1. PowerPoint Lecture Outlines to accompany
Hole’s Human
Anatomy and Physiology
Eleventh Edition
Shier w Butler w Lewis
Chapter 12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Chapter 12 Nervous System III - Senses
General Senses
receptors that are widely distributed throughout the body
skin, various organs and joints
Special Senses
specialized receptors confied to structures in the head
eyes and ears

3. Senses Sensory Receptors
specialized cells or multicellular structures that collect information from the environment
stimulate neurons to send impulses along sensory fibers to the brain
Sensation
a feeling that occurs when brain becomes aware of sensory impulse
Perception
a person’s view of the stimulus; the way the brain interprets the information

4. Pathways From Sensation to Perception (Example of an Apple)

5. Receptor Types Chemoreceptors
respond to changes in chemical concentrations
Pain receptors (Nociceptors)
respond to tissue damage
Thermoreceptors
respond to changes in temperature
Mechanoreceptors
respond to mechanical forces
Photoreceptors
respond to light

6. Sensory Impulses
stimulation of receptor causes local change in its receptor potential
a graded electrical current is generated that reflects intensity of stimulation
if receptor is part of a neuron, the membrane potential may generate an action potential
if receptor is not part of a neuron, the receptor potential must be transferred to a neuron to trigger an action potential
peripheral nerves transmit impulses to CNS where they are analyzed and interpreted in the brain

7. Sensations Projection
process in which the brain projects the sensation back to the apparent source
it allows a person to pinpoint the region of stimulation

8. Sensory Adaptation ability to ignore unimportant stimuli
involves a decreased response to a particular stimulus from the receptors (peripheral adaptations) or along the CNS pathways leading to the cerebral cortex (central adaptation)
sensory impulses become less frequent and may cease
stronger stimulus is required to trigger impulses

9. General Senses
senses associated with skin, muscles, joints, and viscera
three groups
exteroceptive senses – senses associated with body surface; touch, pressure, temperature, pain
visceroceptive senses – senses associated with changes in viscera; blood pressure stretching blood vessels, ingesting a meal
proprioceptive senses – senses associated with changes in muscles and tendons

10. Touch and Pressure Senses
Free nerve endings
common in epithelial tissues
simplest receptors
sense itching
Meissner’s corpuscles
abundant in hairless portions of skin; lips
detect fine touch; distinguish between two points on the skin
Pacinian corpuscles
common in deeper subcutaneous tissues, tendons, and ligaments
detect heavy pressure and vibrations

11. Touch and Pressure Receptors

12. Temperature Senses Warm receptors
sensitive to temperatures above 25oC (77o F)
unresponsive to temperature above 45oC (113oF)
Cold receptors
sensitive to temperature between 10oC (50oF) and 20oC (68oF)
Pain receptors
respond to temperatures below 10oC
respond to temperatures above 45oC

13. Sense of Pain free nerve endings widely distributed
nervous tissue of brain lacks pain receptors
stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature
adapt very little, if at all

14. Visceral Pain pain receptors are the only receptors in viscera whose
stimulation produces sensations
pain receptors respond differently to stimulation
not well localized
may feel as if coming from some other part of the body
known as referred pain

15. Referred Pain
may occur due to sensory impulses from two regions following a common nerve pathway to brain

16. Pain Nerve Pathways Chronic pain fibers Acute pain fibers C fibers
thin, unmyelinated
conduct impulses more slowly
associated with dull, aching pain
difficult to pinpoint
Acute pain fibers
A-delta fibers
thin, myelinated
conduct impulses rapidly
associated with sharp pain
well localized

17. Regulation of Pain Impulses
Thalamus
allows person to be aware of pain
Pain Inhibiting Substances
enkephalins
serotonin
endorphins
Cerebral Cortex
judges intensity of pain
locates source of pain
produces emotional and motor responses to pain

18. Proprioceptors mechanoreceptors
send information to spinal cord and CNS about body position and length and tension of muscles
Main kinds of proprioreceptors
Pacinian corpuscles – in joints
muscle spindles – in skeletal muscles*
Golgi tendon organs – in tendons*
*stretch receptors

19. Stretch Receptors

20. Summary of Receptors of the General Senses

21. Special Senses
sensory receptors are within large, complex sensory organs in the head
smell in olfactory organs
taste in taste buds
hearing and equilibrium in ears
sight in eyes

22. Sense of Smell Olfactory Receptors chemoreceptors
respond to chemicals dissolved in liquids
Olfactory Organs
contain olfactory receptors and supporting epithelial cells
cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

23. Olfactory Receptors

24. Olfactory Nerve Pathways
Once olfactory receptors are stimulated, nerve impulses travel through
olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

25. Olfactory Stimulation
olfactory organs located high in the nasal cavity above the usual pathway of inhaled air
olfactory receptors undergo sensory adaptation rapidly
sense of smell drops by 50% within a second after stimulation
Olfactory Code
hypothesis
odor that is stimulated by a distinct set of receptor cells and its associated receptor proteins

26. Sense of Taste Taste Buds organs of taste
located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx
Taste Receptors
chemoreceptors
taste cells – modified epithelial cells that function as receptors
taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

27. Taste Receptors

28. Taste Sensations Four Primary Taste Sensations
sweet – stimulated by carbohydrates
sour – stimulated by acids
salty – stimulated by salts
bitter – stimulated by many organic compounds
Spicy foods activate pain receptors

29. Taste Nerve Pathways
Sensory impulses from taste receptors travel along
cranial nerves to
medulla oblongata to
thalamus to
gustatory cortex (for interpretation)

30. Hearing
Ear – organ of hearing
Three Sections
External
Middle
Inner

31. External Ear auricle external auditory meatus tympanic membrane
collects sounds waves
external auditory meatus
lined with ceruminous glands
carries sound to tympanic membrane
terminates with tympanic membrane
tympanic membrane
vibrates in response to sound waves

32. Middle Ear tympanic cavity air-filled space in temporal bone
auditory ossicles
vibrate in response to tympanic membrane
malleus, incus, and stapes
oval window
opening in wall of tympanic cavity
stapes vibrates against it to move fluids in inner ear

33. Auditory Tube eustachian tube connects middle ear to throat
helps maintain equal pressure on both sides of tympanic membrane
usually closed by valve-like flaps in throat

34. Inner Ear complex system of labyrinths osseous labyrinth
bony canal in temporal bone
filled with perilymph
membranous labyrinth
tube within osseous labyrinth
filled with endolymph

35. Inner Ear Three Parts of Labyrinths cochlea semicircular canals
functions in hearing
semicircular canals
functions in equilibrium
vestibule

36. Cochlea Scala vestibuli upper compartment
leads from oval window to apex of spiral
part of bony labyrinth
Scala tympani
lower compartment
extends from apex of the cochlea to round window

37. Cochlea Cochlear duct portion of membranous labyrinth in cochlea
Vestibular membrane
separates cochlear duct from scala vestibuli
Basilar membrane
separates cochlear duct from scala tympani

38. Organ of Corti group of hearing receptor cells (hair cells)
on upper surface of basilar membrane
different frequencies of vibration move different parts of basilar membrane
particular sound frequencies cause hairs of receptor cells to bend
nerve impulse generated

39. Organ of Corti

40. Auditory Nerve Pathways

41. Summary of the Generation of Sensory Impulses from the Ear

42. Equilibrium Dynamic Equilibrium Static Equilibrium semicircular canals
sense rotation and movement of head and body
Static Equilibrium
vestibule
sense position of head when body is not moving

43. Vestibule
Utricle
communicates with saccule and membranous portion of semicircular canals
Saccule
communicates with cochlear duct
Mucula
hair cells of utricle and saccule

44. Macula responds to changes in head position
bending of hairs results in generation of nerve impulse

45. Semicircular Canals three canals at right angles ampulla
swelling of membranous labyrinth that communicates with the vestibule
crista ampullaris
sensory organ of ampulla
hair cells and supporting cells
rapid turns of head or body stimulate hair cells

46. Crista Ampullaris

47. Sight Visual Accessory Organs eyelids lacrimal apparatus
extrinsic eye muscles

48. Eyelid palpebra composed of four layers orbicularis oculi - closes
skin
muscle
connective tissue
conjunctiva
orbicularis oculi - closes
levator palperbrae superioris – opens
tarsal glands – secrete oil onto eyelashes
conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball

49. Lacrimal Apparatus lacrimal gland lateral to eye secretes tears
canaliculi
collect tears
lacrimal sac
collects from canaliculi
nasolacrimal duct
collects from lacrimal sac
empties tears into nasal cavity

50. Extrinsic Eye Muscles Superior rectus rotates eye up and medially
Inferior rectus
rotates eye down and medially
Medial rectus
rotates eye medially

51. Extrinsic Eye Muscles Lateral rectus rotates eye laterally
Superior oblique
rotates eye down and laterally
Inferior oblique
rotates eye up and laterally

52. Structure of the Eye hollow spherical wall has 3 layers
outer fibrous tunic
middle vascular tunic
inner nervous tunic

53. Outer Tunic Cornea anterior portion transparent light transmission
light refraction
Sclera
posterior portion
opaque
protection

54. Middle Tunic Iris anterior portion pigmented controls light intensity
Ciliary body
anterior portion
pigmented
holds lens
moves lens for focusing
Choroid coat
provides blood supply
pigments absorb extra light

55. Anterior Portion of Eye
filled with aqueous humor

56. Lens transparent biconvex lies behind iris
largely composed of lens fibers
elastic
held in place by suspensory ligaments of ciliary body

57. Ciliary Body forms internal ring around front of eye
ciliary processes – radiating folds
ciliary muscles – contract and relax to move lens

58. Accommodation
changing of lens shape to view objects

59. Iris composed of connective tissue and smooth muscle
pupil is hole in iris
dim light stimulates radial muscles and pupil dilates
bright light stimulates circular muscles and pupil constricts

60. Aqueous Humor fluid in anterior cavity of eye
secreted by epithelium on inner surface of the ciliary body
provides nutrients
maintains shape of anterior portion of eye
leaves cavity through canal of Schlemm

61. Inner Tunic retina contains visual receptors
continuous with optic nerve
ends just behind margin of the ciliary body
composed of several layers
macula lutea – yellowish spot in retina
fovea centralis – center of macula lutea; produces sharpest vision
optic disc – blind spot; contains no visual receptors
vitreous humor – thick gel that holds retina flat against choroid coat

62. Posterior Cavity
contains vitreous humor – thick gel that holds retina flat against choroid coat

63. Major Groups of Retinal Neurons
receptor cells, bipolar cells, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve
horizontal cells and amacrine cells – modify impulses

64. Layers of the Eye

65. Light Refraction Refraction bending of light
occurs when light waves pass at an oblique angle into mediums of different densities

66. Types of Lenses Convex lenses cause light waves to converge
Concave lenses cause
light waves to diverge

67. Focusing On Retina as light enters eye, it is refracted by
convex surface of cornea
convex surface of lens
image focused on retina is upside down and reversed from left to right

68. Visual Receptors Rods long, thin projections
contain light sensitive pigment called rhodopsin
hundred times more sensitive to light than cones
provide vision in dim light
produce colorless vision
produce outlines of objects
Cones
short, blunt projections
contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe
provide vision in bright light
produce sharp images
produce color vision

69. Rods and Cones

70. Visual Pigments Rhodopsin light-sensitive pigment in rods
decomposes in presence of light
triggers a complex series of reactions that initiate nerve impulses
impulses travel along optic nerve
Pigments on Cones
each set contains different light-sensitive pigment
each set is sensitive to different wavelengths
color perceived depends on which sets of cones are stimulated
erythrolabe – responds to red
chlorolabe – responds to green
cyanolabe – responds to blue

71. Rod Cells

72. Stereoscopic Vision provides perception of distance and depth
results from formation of two slightly different retinal images

73. Visual Nerve Pathway

74. Life-Span Changes Age related hearing loss due to
damage of hair cells in organ of Corti
degeneration of nerve pathways to the brain
tinnitus
Age-related visual problems include
dry eyes
floaters (crystals in vitreous humor)
loss of elasticity of lens
glaucoma
cataracts
macular degeneration

75. Clinical Application Refraction Disorders
concave lens corrects nearsightedness
convex lens corrects farsightedness