Chapter 10: Sensory Physiology Flashcards
what branch is involved in sensory physiology?
afferent branch of peripheral nervous system
conscious interpretation of the world based on sensory systems, memory, and other neural processes
perception
How does information travel?
- sent from periphery to CNS
- external environment (sensory receptors)
- internal environment
what are the sensory systems that enable us to perceive the external environment?
- somatosensory system
- somatic
- proprioception
sensations of the skin
somatic division of somatosensory system
perception of limb and body positions
proprioception division of somatosensory system
what are our special senses that help us perceive the external environment?
- vision
- hearing
- balance and equilibrium
- taste
- smell
- Detect specific form of energy in the external environment
- Modality: light, sound, pressure, temperature, chemicals
sensory receptors
a given sensory receptor is specific for each?
modality
is the modality that the receptor is most responsive.
adequate stimulus
modality that activates photoreceptors causing the perception of light
blow to the eye (pressure)
what are types of sensory receptors?
- chemoreceptors
- mechanoreceptors
- photoreceptors
- thermoreceptors
what are some stimuli for chemoreceptors?
- oxygen
- pH
- organic molecules
what are some stimuli for mechanoreceptors?
- pressure
- cell stretch
- vibration
- acceleration
- sound
what is the stimulus for photoreceptors?
photons of light
what is the stimulus for thermoreceptors?
varying degrees of heat
conversion of stimulus energy into electrical enery
sensory transduction
what are the potentials involved in sensory transduction?
- receptor or generator potentials
- graded potential
- opening or closing of ion channels
- triggered by sensory stimuli
what happens if the receptor potential exceeds the threshold?
- can generate an action potential
- release of neurotransmitters
what are the two basic forms sensory receptors exist in?
- neural sensory receptor
- sensory receptor cell
-neurons
with free nerve endings
-they may have myelinated or
unmyelinated axons.
simple receptors
have nerve
endings enclosed in connective tissue capsules
complex neural receptors
most special senses receptors are cells
that release neurotransmitter onto sensory
neurons, initiating an action potential
nonneural receptors
specific neural pathways transmitting information of a specific modality
labeled lines
what dos activation of a specific pathway cause?
causes perception of the associated modality, regardless of which stimulus actually activated the pathway
where do the pathways for different modalities terminate in?
different sensory areas of the cerebral cortex
-project to the thalamus
most sensory pathways
modifies and relays information to cortical centers
thalamus
project primarily to the cerebellum
equilibrium
what does a sensory unit include?
- single afferent neuron and all associated receptors
- all receptors are of the same type
- activation potential may result from activation of receptors
- receptive field
area in which a sensory unit is activated
receptive field
how the nervous system identifies the type, strength, and location of a stimulus
sensory coding
how is coding done for a stimulus type?
- receptor type activated (light waves)
- specific pathway (to visual cortex)
is perception based on a single sensory pathway?
no, brain must integrate info from different sensory systems
do we have wet receptors on our skin?
no
when activated, appropriately transmit a combination of signals that we interpret as wetness.
thermoreceptors and touch receptors
what is involved in coding for stimulus intensity?
- frequency of action potentials
- number of receptors activated
frequency of action potentials
frequency coding
number of receptors activated
population coding
how do stimulus and receptors correlate?
the stronger the stimulus, the more receptors it activates (recruitment)
-can be from same or other afferent neurons
A decrease over time in the magnitude of the receptor potential in the presence of a constant stimulus.
receptor adaptation
which receptors show little adaptation to a constant stimulus?
tonic receptors, muscle stretch receptors
which receptors adapt quickly to a constant stimulus?
phasic receptors, olfactory receptors
slowly
adapting receptors that respond
for the duration of a stimulus
tonic receptors
rapidly adapt to a
constant stimulus and turn off
phasic receptors
- based on receptive fields in somatic senses and vision (size of field & degree of overlap)
- acuity
- lateral inhibition
coding of stimulus location
precision with which a stimulus is perceived
acuity
what are the steps of lateral inhibition?
- primary neuron response is proportional to stimulus strength
- pathway closest to the stimulus inhibits neighbors
- inhibition of lateral neurons enhances perception of stimulus
what happens in somatosensory pathways?
- pain, temperature, & coarse touch cross the midline in the spinal cord
- fine touch, vibration, & proprioception pathways cross the mindline in the medulla
- sensory pathways synapse in the thalamus
- sensations are perceived in the primary somatic sensory cortex
depends on chemicals in air that bind to chemoreceptors in the olfactory epithelium
olfaction
located in nasal cavity
olfactory epithelium
what are the three cell types of olfactory epithelium?
- receptor cells
- basal cells
- supporting cells
neurons that respond to odorants
receptor cells of olfactory epithelium
precursor cells for new receptor cells
basal cells of olfactory epithelium
maintain extracellular environment
supporting cells of olfactory epithelium
lies high within
the nasal cavity, and its olfactory neurons
project to the olfactory bulb
olfactory epithelium
carried through the
olfactory cortex to the cerebral cortex
and the limbic system.
sensory input at the receptors
- live only about 2 months
- replaced by new neurons whose axons must find their way to the olfactory bulb
olfactory neurons in the olfactory epithelium
neurons that are replaced continuously
olfactory receptor cells
- located in mucus
- transport hydrophobic odorants to receptors
olfactory binding proteins
- *project into mucus
- 400 different chemoreceptor proteins
- olfactory sensory neurons in different combinations
cilia
how does olfactory signal transduction work?
