The valves regulate {TAIL ~ fluid flow} to the second chamber in accordance with electrical signals from {HEAD ~ the heart} 
The valves regulate { TAIL ~ fluid flow } to the second chamber in accordance with electrical signals from { HEAD ~ the heart }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD