Exam 2: Lecture 18 Flashcards
What is defined in cardiac muscle translates the AP into the production of tension
excitation-coupling
Where is the cardiac AP initiated in the heart and causes depolarization to spread to the interior of the cell via T tubules
myocardial cells
What is defined as the inwards current of Ca2+ which allows Ca2+ to move through L-type channels from ECF to ICF
Plateau
How does Ca2+ become released from the SR
ryanodine receptors
What troponin subtype allows Ca2+ to bind and the interaction of actin and myosin can occur
troponin C
what is defined as the intrinsic ability of myocardial cells to develop force at a given muscle cell length
contractility or inotropism
Agents that produce a increase in contractality are said to have a + or - inotropic effects
+
+ or - inotropic effects increase both the rate of tension development and the peak tension
+
Agents that produce a decrease in contractality are said to have a + or - inotropic effect
-
+ or - inotropic effects decrease both the rate of tension development and the peak tension
-
stimulation of the (SNS or PNS) and circulating catecholamines have a + inotropic effect
SNS
Stimulation of the (SNS or PNS) and ACh have a - inotropic effect
PNS
What organ does the SNS and circulating catecholamines act on
myocardium
What organ does the PNS and Ach act on
atria
When you have an increase in HR does it make contractality stronger or weaker
stronger
What is positive staircase effect
Bowditch staircase. When HR doubles for example, the tension developed on each beat increases in a stepwise fashion to a maximal value
- increase happens because there is more AP per unit time bc more Ca2+ entering the cell during plateau phases and more Ca2+ gets into the SR
What is defined as when an extrasystole occurs (anomalous extra beat generated by a latent pacemaker)
- the tension developed on the next beat is greater than normal
Postextrasystole Potentiation
What plant acts as a positive inotropic agent. the prototype drug is digoxin
Foxglove plant - digitalis purpurea
What inhibits Na+/K+ ATPase at the extracellular K+ binding site
Cardiac Glycolysis
When Na+/K+ ATPase is inhibited, less Na+ is pumped out of the cell, increasing the intracellular _______ concentration
Na+
The increase in intracellular Na+ concentration alters the Na+ gradient across the myocardial cell membrane, altering the function of what exchanger
Ca2+ / Na+
As less _______ is pumped out of the cell by the Ca2+ / Na+ exchanger, the intracellular Ca2+ concentration increases
Ca2+