REGIONAL CEREBRAL BLOOD FLOW (RCBF RCBF): Regional cerebral blood flow monitoring may help boost the validity of the regional localization theory, in which specific parts of the brain control specific functions.. measure of the blood flow in a specific area of the brain, using positron emission tomography (PET scans) and/or single photon emission computed tomography.
If a dog goes on his back to you he is accepting you as his master. This is part of the answer but here's a little more in-depth version as reported by USA Today. In general, dogs lie on their back for three reasons.
Short answer: Wait until the penis shrinks back to size. Long answer: If in case your dog knots you, you need to wait because the male dog is ejecting his sperm into you. Meant or female mates, the dog is trying to eject sperms into the female so that the female may get pregnant and may have babies. Done to a human, it is biologically impossible to get pregnant by a dog.