Somatosensory 1 & 2 Flashcards
How many pairs of spinal nerves and cranial nerves do we have?
31 pairs of spinal
12 pairs of cranial
Define somatic sensory system
Sensation as it relates to the body
What are examples of somatic sensory?
Touch
pressure
vibration
limb position
heat
cold
pain
How are somatic sensory signals sent?
Transduced by receptor within skin or muscles and conveyed to a variety of CNS targets
___ receptors are for fine/light touch, vibration and pressure
Mechano receptors
___ receptor is for proprioception
Proprioceptors
___ receptor is for painful stimuli and coarse touch
Nociceptors
___ receptor is for changes in temperature
Thermoreceptors
Define somatosensory afferents
Convey information from the skin surface to central circuits
___ in the dorsal root ganglia give rise to processes that receive information from the skin and send process into the spinal crod
Pseudounipolar neurons
Neurons in the dorsal root ganglia are often called
pseudounipolar
A __ neuron pathway is involved w/ sensation
3
What is the relay center of the brain?
Thalamus
1st neuron in the neuron pathway is
Dorsal root ganglia
___ is the process of converting the energy of a stimulus into an electrical signal
sensory transduction
afferent fibers are often encapsulated by specialized receptor cells called
mechanoreceptors
afferent fibers w/o specialized receptors are
free nerve endings
what are free nerve endings important for?
sensation of pain
Describe stretch gated channels
mechanical stimulus puts pressure on the encapsulation which causes channels to stretch and Na+ rushes in
- deformation of pacinian corpuscle stretches the membrane
Deformation of a ___ stretches the membrane and increases opening of a stretch-sensitive ion channel
Pacinian corpuscle
define modality
Characteristics given to a stimuli
What are the modalities?
vision
taste
audition
cold
cool
light touch
vibration
itch
Is laughter a modlity?
No b/c there’s no direct stimulus
Is sharp pain myelinated or unmyelinated? Is dull/aching pain myelinated or unmyelinated?
Myelinated
Unmyelinated
Is a larger axon faster or slower?
Faster
Define receptive field
Area of body that receives information b/c of AP
Does a larger or smaller receptive field have more innervation/more sensation?
Smaller
Why is it important that dermatomes overlap?
If nerves damaged, you won’t loose ability to receive information b/c of overlap
What’s 2 point discrimination? Is it easier to distinguish separate points in large or small receptive fields? Why’s it important in clinical use?
Minimum distance required to perceive 2 simultaneously applied stimuli as distinct
Small b/c no overlap
Used to assess extend of nerve damage or peripheral nerve recovery after damage
___ is defined as afferents that differ in the way they respond to stimulus over time
Temporal dynamics
Describe slow and rapidly adapting afferents
Slow
- tells you about beginning and end
- gives information about size and shape of object
Rapidly
- give you information about movement
- Not continuous
What are the 4 types of mechanoreceptors? Which ones are rapidly adapting/slow adapting? Do they all have a low/high threshold of action?
Meissner (rapidly)
Merkel cell (slow)
Ruffini (slow)
Pacinian (rapidly)
Low
Meissner afferents provide information about? Where are they located? Small or large receptive field?
skin motion
Dermis
Small
Merkel cell afferents provide information about? Where are they located? Small or large receptive field?
Edges, points, corners and curvature
Epidermis
Slow
Pacinian afferents provide information about? Where are they located? Small or large receptive field?
Vibration and pressure
Dermis and subcutaneous layer
Large
Ruffini afferents provide information about? Where are they located? Small or large receptive field?
Skin stretch
Dermis
Large
Free nerve endings have a high/low threshold of action? What do they provide information about?
High
Temperature
What are the 6 fibers we need to know? What are each of their types?
Aalpha (Ia)
Aalpha (Ib)
Abeta (II)
Adelta (III)
B
C (IV)
Myelination state of A, B, and C fiber. Conduction speed of them? Large or small?
A and B are myelinated
A is fast and large
B is 2nd fastest and larger the C
C is slow and small
Temperature is ___ adapting. Is there a larger range for cold or warm fibers? Why?
Slow adapting
Cold b/c it is not as painful as heat
describe lateral inhibition. How does it work?
body finds where main point of stimulus came from
Collaterals inhibit the other neurons, which allows your body to determine where the stimulus came from
Define labeled line theory
each nerve fiber is devoted to a modality has a distinct path leading to a specific area of the brain devoted to that modality
What are the 3 ways your brain interprets stimuli in neural coding?
- Labelled line
- Stimulus intensity
- Recruitment (how many fibers are activated by stimulus)
