A neurotransmitter released from one neuron causes an influx of negatively charged ions into the cytosol of an adjacent neuron. In the adjacent neuron, the influx of these ions would most likely:

Question

A neurotransmitter released from one neuron causes an influx of negatively charged ions into the cytosol of an adjacent neuron.  In the adjacent neuron, the influx of these ions would most likely:

Quizplus · Accepted Answer

11ecba2d_1023_5bb5_a3bf_83e127293a31_MD0008_00 The vertebrate nervous system is divided into the central and peripheral nervous systems. Within both divisions, neurons transport electrical signals to other neurons and tissues via action potentials (APs). A synapse, which can be chemical or electrical, is a junction formed between the axon terminal of a pre-synaptic neuron and the dendrites of a post-synaptic neuron. An AP travels down the axon of a pre-synaptic neuron until it reaches the axon terminals. At chemical synapses, the AP induces the release of neurotransmitters from the pre-synaptic neuron into the synaptic cleft (ie, the space between the pre-synaptic axon terminal and the post-synaptic dendrite). Neurotransmitters traverse the synaptic cleft to bind receptors on the post-synaptic membrane. This binding causes the opening of ion channels in the post-synaptic neuron, facilitating the movement of charged ions into or out of this cell. As a result, the resting membrane potential (−70 mV) of the post-synaptic neuron is altered. An AP is initiated in the post-synaptic neuron only if the membrane potential becomes more positive and exceeds a certain threshold (−55 mV). Depending on the neurotransmitter's effect on the post-synaptic neuron, synapses can be classified as excitatory or inhibitory. At an excitatory synapse, the pre-synaptic neuron releases neurotransmitters that cause an influx of positively charged ions (Na⁺) into the post-synaptic neuron. These ions cause the resting membrane potential of the post-synaptic neuron to become more positive, or to depolarize, which promotes AP initiation. In contrast, inhibitory synapses release neurotransmitters that affect the post-synaptic neuron by causing either an influx of negative ions (Cl⁻) or an efflux of positive ions (K⁺). The exit of positive ions or entry of negative ions into the post-synaptic neuron causes the cell's membrane potential to become more negative, or to hyperpolarize, which inhibits AP initiation. In this scenario, a neurotransmitter released from one neuron causes an influx of negatively charged ions into an adjacent (post-synaptic) neuron. This influx would cause the adjacent neuron's membrane potential to become more negative, hyperpolarizing the post-synaptic membrane potential and inhibiting AP initiation (Choices A, B, and C). Educational objective: At inhibitory synapses, pre-synaptic neurons release neurotransmitters that cause either an influx of negative ions into the post-synaptic neuron or an efflux of positive ions out of the post-synaptic neuron. This causes hyperpolarization of the membrane potential and inhibits action potential initiation in the post-synaptic neuron.

A Neurotransmitter Released from One Neuron Causes an Influx of Negatively