Flashcards in L7: Cardiac Muscle Tissue Deck (19):
What is the basic anatomy of the heart?
Superior vena cava
Pulmonary artery -In Lungs
Out lungs - pulmonary veins
What are characteristics of cardiac muscle tissue?
Sarcomeric arrangement - striated
Cells may branch
What are characteristics of skeletal muscle tissue?
Describe Cardiac T-tubulues and sarcoplasmic reticulum
Found along the Z-line
One cisterna per t-tubule
Form from diads with the SR
Describe skeletal T-tubulues and sarcoplasmic reticulum
Found at the ends of thick flaments
Two cisternae per tubule
Form triads with the SR
Describe fast cardiac action potentials.
Found in atria, ventricles and conduction system
Very rapidly conducting but non-contractile in purkinje fibers
Rapidly conducting and contractile in artial and ventricular fibers
High amplitude 100mV
Describe slow cardiac action potentials.
Found in SA and AV nodal tissues
Automatically depolarizes during resting phase:
-More rapidly in SA node than in AV node
Low amplitude 60mV
Describe the activities that occur during each of the five phases of cardiac muscle action potential.
Phase 4: resting potential
Phase 0: rapid depolarization
Phase 1: initial, incomplete repolarization
Phase 2: plateau or slow decline of membrane potential
Phase 3: repolarization
Compare the physiology of fast and slow cardiac muscle action potentials.
Fast type non-contractile myocytes:
Very large diameter
Very rapid upstroke
Slow type non-contractile myocytes:
Slow rate of depolarization
Explain the role of calcium, sodium, and potassium ions in the creation of the cardiac muscle action potential plateau.
Sodium channels close rapidly, but the calcium channels open slowly and stay open for a longer period of time
There's a delay in the opening of potassium channels
The large concentration of both calcium and potassium is responsible for the plateau
Describe the role of the SA node as the heart's pacemaker.
SA node usually depolarizes more rapidly than the others and reaches threshold first and, by default, becomes the normal "pacemaker" of the heart's rhythmicity.
Compare a sinus rhythm with an ectopic focus.
Generate Sinus: action potentials originating in the SA node
Generate Ectopic Focus (or pacemaker): action potential that originate anywhere else
Describe the mechanism of calcium release during the contraction of a cardiomyocyte
Calcium floods into sarcoplasm and completes electromechanical coupling process
There are fewer calcium release channels in cardiac muscles
Allows fine control over sarcoplasmic calcium concentration and contractility
Calcium enters from extracellular fluid through voltage-dependent calcium channels (DHP on t-tubules)
Elevated levels of calcium trigger more calcium through Ryanodine receptors
What are the two calcium transporters involved in cardiac transport?
Sodium-calcium exchanger in sarcolemma
what is the role of SERCA?
Stimulated by phosphorylation via an integral protein called phospholambian.
When phospholambian is phosphorylated, reduces its ability to inhibit the SERCA pump
Return calcium to the SR during diastole:
Allows for an even greater calcium release the next beat
Also allows for a fast clearance of calcium from the sarcoplasm
what is the role of Sodium-calcium exchanger in sarcolemma.
Transports calcium out of the cell
What is the Frank-Starling law of the heart?
The greater the heart muscle is stretched during filling, the greater the force of contraction and the great the quantity of blood pumped into the aorta
explain how the force of contraction is altered and how this affects stroke volume.
The stretching of the cardiac muscle brings the actin and myosin filaments to a more nearly optimal degree of overlap for force generation