Question

Passage IV (Questions 114-117) Electrical impubses are transferred from one neuron to another via a synapse. Synapses can be electrical or chemical. In response to an electrical stimalus such as an action potential the presynaptic neuron in a chemical synapse releases a neuro- transmitner across a small space between the two neurons known as a symaptic cief. Neurotransmitiers may have excita- ory or inhibitory effects depending upon the type of membrane bound protein receptors possessed by the postsynaptic neuren For instance, the neunceransmitter acetykholine binkds to nico- tinic acetylcholine receptors creating a conformational change which allows small cations to rush into the cell through the receptor. The receptor remains open only for a fraction of a second. The greatest number of cations flowing through the receptor are Na" sons, since they have the largest electrochem ical gradicnst, Once the receptor is closed, acetylcholine is released and then degraded to choline and acetic acid by acetyl- cholinesterase in the basal lamina. The choline is then taken up by the presynaptic cell and recycled. A second type of acetylcholine receptor, the muscarinic acetylcholine receplor. works more slowly through the activa- tion of a G protein which in turn opens K channels in the posisynaptic membrane. An action potential in the post synap- tic cell is then inhibited. The G protein coetains three subunits, a, B, and y A propased mechanism of the G protein is shown in Figure L Synaptic Cleft Acetylcholine G protein GDP) GTP) Muscannic Acivation of K' channel eceplor GTP GDP) Cysosol Figure 1 Mechanism of a G protein

The right answer is (D)
Please explain. I don't understand how K+ could be effluxing rather than influxing

Answer 1