Questions & explanations
1. Which of the following is an example of a saddle joint?
- Knee joint
- Shoulder joint
- Joint between carpal and metacarpal of thumb
- Hip joint
Answer: Joint between carpal and metacarpal of thumb
A saddle joint is a type of synovial joint where the articulating surfaces are saddle-shaped, allowing movement in two planes. The joint between the carpal and metacarpal of the thumb is a classic example. The knee joint is a hinge joint, the shoulder joint is a ball-and-socket joint, and the hip joint is also a ball-and-socket joint.
2. Which property of muscles is primarily responsible for locomotion and other movements in humans and most multicellular organisms?
- Excitability
- Contractility
- Extensibility
- Elasticity
Answer: Contractility
Contractility is the ability of muscle fibers to shorten and generate force, which is essential for movement. Excitability refers to the ability to respond to stimuli, extensibility to stretching, and elasticity to returning to original shape, but contractility directly produces movement.
3. Gout is a type of arthritis caused by the deposition of crystals of which substance in the joints?
- A. Calcium oxalate
- B. Uric acid
- C. Cholesterol
- D. Calcium pyrophosphate
Answer: B. Uric acid
Gout is characterized by the accumulation of uric acid crystals in the joints, leading to inflammation and pain. Calcium oxalate is associated with kidney stones, cholesterol with atherosclerosis, and calcium pyrophosphate with pseudogout.
4. Which of the following is NOT a function of the vertebral column?
- Protection of the spinal cord
- Support of the head
- Attachment for ribs and back muscles
- Production of red blood cells
Answer: Production of red blood cells
The vertebral column protects the spinal cord, supports the head, and provides attachment for ribs and back muscles. Red blood cell production occurs in bone marrow, but this is not a primary function of the vertebral column as a whole.
5. Which of the following disorders is primarily genetic and affects the muscular and skeletal systems, leading to impaired locomotion?
- Myasthenia gravis
- Muscular dystrophy
- Tetany
- Arthritis
Answer: Muscular dystrophy
Muscular dystrophy is a genetic disorder characterized by progressive degeneration of skeletal muscles, directly affecting locomotion. Myasthenia gravis is autoimmune, tetany is due to low calcium, and arthritis is inflammatory.
6. Which of the following structures is found in the sarcoplasm of a muscle fiber and consists of parallelly arranged filaments?
- A. Sarcoplasmic reticulum
- B. Myofibrils
- C. T-tubules
- D. Sarcolemma
Answer: B. Myofibrils
The sarcoplasm contains myofibrils, which are long, parallel filaments composed of myofilaments (actin and myosin). The sarcoplasmic reticulum stores calcium, T-tubules conduct impulses, and the sarcolemma is the cell membrane.
7. Which of the following is an example of a fibrous joint?
- Sutures of the skull
- Intervertebral discs
- Knee joint
- Shoulder joint
Answer: Sutures of the skull
The flat skull bones fuse end-to-end with dense fibrous connective tissue forming sutures, which are classic examples of fibrous joints. Intervertebral discs are cartilaginous joints; knee and shoulder joints are synovial.
8. According to the sliding filament theory, muscle contraction occurs due to:
- A. Shortening of thick filaments
- B. Sliding of thin filaments over thick filaments
- C. Shortening of thin filaments
- D. Overlap of thick and thin filaments without sliding
Answer: B. Sliding of thin filaments over thick filaments
The sliding filament theory explains that during contraction, the thin filaments (actin) slide over the thick filaments (myosin), pulling the Z-lines closer and shortening the sarcomere without changing filament lengths.
9. Which band of a myofibril contains myosin and is anisotropic?
- A. I-band
- B. A-band
- C. Z-line
- D. M-line
Answer: B. A-band
The A-band (anisotropic) contains myosin, while the I-band (isotropic) contains actin. Z-line and M-line are lines/zones (not bands) marking the center of the I-band and A-band respectively, not 'structural proteins'.
10. What factor affects the movability at joints?
- The type of joint and its structure
- The color of the bones
- The length of the muscles
- The amount of blood flow
Answer: The type of joint and its structure
Movability at joints varies depending on factors such as the type of joint (fibrous, cartilaginous, synovial) and its structural characteristics. Color, muscle length, and blood flow are not primary determinants.
11. Which part of the myosin molecule contains the ATP binding site and the actin binding site, and projects outward from the thick filament at regular intervals?
- A. Tail
- B. Head
- C. Neck
- D. Rod
Answer: B. Head
The myosin head has the active site for ATP hydrolysis and binds to actin during contraction. It is the globular part that extends from the thick filament forming cross-bridges at regular distances and angles.
12. Locomotion in humans requires the coordinated activity of which systems?
- Muscular and skeletal systems only
- Muscular, skeletal, and neural systems
- Skeletal and neural systems only
- Muscular and neural systems only
Answer: Muscular, skeletal, and neural systems
Locomotion involves muscles contracting to move bones, with the nervous system coordinating and controlling these actions. All three systems work together; missing any one would prevent effective movement.