Somatosensory Disorders

Question 1

What are causes of peripheral neuropathy?

Answer 1

• Diabetes
• Autoimmune (GB, CIDP, vasculitis)
• Toxic
• Vitamin deficiency
• Paraneoplastic
• Chronic kidney, liver disease
• Inherited (Charcot-marie tooth)

Question 2

What are the 4 main classes of somatosensory receptors?

Answer 2

• Tactile
• Proprioception
• Thermal sensation
• Nociceptive sensation

Question 3

Which areas of the body have high/low sensitivity?

Answer 3

H= face, fingertips

L=limbs, torso

Question 4

What types of temperature do sensory fibres/ thermoreceptors respond to?

Answer 4

• Cold pain
• Cold
• Warm
• Hot pain
• Activate Trp receptor family

Question 5

What is the function of muscle spindles?

Answer 5

-Provide sensory feedback from muscle fibres on body position & movement

Question 6

What is the function of golgi tendon organs?

Answer 6

• Regulate muscle tension or force of contraction

- Prevent muscle overloading

Question 7

What disorders are produced by damage to the posterior parietal cortex/association cortex? Define them

Answer 7

-Astereoagnosia= inability to identify objects on basis of touch alone
-Neglect syndrome= part of body/visual field disregarded. Parietal cortical lesions
Agnosia= inability to recognise/interpret objects despite normal sensory functioning

Question 8

What does damage to peripheral or sensory components result in?

Answer 8

• Neuropathy
• Phantom pain
• Neuralgia

Question 9

What is the function of tactile somatosensory receptors?

Answer 9

sensations, low threshold mechanoreceptors, merkel, ruffini, pacinian, messier

Question 10

What is the function of proprioception somatosensory receptors?

Answer 10

muscle (spindle) & joint (golgi tendon) receptors, some cutaneous mechanoreceptors

Question 11

What is the function of thermal sensation somatosensory receptors?

Answer 11

thermoreceptors, localised to discrete zones- hot/cold sensitivity

Question 12

What is the function of nociceptive somatosensory receptors?

Answer 12

mechanical, thermal, polymodal receptors

Question 13

Where are the following located:

• Ruffini
• Meissners
• Merkels
• Pacinian

Answer 13

• R= deep in dermis, long axis of the corpuscle is orientated parallel to the skin
• P=are large encapsulated endings located in the subcutaneous tissue.
• Meissners= Beneath the epidermis-sit between the dermal pupillae
• Merkels=Beneath the epidermis-aligned with the pupillae

Question 14

What is the morphology of cutaneous receptors?

Answer 14

• Meissners= Looping axonal terminals that inter-twine supporting cells, rapid adapting
• Ruffini=Nerve terminals intertwined with collagen fibrils
• Merkel=Dome structure atop axon terminals, slow adapting, slow adapting
• Nociceptors=Free nerve endings that penetrate epithelial cells, slow adapting
• Pacinian=Sensory axon surrounded by fluid filled capsule, onion-shaped, rapid adapting

Question 15

Which sensory receptors are active when reading braille?

Answer 15

Merkel afferents

Question 16

How are sensory afferents classified?

Answer 16

• L.diameter= rapidly conducting, low threshold mechanoreceptors
• S.diameter=Slow conducting, nociceptors & thermoreceptors
• Positive correlation between axon diameter & conduction velocity

Question 17

Where are the association areas and what is there function?

Answer 17

• Localised to posterior parietal cortex

- Plays role in integration of multimodal senses

Question 18

Describe the primary & secondary somatosensory cortex

Answer 18

• 1= postcentral gyrus, input from thalamus, 3b= info from skin on texture, shape, size
• 2=adjacent to S1 along lateral sulcus, role in sensory & motor integration, corpus callosum inputs to form body image, builds info from multiple body areas