Ascending Spinal Pathways Flashcards
anatomical types of receptors
free nerve endings - pain
encapsulated - touch, mechanical
special neural receptor cells - special/chemical senses
functional types of receptors
mechanoreceptors nociceptors photoreceptors chemoreceptors thermoreceptors
adequate stimulus
most appropriate stimulus that will allow receptor to pass current
modality
the sense it carries
ex/ stimulus = light
modality = vision
receptor potential
proportional to strength of stimulus
-graded potential
at threshold - primary afferent produces action potential
pre-cenral gyrus
primary motor cortex
post-central gyrus
primary somatosensory cortex
brodmans areas post central gyrus?
3, 1, 2
somatosensory
brodmans area for pre-central gyrus?
4
motor
targets for somatosensation
reflex arc reticular formation hypothlamus > limbic system thalamus > cerebral cortex cerebellum
**divergence of neurosystem
labeled line code
if you stimulate this tract
-modality of this tract results in certain sensation being felt
codes modality
population code
as intensity increases
number of receptors activated increased
frequency code
as intensity increases - rate of APs increases
receptor field
part of environment to which neuron responds
resolution
ability to distinguish between 2 separate stimulus
low density - large receptive field - less resolution
-few number of neurons in cortex
high density - small receptive field - more resolution
-larger number of neurons in cortex
large receptive field
lower density
lower resolution
fewer number of neurons in cortex
general proprioception
static position sense - know where is in space
kinesthesia - feeling movement
axons of PCML
A-alpha
large diameter, myelinated - fast
joint receptors
joint angle and tension in joint capsule
golgi tendon organs
sense tension in organs
muscle spindles
in extrafusal fibes
-detect change in muscle length
skin mechanoreceptors
also signal in proprioception
proprioceptors
joint receptors
golgi tendons
muscle spindles
skin mechanoreceptors
discriminative touch
high degree accuracy in location
ex/ graphesthesia / stereognosis
vibration
often tested with tuning fork
sensory ataxia
without coordination
-lack of proprioception
dysmetria - incorrect metering
wide base stance
truncal sway
difficult turning
inaccuracy in voluntary movements
anterolateral system
nociception, temp, crude touch
4 tracts
region of tracts of ALS
in anterior and lateral funiculi
-anterolateral region of cord
spinothalamic tract
conscious of ALS
projects to primary somatosensory cortex
primarily from somatic structures
tracts of anterolateral system
spinothalamic
spinoreticular
spinomesencephalic
spinohypothalamic
spinoreticular tract
projects to reticular formation
- alerts our attention to painful stimulus
- focus attention
- some autonomic tract
reticular formation
loose group of nuclei in core of brainstem, from medulla to dicencephalon
spinomesencephalic tract
to periaqueductal grey
pain modulation
-descend spinal cord
spinotectal tract
subset of spinomesencephalic tract
“visual grasp reflex”
spinohypothalamic tract
coordinate autonomic response to stimuli
-feel nausea with intense pain
emotional response to pain
RF and hypothalamus > limbic system
spinoreticular and spinohypothalamic tract
axons of anterolateral system
A-beta
A-delta and C
lightly or unmyelinated
small-medium diameter
-slower conducation
A-beta axons
touch and temperature
anterolateral system
A-delta and C fibers
pain
anterolateral system
C-fibers
unmyelinated
