Chapter 15 Part 1 Flashcards
what are sensory receptors?
specialized cells that monitor specific conditions in the body or external environment
when stimulated, what does a sensory receptor do?
when stimulated, a sensory receptor passes information to the CNS in the form of action potentials along the axon of a sensory neuron
what does the term “sensory pathway” refer to?
the nerves, axons, nuclei, and tracts that deliver somatic and visceral sensory information to their final destinations inside the CNS
Taken together, the receptors, sensory neurons, and sensory pathways make up the ______ division of the CNS
afferent
somatic sensory information is delivered to….
sensory processing centers in the brain
–either the primary sensory cortex of the cerebral hemispheres OR appropriate areas of the cerebellar hemispheres
visceral sensory information is distributed to…
reflex centers in the brain stem and diencephalon
somatic motor commands, regardless of whether they arrive at the conscious or unconscious levels, travel from motor centers in the brain along……..
SOMATIC MOTOR PATHWAYS which consist of motor nuclei, tracts, and nerves
what forms the somatic nervous system?
the motor neurons and pathways that control skeletal muscles
the term “general senses” is used to describe…
our sensitivity to temperature, pain, touch, pressure, vibration, and proprioception
where are general sensory receptors located on the body?
distributed throughout the body
the harder the pressure, the _______ the frequency of action potentials
higher
sensory information is interpreted on the basis of…..
the frequency of action potentials
the arriving information is called a _____
the conscious awareness of a sensation is called ________
the arriving information is called a SENSATION
the conscious awareness of a sensation is called PERCEPTION
what are the “special senses”?
olfaction (smell)
vision (sight)
gustation (taste)
equilibrium (balance)
hearing
what can you say about the receptors of the 5 special senses?
they are structurally more complex than the receptors for general senses
sense receptors are protected by surrounding tissue
WHERE are special sensory receptors located?
in SENSE ORGANS such as the eye or ear
sensory receptors represent the interface between the ____ and the _____
nervous system and the internal and external environments
What is transduction?
the translation process of a sensory receptor detecting an arriving stimulus and translating the stimulus into an action potential and conducting it to the CNS
What happens if transduction does NOT occur?
as far as you’re concerned, the stimulus didnt even exist
explain what “receptor specificity” is
each receptor has a characteristic sensitivity
a touch receptor is very sensitive to pressure but relatively insensitive to chemical stimuli.
whereas a taste receptor is sensitive to dissolved chemicals but insensitive to pressure
what are the SIMPLEST of all receptors
the dendrites of sensory neurons
receptor specificity may result from ______ or _______
- the actual structure of the receptor cell or..
- accessory cells or structures that shield the receptor cell from other stimuli
“the simplest receptors are the dendrites of sensory neurons.”
the branching tips of these dendrites are called ___________. explain
free nerve endings.
they are not protected by accessory structures
true or false:
free nerve endings show high receptor specificity
explain
FALSE - they show little receptor specificity
for example, free nerve endings that respons to tissue damage by providing pain sensations may be stimulated by chemical stimulation, pressure, temp changes, or trauma
true or false:
complex receptors such as the eye’s visual receptors provide very specific information.
explain
true
complex receptors are protected by accessory cells and connective tissue layers. These receptors are seldom exposed to any other stimulus than light, so they provide very specific information
the area monitored by a single receptor is called its….
receptor field
the larger the receptive field, the _______ your ability to localize a stimulus
poorer
whenever a sufficiently strong stimulus arrives in the receptive field, explain what happens
the CNS receives the information: “stimulus arriving at receptor X”
what areas of our body have large receptive fields? what areas have very small receptive fields?
what does this indicate
large receptive fields = a touch receptor on the general body surface
small receptive fields = tongue or fingertips
this means that the brain can precisely locate the stimulus when it arrives at the tongue or fingertips, but it only defines a broad area when a stimulus arrives from a general touch receptor on the body surface
sensory information is sent to the CNS EXCLUSIVELY in the form of………
action potentials, which are electrical events
true or false:
an arriving stimulus can take only 1 form
false
an arriving stimulus can take many forms such as a physical force (pressure), a dissolved chemical, sound, or light
recap: what is transduction?
