12.16.3 The Ear and Equilibrium

Question 1

The Ear and Equilibrium

Answer 1

• Three organs of balance that are found in the animal kingdom are the lateral line of fishes, the statocyst of crustaceans, and the human ear.
• The lateral line consists of organs containing a moveable cupula, located in ridges along the outside of the body.
• The statocysts of crustaceans contain statoliths, stones that aid the organism in obtaining positional information.
• The inner ear of humans contains cupulae and otoliths, both of which provide orientation information.

Question 2

lateral line

Answer 2

• The lateral line of fishes is used for maintaining equilibrium in their watery environment. The lateral line consists of organs containing a moveable cupula, located in ridges along the outside of the body. The cupula contain hair cells with stereocilia that bend when the fish moves through water. When a cell is bent, it results in the firing of an action potential through the nervous system to the brain. Only certain cells are bent and depolarized by water from a given direction, thus enabling the fish to orient itself.

Question 3

statocyst

Answer 3

• The statocyst of crustaceans consists of a chamber of
  statoliths surrounded by hair cells. The statoliths are
  comprised of grains of sand or similar material. The force of gravity acts upon the statoliths, causing them to rest at a particular area of the organ. Depending on their location, certain hair cells are depolarized, providing the organism with orientation information.

Question 4

note

Answer 4

• The human ear contains organs of hearing as well as of balance. The organs of balance are located in the inner ear, at the base of the semicircular canals.

Question 5

ampullae

Answer 5

• Structures at the base of the semicircular canals called ampullae contain hair cells, which are embedded in cupulae. Positional information is gained when fluid of the inner ear pushes up against the hair cells, causing them to bend.

Question 6

otoliths

Answer 6

• Otoliths embedded in the gelatinous matrix, provide
  additional orientation information. Like the otoliths of
  crustaceans, they move in response to gravity and trigger hair cells to generate an action potential.

Question 7

The ampullae and otoliths are

Answer 7

• structures of the inner ear that provide positional information.

Question 8

Which of the following more accurately describes how the lateral line of fishes works?

Answer 8

• Stereocilia of hair cells bend when fluid moves over them, triggering an action potential.

Question 9

A lobster obtains orientation information from an organ called a

Answer 9

• statocyst

Question 10

Statocysts

Answer 10

• are organs that function in equilibrium in invertebrates.

Question 11

The ____________________ is the gelatinous mass in which hair cells are embedded.

Answer 11

• cupula