The General and Special Senses. Olfaction & Gustation

1.

PowerPoint® Lecture Slides
prepared by
Kureysh M. Khamchiyev,
The Dep. of Normal
Physiology, AMU
CHAPTER
9
The General and
Special Senses.
Olfaction &
Gustation
© 2017 Kureysh M. Khamchiyev, AMU.

2.

Chapter 9 Learning Outcomes
9-1
• Explain how the organization of receptors for the general senses
and the special senses affects their sensitivity.
9-2
• Identify the receptors for the general senses, and describe how
they function.
9-3
• Describe the sensory organs of smell, and discuss the processes
involved in olfaction.
9-4
• Describe the sensory organs of taste, and discuss the processes
involved in gustation.
© 2017 Kureysh M. Khamchiyev, AMU

3.

Sensory Receptors (9-1)
• Can be special cell processes
• Or separate cells
• Monitor conditions both inside and outside the
body
© 2017 Kureysh M. Khamchiyev, AMU

4.

Free Nerve Endings (9-1)
• The simplest receptors
• Are modified dendritic endings
• Examples:
• Touch receptors
• Pain receptors
• Heat receptors
• Taste receptors
© 2017 Kureysh M. Khamchiyev, AMU

5.

Separate Receptor Cells (9-1)
• Complex structures
• Associated with supportive cells
• Examples:
• Visual receptors in the eyes
• Auditory receptors in the ears
© 2017 Kureysh M. Khamchiyev, AMU

6.

The Receptive Field (9-1)
• The area monitored by a single receptor
• The smaller the field, the more precise the sensory
information
© 2017 Kureysh M. Khamchiyev, AMU

7.

Sensation and Perception (9-1)
• Sensation
• Occurs in the brain
• The action potential from the afferent pathway arrives in
sensory cortex
• Perception
• Awareness and interpretation of sensory input by the
integration areas of cerebral cortex
© 2017 Kureysh M. Khamchiyev, AMU

8.

Adaptation (9-1)
• A reduction in sensitivity due to a constant
stimulus
• Some sensory receptors adapt quickly (e.g.,
jumping into a cold lake)
• Some are slow to adapt or do not adapt at all, like
pain receptors
© 2017 Kureysh M. Khamchiyev, AMU

9.

General Senses (9-1)
• Temperature
• Pain
• Touch
• Pressure
• Vibration
• Proprioception (body position)
• Occur throughout the body
© 2017 Kureysh M. Khamchiyev, AMU

10.

Special Senses (9-1)
• Olfaction (smell)
• Gustation (taste)
• Vision
• Equilibrium (balance)
• Hearing
• Concentrated in the sense organs and located in
the head
© 2017 Kureysh M. Khamchiyev, AMU

11.

Figure 9-1 Receptors and Receptive Fields.
Receptive
field 1
© 2017 Kureysh M. Khamchiyev, AMU
Receptive
field 2

12.

Checkpoint (9-1)
1. What is adaptation?
2. Receptor A has a circular receptive field with a
diameter of 2.5 cm. Receptor B has a circular
receptive field 7.0 cm in diameter. Which receptor
provides more precise sensory information?
3. List the five special senses.
© 2017 Kureysh M. Khamchiyev, AMU

13.

Classes of General Sensory Receptors (9-2)
• Classified by type of stimulus that activates them
• Nociceptors respond to pain
• Thermoreceptors respond to temperature
• Mechanoreceptors respond to touch, pressure, and
body position
• Chemoreceptors respond to chemical stimuli
© 2017 Kureysh M. Khamchiyev, AMU

14.

Nociceptors (9-2)
• Free nerve endings that adapt very slowly
• Can respond to extremes of temperature,
mechanical damage, dissolved chemicals
• Fast pain transmitted to CNS through myelinated axons
• Slow pain transmitted by unmyelinated axons and is burning
or aching
• Referred pain is perception of pain in an unrelated area of
the body
© 2017 Kureysh M. Khamchiyev, AMU

15.

