Term
| What are the 3 major types of cardiac cells? |
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Definition
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Contractile; Conductile; Pacemaker (Nodal)
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Term
| Contractile Cardiac Cells- Location and Function |
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Definition
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Ventricles and Atria of the heart- Major function is contraction (pumping)
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Term
| Conductile Cardiac Cells- Location and Function |
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Definition
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Purkinje Fibers- Major function is the rapid spread of electrical signals
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Term
| Pacemaker Cardiac Cells- Location and Function |
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Definition
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SA and AV Nodes- Major function is pacemaker activity
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Term
| Of the 3 major types of cardiac cells, which 2 have FAST action potentials? |
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Definition
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Contracile and Conductile Cells
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Term
| What is the major difference between action potentials in a ventricular muscle versus a sinoatrial pacemaker cell? |
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Definition
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There is the presence of the pacemaker potential in the SA node cell versus a resting membrane potential in ventricular cells
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Term
| Describe Phase 0 of a Ventricular Action Potential |
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Definition
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Depolarization: UPSTROKE of an action potential via the fast inward current of Na+
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Term
| Describe Phase 1 of a Ventricular Action Potential |
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Definition
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Early Repolarization: K+ begins to move out of the cell when some transient K+ channels are activated
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Term
| Describe Phase 2 of a Ventricular Action Potential |
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Definition
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Plateau Phase: A very long action potential occurs due to the balance between the inward current of Ca2+ and the outward current of K+
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Term
| Describe Phase 3 of a Ventricular Action Potential |
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Definition
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Repolarization: Ca2+ current stops, while K+ current increases
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Term
| Describe Phase 4 of a Ventricular Action Potential |
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Definition
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Resting Potential: due to large background current of K+
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Term
| Absolute Refractory Period |
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Definition
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Closed Na+ channels are inactive, causing the cell to be refractory to firing another action potential
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Term
| How long does the Absolute Refractory Period last? |
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Definition
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From Phase 0 to half- way through Phase 3, where the membrane potential reaches about -50 mV
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Term
| Relative Refractory Period |
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Definition
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Na+ channels begin to open and activate, supporting the upstroke at Phase 0 while decreasing the stimulus size for a second action potential
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Term
| When does the Relative Refractory Period occur? |
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Definition
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When all the Na+ channels have recovered; Approximately when phase 3 repolarization is complete
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Term
| Can cardiac muscle become tetanized? Why or why not? Is this good or bad? |
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Definition
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Cardiac muscle CANNOT become tetanized due to the long refractory period; This is good for cardiac muscle because it protects the muscle from abnormal cramping or contraction
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Term
| What kind of "potential" is characteristic of action potentials from Nodal Cells? What is the range of this potential? |
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Definition
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Maximum diastolic potential; -65 to -55 mV
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Term
| Describe Phase 0 of a Sinoatrial Node Action Potential |
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Definition
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Upstroke: due to inward current of Ca2+ (NOTE: Calcium- dependent upstroke, NOT Sodium- dependent upstroke seen in ventricular AP's)
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Term
| Describe Phase 3 of a Sinoatrial Node Action Potential |
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Definition
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Repolarization: due to uutward current of K+
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Term
| Describe Phase 4 of a Sionatrial Node Action Potential |
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Definition
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Pacemaker Potential: due to reduced outward current of K+, increased inward current of Na+ (funny current), and development of transient inward Ca2+ current
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Term
| "Funny current"- Direction and Polarization |
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Definition
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Inward current; Depolarizing via Na+ and K+
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Term
| Transient Ca2+ current- Direction and Polarization |
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Definition
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Inward current; Depolarizing
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Term
| Long- Lasting Ca2+ current- Direction and Polarization |
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Definition
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Inward current; Depolarizing
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Term
| Delayed Rectifier current- Direction and Polarization |
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Definition
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Outward current; Repolarizing
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Term
| In what 2 ways is cardiac contraction regulated? |
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Definition
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Alterations in fiber length and Changes in contractility
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Term
| True or False: Cardiac Muscle exhibits summation, but not recruitment |
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Definition
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FALSE; Neither summation nor recruitment occur in cardiac muscle
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Term
| Define Cardiac Contractility |
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Definition
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The property of cardiac muscle to alter its tension development independent of fiber length
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Term
| What is a positive inotropic effect? |
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Definition
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An INCREASE in contractility which involves an in increase in both the amount of tension developed and the rate in which that tension develops
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Term
| What is a negative inotropic effect? |
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Definition
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A decrease in tension development and a decrease in the rate of tension development at a given fiber length
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