Which of the following will raise blood pressure?

A. GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter in the central nervous system, meaning it generally reduces neuronal excitability and does not play a role in excitatory neuromuscular transmission.
B. Glycine is also an inhibitory neurotransmitter, mainly in the spinal cord, and works to prevent over-excitation of neurons, not directly involved in neuromuscular transmission.
C. Acetylcholine is the primary neurotransmitter responsible for neuromuscular transmission. It binds to receptors on muscle cells, causing depolarization and triggering muscle contraction, thus playing an excitatory role.
D. Serotonin primarily functions in the brain to regulate mood, appetite, and sleep but does not play a direct role in neuromuscular transmission.

A. After passing through the proximal convoluted tubule, the filtrate enters the Loop of Henle, where further reabsorption of water and solutes occurs. This is the next step in the nephron's sequence.

B. The collecting duct comes much later in the nephron pathway, receiving filtrate after the distal convoluted tubule. It is not the immediate successor to the proximal convoluted tubule.

C. The glomerulus is the site where blood filtration begins, preceding the proximal convoluted tubule, so the filtrate does not return here.

D. Bowman's capsule collects the initial filtrate from the glomerulus before it enters the proximal convoluted tubule, making it an earlier step in the nephron process.