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Physiology of Receptors
UTCVM phys test 2 ch. 8
145
Physiology
Graduate
09/24/2011

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Term
Specific type of stimulus to which a receptor has the lowest threshold
Definition
adequate stimulus
Term
senstive to circulating or applied chemicals. gustatory and olfactory
Definition
chemoreceptors
Term
Respond to changes in mechanical energy.
Definition
mechanoreceptors
Term
Muscle spindles, touch receptors, tendon organs, and hair cells. Hearing and balance
Definition
mechanoreceptors
Term
receptors that are sensitive to light. Include rods and cones in the retina
Definition
photoreceptors
Term
receptors sensitve to temp changes.
Definition
thermoreceptors
Term
Receptors classified by the general type of sensation that the receptors convey (5)
Definition
Exteroceptors
Interoceptors
proprioceptors
nociceptors
teleceptors
Term
Receptors that receive info from the general body surface. Concerned with info about the external environment. Cutaneous receptors
Definition
Exteroceptors
Term
receptors that lie inside the body (viscera or blood vessels) a.k.a. visceroceptors. pain or chemoreceptors
Definition
interoceptors
Term
receptors that deal with body sense and position of body parts in space. Located in muscles, tendons, and joints
Definition
proprioceptors
Term
receptors that transmit the sensation of pain
Definition
nociceptors
Term
receptors of a sensation of events that originate at some distance from the body. Eyes, ears, nose.
Definition
teleceptors
Term
Mechanoreceptors, themoreceptors, and nociceptors
Definition
somatosensory receptors
Term
Sensory fibers of neurons (periphreal receptors) are loacted in peripheral nerves and their cell bodies in ____ for spinal nerves or ________ for cranial nerves
Definition
dorsal root ganglia; ganglia near CNS
Term
There are few ______ but many are mixed with _______.
Definition
purely sensory nerves; motor fibers
Term
All general body sensory information is projected to the _________ in the brain for conscious perception and some goes to the ________ for control of motor activity.
Definition
somatosensory cortex; cerebellum
Term
devoid of hair
Definition
glabrous
Term
3. types of receptors coming from cutaneous areas
Definition
Mechano (touch and pressure), thermo, and nociceptors
Term
sensational functions of cutaneous areas are served by free nerve ending s associated with
Definition
hair follicles
Term
Glabrous, A-beta fibers, Slow adaptive mechanoreceptors that detect velocity and position, sense of touch-pressure on skin.
Definition
Merke's cells
Term
warm receptors on skin
Definition
ruffini's corpuscles
Term
cold receptors on skin
Definition
end bulbs of krause
Term
Glabrous, A-beta fibers, quick adaptive,mechanoreceptors, velocity and instantaneous position. sense of contact and flutter.
Definition
Meissner's corpuscles
Term
Glabrous, A-beta fiber, quick adapting mechanoreceptors. Celocity and higher derivatives of position. Contact and vibration.
Definition
Pacinian corpuscles
Term
Respond by firing impulses when stimulating source is stationary as well as when it is moving.
Definition
Position and velocity receptors (this is one type)
Term
fire only when stimulating source is moving.
Definition
velocity mechanoreceptors
Term
fire only at the onset of displacement
Definition
transient mechanoreceptors
Term
Velocity receptor. Large myelinated axons. supply guard hairs. 3-15 hairs/sensory fiber. Moving 1 hair is not as effective as moving several in succession.
Definition
Type T
Term
Velocity receptor. Associated with fine myelinated axons. Innervate down and guard hair. More sensitve to slight movements of the hair. Adaption is very slow.
Definition
Type G
Term
Velocity receptor. More sensitve to hair movement than types T and G. persistent and irregular discharge when hair is moved and HELD in new position.
Definition
Type D.
Term
The number and location of the receptors served by a single neuron
Definition
receptive field
Term
density of receptive field determines the degree of
Definition
two-point discrimination
Term
a larger number of SMALL receptive fields and little convergence predict
Definition
improved two-point discrimination
Term
Highly localized and refined sensitvity
Definition
epecritic
Term
poorly localized and crude senstaions
Definition
protopathic
Term
continual discharge for any given muscle length or joint angle
Definition
slow adapters
Term
joint and muscle receptors (5)
Definition
GTO, Pacinian corpuscles, Ruffini's corpuscles, Merkel's endings, and muscle spindles.
Term
deep pain is served by ____. Last to succumb to pressure.
Definition
small fibers.
