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319 Cards in this Set

  • Front
  • Back
How many parts to somatic sensory system?
2
What are the parts to the somatic sensory system?
-Touch
-Pain and Temperature
Receptors for touch somatic sensory system?
Mechanoreceptors
Mechanoreceptors receptors?
Skin
Mechanoreceptors cell bodies?
Dorsal Root Ganglion
Mechanoreceptors primary afferent axons?
Skin -> spinal nerves -> spinal cord
Where do mechanoreceptors ascend?
Ipsilateral side of the dorsal columns in the white matter
What does afferent mean?
Carries information into CNS
What does efferent mean?
Carries information out of the CNS
Primary afferent axons for mechanoreceptors?
A-beta
What are the italian mechanoreceptors of the skin?
Pacinian Corpuscle and Ruffini's Endings
What are the german mechanoreceptors of the skin?
Meissner's Corpuscle and Merkel's Disk
Size of Pacinian Corpuscle receptor?
largest
Percentage of hand is Pacinian Corpuscle?
10-15%
Spacial acuity of Pacinian Corpuscle?
Low 10+nm
Point of Pacinian Corpuscle?
Detected transmitted vibrations (tool use)
Size of Ruffini's Endings?
Second largest
Percentage of hand is Ruffini's Endings?
20%
Spacial acuity of Ruffini's Endings?
Low spacial acuity (7mm)
Point of Ruffini's Endings?
Gives information on hand and finger position
Pacinian Corpuscle is sensitive to what?
High frequency vibration
Ruffini's Endings are sensitive to what?
skin stretch from finger movement
Size of Meissner's Corpuscle?
1/10th the size of Pacinian Corpuscle
Percentage of Meissner's Corpuscle on the hand?
40%
Meissner's Corpuscle is sensitive to what?
Low vibrations such as texture on the skin
Spacial acuity of Meissner's Corpuscle?
Intermediate. 3 mm
Point of Meissner's Corpuscle?
Detect motion and grip control
Size of Merkel's Disk?
Smallest receptor
Percentage of Merkel's Disk on hand?
25% (predominantly on finger tips)
Merkel's Disk is sensitive to what?
Edges, points and curvatures
Spacial acuity of Merkel's Disk?
High. (.5 mm)
Point of Merkel's Disk?
Detect form and texture
What is a receptive field?
Area of skin that changes AP fire rate when stimulated
What is a rapid adaptation receptive field?
Detects change, but stops firing AP once change has become constant
What is a slow adaptation receptive field?
Detects change and keeps firing in response to change even if change has become constant
What is a small receptive field size and rapid adapting mechanoreceptor?
Meissner's Corpuscle
What is a large receptive field size and rapid adapting mechanoreceptor?
Pacinian Corpuscle
What is a small receptive field size and slow adapting mechanoreceptor?
Merkel's Disk
What is a large receptive field size and slow adapting mechanoreceptor?
Ruffini's Ending
What does a corpuscle do for a mechanoreceptor?
Makes it sensitive to high frequency vibration, but not to constant pressure
8 Spinal segments?
Cervical
12 spinal segments?
Thoracic
5 spinal segments?
Lumbar and Sacral
What is a dermatome?
Skin innervated on the right and left dorsal roots for a single spinal segment?
Why do you need to cut 3 adjacent dorsal roots to remove feeling to dermatome?
Because adjacent dorsal roots can overlap
What is the Dorsal column-medial lemniscal pathway?
Body receptors to the cortex
What are the first order neurons for Body receptors to cortex?
A-beta axons
Where do A-beta axons enter?
Through dorsal roots
How and where do the A-beta axons get to the brain?
They ascend through the ipsilateral dorsal column
What is the topographic division for dorsal columns in body receptors to cortex? (They are tracts)
Lower Body: Gracile Tract
Upper Body: Cuneate Tract
Where do the axons synapse onto the second order neurons in body receptors to cortex pathway?
At the Second Order Neurons in the dorsal column nuclei
Where do the lower body axons synapse?
Gracile Nucleus
Where do the upper body axons synapse?
Cuneate Nucleus
The part of the Second Order Neurons that cross over in the body receptors to cortex pathway is called what?
Internal Arcuate Fibers
What guides second order axons up the dorsal column in BR to Cortex?
