Nursing practice questions with comprehensive rationales
NurseDive Free Nursing Practice Question
The cross-bridge cycling involves:
A. Myosin heads pulling actin toward the middle
Myosin heads pulling actin toward the center of the sarcomere is the core mechanism of cross-bridge cycling. This interaction shortens the sarcomere and generates muscle contraction. ATP binding and hydrolysis drive the cycle of attachment, power stroke, and detachment.
B. The shortening of thick filaments so that thin filaments slide past
Thick filaments do not shorten during contraction. Instead, thin filaments slide past the thick filaments as the sarcomere shortens. The filaments themselves remain the same length.
C. Actin and myosin lengthening in order to slide past each other
Actin and myosin do not lengthen during contraction. They maintain their structural integrity while sliding past each other through repeated cross-bridge interactions.
D. The Z discs sliding over the myofilaments
Z discs define the boundaries of a sarcomere and move closer together during contraction, but they do not slide over myofilaments. Their movement is a result of filament sliding, not a direct action.
E. The protein titin shortening the myosin filament
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Full Explanation
Choice A reason: Myosin heads pulling actin toward the center of the sarcomere is the core mechanism of cross-bridge cycling. This interaction shortens the sarcomere and generates muscle contraction. ATP binding and hydrolysis drive the cycle of attachment, power stroke, and detachment.
Choice B reason: Thick filaments do not shorten during contraction. Instead, thin filaments slide past the thick filaments as the sarcomere shortens. The filaments themselves remain the same length.
Choice C reason: Actin and myosin do not lengthen during contraction. They maintain their structural integrity while sliding past each other through repeated cross-bridge interactions.
Choice D reason: Z discs define the boundaries of a sarcomere and move closer together during contraction, but they do not slide over myofilaments. Their movement is a result of filament sliding, not a direct action.
Choice E reason: Titin is a structural protein that contributes to passive elasticity and sarcomere stability. It does not actively shorten or participate in the cross-bridge cycle
Similar Questions
A fracture in the shaft of a bone would be a break in the:
A. Metaphysis
The metaphysis is the region between the diaphysis and epiphysis, often containing the growth plate in children. It is not the shaft of the bone.
B. Epiphysis
The epiphysis refers to the ends of long bones, which articulate with adjacent bones. A fracture here would not be considered a shaft fracture.
C. Diaphysis
The diaphysis is the correct answer. It is the central shaft of a long bone, composed primarily of compact bone and housing the medullary cavity. Fractures in this region are common in long bones like the femur and humerus.
D. Periosteum
The periosteum is a fibrous membrane covering the outer surface of bones. While it may be affected in a fracture, it is not the structural region referred to as the shaft.
E. Endosteum
The endosteum lines the inner surface of the bone, including the medullary cavity. It plays a role in bone remodeling but is not the shaft itself
Full Explanation
Choice A reason: The metaphysis is the region between the diaphysis and epiphysis, often containing the growth plate in children. It is not the shaft of the bone.
Choice B reason: The epiphysis refers to the ends of long bones, which articulate with adjacent bones. A fracture here would not be considered a shaft fracture.
Choice C reason: The diaphysis is the correct answer. It is the central shaft of a long bone, composed primarily of compact bone and housing the medullary cavity. Fractures in this region are common in long bones like the femur and humerus.
Choice D reason: The periosteum is a fibrous membrane covering the outer surface of bones. While it may be affected in a fracture, it is not the structural region referred to as the shaft.
Choice E reason: The endosteum lines the inner surface of the bone, including the medullary cavity. It plays a role in bone remodeling but is not the shaft itself
Which of the following is NOT a function of the skeletal system?
A. Communication
Communication is not a direct function of the skeletal system. While the skeletal system supports structures involved in communication (e.g., the skull housing the brain), it does not itself facilitate communication.
B. Support
Support is a primary function of the skeletal system. It provides a rigid framework that supports the body and maintains its shape.
C. Storage of minerals
The skeletal system stores essential minerals such as calcium and phosphate, which can be released into the bloodstream as needed.
D. Production of blood cells
Hematopoiesis, or the production of blood cells, occurs in the red bone marrow found within certain bones. This is a vital function of the skeletal system.
E. Anchorage for muscles
Bones serve as anchoring points for muscles, allowing movement through the leverage of joints and tendons.
Full Explanation
Choice A reason: Communication is not a direct function of the skeletal system. While the skeletal system supports structures involved in communication (e.g., the skull housing the brain), it does not itself facilitate communication.
Choice B reason: Support is a primary function of the skeletal system. It provides a rigid framework that supports the body and maintains its shape.
Choice C reason: The skeletal system stores essential minerals such as calcium and phosphate, which can be released into the bloodstream as needed.
Choice D reason: Hematopoiesis, or the production of blood cells, occurs in the red bone marrow found within certain bones. This is a vital function of the skeletal system.
Choice E reason: Bones serve as anchoring points for muscles, allowing movement through the leverage of joints and tendons.
Yellow bone marrow contains a large percentage of:
A. Sharpey’s fibers
Sharpey’s fibers are collagen fibers that anchor the periosteum to the underlying bone. They are structural, not part of bone marrow.
B. Elastic tissue
Elastic tissue is found in ligaments and certain connective tissues but is not a major component of yellow bone marrow.
C. Spongy bone
Spongy bone surrounds the marrow cavities but is not the content of yellow marrow itself.
D. Fat
Fat is the correct answer. Yellow bone marrow primarily consists of adipocytes and serves as an energy reserve. It replaces red marrow in many bones as a person ages.
E. Blood-forming cells
Blood-forming cells are found in red bone marrow, not yellow marrow. Red marrow is responsible for hematopoiesis.
Full Explanation
Choice A reason: Sharpey’s fibers are collagen fibers that anchor the periosteum to the underlying bone. They are structural, not part of bone marrow.
Choice B reason: Elastic tissue is found in ligaments and certain connective tissues but is not a major component of yellow bone marrow.
Choice C reason: Spongy bone surrounds the marrow cavities but is not the content of yellow marrow itself.
Choice D reason: Fat is the correct answer. Yellow bone marrow primarily consists of adipocytes and serves as an energy reserve. It replaces red marrow in many bones as a person ages.
Choice E reason: Blood-forming cells are found in red bone marrow, not yellow marrow. Red marrow is responsible for hematopoiesis.