Cardiovascular Physiology 14 Flashcards
What follows depolarization of the cardiac myocytes?
The contraction of the cardiac myocytes
What is the shaped of Cardiac Myocytes?
Branched or Y shaped
What are Cardiac Myocytes joined together by?
Intercalated discs
What occurs at the intercalated discs of cardiac myocytes?
Cardiac myocytes are extensively intertwined
What are found at the intercalated discs of myocytes?
Gap junctions and desmosomes
What is the Sarcolemma?
The plasma membrane of a cardiac myocyte
What are the mitochondria of cardiac myocytes important for?
Supplying the myocyte with ATP
What is the Sarcoplasmic Reticulum?
A special type of smooth endoplasmic reticulum which stores and pumps calcium ions
What does the Sarcoplasmic Reticulum in cardiac myocytes do?
Stores and releases calcium when the muscle cell is stimulated
What are Cardiac Myocytes made up of?
Myofibrils
What do Myofibrils run the length of?
The length of the branched muscle cell
What is each Myofibril made up of?
Sarcomeres
What are Sarcomeres?
The contractile unit of muscle
What do Sarcomeres contain?
The protein filaments actin and myosin
What gives cardiac muscle cells its striated appearance?
The orderly arrangement of actin and myosin
What are T-tubules?
Invaginated of the Sarcolemma
What do the T-tubules surround?
The myofibrils
What do T-tubules do in Cardiac Myocytes?
They transmit action potentials propagated along the surface membrane to the interior of the muscle fiber
What is the lumen of the T-tubule continuous with?
The extracellular fluid in the muscle fiber
What does the T-tubule lie in close proximity to?
The sarcoplasmic reticulum
What kind of channels do T-tubules have a lot of?
L-type calcium channels
What controls contraction of the cardiac muscle?
Calcium ions
What are normal concentrations of calcium inside and outside the cell?
Calcium is usually found in low concentrations inside the cell and high concentrations outside the cell
When do extracellular calcium ions enter the cytoplasm of a cardiac myocyte?
During the plateau phase of an action potential through the the L-type calcium channels
What does the Calcium that enters the cell during the plateau phase of a cardiac muscle action potential through the L-type channels do?
Binds to Ryanodine receptors on the sarcoplasmic reticulum
What happens when calcium binds to Ryanodine receptors in a cardiac muscle cell?
The channel in the ryanodine receptor opens allowing the release of calcium from the sarcoplasmic reticulum into the cytoplasm
What is Calcium-dependant calcium release?
Calcium causing it own release from the sarcoplasmic reticulum in cardiac muscle cells
What is the source of about 95% of calcium in the cytoplasm in cardiac muscle cells?
The sarcoplasmic reticulum