the translation of an arriving stimulus into an action potential by a sensory receptor
when does the transduction process begin?
transduction begins when a stimulus changes the transmembrane potential of a receptor cell (called a receptor potential)
what is a “receptor potential”
when a stimulus changes the transmembrane potential of a receptor cell (signals the beginning of transduction)
a receptor potential is either a graded ______ or a graded ______
depolarization or hyperpolarization
the stronger the stimulus, the ______ the receptor potential
larger
for the general senses, what are the typical receptors and what is the sensory neuron?
for the general senses, the typical receptors are the DENDRITES OF SENSORY NEURONS and the sensory neuron is the RECEPTOR CELL
Any receptor potential that depolarizes the plasma membrane will bring the membrane closer to….
threshold
a depolarizing receptor potential in a neural receptor is called a……….
generator potential
what gives us sensations of taste, hearing, equilibrium, and vision?
specialized receptor cells that communicate with sensory neurons across chemical synapses
the receptor cells develop graded receptor potentials in response to stimulation. this change in membrane potential alters the rate of neurotransmitter release at the synapse.
the result is depolarization or hyperpolarization of the sensory neuron. if sufficient depolarization occurs, an action potential appears in the sensory neuron
in this case, the receptor potential and generator potential occurred in different cells. the receptor potential developed in the receptor cell, and the generator potential appears later in the sensory neuron (gets depolarized)
whenever a sufficiently large ____ appears, action potentials develop in the axon of a sensory neuron
generator potential
the greater the degree of sustained depolarization at the axon hillock….
the higher the frequency of action potentials in the afferent fiber
sensory information that arrives at the CNS is routed according to the _____ and ___ of the stimulus
location and nature
sensations of touch, pressure, pain, and temperature arrive in the brain where?
at the primary sensory cortex
an arriving stimulus reaches a cortical neuron via what structre?
labeled line
what does “modality” mean
type of stimulus (ie: touch or pressure or light or sound)
each labeled line consists of ____ carrying information about __modality(ies)
axons, 1 modality
What indicates the TYPE of stimulus to the brain?
the identity of the labeled line
explain what happens when you get a touch sensation on the face
the labeled line with a TOUCH MODALITY passes the information from the receptor to the facial region of your primary sensory cortex, which makes you PERCEIVE that touch on your face
the identity of the labeled line indicates the TYPE of stimulus.
what conveys all other characteristics of the stimulus such as its strength, duration, and variation?
all these characteristics are conveyed by the frequency and pattern of action potentials
this translation of complex sensory information into meaningful patterns of action potentials is called….
sensory coding
what are TONIC RECEPTORS?
sensory neurons that are always active
what is the name of the receptors that are normally inactive, but become active for a short time whenever a change occurs in the conditions they are monitoring?
phasic receptors
tonic receptors give information about…
the background level of stimulation (the frequency with which they generate action potentials indicates this)
phasic receptors provide information about…
the intensity and rate of change of a stimulus
what receptors can convey extremely complicated sensory information?
receptors that COMBINE phasic and tonic coding
______is a reduction in sensitivity in the presence of a constant stimulus
adaptation
peripheral adaptation occurs when…
the level of receptor activity changes.
the receptor responds strongly at first, but its activity gradually declines due to the size of the generator potential gradually decreasing
peripheral adaptation is characteristic of which receptors?
phasic receptors
because they use peripheral adaptation, phasic receptors could also be called _______ receptors
fast-adapting receptors
temperature receptors (thermoreceptors) are __________ receptors
explain
phasic
we dont notice room temperature changes unless it changes suddenly
tonic receptors show ______ peripheral adaptation and are thus called ______ receptors
little
slow-adapting receptors
give an example of slow adapting receptors
pain receptors
what is central adaptation?
