A client's body temperature rises above normal.
Which physiological response is activated to promote heat loss?
Peripheral vasodilation.
Increased metabolic activity.
Shivering.
Peripheral vasoconstriction.
The Correct Answer is A
Choice A rationale
Peripheral vasodilation occurs when the smooth muscles in the walls of arterioles relax, allowing more blood to flow to the skins surface. This mechanism facilitates the transfer of internal body heat to the external environment through radiation and convection. By increasing cutaneous blood flow, the body effectively sheds excess thermal energy to maintain a stable internal core temperature of approximately 37 degrees Celsius, which is essential for preserving cellular enzymatic functions and metabolic homeostasis.
Choice B rationale
Increased metabolic activity is a thermogenic process that generates heat rather than promoting its loss. When the basal metabolic rate rises, the body consumes more oxygen and nutrients to produce adenosine triphosphate, resulting in heat as a byproduct. This physiological response is typically activated during cold exposure or fever to raise body temperature. Therefore, it is counterproductive when the body is already above normal temperature and needs to cool down to prevent hyperthermia.
Choice C rationale
Shivering is an involuntary physical response characterized by rapid, rhythmic muscle contractions that generate significant amounts of heat through friction and metabolic consumption. It is a primary mechanism for thermogenesis used by the body to counteract hypothermia. If the body temperature is already elevated, shivering would further increase the thermal load, potentially leading to heat exhaustion or heat stroke. This response is inhibited by the hypothalamus when the body needs to facilitate heat dissipation.
Choice D rationale
Peripheral vasoconstriction involves the narrowing of blood vessels near the skin surface to redirect blood toward the internal organs. This process minimizes heat loss to the environment and is a critical response to cold stress. By reducing the volume of blood reaching the skin, the body conserves its internal core temperature. In a state of hyperthermia, vasoconstriction would prevent necessary heat loss, causing the internal temperature to rise even further and risking systemic damage.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
A stable blood pressure helps maintain the integrity of the blood-brain barrier. The barrier consists of tight junctions between endothelial cells, astrocytes, and a basement membrane. These structures are designed to regulate the movement of substances into the brain parenchyma. When blood pressure remains within a normal autoregulatory range, the physical pressure against these tight junctions is controlled, preventing the mechanical "stretching" or leaking of fluids and solutes into the delicate neural tissue.
Choice B rationale
Normal oxygen saturations, typically maintained above 95 percent, ensure that the endothelial cells of the blood-brain barrier receive adequate oxygen for metabolic processes. Hypoxia, or low oxygen, is what actually threatens the barrier. Under hypoxic conditions, the tight junction proteins can degrade, and inflammatory mediators are released, leading to increased permeability. Therefore, maintaining high oxygen levels is a protective factor that keeps the barrier sealed and functioning as a selective filter for the CNS.
Choice C rationale
A glucose level of 90 mg/dL is within the normal fasting range of 70 to 99 mg/dL. The brain requires a constant supply of glucose, which is transported across the blood-brain barrier via specific GLUT1 transporters. Normal physiological levels of glucose do not disrupt the structural integrity of the barrier. It is chronic hyperglycemia, seen in uncontrolled diabetes, that eventually damages the microvasculature and increases permeability through the formation of advanced glycation end products.
Choice D rationale
Inflammation and infection are primary causes of increased blood-brain barrier permeability. During an infection such as meningitis, pathogens and immune cells trigger the release of proinflammatory cytokines like tumor necrosis factor and interleukins. These substances cause the tight junctions between endothelial cells to loosen. This increased permeability allows white blood cells and antibiotics to enter the brain, but it also permits the entry of toxins and excess fluid, leading to potentially dangerous cerebral edema.
Correct Answer is C
Explanation
Choice A rationale
A cell that engulfs pathogens is known as a phagocyte, such as a macrophage or a neutrophil. These are specialized white blood cells that identify, ingest, and destroy foreign invaders through a process called phagocytosis. While an antigen may be present on the surface of the pathogen that the phagocyte consumes, the cell itself is an effector of the innate immune system and is not synonymous with the molecular structure of an antigen.
Choice B rationale
Mediators of inflammation include substances like histamines, leukotrienes, and prostaglandins that are released by mast cells and other leukocytes to initiate the inflammatory response. These chemicals increase vascular permeability and blood flow to the site of injury or infection. While antigens can trigger the release of these mediators during an allergic or immune response, they are distinct molecular entities that serve as the identification markers rather than the signaling chemicals themselves.
Choice C rationale
An antigen is any substance, typically a protein or polysaccharide, that the immune system recognizes as foreign and that subsequently triggers an immune response. Antigens can be found on the surfaces of viruses, bacteria, fungi, and pollen. Once detected, they stimulate the production of specific antibodies or the activation of T cells. The specificity of the immune response depends on the unique molecular shape of the antigen which fits with a specific receptor.
Choice D rationale
Proteins produced by B cells in response to an antigen are called antibodies or immunoglobulins. These Y-shaped proteins circulate in the blood and bind specifically to the antigen that triggered their production, marking it for destruction by other immune cells. The antigen is the target or the stimulus, whereas the antibody is the defensive protein produced by the body to neutralize or eliminate that specific threat from the internal environment.
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