Medial Lemniscus
What part of the brain does the medial lemniscus guide the second order neurons through for BR-Cortex pathway?
Medulla, Pons and midbrain
Where do 2nd Order Neurons synapse onto in BR-C pathway?
Ventral Posterior (VP) Nucleus of the Thalamus
What do the 3rd Order Neurons do?
Project to the Primary Somatosensory Cortex (S1)
Cell bodies for mechanoreceptors of the face?
Trigeminal ganglion
Primary Afferent Axons for BR of Face?
Skin to Trigeminal nerve to ganglion
How do BR face mechanoreceptors enter the Pons?
Through Trigeminal Nerve
Another name for trigeminal nerve?
Cranial Nerve V
Where are first order cell bodies in BRf-C?
Trigeminal Ganglion
Where does the second order synapse occur in BRf-C?
On the ipsilateral trigeminal nucleus
What is the structure called when Second order neurons crossover in BRf-C?
Trigeminal lemniscus
What side of dorsal column does lemniscus ascend in BRf-C? And to where?
the contralateral. The thalamus
Where do second order axons synapse in BRf-C?
Ventral Posterior Medial (VPM) Nucleus of the Thalamus
Where do VPM Neurons project to? And what order are these neurons?
Project to primary somatosensory cortex (S1). Third order
What is the primary somatosensory cortex called in Brodmann's terms?
S1 = 3b
What is the postcentral gyrus?
3a, 1, 2
What are posterior parietal cortex made of?
5 and 7
Where is texture felt?
3b->1
Where is size and shape perceived?
3b-2
How many layers does a human cortex have?
3-6
What is special about the human cortex and its organization?
Alternates between rapidly and slowly adapting
Which layer to thalamic inputs synapse on the S1?
Layer IV.
What is somatotropy?
Sensations of the body mapped onto brain
What does somatotropy show us?
Cortex devotes more space to body parts of more importance
What is pain?
Perception of unpleasant things
Does pain require activation of nociceptors?
No
Is pain subjective? And How?
Yes. Each person has a different amount of pain they can take
What is nociception?
Activation of nociceptors and related neural pathways
Does activation of nociception lead to perception of pain?
Not necessarily
What is part of the somatosensory system for pain?
Nociceptors
Nociceptors of the skin?
Free Nerve Endings of A-Gamma and unmyelinated C Fibers
What is the relation between nociceptors and thermoceptors?
They are not the same
How are nociceptors and thermoceptors different in response to stimulus (2 parts)?
Thermoceptors do not increase fire rate as stimulus increases. Nociceptors only start firing when stimulus becomes noxious
Unique aspect of free nerve endings?
Polymodal. (multiple stimuli)
Type of stimuli for nociceptors (3 of them)?
Mechanical: Strong Pressure
Thermal: Burning Heat (>42 C) and Extreme Cold (<17 C)
Chemical: histamine, protons
What is characteristic of A-gamma C Axons?
Smallest diameter, lowest conductance
What does A-Gamma axons typically sense?
Pain, temperature
What does C-axons typically sense?
Temperature, pain, itch
What causes the activation of nociceptors?
When tissue breaks, chemicals are released that activate nociceptors
What are substances that activate nociceptors?
Bradykinin, ATP, and Potassium
How does Bradykinin activate nociceptor?
Depolarization through G-protein coupled reactions
How does ATP activate nociceptors?
Activates P2X receptors
How does Potassim activate nociceptors?
Depolarizes them
What is Hyperglasia?
Increased sensitivity at injury, injury site and surrounding area in pain
What is sensitization?
Increased activity and sensitivity in nociceptors b/c of tissue damage
How are nociceptors sensitivized?
Tissue damage releases chemicals
Chemicals that are part of sensitivation of nocicpetors?
Bradykinin, Prostaglandins, Substance P
How does Bradykinin increase sensitivity in nociceptors?
Increase sensitivity in ion channels like TRPV1
How is Prostaglandins made? What can inhibit these?
By enzyme released from damaged cells called cyclooxygenase. Aspirin and other NSAIDs
How does Substance P increases sensitivity in nociceptors?
Swelling of capilaries (vasodilation), releases histamine (activates mast cells)
What is responsible for first pain?