Term
sensory processing begins in
Definition
specialized membranes of receptor cells
Term
specialized cells exhibit two properties that are important in processing stimulus signals.
Definition
1) differential sensitivity (selective and specific)
2) ability to amplify signal they recieve
Term
each receptor cell transduces the stimulus into a _________
Definition
change in membrane potential.
Term
Receptor cells are sometimes able to respond to _______ other than their adequate stimulus
Definition
stimulus types
Term
In photoreceptors, change in molecular conformation changes the membrane conductance. So _____ on the eyeball will excited the retinal cells and the brain will perceive flashes of light.
Definition
pressure
Term
a small stretch applied to the relaxed muscle leads to a small hypopolarization called the
Definition
receptor potential
Term
Once action potentials have started firing, the frequency is directly proportional to the
Definition
degree of strech
Term
receptor potentials are _____ in amplitude
Definition
graded
Term
Unlike Na current of an action potential, the receptor current is not ________ and therefore spreads only by ___________
Definition
regenerative; passive electrotonic means.
Term
The receptor potential is like an _____ at a synaptic junction.
Definition
EPSP
Term
depolarizing receptor potential spreads electronically to a spike-initiating zone in the axon membrane which generates action ptoentials. this requires that the membranes at the _____ serve as the receptor. most receptors in the body are of this type.
Definition
terminal dendrite; Reception by dendritic ending of a neuron
Term
utilize non-neural receptor cells. A depolarizing or hyperploarizing receptor potential spreads electrotonically to the presynaptic portion of the receptor cell. Modulating the release of transmitter substance. The postsynaptic action of the transmitter then modulates the frequency of impulses generated via _________; in the dendrite of an afferent nerve fiber. IT IS NOT NECESSARY FOR THE _________ TO PRODUCE AN ACTION POTENTIAL. The NON-NEURAL cell produces the ______
Definition
generator potential; receptor cell; action potential
Term
the _____ of the stimulus is not coded by any characteristics inherent in action potentials
Definition
modality
Term
As the intensity of a stimulus is increased, the receptor current is _______ and depolarization is produced.
Definition
increased
Term
In some receptors, the impulse-initiating zone shows little accommodation and in the face of a steady depolarization, can produce a __________
Definition
steady train of impulses
Term
Determinatnts of intensity
Definition
# of receptors involved;
pattern of discharge
Term
the range of stimulus intensities over which a receptor can respon without saturation
Definition
dynamic range
Term
the amplitude of receptor potential is proportional to the
Definition
logarithm of the stimulus intesntiy
Term
The ability of sense organs to function over a large energy range dpends on the (3)
Definition
dynamic range of initial transudction process;
adaptation with maintained exposure;
protperties of neural network that process sensory signals
Term
Where does adaptation occur?
Definition
receptor cell itself;
result of time-dependent changes in accessory tissues;
CNS
Term
continue to discharge steadily in response to a constant stimulus
Definition
tonic or static receptors
Term
receptors that significantly decrease their output for a constant input
Definition
phasic or dynamic receptors
Term
The ______ of molecules necessary for responding to a given stimulus may dimish in the face of a constant stimulus. ex. rhodopsin must be regenerated in the dark (ecxites rod and cone receptors)
Definition
quanitity of molecules
Term
actual _____ properties of receptor cell may change during stiumlation ex. Ca accumulation in cells. can also activate K channels and bring back down to RMP.
Definition
electrical properties
Term
Accessory structures may show ______ changes that alter the membrane potential of the receptor. ex. the lamella of a pacinain corpuscle turns it on an off.
Definition
time-dependent
Term
The responsivenetss of some sensory receptors is influenced by the ____ which sends impulses through efferent axons that innervate the sense organ. ex. gamma efferent fibers that supply muscle spindle modulates the sensitivity of the receptor. when they are active, the receptor is more sensitive to stimulus.
Definition
CNS (efferent control of receptor sensitivity)
Term
4 catagories of nociceptors
Definition
Mechano, mechano-heat, mechao-cold, plymodal.
Term
location of nociceptors
Definition
skin;
arterial walls;
joint surfaces;
periosteum;
peritoneum;
falx and tentorium
Term
Pain is transmitted to the CNS by the small _______ fibers at velocities of (_____) and ________ fibers that are slower.
Definition
Delta type A; 3-20 m/s; C fibers
Term
A-delta fibers are
Definition
myelinated
Term
C fibers are
Definition
unmyelinated
Term
Faster fibers (nociceptors) are called
Definition
first pain
Term
An itch is
Definition
sensed by nociceptive fibers
Term
Types of pain reception
Definition
Prickling, Burning, Aching
Term
Superficial Receptors.
