The generation of an action potential in a sensory nerve fiber beginning with the stimulation of a Pacinian corpuscle involves the following steps:

1. A stimulus such as light touch, pressure, or vibration is applied to the Pacinian corpuscle. This is a type of mechanoreceptor found in the skin and other tissues, which is sensitive to changes in pressure or vibration.

2. This stimulus causes a change in the physical shape of the Pacinian corpuscle, which in turn leads to the opening of mechanosensitive ion channels in the membrane of the sensory neuron associated with the corpuscle.

3. The opening of these ion channels allows positive ions to flow into the neuron, creating a change in electrical potential known as a receptor potential. The size of this receptor potential increases with the intensity of the stimulus - for example, a stronger pressure or faster vibration will cause a larger receptor potential.

4. If the receptor potential reaches a certain threshold level (typically around -55 mV), it triggers the generation of an action potential. This is an all-or-nothing electrical signal that travels along the sensory neuron towards the central nervous system.

5. The action potential is generated at the first node of Ranvier, a point on the neuron where the insulating myelin sheath is interrupted. This allows for the rapid, saltatory conduction of the action potential along the neuron.

6. Once the action potential reaches the end of the neuron, it causes the release of neurotransmitters into the synaptic cleft, which can then stimulate the next neuron in the pathway.

7. The sensory information carried by this action potential is then processed by the central nervous system, leading to the perception of the original stimulus.

So, the correct answer is B. Light touch is applied to the Pacinian corpuscle, and a receptor potential is generated; as more receptors are brought into the receptive field, the size of the receptor potential increases; when it reaches 30 mV, an action potential is produced at the first node of Ranvier.

Question

The generation of an action potential in a sensory nerve fiber beginning with the stimulation of a Pacinian corpuscle involves the following steps:

1. A stimulus such as light touch, pressure, or vibration is applied to the Pacinian corpuscle. This is a type of mechanoreceptor found in the skin and other tissues, which is sensitive to changes in pressure or vibration.

2. This stimulus causes a change in the physical shape of the Pacinian corpuscle, which in turn leads to the opening of mechanosensitive ion channels in the membrane of the sensory neuron associated with the corpuscle.

3. The opening of these ion channels allows positive ions to flow into the neuron, creating a change in electrical potential known as a receptor potential. The size of this receptor potential increases with the intensity of the stimulus - for example, a stronger pressure or faster vibration will cause a larger receptor potential.

4. If the receptor potential reaches a certain threshold level (typically around -55 mV), it triggers the generation of an action potential. This is an all-or-nothing electrical signal that travels along the sensory neuron towards the central nervous system.

5. The action potential is generated at the first node of Ranvier, a point on the neuron where the insulating myelin sheath is interrupted. This allows for the rapid, saltatory conduction of the action potential along the neuron.

6. Once the action potential reaches the end of the neuron, it causes the release of neurotransmitters into the synaptic cleft, which can then stimulate the next neuron in the pathway.

7. The sensory information carried by this action potential is then processed by the central nervous system, leading to the perception of the original stimulus.

So, the correct answer is B. Light touch is applied to the Pacinian corpuscle, and a receptor potential is generated; as more receptors are brought into the receptive field, the size of the receptor potential increases; when it reaches 30 mV, an action potential is produced at the first node of Ranvier.

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