Figure 9-2 Referred Pain.
Heart
Liver and
gallbladder
Stomach
Small
intestine
Appendix
Colon
© 2017 Kureysh M. Khamchiyev, AMU
Ureters

16.

Thermoreceptors (9-2)
• Free nerve endings
• In dermis, skeletal muscles, liver, and hypothalamus
• Cold receptors
• More numerous than warm receptors, although there is no
known difference in structure
• They use the same pathway as pain receptors, but
thermoreceptors are adaptive
© 2017 Kureysh M. Khamchiyev, AMU

17.

Three Classes of Mechanoreceptors
1. Tactile receptors
Touch
2. Baroreceptors
Pressure
3. Proprioceptors
Position
© 2017 Kureysh M. Khamchiyev, AMU

18.

Tactile Receptors (9-2)
Include fine touch and pressure receptors and crude
touch and pressure receptors
Six types of tactile receptors in the skin
1. Free nerve endings responding to temperature and pain
2. Root hair plexus
3. Tactile (Merkel) disc
4. Tactile (Meissner) corpuscle
5. Lamellated (pacinian) corpuscle
6. Ruffini corpuscle
© 2017 Kureysh M. Khamchiyev, AMU

19.

Figure 9-3 Tactile Receptors in the Skin.
Hair
Free
Tactile
Tactile disc
(innervating corpuscle nerve
ending
Merkel cell)
Dendrites
Sensory
nerve fiber
Ruffini corpuscle
Free nerve
endings
Root hair
plexus
Lamellated
corpuscle
Ruffini
corpuscle
Dendrite
Sensory
nerves
Dermis
Lamellated
corpuscle
Root hair
plexus
Merkel cells
Dendrites
Tactile disc
Dermis
Tactile discs innervating
Merkel cells
© 2017 Kureysh M. Khamchiyev, AMU
Tactile corpuscle

20.

Baroreceptors (9-2)
• Monitor changes in pressure in the viscera
• Adapt readily
• Found in the major blood vessels, lungs, digestive,
and urinary tracts
© 2017 Kureysh M. Khamchiyev, AMU

21.

Figure 9-4 Baroreceptors and the Regulation of Autonomic Functions.
Baroreceptors of Carotid
Sinus and Aortic Sinus
Baroreceptors of Lung
Baroreceptors of
Digestive Tract
Baroreceptors of
Bladder Wall
© 2017 Kureysh M. Khamchiyev, AMU
Baroreceptors of Colon

22.

Proprioceptors (9-2)
• Monitor position, tension in tendons and
ligaments, state of muscle contraction
• Nonadaptive and include:
• Free nerve endings that monitor joint capsule pressure,
tension, and movement
• Golgi tendon organs that monitor strain on tendons
• Muscle spindles that monitor the length of a muscle
© 2017 Kureysh M. Khamchiyev, AMU

23.

Chemoreceptors (9-2)
• Respond to chemicals in solution in body fluids
• Include CNS receptors that monitor CSF, plasma
concentrations of carbon dioxide, and pH
• Key peripheral chemoreceptors for plasma carbon
dioxide and pH are in the carotid bodies and
aortic bodies
© 2017 Kureysh M. Khamchiyev, AMU

24.

Figure 9-5 Locations and Functions of Chemoreceptors.
Chemoreceptors in and
near Respiratory Centers
of Medulla Oblongata
Chemoreceptors
of Carotid Bodies
Chemoreceptors
of Aortic Bodies
© 2017 Kureysh M. Khamchiyev, AMU
Trigger reflexive
adjustments in
depth and rate of
respiration
Cranial
nerve IX
Cranial
nerve X
Trigger reflexive
adjustments in
respiratory and
cardiovascular
activity

25.

Checkpoint (9-2)
4. List the four types of general sensory receptors,
and identify the nature of the stimulus that excites
each type.
5. Identify the three classes of mechanoreceptors.
6. What would happen if information from
proprioceptors in your legs were blocked from
reaching the CNS?
© 2017 Kureysh M. Khamchiyev, AMU

26.

