Do not write paragraphs. Be clear and concise. oo Verizon 12:32 AM * 91%-. Outli

Question

Do not write paragraphs. Be clear and concise. oo Verizon 12:32 AM * 91%-. Outline COMPLETELY a single pathway from a specific sensory receptor to the brain and back to an effector organ. Include Specific input that causes the sensory receptor to be activated first, second (third) order sensory neurons and tracts (where they are located, where they synapse, if they cross over or not) What happens in the brain- be specific How the motor output travels (upper and lower motor neurons) Between the lower order neuron and effector include how an action potential is generated and travels, neurotransmitter release and response of effector organ (skeletal muscle) and how it contracts (include details) Reply & 25 Mail Calendar Files People

Explanation / Answer

I would like to discuss about the pathway of touch.

The receptors for touch sensation are free nerve endings located all over the skin. The sensation of touch is transmitted along the spinothalamic tracts. The anterior spinothalamic tract carries information about crude touch and posterior spinothalamic tract carries information about pain and temperature.

These spinothalamic tracts uses three neurons to convey the information from the periphery to higher center. Pseudounipolar neurons in the dorsal root ganglion have axons that lead from the skin into the dorsal spinal cord. Here, they synapse with secondary neurons in the substantia gelatinosa of Rolando. Then, the axons of the tract cells cross over (decussate) to the opposite side of the spinal cord. The axons travel up the length of the spinal cord into the brainstem, in the rostral ventromedial medulla. The neurons ultimately synapse with third order neurons in several nuclei of the thalamus. From there, signals go to sensory cortex.

Processing of information takes place in the cerebral cortex. Then, the signals for the motor response of the brain to the effector organs travel through pyramidal tracts. Pyramidal tracts consists of upper order and lower order neurons. These pyramidal tracts are also known as corticospinal tracts. These tracts decussate in the medulla to the opposite side. These tracts travel down the spinal cord along the white matter of spinal cord till it reaches a vertebral level of the muscle it innervates.

The action potential travels along these corticospinal tracts. When it reaches the presynaptic membrane of neuromuscular junction, it causes release of neurotransmitters in the synaptic cleft. These neurotransmitters bind with receptors in the post synaptic membrane and causes release of calcium from sarcoplasmic reticulum. Calcium binds with troponin which in turn exposes myosin binding site on actin. Myosin binds with actin and excitation contraction coupling takes place.

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