A-Gamma Axons
What is responsible for second pain?
C-axons
Receptors for the nociceptors of the body?
skin
Cell bodies for nociceptors?
dorsal root ganglion
Primary afferent axons for nociceptors?
skin -> spinal nerves (dorsal root) ->spinal cord
How is information sent up and down spinal segments in nociceptor pathway?
Lissauer's Tract
Where is 2nd Order Neuron for nociceptors?
Substantia Gelatinosa
Where is Substantia Gelatinosa located in spinal cord?
Dorsal horn
First order neurons in Spinothalamic pathway?
A-Gamma and C-axons
Where do neurons cross-over in spinothalamic pathway?
Right after 2nd Order Neuron synapse
Where does 3rd Order Neuron synapse at in spinothalamic pathway?
Ventral Posterior Lateral (VPL) Nucelus of the thalaum and intralaminar nuclei
Where does 3rd order Neurons project?
Primary somatosensory cortex (S1)
What is the structure that brings the 2nd order neurons to the third order neurons in the spinothalamic pathway called?
Spinothalamic tract
Primary Axons in Trigeminal Nociceptors?
A-gamma and C-axons
Where are the cell bodies found for Noc.Trig pathway primary neurons?
Trigeminal Ganglion
Where does the primary neurons travel first in the Noc.Trig pathway?
Down first. From Pons to Caudal Medulla
How does the primary neurons travel first in the Noc.Trig pathway?
By Spinal trigeminal Tract
Where is the synapse for Noc.Trig. pathway 2nd Order Neurons?
In the Spinal Trigeminal Nucleus of the Caudal medulla
What is structure called that is involved with the 2nd order neurons cross over in Noc.Tri. Pathway?
Trigeminothalamic Tract or Trigeminal Lemniscus
Where is 3rd Order Neurons in Noc.Tri. Pathway?
Ventral Posterior Medial (VPM) nucleus of Thalamus
Where do 3rd Order Neurons project to?
Primary somatosensory cortex (S1)
What can influence activity of the PAG?
Emotional State
Where is PAG located?
Midbrain
What does PAG stand for?
Periacqueductal Gray
What process is PAG involved in?
Descending Pain Pathways
Where does PAG synapse at?
Serotonic Neurons in Raphe Nuclei of Medulla
Relation between nociceptor and mechanosensory neuron with second order projection neuron?
Can both excite some second order projection neurons
What type of fiber excites the inhibitory interneuron?
A-Beta fiber
C-fiber and A-gamma axons inhibit the inhibitory interneuron which means...?
The Second order projection neuron is excited
A-beta axon excites inhibitory inteneuron, which means...?
The second order projection neuron is inhibited
When the gate is closed and no sensory information, what is happening?
Inhibitory interneuron is being excited by A-beta so it inhibits second order projection neuron
When the gate is closed and touch alone is sensed, what is happening?
Mecahnosensory (A-beta) is exciting the interneuron, inhibiting the 2nd order neuron
When the gate is closed and pain and touch is experienced, what is happening?
Mechanosensory neuron blocks the excitatory effects of nociceptor neuron on 2nd order projection neuron
What is happening when the gate is open?
Only pain. Nociceptive neuron maximally excites projection neuron by inhibiting interneuron
What is referred pain?
Pain perceived at a site that isn't a painful stimulus
What is visceral pain?
Pain perceived in the organs
What is cutaneous pain?
Sensation of pain arising from the skin
Job of the thermoreceptor?
Nonnoxious (nonpainful) temperature sensations
Heat TRP channels (2)?
TRPV3, TRPV4
Cold TRP channels (1)?
TRPM8
Noxious (nociception) heat TRP channels (2)?
TRPV1, TRPV2
Noxious (nociception) cold TRP channels (1)?
TRPA1
Pathway for thermoreceptors?
Nearly identical to the pain pathway
What are cold receptors coupled with?
A-gamma and C Fibers
What are warm receptors coupled with?
C fibers
What is Dorsal column-medial lemniscal pathway also called?
Mechanosensory pathway/Touch pathway
What does a bitter taste indicate?
Potentially poisonous food
What does a Sweet taste indicate?
Calorie-Rich Food
What does a Salty taste indicate?
