1. An enlargement at one end of each of the semicircular canals of the inner ear. Each ampulla contains a group of receptors—sensory hair cells—embedded in a gelatinous cap (cupula), which detects movement in one particular dimension, corresponding to the plane of the canal. Movement of the head causes the cupula (and the hairs within it) to bend in a direction opposite to that of the head movement (see illustration); this stimulates nerve impulses in the receptors, which are interpreted by the brain as movement in a particular dimension.
2. Any small vesicle or saclike process.
3. (ampulla of Lorenzini) See electroreceptor.
Ampulla
An inflatable sac at the end of each tube foot in the echinoids (Echinoidea). It controls water pressure in the tube foot when the muscles in its walls are contracted.
- neutron degeneracy
- neutron diffraction
- neutron drip
- neutron excess
- neutron halo
- neutron interferometer
- neutron log
- neutron moisture meter
- neutron number
- neutron optics
- neutron scattering
- neutron soil-moisture probe
- neutron spin echo
- neutron star
- neutron temperature
- neutron–gamma sonde
- neutron–neutron sonde
- neutrophil
- Neville’s Cross, Battle of (17 October 1346)
- Nevilly, Treaty of
- New Academy
- New Australians
- Newcastle, Thomas Pelham-Holles, 1st Duke of (1693–1768)
- new classical economics
- Newcomb, Simon