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70 Cards in this Set

  • Front
  • Back
what is a local potential? aka..
recpetor potential, generator potential: electrical potential induced at site of stimulus; graded, electrical event
where and how are AP generated?
AP generated when a local potential is large enough
AP occur in regions with VG Na+ channels (ex: nodes of ranvier; not at receptive ending)
what happens to cause a local potential? use a touch R as an example
touch R (Pacinian corpuscle) stretched and stimulated to open MECHANICALLY gated Na+ channels
what happens after a local potential is generated?
if lg enough, stim an AP to travel retrograde down axon (past DRG) to presynaptic terminal; releases NT on postsynaptic cell (often interneuron) in dorsal horn of SC; new AP (IPSP, EPSP) generated in postsynaptic neuron travles through CNS
what are some attributes of a sensory stimulus that CNS interprets? (4)
modality (ex: vision, taste)
intensity (proportional to stim strength)
duration (length of stim)
where does a end plate potential occur?
at n/m jxn
what are dermatones?
regions of the skin that are innervated by spinal nerves originating at DRGs at a specific level
what are 4 somatic modalities?
what are the types of somatosensory receptors? (3)
mechanoreceptors- include touch and proprioception
how does the distribution of somatosensory receptors determine sensation?
if have cold probe placed over area of skin without thermoreceptors then would only feel touch (via mechanoreceptor)
what is the general path of almost all sensory afferents? what is the exception?
all sensory info travels through thalamus on way to the cortex (post-central gyrus)
exception is olfaction; goes to thalamus after?
what are the 2 basic receptor structures?
bare nerve ending (noci and thermoreceptors)
end organ-nonneural capsule around axon terminal (mechanoreceptors)
what is a pacinian corpuscle? ruffini's endings?
mechanoreceptor in skin that detects touch and vibration

general mechanoreceptor
how are hair follicles innervated?
axon nerve ending wraps around hair follicle; is activated with displacement
what is a merkel cell?
cell in skin assoc with touch; when stimulated, rel NT on post synaptic sensory neuron to open channels
what is the fxn of limb proprioception?
convey sense of position and movement of limbs
stationary position v. kinesthesia (limb movement)
what are extrafusal v. intrafusal muscle fibers?
extrafusal are innervated by alpha motor neurons (LMN) and are stimulated for contraction
intrafusal m. fibers comprise the muscle spindle and are contained within the extrafusal fibers
how does the muscle spindle convey sensory info?
intrafusal fibers are wrapped in sensory receptors (proprioceptors)
stretch m-> stretch intrafusal fibers->stretch sensory ending
what type of fibers innvervate muscle spindles?
Ia afferents
detect m. length/stretch
what does the density of muscle spindles correlate to?
more muscle spindles for finer control of movement (extraocular eye mm.)
what are golgi tendon organs? what innervates them?
mechanoreceptors that relay info abt m. tension
Ib afferents
what type of axon is assoc with free nerve endings? what is their fxn?
C, Ad(elta)
pain, temp
slow adaptation
what type of axon is assoc with meissner's corpuscles?
(b/w dermal papillae)
touch, pressure
rapid adaptation
what type of axon is assoc with pacinian corpuscles?
deep pressure, vibration
rapid adaptation
what type of axon is assoc with merkel's disks?
touch pressure
slow adaptation
what type of axon is assoc with ruffini's corpuscles?
stretching of skin
slow adaptation
which axon/peripheral n. fiber is the largest? smallest (in diameter)?
largest: I (a,b)
smallest: IV (C)
I (a,b), AB(eta), AD(elta), C
which n. fibers are proprioceptors?
Ia and Ib
which n. fibers are mechanoreceptors? (touch, pressure)
which n. fibers are nociceptors?
AD(elta) and C
which n. fibers are thermoreceptors?
AD(elta) and C
which part of a sensory neuron is sensitive to stimulus energy?
the terminal of the peripheral branch of the sensory neuron
which afferent has the fastest conduction velocity?
A(Beta) fastest because largest diameter
which afferents are myelinated?
(all except C)
which afferents are involved in sharp pain? what abt slow, dull pain?
sharp- AD(elta)
what happens in diabetics with peripheral neuropathy?
degeneration of AD(elta) and C fibers (nociceptors) gives sensation of pain
which n. fibers are assoc with itch?
C fibers
what is the relationship b/w the generator potential and the size of the stimulus?
directly proportional
relationship b/w AP and local potential?
amplitude of local potential dir proportional to frequency of AP
what is adaptation of a n. fiber receptor?
habituation to stimulus
slow-pain and m. tension
fast-touch, pressure
what is the mxn of nociceptor detection of pain? what is the stimulus?
stimulus is tissue damage
damaged cells rel bradykinin, prostaglandins, K+ to activate nociceptor
what happens after activation of nociceptor?
nerve endings rel substance P: increases vessel permeability, vasodilation-> more inflammation; activates mast cells to release histamine ->activate nociceptors
what is the rel b/w density of receptor terminals in an area and the size of the receptive field?
highly innervated areas (sensitive areas, lip) have small receptor fields
what is the 2 point discrimination threshold?
the distance that needs to separate 2 stimuli before it can be distinguished as 2 stimuli
what are some ex of things that have hi v low 2 pt discrimination?
highly innervated areas (with small receptive fields) have a small 2 pt threshold (fingers, lips, nose, cheek)
sparsely innervated areas (w/ lg receptive fields) have large 2 pt discrimination values (calf, back, thigh, upper arm)
what is a dermatone?
the region (receptive field) that is innervated by each spinal n.
what is the path of sensory info on its way to the brain?
peripheral afferent->central afferent-> synapses in the spinal cord-> ascends to the medulla and thalamus-> to somatosensory cortex
what is somatotopy?
idea that receptors in adjacent portions of peripheral receptive fields project neurons to regions adjacent in CNS
what is the path for a pain/temp afferent? what type of afferent?
C, AD(elta)
3 neuron track
primary afferent synapses immediately on a projection interneuron in dorsal horn
secondary afferent crosses SC and ascends through ventral-lateral funiculus to synapse in thalamus
tertiary afferent goes from thalamus to somatosensory cortex
how does the path of a mechanoreceptor afferent differ from the pain/temp afferent?
mechanoreceptor afferent doesnt synapse immediately upon entering SC
what is the path of a mechanoreceptor afferent?
primary enters dorsal horn; travels to medulla where it synapses in dorsal funiculus (cuneate nucleus-from above T6; gracile nucleus-from below T6)
secondary crosses in medulla and then travels up to synapse in thalamus
tertiary travels to synapse in somatosensory cortex
what would be the result of a lesion above the medulla? (in terms of mechanoreceptors and pain/temp receptors?
a lesion above the medulla on the right would cause loss on contralateral side (left)
whats the result of a lesion on the right between the medulla and the level of crossing for the pain/temp?
ipsilateral loss for mechanoreceptors (touch, pressure)
contralateral loss for pain/temp receptors
what is contained in the dorsal horn?
interneurons and ascending sensory neurons
what is contained in the intermediate zone?
autonomic preganglionic neurons
afferents traveling to cerebellum
what is contained in the ventral horn?
interneurons and motor axons
what are the lamina of the gray matter and what "horns" do they rel to?
dorsal horn: I-VI

