Lecture 22 -- NS VIII -- Sensory Organs I Flashcards
some concepts to know:
sensory receptor (definition)
any structure specialized to detect a stimulus
some concepts to know:
sense organ (definition)
structure that combines nervous tissue w/ other tissue that enhances its response to a certain type of stimulus
some concepts to know:
exteroreceptors sense stimuli ___ to the body
external
some concepts to know:
interoceptors (AKA ___) sense stimuli in the ___ organs
visceroceptors
internal
some concepts to know:
explain receptor potential
energy of stimulus is transduced into electrical response
receptor potential is a type of local potential
some concepts to know:
how does the brain distinguish stimuli intensities?
- which neurons are firing
- how many
- how fast
some concepts to know:
explain sensory adaptation
if stimulus is prolonged –> decrease neuron firing frequency –> less aware of stimulus
LO1: classify receptors according to stimulus modality
match the type of stimulus w/ sensation it produces:
thermoreceptors
heat/cold
LO1: classify receptors according to stimulus modality
match the type of stimulus w/ sensation it produces:
mechanoreceptors
physical deformation of (plasma mb) cell or tissue by:
- vibration/touch/pressure (tactile receptors)
- stretch (proprioceptors)
- tension/pressure changes in walls of blood vessels, digestive organs, bladder, lungs (baroreceptors)
LO1: classify receptors according to stimulus modality
match the type of stimulus w/ sensation it produces:
chemoreceptors
chemicals (odors, tastes, body fluid composition
LO1: classify receptors according to stimulus modality
match the type of stimulus w/ sensation it produces:
photoreceptors
light
LO1: classify receptors according to stimulus modality
match the type of stimulus w/ sensation it produces:
nociceptors
pain
tissue injury/damage
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
what are the 2 types of senses?
where are they distributed?
receptors limited to head – special senses
receptors all over body – general (somatosensory) senses
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
receptors confined to head:
5 special senses:
(1) smell
(2) taste
(3) balance
(4) hearing
(5) vision
“special” bc receptors are confined to head and have specialized structures for detection
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
receptors all over body
general (somatosensory, somesthetic) senses
“general” senses are everything else:
(1) touch
(2) pain
(3) temp
- etc.
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
general senses:
what information do they carry?
touch, pain temp
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
general senses:
how are stimuli detected?
receptive endings of sensory neurons
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
general senses:
what are signals carried by?
axons of spinal or cranial nerves
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
general senses:
what kind of electrical signal is sent?
fire action potentials
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses:
what information is carried?
taste
vision
hearing
balance
excludes smell
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses:
how are stimuli detected?
what does the stimulus do?
by sensory receptors on separate specialized sensory cell (not neurons)
stimulus triggers NT release from sensory cell
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses:
what are signals carried by?
axons of cranial nerves
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses:
what kind of electrical signal is sent?
non-neuron receptors have graded changes in membrane potential
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses – smell:
what kind of information is carried?
smell
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses – smell:
how are stimuli detected?
receptive endings of olfactory neurons in PNS
LO2: compare general senses vs. special senses considering: (a) receptor body distribution, (b) information carried, (c) structures that detect the stimulus
special senses – smell:
how are signals carried?
cranial nerves in CNS
LO3: differentiate b/n unencapsulated vs. encapsulated nerve endings
what are the two types of nerve endings on somatosensory receptors (receptors for general senses)
unencapsulated
encapsulated
LO3: differentiate b/n unencapsulated vs. encapsulated nerve endings:
unencapsulated nerve endings (definition)
dendrites w/ no connective tissue wrapping
LO3: differentiate b/n unencapsulated vs. encapsulated nerve endings:
encapsulated nerve endings (definition)
nerve fibers wrapped in glial cells or connective tissue
LO4: list the types of receptor types in each group, indicating their modalities (not location):
unencapsulated nerve ending:
3 receptor types:
free nerve endings
tactile discs (Merkel discs)
hair receptors (root hair plexus)
LO4: list the types of receptor types in each group, indicating their modalities (not location):
encapsulated nerve ending receptor types (general description)
4 major types of encapsulated mechanoreceptors
–> provide information to the CNS
–> touch, pressure, vibration, and cutaneous tension
LO4: list the types of receptor types in each group, indicating their modalities (not location):
encapsulated nerve ending:
5 receptor types:
tactile (Meissner’s) corpuscles
(Krause) end bulbs
bulbous corpuscles (Ruffini ending or Ruffini corpuscle)
lamella (Pacinian) corpuscles
muscle spindles and tendon organs (Golgi)
LO4: list the types of receptor types in each group, indicating their modalities (not location):
free nerve endings:
- unencapsulated or encapsulated nerve endings?
