Sensory Flashcards
Conversion of a physical signal (energy) into a neural signal
tranduction
Representing qualitative and quantitative aspects of stimulus (modality, intensity, duration, location)
encoding
conscious awareness of stimulation
perception
[Encoding] quality of a stimulus
modality
[Encoding] strength of a stimulus
intensity
[Encoding] length of stimulation
duration
[Encoding] site of stimulation
location
Basic modalities of sensation (5)
1) somatosensation (sense of body)
2) vision
3) audition
4) olfaction
5) gustation
type of energy that activates a specific receptor at lowest energy level
adequate stimulus
lowest intensity which can be detected reliably 50% of the time
sensory threshold
Relationship between threshold and sensitivity
inversely related
Slowly adapting receptors provide accurate information about…
stimulus duration
Rapidly adapting receptors provide information about…
change in stimulus intensity
Specific spatial location where stimulus energy is effective in stimulating a receptor
receptive field
Transduces physical energy (membrane deformation) into neural activity
Mechanosensitive ion channel (also called stretch-gated ion channels)
eg: pacinian, meissner, and ruffini corpuscles. Merkel discs. etc…
Cold or warm somatosensory receptor contain thermally gated ____ channels
TRP channels
Large family of ion channels gated by mechanical, chemical, osmotic or thermal stimulation. Can open Na+, K+, H+, or Ca2+ channels depending on channel subtype.
Transient Receptor Potential (TRP) channels
Cold TRP receptors are also stimulated by…
menthol
Warm TRP receptors are also stimulated by…
capsaicin
How is stimulus duration encoded?
length of the action potential train, in other words, the duration of transmitter release onto second order neuron
reduced output despite sustained stimulation
adaptation
Type of channel offering an explanation for ion conductance adaption
Ca2+-activated K+ channels
What is an encapsulated receptor surrounded by?
connective tissue capsule
Types of non encapsulated receptors / free nerve endings (4)
1) mechanical
2) thermal
3) itch
4) nociceptors (pain)
Mechanoreceptors with disk-shaped terminal of myelinated axons. Nonencapsulated receptor type
Merkel endings
Encapsulated mechanoreceptor, containing layered stack of schwann cells. Axon endings wind between the schwann cell layers. Located just under epidermis in hairless skin
Meissner corpuscle
Encapsulated subcutaneous mechanoreceptor, with single axon ending in center of capsule containing concentric layers of epithelial cells with fluid filled spaces.
Pacinian corpuscle
Encapsulated mechanoreceptor found in dermis, subcutaneous, and connective tissue. Capsule contains collagen strands with intertwined axon endings. The stretching of skin applies tension to collagen strands, squeezing axon endings.
Ruffini endings
Pacinian corpuscle – rapid or slow adapting?
Rapidly adapting receptor
Which respond to lower frequency of vibration, Meissner or Pacinian corpsucles?
Meissner
Merkel and Ruffini receptors are slow or fast adapting?
slow
True or False: Free nerve endings are rapidly adapting?
False. They can be both rapid or slow actually
Most abundant sensory receptor type in hand
Meissner corpuscles
Itch receptors can also respond to chemical stimuli, including what chemical?
histamine
Provide sensory information about muscle length
Muscle Spindles
Provide iformation about muscle tension
Golgi tendon organs
Provide pain sensory information about muscle injury or overuse
Free nerve endings
Receptor type mediating joint pain
free nerve endings
Around joints; may provide some information about join movements that cause stretching of skin
ruffini endings
Near the periosteum; provide information about bone vibration in joints
Pacinian corpuscles
most cutaneous mechanoreceptor sensory fibers. Large diameter, myelinated, and fast conduction velocities
A-beta fibers
Cutaneous sensory fibers to hair follicle receptors and some free nerve endings. Small diameter, lightly myelinated, conduct more slowly that large diameter myelinated axons.
A-delta fibers
Small diameter, unmyelinated axons of free nerve endings. Type of cutaneous sensory fiber.
C fibers
Type of pain associated with A-delta fibers
fast pain, perceived as sharp, pricking, and localized
Type of pain associated with C fibers
slow pain, perceived as aching, throbbing, and burning
Structure responsible for sensory transduction in olfactory receptor neurons
cilia. they contain g-protein coupled odorant receptors
olfactory g protein receptors stimulate which second messenger pathway?
G(olf) stimulates adenylyl cyclase -> cAMP, etc..
Similar to Ca2+ activated K+ channels, this channel family has intracellular binding sites and amplify the effect from G protein receptor pathways by bringing in sodium and calcium
Cyclic Nucleotide (cAMP or cGMP) gated channels
In olfactory sensory transduction, the increase in Ca2+ does what to cause further depolarization
stimulates Ca2+-activated Cl- channels. EFFLUX of Cl-
What causes the response to continuous odor to terminate in about 1 minute?
Ca2+ binds to calmodulin, which goes an inhibits the CNG channel (calcium activated cl- efflux channel)
Location that olfactory receptor neuron axons project to in the brain
olfactory bulb
Which two taste sensations have ionotropic receptors?
salt and sour
Which three taste sensations have metabotropic receptors?
sweet, bitter, and umami
Channel associated with salt taste transduction
Epithelial Sodium Channel (ENaC)
It’s a leak channel in which the increase in extracellular Na+ causes an influx into the cell.
Channel associated with sour taste transduction
Proton permeable TRP channel
Inward H+ flow depolarizes cell. Intracellular H+ blocks K+ channel to further depolarize.
Channel associated with sweet taste transduction
Type 1 Taste Receptor (T1R) - G-protein coupled. Stimulates phospholipase C
Channel associated with bitter taste transduction
T2R family. G-protein receptor with specific protein, gustducin
Channel associated with umami taste transduction
A different type of T1R family channel from sweet and bitter
