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Definition
When receptor potentials reach a certain level it releases neurotransmitter across the space and it interacts with the sensory neuron. Depending on how much neurotransmitter is released, the potential in the neuron will get bigger and bigger. This is the generator potential.
The generator potential is on a nerve cell. So, if the generator potential reaches threshold it will generate an all or nothing action potential. |
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Term
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Definition
a change in the membrane potential of a receptor in response to some sort of stimulus.
These are graded potentials and distribution decreases with distance along the membrane. |
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| Describe the basic mechanism sequence of action |
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Definition
1) Stimuli come in through an accessory structure
2) This creates a depolarization in the receptor potential
3) The receptor cell releases neurotransmitter to the 2nd order neuron
4) This creates a generator potential.
5) If the generator potential gets large enough, it sets off an action potential. |
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| Define modality, quality, and quantity of sensory receptor cells |
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Definition
Modality: type of information that a particular sense organ encodes
Quality: properties of a stimulus
Quantity: intensity of stimulus |
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| Phasic receptors are rapidly adapting. They are good at telling you when something is changing. Action potentials will occur at the onset and end of the stimulus. |
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| Tonic receptors are slowly adapting. They are good at continuous monitoring of the external environment. Action potentials will fire as long as the generator potential is above threshold. |
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| What structure gives the pacinian corpuscle the very rapidly adapting feature? Why? |
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Definition
| The free nerve ending is surrounded by an onion like structure. When you apply pressure, the stimulus is transferred down to the nerve ending, but pressure is also displaced laterally. The amount of pressure on the nerve ending decreases quickly. |
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| Discuss the importance of the distance from the stimuli to the first node of ranvier. |
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Definition
| You loose current over distance. Specifically, you loose 63% of the current per time constant. Since the action potential will start at the first node of ranvier, the generator potential must be at or above threshold when it reaches that point. If not, an action potential will not occur and the brain will not know what is going on. |
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Definition
| The receptor surface has lots of channels that can act independently. If a stimulus is applied simultaneously to two differnt channels, they add together. If both stimuli are excitatory, this results in an increased generator potential. |
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| The size of the generator potential is proportional to... |
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Definition
| the stimulus strength. The size of the generator potential will taper off close to the maximum stimulus strength. |
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Definition
| The area or region of tissue which when stimulated causes the sensory neuron to change its electrochemical properties (depolarization or hyperpolarization). |
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| Discuss complex receptor fields |
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Definition
| Receptor fields can have directional sensitivity, in which the neuron is sensitive to stimuli in one direction but not the other. This is a type of lateral inhibition which allows us to sharpen a stimulus. |
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