2. Chapter 35
Senses

3. Senses Perceive environment Find food Avoid predators Avoid danger
Find shelter
Interact socially

4. Sensory Receptors Mechanoreceptors Thermoreceptors Nociceptors
Touch, hearing, equilibrium, pressure
Thermoreceptors
Radiant energy, infrared
Nociceptors
Pain
Chemoreceptors
Smell, taste
Osmoreceptors
Water, solute concentration
Photoreceptors
Light, vision

5. Sensory Receptors Sensory receptor Nerve pathway Brain integration
Sensory perception

6. 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

7. Somatic Start at sensory neurons
Different sensors to different part of brain
Somatosensory cortex

8. Somatic Body surface Free nerve endings Meissner corpuscles
Pacinian corpuscles
Thermoreceptors
Bulb of Krause
Ruffini endings

9. Somatic
Muscles
Mechanorecptors
Motion
Position in space
Stretch

10. 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

11. Olfaction Smell Social communication Find mates Find prey
Avoid predators

12. 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 million times

13. Olfaction Poorly developed in most birds Well-developed in fish
Salmon—ID and return to home streams
Catfish—ID others, maintain social order

14. 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

15. Olfaction

16. Olfaction
Pheromones
Air-borne chemical that triggers behavioral response in same species
Alarm
Food trail
Sex
Territorial

17. Taste Differentiate nutrition vs. noxious Receptors on various organs
Antennae
Tentacles
Tongue
Legs

18. Taste
Five tastes in humans
Sweet
Sour
Salty
Bitter
Umami

19. 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

20. Chemoreceptors Vomeronasal organ Many animals (including humans)
Certain smells
Many pheromones
May be involved in triggering some aggression & mating

21. Chemoreceptors
Vomeronasal organ
Flehmen response
In cat
In deer

22. Hearing Detect vibrations Interpret as sound Amplitude (loudness)
Frequency (pitch)
Important for communication
Important for finding prey
Important for avoiding predators

23. Hearing Sonic—human frequencies Ultrasonic—above 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)

24. Hearing External ear (pinna) Middle ear Inner ear Collects sound
Ossicles
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Receive vibrations from tympanum (eardrum)
Transmit to inner ear
Inner ear
Cochlea—auditory nerves
Semicircular canals—balance

25. Hearing
,,,

26. 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

27. Hearing
,,,

28. 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

29. Hearing Echolocation Dolphis, shrews, bats, most whales Active sonar
Sounds sent out
Hear reflection of sounds (echo)
Able to triangulate sounds

30. “Hearing” Lateral line Detect vibrations in water
Along sides of many fish
Similar to certain aspects of hearing & equilibrium

31. Vision Photoreceptors
Part of brain that can interpret pattern of nerve impulses
Pigment molecules absorb incoming photons
Convert photons into action potential

32. Vision Invertebrate Simple Photosensitive receptors Do not form images
Light & dark
Ocellus

33. 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

34. Vision Invertebrate Mollusks
Many have lens eyes (similar to vertebrates)
Cephalopods have most developed
Hunters, 3 dimensions, often move fast

35. Vision Vertebrate Outer layer Middle Layer Sclera Cornea Lens Iris
Pupil
Choroid
Aqueous Humor
Vitreous Humor

36. Vision
Inner layer
Retina
Macula lutea
Optic disc
Tapetum Lucidum

37. Vision Rods Cones Low light Night vision No color Bright light
Day vision
Color

38. 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.

39. Vision Photons enter through cornea Are focused by lens
Absorbed by cells in retina
Photon activity stimulates receptors to generate action potential

40. Vision Eye placement Forward-facing Side-facing Predators
Depth perception
Side-facing
Prey
Wide field of vision

41. 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

42. Other Senses Magnetoception Mostly birds Some bees
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