Target organs regulate the pituitary through feedback loops.
Most often, this is in the form of a.
positive feedback.
direct nervous stimulation.
negative feedback inhibition.
reverberation.
The Correct Answer is C
Choice C rationale
Negative feedback inhibition is the most common mechanism by which target organs regulate pituitary hormone secretion. When the concentration of a hormone secreted by a target gland reaches a sufficient level, it inhibits the release of stimulating hormones from the pituitary and/or hypothalamus, thereby maintaining hormonal homeostasis and preventing overproduction.
Choice A rationale
Positive feedback is less common in endocrine regulation and typically leads to an amplification of the initial stimulus, rather than a return to homeostasis. An example is the surge of luteinizing hormone during ovulation, where estrogen stimulates more LH release.
Choice B rationale
Direct nervous stimulation occurs in some cases, such as the adrenal medulla's release of catecholamines in response to sympathetic preganglionic neurons. However, for target organ regulation of the pituitary, feedback loops involving hormones are the predominant mechanism, not direct nervous stimulation.
Choice D rationale
Reverberation refers to a type of neural circuit where neurons re-excite themselves or upstream neurons, leading to a sustained output. This concept is primarily relevant to neural networks and not a direct mechanism for endocrine feedback from target organs to the pituitary gland.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
While the immune response originates in specific organs like the thymus, bone marrow, and lymph nodes, this statement describes the origin of immune cells and processes, not the fundamental characteristic of specificity, which relates to targeting particular antigens.
Choice B rationale
Similar to Choice A, the immune response involves specialized tissues throughout the body, such as lymphoid tissues. However, this describes the anatomical distribution of the immune system rather than the core principle of specificity in recognizing unique pathogens.
Choice C rationale
The immune response is indeed carried out by specific groups of cells, such as B lymphocytes and T lymphocytes, which have specialized functions. However, while these cells contribute to specificity, the most direct definition of specificity in immunity is the targeted response against a particular pathogen or antigen.
Choice D rationale
Specificity in immunity means that the immune system's response is highly targeted and precise. Each specific B and T lymphocyte is programmed to recognize and respond to a particular epitope (a specific molecular structure) on a pathogen, ensuring that the immune response is directed only against the invading microbe.
Choice E rationale
The immune response involves specialized tissues. However, this statement focuses on the location rather than the fundamental characteristic of specificity, which refers to the precise recognition and targeting of a particular pathogen or antigen by immune cells.
Correct Answer is A
Explanation
Choice A rationale
Oxygen-poor blood from the systemic circulation enters the right atrium, then passes through the right AV (tricuspid) valve into the right ventricle. From the right ventricle, it is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. This pathway ensures deoxygenated blood reaches the pulmonary circuit.
Choice B rationale
This choice is incomplete because while oxygen-poor blood does pass through the right AV (tricuspid) valve, it must also pass through the pulmonary valve to exit the right ventricle and reach the lungs for oxygenation. Omitting the pulmonary valve provides an incomplete description of the path.
Choice C rationale
The left AV (mitral) valve and aortic valve are components of the left side of the heart, which handles oxygenated blood. Oxygenated blood from the lungs enters the left atrium, passes through the mitral valve into the left ventricle, and then through the aortic valve into the aorta for systemic distribution.
Choice D rationale
This choice describes only the entry of oxygenated blood into the left ventricle from the left atrium via the left AV (mitral) valve. It does not account for the oxygen-poor blood pathway, which involves the right side of the heart.
Choice E rationale
The pulmonary valve allows oxygen-poor blood to leave the right ventricle. However, the aortic valve allows oxygenated blood to leave the left ventricle. Therefore, the combination of pulmonary and aortic valves does not exclusively describe the path of oxygen-poor blood.
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