Which of the following is TRUE about action potentials in pacemaker cardiac cells? Select all that apply Group of answer choices They rely on calcium influx for depolarization They have a resting membrane potential of -90 mV They rely on sodium influx for depolarization They display a prolonged plateau phase

which of the following conditions at the S-A node will cause a decrease in heart rate? increased sodium permeability decreased acetylcholin levelsincreased norepinephrine levels increased potassium permeabilityincreased calcium permeability

The force of contraction can be changed by: can choose more than on e Group of answer choices - muscarinic ACh receptors.  Activation of the receptors leads to decreased Ca2+ entry and increased K+ entry in ventricles.     - Beta2 adrenergic receptors.  Increasing cAMP leads to increases in PKA, which increases sarcoplasmic calcium by opening VG Ca+ channels for a longer time, opening SR Ca2+ channels, and increasing the rate of Ca2+ removed by SERCA pumps.   - Beta1 adrenergic receptors.  Increasing cAMP leads to increases in PKA, which increases sarcoplasmic calcium by opening VG Ca+ channels for a longer time, opening SR Ca2+ channels, and increasing the rate of Ca2+ removed by SERCA pumps.   - Not by the parasympathetic NS. (at least, not the ventricles).

Hypertension increases afterload for the heart which in turn   a-decreases Stroke Volume b-increases Stroke Volume c-increases Cardiac Output d-increases Venous Return

The entry of calcium into a ventricular muscle cell helps to maintain depolarization of the membrane during the plateau phase of the action potential, but this calcium also performs what other function?

Which of the following are false about the inward rectifier? OA The inward rectifier current is carried by potassium OB. The inward rectifier carries inward current at potentials negative to the Nersnst potential for potassium under voltage clamp conditions. OC. The inward rectifier current obeys Ohm's law. OD. The inward rectifier is absent in the sino-atrial node. OE All of the above are true.

The role of calcium currents in cardiac contractile cells is to .  The role of calcium currents in cardiac conductive cells is to .    Choose between: release neurotransmitter, bring the membrane potential to threshold, initiate action potential, prolong action potential, terminate action potential

Which of the following combinations would have OPPOSITE effects in changing heart rate? atropine and norepinephrine atropine and a cholinesterase inhibitor epinephrine and norepinephrine acetylcholine and a cholinesterase inhibitor

Sympathetic stimulation increases the phosphorylation of the Ca2+ATPase in the sarcoplasmic reticulum. What effect does this have on cardiac function? It increases the rate of diastole  It decreases the stretch of the ventricles The rate of systole decreases

Which of the following statements best describes the differences in the regulation of cardiac and skeletal muscle contraction?     The amount of contractile force actively generated by muscle cells is increased by stretch in skeletal muscle and decreased by stretch in cardiac muscle.     Cardiac muscle is stimulated by motor neurons and skeletal muscle by neurones from the autonomic nervous system.     Skeletal muscle contractile force is augmented by increasing the firing frequency of action potentials whereas cardiac muscle contractile force is enhanced by noradrenaline increasing calcium influx through ion channels.     Ryanodine receptors in skeletal muscle are opened by a mechanism that requires calcium influx whereas in cardiac muscle membrane depolarisation alone without calcium influx is sufficient to open ryanodine receptors.