Somatosensory Ascending Pathway - Part I Flashcards
How do the mechanoreceptors encode the characteristics of the stimuli?
different mechanoreceptors respond to limited different modalities of stimuli
What is the concentration of mitochondria in the stimuli detection area?
high!
What is a specialized nerve ending?
receptive area
What is an example of a specialized cell or neuron ?
- visual pathway (i.e. rods)
- hair cells for hearing, vestibular functions
What are the two layers of receptors?
- microscopic (bigger)
- macroscopic (very small)
What do microscopic receptors detect?
energy
- molecules interactive with the stimulants/energy
What are the characteristics of macroscopic receptors?
- high concentration of mitochondria in the stimuli detection area
- specialized nerve ending
- specialized cell or neuron
What mechanoreceptor does blood pressure?
- carotid sinus
What chemoreceptor does oxygen concentration of blood?
- carotid body
What do mechanoreceptors detect?
fine touch, vibration, stretch, etc
What kind of receptor is for A-beta?
mechanoreceptor
What do chemoreceptors detect?
taste, smell, pH, O2, etc.
- i.e. carotid body for O2 concentration
What do thermoreceptors detect?
cold to hot, FLAVOR OF FOOD
What do nociceptors detect?
noxious stimuli, pain
What is another sensory receptor not usually mentioned?
electromagnetic waves
- FISH, know how to swim home
Where does conscious localization project to?
S1
Is somatotopy maintained with conscious localization?
yes
What maintains the somatotopy?
- dorsal column (fine touch, vibration)
- lateral spinothalamic tract (sharp p!)
Where does unconscious localization project to?
subcortical structures
- reticular formation, cerebellum, etc.
What are other special sensations?
taste, smell, vision, hearing, vestibular
Do we need the somatotopy for taste?
no
- cannot remember all tastes all the time, tongue detects
Do we need the somatotopy for smell?
No
- nasal cavities
Do we need the somatotopy for vision?
NO, have retinotopy
- reason we know whats on left and right, image is projected on retina
Do we need the somatotopy for hearing?
NO, have tonotopy
- composes sound into different frequency, projects to A1, integrates, and decodes meaning of sounds
Why is the vestibular sensation important?
- body in space, integrate info in cerebral cortex
- BALANCE
What is the intensity of receptor potential measured in?
AMPLITUDE
- changes in the intensity of the stimuli
What is the intensity of action potentials measured in?
FREQUENCY
- receptor potential above the threshold
How many AP can happen in 1 second?
- with higher receptor potential higher AP, can have few to 1000s
When does the receptor potential stop?
when stimuli stops
Do we still have a baseline AP without stimuli?
Yes
- if you want to rob a bank you dont turn off your car
- helps us be ready/prepared for next function
What are lagging effects?
persistence of vision
Where is sensory memory most prominent?
visual system
What is an example of a slowly adapting static stimuli?
smell
- weird food, stink, but adapt and “less stink”
What kind of stimuli are you slowly adapting receptors for?
static stimuli
What kind of stimuli are rapidly adapting receptors for?
dynamic stimuli
What kind of adaptor is for pulling hair CONSTANTLY?
Slow adapting, static stimuli
What kind of adaptor do motor function need?
fast adapting (FA)
Which ascending and descending tracts run in the lateral funiculus?
Descending
- lateral corticospinal tract
- rubrospinal tract
- medullary reticulospinal tract
Ascending
- lateral spinothalamic tract
How are receptors transducted?
- stimulants/energy as neurotransmitters
- on receptor cells or nerve endings
Where is the receptor area for transduction of receptors?
post-synaptic membrane
What kind of receptors are on the post-synaptic membrane?
- ionotropic receptor
- metabotropic receptor
What are the effects of transduction of receptors?
- Excitatory: EPSP, depolarization
- Inhibitory: IPSP, hyperpolarization
What kind of channel is in the trigger zone?
voltage-gated sodium channel
What can be receptor/receptive areas?
cell or specialized area of nerve endings
Where does peripheral process occur?
outside of CNS
- conduct along axons
- CNS: brain stem or spinal cord
What is an examplie of a trigger zone?
like in a hillock
What happens in a trigger zone?
- rock in lake, waves spread everywhere
- changes to initiate AP
- spreads out, receptor potential intensity decreases = dissipation
What happens in the central process?
SHORT
- axons arrive to soma
- in CNS
What should we know about the cauda eqina?
- LONG
- axons get myelin sheath from oligodendrocytes (sensory and motor)
- MS affects cauda equine myelin sheath (is destroyed)
What are the two types of skin?
- hairless/glaborous
- Hairy
What kind of receptors are free nerve endings?
unimodal and polymodal receptors
What are the layers of cutaneous innervators?
- free nerve endings (EVERYWHERE)
- Meissner corpuscle
- Merkel cell
- Ruffini corpuscle
- Pacinian corpsule
Where is hairless/glabrous skin found?
palm/sole/lip
What are free nerve endings in?
