1. The loss of actin from striated muscle would... A. not prevent sarcomeres fro
ID: 64903 • Letter: 1
Question
1. The loss of actin from striated muscle would...
A. not prevent sarcomeres from generation tension in a non-crossbridge manner
B. prevent the msucle from recoiling to its resting length after stretching
C. increase the ability of the sarcomere to generate force
D. prevent the muscle from stretching past its resting length
E. prevent crossbridge formation and tension development
2. An elasmobranch is an..., which is reflected in its kidney which...
A. osmoconformer...has no loop of henle
B. osmoregulator...has no loop of henle
C. osmoconformer...has no proximal convoluted tubule
D. osmoconformer...has a loop of henle
E. osmoconfermer...has no filtration barrier
3. In striated muscle the loss of tropomyosin...
A. would increase influx of calcium into sarcomere
B. Allow crossbridges to form in absence of Calcium
C. Decrease the tension-length curve
D. Prevent calcium-activation of muscle
E. would prevent actin-myosin corssbrdige formation
4. How is possible for insects to beat their ings at up to 1,000/s
A. They rely on the elastic recoil of the thorac to help wings beat
B. Their striated muscle is not activated externally by nuerons as is striated muscle in other animals
C. The have very unusual neurons that can fire at rates >2,000 times a second
D. They have a unique striated muscle that is not activated in the same way as vertebrate striated muscle
5. If the maximal intersitial osmolarity around a nephron is 1500 mOsm/L what is the maximal urine osmolarity that can be produced by the nephron (answer in mOsm/L)
A. 3000
B. 300
C. 900
D. 1500
E. Cant be determined
6. What would not affect osmolarity if added to water
A. additional water
B. CO2
C. NaCl
D. H+
E. Sand
Explanation / Answer
1. E. prevent crossbridge formation and tension development
Myofilaments are arranged parallel in the sarcoplasm; they run along the entire length of the muscle fibre. A huge portion of the sarcoplasm is occupied by these filaments. The myofilaments are composed of two types of proteins called actin and myosin, which are responsible for the contractility of myofibrils. Actin and myosin filaments are the structural components of sarcomere, which is the actual contractile part of the muscle.
Myosin filaments are thick and actin filaments are thin. The longitudinal striations of skeletal muscles are due the presence of myofilaments of different thickness. During muscle contraction, cross bridges are formed between these filaments and myosin slides over the stationary actin filament.
Thus, the loss of actin from striated muscle would prevent crossbridge formation and tension development.
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