Chapter 9 Cardiac Physiology Flashcards
Circulatory System
the body’s transport system consisting of heart, blood vessels, and blood
Pulmonary circulation
Sending blood depleted into O2 and rich in CO2 to the lungs and returns blood rich in O2 and depleted in CO2 to the heart
Systemic circulation
Sends blood rich in O2 and depleted in CO2 to the whole body and returns blood depleted in O2 and rich in CO2 to the heart
Blood circulation
Right atrium, right ventricle, pulmonary trunk, pulmonary arteries, lungs, pulmonary veins, left atrium, left ventricle, aorta, whole body
What prevents the atrioventricular valves from everting?
By one way valves, they have chordae tendineae attached to papillary muscles
What is the fibrous skeleton?
Dense connective tissue that surrounds and stabilizes position of four valves
What are the three tissue layers of the heart?
Endothelium, myocardium, and epicardium
What is the pericardial sac?
A tough fibrous outer covering that attaches to connective tissue in thoracic cavity and anchors the heart in place.
What are some commonalities between cardiac and skeletal muscle fibers?
-They are striated (layers of thick and thin filaments)
-They contract via Ca2+ binding to troponin
Intercalated disks contain what
Desmosomes (strongest cell junction) and Gap Junctions (allows action potentials to travel from one fiber to another)
Differences between cardiac and skeletal muscle fibers?
- Contain many mitochondria (for oxidative phosphorylation)
-short and slender and arranged like a spiral
-they branch out and connect end-to end called intercalated disks
Functional Syncytium
When all the cardiac muscle fibers contract together as one
Two types of cardiac muscle cells
-Contractile cells- receive electrical current and provide the actual contractile force
-Autorhythmic cells- initiate the action potentials
Do autorhythmic cells require nervous system input to fire action potentials?
No
What is the potential between action potentials called?
pacemaker potential
What is the weird thing about Na+ funny channels?
They open with hyperpolarization
Are autorhythmic cells spread out homogenously throughout the heart? If not, where are they located?
Concentrated in specific sites such as the SA node, AV node, Bundle of his, and the purkinje fibers
Why does the rhythm of the sinoatrial node drive the rest of the autorhythmic cells?
They are all connected to each other via gap junctions and the area with the highest bpm which is the SA node and that controls the rhythm.
Do the atria contract at the same time as the ventricles? Why or why not?
No, the left and right atria contract together then after the ventricles contract together ensuring synchronous flow between pulmonary & systemic circulation loops
Do contractile cells have a pacemaker potential? Which cell causes it to fire an action potential?
No, autorhythmic cells are what sends the action potential signal to the contractile cells
Opening of which channel causes action potentials in contractiles cells to be so long in duration?
A slow, L-type Ca2+ channel
How does the long-duration action potential in a contractile cell affect the contractile response?
Leads to increased duration of cardiac muscle fiber contraction (~3 times longer than skeletal)
Does twitch summation occur in cardiac muscle fibers?
No
Where is an ECG measured? What are the three main components of an ECG? What underlying cardiac events cause each component?
- Measured at skin surface arising from summed electrical activity of cardiac muscle fibers
- P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization)
