Vertebrates 18 - Receptors Flashcards
Merkel disks
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)
Meissner’s corpuscles
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)
Free nerve endings
Pain, touch, itching; they can wrap around vibrissae (sensitive!)
Pacinian corpuscles
Deep in skin for pressure (harder touch), vibrations. Rapid adapting. Layers of membrane around them. Elephants have lots in the trunk and toes.
Elephants
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)
Lateral line receptors
In fish, larval amphibians, not amniotes. Used in schooling, navigation. Have neuromast cells along the body, support cells.
Neuromast organ
Have sensory hair cells which respond to pressure (water pressure). Covered in cupula (gelatin bulb) which contains the kinocilia (tall) and sterocilia (short) “hairs”.
Hair cells
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.
Schooling behaviour
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
Vertebrate outer ear
Pinna (outside shape), auditory canal, tympanum. Pinna funnels in sound, in some animals can be moved (directionality).
Vertebrate middle ear
Air-filled cavity (eustachian tube). Malleus, incus and stapes. Stapes causes oval window to vibrate
Role of eustachian tube
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.
Where did the middle ear bones come from?
Malleus was articular bone, incus was quadrate, and stapes came from a bone in skull.
Vertebrate inner ear
Semicircular canals, and cochlea (in mammals), to auditory nerve
Lizard, amphibians, bird ear
No real outer ear, the disk is the tympanum (birds have very shallow canal). No pinna
Columella
Connects from tympanum to the inner ear in lizards, amphibians, birds. Analogous to the stapes in mammals
Sound in water
Travels faster and with more power. Fish are about same density as water so sound travels to swim bladder easily.
Fish hearing
Inner ear receives the sound “directly”. Osteichthyes have weberian apparatus and have better hearing.
Weberian apparatus
Amplifies sound. Air in swim bladder vibrates in response to sound, causes bones to vibrate and connect to inner ear. Hearing is better
Cochlea
Has the organ of corti. Made of several cells and tissues. Basilar membrane and tectorial membrane with receptors between. Filled with endolymphatic fluid.
Basilar membrane and Range of frequency
Thinner and stiffer at proximal end, so highest frequency (16kHz) at the proximal end. More loose so lowest frequency (500Hz) vibrates at distal end
Different ranges across vertebrates
Mammals have larger range (cochlea is long). Bats and porpoises are very high for echolocation. Blue whale can hear 10Hz, long distance communication.
Utriculus and sacculus
For equilibrium. Part of inner ear. Filled with endolymphatic fluid
Sacculus
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.
Utriculus
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.
Reading: aging and hair cells
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.
Reading: Precautions for studying hair cells
Hair cells are sensitive to vibrations in a building. Basement pool filled with concrete and table on a cushion of air (pneumatic pistons).
Reading: how does hair cell work?
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.
Electroreceptors
In only some fish, sharks, monotremes. Like a 6th sense.
Ampulla of Lorenzini
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.
Ampulla in dogfish and great whites
Great whites out in open water. Dogfish generally on bottom. More important in the dogfish
Passive electroreception
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)
Active electroreception
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.
Thermoreceptors
All vertebrates have cutaneous temp receptors and in hypothalamus. Also nasal folds of vampires and pits in snakes
