Practice Questsions 1

What does the sarcoplasmic reticulum store that is significant for muscular contraction?

Calcium ions

What cardiac phase is represented by diastole?

Diastole is the phase of the cardiac cycle where relaxation of the ventricles and atria allows for the heart to fill with blood.

What is the name of the most external layer of a single muscle fiber?

Endomysium The endomysium encapsulates each individual muscle fiber. The perimysium is a layer of connective tissue that groups individual muscle fibers into fascicles. The epimysium is a sheath of dense connective tissue that covers the entire muscle, including the perimysium and endomysium, and is continuous with the fascia.

Where are the contractile proteins in striated muscle located?

Sarcomere

Where in a muscle are essential elements of muscular contraction (i.e., glycogen, fat, mitochondria) located?

Sarcoplasm The sarcoplasm functions similarly to cytoplasm in other organisms and serves as the primary storage site for glycogen, fats, mitochondria, etc. The sarcoplasm of a muscle fiber is analogous to the cytoplasm of other organisms, as this is where essential elements of muscular contraction are located, such as glycogen, fat, various enzymes, mitochondria, and the sarcoplasmic reticulum.

What is the proper orientation for blood pressure notation, and what is considered normal blood pressure?

Systole/Diastole; 120/80

What connective tissue attaches a muscle to a bone?

Tendon

The sarcolemma in striated muscle tissue plays a significant role in muscular contraction. What is the primary function of the sarcolemma?

The primary function of the sarcolemma is to conduct electrical signals, via transduction, signaling the release of Ca2+ ions.

What anatomical structure is considered to be the "pacemaker" of the heart?

The sinoatrial node serves as the electrical-impulse-generating tissue of the heart, is commonly referred to as the pacemaker, and is located in the right atrium. The sinoatrial node establishes the normal heart rhythm, which is referred to as the sinus rhythm.

What is the all-or-nothing principle of muscular contraction?

This principle refers to the complete muscular contraction that takes place after an action potential has been released onto the sarcolemma of the muscle. If no action potential is present, then there is no contraction.

What protein is responsible for initiating muscular contraction?

Troponin is the protein responsible for initiating muscular contraction, as this is the location where actin and myosin sites bind forming the crossbridges necessary for contraction to occur. Calcium ions are responsible for initiating the movement of troponin from the myosin binding site, initiating a conformational change. Once this takes place, the myosin crossbridge can be carried out and muscular contraction can occur.

What muscle fiber type has the greatest capacity for force production and hypertrophy?

Type IIb fibers are considered "fast" glycolytic, produce large amounts of force, and possess the greatest capacity for hypertrophy. Type IIb fibers primarily function in high-force, explosive-type movements because of the force generation capacities they possess. This fiber has very little involvement in moderate duration movements past the initial effort, usually 5-8 seconds, and very little to no impact on sustained muscular contractions and endurance-related efforts.

During muscular contraction, which section of the sarcomere does not move?

A-band The A-band is the segment where both actin and myosin filaments are located. The A-band does not move during muscular contraction, while the I-bands and H-zones shorten. The H-zone is a part of the A-band located in the center of the sarcomere where only myosin filaments occur. The I-band is an area that only consists of thin filaments, and is made up of two contiguous sarcomeres. The Z-line occurs in the middle of the I-band and appears as a line running lengthwise throughout.

What substance is involved in muscular contraction at the neuromuscular junction?

Acetylcholine Acetylcholine is the neurotransmitter responsible for inducing the release of sodium ions into the muscle cell that result in muscular contraction. Acetylcholine must accumulate in sufficient amounts at the neuromuscular junction in order for an action potential to be released onto the sarcolemma, resulting in a muscular contraction.

During muscular contraction, two specific proteins form a crossbridge that generates movement. What are these two proteins called, and for what action during the crossbridge formation are they individually responsible?

Actin is the thin filament and serves as the binding site. Myosin is the thicker filament and forms the crosslink to the actin filament.