Lecture 2: receptors and Afferent Pathways of the Somatosensation and Proprioception Flashcards
Purpose of Somatosensation and Proprioception
Explore, identify, increase feedback, and prevent injury
Cutaneous Sensory Information
1) tactile (virbration, proprioception, and kinesthesia)
2) pain
3) temperature
Muscle, CT, or joint sensory information
stretching , static and dynamic force, and skin
definition of proprioception
awareness of static joint position
definition of kinesthesia
awareness of dynamic joint position (across joints)
Sensory perception promotes
-Adaptation in posture and movement
-Is planned and reactive
-Sent from the peripheral nerve
- gives us feedback
definition of perception
-the awareness of stimuli
-Interprets sensory info into meaningful forms
- is an active and on going process: acting within ones environment (unconscious and fast)
Cutaneous Sensory Receptors
1) mechanoreceptors (pressure, touch, vibration, and proprioception)
2) thermoreceptors (temperature)
3) nocioceptors (pain)
where are Meissners corpuscles found
-in the superficial skin with a greater density at the fingertips
- small receptive fields (2-4 mm)
what do meissners corpuscles respond to
1) discriminative touch: 2 - point discrimination
2) Low frequency vibration (30-50 Hz flutter)
3) velocity sensitive (2-40 mm/s)
where are Pacinian Corpuscles found
-in the subcutaneous at a higher density in the fingertips
-With a large receptive field (greater then 4mm)
what does Pacinian Corpuscles respond to
- high frequency vibration (100-300 Hz) tickle
- deep pressure over a large space
where are Merkels discs found?
- in the superficial skin at greater density in the fingertips
-dermis and hair follicles
Small receptive field (2-4 mm)
what do Merkels discs respond too
-pressure (discriminate shapes and edges)
- touch and form
where are Ruffinis Corpuscles found
in the subcutaneous skin with a large receptive field (greater then 4 mm)
what do Ruffini’s corpuscles detect
skin stretch: direction and force
intensity and time course of Meissner’s corpuscles
rapid
intensity and time course of merkel cells
slow
intensity and time course of pacinian corpuscle
rapid
intensity and time course of ruffini endings
slow
where are Free Nerve endings found?
throughout the skin and viscera, epidermis
what do free nerve endings detect?
temperature, pain, tickle, and itch
pain stimulus purpose
-translate potentially damaging stimuli into electrochemical signals
-detects mechanical, thermal, or chemical stimuli
Types of pain
1) nociceptive pain
2) neuropathic pain
nociceptive pain
results from activation of pain receptors in the body due to tissue injury/inflammation (normal response). Usually has a localized area and stops after palpation
Neuropathic pain
direct injury to neural tissue, typically results in a burning sensation, radiating, following peripheral nerve (something is wrong with the nerve)
worse pain at rest
what are pain receptors at the skin capable of transmitting
precise information such as where an injury is located and characterize the sensation such as sharp, dull, pressure, temperature
Nociceptor types
- free nerve endings (delta)
- Unmyelinated C fibers
Free nerve endings (delta)
- carry sharp, stabbing, pricking pain or cold
- has a high threshold the results in immediate pain
Unyelinated C fibers
-C afferent fibers (slower)
-Carry dull ache pain
-Free nerve endings
-Activation threshold is higher
-Polymodal pain (receptors
chemical , heat, mechanical, hypoxia)
alpha axons
-Alpha motor neuron
-fastest and most myelinated
-Pain and temperature
Beta axons
-Sensory neuron
-2nd fastest
-Include pacinian, ruffini, meissner, and merkel
Delta axons
3rd fastest
Lightly myelinated
C fibers
The slowest
Unmylinated
pain
what is the muscle spindle
- a sensory proprioceptor within the muscle belly
- Intrafusal muscle spindle connects with the extrafusal muscle
- relays efferent information to the muscle
- contractile at both ends
what does the muscle spindle determine
-the muscle length and speed.
-Sends info to the cerebellum to calculate joint motion and movement
what does the cerebellum house
motor memory
what does the gamma do in the muscle spindle
identifies the efferent nerve that travels from the CNS to the muscle spindle. confirming the movement
how to assess the muscle spindle
by doing a tendon reflex
the tendon reflex steps
1) stimulus is activated
2) receptor muscle spindle detects the stretch
3) Afferent neuron 1 A sends the information to the spinal cord
4) spinal cord synapses with interneurons
5) Two motor neurons are activated (one to excite the agonist and one to inhibit the antagonist)
what motor action does not use an interneuron in the reflex
the excitatory neuron
Golgi tendon organs
provides Force production feedback
autogentic inhibition
Order neurons of sensory pathways
the delivery of sensory info from the periphery to the cortex
From Stimulus to Cortex pathway of afferent
1) PNS- dorsal root ganglion (1st order)
2) Spinal cord (2nd order)
3) thalamus relay (3rd order)
to the cortex
what are the two major sensory pathways
the anterolateral pathway and the posterior (dorsal) columns
what sensory information uses the anterolateral pathway?
pain, temperature, and crude touch
where does decussation of the anterolateral pathway occur
spinal cord
what sensory information used the Posterior (dorsal columns)
vibration, joint position, fine touch
where does decussation of the Posterior Dorsal columns occur
medulla
what are the three pathways of the Anterolateral pathways
1) spinothalamic
2) mesencephalic
3) spinoreticular
what are the functions of the thalamus?
- sensory relay center
-sensory integration
-influences voluntary movements
-influences limbic system and memory
-vision: visual grasp
-recognition of pain and temperature
what does the medial lemniscal pathway (posterior columns) carry
proprioceptors and mechanoreceptors
what does through the Nucleus Gracilis in the posterior (dorsal) column/ Medial Lemniscal Pathway
lower body pathway
what goes through the Nucleus Cuneatus in the posteior (dorsal) column/ Medial Lemniscal Pathway?
Pathways from the upper body
