Vertebrates 18 - Receptors

Question 1

Merkel disks

Answer 1

Skin surface, slow adapting ie they stay active as long as stimulus is there (light touch, grip). Found in bottom of feet and hands, lips of fish (for pressure)

Question 2

Meissner’s corpuscles

Answer 2

Skin surface, rapid adapting ie shut off when stimulus isn’t changing (texture). Found in bottom of feet and hands, lips of fish (for pressure)

Question 3

Free nerve endings

Answer 3

Pain, touch, itching; they can wrap around vibrissae (sensitive!)

Question 4

Pacinian corpuscles

Answer 4

Deep in skin for pressure (harder touch), vibrations. Rapid adapting. Layers of membrane around them. Elephants have lots in the trunk and toes.

Question 5

Elephants

Answer 5

Elephants have lots of Pacinian corpuscles in the trunk and toes, so very sensitive to vibrations; Possible use in communicating/knowing of presence of other elephants in area (far away)

Question 6

Lateral line receptors

Answer 6

In fish, larval amphibians, not amniotes. Used in schooling, navigation. Have neuromast cells along the body, support cells.

Question 7

Neuromast organ

Answer 7

Have sensory hair cells which respond to pressure (water pressure). Covered in cupula (gelatin bulb) which contains the kinocilia (tall) and sterocilia (short) “hairs”.

Question 8

Hair cells

Answer 8

Tonic receptors (always sending signal). Output by cilia movement (stretch ion channels). More/less NT released so more/less depolarizations depending on direction of bending.

Question 9

Schooling behaviour

Answer 9

Hangout close together. Protection from predation: look huge, hard to see individual fish. Hard to swim close together and bumping together would remove mucous layer (bad). Facilitated by lateral line

Question 10

Vertebrate outer ear

Answer 10

Pinna (outside shape), auditory canal, tympanum. Pinna funnels in sound, in some animals can be moved (directionality).

Question 11

Vertebrate middle ear

Answer 11

Air-filled cavity (eustachian tube). Malleus, incus and stapes. Stapes causes oval window to vibrate

Question 12

Role of eustachian tube

Answer 12

Connects to the pharynx, used to balance pressure which helps tympanum vibrating. Can get blocked by mucous or infection which prevents tympanum from vibrating, can even rupture.

Question 13

Where did the middle ear bones come from?

Answer 13

Malleus was articular bone, incus was quadrate, and stapes came from a bone in skull.

Question 14

Vertebrate inner ear

Answer 14

Semicircular canals, and cochlea (in mammals), to auditory nerve

Question 15

Lizard, amphibians, bird ear

Answer 15

No real outer ear, the disk is the tympanum (birds have very shallow canal). No pinna

Question 16

Columella

Answer 16

Connects from tympanum to the inner ear in lizards, amphibians, birds. Analogous to the stapes in mammals

Question 17

Sound in water

Answer 17

Travels faster and with more power. Fish are about same density as water so sound travels to swim bladder easily.

Question 18

Fish hearing

Answer 18

Inner ear receives the sound “directly”. Osteichthyes have weberian apparatus and have better hearing.

Question 19

Weberian apparatus

Answer 19

Amplifies sound. Air in swim bladder vibrates in response to sound, causes bones to vibrate and connect to inner ear. Hearing is better

Question 20

Cochlea

Answer 20

Has the organ of corti. Made of several cells and tissues. Basilar membrane and tectorial membrane with receptors between. Filled with endolymphatic fluid.

Question 21

Basilar membrane and Range of frequency

Answer 21

Thinner and stiffer at proximal end, so highest frequency (16kHz) at the proximal end. More loose so lowest frequency (500Hz) vibrates at distal end

Question 22

Different ranges across vertebrates

Answer 22

Mammals have larger range (cochlea is long). Bats and porpoises are very high for echolocation. Blue whale can hear 10Hz, long distance communication.

Question 23

Utriculus and sacculus

Answer 23

For equilibrium. Part of inner ear. Filled with endolymphatic fluid

Question 24

Sacculus

Answer 24

For static equilibrium, for orientation to reference to gravity. Contain otoliths (CaCO3) which are on gelatinous material above hair cells. Get stimulated based on movement.

Question 25

Utriculus

Answer 25

For dynamic equilibrium. Attached to 3 perpendicular semi-circular canals (x, y, z). Help determine where you are going, how fast. Helps orient in 3D space. Fluid pushes against the cupula which activates the hair cells.

Question 26

Reading: aging and hair cells

Answer 26

Outer and inner hair cells in basilar membrane. Cilia on air cells can be damaged by frequency and by amplitude (loudness) of sound. They also die naturally and are not replaced.

Question 27

Reading: Precautions for studying hair cells

Answer 27

Hair cells are sensitive to vibrations in a building. Basement pool filled with concrete and table on a cushion of air (pneumatic pistons).

Question 28

Reading: how does hair cell work?

Answer 28

Tonic, always sending impulse. Cilia move in response to membranes moving in the fluid. Turn them on and off (i.e. 16kHz) in response to vibration. Most sensitive receptor ever.

Question 29

Electroreceptors

Answer 29

In only some fish, sharks, monotremes. Like a 6th sense.

Question 30

Ampulla of Lorenzini

Answer 30

Most common electroreceptor. Canals with mucous/jelly that conducts electricity (salts), electrosensory cells at end and depolarizes with stimulus. Mostly found in head and in lateral line.

Question 31

Ampulla in dogfish and great whites

Answer 31

Great whites out in open water. Dogfish generally on bottom. More important in the dogfish

Question 32

Passive electroreception

Answer 32

Dogfish put in tank to locate fish buried in sand, no problem. Put fish in insulated box, can’t find it. Put pieces of fish on surface and buried electrical rod, shark went for rod. Electroreception more important than smell. Generally only for living things (except in tank)

Question 33

Active electroreception

Answer 33

In elephantfish and knifefish. Electroreceptors all over, and has electric organ which produce electricity (like eels). Creates electric field around body and detects any object that comes close. Navigate, hunt and communicate.

Question 34

Thermoreceptors

Answer 34

All vertebrates have cutaneous temp receptors and in hypothalamus. Also nasal folds of vampires and pits in snakes