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Somatosensory System

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Christopher Perumalla

1General principles of sensory physiology2The somatosensory systemSensory system deals with what you perceive through touch smell sound vision and hearing This is all possible due to the existence of specialized sensory receptors that can detect specific energy from the environment An example are photoreceptors found in the eyes to detect light1General principles of sensory physiologyAReceptor physiologyThe sensory receptors are specialized nerve endings or a separate cell that detects a sensory stimulus such as touch Instead of post synaptic protein receptors we have sensory receptors that receive signal from the outside touch vision etc These signals will be transmitted to the CNSThe sensory receptors are embedded in sensory cell membranesThey detect specific signalsThe receptors proteins of the sensory cells will change shape when specific energy chemical mechanical is received which will allow a chain of events to occurHow does this signal get transmitted We know that there needs to be the generation of an action potential at some point to transmit the signal to the brainFor example for touch there is pressure applied to the skinThis pressure opens ion channels in the membrane of the sensory neurons and generate depolarizing currentThe actual sensory neuron does not have to generate an action potential if there is the release of vesicles containing neurotransmittersThe stimulus changes the membrane potential of the sensory receptor cell and opens calcium channels which in turn trigger the release of vesiclesThe signal is eventually carried to the CNSThe next cell in line will produce an action potential which will carry the signal to the CNS The depolarizing current caused by the stimulus does not produce any action potential The current travels throughout the membrane passively depolarizing the membrane sufficiently which allow influx of calcium ions triggering the exocytosis of vesicles We have a sensory cell releasing vesicles to the neighboring neuron and then this neuron produces an action potential
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