EVERY BODY PART
- epidermis
What are the 4 cutaneous mechanoreceptors?
- Meissner corpuscle
- Merkel cell
- Ruffini corpuscle
- Pacinian corpsule
What cutaneous receptors are unimodal?
- merkel cell
- Ruffini corpuscle
- Pacinian corpuscle
Where is hairy skin found?
EVERYWHERE but palm,lip, and sole
What kind of mechanoreceptor is not in hairy skin?
Meissner corpuscle
How many mechanoreceptors are in hairy skin?
still 4
Where are meissner corpuscles located?
Hairless skin only
What do meissner corpuscles detect?
flutter/vibration of small amplitude
What common sensation is done by the meissner corpuscles?
numbness/tingling
What do free nerve endings detect?
pain and crude touch
Why does a paper cut that does not draw blood still hurt?
free nerve endings in epidermis
- no blood vessels, but FNE = p!
What kind of pain fibers are in the free nerve endings?
C- fibers and A-delta
Are C-fibers myelinated?
NO = SLOW
Are A-delta fibers myelinated?
poorly myelinated, SLOW
What do merkel cells detect?
complex and fine touch, percieving edges and stereognosis
What is sterognosis?
know structure without seeing it using only feeling
- paper bag in NMSK
What is the function of hair follicle receptors?
fine touch and movement
- hairy skin only (duh)
- ex. cat whisker, detects movement
What do ruffini endings detect?
stretch sensation in skin
- somatic!
- A- beta (SA)
What do pacinian corpuscles detect?
various functions including vibration in skin (higher amplitude than meissner)
Where are pacinian corpuslce slocated?
strictly, not in skin; whole body
What is a receptive field?
area innervated by one single axonal terminal
What is unique about receptive fields?
smaller and more disciminative
Where are fine touch/2-point discrimination highest?
in fingers, lips, sole
Where are fine touch/2-point discrimination fields located?
around the glabrous/hairless skin
What kind of mechanoreceptors are for fine touch/2-point discrimination?
- UNIMODAL
- meissner corpuscle and Merkel Cell
When performing 2 point discrimination test, what are you testing?
Ability to differentiate two points in a receptive field
- Meissner
- Merkle
Which mechanoreceptors are in the glabrous/hairless skin?
- Meissner corpuscle
- Merkle cell
- Ruffini endings
- Pacinian corpuscle
What are the two types of skeletal muscle fibers?
- extrafusal
- intrafusal
What are extrafusal muscle cells innervated by?
alpha motor neuron
What do intrafusal muscle cells form?
muscle spindle
What innervates the muscle spindle?
gamma motor neuron
What are the two types of fibers in the muscle spindle?
nuclear bad and nuclear chain fibers
What are intrafusal cells innervated by simultaneously?
- sensory neurons
What type of sensory neurons innervate the intrafusal muscle cells?
- Type Ia (Aα)/ II (Aβ)
FAST, highly myelinated
What do the type Ia (Aα)/ II (Aβ) sensory neurons that innervate intrafusal muscle fibers detect?
proprioception and motor information
What sensory neurons innervate nuclear bag and chain fibers in the muscle spindle?
Type II (Aβ)
What are the mechanoreceptors for intrafusal muscle cells?
like ruffini endsings
What kind of translator is the muscle spindle?
MOTOR TO SENSORY
- translates motor functions to sensory feedback
Where is the golgi tendon organ located at?
musculotendinous junction
What is the golgi tendon organ innervated by?
Type Ib (Aα), Ruffini-like sensory neurons
- FAST
Why do we feel pain in muscles and tendons too?
free nerve endings
What kind of sensory neurons innervate the joint capsule?
Aα
What kind of nerve endings are in the joint capsule?
- ruffini-type endings
- pacinian-type endings
What does the joint capsule need to do?
detect change of body in space ASAP to maintain balance
What is the frequency of vibration for a tuning fork test?
128 Hz
What kind of nerve endings are being tested during a tuning fork test around joints?
pacinian type endings
What kind of channel is PIEZ02?
modality-gated sodium ion channel
What kind of terminals does PIEZ02 have?
both markel cell and axonal terminal
(A beta)
How does a PIEZ02 initiate an RP?
stretches open PIEZ02 and induces the receptor potential
- both merkel and axon terminal of A beta axons stretch above a specific amplitude of stimuli results in a resting potential
What should we know about the stimuli with PIEZ02?
- stimuli with different intensities
- Receptor potential to action potential
- weak can cause a receptor potential
- strong can make it above, initiate AP, open PIEZ02 channels and allow NA+ ions to flow in
What are the 2 types of free nerve endings in the skin?
- c-fiber for diffuse pain; myelinated = fast
- A-delta (Aδ) for first, sharp pain; poorly myelinated
Which nerves innervate the intrafusal muscle fibers?
γ motor neuron: Aβ
Ia: Aα
II: Aβ
Free nerve endings: Aδ and C-fiber
