1. What are receptor neurons?
Specialized neurons that respond to physical or chemical stimuli
Respond by changing ion channels, altering graded potentials

2. Afferent neuron
High graded potential at receptor ending causes rapid firing of its afferent neuron.

3. Fig. 6-1, p. 142

4. Where sensations get received

5. Nociceptors
Mechanical receptors respond to mechanical damage fast pain pathway
Thermal receptors respond to temperature extremes fast pain pathway
Polymodal nociceptors respond to damaging stimuli slow pain pathway

6. Pain perception and analgesia pathways
Pain pathways
Pain perception and analgesia pathways
Substance P
is neurotransmitter
here

7. How does the body react to pain to reduce sensation?
Your brain can influence its own perception of pain Endogenous opiates: Enkephalin Endorphin

8. Analgesic pathway Substance P blocked
Descending
analgesia
signal
Opiate
receptor
Transmission
of pain
reduced
OUCH!
Enkephalin, Endorphin released
Nociceptor
Afferent pain axon
Substance P blocked
Morphine, oxycodone, codeine and heroin can bind to opiate receptors

9. How might acupuncture work?
Several hypotheses, including:
AP helps release of endorphins, inhibiting pain (previous slide)
AP increases local blood flow, promotes healing
AP stimulates non-pain pathways that inhibit pain pathways

10. Phantom limb pain Brain plasticity in response to loss of limb
Touch face of hand amputee, report hand touched
Brain wrongly ‘remaps’ the area

11. Interesting therapy!

12. External eye anatomy Iris Pupil Cornea Sclera contains smooth muscle
cells specialized
to admit light
Sclera
supports eye

13. choroid
nourishes retina
retina contains
photoreceptors
Ciliary
muscles
change lens
shape

14. Focusing on the retina

15. Lens refracts light to focus images to back
of retina

16. Light rays reflecting from distant vs. near objects

17. Focusing distant and near objects
light
source
Focal point
Parallel rays

18. Focusing distant and near objects
Stronger lens
Near
light
source
Focal point

19. Ciliary muscle
Lens
Ligaments
Ligaments

20. Accommodation - change in the strength of the lens
Sympathetic
stimulation
Contracted
ciliary
muscle
Relaxed
ciliary
muscle
Rounded,
strong lens
Flattened,
weak lens
Tight
ligaments
Slackened
ligaments

21. Presbyopia Myopia (near-sightedness)

22. R e t i n a Light Photoreceptors Ganglion cells Fibers of the optic
Direction of light
Pigment layer
Direction of retinal visual processing
Choroid layer
Sclera
R e t i n a
Light
Photoreceptors
Front of
retina
Ganglion
cells
Fibers of
the optic
nerve

23. Rods - sense grayscale images, function in low light better than cones Cones - red, blue, green wavelengths, better acuity than rods

24. Resolving the problem of the backwards retina
Along the retina is a ‘dimple’ (macula) with a fovea at its base where neurons that lie above photoreceptors are off to the side.
Fovea has primarily cones

25. Phototransduction: light stimuli into neural signals.
Photopigment “rhodopsin” (in rods).
When a photon of light hits rhodopsin, it changes shape and sodium channels close.

26. Colorblindness
If one of the three types of cone pigments is abnormal or missing, colorblindness results.
Genes for green and red pigments are on the X chromosome.

27. Cochlea ear canal Eustachian tube (eardrum) External Ear Tympanic
membrane
(eardrum)
Oval window
External
Ear
Ear
bones
Cochlea
ear canal
Eustachian
tube
External
ear
Middle
ear
Inner
ear

28. What is sound?
alternating regions of high and low pressure

29. “Ear drum” and ear bones convert air vibrations
into movement of liquid in cochlea

30. Movement of last earbone
is transferred to cochlea
at “oval window”

31. Amplification of sound waves

32. Vibrations travel up one cochlea channel and back another
Stapes
Oval
window
Cochlea
Perilymph
Tympanic
membrane
Perilymph
cross
section
Vibrations
released
Round
window

33. Organ of Corti
Tectorial membrane
Auditory
nerve
Basilar
membrane

35. Sensations of different sound frequencies are
detected at different areas of the cochlea
Width & stiffness of basilar membrane changes

36. Wide, flexible end
of basilar membrane
near ‘tip’
Narrow, stiff end
of basilar membrane
near the base

37. Conductive deafness - sound not conducted through middle ear
Conductive deafness - sound not conducted through middle ear. Helped w/hearing aids
Sensorineural deafness - Defect in neural signal.

38. Endolymph
Semicircular
canals
Vestibular
apparatus
Ampulla
nerves

40. Information from hair cells includes the direction of deflection
Kinocilium
Stereocilia
Hair cell
increases potential hyperpolarizes

41. Detecting rotation (angular motion)

42. hair cell
otoliths in membrane
utriclus

43. Detecting linear motion
Within the vestibular apparatus are hair cells which sense movement of otoliths
mineral particles

45. Why alcohol can make the room spin
Alcohol diffuses from blood into endolymph, and endolymph swirls.
Inner ear passes info. to eye muscles, causing eyes to twitch to right (reverses once liver removes alcohol from blood)

46. Gustation and Olfaction
Both utilize chemoreceptors
that bind w/ dissolved
molecules

47. Tasting
Taste buds – contain about receptors in small groups at a taste pore Receptors have cilia that extend into pore
Papilla

48. Variety of taste receptors

49. Pain receptors at taste buds
There are nociceptors along tongue, sensitive to acid, ethanol, capsaicin (in spicy foods)

50. Olfactory epithelium Olfactory receptors Cilia Brain Olfactory bulb
To limbic system
and cerebral cortex
Olfactory receptors
Cilia

51. Cilia Olfactory bulb Afferent nerve fibers (olfactory nerve) Olfactory
mucosa
Receptors
Cilia
Mucus

52. How smell works
Any ‘smell’ is a combination of numerous odorant molecules of specific types
Each of these odorant molecules can possibly bind with one of a few different receptors, most receptors cannot bind
The pattern of binding of odorants to those few receptors types = perception of a smell

53. Vomernasal organ - separate area of olfaction low in nasal cavity
Vomernasal organ - separate area of olfaction low in nasal cavity. Senses pheromones

54. Autonomic Nervous System
The motor system for homeostasis, involuntary responses of visceral organs
Impulses to the viscera, glands, blood vessels, smooth and cardiac muscles

55. ANS pathways
ANS impulses travel from the CNS and pass through 2 neurons to reach an effector.

56. Sympathetic vs. Parasympathetic systems
Sympathetic - “Fight or Flight” ( heart rate, digestion, breathing rate, glycogen glucose, dilate pupil...) Parasympathetic - “Rest and Digest” ( heart rate, digestion, ...etc.

57. Sympathetic vs. Parasympathetic systems
SNS fibers originate from the thoracic and lumbar regions of the spinal cord.
Preganglionic fibers are short Postganglionic fibers are long

58. With sympathetic system activation, the adrenal medulla releases epinephrine and norepinephrine into blood

59. Sympathetic vs. Parasympathetic systems
PNS fibers originate from the cranial and sacral regions of the CNS.
Preganglionic fibers are long Postganglionic fibers are short

60. Sympathetic vs. Parasympathetic systems
Two neurotransmitters are utilized in ANS:
Acetylcholine and norepinephrine
ACh - at autonomic ganglion for both systems
At effectors:
ACh - parasympathetic
Nor - sympathetic

61. Cholinergic vs. Adrenergic fibers
Cholinergic fibers release Ach
Adrenergic fibers release norepinephrine