Somatosensory System Part 1 Flashcards
(11 cards)
4 Main Types of Somatosensory Receptors?
(Note: They are also Mechanoreceptors)
Pacinian Corpuscles
Ruffini’s Endings
Meissners’s Corpuscles
Merkel’s Disks
Terminology:
How Somatosensory Information Travels
Ipsilateral: Recieve Info. Same Side
Contralateral: Recieve Info. Opposite Side
Decussation: Cross-over of Nerve Fibers to opposite side
Dorsal Column-Medial Leminiscal Pathway
1st Order Neuron > Afferent Peripheral Neuron > Ipsilateral > Dorsal Root > Dorsal Column (Spinal Cord) > Dorsal Column Nuclei (Medulla)
2nd Order Neuron > Dorsal Column Nuclei > Decussates Medial Lemniscus (Medulla) > VP Nucleus of Thalamus
3rd Order Neuron > VP Nucleus of Thalamus > S1 (Somatosensory Cortex)
What is Agnosia?
loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective + no significant memory loss
What is Astereoagnosia?
•inability to identify an object by touch without visual input
(Damage to parietal lobe or dorsal column)
What is Neglect syndrome?
inability to process & perceive stimuli on one side of the body or environment (not due to a lack of sensation)
Hemispatial neglect is very commonly contralateral to damaged hemisphere
What is 2 Point Discrimination?
Smallest Distance Between 2 Points that can be Differentiated by the Somatosensory System as 2 Points
Factors that Influence this:
Receptor Field: Size & Density
Computing Power
Special Neural Mechanisms
Primary Afferent Axons
↓ Fastest To Slowest & Lrg. Diameter to Smallest ↓
Aα (Alpha) - Proprioception, Motor Mov’t
Aβ (Beta) - Mechanoreceptors for Touch Sensation
Aδ (Delta) - Sharp Px, Temperature
C - Throbbing Px, Itching, Temperature
Note: Only C is Unmyelinated
Causes of Lesions
Receptor Damage
Nerve Impingement/Damage
Contralateral lesions in the Brain
Note: Damage Must Be Significant for Some Tests to Work Fully as Some Dermatomes Have Overlapping Functions
Dorsal Column Medial Lemniscus Pathway
Hint: Decussation Point In Name
