Which of the following components of a neuron is an insulative covering necessary for effective transmission of nerve impulses?
Myelin
Synapse
Axon
Dendrite
The Correct Answer is A
A. Myelin is a fatty substance that wraps around axons in many neurons. It acts as an insulative covering that speeds up the transmission of nerve impulses by enabling the signal to jump between gaps in the myelin (called nodes of Ranvier). This is the correct answer.
B. The synapse is the junction between two neurons where signals are transmitted. It is not involved in the insulative covering of a neuron.
C. The axon is the long, slender part of a neuron that transmits electrical signals, but it requires myelin to efficiently conduct those signals.
D. Dendrites are branched extensions of a neuron that receive signals from other neurons. They do not have an insulative function.
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Related Questions
Correct Answer is D
Explanation
A. The thyroid gland functions only as an endocrine gland. It secretes hormones like thyroxine (T4) and triiodothyronine (T3) into the bloodstream, but it does not have an exocrine function.
B. The pituitary gland is an endocrine gland that secretes hormones into the bloodstream but does not have exocrine functions.
C. The hypothalamus is involved in hormone production and regulation but is considered part of the brain rather than an endocrine or exocrine gland itself.
D. The pancreas functions as both an endocrine and exocrine gland. It produces insulin and glucagon (endocrine functions) and secretes digestive enzymes into the small intestine through ducts (exocrine function).
Correct Answer is B
Explanation
A. The parathyroid glands regulate calcium and phosphate levels in the blood through the release of parathyroid hormone (PTH), not testosterone.
B. The anterior pituitary gland regulates the release of testosterone through the secretion of luteinizing hormone (LH), which stimulates the testes to produce testosterone. This is the correct gland involved in testosterone regulation.
C. The posterior pituitary releases hormones like oxytocin and antidiuretic hormone (ADH), but it does not regulate testosterone production.
D. The thyroid gland is responsible for regulating metabolism through thyroid hormones (T3 and T4), not testosterone.
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