Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Orthostatic Hypotension ?
    ### Response:
    Orthostatic hypotension is a sudden fall in blood pressure that occurs when a person assumes a standing position. It is due to a lesion of the baroreflex loop, which senses a change in blood pressure and adjusts heart rate and activates sympathetic nerve system fibers to cause the blood vessels to narrow and correct blood pressure.
    