1. Sensory systems
Chapter 50

2. Five senses
Touch
Taste
Smell
Sound
Vision

3. Sensory systems Sensory info is received
Nerve impulse or action potential
All or nothing response
Response depends on part of brain that receives the info

4. Sensory information Sensory info to CNS 1. Sensory reception
2. Transduction
Graded potential
Ion channels open or close
Receptor potential
Change in membrane potential
Depolarization

5. Sensory information 3. Transmission Goes to CNS via afferent pathway
4. Interpretation
Perception by the brain

6. Sensory receptors Nerve endings
Specialized neurons or epithelial cells
Associated with sensory organs -eyes
All stimuli is a form of energy

7. Sensory receptors Stimuli-outside body
Heat, light, pressure & chemicals
Stimuli-inside body
BP, body position, body temperature

8. Types of sensory receptors
Mechanoreceptors
Pressure, stretch, touch
Chemoreceptors
chemicals
Electromagnetic receptors (photoreceptors)
Nociceptors (pain)
Thermoreceptors

9. Receptors Cutaneous receptors: Skin Heat, cold, pressure, pain & touch
Thermoreceptors
Heat/Cold
Hypothalamus
Regulates temp of blood (core temp)

10. Receptors Mechanoreceptors Touch Close to surface of skin
Hair follicle receptors
Pressure
Deeper

11. Heat Gentle touch Pain Cold Hair Epidermis Dermis Hypodermis Nerve
skin
Heat
Gentle touch
Pain
Cold
Hair
Epidermis
Dermis
Hypodermis
Nerve
Connective tissue
Hair movement
Strong pressure

12. Receptors Nociceptors: Pain Severe temperature change Tissue damage
Free nerve endings (naked dendrites)
Located in the epidermis

13. PAIN

14. Receptors Proprioceptors Give info on animal’s body parts Position
Movement
Stretch receptors on muscle
Prevent over stretch

15. Receptors Baroreceptors:
Detect tension or stretch in blood vessel walls
Internal carotids
Aortic arch
Drop in BP
Stimulation to increase HR & vasoconstriction

16. Receptors Chemoreceptor Aorta & carotid Medulla oblongata
pH (blood & CSF)
Slow breathing
Increased CO2
Lowers pH
Causes an increased respiration rate

17. Taste Taste buds Collections of receptor cells Epithelial cells
Papillae
Raised areas on tongue
Taste buds located

18. Taste Taste buds contain 50-100 taste cells Food dissolves in saliva
Contact taste cells
Taste salty, sweet, sour, bitter

19. Taste Chemoreceptors Salt: Na+1 Sour: H+1 Directly through ion-channel
Sweet: receptor proteins for sugar
Bitter: K+channels are closed by receptor proteins

20. TONGUE

21. Sweet
Sugar molecule
G protein
Sweet receptor
Tongue
Phospholipase C
SENSORY RECEPTOR CELL
Sugar molecule
Taste pore
PIP2
Taste bud
Sensory receptor cells
IP3 (second messenger)
Sodium channel
Sensory neuron
IP3-gated calcium channel
Nucleus ER
Ca2+ (second messenger)
Na+

22. Smell Olfactory receptors Chemoreceptors
Located upper portions of nasal passages
Dendrites are in cilia
Axon goes directly to cerebral cortex
Odorant or odorous substance binds proteins
Second messenger response in receptor cell

23. Smell Opens membrane to Ca & Na Causes impulse (action potential)
Distinguish thousands of odors
Very accurate
Single odorant molecule

24. NOSE

25. Nose Brain Olfactory bulb Odorants Nasal cavity Bone Epithelial cell
Action potentials
Olfactory bulb
Odorants
Nasal cavity
Bone
Epithelial cell
Odorant receptors
Chemo- receptor
Plasma membrane
Cilia
Odorants
Mucus

26. Hearing Outer ear: Pinna, canal Middle ear:
Tympanic membrane (ear drum)
Eustachian tube
Small bones (malleus, incus, stapes)
Inner ear:
Cochlea, auditory nerve

27. EAR

28. Ear

29. Hearing Vibrations move in canal Cause eardrum to move
Vibrations pass through the bones
Stapes pass vibration to inner ear
Causes pressure waves in fluid in cochlea
Basilar membrane of the cochlea vibrates

30. Hearing Hair cells on membrane vibrate
Leads to change in membrane potentials in sensory neurons
Sound interpreted
Humans hear 20-20,000 hertz
Age decreases higher frequencies
Dogs hear sounds at 40,000 hertz

31. Ears Inner ear Body position & balance Two chambers near the cochlea
Utricle & saccule
Filled with fluid
Hair cells in chambers respond to changes in head positions

32. Ears Utricle: horizontal motion Saccule: vertical motion
Different movement causes different sensory neurons to be stimulate
Labyrinth system
Spin around become dizzy

33. Semicircular canals Flow of fluid Vestibular nerve Cupula Hairs
Equilibrium
Semicircular canals
Flow of fluid
Vestibular nerve
Cupula
Hairs
Hair cells
Vestibule
Axons
Utricle
Body movement
Saccule

34. Eye Sclera: White outer layer of connective tissue Conjunctiva:
Epithelial layer
Covers outer surface of sclera
Under surface of the eyelid
Cornea:
Clear part of sclera, light passes through

35. Eye Choroid Pigmented layer under the sclera Iris
Color part of eye formed by the choroid
Pupil
Opening at the center of the iris
Controlled by iris
Lens
Behind the pupil, held in place by ligaments

36. Eye Retina Back of eye where image is focused Optic nerve
Sensory neurons
Vitreous humor
Jellylike substance behind the lens
Aqueous humor
Thinner fluid
Fills smaller chamber in front of the lens

37. EYE

39. Eye Light enters eye through cornea Passes through pupil to lens
Lens focuses images on retina
Photoreceptor cells of retina transduce light energy
Action potentials pass via sensory neurons in the optic nerve

40. Eye Rods & cones Photoreceptors of eyes
Rods: black and white vision in dim light
Cones: high visual acuity & color vision
Located in center of retina

41. EYE

42. Rods/cones
Retina
Choroid
Photoreceptors
Neurons
Retina
Cone
Rod
Light
To brain
Optic nerve
Light
Ganglion cell
Amacrine cell
Horizontal cell
Optic nerve axons
Bipolar cell
Pigmented epithelium

43. Eyes Binocular vision Axons of ganglion cells form optic nerves
Optic nerves meet at the optic chiasm (base of the cerebral cortex)
Visions from the right visual field go to the left side of the brain and vise versa
Thalamus
Cortex

44. Lateral geniculate nucleus
Vision
Right visual field
Optic chiasm
Right eye
Left eye
Left visual field
Optic nerve
Primary visual cortex
Lateral geniculate nucleus

45. Eyes Nearsightedness: longer eyeball Farsightedness: shorter eyeball
Asitgmatism: problems with lens or cornea
Light rays converge unevenly
Colorblindness: inherited lack of one or more types of cones