Cardiac Muscle Cell Contractions

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What happens to the impulses that originate at the SA node during atrial contraction?

They are blocked by the atrioventricular node

They are delayed for about 0.1 second before spreading to the heart apex (correct)

They are conducted directly to the ventricular walls

They are transmitted directly to the Purkinje fibers

What is the function of the bundle branches and Purkinje fibers?

To conduct signals from the AV node to the ventricular walls (correct)

To secrete hormones that influence the pacemaker

To regulate the pace of the SA node

To detect changes in body temperature

What is the role of the parasympathetic division in regulating heart tempo?

It has no effect on the pacemaker

It slows down the pacemaker (correct)

It increases the force of contraction

It speeds up the pacemaker

What is the effect of an increase in body temperature on heart rate?

It increases heart rate by about 10 beats per minute Signup and view all the answers

What is the role of epinephrine in regulating heart rate?

It speeds up the pacemaker Signup and view all the answers

What happens to the atria during atrial contraction?

They contract in unison Signup and view all the answers

What is a characteristic of some cardiac muscle cells?

They can contract and relax repeatedly without any signal from the nervous system Signup and view all the answers

Where is the pacemaker located in vertebrates?

In the wall of the right atrium, near where the superior vena cava enters the heart Signup and view all the answers

What is the function of the sinoatrial node?

To set the rate and timing of cardiac muscle cell contractions Signup and view all the answers

What is the purpose of an electrocardiogram (ECG or EKG)?

To measure the electrical activity of the heart Signup and view all the answers

What is special about the impulses produced by the sinoatrial node?

They are similar to those produced by nerve cells Signup and view all the answers

What is the term for the cluster of autorhythmic cells that sets the rate and timing of cardiac muscle cell contractions?

Sinoatrial node Signup and view all the answers

Where in the heart does the heartbeat originate?

In the cardiac muscle cells Signup and view all the answers

What allows impulses from the SA node to spread rapidly within heart tissue?

Gap junctions Signup and view all the answers

What is recorded by electrodes placed on the skin in an electrocardiogram?

Electrical currents Signup and view all the answers

What is the shape of the graph representing the stages in the cardiac cycle?

Complex waveform Signup and view all the answers

What is unique about the rhythmic contractions of autorhythmic cardiac muscle cells?

They can contract and relax repeatedly without any signal Signup and view all the answers

In which vertebrates is the pacemaker located in the nervous system?

Arthropods Signup and view all the answers

What is the primary function of the AV node?

To delay the impulses from the SA node Signup and view all the answers

What happens to the heart rate when the body temperature increases?

It increases by about 10 beats per minute for every 1°C increase Signup and view all the answers

What is the primary function of the bundle branches and Purkinje fibers?

To conduct signals from the AV node to the ventricular walls Signup and view all the answers

Cardiac Muscle Cell Contractions

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