- modality?
unencapsulated nerve ending
pain (nociceptors)
heat (warm-R)
cold (cold-R)
LO4: list the types of receptor types in each group, indicating their modalities (not location):
tactile (Merkel) discs:
- unencapsulated or encapsulated nerve endings?
- modality?
unencapsulated
light touch (static discrimination of shapes, edges, and rough textures)
compression the skin releases serotonin
LO4: list the types of receptor types in each group, indicating their modalities (not location):
hair receptors (root hair plexus):
- unencapsulated or encapsulated nerve endings?
- modality?
unencapsulated
light touch – respond to movement of hairs
LO4: list the types of receptor types in each group, indicating their modalities (not location):
tactile (Meissner’s) corpuscles:
- unencapsulated or encapsulated nerve endings?
- structure?
- modality?
encapsulated
fluid-filled capsule of Schwann cells
indentation and slipping of objects (low-frequency vibrations)
muscle spindles and tendon organs (golgi)
LO4: list the types of receptor types in each group, indicating their modalities (not location):
(Krause) end bulbs:
- unencapsulated or encapsulated nerve endings?
- modality?
encapsulated
temperature
touch
LO4: list the types of receptor types in each group, indicating their modalities (not location):
bulbous corpuscles (Ruffini ending or Ruffini corpuscle):
- unencapsulated or encapsulated nerve endings?
- modality?
encapsulated
stretch
heavy continuous touch/pressure – shapes perception
LO4: list the types of receptor types in each group, indicating their modalities (not location):
lamellar (Pacinian) corpuscles:
- unencapsulated or encapsulated nerve endings?
- structure?
- modality?
encapsulated
1 dendrite
multiple concentric cell layers
vibration
LO4: list the types of receptor types in each group, indicating their modalities (not location):
muscle spindles and tendon organs (Golgi):
- unencapsulated or encapsulated nerve endings?
encapsulated
LO5: compare the 3 types of pain
define pain
characteristics of pain…
uncomfortable conscious perception of tissue injury or noxious stimulation
subjective, highly variable, influenced by mental state
LO5: compare the 3 types of pain
what are the 3 types of pain?
nociceptive vs neuropathic vs. nociplastic
LO5: compare the 3 types of pain
define nociceptive pain
pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors
LO5: compare the 3 types of pain
what are the 2 types of nociceptive pain?
visceral pain
somatic pain
LO5: compare the 3 types of pain
where does nociceptive pain come from?
stems from tissue injury (cuts, burns, chemical irritation) – tissue inflammation
LO5: compare the 3 types of pain
examples of visceral nociceptive pain
mucosal injury – peptic ulcer
ischemia – angina
obstruction or capsular distension – kidney stones
LO5: compare the 3 types of pain
what are the 2 types of somatic pain?
deep vs. superficial
LO5: compare the 3 types of pain
what body parts are affected by deep somatic nociceptive pain?
what is an example?
bones
joints
muscles
osteoarthritis
LO5: compare the 3 types of pain
what body parts are affected by superficial somatic nociceptive pain?
what is an example?
