Anatomy & Physiology 34B Lecture
Chapter 13 & 15 – PNS Sensory Systems
I. Overview
A. General Properties of Sensory Systems
B. Somatic Senses
C. Special Senses – Olfactory & Gustatory
II. General Properties of Sensory Systems
A. _______ organs are extensions of the nervous system that respond to changes in the
environment & transmit nerve impulses to the CNS
B. In order to ___________ a sensation, the following are necessary:
1.
A _____________ (chemical, mechanical, temperature, or light) to initiate a nervous
system response
2. A __________ (sensory neuron dendrites or specialized epithelial cell) is a transducer
that converts the stimulus to a nerve impulse
3. ______________ of the nerve impulse from the receptor to the brain, via sensory
(ascending) nerve tracts in the spinal cord
4. _______________ of the perception in the brain’s cerebral cortex, after passing through
the medulla, pons, and thalamus
C. ____________ may be general or special senses
1. _______________ (somatic) senses
a. Have _____________ throughout the skin, muscles, tendons, joint capsules, and viscera.
b. Somatic and visceral __________ _________ transmit impulses from the receptors to
the CNS
2. ______________ senses
a. Are limited to the head and innervated by ____________ nerves
b. Include vision, hearing, equilibrium, taste, and ___________
D. Sense _______________ may be classified several ways
1. By the way they are _______________
a. ________receptors respond to chemicals; found in the tongue, nose, and blood
vessels
b. __________receptors respond to heat and cold; in skin
c. _______ceptors respond to pain and itch; found throughout the body, except in the
brain
d. __________receptors respond to physical deformation of the plasma membrane
caused by touch, pressure, stretch, tension, or vibration; found in skin, viscera, and
joints
e. __________receptors in the eyes respond to light
2. By the ___________________ of receptors in the body
a. ______________ (somatic) senses
1) Have receptors throughout the _______, muscles, tendons, joint capsules, and
viscera.
2) Include mechanoreceptors, thermoreceptors, chemoreceptors, and
______________
b. ______________ senses
1) Are limited to the ______ and innervated by cranial nerves
2) Include _________, hearing, equilibrium, taste, and smell
3. By ____________ of the stimuli
a. _________ceptors detect stimuli in internal organs and produce feelings of visceral
pain, nausea, stretch, and pressure
b. ____________ceptors sense the position and movements of body parts; found in
muscles, tendons, and joint capsules
c. _________ceptors sense external stimuli; include receptors for vision, hearing,
taste, smell, touch, and cutaneous pain
4. By the __________ of their electrical impulse firing frequencies
a. __________ receptors generate a burst of impulses when first stimulated, adapt
quickly, and stop even if stimuli continues (e.g.: touch, pressure, and smell
receptors)
b. ___________ receptors adapt slowly and generate impulses continually (e.g.:
nociceptors, proprioceptors)
III. General Senses
A. ____________ sense receptors include those with unencapsulated and encapsulated nerve
endings
1. __________________ nerve endings are sensory dendrites that are not wrapped in CT
a. __________ nerve endings include thermoreceptors and nociceptors; numerous in
epithelia and CT
b. Tactile (_________) discs are tonic receptors for light touch; found in the
epidermis stratum basale
c. ___________ receptors monitor movements of hairs; found at the base of hair
follicles
2. _______________ nerve endings are dendrites wrapped in glial cells or CT. These
include
a. Tactile (_____________) corpuscles are phasic receptors for light touch and
pressure; found in the dermal papillae
b. ___________ end bulbs are similar to tactile corpuscles, but occur in mucous
membranes rather than in the skin
c. ______________ (lamellated) corpuscles are phasic receptors for deep pressure,
stretch, tickle, and vibration; found deep in the dermis and pancreas
d. _______________ corpuscles are tonic receptors for heavy touch, pressure, stretch,
and joint movements; found in the dermis, hypodermis, ligaments, tendons, and
joint capsules
E. Each sensory __________ has a receptive field
1. A sensory neuron is activated by stimuli that fall within the neuron’s ____________
_________
2. Example: a ______-________ discrimination test
a. In less sensitive skin areas, _______ primary neurons converge on _____ secondary
