Complex sentence: Another exception is with certain deep muscle blood vessels, which dilate (rather than constrict) with an increase in sympathetic tone, this is because of the presence of more beta2 receptors, rather than alpha1, which are more frequently found on other vessels.
Split into simpler sentences: Another exception is with certain deep muscle blood vessels, which dilate (rather than constrict) with an increase in sympathetic tone. This is because of the presence of more beta2 receptors, rather than alpha1, which are more frequently found on other vessels.