Theme 1 Flashcards
What is the wiring pattern of the DCML pathway?
- Receptors in the skin
- Dorsal root ganglion cells
- Dorsal column of spinal cord
- Medulla (Gracile and Cuneate Nuclei)
- Midbrain (Medial lemniscus tract)
- Ventral posterolateral (VPL) nucleus of thalamus
- Primary somatosensory cortex
Where does the DCML decussate?
Medulla
What is the DCML pathway responsible for transmitting?
- Fine touch
- Proprioception
- Vibration sensation
- 2-point discrimination
What do the thalamus and cortex have (with regards to DCML pathway)?
A hardwired body map / pattern for sensory input
For every 1 fibre that ascends to the cortex, how many go downwards?
10
What are mechanoreceptors?
Sense organs / cells that respond to sensory stimuli
What are the two types of mechanoreceptors?
Rapidly adapting and slow adapting
How do rapidly adapting receptors work?
Fire at onset, but not continually after that even if stimulus is held
How do slowly adapting receptors work?
Fire at onset, and then keep firing (may change frequency)
What are the main mechanoreceptors in the skin?
- Meissner corpuscle
- Pacinian corpuscle
- Ruffini corpuscle
- Merkel’s disks
(+ free nerve endings)
Which receptor is Meissner corpuscle?
RA1
Which receptor is Pacinian corpuscle?
RA2
Which receptor is Ruffini corpuscle?
SA2
Which receptor is Merkel’s disks?
SA1
What is the role of Meissner corpuscle?
For textured objects moving across the skin
Detection of slippage between hand and object - important for grip
What is the role of Pacinian corpuscle?
More sensitive than Meissner - for fine textured surfaces
Produce sensation of vibration or tickle (important for skilled use of tools)
What is the role of Ruffini corpuscle?
Function not exactly known
Something to do with proprioception
What is the role of Merkel’s disks?
Stimulation produces sensation of light pressure
Role in detection of shapes, edges and rough textures
What percent of receptors in the skin are rapidly adapting?
55%
40% RA1 (Meisnner)
15% RA2 (Pacinian)
What percent of receptors in the skin are slowly adapting?
45%
15% SA1 (Merkel’s)
20% SA2 (Ruffini)
Where are Meissner corpuscle found?
Most common in hairless skin
Where are Merkel’s disks dense?
In the fingertips
What is the order of the mechanoreceptors in skin from superficial to deep?
Meissner corpuscle and Merkel’s disk at top (RA1 & SA1)
Ruffini towards top of dermis (SA2)
Pacinian deep in dermis (RA2)
What is the role of free nerve endings?
Pain and temperature sensation