Which of the following channels is responsible for generating the long plateau found in the action potentials of ventricular myocytes?   a-slow Na+ channels b-slow Ca2+ channels c-leaky Ca2+ channels d-leaky Na+ channels

the herbal supplements bitter orange, also known as synephrine, mimics the effects of neurotransmitters on the SNS on the heart and blood vessels serving the abdominal viscera and skin. what effect do you think this would have on the blood pressure? Considering this, do you think this drug should be given to people with hypertension (high blood pressure)?

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

The cardiac action potential is substantially longer than a neuron potential due to: spontaneous depolarization Ca++ entry gap junctions myocardial contractility

A 28-year-old athlete is noted to have a baseline heart rate of 55bpm, which his trainer attributes to excellent parasympathetic (vagal) tone. This parasympathetic effect normally increases Ach release at the SA and AV nodes. Ach release into AV node leads to which of the following effects of its fibers? a. increased action potential amplitudeb. increased conduction velocityc. increased K+ equilibrium potentiald. Hyperpolarizatione. increased rate of depolarization of the pacemaker potential

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.

(please type answer).

Describe the movement in ions in action potentials of these cells - pacemaker cell - cardiac contractile cell

during isometric ventricular contraction: a. the entry and exit valves of the ventricle are closedb. pressure in the aorta arisesc. pressure in the atria fallsd. the rate of rise in pressure is greater in the right than in the left ventriclee. volume of the ventricle increases

As blood in the great arteries ricochets back against the closed semilunar valves, the second heart sound ("dupp") can be heard. Why does this heart sound occur towards the end of the T wave in an ECG?