L7: Cardiac Muscle Tissue Flashcards Preview

Physiology I - EXAM 1 > L7: Cardiac Muscle Tissue > Flashcards

Flashcards in L7: Cardiac Muscle Tissue Deck (19):

What is the basic anatomy of the heart?

Superior vena cava
Right atrium
Tricuspid valve
Right ventricle
Pulmonary valve
Pulmonary artery -In Lungs
Out lungs - pulmonary veins
Left atrium
Mitral valve
Left ventricle
Aortic valve


What are characteristics of cardiac muscle tissue?

Sarcomeric arrangement - striated
Central nuclei
Intercalated discs
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

Sarcoplasmic reticulum:
Less extensive


Describe skeletal T-tubulues and sarcoplasmic reticulum

Found at the ends of thick flaments
Two cisternae per tubule
Form triads with the SR

Sarcoplasmic reticulum:
More extensive


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
Conducts slowly
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:
Small diameter
Low amplitude
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


Describe forces altering flow and velocity and describe how the heart controls the flow of blood through the chambers.

The rate of blood flow to each tissue is precisely controlled in relation to tissue need
Active tissues may need 20 to 30 times as much blood flow than at rest
Cardiac output cannot exceed 4-7 times great than at rest
Microvessels of each tissue monitor tissue needs
Needs of tissues act directly on local blood vessels
Nervous control and hormones also help control tissue blood flow