triggers the release of Ca++ from the sarcoplasmic reticulum
4) As a result of this Ca++ release, ICF (ca++) rises significantly
5) Ca++ binds to troponin C, & tropomyosin is moved out of the way way, removing the inhibition of actin & myosin binding.
6) Actin & Myosin bind, thick & thin filaments slide past each other, & cardiac muscle cell contracts. (Tension is = ICF [ca++]
7) Relaxation occurs when Ca++ is reaccumulated by the SR & moved from the IFC back to the ECF
Compare and Contrast Cardiac vs. Skeletal Muscle
Skeletal muscle is striated, voluntary, has thick and think filaments, more dense Sarcoplasmic Reticulum, and have many mitochondria.
Cardiac muscle is striated, involuntary, has thick & thin filaments, less dense SR, tons of mitochondria, and intercalated discs.
What are intercalated discs?
The plasma membranes of adjacent cardiac muscle cells interlock at dark-staining junctions.
Note: Skeletal muscle cells are independent of one another both structurally and functionally.
What are the function of desmosomes in intercalated discs?
Prevents adjacent cardia cells from separating during contraction
What is the function of gap junctions within intercalated discs?
Allows ions to pass freely from cell to cell, directly transmitting the depolarizing current across the entire heart
What is a functional syncytium when referring to intercalated discs?
Because cardiac fivers are electrically coupled by the gap junctions, the entire myocardium behaves as a single coordinated unit
What are the 3 proteins in the cardiac Troponin complex
1) cardiac Troponin C (cTnC)
2) cardiac Troponin I (cTnI)
3) cardiac Troponin T (cTnT)
What does the T, I and C stand for in the cardiac troponin complex ?
T= tropomyosin binding I= inhibitory C= calcium binding
True or False? Skeletal and cardiac Troponin T and I isoform differ from each other in amino acid sequence.
true
What do Angina and Myocardial infarction have in common?
- Both are due to myocardial ischemia as a result of atherosclerosis.
- Both result in chest pain
In general what is anginal pain often related to ?
Exertion , emotion, eating, or cold.
-Usually short lived and relieved by NTG
When does the pain associated with myocardial infarction occur?
Occurs spontaneously, is more long-lasting compared to anginal pain and is NOT relieved by NTG.
