Sensory Receptors Flashcards
Folded membranes increase the following
– Surface area
– Amount of membrane with photopigment
– Light trapping efficiency
– Light sensitivity
Rhodopsin
- 2 major components
– Opsin – lipoprotein
– does not absorblight
– Retinal – form of vitamin A – absorbs light - Changes shape when it absorbs a photon
- Light activates
Dark Current
- In dark, Na+
channels open,
maintain -30mV
resting potential - Light
Hyperpolarizes
– ↓cGMP- close
channel
– Hyperpolarization
is the signal
Visual Pigments
- Dark Current – in
dark Na+ channels
open, maintain -40
resting potential
– Glutamate released - Light Hyperpolarizes
– ↓ Glutamate
release
– The
hyperpolarization is
the signa
Mechanoreception
- Mechanical distortion of the plasma membrane
opens ion channels
– Pressure (“touch”)
– Equilibrium
– Audition
Pacinian Corpuscle
- Layers of connective tissue
- Sends signal at onset and offset of stimulus
Note study stretch receptors
Insect Bristles
- Directionality
- Endolymph – K + higher outside cells
- Bending opens the K+ channels
Hair Cells (Audition and Balance)
- Cilia distributed over part of cell surface
- Fluid filled canals; direct water contact
- Lack axons; synaptic transmission
Lateral Line System
feels disturbance vinrations which can detect prey
Vertebrate Ear
- Specialization of the lateral line system
- Equilibrium
- Audition
higher frequency fade quicker, lower frequency fade slower
External and Middle Ear
- Collect and Funnel Sound
- Transmit airborne vibrations to fluid filled inner ear
- Tympanic Membrane
- Auditory Ossicles
– Malleus, Incus, Stapes - Oval Window
- Amplification
– 20:1 reduction in size from eardrum to oval
window
– Bones cause 3:2 reduction in movement
– RESULT: 22-fold force ↑ at Oval Window
Inner Ear
- Converts fluid vibrations
into nerve impulses - Cochlea (Mammals,
birds, crocodilians)
– Series of fluid filled
tubes
* Scala tympani and S.vestibuli (form U-shaped
tube)
* Scala media – filledwith endolymph - Basilar Membrane
- Organ of Corti
- Tectorial Membrane
Mechanics of Cochlear Excitation
- Sensitive to frequency and intensity
– Long stereocilia more sensitive to low freq. - K+ and Ca2+ channels open
– NOTE depolarizing action; endolymph
Chemoreception
- Contact chemoreceptors for gathering
info about the chemical environment
– General chemical sensors
– Internal chemoreceptors
– Contact chemoreceptors
– Distance chemoreceptors (olfactory)
Sensilla
- Invertebrate sensilla contain dendrites
sensitive to different chemicals
– Water
– Salt
– Sugar - AP arises in
dendrite
Taste Buds
- Terrestrial Vertebrates – group taste receptors
internally - Support Cells
- Basal Cells –
reg. replacement - No axon
- Depolarize adjacent afferent
neuron
Ionotropic
– Sour – direct flow
– Salt – direct flow
(fast)
Metabotropic
– Sweet – second
messenger (slow)
– Bitter – second
messenger
– Umami- second
messenger
Special Senses - Olfaction
- Smell Receptors – chemoreceptors for
gathering info from a distant chem. environment - Support Cells
- Primary afferent axon
- Secondary Mess.
- Sense many classes of odorants
Vertebrate Olfaction
- Olfactory Bulb
- Vomeronasal Organ-picks up signal, infront of mouth
examples
Chimps ad humans have small olfactory, while rat and tarsier have big olfactory.
Humans have most senses in tongue and fingers.
Starnosed mole-22 pink tentacles covered with eimer’s orans (has 25,000) record eater of 120 ms from touch to consume (227 ms avg), speed of decision.