Special Sense of Olfaction (9-3)
• Olfactory organs found in the nasal cavity
• Olfactory epithelium, containing olfactory
receptor cells, supporting cells, and stem cells,
lines the nasal cavity
• Olfactory glands, which are deeper, secrete
mucus
• Air is warmed and moisturized as it is inhaled
© 2017 Kureysh M. Khamchiyev, AMU

27.

Special Sense of Olfaction (9-3)
• Olfactory receptor cells
• Modified neurons with chemical receptors called odorantbinding proteins on the cilia
• Odorants are chemicals in the air that bind to the
proteins
• Respond to over 1000 unique smells
© 2017 Kureysh M. Khamchiyev, AMU

28.

Olfactory Pathways (9-3)
• Axons projecting from the olfactory epithelium
• Bundled and pass through the cribriform plate of the ethmoid
bone and into olfactory bulb
• Olfactory tracts extend back to the olfactory cortex of the
cerebrum, the hypothalamus, and the limbic system
• Olfaction is the only sense that is NOT routed
through the thalamus
© 2017 Kureysh M. Khamchiyev, AMU

29.

Figure 9-6a The Olfactory Organs.
Olfactory Pathway to the Cerebrum
Olfactory Olfactory Olfactory Olfactory Central
epithebulb
nerve
tract
nervous
lium
Fibers
system
(N I)
Cribriform
plate
Superior
nasal
concha
© 2017 Kureysh M. Khamchiyev, AMU
The olfactory organ on the right
side of the nasal septum.

30.

Figure 9-6b The Olfactory Organs.
Basal cell:
divides to
replace
worn-out
To
olfactory
receptor Olfactory olfactory
gland
bulb
cells
Cribriform
plate
Areolar
tissue
Olfactory
nerve fibers
Developing
olfactory
receptor cell
Olfactory
receptor cell
Olfactory
epithelium
Supporting cell
Mucous layer
Olfactory cilia:
surfaces contain
receptor proteins
Substance being smelled
© 2017 Kureysh M. Khamchiyev, AMU
An olfactory receptor is a modified neuron
with multiple cilia extending from its free
surface.

31.

Checkpoint (9-3)
7. Define olfaction.
8. How does repeated sniffing help to identify faint
odors?
© 2017 Kureysh M. Khamchiyev, AMU

32.

Special Sense of Gustation (9-4)
• Gustatory receptors
• Found in the gustatory cells of the taste buds, which are
found on the sides of the papillae
• Circumvallate papillae most numerous and on the front 2/3 of
the tongue
• Gustatory cells have microvilli (taste hairs) that
extend out through the taste pore
© 2017 Kureysh M. Khamchiyev, AMU

33.

Special Sense of Gustation (9-4)
• Taste hairs respond to chemicals in solution
• Trigger a change in the membrane potential of the
taste cells
• Primary taste sensations
• Sweet, sour, bitter, salty, and umami
• Also receptors in the pharynx for water
© 2017 Kureysh M. Khamchiyev, AMU

34.

The Taste Pathway (9-4)
• Extends from the taste cell axons found in:
• Facial nerve (N VII)
• Glossopharyngeal (N IX)
• Vagus (N X)
• Fibers synapse in the medulla oblongata
• Those neurons extend into the thalamus
• Neurons project to the primary sensory cortex
© 2017 Kureysh M. Khamchiyev, AMU

35.

Figure 9-7 Gustatory Receptors.
Water receptors
Umami
(pharynx)
Taste
buds
Sour
Bitter
Salty
Sweet
Taste
buds
Circumvallate papilla
Taste buds
Supporting
cell
Tastes are detected by gustatory receptors within
taste buds, which form pockets along the sides of
epithelial projections called papillae.
LM x 280
Gustatory
cell
Taste
hairs
(microvilli)
Taste
pore
A diagrammatic view of the structure
of a taste bud, showing gustatory
receptor cells and supporting cells.
© 2017 Kureysh M. Khamchiyev, AMU

36.

Checkpoint (9-4)
9. Define gustation.
10. If you completely dry the surface of your tongue
and then place salt or sugar crystals on it, you
cannot taste them. Why not?
© 2017 Kureysh M. Khamchiyev, AMU