Carries impulse across the synaptic cleft and triggers impulse in the next neuron

Carries impulse across the synaptic cleft and triggers impulse in the next neuron

• A. Neurotransmitter
• B. Neuron
• C. Reflex action
• D. Sensory neuron

Answer: (A)

Signals at chemical synapses are transmitted by neurotransmitters. When a nerve impulse reaches the end of a neuron, it triggers the release of neurotransmitter molecules from vesicles into the synaptic cleft. These chemicals diffuse across the gap and bind to receptors on the membrane of the next neuron. This binding opens ion channels and alters the postsynaptic membrane potential, often producing an impulse in the next neuron if the threshold is reached. In this way, the chemical messenger across the synapse starts the signal in the subsequent neuron. The other options describe cells or types of neural responses, not the chemical carrier across the synapse. A neuron is the cell that conducts impulses, a reflex action is the body's automatic response, and a sensory neuron is a neuron that detects stimuli—none of these are the messenger that crosses the synaptic gap.

Signals at chemical synapses are transmitted by neurotransmitters. When a nerve impulse reaches the end of a neuron, it triggers the release of neurotransmitter molecules from vesicles into the synaptic cleft. These chemicals diffuse across the gap and bind to receptors on the membrane of the next neuron. This binding opens ion channels and alters the postsynaptic membrane potential, often producing an impulse in the next neuron if the threshold is reached. In this way, the chemical messenger across the synapse starts the signal in the subsequent neuron.

The other options describe cells or types of neural responses, not the chemical carrier across the synapse. A neuron is the cell that conducts impulses, a reflex action is the body's automatic response, and a sensory neuron is a neuron that detects stimuli—none of these are the messenger that crosses the synaptic gap.