freewheel. 1  a device in the transmission of a motor vehicle that automatically disengages the drive shaft whenever it begins to turn more rapidly than the engine. 2  a form of rear bicycle wheel that has a device freeing it from the driving mechanism, as when the pedals are stopped in coasting.
Ampullae are an important part of the water vascular system of starfish, which is the responsible for the animal's locomotion. The only function of the ampullae is to store the water that enters the vascular system and send it to the minuscule tube feet, located in the ventral side of the starfish's arms.he contraction of the muscles also causes the water stored in the ampullae to move to the tube feet, which are the locomotion organs of the starfish. Nerve cells connected to the ampullae and other parts of the vascular water system control the relaxation and contraction of the ampullae's muscle fibers.
The medulla oblongata often just referred to as the medulla, is the lower half of the brainstem continuous with the spinal cord. Its upper part is continuous with the pons. The medulla contains the cardiac, respiratory, vomiting and vasomotor centres dealing with heart rate, breathing and blood pressure.hough small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brainstem.