Insulin enhances the membrane transport of glucose in all of the following tissues EXCEPT __________.

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 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.

Correct Answer: C

Rationale: The correct answer is C: anterior pituitary gland. Portal capillaries carry releasing hormones from the hypothalamus to the anterior pituitary gland, where they regulate the release of hormones. Releasing hormones do not target the neurohypophysis (choice A) or the posterior pituitary gland (choice D) directly. They also do not affect the pancreas (choice B) in this context. Thus, the correct answer is the anterior pituitary gland due to its role in receiving and responding to releasing hormones from the hypothalamus.

Correct Answer: C

Rationale: Rationale: 1. Lactogenic hormone stimulates mammary glands to produce milk, essential for lactation. 2. Oxytocin is a different hormone that causes milk ejection, not production. 3. Gonadotropins like FSH and LH affect gonads, not lactation. 4. Choice C directly relates to lactation, making it the correct answer.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Insulin is a hormone that regulates blood glucose levels by promoting glucose uptake into cells. 2. Beta cells of the islets of Langerhans in the pancreas are responsible for secreting insulin. 3. Insulin lowers blood glucose levels by enhancing glucose uptake and storage. 4. Therefore, choice A is correct as it accurately identifies the source of insulin secretion. Summary: - Choice B is incorrect as the liver does not secrete insulin. - Choice C is incorrect as insulin lowers blood glucose levels. - Choice D is incorrect as insulin is released in response to high, not low, blood glucose levels.