Free Support and Movement MCQs with Answers

61. Why thick filaments are unable to bind with thin filament in a relaxed muscle fiber?

• A. Actin blocks the myosin binding site
• B. Tropomyosin blocks the myosin binding site
• C. Troponin blocks the myosin binding site
• D. Tropomyosin blocks the troponin binding site

Explanation: In a relaxed fibre the long tropomyosin strand lies across the myosin binding sites on actin, so no cross bridge can form. Troponin is the tempting answer, but its job is to hold tropomyosin in that position and then pull it aside once calcium binds to it. Actin carries the binding sites rather than blocking them.

62. Once an action potential reaches the membrane of a skeletal muscle fiber, what is the first event that occurs in the contraction process?

• A. Actin and myosin form a cross-bridge
• B. Calcium is pumped back into the sarcoplasmic reticulum
• C. Calcium is released from the sarcoplasmic reticulum
• D. ATP is hydrolyzed by troponin

Explanation: The action potential travels down the T tubules and triggers the sarcoplasmic reticulum to release calcium, which then binds troponin and moves tropomyosin off the binding sites so cross bridges can form. Cross bridge formation therefore comes second, not first, which is the trap in the first option. Pumping calcium back is what ends the contraction.

63. The pubic symphysis is a slightly moveable joint joined by which of the following tissue?

• A. Elastic cartilage
• B. Fibrocartilage
• C. Costal cartilage
• D. Articular cartilage

Explanation: Fibrocartilage is tough and compressible, which suits a slightly movable joint that must bear load, and it is the same tissue found in the intervertebral discs and the menisci of the knee. Articular cartilage is the smooth hyaline layer covering bone ends in freely movable joints. Elastic cartilage supports the pinna of the ear and costal cartilage joins the ribs to the sternum.

64. Arthritis is:

• A. Inflammation of joints
• B. Herniation of intervertebral disc
• C. Fusion of vertebral joint
• D. Tingling along the length of legs

Explanation: The word itself means inflammation of a joint, from arthron for joint and itis for inflammation, and it covers osteoarthritis, rheumatoid arthritis and gout despite their very different causes. A herniated disc is a slipped disc pressing on a nerve, which produces the tingling described in the last option. Reading the suffix is often enough with medical terms of this kind.

65. Which type of joint is present in pubis?

• A. Fibrous joints
• B. Immoveable joints
• C. Cartilaginous joints
• D. Freely moveable joints

Explanation: The pubic symphysis is a cartilaginous joint, its two bones joined by a pad of fibrocartilage that allows slight movement, which becomes important during childbirth when the ligaments soften. Fibrous joints such as the skull sutures allow no movement at all, and freely movable synovial joints have a fluid filled cavity. Cartilaginous joints sit between these two extremes.

66. In which of the following combination, both components have hyaline cartilage?

• A. Epiglottis & intervertebral disc
• B. Trachea & intervertebral disc
• C. Nose & pinna
• D. Nose & trachea

Explanation: The C shaped rings of the trachea and the supporting plates of the nose are both hyaline cartilage, the smooth glassy type that also covers the ends of bones. The intervertebral discs are fibrocartilage, built for shock absorption, and the epiglottis and pinna are elastic cartilage, which springs back into shape. Each pairing in the wrong options mixes two different types.

67. Which of the following characters is shared by both skeletal and cardiac muscles?

• A. Presence of striation
• B. Involuntary control
• C. Multinucleated fibers
• D. Intercalated discs

Explanation: Both use the same regular arrangement of actin and myosin filaments, so both show cross striations under the microscope. They differ in control, skeletal being voluntary and cardiac involuntary, and intercalated discs and branching belong to cardiac muscle alone. Multinucleated fibres are a skeletal muscle feature.

68. Which of the following muscle types are involuntary in action?

• A. Skeletal and smooth
• B. Skeletal and cardiac
• C. Cardiac and smooth
• D. Smooth muscle only

Explanation: Cardiac muscle beats rhythmically without conscious control and smooth muscle works the gut, blood vessels and other hollow organs automatically, so both are involuntary. Skeletal muscle is the only voluntary type, which eliminates the first two options at once. Smooth muscle alone is too narrow, since it leaves cardiac muscle out.

69. In which of the following combinations, both components have non-striated muscle fibers?

• A. Intestine & biceps
• B. Intestine & blood vessels
• C. Heart & lungs
• D. Stomach & heart

Explanation: The walls of the intestine and of blood vessels both contain smooth muscle, which has no striations and works involuntarily. The biceps is skeletal muscle and the heart is cardiac, and both of those are striated, so any pairing including them fails. Recognising which organ contains which muscle type is the whole of this question.