The Heart Lecture 8

1. In a cardiac muscle contraction which process of the heart is rhythmic and spontaneous?

Atrial contraction

Repolarization

Ventricular relaxation

Depolarization

During a cardiac muscle contraction, the process of depolarization is responsible for the rhythmic and spontaneous activity of the heart. This is the electrical process that leads to the contraction of the heart muscle.

Explanation

During a cardiac muscle contraction, the process of depolarization is responsible for the rhythmic and spontaneous activity of the heart. This is the electrical process that leads to the contraction of the heart muscle.

2. What is the main function of gap junctions in the heart?

Produce bile in the liver

Synthesize neurotransmitters in the brain

Regulate blood pressure in the lungs

Ensure the heart contracts as a unit

Gap junctions in the heart allow for direct electrical coupling between cardiac cells, ensuring coordinated contraction of the heart muscle and proper functioning of the heart as a pump.

Explanation

Gap junctions in the heart allow for direct electrical coupling between cardiac cells, ensuring coordinated contraction of the heart muscle and proper functioning of the heart as a pump.

3. In cardiac muscle contraction depolarization opens what?

Ligand-gated Ca2+ channels in the cytoplasm

Voltage gated K+ channels in the sarcolemma

Voltage gated Na+ channels in the sarcolemma

Calcium-gated Na+ channels in the sarcoplasmic reticulum

During cardiac muscle contraction, depolarization opens voltage gated Na+ channels in the sarcolemma, allowing an influx of sodium ions into the cell. This influx of sodium ions is essential for initiating the action potential required for muscle contraction.

Explanation

During cardiac muscle contraction, depolarization opens voltage gated Na+ channels in the sarcolemma, allowing an influx of sodium ions into the cell. This influx of sodium ions is essential for initiating the action potential required for muscle contraction.

4. At what membrane potential does the reversal go from?

-50 mV to +20 mV

-70 mV to +40 mV

-90mv to +30 mv

-60 mV to +10 mV

The reversal of membrane potential refers to the point at which the inside of the cell becomes more positive than the outside. In this case, it goes from -90 mV to +30 mV.

Explanation

The reversal of membrane potential refers to the point at which the inside of the cell becomes more positive than the outside. In this case, it goes from -90 mV to +30 mV.

5. What does depolarization wave in T tubules cause the SR to do?

Release Ca2+

Produce ATP

Take up Ca2+

Store glucose

When a depolarization wave travels through the T tubules, it triggers the sarcoplasmic reticulum (SR) to release Ca2+ ions, which are essential for muscle contraction. This process is crucial for regulating muscle contractions and ensuring proper function.

Explanation

When a depolarization wave travels through the T tubules, it triggers the sarcoplasmic reticulum (SR) to release Ca2+ ions, which are essential for muscle contraction. This process is crucial for regulating muscle contractions and ensuring proper function.

6. In cardiac muscle contraction, what does the depolarization wave do?

Triggers the release of adrenaline

Opens slow Ca2 channels in the sarcolemma

Activates ATP production in the mitochondria

Causes potassium efflux from the cell

During cardiac muscle contraction, the depolarization wave specifically opens slow Ca2+ channels in the sarcolemma, allowing Ca2+ ions to enter the cell and initiate the contraction process.

Explanation

During cardiac muscle contraction, the depolarization wave specifically opens slow Ca2+ channels in the sarcolemma, allowing Ca2+ ions to enter the cell and initiate the contraction process.

7. In cardiac muscle contraction what effect does a Ca2+ surge have?

Shortens depolarization phase

Accelerates repolarization phase

Prolongs depolarization phase (plateau)

Increases resting membrane potential

During cardiac muscle contraction, a Ca2+ surge prolongs the depolarization phase, specifically the plateau phase, allowing for continued contractions to occur.

Explanation

During cardiac muscle contraction, a Ca2+ surge prolongs the depolarization phase, specifically the plateau phase, allowing for continued contractions to occur.