Term
| What is the mechanism by which the individual muscle cells of the heart function as if they were a single unit, all undergoing synchronous electrical and mechanical activity? |
|
Definition
| Cardiac muscles are joined by gap junctions that permit the conduction of action potentials from cell to cell. |
|
|
Term
| How does a cardiac muscle cell differ from skeletal and smooth muscle fibers with respect to producing a graded twitch strength? |
|
Definition
| Cardiac contractions are slow twitch. Skeletal contractions are fast-slow. Smooth muscle contractions are very slow. |
|
|
Term
| How does excitation-coupling in a cardiac muscle cell differ from that in a skeletal and smooth muscle fiber? |
|
Definition
| Depolarization due to influx of calcium ions through voltage gated channels (L type calcium channels which are modified versions of the DHP receptors in skeletal muscle) Instead of being open directly by voltage as in skeletal, cardiac are opened by binding of trigger calcium in cytosol. Unlike skeletal, process is dependent upon movement of extracellular calcium in cytosol (even though most calcium initiating contraction comes from sarcoplasmic reticulum) cardiac are graded like smooth muscle contraction. Unlike skeletal, action potential is brief and force generation is much longer. |
|
|
Term
|
Definition
| Recording at skin surface of the electrical currents generated by cardiac muscle action potentials. |
|
|
Term
| Positive Inotropic effect |
|
Definition
| Increased force has an effect on contractile cells, Beta-1 effect on G protein and cAMP. Activated protein kinase which increases calcium ion from ECF and amount in sarcoplasmic reticulum released by trigger calcium to move free cytosol calcium ion for a stronger contraction. |
|
|
Term
| Negative chronotropic effect |
|
Definition
| Decreased rate which increases membrane potassium permeability in conductile tissues. More potassium ion is able to leave, cell is more negative and takes longer for SA cells to reach threshold and heartrate slows. |
|
|
Term
|
Definition
| Period of cardiac cycle when ventricles are relaxing |
|
|
Term
|
Definition
| Period of ventricular contraction |
|
|
Term
| End-diastolic volume (EDV) |
|
Definition
| amount of blood in ventricle just prior to systole |
|
|
Term
| End-systolic volume (ESV) |
|
Definition
| amaount of blood remaining after ejection |
|
|
Term
|
Definition
| the volume of blood ejected from each ventricle during systole |
|
|
Term
|
Definition
| blood volume pumped by each ventricle per minute (not total output pumped by both ventricles) |
|
|
Term
|
Definition
|
|
Term
|
Definition
| slow, decreased heart rate |
|
|
Term
|
Definition
| changes in the end-diastolic volume in the ventricles just before contraction |
|
|
Term
|
Definition
| the work the heart does while ejecting blood. A function of arterial blood pressure as well as the diameter and thickness of the ventricles. |
|
|
Term
|
Definition
| the ratio of stroke volume to end-diastolic volume EF=SV/EDV |
|
|
Term
|
Definition
|
|
Term
|
Definition
| ventricular depolarization. Masks atrial repolarization. |
|
|
Term
|
Definition
| Reflects slow wave of conduction through AV node |
|
|
Term
|
Definition
| ventricular repolarization |
|
|
Term
| Where is the myocardium found? |
|
Definition
| Middle layer of cardiac muscle which forms the heart wall |
|
|
Term
| Where is the endocardium found? |
|
Definition
| Inner layer of endothelial cells |
|
|
Term
| Where is the epicardium found? |
|
Definition
| Outer layer of endothelial cells |
|
|
Term
| Where is the pericardium found? |
|
Definition
| Connective tissue surrounding the heart. |
|
|
Term
| What is the functions do the papillary muscles and chordate tendinae serve? |
|
Definition
| Prevent backflow of blood during ventricular contraction. |
|
|
Term
| What function do the atria serve? |
|
Definition
| Atria receives blood from veins and passes it on to ventricle on same side of heart using pressure differences as force. |
|
|
Term
| From where do the cells of the myocardium and epicardium receive oxygen and glucose? |
|
Definition
| Via coronary arteries blood supply |
|
|
Term
| How do action potentials recorded from contractile heart cells differ from action potentials recorded from conductile heart cells? |
|
Definition
| Conductile cells have a pre potential, a more gradually developing phase D (depolarization), no phase 1 (sodium channel closes, sodium pump speeds) and a blending of phases 2 (pleateau) and 3 (repolarization) compared to contractile. |
|
|
Term
| What ionic events are responsible for how actino potentials are recorded from contractile heart cells differ from action potentials recorded from conductile heart cells? |
|
Definition
| Prepotential of conductile is from less potassium leakage and more retained in cell. |
|
|
Term
| Do contractile or conductile heart cells have pacemaker potentials? |
|
Definition
|
|
Term
| What is the function of the SA node? |
|
Definition
| Pacemaker for the entire heart. Its depolarization generates action potential that leads to depolarization of all other cardiac muscle cells. (Its discharge rate determines heart rate) |
|
|
Term
| What is the function of Atrial impulses? |
|
Definition
| Trigger discharge of AV node during AV relative refractory period. |
|
|
Term
| What is the function of AV node? |
|
Definition
| The link between atrial depolarization and ventricular depolarization. Conducts slowly allowing time for erection blood from atria to ventricles. |
|
|
Term
| What is the function of Bundle of HIS? |
|
Definition
| Carries electrical impulses from AV node down the interventricular septum. |
|
|
Term
| What is the function of the Purkinje system? |
|
Definition
| Distributes impulse to ventricular contractile cells. |
|
|
Term
| What is the function of ventricular muscles? |
|
Definition
| Where the conduction of impulse occurs by ephaptic conduction or gap junctions. |
|
|
Term
| How does the regulation of the strength of contraction of a cardiac muscle cell compare to that of a skeletal or smooth muscle cell? |
|
Definition
| Strength and frequency are modulated by neurotransmitters and hormones. Cardiac muscle has trigger calcium which releases more calcium from sarcoplasmic reticulum? |
|
|
Term
| What is a cardiac pacemaker potential? |
|
Definition
| Spontaneous gradual depolarization to threshold of some nerve and muscle cells' plasma membrane. |
|
|
Term
| How is a cardiac pacemaker potential generated? |
|
Definition
| By potassium leakage out of cell decreasing and therefore more potassium is retained in the cell. Voltage gated sodium channels open and sodium enters the cell and calcium T channels open causing calcium ion to enter. |
|
|
Term
| How does the stroke volume of the left ventricle compare to that of the right ventricle? |
|
Definition
| Identical despite the right ventricle's lower pressure during contraction. |
|
|
Term
| When the heart rate is slowed from 70 beats per minute to 40, how much does the duration of systole change? |
|
Definition
|
|
Term
| When the heart rate is slowed from 70 beats per minute to 40, how much does the duration of diastole change? |
|
Definition
|
|
Term
| When the heart rate is increased from 70 beats per minute to 100, how much does the duration of systole change? |
|
Definition
|
|
Term
| When heart rate is increased from 70 beats per minute to 100, how much does the duration of diastole change? |
|
Definition
|
|
Term
| What is the name of the parasympathetic nerve which innervates the heart? |
|
Definition
|
|
Term
| What is the mechanism by which muscarinic (parasympathetic) stimulation slows the heart? |
|
Definition
| The slope of the pacemaker potential decreases due to a reduction in the inward current. Threshold is reached more slowly and heart rate decreases. |
|
|
Term
| What is the mechanism by which beta one (sympathetic) stimulation increases heart rate? |
|
Definition
| Increases the slope of pacemaker potential by increasing F-type channel permeability. Main current is sodium entering cell and further depolarization results. this causes SA node cells to reach threshold more rapidly and heart rate increases. |
|
|
Term
| How does the body vary cardiac output? |
|
Definition
| Control of heart rate and control of stroke volume. |
|
|
Term
| How does the Frank-Starling relationship compare to a positive or negative inotropic action in influencing cardiac stroke volume? |
|
Definition
| Increased end disastolic volume creates greater stretch and a more forceful contraction. The greater filling will increase the force of contraction. The sympathetic tone remains constant. Autonomic influences an ionotrophy relate Beta 1 receptor activity and is independent of end diastolic volume. |
|
|
Term
| What are the functions of desmosomes and gap junctions between myocardial cells? |
|
Definition
| Desmosomes and gap junctions allow positive ions to depolarize adjacent contractile cells and conductile system and overall allows simultaneous (choreographed) contractions. It spreads the action potential from one cell to another. |
|
|
Term
| What ion is responsible for the deopolarization of myocardial contractile cells? |
|
Definition
| Voltage gated sodium channels |
|
|
Term
| What ion is responsible for the depolarization of myocardial conductile cells? |
|
Definition
| L voltage gated calcium channels |
|
|
