Muscle Contraction
Some are involved in muscle contraction, such as calcium.
What our notes say
- Some are involved in muscle contraction, such as calcium. (Medical Physiology Assorted SAQs — With Answers (Past Paper Study Guide))
- Pendular movements: longitudinal muscle contraction that moves the segment back and forth to mix the contents. (General Surgery CAT 2 (MBSG 4600): 4 October 2021)
- Extrafusal muscle contraction can be achieved by: *(repeat, see Paper 4 Q6 — Answer: a)* (cat 2 2014 — Source Paper Awaiting Edit)
- Kinins (Bradykinin) — smooth muscle contraction, vasodilatation, increased vascular permeability (Medical MCQs: Chemical Pathology & Haematology Exam Review)
- Loss of inhibitory signals → unopposed, sustained muscle contraction → spastic/rigid paralysis (opposite mechanism to botulism, which causes flaccid paralysis) (Streptococcus Classification, S. pyogenes, Rheumatic Fever, AGN)
- Bradykinin — pain, vasodilation, smooth muscle contraction (⚠️ NOT involved in opsonization — common false-option trap) (General Pathology Revision: Cell Injury, Inflammation & Adaptation (MBPA 3500 Pa)
Study material on Muscle Contraction
- Genetic and Autoimmune Causes with Focus on Affected Proteins
- cat 2 2014 — Source Paper Awaiting Edit
- Medical Physiology Year Two – Paper Two MCQs
- Medical Physiology Mid-Semester Exam — 2020 (Past Paper)
- Weekly Year 1: Enzymes, Vitamins and Minerals Exam - June 19, 2026 (Section A: MCQs)
- Weekly Year 2: Cellular Immunology Exam - May 1, 2026 (Section A: MCQs)
Practice questions on Muscle Contraction
The primary disadvantage of anaerobic glycolysis during high-intensity muscle contractions is:
- A. Its dependence on oxygen availability.
- B. The relatively low ATP yield per glucose molecule.
- C. The rapid accumulation of lactate, leading to muscle fatigue.
- D. Its slow rate of ATP production compared to aerobic pathways.
Answer: C. Anaerobic glycolysis produces ATP rapidly but inefficiently, yielding only 2 ATP per glucose. A major disadvantage in high-intensity contractions is the production of lactic acid (lactate) as pyruvate is converted to regenerate NAD+, which lowers muscle pH and contributes to fatigue.
Which major mineral is crucial for bone and tooth structure, muscle contraction, nerve transmission, and blood clotting?
- A. Sodium
- B. Potassium
- C. Calcium
- D. Magnesium
Answer: C. Calcium is the most abundant mineral in the body, primarily forming bones and teeth. It also plays vital roles as an intracellular messenger, in muscle contraction, nerve impulse transmission, and blood coagulation.
High-energy phosphate bonds for instant human muscle contraction are readily provided by which molecule?
- Phosphocreatine
- Adenosine Triphosphate (ATP)
- Glucose
- Lactic acid
Answer: A. Phosphocreatine acts as a rapid reservoir of high-energy phosphate bonds that can quickly regenerate ATP from ADP during intense muscular activity.
Tetanospasmin, the toxin produced by Clostridium tetani, blocks the release of inhibitory neurotransmitters (GABA and glycine) at the spinal cord level, leading to uncontrolled muscle contraction.
- A) It blocks inhibitory neurotransmitters
- B) It inhibits muscle contraction
- C) It causes rapid muscle fatigue
- D) It directly damages muscle fibers
Answer: A. Tetanospasmin acts centrally by inhibiting the release of inhibitory neurotransmitters, leading to spastic paralysis. This means it disinhibits excitatory pathways, resulting in uncontrolled muscle excitation and contraction, not inhibition of contraction.
During skeletal muscle contraction, what role does Ca2+ primarily play?
- Binds to myosin heads to initiate cross-bridge cycling.
- Causes the release of acetylcholine from the motor neuron.
- Binds to troponin, exposing myosin binding sites on actin.
- Powers the reuptake of calcium into the sarcoplasmic reticulum.
Answer: C. In skeletal muscle contraction, Ca2+ is released from the sarcoplasmic reticulum and binds to troponin C. This binding causes a conformational change in the troponin-tropomyosin complex, which moves tropomyosin away from the myosin-binding sites on the actin filaments, allowing myosin heads to attach and initiate cross-bridge cycling. Ca2+ does not bind directly to myosin (A) to initiate cross-bridge cycling. Ca2+ ca
High-energy phosphate bonds for instant human muscle contraction are readily provided by:
- Creatine phosphate
- ATP hydrolysis alone
- Lactic acid
- Glycogen
Answer: A. Creatine phosphate serves as a readily available phosphate donor to quickly regenerate ATP from ADP during the initial phase of intense muscle activity.