Mechanoreceptors

Question 1

What are Mechanoreceptors?

Answer 1

Sensory receptors that detect mechanical stimuli; changes in touch and pressure.

Question 2

What are Free Nerve Endings?

Answer 2

Mechanoreceptors that respond to light touch, phasic.

Question 3

What are Pacinian Corpuscles?

Answer 3

Mechanoreceptors that respond to deep pressure and vibrations, located in the nerve endings of the skin, consist of a concentric layer of connective tissue wrapped around the peripheral terminal of an afferent neuron, phasic.

Question 4

What are Ruffini Endings?

Answer 4

Mechanoreceptors that respond to deep pressure, wide receptive field, phasic.

Question 5

What are Meissner’s Corpuscle?

Answer 5

Mechanoreceptors that respond to light touch and pressure, lie just beneath the skin with a small receptive field, phasic.

Question 6

What are Stretch Receptors?

Answer 6

A tonic receptor commonly found in the walls of tissues/organs that can be distended (muscle, stomach); stretching deforms them and they depolarize [Stretching in stomach is interpreted as fullness].

Question 7

What are Hair Cells?

Answer 7

Modified epithelial cells that are used for equilibrium and hearing (sense of movements of internal fluid) and in the lateral line system - sense movements of external fluid.

Question 8

What are common features of Hair Cells?

Answer 8

1. Receptor cells do not have axons
2. Afferents project to CNS
3. Receptor cells release neurotransmitter (glutamate)
4. Cells bath in endolymph
5. Depolarized by inward movement of potassium
6. Hair cells are always firing (continuous secretion of some kind of neurotransmitter)

Question 9

What is Endolymph?

Answer 9

A liquid high in potassium concentration (meaning extracellular fluid is low in potassium)

Question 10

True or False: In humans, the hair cell only synapses onto afferent neurons.

Answer 10

False, hair cells in humans can form synapses with efferent neurons.

Question 11

What are neuromasts? (Lateral Line System)

Answer 11

A mechanoreceptive organ that allows the sensing of mechanical changes in water (consists of cupula and stereocilli), set in pits and canals along the side of the body; the lateral line system consists of a row of them.

Question 12

What kind of ion channels does the Lateral Line System (in Fish) have?

Answer 12

Mechanically gated ion channels in hair cell membrane that cause depolarization or hyperpolarization.

Question 13

What are Proprioceptors?

Answer 13

(Example: Hair cells) Maintains body balance and position.

Question 14

What is a Statocyst?

Answer 14

An organ of equilibrium (orientation of gravity) found in invertebrates (mollusks) that is important for life in water. A simple system like lobsters deals only with gravity while a more complex, like squids and octopus, deals with gravity and acceleration.

Question 15

What are hairs in the inner ear embedded in?

Answer 15

The gelantinous cupula; which is embedded in enodlymph.

Question 16

What do 3 Semicircular canals provide?

Answer 16

3D sensitivity; angular motion of the head.

Question 17

What direction does the endolymph move in?

Answer 17

The opposite direction of the head. The movement of the endolymph deflects hairs.

Question 18

What are Otolith Organs?

Answer 18

Located between the semicircular canals and the cochlea, made up of calcium carbonate, they deal with gravity (tilting of the head) and forward/backward motion.

Question 19

What is the Vestibular System?

Answer 19

The Semicircular Canals and the Otolith Organs; the system that maintains body balance and allows a sense of the position of the body in relation to gravity.

Question 20

What is hearing?

Answer 20

The detection of very small changes in air pressure (sound waves).

Question 21

What is pitch?

Answer 21

The frequency of pressure change.

Question 22

What does sound vibrate?

Answer 22

Tympanic Membrane (ear drum).

Question 23

What constituents the middle ear?

Answer 23

The stapes, incus, and malleus. Transports the sound from the outer ear to the inner ear.

Question 24

How much does sound energy get amplified in the ear?

Answer 24

24x (sound gets to the oval window).

Question 25

What is the inner ear?

Answer 25

A continuous tube (upper part = vestibular canal, lower part = tympanic canal) filled with perilymph (similar to extracellular fluid)

Question 26

What is the Cochlear duct filled with?

Answer 26

Endolymph. Sound is detected by hair cells in the Cochlea.

Question 27

What does the Basilar membrane contain?

Answer 27

The hair cells involved with sound.

Question 28

What does stretching of the stereocillia open?

Answer 28

Mechanically gated potassium channels. Inward flow of potassium concentration depolarizes receptive potential.

Question 29

How do we differentiate between high pitch and low pitch sound?

Answer 29

The vestibular membrane portion close to the oval window is narrow and stiff, and high pitch sound causes this to vibrate. The other end is very flexible, and low pitch sounds will cause it to vibrate.

Question 30

True or False: All the hair cells in the human cochlea vibrate in response to sound.

Answer 30

False. Depending on the pitch of the sound, only some of the hair will vibrate.

Question 31

Do terrestrial animals or aquatic animals have more efficient amplification mechanisms?

Answer 31

Terrestrial animals because fish do not have an outer or middle ear and therefore a more simple amplification system.