Question

Consider the factors that affect muscular strength. Read each scenario and then identify each label into the appropriate category based on whether each would result in a stronger or weaker muscle contraction.
a. Potassium accumulate in the sarcoplasm
b. Increase in muscle belly circumference
c. Lesser proportion of motor neurons to muscle fibres
d. Begin contractions with muscle already 50% contraction
e. Lower sarcoplasm pH
f. Increased stimulus frequency.
g. Circular arrangement of muscle fascicles
h. increased requirement.

Answer 1

Answer:

1. Weaker contraction:

a. Potassium accumulate in the sarcoplasm

d. Begin contractions with muscle already 50% contraction

e. Lower sarcoplasm pH

g. Circular arrangement of muscle fascicles

2. Stronger Contraction

b. Increase in muscle belly circumference

c. Lesser proportion of motor neurons to muscle fibres

f. Increased stimulus frequency.

h. increased requirement.

Explanation:

Sarcoplasm refers to the cytoplasm of muscle cells which contains ATP, enzymes, and a variety of ions, including potassium (K+). The negative potential required during muscle activity is produced from the disequilibrium of ionic concentrations (mostly Na+ and K+) across the membrane, which is generated through Na+/K+ ATPase pumps. During contraction, a muscle shortens, and thus its circumference increases. The generation of lactic acid is known to lower pH in the sarcoplasm and thus hinder the force and power development of the muscle fibers. Muscle fascicles can be arranged in concentric rings, it is a common pattern in sphincter muscles that modulate the opening and closing of orifices (which have weak contractions). A motor unit refers to a single efferent neuron and all of the muscle fibers it modulates. Each individual muscle fiber is innervated by one motor neuron, whereas a single motor neuron can innervate many muscle fibers. Finally, higher intensity/frequency are known to induce stronger muscular contractions, but also produce a stronger decline in force and cause more rapid muscle fatigue.