skin
LO5: compare the 3 types of pain
define neuropathic pain and its characteristic sensations
pain caused by a lesion or disease of the somatosensory nervous system
burning, tingling, or “electrical” sensations
LO5: compare the 3 types of pain
give examples of neuropathic pain:
ischemia
stroke
postherpetic neuralgia
multiple sclerosis
spinal cord injury (trauma)
LO5: compare the 3 types of pain
describe neuropathic pain caused by ischemia:
peripheral vascular disease, diabetes
circulation disorder
most common is artherosclerosis (build up of plaque inside artery wall)
causes:
- narrowing, blockage, or spasms in blood vessel
LO5: compare the 3 types of pain
describe neuropathic pain caused by stroke:
(brain attack) –> blood flow to the brain is stopped
LO5: compare the 3 types of pain
describe neuropathic pain caused by postherpetic neuralgia:
lasting pain in areas of skin where you had shingles –> caused by chickenpox
LO5: compare the 3 types of pain
describe neuropathic pain caused by multiple sclerosis:
immune system attacks myeline nerve sheathing in brain and spinal cord
LO5: compare the 3 types of pain
what kind of pain is caused by trauma to spinal cord?
neuropathic
LO5: compare the 3 types of pain
define nociplastic pain
what are some symptoms?
pain from altered nociception even though there is no clear evidence of tissue damage causing the activation of peripheral nociceptors or evidence of damage to somatosensory systems
symptoms:
- multifocal pain and other CNS-associated symptoms
LO5: compare the 3 types of pain
what are 2 examples of nociplastic pain?
fibromyalgia
irritable bowel syndrome
LO5: compare the 3 types of pain
describe fibromyalgia
a type of nociplastic pain
causes widespread pain, sleep problems, fatigue, and often emotional and mental distress. Patients might have abnormal pain perception processing (increased sensitivity to pain)
(diffuse sensitization)
LO5: compare the 3 types of pain
describe irritable bowel syndrome
a type of nociplastic pain
abdominal discomfort associated w/ altered bowel movements. Many symptoms are related to hypersensitivity of the nerves found in wall of GI tract
(functional visceral pain)
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what do endogenous molecules do?
contribute to the transmission of pain and make the nociceptors more sensitive
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
define inflammation
during an injury, damaged cells release their contents into extracellular space
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
list the endogenous molecules that produce pain in PNS and CNS
(1) histamin, NGF
(2) bradykinin
(3) serotonin (5-HT)
(4) prostaglandin
(5) H+
(6) edema
(7) substance P and CGRP
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what is bradykinin?
an endogenous molecule
released during inflammation
one of the most powerful pain-causing agents
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what is prostaglandin and how does it work?
an endogenous molecule
released during inflammation
sensitizes the nociceptors to the substances generated by the injury
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what does H+ do?
an endogenous molecule
released during inflammation
activates ion channels in certain nociceptors directly
responsible for muscle pains associated w/ production of ATP under anaerobic conditions, which generates lactic acid
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what is an edema?
vasodilation of local capillaries
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
describe “axon reflex”
nociceptors at site of tissue injury release substance P and calcitonin gene-related peptides (CGRP)
further Vd, bradykinin, histamine, 5-HT release
LO6: list the endogenous molecules that produce pain in the PNS and CNS:
what are the efferent and afferent endogenous molecules?
efferent – opiates
afferent – substance P, glutamate
LO7: describe the 3 families of endogenous opioid peptides: name, main receptor, and function:
3 distinct families of peptides are…
enkephalins
endorphins
dynorphins
LO7: describe the 3 families of endogenous opioid peptides: name, main receptor, and function:
enkephalins (main receptor, function)
delta receptor
involved in nociception – attenuate substance P release in the dorsal form of the spinal cord and inhibit afferent pain fibers
LO7: describe the 3 families of endogenous opioid peptides: name, main receptor, and function:
endorphins (main receptor, function)
mu receptor
produced by hypothalamus and pituitary gland
produce analgesia and well-being
LO7: describe the 3 families of endogenous opioid peptides: name, main receptor, and function:
dynorphins (main receptor, function)
kappa receptor
involved in pain, addiction, and mood regulation
LO8: explain what causes referred pain
define referred pain
activation of nociceptors in viscera results in perception of pain on body surface
LO8: explain what causes referred pain
define referred pain
activation of nociceptors in viscera results in perception of pain on body surface
LO8: explain what causes referred pain
referred pain results from…
convergence of neural pathways in CNS
LO8: explain what causes referred pain
explain cardiac pain referral mechanism:
(1) heart attack –> pain signals
(2) spinal cord segments T1-T5 receive input from heart, chest, and arm. Pain fibers converge and follow the same pathway.
