Which row shows the correct order of reactivity for the elements?

Correct Answer: D

Rationale: The correct order of reactivity for elements is based on their tendency to lose electrons. In this case, sodium is the most reactive as it readily loses an electron to form a stable ion. Zinc is less reactive compared to sodium but more reactive than hydrogen and gold. Hydrogen is less reactive than both zinc and sodium. Gold is the least reactive among the options given. Therefore, the correct order of reactivity is sodium > zinc > hydrogen > gold, which matches option D. Choices A, B, and C do not follow the correct order of reactivity for the elements listed, making them incorrect.

Correct Answer: C

Rationale: The correct answer is C: ADH. The pituitary gland consists of two parts: the anterior and posterior pituitary. ADH, also known as vasopressin, is synthesized in the hypothalamus and stored in the posterior pituitary. Therefore, it is not synthesized in the pituitary gland itself. LH, FSH, and TSH are all hormones synthesized and released by the anterior pituitary gland.

Correct Answer: A

Rationale: Insulin enhances glucose transport by promoting the translocation of glucose transporter proteins to the cell membrane. The brain does not require insulin for glucose uptake as it has a specialized transporter. Skeletal muscle, myocardium, and adipose tissue all rely on insulin for increased glucose transport. Therefore, the correct answer is A. The other choices (B, C, and D) are incorrect as they all depend on insulin to enhance glucose transport in their respective tissues.

Correct Answer: C

Rationale: The correct answer is C: Its isthmus is at the level of thyroid cartilage. The isthmus of the thyroid gland is located at the level of the cricoid cartilage, not the thyroid cartilage. The thyroid gland is closely related to the inferior (recurrent) laryngeal nerve (A), it moves on swallowing (B), and it is invested by pretracheal fascia together with the parathyroids (D). These choices are correct anatomical characteristics of the thyroid gland.

Correct Answer: c

Rationale: The correct answer is C because when an action potential reaches the axon terminal, endosomes containing neurotransmitters fuse with the cell membrane and release neurotransmitter into the synaptic cleft. This process is known as exocytosis. This neurotransmitter then binds to receptors on the postsynaptic neuron, initiating a new action potential. Choice A is incorrect because the muscle fiber contraction is initiated by the binding of the neurotransmitter to receptors on the muscle cell, not directly by the action potential reaching the axon terminal. Choice B is incorrect because acetylcholinesterase breaks down acetylcholine in the synaptic cleft after it has already been released and has completed its role in transmitting the signal. Choice D is incorrect because sodium channels opening at the motor end plate is part of the process of muscle cell depolarization and contraction, not directly related to the release of neurotransmitter at the axon terminal.