Interstate 635 (Texas) Interstate 635 (Texas) Interstate 635 (I-635) is a partial loop around Dallas, Texas, in the United States between I-20 in Balch Springs and State Highway 121 (SH 121) at the north entrance of the Dallas-Fort Worth International Airport in Grapevine. It intersects I-35E at exits 27B–C, but does not connect with I-35W. It is known locally as the Lyndon B. Johnson Freeway, or LBJ, named after Lyndon B. Johnson, the former U.S. Senator from Texas, 37th Vice President, and the 36th President of the United States. Where I-635 ends at I-20, I-20 continues the LBJ Freeway name heading west. Because
Referred pain local pain (pain at the site of stimulation) is intensified the referred pain is intensified as well. Criticism of this model arises from its inability to explain why there is a delay between the onset of referred pain after local pain stimulation. Experimental evidence also shows that referred pain is often unidirectional. For example, stimulated local pain in the anterior tibial muscle causes referred pain in the ventral portion of the ankle; however referred pain moving in the opposite direction has not been shown experimentally. Lastly, the threshold for the local pain stimulation and the referred pain stimulation are different,