PTA Science Fundamentals 3 — Questions and Answers
Question 1: Which of the following describes an isotonic muscle contraction?
- Muscle length stays the same while tension changes
- Muscle tension stays the same while length changes (Correct answer)
- No movement occurs at either the joint or muscle
- Muscle contracts and relaxes simultaneously
Correct answer: Muscle tension stays the same while length changes
Isotonic contractions occur when muscle tension remains constant while the muscle changes length, as seen in lifting a fixed weight.
Question 2: Which body system is primarily responsible for regulating blood pH?
- Skeletal system
- Integumentary system
- Renal and respiratory systems (Correct answer)
- Lymphatic system
Correct answer: Renal and respiratory systems
The kidneys regulate bicarbonate excretion and the lungs control CO₂ levels, together maintaining blood pH near 7.4.
Question 3: In a lever system, the mechanical advantage increases when:
- The effort arm is shorter than the resistance arm
- The fulcrum is placed between the effort and resistance
- The effort arm is longer than the resistance arm (Correct answer)
- Force and resistance are equidistant from the fulcrum
Correct answer: The effort arm is longer than the resistance arm
Mechanical advantage = effort arm length ÷ resistance arm length; a longer effort arm relative to the resistance arm produces greater mechanical advantage.
Question 4: Covalent bonds are formed by:
- Transfer of electrons between atoms
- Sharing of electron pairs between atoms (Correct answer)
- Attraction between oppositely charged ions
- Van der Waals forces only
Correct answer: Sharing of electron pairs between atoms
Covalent bonds form when two atoms share one or more pairs of electrons, as in water (H₂O) or glucose.
Question 5: Which organelle synthesizes proteins based on mRNA instructions?
- Golgi apparatus
- Lysosome
- Ribosome (Correct answer)
- Smooth endoplasmic reticulum
Correct answer: Ribosome
Ribosomes translate mRNA sequences into polypeptide chains, which then fold into functional proteins.
Question 6: The term 'homeostasis' refers to the body's ability to:
- Regenerate damaged tissue at accelerated rates
- Maintain a stable internal environment despite external changes (Correct answer)
- Increase metabolic rate during exercise
- Adapt muscles to prolonged resistance training
Correct answer: Maintain a stable internal environment despite external changes
Homeostasis is the process by which physiological systems use feedback mechanisms to maintain stable internal conditions (e.g., temperature, pH, glucose).
Question 7: What is the primary role of surfactant in the lungs?
- Transport oxygen across the alveolar membrane
- Reduce surface tension in alveoli to prevent collapse (Correct answer)
- Stimulate bronchodilation during exercise
- Filter inhaled pathogens before reaching alveoli
Correct answer: Reduce surface tension in alveoli to prevent collapse
Pulmonary surfactant is a phospholipid mixture secreted by type II pneumocytes that reduces alveolar surface tension, preventing alveolar collapse (atelectasis).
PTA Science Fundamentals 3
Which of the following describes an isotonic muscle contraction?