Week 3: Peripheral and Central Somatosensory System Flashcards
Closed Loop
Closed loop: feedback at the end [Reaching] continuous feedback (sensory feedback while you’re doing the movement) Damage from dorsal root is why you would have damage
- Most ADL movements involve sensory feedback, when reaching for cup you’re faster in the beginning and begin to slow down to grab object and not knock it over
Open Loop
Open loop: constant feedback
- Throwing: Doing it so fast there’s no time for sensory feedback until it’s over
Three-neuron somatosensory pathways (first order, second order, third order)
First order: Sensory receptor to dorsal root ganglion of the spinal cord (brings information to the brain)
Second order: Spinal cord or brainstem to the thalamus
Third order neuron: Thalamus to cerebral cortex (sorts to appropriate part)
Cutaneous sensory information
Touch (superficial pressure and vibration) nociception, and temperature – signal to brain that something is injured
Musculoskeletal sensory information
Proprioception (static and kinesthetic)
Mechanoreceptors
Touch, pressure, stretch, vibration
Chemoreceptors
Respond to chemicals released by cells following damage or infection
Thermoreceptors
Hot/Cold
Tonic Receptors
Constant
Phasic Receptors
Temporary
conduction velocity of sensory axon
Most large diameter afferents (Ia, Ib, II, AB) are triggered only by mechanical stimuli – Small to large
Receptive Fields
-The are of skin innervated by a single afferent neuron
- Receptive fields are smaller in the distal extremities
Muscle Spindles
Convery information on the length and rate of change in length of the muscle.
Golgi Tendon Organs
a proprioceptor, sense organ that receives information from the tendon, that senses TENSION.
Joint Receptors
Respond to mechanical deformation of the capsule and ligaments
Somatotropin anatomical cortical representation
The face/different parts of the body across the brain
Neuropathy
happens when the nerves that are located outside of the brain and spinal cord (peripheral nerves) are damaged. This condition often causes weakness, numbness and pain, usually in the hands and feet.
Proprioception
The ability to identify trunk and limb position in space when vision is occluded.
1. Occlude to pt. vision
2. Move the pt. UE 3 times between shoulder flexion and extension (**The last position should place the extremity into shoulder flexion)
3. Ask the pt. “Is your arm up or down? Can you replicate the position with your other arm”
(Shoulder, Elbow, Wrist, Thumb – bent or straight, Pinky)
Upper extremities: Getting dressed in the dark, or a dark closet knowing where to place your arms. Grabbing something from a shelf if you cant see it.
2-point discrimination
The ability to determine whether one has been touched by 1 or 2 points. This sensory function allows an individual to perform precision grip movements during ADLs and IADLs (it prevents one from dropping objects)
1. Occlude the pt. vision
2. Apply an esthestiometer to the pt. uninvolved thumb. Ask the pt. whether 1 or 2 points have touched him or her. Gradually move the distance closer (THE 3 SMALLEST).
3. Apply an esthestiometer to the pt. uninvolved index finger. Ask the pt. whether 1 or 2 points have touched him or her.
4. Repeat with pinky
Sterognosis
Sterognosis (Pg. 76)
The ability to recognize shapes, objects, and textures by touch, with vision occluded. Allows individuals to identify familiar objects without the use of vision.
Familiar objects
Ahylognosia
Textures
Amorphagnosia
Shapes
Graphestesia
Drawing on hand
A client reaches into her purse to find her keys. She tells her OT she has a hard time finding things in her purse and everything feels the same what is most likely impaired.
Sterognosis
The OTS asks the client to close their eyes and then moves the client’s thumb 3 times between thumb flexion and extension and then places the thumb in extension.
Proprioception
Below are list of assessments and the materials used to test them.
Ahylognosia - Sandpaper
Amorphagnosia - A small cube, sphere, and cone
2 point discrimination - Esthesiometer
Sterognosis - A bag of small every day objects
A pediatric OTR is working with a 6 year old. The childs mother complains that the child is very clumsy and is always tripping or bumping into walls.
Proprioception - Where there body is in space
A 2-point discrimination impairment would most likely reveal itself in which of the following activties
Typing without looking at your hands
Damage to the dorsal root ganglion would more so impair ____ movements such as reaching as opposed to throwing.
Closed loop
Where is the decussation point of the dorsal column/medial lemniscus pathway, to the contralateral side of the body?
Medulla of the brainstem
What information do muscle spindles convey
Length and rate of change in length of a muscle
Increased axon diameter ___ nerve conduction velocity
Increases
How many neurons are along a single somatosensory pathway
3
