Neuro 7 - Sensory Pathways: Touch and Proprioception

Question 1

What receptors are responsible for the sensory modalities of touch and proprioception?

Answer 1

Mechanoreceptors

Question 2

Describe the structure of mechanoreceptors involved in touch and proprioception?

Answer 2

it is the peripheral termina of the peripheral axon of the primary sensory neuron

Not a separate entity

Question 3

Describe the structure of Pacinian corpuscle and explain how the structure relates to its function.

Answer 3

Axonal ending in the middle, wrapped around concentric circles of epithelial cells

allows the receptor o be sensitive to vibration

Question 4

What is the difference between slow and fast adapting receptors?

Answer 4

Slow - continue to fire impulses as long as the stimulus is present

Fast- - fire at start and end of stimulus

Question 5

What type of receptors are mechanoreceptors - fast or slow adapting?

Answer 5

Mixture of both

Question 6

Describe how sensory neurons vary in their properties.

Answer 6

vary in size and conduction velocity

Question 7

What two ways can axons be classified?

Answer 7

based on diameter
based on conduction velocity

but these are also linked
larger diameter = faster conduction

Question 8

Describe the general structure of sensory neurons that convey touch and proprioceptive information?

Answer 8

Large and have a fast conduction velocity

Question 9

What is a receptive field?

Answer 9

An area of skin that is innervated by one sensory axon and its branches

Question 10

Describe how the receptive fields in the lips and mouth vary from the receptive fields of the upper arm.

Answer 10

Lips and mouth - high density innervation with small receptive fields

Upper arm - low density innervation, with large receptive fields

Question 11

Describe how neurons can code for intensity of a stimulus.

Answer 11

FREQUENCY

Question 12

Which part of the spinal cord carries sensory axons for touch and proprioception?

Answer 12

Dorsal columns

Question 13

What are the bundles of axons within the spinal cord that have come from below/above the waist called?

Answer 13

Above waist = cuneate Fasciculus

Below waist = Gracile Fasciculus

Question 14

Are axons from lower down packed more medially or more laterally?

Answer 14

Lower = medial
Higher = lateral

Question 15

Where do the cuneate and gracile fasciculus neurons synapse?

Answer 15

cuneate and gracile nuclei in the medulla

Question 16

Where does decussation happen in the central pathway?

Answer 16

In the brainstem

Question 17

Which thalamic nucleus is responsible for relaying somatosensory information from the neck down?

Answer 17

Ventero-postero lateral

Question 18

Describe the passage of the third order sensory neuron.

Answer 18

Travels from the ventral postero lateral nucleus in the thalamus to the primary somatosensory cortex

Question 19

What is the main sensory nerve of the face?

Answer 19

Trigeminal nerve

Question 20

Where does the trigeminal nerve enter the brainstem and where does it synapse with the second order neuron?

Answer 20

Pons

synapses at the trigeminal cranial nucleus

Question 21

Describe the passage of this second order neuron.

Answer 21

crosses the midline and join the medial part of the median lemniscus

Question 22

Which thalamic nucleus is responsible for relaying sensory information from the face?

Answer 22

Ventral-Postero-medial

Question 23

What is lateral inhibition?

Answer 23

Each axons has lateral branches that are inhibitory on neighbouring axons
So each axon stimulates a second order neuron and inhibits neighbouring first order neurons

Question 24

What is the point of lateral inhibition?

Answer 24

Improve the resolution of localising the stimulus

Question 25

Name the three parts of the somatosensory cortex.

Answer 25

Primary somatosensory cortex
Secondary somatosensory cortex
Posterior parietal cortex

Question 26

What is the posterior parietal cortex involved in?

Answer 26

Spatial relationships

Question 27

Damage to the touch and proprioception pathway will halt sensory information going up to the primary somatosensory cortex. What effects will this have?

Answer 27

Anaesthesia - complete loss of sensation

Paraesthesia - abnormal sensation

Question 28

What is the most common cause of peripheral neuropathy?

Answer 28

Diabetes Mellitus