Somatosensory System Flashcards
What is proprioception?
Joint and muscle position in space
What is nociception?
Pain
What is pruriception?
Itch
What are the 3 divisions of the somatosensory system?
Exteroceptive division
Proprioceptive division
Enteroceptive division
Exteroceptive division - what is it?
Registers infromation from the surface of the body
Cutaneous senses
Proprioceptive division - what is it?
Monitors posture, movement
Enteroceptive division - what is it?
Closely related to autonomic function
The 1st/2nd/3rd order neurone is the primary sensory afferent ?
1st order neurone
Which order neurone (1st/2nd/3rd) starts at a peripheral site of the body ?
1st order neurone
Cell body of the 1st order neurone will be located where?
Dorsal root ganglion (innervation of limbs, trunk, posterior head)
OR
Cranial ganglia (innervation of anterior head)
The 2nd order neurone is located in the CNS. True or false?
True
Where is the cell body location of 2nd order neurone?
Dorsal horn of SC or
Brainstem nuclei
Where is the cell body location of 3rd order neurone?
Thalamic nuclei
Light pressure has a low/high action potential frequency ?
Low
What do mechanoreceptors detect?
Touch, pressure, vibration
Low threshold units respond to high intensity stimuli. True or false?
False
- low intensity stimuli
What do low threshold mechanoreceptors mediate?
Fine discriminatory touch
High threshold units respond to nociceptors. True or false?
True
- extremes
The greater the diameter of an axon, the lower/higher its internal resistance so the slower/faster the conduction
Greater diameter
Lower resistance
Faster conduction
Which primary sensory afferent fibres have the largest diameter?
Proprioceptors
Which primary sensory afferent fibres have the smallest diameter?
Temperature
Pain
Itch
What is the receptive field ?
The territory from which a sensory unit can be excited.
A large receptive field will have low/high density of innervation and low/high acuity ?
Low
Low
A small receptive field will have low/high density of innervation and low/high acuity?
High
High
Merkel cell neurone complexes is a sensory receptor of hairy/hairless/both skin and has a small/large receptive field ?
Hairless and hairy
Small receptive field
Where are merkel cell neurone complexes located?
Areas with high sensory acuity (e.g. fingers)
Meissner corpuscle is only ever found in hairy skin. true or false?
False
- only ever found in hairless skin (e.g. fingers)
Pacinian corpuscle has a small/large receptive field and detects what?
Large
Deep vibration
Name 3 sensory receptors of hairless and hairy skin ?
Pacinian corpuscle
Merkel cell neurone complexes
Ruffini endings
Name 1 sensory receptor of purely hairless skin?
Meissner corpuscles
As information is conveyed from one neurone to the next in a sensory pathway, differences in the activity of adjacent neurones are amplified. What is this called?
Contrast enhancement
When one neurone is active, it inhibits the activity of its neighbours via inhibitors neurones. What is this called?
Lateral inhibition
Somatic information from the anterior head is mediated by which system?
trigeminal system
Where is the somatosensory cortex located?
Post central gyrus of the parietal cortex
The somatosensory cortex is located immediately anterior/posterior to the central sulcus ?
Posterior
The somatosensory system consists of Brodmann areas. True or false?
True
How many layers does the somatosensory cortex have?
6 layers
What does the homunculus illustrate?
How much cortex is devoted to a particular body part
Which body part is located at the medial part of the post central gyrus? Trunk Face Upper limb Lower limb
Lower limb
Which body part is located at the lateral part of the post central gyrus? Trunk Face Upper limb Lower limb
Face
Which area of the brain receives and integrates information from the primary somatosensory cortex ?
Posterior parietal cortex