(3) brain can’t distinguish which source the arriving signals are coming from
(4) patient perceives diffuse pain in T1-4 dermatomes
LO9: what are taste buds and where are they found?
taste buds are the true…
taste organ
LO9: what are taste buds and where are they found?
describe filiform papillae
scale-like projections that cover tongue’s surface
sense pressure
LO9: what are taste buds and where are they found?
describe fungiform papillae
round areas that contain taste buds
LO9: what are taste buds and where are they found?
describe vallate papillae
V-shaped
LO9: what are taste buds and where are they found?
define papilla
wart-like bumps on the mucous membrane of the tongue
LO9: what are taste buds and where are they found?
describe taste buds
contain gustatory receptor cells (taste cells)
contain taste pores and microvilli (hair)
LO11: explain how taste receptors and associated sensory nerve fibers are stimulated
define tastants
chemical stimuli
LO10: describe the structure of a taste bud
basal cell – stem cells
supporting cells
axons of sensory neurons
taste hairs
gustatory receptor cells (taste cells), half life = 7-10 days
taste pores
LO11: explain how taste receptors and associated sensory nerve fibers are stimulated
which tastants are recepted by ligand-gated ion channels?
salt – metal ions Na+ and K+
sour – associated w/ acids
LO11: explain how taste receptors and associated sensory nerve fibers are stimulated
which tastants are recepted by G protein-coupled receptors? (GPCR)
sweet – carbs
bitter – spoiled foods and alkaloids
umami – “meaty” – aspartic and glutamic acids
LO11: explain how taste receptors and associated sensory nerve fibers are stimulated
how are the taste sensory neurons of stimulated
neurotransmitters release after tastants are recepted
LO11: explain how taste receptors and associated sensory nerve fibers are stimulated
each taste cell has receptors for ___ type of taste, but a taste bud is typically composed of ___ cells detecting different tastes
only 1
several
LO12: describe the gustatory projection pathways
which cranial nerves are involved in gustatory projection?
mixed cranial nerves: 5, 7, 9, 10
5: trigeminal
7: facial
9: glossopharyngeal nerve
10: vagus
LO12: describe the gustatory projection pathways
list the steps of the gustatory projection pathways
(1) gustatory info is relayed from tongue (taste buds) via cranial nerves to nucleus of solitary tract (NTS)
(2) NTs relays signals to:
(a) nuclei in hypothalamus and amygdala –> activate autonomic reflexes (salivation, gagging, vomiting) and emotions and memory associated w/ taste
(b) thalamus –> gustatory cortex (insula) and orbitofrontal cortex
(3) in orbitofrontal cortex – taste signals are integrated w/ signals from nose and eyes – overall impression of food flavor and palatability
LO13: describe the olfactory mucosa: definition, localization, and composition
define olfaction
a response to airborne chemicals called odorants
LO13: describe the olfactory mucosa: definition, localization, and composition
how are odorants detected?
by receptor cells in olfactory mucosa
LO13: describe the olfactory mucosa: definition, localization, and composition
define olfactory mucosa
patch of epithelium in the roof of the nasal cavity
LO13: describe the olfactory mucosa: definition, localization, and composition
what are the components of the olfactory mucosa?
cilia: olfactory hairs
supporting cells – provide metabolic and structural support
olfactory receptor cell – neurons (half life of 60 days
basal cell – stem cells, replace olfactory receptor cells
LO13: describe the olfactory mucosa: definition, localization, and composition
what are the components of the olfactory mucosa?
