Final answer:
Neurotransmitter acetylcholine and the lipid myelin. Acetylcholine is essential for signal transmission in the nervous system, while myelin insulates axons for efficient impulse conduction (Options B and C).
Step-by-step explanation:
The student's question relates to the neurotransmitter known as acetylcholine, which is released by neurons both in the central nervous system (CNS) and the peripheral nervous system (PNS).
Acetylcholine plays a vital role in transmitting signals across synapses, which are the junctions between neurons.
The synthesis and release of this neurotransmitter facilitate the self-propagating change in electrical potential of a neuron's membrane, termed action potential.
Myelin, on the other hand, is a lipid produced by oligodendrocytes in the CNS and Schwann cells in the PNS.
Myelin forms a sheath around axons, which significantly improves the efficiency of electrochemical impulse transmission along neurons.
Conditions such as Alzheimer's disease are often associated with disruptions in acetylcholine function.
Moreover, myelination plays a critical role in ensuring high-speed signal conduction and is crucial for proper nervous system function.
The gray matter is where all synapses are located, which is essential for transmitting signals along the spinal cord and brain.
Hence, the correct answers are Options B and C.