Muscle Flashcards
Which of the following correctly describes the function of the muscular system?
Posture and thermoregulation
Movement and regulation of respiration
Movement and acquired immunity
Posture and secondary sex characteristics
Posture and thermoregulation
The muscular system performs the following functions:
Movement
Posture
Thermoregulation
Which type of muscles have striated muscle fibers that join at the intercalated disc?
Vascular muscles
Skeletal muscle
Cardiac muscle
Smooth muscle
The correct answer is Cardiac muscle.
Cardiac muscles have branched, striated fibers that have a single nucleus. The fibers join at the intercalated discs.
Which of the following correctly describes the skeletal muscles?
Branched, striated fibers with a single nucleus
Striated, multinucleated cylindrical fibers
Spindle-shaped, nonstriated fibers with a single nucleus
Spindle-shaped, multinucleated, nonstriated fibers
The correct answer is Striated multinucleated cylindrical fibers.
Skeletal muscle has striated multinucleated cylindrical fibers, and its action is under voluntary control.
Which of the following contains nonstriated muscle fibers?
Pectoralis major
The heart
The intestine
Quadricep muscle
The intestine.
Smooth muscles are spindle-shaped, nonstriated, and have a single nucleus.
They are involuntary muscles. Smooth muscles are present in the gastrointestinal tract, walls of blood vessels, uterus, bladder, ureter, and urethra.
Muscles attach to the bones through a _______________.
Cartilage
Joint
Tendon
Ligament
The correct answer is Tendon.
A tendon attaches a muscle to a bone.
The rod-like structure that makes up muscle fibers is called _____________.
Tropomyosin
Intercalated disc
Actin
Myofibrils
The correct answer is Myofibrils.
Myofibrils are rod-like structures that make up the muscle fibers. Each muscle cell/fiber is made up of numerous myofibrils.
The functional unit of the myofibril is called ____________.
Actin
Myosin
Sarcomere
Z-line
The correct answer is Sarcomere.
The sarcomere is the functional unit of a myofibril.
Myofibrils consist of:
Thin filament that comprises actin filament, tropomyosin which spirals around the actin filament, and troponin which attaches tropomyosin to actin.
Thick filament that comprises myosin.
Which group of muscles increases the angle at a joint?
Pronators
Flexors
Extensors
Abductors
The correct answer is Extensors.
Extensors increase the angle at a joint.
Flexors decrease the angle at a joint.
Abductors pull the limb away from the midline.
Pronators rotate the forearm so that the palm faces posteriorly.
The pectoralis major pulls the arm towards the midline. This movement is called _________.
Supination
Adduction
Abduction
Flexion
The correct answer is Adduction.
Adduction pulls towards the midline.
Which of the following describes flexion?
Decreases the angle at a joint
Pulls towards the midline
Pulls away from the midline
Increases the angle at a joint
The correct answer is Decreases the angle at a joint.
Flexion decreases the angle at a joint.
Which of the following terms and descriptions is correctly paired?
Flexion—increases the angle at a joint
Extension—away from the midline
Abduction—reduces the angle at a joint
Adduction—towards the midline
The correct answer is Adduction—towards the midline.
Adduction moves towards the midline.
Which of the following is not a part of the thin myofilament?
Actin
Tropomyosin
Troponin
Myosin
The correct answer is Myosin.
The thick filament is composed of myosin.
The thin myofilament comprises:
Actin
Tropomyosin, which spirals around actin filament and covers the myosin-binding sites.
Troponin holds the tropomyosin to the actin filament.
Troponin has different subunits. Troponin I has an affinity for actin, troponin T has an affinity for tropomyosin, and troponin C has an affinity for calcium.
When troponin binds calcium, it causes the tropomyosin to shift and uncover the myosin-binding sites.
Which of the following cleaves ATP to generate energy for muscle contraction?
Tropomyosin
Myosin
Actin
Troponin
The correct answer is Myosin.
Myosin cleaves ATP, which it utilizes to generate energy used to tug on actin, leading to contraction and shortening of the sarcomere.
The process of muscle contraction is described below:
An action potential arrives at the neuromuscular junction
The sarcoplasmic reticulum releases calcium molecules
Calcium binds to troponin, which leads to the active site of actin being exposed
The myosin head full of energy from cleaved ATP binds to actin and forms cross bridges
The myosin tugs on actin and moves it towards the midline leading to contraction and shortening of the sarcomere
ADP is released and new ATP binds to myosin
The myosin head detaches, cleaves the ATP, and is ready to begin the cycle again
What is the role of calcium in muscle contraction?
Calcium binds to actin to initiate the formation of cross-bridges between myosin and actin
Calcium binds to myosin to initiate the formation of cross-bridges between myosin and actin
Calcium binds to troponin and leads to the uncovering of the active site of actin
Calcium binds to tropomyosin and leads to the uncovering of the active site of actin
The correct answer is Calcium binds to troponin and leads to the uncovering of the active site of actin.
Calcium binds to troponin and this causes tropomyosin to uncover the binding sites on the actin filament to which myosin can bind.
During muscle contraction, calcium molecules are released from ____________.
Sarcoplasmic reticulum
Troponin
Tropomyosin
Myosin
The correct answer is Sarcoplasmic reticulum.
When an action potential arrives at the neuromuscular junction, the muscle gets depolarized. This leads to the release of calcium from the sarcoplasmic reticulum.
