Which of the following best des best describes a hormone?
A chemical messenger that is triggered by the binding of a ligand on the cell surface and causes a change in DNA transcription.
Junctions between cells interconnecting their cytoplasm
A chemical messenger transported by the bloodstream that stimulates target cells in another organ often a good distance away.
Chemical messengers that travel across a synapse to stimulate another cell
Chemical messengers that diffuse from their point of origin locally to affect other cells physiology.
The Correct Answer is C
A. A chemical messenger that is triggered by the binding of a ligand on the cell surface and causes a change in DNA transcription: This describes the mechanism of some hormones or intracellular signaling molecules, particularly steroid hormones, but it is not a complete definition of a hormone itself.
B. Junctions between cells interconnecting their cytoplasm: This describes gap junctions, which allow direct cytoplasmic communication between adjacent cells. It is a structural feature, not a hormone.
C. A chemical messenger transported by the bloodstream that stimulates target cells in another organ often a good distance away: This accurately defines a hormone. Hormones are secreted by endocrine glands into the blood and travel to distant target cells, eliciting specific physiological responses.
D. Chemical messengers that travel across a synapse to stimulate another cell: This describes neurotransmitters, which act locally at synapses rather than being transported through the bloodstream.
E. Chemical messengers that diffuse from their point of origin locally to affect other cells physiology: This describes paracrine signaling, which is local and short-range. Hormones, in contrast, typically act on distant cells via the circulatory system.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. 5:Hemoglobin molecules do not bind five oxygen molecules; this exceeds their structural capacity.
B. 4:Each hemoglobin molecule has four heme groups, and each heme can bind one oxygen molecule. Therefore, one hemoglobin molecule can carry a maximum of four oxygen molecules.
C. 2:Hemoglobin can carry more than two oxygen molecules; two would only represent half-saturation of the molecule.
D. 6:Six oxygen molecules exceed the binding capacity of hemoglobin and are not physiologically possible.
E. 3:Hemoglobin can bind three oxygen molecules, but this is not the maximum capacity. Four is the full complement when fully saturated.
Correct Answer is A
Explanation
A. Systolic pressure:The top number in a blood pressure reading represents systolic pressure. It reflects the maximum arterial pressure during ventricular contraction and indicates how forcefully the heart pumps blood into the arteries.
B. Pulse pressure:Pulse pressure is the difference between systolic and diastolic pressures. It is calculated from both numbers, not represented solely by the top number.
C. Mean arterial pressure:Mean arterial pressure (MAP) is the average arterial pressure during a cardiac cycle, calculated using both systolic and diastolic values. It is not indicated by the top number alone.
D. Diastolic pressure:Diastolic pressure is the bottom number in a blood pressure reading. It reflects the arterial pressure when the heart is relaxed, not the top number.
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