- chemical binds to receptor
- activates G protein (G olf)
- activates adenylate cyclase–> caMP
- cAMP directly binds cation channels, opening them
- Na+ and Ca2+ enter cell–> depolarization
sense of taste
gustation
how many taste buds do we have and where are they?
- more than 10,000
- tongue
- roof of mouth
- pharynx
what part of a taste bud is exposed to saliva in the mouth?
pore of taste bud
how many taste receptors per taste bud?
50-150 taste receptors
- modified epithelial cells
- respond to tastants
have support cells
taste buds
are non-neural epithelium
taste receptor cells
each taste cell is sensitive to?
only one taste
support cells
Type I
receptor cells
Type II
presynaptic cells
Type III
what protein is involved in taste transduction?
Gustducin (special G protein)
may sense salt when Na+ enters through channels
Type I support cells
receptors bind either bitter,
sweet, or umami ligands and release
ATP as a signal molecule.
receptor cells with G protein-coupled membrane receptors
sense sour taste (H+) when H+ enters the cell through channels
presynaptic cells
how does taste work?
- ligands activate the taste cell
- various intracellular pathways are activated
- Ca2+ signal in the cytoplasm
triggers exocytosis or ATP
formation. - Neurotransmitter or ATP is
released. - Primary sensory neuron fires
and action potentials are
sent to the brain.
directs sound waves into the ear
pinna
separate the fluid-filled inner ear from the air-filled middle ear
oval window and round window
mechanical waves caused by air molecules put into motion
sound waves
is the perception of energy carried by sound waves
hearing
is determined by the frequency of the sound waves. Hertz (number of waves per second)
pitch of a sound
low frequency
low pitch
high frequency
high pitch
what is the human range of hearing?
20-20,000 Hz
an interpretation of intensity, a function of wave amplitude (height) 60dB conversation, 120dB danger
loudness
distinguished by their frequency, measured in hertz (Hz), and amplitude, measured in decibels (dB).
sound waves
what does the cochlea contain?
- Perilymph in vestibular and tympanic duct
- Endolymph in cochlear duct
- Cochlear duct contains organ of Corti
similar to plasma
perilymph in vestibular and tympanic duct
- secreted by epithelial cells
- similar to intracellular fluid (high K+ and Ca2+)
endolymph in cochlear duct
- hair cell receptors and support cells
- sits on basilar membrane
- partially covered by tectorial membrane
cochlear duct contains organ of corti
bends sterocilia on non-neural hair cells
tectorial membrane
what happens when sound waves strike the tympanic membrane?
they become vibrations
where is the sound wave energy transferred to?
the 3 bones of the middle ear, which vibrate
attached to the membrane of the oval window
the stapes
create fluid waves within the cochlea
vibrations of the oval window
push on the flexible membranes of the cochlear duct
fluid waves
what happens when hair cells bend and ion channels open?
creates an electrical signal that alters neurotransmitter release
creates action potentials that travel through the cochlear nerve to the brain
neurotransmitter release onto sensory neurons
transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window
energy from the waves
transforms sound waves into electrical signals
cochlea
project to brain in medulla oblongata
primary auditory neurons
- project to higher nuclei
- Synapse in nuclei in midbrain and thalamus before projecting into auditory cortex
secondary sensory neurons
requires simultaneous input from both ears
localization of a sound source
has variable sensitivity to sound
wave frequency along its length
basilar membrane
determines the displacement
of the basilar membrane
frequency of sound waves
creates
a code that the brain translates as information about the pitch
of sound.
location of active hair cells
no transmission through either external or middle ear
-blockage or trauma to the bones
conductive hearing loss
Damage to neural pathway between ear and cerebral cortex or damage to cortex itself
central hearing loss
Damage to structures of inner ear (ex. hair cells)
sensorineural hearing loss
senses
the tilt of the head toward
the right or left shoulder
posterior canal of the vestibular apparatus
senses rotation of the head as
it turns left or right, such as that
which occurs when shaking the head
“no.”
horizontal canal
senses
rotation of the head from front
to back, such as that which
occurs when nodding “yes.”
superior canal
pushes on the gelatinous cupula and activates the hair cells.
movement of endolymph
when the head turns right, endolymph pushes the cupula to the…?
left
bulges between semicircular canals and cochlea
utricle and saccule
oriented to detect linear acceleration
utricle and saccule
detects forward and backward motion
utricle
detects up and down motion
saccule
- hair cells
- located in gelatinous material covered by otoliths
receptor cells
The conversion of stimulus energy into a change in membrane potential is known as
transduction
The intensity of a sensory stimulus is coded by…?
the frequency of action potentials
The organ of Corti sends electrical information about sound to the brain. The perceived pitch of a sound is determined by….?
the location of the activated hair cells on the basilar membrane.