Electrolytes
What does a sour taste indicate?
Possibly spoiled/unripe food
What does a umami taste indicate?
"delicious flavor" (savory): Amino Acids
4 structures involved with taste?
Tongue, Pharynx, Epiglottis, Palate
Where is the papillae found?
On the taste structures
What is a single papilla made of?
Taste buds
What is a single taste bud made of?
Many taste receptor cells
What is the taste receptor cell? (Its type)
Sensory cell
Type of Papillae in the back part of the tongue?
Vallate or Circumvallate
Type of papillae in the anterior 2/3rds of the tongue?
Fungiform
Type of papillae the posterior lateral edge?
Foliate
How many taste buds does Fungiform papillae have?
Few
How many taste buds does vallate papillae have?
250
How many taste buds does foliate papillae have?
12-600
How many taste receptor cells does each taste bud have?
50-150
What type of cell is the TRC and what is its polarity?
Non-neuronal, Polar
What is a microvilli? Where is it found?
Things that project into the taste pore. Found on the apical surface of taste receptor cell
Life span of taste receptor cell?
2 weeks
What is a tastant?
Disolved ion or molecule that stimulates taste receptor proteins
Where doe we experience taste on our tongue?
Each taste has the same range of perceptibility
What is transduction?
When a stimulus from the environment causes an electrical response in a sensory receptor cell
What starts transduction for taste?
Tastant
What starts AP for taste?
When gustatory axons receive neurotransmitter emitted by TRC
G-protein combination for Sweet tastes?
T1R2+T1R3
G-protein combination for umami tastes?
T1R1+T1R3
How many types of G-protein bitter receptors are there?
30
How does tastant (Na) for salt enter the TRC?
Through amiloride-sensitive sodium channels
How does tastant (H+) for sour enter the TRC?
H+ regulates some type of cation channel (Opens TRPP or closes K+)
Difference between Amiloride-Sensitive Na Channels and Na voltage gated channels (3)?
-not voltage gated
-open at rest
-blocked by amiloride
Name of g protein in transduction of bitter, sweet and umami?
gustducin
What activates TRP channel in bitter, sweet, umami transduction?
IP3
What is the TRP channel in bitter, sweet, umami transduction?
TRPM5
What is the specific type of bitter TRC called?
T2R
Labeled line theory of TRC?
Each TRC responds to a single receptor type
Across-Fiber theory?
Each TRC can respond to more than one type of taste
Multimodal Across-Fiber theory?
Each TRC has many receptor types
1 Kind of TRC to any nerve for across fiber theory?
Each TRC only codes for taste type, but the axons sending the information can be responding to more than 1 TRC at a time
H+ typical tastant for what kind?
Sour
Na+ typical tastant for what kind?
Salt
Quinine typical tastant for what kind?
Bitter
Glucose typical tastant for what kind?
Sweet
Glutamate typical tastant for what kind?
Umami
What carries taste signal?
Cranial nerves VII, IX, X
Where does cranial nerves XII, IX, X synapse onto for taste? And where?
Gustatory Nucleus in the medulla
Where does gustatory nucleus axons synapse onto for taste? and what?
Ventral posterior medial (VPM) nucleus of the thalamus in the thalamus
Where does VPM neurons project to?
Gustatory and frontal cortex
Where are the majority of olfactory pathways?
Olfactory bulb
Organ of smell?
Olfactory Epithelium
Name of specific receptor of odorants?
Olfactory Receptor Neuron
Life span of ORN?
4-8 weeks
Type of cell is ORN?
Neuronal
What do supporting cells do in olfactory system (2)?
Detoxify toxins in mucus and contribute to mucus
Point of basal cells in Olfactory system?
Produce new ORN
Point of Bowman's Gland?
Produce mucus
How many axons and dendrites per ORN?
1
What is on the end of the dendrite of the ORN?
A know with Cilia that protrude out
What structure does ORN neurons leave the Olfactory Epithelium in? And in what nature?
Axons leave through openings called Cribiforms in clusters
What is the cranial nerve for olfactory system? What is unique about it?
Cranial Nerve 1. There isn't a single Cranial nerve, but collectively, all the axons make up this nerve
Where does odorant detection occur?
In the cilia
Specific G-protein for Olfactory system?
