Physiology Quiz - Cardiac Conduction

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| By CardioECI517

CardioECI517

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Quizzes Created: 3 | Total Attempts: 14,359

Questions: 6 | Attempts: 1,407 | Updated: Mar 21, 2023

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Questions and Answers

1.

The initial phase of the action potential, associated with the rapid opening of sodium channels is called:
- A.
  
  Plateau
- B.
  
  Initiation
- C.
  
  Depolarization
- D.
  
  Repolarization
Correct Answer
C. Depolarization

Explanation
Depolarization refers to the initial phase of the action potential where the membrane potential becomes less negative or even positive. This is caused by the rapid opening of sodium channels, allowing sodium ions to enter the cell and causing the membrane potential to become more positive. This depolarization phase is essential for the propagation of the action potential along the neuron.

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2.

When ___ concentration rises inside the contractile fiber, contraction of the muscle occurs.
- A.
  
  Potassium
- B.
  
  Sodium
- C.
  
  Chloride
- D.
  
  Calcium
Correct Answer
D. Calcium

Explanation
Calcium is required for muscle contraction. When the concentration of calcium rises inside the contractile fiber, it triggers the release of calcium from the sarcoplasmic reticulum, which then binds to troponin and initiates the sliding of actin and myosin filaments, resulting in muscle contraction. Potassium, sodium, and chloride ions are involved in maintaining the resting membrane potential and action potential in muscle cells, but they do not directly trigger muscle contraction.

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3.

The term that refers to the period when another contraction cannot occur in the muscle is:
- A.
  
  Depolarization
- B.
  
  Tetanus
- C.
  
  Refractory
- D.
  
  Autorhythmic
Correct Answer
C. Refractory

Explanation
During the refractory period, the muscle is unable to generate another contraction. This period occurs immediately after a contraction and is necessary for the muscle to reset and regain its sensitivity to stimuli. This prevents the muscle from contracting again before it has fully relaxed and allows for proper muscle function and coordination.

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4.

All of the following are true about repolarization, EXCEPT:
- A.
  
  Membrane potential returns to resting potential (-90 mV)
- B.
  
  Is associated with potassium outflow
- C.
  
  Occurs before the plateau phase of the action potential
Correct Answer
C. Occurs before the plateau phase of the action potential

Explanation
During repolarization, the membrane potential returns to its resting potential (-90 mV) and is associated with potassium outflow. However, it does not occur before the plateau phase of the action potential.

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5.

The long refractory period characteristic of cardiac muscle contributes to all of the following EXCEPT:
- A.
  
  Tetanus (sustained muscle contraction)
- B.
  
  Allows cardiac muscle to relax before contracting again
- C.
  
  Allows ventricles to fill with blood during relaxation
- D.
  
  Promotes effective blood flow to the body
Correct Answer
A. Tetanus (sustained muscle contraction)

Explanation
The long refractory period characteristic of cardiac muscle prevents tetanus (sustained muscle contraction) from occurring. This is because during the refractory period, the cardiac muscle is unable to respond to another stimulus and therefore cannot sustain a contraction. Instead, it allows the cardiac muscle to relax before contracting again, which is important for proper functioning of the heart. Additionally, the refractory period allows the ventricles to fill with blood during relaxation, promoting effective blood flow to the body.

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6.

The normal path of impulse conduction in the heart is:
- A.
  
  SA node - Purkinje fibers - AV node - AV bundle - bundle branches
- B.
  
  SA node - AV node - Purkinje fibers - AV bundle - bundle branches
- C.
  
  SA node - AV node - bundle branches - AV bundle - Purkinje fibers
- D.
  
  SA node - AV node - AV bundle - bundle branches - Purkinje fibers
Correct Answer
D. SA node - AV node - AV bundle - bundle branches - Purkinje fibers

Explanation
The correct answer is SA node - AV node - AV bundle - bundle branches - Purkinje fibers. This is the normal sequence of impulse conduction in the heart. The SA node (sinoatrial node) initiates the electrical impulse, which then travels to the AV node (atrioventricular node). From the AV node, the impulse is conducted through the AV bundle (bundle of His) and then into the bundle branches. Finally, the impulse spreads through the Purkinje fibers, causing the contraction of the ventricles.

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Physiology Quiz - Cardiac Conduction

The initial phase of the action potential, associated with the rapid opening of sodium channels is called:

When ___ concentration rises inside the contractile fiber, contraction of the muscle occurs.

The term that refers to the period when another contraction cannot occur in the muscle is:

All of the following are true about repolarization, EXCEPT:

The long refractory period characteristic of cardiac muscle contributes to all of the following EXCEPT:

The normal path of impulse conduction in the heart is: