1. Human Biology Sylvia S. Mader Michael Windelspecht
Chapter 14
Senses
Lecture Outline
Part 1
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2. Senses
See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes 2

3. Points to ponder What are sensory receptors?
How do we detect the sense of taste and smell?
What is the anatomy of the eye?
How do we focus images?
What are some eye abnormalities?
What is the anatomy of the ear?
Which parts function in balance and which parts function in hearing?

4. 14.1 Overview of Sensory Receptors and Sensations
Sensory receptors – dendrites specialized to detect certain types of stimuli
___________: detect stimuli from outside the body (e.g., taste, hearing, vision)
___________: receive stimuli from inside the body (e.g., change in blood pressure)

5. Types of sensory receptors
14.1 Overview of Sensory Receptors and Sensations
Types of sensory receptors
Chemoreceptors – respond to nearby chemicals
_____________ (pain receptors) – chemoreceptors that respond to chemicals released by damaged tissue
_____________ – respond to light energy
Mechanoreceptors – respond to mechanical forces such as pressure
______________ – stimulated by temperature changes

6. Senses and the receptors involved
14.1 Overview of Sensory Receptors and Sensations
Senses and the receptors involved

7. How does sensation occur?
14.1 Overview of Sensory Receptors and Sensations
How does sensation occur?
Sensory receptors respond to environmental stimuli.
Nerve impulses travel to the cerebral cortex and sensation (conscious perception of stimuli) occurs.
____________, decrease in stimulus response, can occur with repetitive stimuli (i.e., odor).

8. How does sensation occur?
14.1 Overview of Sensory Receptors and Sensations
How does sensation occur?
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Peripheral
Nervous System
stimulus
sensory receptor
nerve impulses
along sensory
fiber
spinal cord
brain
Central
Nervous System
Figure The role of the CNS and PNS in sensation and sensory perception. 8

9. Proprioceptors 14.2 Somatic Senses
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muscle spindle 2
muscle fiber 2 1
quadriceps
muscle
bundle of
muscle fibers 3
sensory neuron
to spinal cord
Golgi tendon organ
tendon
Figure The action of a muscle spindle.

10. 14.2 Somatic Senses
Cutaneous receptors
Receptors in the dermis that make the skin sensitive to touch, pressure, pain, and temperature.
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epidermis
free nerve endings
(pain, heat, cold)
Meissner
corpuscles (touch)
Merkel disks (touch)
Pacinian corpuscles
(pressure)
Krause end
bulbs (touch)
Ruffini endings
(pressure)
dermis
root hair
plexus (touch)
Figure Sensory receptors of the skin.

11. 14.3 Senses of Taste and Smell
Taste receptors
4,000 taste buds are located primarily on the tongue of adult humans.
We have 5 main types of taste receptors: sweet, sour, salty, bitter, and umami (savory).
80-90% of what we perceive as taste is actually due to the sense of ______.

12. b (both): © Omikron/SPL/Photo Researchers
14.3 Senses of Taste and Smell
Taste receptors
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tonsils
epiglottis
sensory nerve fiber
supporting cell
taste pore
10 μm
papillae
taste bud
connective tissue
taste cell
microvilli
a. Tongue
b. Papillae
c. Taste bud
b (both): © Omikron/SPL/Photo Researchers
Figure The tongue and the sense of taste. 12

13. 14.3 Senses of Taste and Smell
Smell receptors
Depends on million olfactory cells (modified neurons) in the roof of the nasal cavity
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olfactory bulb
neuron
olfactory tract
frontal lobe of
cerebral hemisphere
olfactory bulb
olfactory epithelium
bone of
skull
nasal cavity
odor
molecules
sensory
nerve fibers
olfactory
epithelium a.
supporting
cell
olfactory
cell
olfactory cilia of
olfactory cell
Figure The sense of smell. b.
odor molecules

14. Anatomy of the eye Made of 3 layers/coats
14.4 Sense of Vision
Anatomy of the eye
Made of 3 layers/coats
______: mostly white and fibrous except the cornea
______: darkly-pigmented vascular layer
______: inner layer containing photoreceptors 14

15. Anatomy of the eye 2 compartments
14.4 Sense of Vision
Anatomy of the eye
2 compartments
Anterior compartment: between the cornea and lens; filled with a clear fluid called _________ humor
Posterior compartment: most of the eye, behind the lens; contains a gelatinous material called ________ humor 15

16. Anatomy of the eye 14.4 Sense of Vision
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sclera
choroid
retina
ciliary body
retinal blood
vessels
lens
iris
optic nerve
pupil
fovea centralis
cornea
posterior compartment
filled with vitreous humor
anterior
compartment
filled with
aqueous humor
retina
suspensory
ligament
choroid
sclera
Figure The structures of the human eye.