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.
Which statement regarding the movement in the sensitive plant (Mimosa pudica) is INCORRECT?
It is a seismonastic movement triggered by touch or other stimuli.
It involves the active transport of potassium ions into the pulvinus.
It is a nastic movement caused by changes in turgor pressure.
Water moves out of the pulvinus cells, leading to a decrease in turgor and leaf drooping.
A patient presents with muscle weakness and fatigue. Biochemical analysis reveals a defect in the calcium-binding protein crucial for muscle contraction, specifically within the thin filaments. Which protein is MOST likely affected?
Tropomyosin
Troponin T
Troponin I
Troponin C
During strenuous exercise, muscle fatigue can occur due to the accumulation of which metabolic byproduct, inhibiting the binding of calcium to troponin C?
Lactate
Pyruvate
ATP
H+
A researcher is studying muscle contraction in vitro. They observe that even with sufficient ATP and $Ca^{2+}$$, contraction doesn't occur when they introduce a compound that specifically inhibits the binding of myosin heads to actin filaments. Which step of the cross-bridge cycle is directly affected by this compound?
Release of Pi from the myosin head
Attachment of myosin heads to actin
Hydrolysis of ATP
Power stroke
A genetic mutation affects the $Ca^{2+}$$-ATPase pumps in the sarcoplasmic reticulum (SR). Which of the following would be the MOST likely direct consequence of this mutation in muscle fibers?
Inhibition of action potential propagation along the sarcolemma
Reduced release of acetylcholine at the neuromuscular junction
Prolonged muscle contraction due to impaired $Ca^{2+}$$ removal from the sarcoplasm
Inability of troponin to bind $Ca^{2+}$$
In a research experiment, a muscle fiber is exposed to a drug that inhibits the activity of acetylcholinesterase. Which of the following is the MOST likely direct effect on muscle contraction?
Inhibition of action potential generation in the muscle fiber
Prevention of calcium release from the sarcoplasmic reticulum
Prolonged muscle contraction due to continuous stimulation at the neuromuscular junction
Increased rate of ATP hydrolysis
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
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