G_olf
What does G_olf activate?
Adenylyl cyclase
What does Adenylyl cyclase synthesize (Olfactory)?
cAMP
What does cAMP then do (olf.)?
Bind to Cyclic Nucleotide (CNG) Channels
Binding to CNG Channels does what (olf.)?
Influx of Na^+ and Ca^2+
What does the Ca^2+ do (olf.)?
Binds to Ca^2+ activated Cl^- channels
Activation of Cl^- channels does what (olf.)?
Membrane depolarization
Where does the membrane depolarization first occur in the olfactory system?
Cilia. (NOT Dendrite, AP propagates there)
What is an odorant?
Airborne chemical stimulus
What is the g-protein coupled receptor odorant structure like?
Has 7 membrane-spanning domains
Where does odorant bind in relation to the cell?
Extracellular domains
Where is the g-protein interaction occurring?
Intracellular C-terminal
How many odorant types do most ORNs express?
1
How many ORNs can one odorant activate?
many
How does brain encode what kind of smell it is experiencing if there many ORNs can be activated by one odorant?
Through population coding. A certain odorant will create a certain response across ORNs that is unique to that odorant
Where is the second order neuron located (olf.)?
Olfactory bulb
What are the second order neurons called (olf.)?
Mitral cells
Where do ORNs synapes onto Mitral cells?
Glomerulus
Mitral cells form a bundle called what?
Lateral Olfactory Tract
What does the Lateral Olfactory Tract do?
Project to several brain structures
What does 3rd order projection neurons go to (olf.)?
Olfactory Cortex
What does 4th order projection neurons go to (olf.)?
Orbitofrontal Cortex
Where does 3rd order neuron synapse onto 4th order (olf.)?
In the Medial Dorsal Nucleus in the Thalamus
Where does the 2nd order neuron synapse onto the 3rd order (olf.)?
Olfactory tubercle
How many Glomeruli are there per olfactory bulb?
2000
How many ORNs go to one Glomeruli?
About 25,000
How many Mitral cells do Glomeruli converge onto?
25
Where do all ORNs expressing as type of odorant synapse to?
the same glomerulus
Two ways to map Olfaction encoding?
Temporal and with a map
What is ansomia?
Inability to detect a common odor
What can affect ansomia (3)?
Genetic defect, injury and age
Can humans scent-track?
Yes
Can humans improve smell with practice?
yes
Is sniffing behavior involved?
yes
Does each nostril provide distinct information?
yes
Do humans use inter-nostril information?
yes
What is a pheromone?
Chemicals released by a organism that affects another organism in the same species' behavior or physiology
What is the point of the Vomeronasal Organ do in relation with pheromones?
Involved in mating behavior
What is the point of the Grueneberg Ganglion in relation to pheromones?
Fear response
2 types of specialized coupled g-protein receptors in Vomeronasal Organs?
V1Rs and V2Rs
Main type of specialized coupled g-protein receptors in Grueneberg Ganglion?
V2Rs
Do human adults have a Vomeronasal Organ? If not, do we ever?
No. Only when we are embryos
What could play role of Vomeronasal Organ in humans? Why?
Olfactory Epithelium. There are two functional pheromone receptor genes (V1R-type) found there
Possible pheromones in humans (3)?
Menstrual cycles, sweat and affects on opposite sex, what estrogen/testosterone does on opposite sex's brain activity
What nerves are used in the Vestibulo-Occular reflex?
3, 4, and 6
What part of the ear is the vestibular labyrinth a apart of?
The inner ear
What does the vestibular labyrinth do?
Maintains balance
What does the cochlea do?
Hearing
What is endolymph?
A fluid with high conc. of K^+ and low Na^+, like cytoplasm
What structures make up the vestibular labyrinth (2)?
Otolith Organs and Semicircular Canals
How many otolith organs per vestibular labyrinth?
2
How many semi-circular canals per vestibular labyrinth?
3
what is the longest cillium on a hair cell called?
Kinocilium
How is the vestibular epithelium special in terms of charge?
It has a polarized orientation
How is depolarization caused within the Vestibular Labyrinth structures?
Deflection towards the kinocillium.
Function of the otolith organs?
