NS V Sensory Physiology Flashcards
where do afferent pathways enter the spinal cord
through the posterior/dorsal root
what does the dorsal column pathway send info about
touch pressure proprioception
what does the spinothalamic tract send info about
pain and temperature
where does the dorsal column pathway cross over
lower medulla
where does the spinothalamic tract cross over
at the spinal cord
what neuron is the one that always crosses over
the second order neuron
what are the 5 types of sensory receptors
-mechanoreceptors
-chemoreceptors
-thermoreceptors
-nociceptors
-photoreceptors
what do mechanoreceptors receive info about and where are they found
info about compression/stretch
- found in skin, muscle spindles, hearing, equilibrium, arterial pressurer
what do chemoreceptors signaled by
ligands
what are nociceptors signaled by
damage
the particular form of energy to which a receptor is most sensitive is called its _____?
adequate stimulus
what does activation of sensory receptors cause
change in membrane potential called transduction and produces a graded potential
what type of receptor is a pacinian corpuscle
mechanoreceptor
what does a larger graded potential lead to
larger number of APs
what is the relationship between increase in stimulus strength and graded potentials
direct but not linear
what is the intensity of stimulus determined by
the frequency of APs (temporal summation) and the total number of receptors activated (spatial summation)
what is adaptation
when stimulus is maintained the frequency of APs decreases over time
where can adaptation occur
at the receptor or in the neuron
what is tonic vs phasic
tonic adapts slow phasic adapts fast
what happens in receptor adaptation
decrease in amplitude of graded potential over time in the presence of a constant stimulus
what do tonic receptors help differentiate
stimulus intensity
what do phasic receptors help differentiate
duration
what are examples of tonic receptors
, nociceptors, baroreceptors, chemoreceptors
what are examples of phasic receptors
pacinian corpuscle
what is the labeled line principle
a precise type of stimulus activates specific receptors and postsynaptic cells. the info continues on a pathway that specific kinds of information are conveyed by specific nerve fibers to specific regions of the CNS that are programmed for perception of that modality
what does the homonculus do
correlates the anatomical regions of the CNS with where interpretation and awareness of sensations are perceived
where do second to third order neurons synapse
at the thalamus
what is a receptive field
region where a single fibers afferent receptors are located
what is the effect of overlap in receptive fields
it improves localization ability
what is acuity
precision with which a stimulus is perceived
what does lateral inhibition do
enhances acuity
how does lateral inhibition work
it decreases lateral spread of an excitatory signal and increases degree of contracts in the sensory pattern perceived in the cortex
where does lateral inhibition occur
at each synapse, medulla, thalamus and cerebral cortex
what is the conduction velocity and type of information transmitted by A alpha fibers
fast
-muscle spindle, muscle tendon, skeletal muscle
what is the conduction velocity and type of information transmitted by A betafibers
fast
-muscle spindle, hair receptors, vibration, high discrimination touch, deep pressure, skeletal muscle
what is the conduction velocity and type of information transmitted by A gamma fibers
fast
-deep pressure and touch, pricking pain
what is the conduction velocity and type of information transmitted by A delta fibers
fast
-deep pressure and touch , pricking pain
what is the conduction velocity and type of information transmitted by C fibers
slow
- crude touch and pressure, tickle, aching pain, cold and warmth
what are the types of mechanoreceptors
-free nerve endings
- pacinian corpuscles
what is the function and location of free nerve endings and what type of adaptation
function: detect touch and pressure (temp and pain)
location: skin, cornea, dental pulp, GI tract
-slow/tonic
what is the function, location, and type of adaptation of pacinian corpuscles
function: detect deep pressure, vibration
location: subcutaneous tissue, viscera, joints
-rapid/phasic
what type of vibration is detected by pacinian corpuscles? meisnners?
pacinian- higher frequency
meissners: lower frequency
what spinal pathway detects vibration
dorsal column pathway
what is the function, location, and type of adaptation of meissners corpuscles?
function: detect light, touch, pressure and vibration
location: glabrous skin
-rapid/phasic
what is the function, location, and type of adaptation of merkels discs
function: localize continuous pressure and sensing an objects texture
location: all skin
slow/tonic
what is the function, location, and type of adaptation of ruffini’s endings
function: sensitive to stretch or indentation; proprioception
location: deep layers of skin, joints, surrounding tooth roots
-slow/tonic
what are the receptors in the periodontal ligament
mechanoreceptors that are ruffini-like receptos
what is the function, location, and type of adaptation of hair end organ
function: hair movement
location: base of hair follicle
-rapid/phasic
what side of the spinal cord does the ascending sensory tract ascend the spinal cord in the dorsal column pathway
same side as the stimulus
what side of the spinal cord does the ascending sensory tract ascend the spinal cord in the spinothalamic pathway
opposite side of the stimulus
what are the proprioception receptor types
-photoreceptors
-touch and pressure receptors in skin, joints, ligaments (periodontal ligament)
-skeletal muscle receptors
-vestibular receptors
what are examples of skeletal muscle receptors
-muscle spindles
-golgi tendon organs
