Study 3a Feedback Loops Homeostasis in MCAT Biological and Biochemical Foundations of Living Systems with focused flashcards that help you recognize the idea, recall the key rule, and apply it in practice-style prompts.
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Flashcard 1: Identify the classic human positive feedback example involving uterine contractions.
Answer: Oxytocin-driven labor (parturition). Oxytocin release amplifies contractions, creating a positive loop that progresses labor to delivery.
Flashcard 2: Which option best describes a regulated variable in homeostasis?
Answer: A measurable condition maintained within a narrow range. Regulated variables are essential parameters like blood pressure that homeostasis keeps stable for optimal function.
Flashcard 3: What is a positive feedback loop in physiological regulation?
Answer: A response that amplifies the initial change. Positive feedback intensifies a process to completion, like oxytocin enhancing uterine contractions during childbirth.
Flashcard 4: What is the response in a physiological feedback loop?
Answer: Effector action that changes the regulated variable. The response corrects the deviation detected by the sensor, bringing the system back toward the set point.
Flashcard 5: Identify the three core components of a homeostatic control loop.
Answer: Sensor, integrator (control center), effector. These components form the basic structure of feedback systems, detecting changes, processing information, and enacting responses.
Flashcard 6: Which option best defines an antagonist effector pair in homeostasis?
Answer: Two effectors that produce opposing effects on a variable. Antagonist pairs allow precise control by balancing increases and decreases in the regulated variable.
Flashcard 7: What is the primary stimulus for insulin secretion by pancreatic b^2 cells?
Answer: Increased blood glucose. Elevated glucose levels prompt insulin release to promote uptake and storage, restoring normoglycemia.
Flashcard 8: Which effectors primarily conserve or generate heat during hypothermia?
Answer: Shivering and cutaneous vasoconstriction. These responses reduce heat loss and increase heat production to restore normal body temperature.
Flashcard 9: Identify the classic positive feedback example involving blood vessel repair.
Answer: Platelet aggregation during blood clotting. Initial platelet activation releases factors that recruit more platelets, accelerating clot formation.
Flashcard 10: Which option best defines feedforward control in physiology?
Answer: Anticipatory response that occurs before a variable changes. Feedforward mechanisms preemptively adjust physiology, like salivation before eating to aid digestion.
Flashcard 11: What is the set point in a homeostatic control system?
Answer: Target value or range for a regulated variable. The set point represents the ideal physiological value that feedback mechanisms aim to restore when deviations occur.
Flashcard 12: What is the function of an effector in a homeostatic control system?
Answer: Carries out the response to adjust the variable. Effectors execute commands from the control center to restore the regulated variable to its set point.
Flashcard 13: What is homeostasis in physiology?
Answer: Maintenance of internal conditions near a set point. Homeostasis ensures physiological stability by regulating variables like temperature and pH around optimal levels despite external changes.
Flashcard 14: Identify the term for stable oscillations around a set point in homeostasis.
Answer: Dynamic equilibrium. Dynamic equilibrium describes the steady state where variables fluctuate minimally around the set point.
Flashcard 15: Which effectors primarily increase heat loss during hyperthermia?
Answer: Sweating and cutaneous vasodilation. These mechanisms enhance evaporative cooling and heat radiation to counteract elevated body temperature.
Flashcard 16: What is the primary stimulus for glucagon secretion by pancreatic b^1 cells?
Answer: Decreased blood glucose. Low glucose triggers glucagon to mobilize stores and raise levels, preventing hypoglycemia.
Flashcard 17: What is a negative feedback loop in homeostatic regulation?
Answer: A response that counteracts the initial change. Negative feedback restores equilibrium by opposing deviations, such as insulin lowering high blood glucose.
Flashcard 18: What is the thermoregulatory control center in humans?
Answer: Hypothalamus. The hypothalamus integrates thermal signals and coordinates responses to maintain core body temperature.
Flashcard 19: What is the function of an integrator (control center) in homeostasis?
Answer: Compares to set point and generates an output signal. The integrator evaluates sensor input against the set point to initiate appropriate corrective actions via effectors.
Flashcard 20: What is the function of a sensor (receptor) in a feedback loop?
Answer: Detects a change in a regulated variable (stimulus). Sensors monitor environmental or internal changes and relay information to maintain homeostasis.
Flashcard 21: What is the stimulus in a physiological feedback loop?
Answer: Deviation of a regulated variable from its set point. The stimulus triggers the feedback loop by signaling a need for adjustment to maintain homeostasis.
Flashcard 22: What is the net effect of glucagon on blood glucose?
Answer: Increases blood glucose. Glucagon stimulates glycogenolysis and gluconeogenesis to elevate blood sugar during fasting states.
Flashcard 23: What is the net effect of insulin on blood glucose?
Answer: Decreases blood glucose. Insulin facilitates glucose uptake by cells and inhibits gluconeogenesis, normalizing high blood sugar.
Flashcard 24: Choose the phrase that best defines allostasis in regulation.
Answer: Stability through change by adjusting the set point. Allostasis achieves stability by adapting set points to chronic stressors, differing from fixed homeostasis.