Detect head tilt and linear accelerations
What is the sensory epithelium called in the Otolith Organ?
Macula
what is a utricle?
A macula orientated parallel to the ground (The kinocilia are then perpendicular to the ground)
Where is the utricle connected?
To the semi-circular canals
What kind of motion is the utricle sensitive to?
Movement along the horizontal plane
What is a saccule?
macula orientated perpendicular to the ground (The kinocilia is then parallel to the ground)
What is the saccule connected to?
the cochlea
What kind of motion is the saccule sensitive to?
sensitive to gravity and vertical fall
Semicircular Canal function?
Detect angular accelerations
Sensory epithelium in the semicircular canals?
crista
How many canals are found in the semicircular canal?
3
What is the name of the three canals within the semicircular canal?
-Superior
-Posterior
-Horizontal or lateral
What is the structure called that the semicircular canal meets up with the utricle?
Ampulla
What does the ampulla do?
Houses the crista and the gelatinous structure called capula and hair bundle
How many ampullas per semicircular canal?
1
What is a hair bundle (vest.)?
cilia of hair cells
How are kinocilia arranged in the macula?
In different directions
How are the kinocilia arranged in the crista?
same direction
How to hyperpolarize a cell (vestib.)?
deflect the hair cell in which the kinocilia is the last cilium
How to depolarize a cell (vestib.)?
deflect the hair cell in which the kionocilia is the first cilium
What kind of channels are activated when the kinocilia is deflected forward?
Stretch-activated channels
When the stretch activated channels are activated, what ion do they allow into the cell?
Ca^2+
What does the influx of Ca^2+ do (vestib.)?
Open voltage gated Ca^2+ channels
With the opening of voltage gated Ca^2+ channels, what happens?
Neurotransmitter is released
Two parts to the structure of the macula are?
-Gelatinous cap
-otolithic membrane
What is the otolithic membrane?
membrane embedded with otoliths (ear stones)
What is the point of the macula with relation to head movement?
To cause the cilia to bend with gravity due to the pressure the gelatinous cap and otolithic membrane applies
How does hair cell bend in the crista?
When head moves, endolymph fluid follows, but the cupula lags behind in opposite direction of head rotation
What does the graph of the right and left semicircular AP look like when the head is rotated (any direction)?
Exact opposites
Otolith Organs and Semicircular Canals use which cranial nerve?
8
otolith organs synapse onto what (2)?
The lateral vestibular nucleus
semicircular canals synapse onto what?
medial vestibular nucleus
What does the 2nd order neuron project of the otolith organ that is going into the CNS?
The cerebellum
What does the 2nd order neuron project of the otolith organ that is going into the body?
Limb motor neurons
What does the 2nd order neuron project of the semicircular canals that is going into the CNS (2)?
-VP nucleus of the thalamus
-Extraocular Motor Neurons
What neurons (numbers) does the extraocular motor neurons go to?
3, 4, 6
What does the 2nd order neuron project of the semicircular canal that is going into the body?
Neck motor neurons
What tract does the neck motor neurons and the extraocular motor neurons use?
Medial longitudal fasciculus
What is Vestibulo-Ocular Reflex (VOR)?
Maintains focus of eyes while rotating head
What muscles move eye left or right in VOR (2)?
lateral rectus (temporal side of eye) or medial rectus (nasal side of eye)
What does nerve 3 synapse onto for the extraocular motor neurons?
Oculomotor Nucleus
What does nerve 4 synapse onto for the extraocular motor neurons?
Trochlear Nucleus
What does nerve 6 synapse onto for the extraocular motor neurons?
Abducens Nucleus
What does In Vitro mean?
In cell culture outside of animal
What does In Vivo mean?
In the animal
What does pharmacology mean?
How a drug affects an animal
What causes axons to form in relation to actin?
The depolymerization of acting
What causes axons to form in relation to Microtuble?
The stabilization of microtubles
What protein is essential to producing axons?
Cdc42
What happens when Cdc42 is inhibited?
Lack of axon development and smaller brain (due to less axons being produced)
What protein recognizes Microtubles in axons?
KIF5
What protein recognizes microtubles in dendrites?
KIF17
What keeps large molecules from entering the axon?
A actin wall forms at beginning of axon once it becomes polarized (mature)