BMS 450 Lecture Notes - Cardiac Action Potential, Vascular Resistance, Sodium Channel
Document Summary
Vasoconstrictors cause calcium levels to rise contraction, raises peripheral resistance, raises blood pressure. The heart contracts sequentially (atria and then ventricles) and in a synchronized manner. This is accomplished by an electrical conduction system that allows rapid and organized spread of electrical excitation. Electrical excitation is converted into mechanical energy (i. e. contraction) Moves slowly through the atrioventricular (av) node to the ventricles. Spreads rapidly throughout the ventricles via the his-purkinje system. Electrical current spreads from one cell to another via gap junctions. Arises from diverse populations of ion channels throughout the heart. Different cardiac cell types have different populations of ion channels. Different cardiac cell types have different electrical properties. Initiation of contraction, k+ exits the cell also. The distribution of positive and negative ions is unequal. At rest, the interior of the cell is negative (-90 mv) with respect to the exterior. Electrical and chemical forces cause charged ions to move in or out of the cell.
