Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 14
Senses
Lecture Outline
Part 1
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Senses
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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?
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14.1 Overview of Sensory Receptors and Sensations
Sensory receptors
• 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)
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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
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14.1 Overview of Sensory Receptors and Sensations
Senses and the receptors involved
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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).
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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 14.1 The role of the CNS and PNS in sensation and sensory perception.
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14.2 Somatic Senses
Proprioceptors
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muscle spindle
2
muscle fiber
2
1
quadriceps
muscle
3
bundle of
muscle fibers
sensory neuron
to spinal cord
Golgi tendon organ
tendon
Figure 14.2 The action of a muscle spindle.
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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 14.3 Sensory receptors of the skin.
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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 ______.
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14.3 Senses of Taste and Smell
Taste receptors
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
tonsils epiglottis
sensory nerve fiber supporting cell taste pore
10 μm
papillae
taste bud
connective tissue
a. Tongue
b. Papillae
taste cell
microvilli
c. Taste bud
b (both): © Omikron/SPL/Photo Researchers
Figure 14.4 The tongue and the sense of taste.
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14.4 Sense of Vision
Anatomy of the eye
• Made of 3 layers/coats
1. ______: mostly white and fibrous except the
cornea
2. ______: darkly-pigmented vascular layer
3. ______: inner layer containing
photoreceptors
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14.4 Sense of Vision
Anatomy of the eye
• 2 compartments
1. Anterior compartment: between the cornea
and lens; filled with a clear fluid called
_________ humor
2. Posterior compartment: most of the eye,
behind the lens; contains a gelatinous
material called ________ humor
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14.4 Sense of Vision
Anatomy of the eye
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
choroid
suspensory
ligament
sclera
Figure 14.6 The structures of the human eye.
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