Which of the following mechanisms is an example of negative feedback in the endocrine system?
The release of oxytocin during childbirth
The activation of the sympathetic nervous system during stress
The regulation of blood glucose levels by insulin and glucagon
The release of adrenaline during exercise
The Correct Answer is C
A. The release of oxytocin during childbirth: This is the classic example of positive feedback. Uterine contractions stimulate the release of oxytocin, which causes stronger contractions, which stimulates more oxytocin, continuing until delivery is complete.
B. The activation of the sympathetic nervous system during stress: This is a neurological "fight or flight" response. While it involves hormones (epinephrine), the mechanism of rapidly ramping up the body's alert state is not a homeostatic negative feedback loop (which aims to reverse a change).
C. The regulation of blood glucose levels by insulin and glucagon: Negative feedback works to reverse a deviation from the set point. If blood glucose rises, insulin is released to lower it. If blood glucose drops, glucagon is released to raise it. The system works to negate the stimulus (high or low sugar) to maintain balance.
D. The release of adrenaline during exercise: Similar to choice B, this is a response to increased demand (feed-forward) rather than a loop designed to keep adrenaline levels constant.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Cardiac muscle:Cardiac muscle is found only in the heart. It is striated and involuntary with unique intercalated discs and autorhythmicity; it is notthe muscle that lines most hollow organs (like intestines, bladder, blood vessels).
B. Smooth muscle:Smooth muscle is non-striated, involuntary muscle located in the walls of hollow organs (e.g., gastrointestinal tract, bladder, uterus), blood vessel walls, and bronchi. It generates slow, sustained contractions for peristalsis, vasomotion, and other automatic functions.
C. Skeletal muscle:Skeletal muscle is striated and under voluntary control, attached to bones to produce movement; it is not the primary muscle of hollow organ walls.
D. Striated muscle:“Striated muscle” is a descriptive term that includes skeletal and cardiac muscle (both have striations). Since the question asks specifically about involuntary muscle in hollow organs, striated muscle is not the correct category.
Correct Answer is D
Explanation
A. Basement membrane:This is a thin, non-cellular adhesive layer that anchors the epidermis to the dermis. It does not contain its own blood supply or complex nerve endings.
B. Hypodermis:While the hypodermis (subcutaneous tissue) does contain larger blood vessels and nerves, the question describes the characteristics of the "skin." The dermisis the classic answer for the vascularized and innervated layer of the skin itself, often contrasted with the avascular epidermis.
C. Epidermis:The epidermis is avascular(has no blood vessels) and receives its nutrients via diffusion from the dermis below. It has free nerve endings but lacks the rich vascular network found in the dermis.
D. Dermis:The dermis is highly vascular (rich in blood capillaries) to regulate temperature and provide nutrients. It is also packed with sensory receptors (nerve endings) for touch, pressure, heat, and pain.
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