intermediate zone: VII

ventral horn: VIII-IX
what sensory neurons synapse in lamina I, II?
AD(elta) and C fibers (pain, temp)
what afferents synapse in lamina III-VI?
Ia and AB(eta) -proprioceptors and mechanoreceptors
what is Lissauer's tract?
region where A(Delta) and C fibers enter the spinal cord
what are the 3 general paths for an A(Beta) or Ia fiber entering the spinal cord?
1. can travel up dorsal column to synapse in medulla
2. can synapse in clark's nucleus and cont to cerebellum
3. can enter ventral horn to directly synapse on LMN (reflex; Ia muscle spindles)
what is clark's nucleus and where is it located?
in intermediate zone, lamina VII
present T1-L2 only
relays info about body position to cerebellum
location of synapse for Ia and AB(eta) fibers
what is the intermediolateral column?
in intermediate zone; lamina VII; T1-L3
contains presynaptic cell bodies for autonomic system
presynaptic axons leave through ventral horn to synapse in sympathetic ganglia
what is contained primarily in lamina VIII?
interneurons for skeletal m. contraction
where is the phrenic nucleus?
lamina IX- medial portion of ventral horn from C3-C5
which would cause more damage? a lesion to a peripheral n. or a spinal n?
peripheral n
covers many dermatones and contains spinal nerves from several (2-4) DRG
what is the substantia gelatinosa?
in lamina II of all levels of spinal cord
receives afferent info (pain, temp) from non-finely myelinated fibers (Adelta, C)
where are the preganglionic autonomic cell bodies located in the spinal cord? at what level?
in the intermediolateral nucleus
lamina VII
what are 4 things that can clue you in when determining the level of a spinal cord section?
1. dorsal columns get smaller caudally
2. above T6: funiculus gracilis and funiculus cuneatus; below T6: only funiculus gracilis
3. C8, L5- large ventral horns; LMN to supply limbs
4. lateral funiculus decr in size caudally (corticospinal tract)
which afferent fibers are not myelinated?
C fibers (dull pain, itch, warm temps)