Question 1

Type 2X skeletal muscle fibers have fast myosin ATPase activity.

Accepted Answer

Type 2X skeletal muscle fibers, also known as fast glycolytic fibers, have a high myosin ATPase activity which allows for a fast contraction speed. This type of muscle fiber is used for explosive movements such as sprinting or weight-lifting.

Question 2

In cardiac muscle cells,the release of Ca²⁺ through L-type Ca²⁺ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca²⁺ necessary for excitation-contraction coupling.

Accepted Answer

The release of Ca²⁺ through L-type Ca²⁺ channels depolarizes the sarcoplasmic reticulum, triggering the release of additional Ca²⁺ necessary for excitation-contraction coupling in cardiac muscle cells.

Question 3

Compared to type 1,both forms of type 2 muscle fibers usually have a large diameter.

Accepted Answer

Type 2 muscle fibers are typically larger in diameter than type 1 muscle fibers, regardless of whether they are type 2a or type 2x.

Question 4

A lack of ATP in the muscle cell will lead to

Accepted Answer

ATP is required for calcium reuptake into the sarcoplasmic reticulum and for myosin head detachment from actin. Without ATP, calcium accumulates in the cytosol and myosin heads remain bound to actin, causing muscle contraction to persist.

Question 5

You're holding a pose for a photograph.Your cheek muscles fatigue quickly from smiling,meanwhile your neck muscles feel fine from holding your head up.This is because your cheek muscles are predominantly type 2 muscle fibers.

Accepted Answer

Type 2 muscle fibers are associated with quick, intense bursts of activity and tire more easily than type 1 muscle fibers. The muscles in the cheeks are small and not used as frequently as the neck muscles, so they are more likely to be composed mainly of type 2 muscle fibers, which tire quickly.

Question 6

With athletic conditioning,type 2 muscle fibers can gain myoglobin.

Accepted Answer

Athletic conditioning, specifically endurance training, can increase the number and size of type 2 muscle fibers, which can lead to an increase in myoglobin production. Myoglobin is a protein that binds with oxygen in the muscles to provide energy during exercise.

Question 7

Type 2 muscle fibers are generally recruited first during a muscle contraction.

Accepted Answer

Type 1 muscle fibers (slow-twitch) are generally recruited first during a muscle contraction, followed by type 2 muscle fibers (fast-twitch) as the intensity of the contraction increases. This is because type 1 fibers are more resistant to fatigue and are better suited for endurance activities, while type 2 fibers are better suited for short bursts of intense activity.

Question 8

Why does breathing continue to be rapid and deep for a time after heavy exercise?

Accepted Answer

Extra oxygen is needed to restore muscle creatine phosphate concentration and to restore the blood pH to normal after the production of excess lactic acid during the exercise.

Question 9

More mitochondria are typically found in type 1 muscle fibers.

Accepted Answer

Type 1 muscle fibers are also known as slow-twitch fibers and rely heavily on aerobic metabolism to generate energy. This requires a lot of mitochondria, so type 1 fibers have more mitochondria compared to type 2 fibers (fast-twitch fibers).

Question 10

Type 2 muscle fibers typically have the fewer mitochondria than type 1.

Accepted Answer

Type 2 muscle fibers, also known as fast-twitch fibers, are designed for quick and powerful contractions but tire easily compared to type 1 muscle fibers, also known as slow-twitch fibers. Type 2 fibers rely more on anaerobic energy production, meaning they do not require oxygen or mitochondria, compared to type 1 fibers which rely on aerobic energy production, which requires oxygen and many mitochondria. Therefore, type 2 fibers typically have fewer mitochondria than type 1 fibers.

Question 11

You are training for a marathon.As you increase your level of physical fitness,you've noticed that the time spent recovering (breathing heavily after stopping running)is decreasing.What change to your muscle cells might account for this?

Accepted Answer

The answer of You are training for a marathon.As you...

Question 12

More myoglobin is typically found in type 2X skeletal muscle fibers.

Accepted Answer

More myoglobin is typically found in type 1 skeletal muscle fibers, also known as slow-twitch fibers, which are used for endurance activities. Type 2X fibers, also known as fast-twitch glycolytic fibers, have less myoglobin and are used for explosive activities. Type 2A fibers, also known as fast-twitch oxidative fibers, have an intermediate amount of myoglobin.

Question 13

Extracellular calcium plays a role in contraction in

Accepted Answer

Extracellular calcium is required for contraction in both smooth and cardiac muscle cells, but not in skeletal muscle cells, which rely on intracellular calcium release for contraction.

Quiz 9: Muscle