A-delta size fibers
Latency is SHORT and subsides quickly
Definition
prickling pain
Term
Superficial cutaneous receptors
Unmyelinated C type fibers
Longer Latency and greater persistence
Definition
Burning Pain
Term
Receptors are in viscera, periosteum and joints.

Type C fibers

difficult to localize, may be life threatening
Definition
Deep (aching) pain
Term
Afferent activities ceoncerned with gut reflexes.
poorly localized
often referred pain.
Definition
visceral pain
Term
CNS cannot tell the difference between _____ and ____ in viscera. Pain arises from the _______. Pain fibers enter cord through ___________.
Definition
Distension & strong contractions; peritoneal linings; sympathetic routes
Term
senstation of pain
Definition
ALgesia
Term
absense of pain
Definition
ANAlgisia
Term
severe sensation or reaction to pain
Definition
HYPERALgesia
Term
Decreased senstation to pain
Definition
HYPESthesia, HYPALgesia
Term
Nociceptors are the best method of assesing the _____ system
Definition
GSA
Term
Injured tissues may release _____ that alter permability of high threshold receptors
Definition
K, hisamine, prostaglandins, bradykinen.
Term
ischemic pain
Definition
lactic acid
Term
Nonpainful mechanical manipulation of a painful site decreases the reception and/or perception of pain
Definition
counterirritation
Term
Mechanoreception using ______ fibers enhance interneurons in the spinal cord taht normally inhibit pain pathways.
Definition
Beta sized A fibers
Term
Pain impulses travel from receptors over the _______ of a spinal nerve. Stimulation of the _______ may also cause pain.
Definition
dorsal root (Redicular Pain)
Term
Radicular pain may cause
Definition
phantom pain
Term
Caused by excitation of nociceptors at one site, usally deep or vesceral, that is sensed as originating at another site, usually superficial.
Definition
referred pain
Term
The superficial region to which pain is referred is the ______ that shares teh same dorsal root as the visceral or deep afferents innervating the structure from which the pain actually originates.
Definition
dermatome
Term
The spindle is the ____ most complex receptor in the body
Definition
3rd
Term
The muscle spindle is found in all skeletal muscle, particularly _____ and those responsible for fine motor control.
Definition
antigravity muscle
Term
The spindle is a fusiform structure. it is composed of 8-10 ____ which are striated in appearance
Definition
intrafusal fibers
Term
the center of the intrafusal fiber. devoid of striations.
Definition
equatorial region
Term
striated end portions capable of contraction in intrafusal fibers.
Definition
myotube region
Term
long thick fibers that have nuclei located in a central position in a cluster
Definition
nuclear bag fibers
Term
shorter and thinner than bag fibers, with nuclei located serially in the center of the fiber
Definition
nuclear chain fiber
Term
spindle has how many bag and how many chain fibers?
Definition
2 bag, 4-5 chain
Term
Sensory (afferent) fibers supplying the spindle are type Ia and II. They supply the _____ of the intrafusal fiber
Definition
equitorial region
Term
Fibers that arise from the central portions of both types of intrafusal fibers (bag and chain) where they spiral around the central portion
Definition
Primary/ annulospiral. Ia
Term
Arise primarily from the ends of the nuclear chain fibers, with some smaller branches arising from the nuclear bag2 fibers.
Definition
secondary/ flower spray receptors (type II fibers)
Term
Primary afferents are ____ than secondary
Definition
faster
Term
receptors for the spindle have their cell bodies in the ________ of spinal nerves for those muscles supplied by spinal nerves
Definition
dorsal root ganglion
Term
The efferent (motor) supply to the intrafusal (spindle) fibers form a specailized group of fibers called the
Definition
gamma efferent fibers
Term
collective term for gamma motor fibers
Definition
fusimotor
Term
(gamma)Cell bodies for these neurons are located in the ______ of the ______ along with the cell bodies fro the LMN(Alpha)
Definition
Ventral horn of the gray matter
Term
(dynamic gamma) endings terminate on polar regions of nuclear bag1 fibers
Definition
gamma plate
Term
(statis gamma) fibers that terminate primarily on the nuclear bag2 fibers and nuclear chain fibers
Definition
gamma trail
Term
spindles are located throughout the muscle and lie _______ with the extrafusal fibers.
