Muscular System

Question 1

What is the area of the sarcomere where only actin is present?

Answer 1

I band

Question 2

What part of the sarcomere shortens during muscle contraction?

Answer 2

The H-zone (which contains only thick filaments) and the I-band (which contains only thin filaments

Question 3

What causes different types of muscle fibers to vary in speed of contraction?

Answer 3

Due to the type of ATPase on their myosin heads, this allows for the hydrolysis of ATP into ADP + P_i and ultimate cross-bridge cycling

Question 4

Hypotonicity

Answer 4

Occurs as a result of damage to the peripheral nervous system and reduced electrolytes which causes muscles to lose tone and thus feel flaccid

Ex: carpal tunnel syndrome - compression of the peripheral never leaves hands feeling weak

Question 5

Hypertonicity

Answer 5

Occurs as a result of damage to the central nervous system and causes muscles to gain tone and thus feel spastic and rigid

Ex: stroke- causes damage to the CNS, causing muscles to feel stiff

Question 6

Contraction phase

Answer 6

Calcium binds to troponin-C, triggering a shape change in troponin that causes it to pull tropomyosin away from actin’s myosin binding site

Cross-bridges are established and the H zone begins to shrink