Lec 6 Somatic Sensory Flashcards
Encapsulated receptors: myelinated or unmyelinated? Detects what stimuli?
myelinated
mechanical
Free Nerve Endings: myelinated or unmyelinated? Detects what stimuli?
Unmyelinated
pain/temp
First step in all sensory processes
Sensory transduction: energy from stimulus converts to electrical signal (AP)
Rapidly Adapting (AKA Phasic) Receptors
only respond to on/offset.
info about change/dynamic quality.
Slowly Adapting (AKA Tonic) Receptors
continous AP firing as long as stimulus present.
info about persistence/static quality.
Which mechanoreceptors are Rapidly-Adapting?
Meissner
Pacinian
Which mechanoreceptors are Slowly-Adapting?
Merkel
Ruffini
Meissner detects…
low-freq vibration.
tactile discrimination.
Pacinian detects…
high-freq vibration.
deep pressure
merkel detects
light pressure
ruffini detects
cutaneous stretch during digital movement
2-pt discrimination
ability to perceive 2 stimuli as distinct points
more receptors = ____ (higher/lower) 2-pt discrimination
lower
receptive fields
region of skin within which tactile stimulation evokes a response in axon
more receptors = ____ (larger/smaller) receptive field
smaller
Muscle spindle: intrafusal fibers
inside capsule
Muscle spindle: Nuclear Bag Fiber
largest intrafusal
nuclei centered
Muscle spindle: Nuclear Chain Fiber
remaining fibers, nuclei lined up single-file
Muscle spindle: primary sensory ending
group 1a myelinated axons that invx both types of fibers
Muscle spindle: secondary innervation
group 2 axons - invx chain & give off branches to bag
Muscle spindle: gamma motor neurons
causes spindle to contract
Larger muscles = ____ (higher/lower) density of spindles
lower
Trigeminal Nerve sensory branches
V1 - Opthalamic - sensation btwn eyes/forehead.
V2 - Maxillary - sensation btwn eyes/mouth.
V3 - Mandibular - sensation to mandibular region.
Trigeminal Complex components
Principle Sensory Nucleus (mechanosensory). Spinal Nucleus (pain/temp).
VPL receives projections from…
body
VPM receives projections from…
face
Axons from thalamus project to…
Layer 4 of somatosensory
Primary sensory cortex: Broadman’s 3a responds to
muscle stretch
Primary sensory cortex: Broadman’s 3b responds to
tactile
Primary sensory cortex: Broadman’s 1 responds to
texture
Primary sensory cortex: Broadman’s 2 responds to
shape/size
Broadman’s 3b projects to…
Broadman’s 1 & 2
Primary Sensory projects to
Secondary Sensory
Motor Cortex (Area 4)
Other association cortices (Areas 5 & 7)
Secondarry Sensory projects to
amygdala & hippocampus
Why are descending axons > ascending?
limits incoming sensory info, prevents CNS from being overloaded.
