Nokea
Cellular responses to hormones that initiate second-messenger systems include ________.
- A. possible activation of several different second-messenger systems
- B. cyclic AMP phosphodiesterase formation of an active second messenger
- C. formation of a specific protein kinase that acts on a series of extracellular intermediates
- D. hormone binding to intracellular receptors
Correct Answer: A
Rationale: The correct answer is A because cellular responses to hormones initiating second-messenger systems can activate various pathways. Different hormones can utilize different second messengers such as cAMP, cGMP, IP3, and DAG. This diversity allows for a wide range of responses in target cells.
Choice B is incorrect because cyclic AMP phosphodiesterase degrades cAMP, not forms an active second messenger.
Choice C is incorrect as it describes the mechanism of a specific protein kinase, which is not a characteristic of second-messenger systems.
Choice D is incorrect since hormone binding to intracellular receptors typically leads to gene transcription regulation, not direct activation of second-messenger systems.
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Diabetes mellitus occurs due to deficiency of:
- A. Glucagon
- B. Thyroxin
- C. Insulin
- D. Melatonin
Correct Answer: C
Rationale: Step-by-step rationale for why choice C (Insulin) is correct:
1. Insulin is a hormone produced by the pancreas that regulates blood sugar levels.
2. Diabetes mellitus is a condition characterized by high blood sugar levels due to inadequate insulin production or ineffective use of insulin.
3. The deficiency of insulin leads to the inability to properly regulate blood sugar levels, resulting in diabetes mellitus.
4. Glucagon (choice A) is a hormone that increases blood sugar levels, so its deficiency would not cause diabetes.
5. Thyroxin (choice B) is a hormone produced by the thyroid gland and is not directly related to diabetes.
6. Melatonin (choice D) is a hormone that regulates sleep-wake cycles and is not involved in blood sugar regulation.
Summary:
Insulin is the correct choice because its deficiency directly leads to diabetes mellitus, while the other choices do not play a significant role in the development of this condition.
Which nerve is NOT involved in the efferent (motor) swallow reflex?
- A. trigeminal
- B. vagus
- C. facial
- D. hypoglossal
Correct Answer: B
Rationale: The correct answer is B: vagus. The efferent (motor) swallow reflex involves motor nerves that control swallowing muscles. The vagus nerve (cranial nerve X) is primarily responsible for the afferent (sensory) component of the swallow reflex, while the efferent component is carried out by other cranial nerves such as the glossopharyngeal (IX), facial (VII), and hypoglossal (XII) nerves. Therefore, the vagus nerve is not directly involved in the efferent motor response during swallowing. Trigeminal (V), facial (VII), and hypoglossal (XII) nerves play essential roles in the motor aspects of swallowing, making them incorrect choices.
Epinephrine and norepinephrine from the adrenal medulla will produce the same results as the _____ nervous system.
- A. sympathetic
- B. parasympathetic
- C. somatic
- D. central
Correct Answer: A
Rationale: The correct answer is A: sympathetic. Epinephrine and norepinephrine are neurotransmitters released by the sympathetic nervous system. They activate the fight-or-flight response, increasing heart rate, dilating airways, and redirecting blood flow to muscles. The sympathetic nervous system prepares the body for action in response to stress or danger. Choices B, C, and D are incorrect because parasympathetic regulates rest and digest functions, somatic controls voluntary movements, and central refers to the brain and spinal cord, not a division of the autonomic nervous system like sympathetic.
What is meant by the term biodiversity?
- A. an increase in the number of different species that live in an area
- B. how organisms and their environment interact
- C. the number of different animals that live in an area
- D. the number of different species that live in an area
Correct Answer: D
Rationale: The correct answer is D because biodiversity refers to the variety of living organisms in an ecosystem, specifically the number of different species present. This term encompasses all forms of life, from bacteria to plants to animals. Choice A is incorrect as it only focuses on the increase in the number of species, not the overall diversity. Choice B is incorrect as it describes the interaction between organisms and their environment, not the diversity of species. Choice C is incorrect as it limits biodiversity to only animals, neglecting the importance of other living organisms in an ecosystem.
Hyoscine produces all of the following actions EXCEPT:
- A. Sedation
- B. Antiemetic action
- C. Stimulation of the respiratory center
- D. Increase of salivary secretion
Correct Answer: D
Rationale: Hyoscine, also known as scopolamine, is an anticholinergic drug that acts by blocking muscarinic receptors. It produces sedation by crossing the blood-brain barrier and affecting the central nervous system. Its antiemetic action is due to its ability to inhibit the vomiting center in the brain. Stimulation of the respiratory center is not a typical action of hyoscine. Lastly, hyoscine decreases salivary secretion due to its anticholinergic effects. Therefore, the correct answer is D (Increase of salivary secretion) as it is inconsistent with the pharmacological actions of hyoscine.