Definition
in parallel
Term
when the equatorial area of the intrafusal fiber is stretched, activity in the spindle afferents -_______
Definition
increases
Term
when the centerl of the intrafusal fiber is shortened afferent activity
Definition
wanes
Term
afferent activity results from an increased ______ of cell membranes to small ions, particularly ____.
Definition
conductance; sodium
Term
the center of the spindle can be streched by: strech of the ______ surrounding the spindle
Definition
extrafusal fibers
Term
center of the spindle can be streched by: contraction of the ________ By:
Definition
ends of the intrafusal fibers; impulses over the gamma efferent fibers
Term
fiber types that convey static information
Definition
Ia and II
Term
fiber type responsible for dynamic response
Definition
Ia
Term
The Ia fiber discharges rapidly during strech, but also has a ____ level of output for muscle length before and after strech.
Definition
basal
Term
Type II fiber discharges _____ for any given length, but only slowly increases its output when a muscle is streched.
Definition
tonically
Term
Ia fiber synapses directly with the
Definition
LMN
Term
____ fibers are not directly involved in the myotatic reflex, but only indirectly
Definition
gamma motor fibers
Term
Increased gamma EFFERENT discharge increases spindle _______
Definition
sensitivity
Term
Gamma efferent activity incereases the output of a _____ fiber
Definition
Ia
Term
The __CNS___ modulates the discharge level of the receptor
Definition
centrifugal control
Term
1/3 of the motor fibers in the _________ of a spinal nerve are gamma motor
Definition
ventral root
Term
gamma activity can evoke _________ contration
Definition
extrafusal fiber
Term
resistance of a muscle to _______ because a certain # of motor units are active may be referred to as _____
Definition
stretch; tone
Term
loss of input to gamma cell bodies due to injury of the spinal cord can esult in ________
Definition
immediate loss of tone (in muslces supplied by gamma fibers)
Term
the tendoncy of the spindle is to shut off during muscle contraction. this is prevented by
Definition
alpha gamma coactivation
Term
the spindle shortedns along with the muscle, and spindle discharge may continue throughout the muscle contraction. this means that...
Definition
the muscle may respond to strech, even at its new shorter length.
Term
if coactivation did not occur, the spindle...
Definition
would be constantly opposing muscle contraction.
Term
gamma activation during alpha activation may assist the
Definition
LMN and extrafusal muscle contraction.
Term
Gamma Loop:

The gamma neuron stimulates the contractile portions of the intrafusal fibers, which ______(1)________. that strech stimulates sensory fibers supplying the spindle (Ia dynamically, II in a tonic fashion). Proprioceptive impulses ___(2)___ that cause _____
Definition
1) streches the central portion of the intrafusal fibers

(2) excite LMN that cause extrafusal muscle contraction.
Term
The "loop" is
Definition
-CNS to receptor
-Receptor to CNS
-CNS to effector
Term
An injury to the spinal cord will result in an abnormal input to the spindle from the
Definition
gamma cell bodies
Term
LMN and GMN abnormality results in
Definition
clonus
Term
GTO:
Consits of the end ramifications of type ___ sensory fibers. The receptor is enclosed in a _____ and connected at either end to the connective tissue of the tendon. The terminal endings are aborize that is probably the reason they are
Definition
Ib;
capsule;
stimulated when streched.
Term
The GTO is ______ with the muscle
Definition
in series
Term
GTO functions to detect ____ during contraction
Definition
detect tension
Term
Stimulation of the Ib fibers that supply the GTO terminate in the spinal cord on inhibitory ______. Which in turn, synapse on _____
Definition
interneurons;
LMN
Term
In addition to _____ the LMN to the muscle of stimulus origin, the incoming Ib fibers ______ stimulaes LMN to _______ muscles.
Definition
inhibiting;
disynaptically;
antagonistic
Term
The end effect of the GTO excitation is to ______ in the tendon from which the signal arose.
Definition
Decrease tension
Term
The _____ as it is sometimes called, prevents excessive strech of tendons, thus regulating ____ of muscle contraction
Definition
Inverse myotatic reflex;
velocity
Term
Abnormally hperexended limb
Definition
decerebrate rigidtiy
Term
in hyperextension, the muscles are stimulating their GTOS and wehn passive strech is added to this, the GTOs finally overcome the LMN pools to extensor muscles and the limb collapses.
Definition
clasp-knife reaction.
Term
the clasp knife reaction demonstrates the _____ input to the LMN of the extensor muscles
Definition
inhibitory
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