cilia: olfactory hairs
supporting cells – provide metabolic and structural support
olfactory receptor cell – neurons (half life of 60 days
basal cell – stem cells, replace olfactory receptor cell
LO13: describe the olfactory mucosa: definition, localization, and composition
olfactory nerve fiber axons are arranged in ___
collectively, the fascicles are regarded as the ___
fascicles
olfactory nerve (CN I)
LO14: discuss the steps for olfactory sensory transduction
list the 4 steps:
(1)
hydrophilic odorants diffuse freely and bind directly to a receptor (GPCR)
hydrophobic odorants are transported by an odorant-binding protein
(2) a receptor-odorant complex is formed – activates (thru G protein) adenylate cyclase (an enzyme) –> converts ATP to cAMP (2nd messenger)
(3) cAMP opens Na+ channels in plasma mb of cilia –> depolarizes –> creates receptor potential
(4) depolarization is conducted to axon hillock of olfactory sensory neuron –> AP is generated –> signal transmitted to brain
LO15: describe the olfactory projection pathways
olfactory tracts – how are they formed? what is their function?
formed from bundles of axons of tufted and mitral cells
carry out olfactory info to brain structures
LO15: describe the olfactory projection pathways
explain difference b/n tract and nerve and which NS they’re found in
nerve = collection of nerve fibers in CNS
tract = collection of nerve fibers in PNS
LO15: describe the olfactory projection pathways
olfactory nerve (CN 1): what is it composed of?
many small olfactory nerve fascicles
LO15: describe the olfactory projection pathways
what is a glomerulus in olfactory bulb?
spherical structure where synapses form b/n terminals of olfactory fibers and dendrites of mitral and tufted cells
LO15: describe the olfactory projection pathways
explain how receptor cells and mitral and tufted cells synapse to form glomerulus
receptor cells expressing the same receptor project their axons to the same discrete glomeruli w/in the olfactory bulb
receptor cells synapse w/ dendrites of mitral and tufted cells to form the glomerulus
LO15: describe the olfactory projection pathways
what kind of cells are tufted and mitral cells?
neurons
LO15: describe the olfactory projection pathways
how many types of odors does each glomerulus detect?
1
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
where is the primary olfactory cortex located?
describe its structure.
how does it receive input?
what does it do
located in temporal lobe
not a single structure
receives input directly from olfactory bulb
creates conscious perception of odor and relays signals to other brain destinations
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
list parts of the primary olfactory cortex and their functions
piriform cortex – “pear” shape – travels to OFC and thalamus
amygdala – emotional responses
entorhinal cortex – travels to hippocampus
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
what are the primary parts of the secondary olfactory cortex?
where is the secondary olfactory cortex located?
what does it do?
orbitofrontal cortex (OFC) and insula
OFC:
- located in the prefrontal cortex above the eyes
- identifies and discriminates among odors
- integrates odors, taste, and vision
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
what does the hippocampus have to do with olfaction?
olfactory memory
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
where are signals from temporal lobes relayed?
signals from each temporal lobe are relayed to contralateral temporal lobe, so all processing is mirrored in both cerebral hemispheres
LO16: indicate the brain regions where the olfactory signals are processed and integrated w/ other sensory input
where is odor info sent?
what kind of response does it trigger?
what is the response involved in?
odor info is sent to hypothalamus and brainstem
triggers autonomic responses
involved in appetite, salivation, and gastric contraction
LO17: which cells mediate cortical feedback modulation for the olfactory bulb circuit? How?
granule cells (interneurons)
olfactory cortex sends fibers back to olfactory bulbs to synapse onto the inhibitory (GABAergic) granule cells (interneurons)
granule cells can inhibit the mitral and tufted cells
what are the principal relays of olfactory info from bulb to brain?
mitral and tufted cells
LO17: which cells mediate cortical feedback modulation for the olfactory bulb circuit? How?
what is the result of cortical feedback modulation of olfactory bulb circuit?
granule cells (interneurons) are inhibitory –>
odors can change in quality and significance under different conditions
what are olfactory receptor cells?
neurons that contain hair-like cilia containing specialized receptor-proteins that recognize odor molecules
what is the olfactory bulb?
relay station of the olfactory pathway and contains olfactory glomeruli
what is the olfactory cortex?
piriform cortex, amygdala, entorhinal cortex
what is the olfactory tract?
made up of axons of mitral and tufted neurons
what is the olfactory nerve?
CN I formed out of a collection of olfactory receptor cell axons, which pass thru the crifbriform plate and into the roof of the nasal cavity