adaptation that occurs along sensory pathways inside the CNS
for instance, a few seconds after beinf exposed to a new smell, awareness of the stimulus virtually disappears
can output from higher centers increase receptor sensitivity?
explain
yes
RAS (reticular activating system) in the midbrain helps to focus our attention and heightens or reduces our awareness of arriving sensations
ex: when we “listen carefully”, our sensitivity and awareness of auditory stimuli increases
can output from higher centers INHIBIT transmission along a sensory pathway?
yes
this occurs when we walk along a crowded city street. we automatically tune out the high level of background noice
what is the simple classification scheme for general sense receptors
- exteroreceptors - provide info about the external environment
- proprioreceptors - provide info about the positions of skeletal muscles and joints
- interoreceptors – monitor visceral organs and their functions
a more DETAILED classification system divides the general sensory receptors into….
4 types by the nature of the stimulus that excites them
pain - nociceptors
temperature - thermoreceptors
physical distortion - mechanoreceptors
chemical concentration - chemoreceptors
the difference between a somatic and visceral receptor is its ____ not its _______
its LOCATION not its STRUCTURE
Explain the similarities and differences between a pain receptor in the gut and a pain receptor in the skin
they both look and act the same, but the 2 sensations are delivered to separate locations in the CNS
are there any proprioceptors in our visceral organs?
NO – proprioception is a purely somatic sensation
true or false:
the visceral organs have more pain, temperature, and touch receptors than elsewhere in the body
FALSE – visceral organs have fewer
true or false
the sensory information in the visceral organs is poorly localized
explain
true
the sensory information is poorly localized because the receptive fields are very large and may be widely separated
does a lot of the information provided by afferent fibers reach our awareness? explain
NO. only about 1% actually reaches our awareness.
for instance, we dont feel our clothes when we wear them of hear the hum of the engine when riding a car
pain receptors
nociceptors
nociceptors are especially common in….
the superficial portions of the skin, in joint capsules, within the periostea of bones, and around the walls of blood vessel
do pain receptors have large receptive fields?
yes
they are free nerve endings. therefore, it is often difficult to determine the exact source of a painful sensation
nociceptors may be sensitive to what 3 things?
-extreme temp
-mechanical damage
-dissolved chemicals, such as chemicals released by injured cells
VERY STRONG STIMULI will stimulate which nociceptor?
ALL OF THEM — temp, mechanical, and chemical
often described as a burning pain
which types of axons carry pain sensations?
Type A and Type C
Type A = fast pain
Type C = slow pain
fast pain is described as ______ pain
prickling
slow pain is described as ______ pain
burning and aching
what type of events produce prickling (fast) pain?
injection or a deep cut
explain what happens with fast pain in relation to the CNS
fast pain reaches the CNS quickly.
somatic reflexes are triggered
relayed to primary sensory cortex (so they receive conscious attention)
is fast pain able to be localized?
yes – several inches in diameter
slow pain sensations carry a GENERALIZED activation of ______ and _____
reticular formation and thalamus
does slow pain become localized?
no— individual only has a general idea of the are affected
are pain receptors tonic or phasic?
TONIC
peripheral adaptation does not occur. the receptors continue to respond as long as the painful stimulus remains
painful sensations stop only after…..
tissue damage has ended
painful sensations stop only after tissue damage has ended. however, what can reduce the PERCEPTION of the pain while the pain receptors are still stimulated?
central adaptation
the sensory neurons that bring pain sensations into the CNS release……
glutamate and/or substance P as neurotransmitters
these neurotransmitters facilitate neurons along the pain pathways
the level of pain felt by an individual can be reduced by….
the release of endorphins and enkephalins within the CNS
INHIBITS ACTIVITY ALONG PAIN PATHWAYS IN THE BRAIN
Endorphins and enkephalins are structurally similar to _______
morphine
where are endorphins and enkephalins located?
the limbic system, hypothalamus, and reticular formation
explain how endorphins help to reduce pain
endorphins bind to the presynaptic membrane and prevent the release of substance P, reducing the conscious perception of pain, although the painful stimulus still exists
