Heart Lab

Threshold of autorhythmic cell?

-40 mV

What heart cell depolarizes and repolarizes first?

Autorhythmic

Why is this referred to as isovolumetric contraction?

Because semilunar valves are still closed

Why is the timing of depolarization and repolarization is necessary for the autorhythmic cell?

Because the autorhythmic cell is the pacemaker

After the "plateau", what eventually allows repolarization to continue in the contractile cell?

Ca+ channels close while more K+ channels open

What happens to cause depolarization of autorhythmic cell?

Ca+ channels open and calcium rushes in

What happens to cause repolarization of the autorhythmic cell?

Closing of Ca+ and open of K+ channels rapid efflux of K+

What is meant by the membrane potential and what causes it

Concentration of ions

How are heart muscle cells different from other muscle cells in the body?

Contracr automatically without stimulus of the the nervous system

Systole

Contraction

What is the effect of depolarization on contractile cells?

Contraction

What makes the transport channels in the plasma membrane open and close?

Electrical charge

What connects adjacent cardiac cells allowing ions to pass between cells?

Gap junctions

What is the function of the cardiac autorhythmic cells?

Generare action potenial tiggering contrations

In an autorhythmic cardiac cell what generates the pacemaker potential that gets the cell to threshold?

Influx in Na+ and efflux of K*

What initiated the depolarization in a contractile cell?

Influx of Na+ through gap junctions

What is the third phase of the cardiac cycle and when does it occur?

Isovolumetric relaxation and occurs in early diastole

Which channels in the plasma membranes of the autorhythmic cells allow ions to leave?

K+

What two ion channels are opened as a result of sodium influx through fast sodium channels

K+ and Ca+

What ionic pumps are active to restore ion concentrations to their resting conditions?

Na+ -K+ ATPase

What ionic pumps are active during repolarization of an autorhythmic cell?

Na+ -K+ pumps atpase

Which channels in the plasma membranes of the autorhythmic cells allow ions to enter the cell?

Na+ and Ca+

What is the function of calcium ions inside the contractile cells?

Open troponin and tropomysin cover on active sites of actin

What causes complete depolarization in contractile cell?

Rapid influx of sodium through fast voltage gated Na+ channels

Diastole

Relaxation

What is the effect of repolarization on contractile cells?

Relaxation

What cause the movement of blood through ventricular filling?

Relaxation of the right atrium and ventricle

During the first part of ventricular filling the blood moves from the superior and inferior venae cavae into the?

Right atria and then into the right ventricle

What are the contractile units in a cardiac contractile cell?

Sarcomeres

Where are calcium ions stored in the cardiac contractile cell?

Sarcoplasmic reticulum

As ventricles relax which valves close?

Semilunar valves

How does the opening of these ion channels produce the "plateau" in the action potential of a contractile cell?

Slow calcium influx is balanced by decking potassium efflux

As the ventricles begin to contract which heart valves close?

The AV valves

What is the first phase of the cardiac cycle and when does it occur?

Ventricular filming and occurs mid to late diastole

What is the second phase of the cardiac cycle and what events take place in this phase?

Ventricular systole and ventricles contractile and eject blood into aorta and pulmonary trunk

How do action potentials spread from autorhythmic cells to contractile cells?

Via gap junctions

What simulates open of the fast sodium channels in a contractile cell?

Voltage change in sarcolema due to influx of Na+ through gap junctions