1. The Senses

2. Super Snout In The News

3. Sensory Receptors
Changes environmental stimuli into nerve impulses

4. Generalized Sensory Pathway

5. Impulses are conducted to sensory areas of the cerebral cortex

6. Sensing the Internal Environment
Neurons send messages to homeostasis centers in the brain
Sensor types
Temperature
Carbon dioxide levels
Oxygen levels pH
Stretch
Pain

7. Proprioceptors Position receptors Sense position in space
Within skeletal muscle
Within tendons
In the inner ear
Sense position in space
Example: stretch receptor in muscle

9. Mechanoreceptors Detect touch, movement & pressure
Example: lateral line system

10. Touch Receptors in Human Skin
Merkel’s discs, Meissner’s corpuscles & Pacinian corpuscles

11. Thermoreceptors
Sensitive to temperature change

12. Detecting Infrared Heat is sensed as infrared radiation
Pit organs of some snakes

13. Detecting UV light Insects have receptors to detect UV
UV light transmitted by flowers
Insects are pollinators of flowers
Normal Light
UV Light

14. Electroreceptors Detect electric fields
Found in some fish, salamanders & platypus

15. Detection of Magnetic Fields
Found in variety of migratory animals
Used for orientation to return to certain areas

16. Chemoreception Widespread in animal kingdom
May be found on many parts of the body
Includes senses of taste & smell

17. Taste Receptor = taste buds Detect chemicals in food Primary tastes
Salty
Sweet
Sour
Bitter

18. Taste Buds Within tongue papillae Microvilli extend through taste pore
Nerves attached to receptor cells

19. Smell Olfactory receptors Can distinguish several thousand odors
In nasal epithelium
Can distinguish several thousand odors

20. Photoreception Sensing light
Different organisms sense different wavelengths
Not all eyes are image forming

21. Multifaceted Eyes Each facet sees part of image
Image is summed by brain to form single image

22. Phototaxis Detection of light can change behavior Positive phototaxis
Organism moves toward light
Negative phototaxis
Organism moves away from light

23. Human Eye Camera-like eye also found in cephalopods Single lens
Receptors sensitive to various wavelengths
Light is focused onto receptors

24. Structure of the Human Eye

25. Outer Layer of Eye Sclera Cornea Aqueous humor
Tough connective tissue layer
White region of the eye
Cornea
Transparent front of eye
Allows light to enter
Aqueous humor
Liquid behind cornea
Fills anterior chamber

26. Lens Just behind aqueous humor Suspended by ligaments
Ligaments attached to cilliary muscles
Cilliary muscles are able to change lens shape for focusing

27. Focusing the Eye

28. Iris Lies between cornea & lens Colored part of eye
Controls size of opening
Opening = pupil

29. Choroid Layer Dark brown membrane Lines sclera Contains blood vessels
Nourishes eye

30. Retina Contains sensory receptors Fovea Rods Cones
Low levels of light
Cones
Three types
Stimulated by different wavelengths
Allows for color vision
Fovea
Central area with many cones

31. Structure of the Retina

32. Optic Nerve
Creates blind spot in retina
Carries impulses to brain

33. Depth Perception Possible because of two eyes in different positions
Provides two images summed by brain
Results in three dimensional quality image

34. Sound Type of mechanical energy
Many different types of sound receptors
Some animals hear different wavelengths
Bats use echolocation or animal sonar

35. Human Hearing
Human ear has three parts
Inner ear has sound receptors

36. Outer Ear Pinna External auditory canal Funnels sound waves
Leads to tympanic membrane

37. Tympanic Membrane Eardrum Stretches over middle ear opening
Amplifies & increases vibrations
Transfers vibrations to bones of middle ear

38. Bones of Middle Ear Malleus, Incus & Stapes
Transfer vibrations to opening of Cochlea

39. Eustachian Tube Connects middle ear to nasopharynx
Equalizes air pressure

40. Inner Ear Membrane covers oval window Fluid filled cochlea
Contains organ of Corti
Hair cells are receptors

42. Transmission of Pressure Waves in Inner Ear

43. Sound Perception Different frequencies set up differing wave patterns
Loud sound increases wave magnitude

44. Vestibule & Semicircular Canals
Detect position and movement
Both found in inner ear

45. Vestibule Senses if you are upside down Detects effects of gravity
Includes two areas
Utricle
Saccule
Jelly filled chambers

46. Movement Detection in Vestibule
Otoliths – small pebbles
Movement can cause otoliths to stimulate receptor cells
Brain makes sense of sensory input

48. Semicircular Canals Three fluid filled canals
Canals oriented at right angles
Contain ciliated sensory cells
Jelly like material lies above cells
Movement initiates depolarization
Complex movements analyzed by brain