Prepare for NEET Biology Locomotion And Movement with MCQs & PYQs on NEET.GUIDE. Access free practice, previous year questions, and expert explanations of muscles and skeleton.
The 'rigor mortis' state after death is primarily caused by:
Massive calcium influx into muscle cells
Permanent contraction of all muscle fibers
Depletion of ATP, preventing myosin detachment from actin
Denaturation of muscle proteins due to temperature changes
Which statement BEST describes the role of tropomyosin in skeletal muscle?
It binds calcium ions to initiate muscle contraction.
It hydrolyzes ATP to provide energy for muscle contraction.
It forms the cross-bridges between actin and myosin.
It blocks myosin-binding sites on actin in the resting state.
The nebulin protein is associated with thin filaments and plays a crucial role in:
Binding calcium ions to initiate contraction
Hydrolyzing ATP to provide energy for contraction
Regulating the length of actin filaments
Forming cross-bridges between actin and myosin
A mutation affecting the flexibility of the hinge region of the myosin molecule would MOST directly impair which step of the cross-bridge cycle?
ATP binding
ATP hydrolysis
The power stroke
Myosin detachment from actin
A patient presents with brittle bones, decreased bone density, and a history of fractures. Genetic analysis reveals a mutation affecting the function of osteoblasts. Which of the following is the MOST likely consequence of this mutation?
Increased bone resorption by osteoclasts
Reduced bone matrix synthesis and mineralization
Excessive cartilage formation at the epiphyseal plates
Enhanced calcium absorption in the intestines
Which of the following accurately describes the role of the periosteum in fracture repair?
Secretes synovial fluid to lubricate the fracture site
Provides cells that differentiate into osteoblasts and chondroblasts, contributing to callus formation
Absorbs excess calcium from the blood to promote bone hardening
Stimulates osteoclast activity to remove damaged bone fragments
A rare genetic disorder leads to defective collagen synthesis specifically within the intervertebral discs. Which of the following is the MOST likely direct consequence of this disorder?
Increased bone density in the vertebrae
Reduced ability of the discs to withstand compressive forces
Inflammation of the synovial joints
Accelerated bone growth in the limbs
Which structural feature distinguishes the atlas vertebra from other cervical vertebrae, enabling its unique articulation with the skull?
Presence of a prominent spinous process
Absence of a vertebral body and presence of lateral masses
Fusion with the axis vertebra to form a single unit
Presence of a bifid spinous process
A child presents with bowed legs, muscle weakness, and delayed growth. Biochemical analysis reveals low levels of vitamin D and calcium. Radiographic examination of the bones is MOST likely to reveal which of the following?
Increased bone density and thickening of the cortical bone
Decreased bone mineralization and widening of the epiphyseal plates
Premature closure of the epiphyseal plates
Excessive bone resorption by osteoclasts
During endochondral ossification, the primary ossification center forms in the diaphysis of the long bone. Which specific event initiates the formation of this ossification center?
Deposition of calcium salts in the cartilage matrix
Invasion of blood vessels into the cartilage model, bringing osteoprogenitor cells
Proliferation of chondrocytes at the epiphyseal plate
Formation of the periosteal bone collar
