Nokea
What is the electrical charge of the nucleus?
- A. A nucleus always has a positive charge.
- B. A stable nucleus has a positive charge, but a radioactive nucleus may have no charge and instead be neutral.
- C. A nucleus always has no charge and is instead neutral.
- D. A stable nucleus has no charge and is instead neutral, but a radioactive nucleus may have a charge.
Correct Answer: A
Rationale: A nucleus always has a positive charge. This is because the nucleus is composed of positively charged protons, along with neutral neutrons. The positive charge of the protons is balanced by the negative charge of the surrounding electrons in an atom, resulting in an overall neutral charge for the atom as a whole. Therefore, choice A is correct as it accurately reflects the positive charge of the nucleus due to the presence of protons. Choices B, C, and D are incorrect because they do not accurately represent the fundamental composition and charge distribution within an atom's nucleus. A stable nucleus consists of positively charged protons and neutral neutrons, leading to an overall positive charge, and not a neutral charge as suggested in the incorrect choices.
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What type of muscle is found in the walls of hollow organs like the intestines?
- A. Cardiac muscle
- B. Smooth muscle
- C. Skeletal muscle
- D. Voluntary muscle
Correct Answer: B
Rationale: Smooth muscle is the correct type of muscle found in the walls of hollow organs like the intestines. It is responsible for movements such as peristalsis, aiding in the movement of food and other materials through the digestive system. Cardiac muscle (Choice A) is found in the heart and is responsible for the heart's contractions, not in hollow organs like the intestines. Skeletal muscle (Choice C) is attached to bones and responsible for voluntary movements, not in hollow organ walls. Voluntary muscle (Choice D) is another term for skeletal muscle, which is under conscious control, unlike smooth muscle in hollow organ walls.
What is the small repeating unit in the contractile apparatus of skeletal muscle?
- A. Myofibril
- B. Actin
- C. Sarcomere
- D. Myosin
Correct Answer: C
Rationale: The correct answer is 'Sarcomere.' The sarcomere is the smallest repeating unit within myofibrils and is responsible for muscle contraction in skeletal muscle. It consists of overlapping actin and myosin filaments arranged in a highly organized structure that allows for the sliding of filaments during muscle contraction. 'Myofibril' (choice A) is incorrect because it is a larger structure composed of sarcomeres. 'Actin' (choice B) and 'Myosin' (choice D) are incorrect as they are individual proteins that are components of the sarcomere, not the smallest repeating unit itself.
Which type of tissue connects muscles to bones?
- A. Ligaments
- B. Tendons
- C. Cartilage
- D. Muscles
Correct Answer: B
Rationale: The correct answer is B: Tendons. Tendons connect muscles to bones, not bones to muscles. They play a crucial role in transmitting the force generated by muscles to move bones, enabling movement. Ligaments (choice A) connect bones to bones, providing stability to joints. Cartilage (choice C) is a connective tissue found in joints, providing cushioning and flexibility. Muscles (choice D) are responsible for generating force through contraction but do not directly connect muscles to bones.
Which structure of the respiratory system bifurcates into the primary bronchi?
- A. Trachea
- B. Alveoli
- C. Bronchioles
- D. Larynx
Correct Answer: A
Rationale: The trachea is the structure that bifurcates into the primary bronchi. The trachea is a tube that carries air to and from the lungs. It divides into the left and right primary bronchi at a specific point called the carina, which then further divide into secondary and tertiary bronchi, leading to the bronchioles. The alveoli are the tiny air sacs at the end of the bronchioles where gas exchange occurs, not the structure that bifurcates into the primary bronchi. Bronchioles are smaller airway branches that come after the bronchi but do not bifurcate into them. The larynx, also known as the voice box, is located above the trachea and is responsible for sound production, not the bifurcation into primary bronchi. Therefore, the correct answer is the trachea.
Which feedback loops are less common and sometimes harmful because they enhance stimuli rather than inhibit them?
- A. Negative feedback loop
- B. Positive feedback loop
- C. Inhibitory feedback loop
- D. Stimulating feedback loop
Correct Answer: B
Rationale: Correct. Positive feedback loops enhance or amplify changes, which can sometimes be harmful as they drive processes further from equilibrium. In contrast, negative feedback loops work to counteract deviations from a set point, promoting stability. Choice A, 'Negative feedback loop,' is incorrect because negative feedback loops inhibit or reduce changes, promoting stability. Choice C, 'Inhibitory feedback loop,' is incorrect as it is synonymous with negative feedback loops. Choice D, 'Stimulating feedback loop,' is incorrect as it inaccurately describes the nature of positive feedback loops.