neuron (a large receptive field), thus two pins 20 mm apart are perceived as _____ pinprick
b. More sensitive skin areas often have smaller receptive areas, with a ______-to-_____
relationship between primary and secondary neurons, thus two pins 2 mm apart are
perceived as ____________
F. The CNS _______________ sensory information
1. Sensory impulses (except smell) travel to the spinal cord (or brain stem), up projection
tracts to the ____________, and are relayed to the cererbral cortex
2. The perceptual _____________ is the level of stimulus intensity necessary for us to be
aware of a sensation
a. To keep from being overwhelmed by sensory input, the CNS can selectively “turn
_____” some stimuli
b. _______________ modulation often occurs in secondary or tertiary neurons in the
sensory pathway
G. The CNS must distinguish the 4 _____________ of a stimulus: modality, location,
intensity, and duration
1. Sensory _____________ is indicated by which types of sensory neurons are activated;
the brain associates a signal from a particular type of receptor with a specific sensation
2. Stimulus ______________ is coded by different types of sensory neurons sending their
impulses through ascending tracts to specific regions of the cerebral cortex
3. Stimulus ____________ is coded by the number of receptors that are activated and by
the frequency of their action potentials
4. ______________ of a stimulus is coded by the duration of action potentials in a sensory
neuron. Neurons may be either:
a. __________ receptors adapt slowly and generate impulses continually (e.g.: nociceptors,
proprioceptors)
b. _____________ receptors generate a burst of impulses when first stimulated, adapt
quickly, and stop even if stimuli continues (e.g.: touch, pressure, and smell receptors)
III. ___________ Senses include touch, proprioception, temperature, and nocioception (pain and
itch)
A. Receptors for somatic senses are found in the _______ and viscera
1. Receptor activation triggers action potentials in associated ____________ sensory
neurons, which travel to the spinal cord and synapse with
2. _____________ sensory neurons (interneurons), in ascending tracts, which cross over to
the thalamus on the opposite side, where they synapse with
3. ______________ sensory neurons, which project to a particular region of the
sematosensory cortex
B. Pain that originates in one area, but is felt in another area is called ______________ pain,
and occurs because multiple primary sensory neurons converge onto a single ascending tract
C. _____________ limb pain in which an amputee feels pain in the amputated limb also
occurs because of nerve convergence in the spinal cord
IV. Special Senses
A. _____________ Sense (sense of smell)
1.
Olfactory receptors are dendritic endings of the _____________ nerve (CN I) that
respond to chemical stimuli
2.
Odor impulses are transmitted it to the olfactory __________ via the following pathway:
a.
b.
Olfactory _____________ cells in nasal epithelium receive the stimulus
The impulse is transmitted via olfactory nerves (CN ____) that extend through the
cribriform plate of the ethmoid bone to the
c.
Olfactory _______ on both sides of the crista galli, beneath the frontal lobes.
Neurons here convey the impulse to neurons of
d.
e.
Olfactory __________, which transmits the impulse to the
Olfactory ___________ within the temporal and frontal lobes, where it is
interpreted as odor
B. __________________ Sense (sense of taste)
1.
Gustatory ____________ are specialized epithelial cells, clustered in taste buds,
that respond to chemical stimuli
2.
Taste _________ are lemon shaped structures composed of gustatory cells
surrounded by supporting cells and basal cells
3.
Each gustatory cell has a ________________ taste hairs that extend through a
taste pore on the taste bud surface
4.
There are 3 major types of tongue ________________:
5.
6.
a.
___________ (circumvallate) papillae - largest but least numerous, arranged in
an inverted V on the back of tongue
b.
______________ papillae - knoblike papilla on the tip & sides of tongue; both
fungiform & vallate papillae contain taste buds
c.
_______________ papillae - short, thick, threadlike; on the anterior 2/3 of
tongue; contains no taste buds
Five basic ____________ are sensed:
a. ___________
b. ___________
c. ___________
d. ___________
e. ___________ – a meaty taste produced by amino acids
Taste impulses are transmitted via the __________pharyngeal (CN IX) and
__________ (CN VII) nerves to the gustatory cortex in the parietal lobes for
interpretation