Final answer:
Nicotinic receptors are located in autonomic ganglia, NMJs, and some CNS synapses, and they act as ligand-gated ion channels to depolarize cells when acetylcholine binds. These receptors are distinct from muscarinic receptors and are crucial in the function of the autonomic nervous system and muscle contraction.
Step-by-step explanation:
Nicotinic receptors are a type of acetylcholine receptor protein characterized by their ability to bind to nicotine; they are also known as ionotropic receptors. They are found in various locations, including all autonomic ganglia of the sympathetic and parasympathetic systems, neuromuscular junctions (NMJs), and some central nervous system synapses. Nicotinic receptors act as ligand-gated ion channels and are responsible for the depolarization of cells following acetylcholine (ACh) binding. This process triggers nerve impulses in muscle cells or postsynaptic potentials in neurons.
Unlike nicotinic receptors, muscarinic receptors, which are associated with sweat glands and the blood vessels associated with skeletal muscles, are G protein-coupled receptors. Acetylcholine is the primary neurotransmitter for both nicotinic and muscarinic receptors, but whereas the former directly opens ion channels, the latter affects cells through a second-messenger cascade. Moreover, there is no cross-reactivity between the two receptor types, meaning nicotine cannot activate muscarinic receptors, and vice versa with muscarine.
Finally, in the cardiovascular system, the nicotinic receptor plays a role that does not conform to standard competitive projections. An example is that stimulating these receptors could potentially affect heart rhythm, with the sympathetic nervous system affecting systemic blood pressure.