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Senses
Senses
 Perceive environment
 Find food
 Avoid predators
 Avoid danger
 Find shelter
 Interact socially
Sensory Receptors
 Mechanoreceptors
 Touch, hearing, equilibrium, pressure
 Thermoreceptors
 Radiant energy, infrared
 Nociceptors
 Pain
 Chemoreceptors
 Smell, taste
 Osmoreceptors
 Water, solute concentration
 Photoreceptors
 Light, vision
Sensory Receptors
 Sensory receptor
 Nerve pathway
 Brain integration
 Sensory perception
Sensory Receptors
 Receptors specific for given stimulus
 Strong stimulation
 Greater frequency of action potentials
 Greater number of neurons
 Sensory adaptaion
 Frequency of AP decrease or stop w/ constant simulus
Somatic
 Start at sensory
neurons
 Different sensors to
different part of brain
 Somatosensory cortex
Somatic
 Body surface
 Free nerve endings
 Meissner corpuscles
 Pacinian corpuscles
 Thermoreceptors


Bulb of Krause
Ruffini endings
Somatic
 Muscles
 Mechanorecptors



Motion
Position in space
Stretch
Somatic
 Pain—perception of injury
 Nociceptors
 Somatic—skin, skeletal muscle, joints, tendons
 Visceral—internal organs


Fewer nocieptors
“Referred” pain
 Cell damage releases bradykinins
 Bradykinins stimulate nearby nociceptors
 Stimulus perceived by brain as pain
Olfaction
 Smell
 Social communication
 Find mates
 Find prey
 Avoid predators
Olfaction
 Well-developed in most
mammals
 Especially carnivores &
ungulates
 Non-existent in cetaceans
(whales, dolphins, etc.)
 Canines 100,000-1 million
times better than humans

Bloodhounds 10-100 million
times
Olfaction
 Poorly developed in
most birds
 Well-developed in fish
 Salmon—ID and return
to home streams
 Catfish—ID others,
maintain social order
Olfaction
 Chemicals inhaled
 Must be dissolved in liquid
(mucus)
 Binds to membrane proteins
 Triggers depolarization of
neurons
 Different combinations of
receptor activation recognized
as patterns by brain
Olfaction
Olfaction
 Pheromones
 Air-borne chemical that triggers behavioral response in
same species
 Alarm
 Food trail
 Sex
 Territorial
Taste
 Differentiate nutrition vs.
noxious
 Receptors on various organs
 Antennae
 Tentacles
 Tongue
 Legs
Taste
 Five tastes in humans
 Sweet
 Sour
 Salty
 Bitter
 Umami
Chemoreceptors
 Antennae
 Most arthropods
 Multiple functions


Smell & taste most important
Also touch, air motion, vibration,
heat
 Olfactory receptors bind to odor
molecules
 Sends signal to antennal lobe in
brain
Chemoreceptors
 Vomeronasal organ
 Many animals (including
humans)
 Certain smells
 Many pheromones
 May be involved in triggering
some aggression & mating
Chemoreceptors
 Vomeronasal organ
 Flehmen response
 In cat
 In deer
Hearing
 Detect vibrations
 Interpret as sound
 Amplitude (loudness)
 Frequency (pitch)
 Important for communication
 Important for finding prey
 Important for avoiding predators
Hearing
 Sonic—human frequencies
 15 Hz-20,000 Hz
 Best at 2,000-4,000 Hz
 Ultrasonic—above human frequencies
 Bats, dogs
 Subsonic—below human frequencies
 Snakes (sense through bellies)
 Whales, giraffes, elephants (communication)
Hearing
 External ear (pinna)
 Collects sound
 Middle ear
 Ossicles



Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
 Receive vibrations from
tympanum (eardrum)
 Transmit to inner ear
 Inner ear
 Cochlea—auditory nerves
 Semicircular canals—balance
Hearing
 ,,,
Hearing
 Vibrations coming down ear vibrate ossicles
 Stapes vibration pushes on oval membrane on cochlea
 Fluid in cochlea moves at specific frequency
 Fluid wave moves tectorial membrane
 Movement of tectorial membrane stimulates nerve
impulse
Hearing
 ,,,
Hearing
 Equilibrium
 Vestibular organs
(semicircular canals)
 Static equilibrium


Linear movement of head
Otolithic membrane
movement triggers hairs
 Dynamic equilibrium


Rotation, acceleration,
deceleration
Fluid bends hairs in crista
ampullaris
Hearing
 Echolocation
 Dolphis, shrews, bats, most
whales
 Active sonar
 Sounds sent out
 Hear reflection of sounds
(echo)
 Able to triangulate sounds
“Hearing”
 Lateral line
 Detect vibrations in water
 Along sides of many fish
 Similar to certain aspects of hearing &
equilibrium
Vision
 Photoreceptors
 Part of brain that can interpret
pattern of nerve impulses
 Pigment molecules absorb
incoming photons
 Convert photons into action
potential
Vision
 Invertebrate
 Simple




Photosensitive receptors
Do not form images
Light & dark
Ocellus
Vision
 Invertebrate
 Compound







Arthropods
Multiple facets
Each has own lens & photoreceptor
cells
Very sensitive to motion
360o field of vision
Multiple images integrated in brain
Poor image resolution
Vision
 Invertebrate
 Mollusks



Many have lens eyes (similar to
vertebrates)
Cephalopods have most developed
Hunters, 3 dimensions, often move
fast
Vision
 Vertebrate
 Outer layer


Sclera
Cornea
 Middle Layer
 Lens
 Iris
 Pupil
 Choroid
 Aqueous Humor
 Vitreous Humor
Vision
 Inner layer
 Retina


Macula lutea
Optic disc
 Tapetum Lucidum
Vision
 Rods
 Low light
 Night vision
 No color
 Cones
 Bright light
 Day vision
 Color
Vision
 Accommodation—the process by which an eye
changes to keep an object in focus as it moves closer or
further away.
 Fish, reptiles—Lens moves forwards & backwards in
eye
 Birds, mammals—ciliary muscles change shape of
lens.
Vision
 Photons enter through cornea
 Are focused by lens
 Absorbed by cells in retina
 Photon activity stimulates
receptors to generate action
potential
Vision
 Eye placement
 Forward-facing


Predators
Depth perception
 Side-facing


Prey
Wide field of vision
Other Senses
 Electroception
 Detect electrical fields
 Sharks, skates, rays
 Lungfish, coelacanths, sturgeons
 Monotremes (especially platypus)
 Active—generate own field


Electric eels & fish
Communication
 Passive—sense other fields

Chondrichthyes
Other Senses
 Magnetoception
 Mostly birds

Very important to migration
 Some bees
 Detect magnetic fields
 Magnetite
 Found in many rocks & minerals
 Source of iron ore
 Identified in brains of birds, bees, and humans
 When magnetite aligns w/ Earth’s
magnetic field, stimulates nerve impulse
 Poorly understood sense