Nokea
An example of a hormone that under certain circumstances is regulated by positive feedback is:
- A. calcitonin.
- B. histamine.
- C. oxytocin.
- D. melatonin.
Correct Answer: C
Rationale: Rationale:
1. Oxytocin is released during childbirth to stimulate uterine contractions.
2. As contractions increase, oxytocin secretion is further stimulated in a positive feedback loop.
3. This positive feedback mechanism amplifies the contractions until delivery.
4. Calcitonin regulates calcium levels, histamine is involved in allergic responses, and melatonin regulates sleep-wake cycles.
Summary:
- Calcitonin, histamine, and melatonin do not exhibit positive feedback regulation like oxytocin during childbirth.
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This cone-shaped gland is located in the head and is called the “biological clock.â€
- A. Posterior pituitary
- B. Hypothalamus
- C. Pineal
- D. Thymus
Correct Answer: C
Rationale: The correct answer is C: Pineal gland. The pineal gland is located in the brain and is often referred to as the "biological clock" due to its role in regulating the sleep-wake cycle through the secretion of melatonin. The posterior pituitary (choice A) is responsible for releasing hormones produced by the hypothalamus, not related to the circadian rhythm. The hypothalamus (choice B) is involved in regulating various physiological processes but is not directly associated with the circadian rhythm. The thymus (choice D) plays a role in the immune system, not in regulating the biological clock. Thus, the pineal gland is the correct answer as it specifically controls the circadian rhythm.
Which of the following is NOT a function of hormones?
- A. maintain homeostasis
- B. influence metabolism
- C. influence growth and development
- D. breaking down nutrients
Correct Answer: D
Rationale: The correct answer is D: breaking down nutrients. Hormones are chemical messengers that regulate various physiological processes in the body. Hormones do not directly break down nutrients; instead, they regulate the processes involved in nutrient breakdown. A: maintaining homeostasis is a function of hormones as they help regulate internal balance. B: influencing metabolism is a function of hormones as they regulate energy production and utilization. C: influencing growth and development is a function of hormones as they play a crucial role in the growth and maturation of cells and tissues.
Albuterol causes selective activation of β2 adrenergic receptors when administered in 'low doses,' mainly by inhalation. If very large doses of albuterol were given, or if the drug is administered intravenously, the effects caused by albuterol would look quite different and would resemble those of which one of the following drugs?
- A. Epinephrine
- B. Isoprenaline
- C. Norepinephrine
- D. Phenylephrine
Correct Answer: B
Rationale: Step 1: Albuterol selectively activates β2 adrenergic receptors in low doses.
Step 2: Isoprenaline is a non-selective beta-adrenergic agonist.
Step 3: Very large doses of albuterol or IV administration would lead to non-selective activation of beta receptors.
Step 4: Isoprenaline also activates both β1 and β2 receptors, causing a broad range of effects.
Step 5: Therefore, the effects of high-dose albuterol would resemble those of Isoprenaline, making B the correct answer.
Summary:
Choice A (Epinephrine) is incorrect because epinephrine primarily acts on both α and β adrenergic receptors, not just β2.
Choice C (Norepinephrine) is incorrect as it mainly acts on α adrenergic receptors, not β.
Choice D (Phenylephrine) is incorrect because it is a
Insulin and glucagon:
- A. are secreted by the beta cells of the islets of Langerhans.
- B. elevate blood glucose levels.
- C. are secreted in response to declining plasma levels of glucose.
- D. are secreted by the pancreas to regulate blood glucose.
Correct Answer: D
Rationale: The correct answer is D because insulin and glucagon are both hormones secreted by the pancreas to regulate blood glucose levels. Insulin is secreted by beta cells in response to high blood glucose levels, promoting glucose uptake by cells. Glucagon is secreted by alpha cells in response to low blood glucose levels, stimulating the release of stored glucose. Choices A and C are incorrect because insulin is secreted by beta cells, not glucagon, and they are secreted in response to high, not low, glucose levels. Choice B is incorrect because insulin lowers blood glucose levels, while glucagon raises them.
Monoamine oxidase enzyme (MAO) is responsible for:
- A. Adrenaline activation
- B. Adrenaline synthesis
- C. Adrenaline degradation
- D. Acetylcholine degradation
Correct Answer: C
Rationale: Monoamine oxidase enzyme (MAO) is responsible for the degradation of neurotransmitters like adrenaline. MAO breaks down adrenaline into inactive metabolites, regulating its levels in the body. This process is crucial for maintaining neurotransmitter balance. Choice A is incorrect because MAO does not activate adrenaline. Choice B is incorrect as MAO is not involved in adrenaline synthesis. Choice D is incorrect as MAO does not degrade acetylcholine, but rather neurotransmitters like serotonin, dopamine, and adrenaline.