Terms in this set (26)
Skeletal muscle fibers develop from undifferentiated cells called
A contraction where the tension in the muscle is greater than the load it is trying to move would be
B. isotonic contraction
Which of these fibers is the largest?
Smooth muscle contractions can be initiated by
A, B, & C
neural input causing an action potential
pacemaker potentials that cause an action potential
mechano-sensitive ion channels
Which of these fibers has the weakest contractions but has the longest endurance?
Multi-unit smooth muscle contractions
A. are possible because each muscle cell contraction is started by a neuron
During the relaxation period
B. calcium pumps return Ca2+ into the sarcoplasmic reticulum
In the process of skeletal muscle hypertrophy, there can be an
D. A & B
addition of glycolytic enzymes
addition of myofibrils
Which of the following would not be found in a skeletal muscle neuromuscular junction
E. all of the above would be found in the skeletal muscle neuromuscular junction
Which of the following could be found in smooth muscle tissue but not in skeletal muscle tissue
D. gap junctions
Which of these types of muscle tissue do not show striations (alternating light and dark bands)?
If an adult skeletal muscle has undergone a small degree of atrophy, some new muscle fibers can develop from
C. undifferentiated satellite cells
The globular heads of a myosin molecule have binding sites for
D. A & B
The troponin complex on an actin filament contains three individual proteins. The Trop-I has a binding site for which of the following?
The motor neurons that innervate skeletal muscle cells
D. A & B
are always cholinergic
are always myelinated
A motor unit
D. A & B
can consist of one motor neuron aon 2 muscle fibers
can consist of one motor neuron on 150 muscle fibers
Skeletal muscle contractions are a result of a signal transduction pathway that begins at the motor end plate. How is this signal transduction pathways ultimately stopped?
C. By the action of acetylcholinesterase
In the process of multiple motor unit recruitment, contractile strength is increased by
A. Increasing the voltage of the electrical stimulus
In the process of temporal summation, contractile strength is increased by
B. increasing the frequency of the electrical stimulus
Within a skeletal muscle fiber, which of the following processes does not use ATP hydrolysis (the process used to release ATP energy)
D. T-tubule depolarization
Which of the following is a primary source of fatigue within a skeletal muscle fiber?
B. Abundance of lactic acid in the sarcoplasm
The presence of myoglobin in skeletal muscle fibers
B. allows the cells to store a small amount of oxygen in the sarcoplasm
In single-unit smooth muscle tissue
C. each muscle fiber is connected to other fibers by gap-junctions
Beginning with Ca2+ entering the sarcoplasm, explain how the sliding filament theory explains the contraction in skeletal muscle. Be sure to use the names of specific molecules enzymes involved.
4 Ca2+ bind to Trop-C in troponin complex. This causes a conformational change in the complex, which causes tropomyosin to be pushed deeper between 2 F-actin molecules. This reveals myosin head binding sites on G-actin molecules. Myosin cross-bridges are activated by binding and hydrolysis of ATP. The heads of myosin molecules bind to the G-actin molecules by connecting cross-bridges. This binding causes a conformational change in the myosin molecule, a power stroke. The energy needed for this was stored in myosin by the binding and hydrolysis of the ATP molecule.
Beginning with Ca2+ entering the cytoplasm, explain how cross bridge cycling produces a contraction in smooth muscle and also how the muscle cell relaxes. Be sure to use the names of specific molecules of enzymes involved.
When Ca2+ enter the cytoplasm of smooth muscle cells, it binds to calmodulin. Calmodulin/Ca2+ complex binds to myosin light-chain kinase activating the enzyme. The activated enzyme then uses ATP to phosphorylate the myosin cross bridges allowing the bridges to bind to the actin molecules. Then another ATP is used to produce a power stroke. Relaxation is produced by the myosin light-chain phosphotase enzyme. This is always there and active, and it dephosphorylates the myosin.
Briefly state the three energy pathways, that skeletal muscle cells enlist to produce ATP while maintaining contractions during moderate exercise (less than 70% maximum energy metabolism). These occur in a specific order as muscle contractions are sustained. Be sure to list them in the proper order of their usage.
1. Creatine phosphate carries high-energy P bonds similar to those in ATP. These bonds can be cleaved and the energy used to attach a new P ion onto a ADP.
2. Glycogen is also found in muscle cells. This can be broken down to glucose which can be used in the process of aerobic cellular respiration. Glycolysis, the Citric Acid Cycle, and Chemiosmosis, the glycogen is converted into ATP energy.
3. The ultimate source of energy comes from the intake of carbs, lipids, and proteins. These foods are taken into the cell and converted to ATP.
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