Lecture 4-Sensory System

Question 1

What are modalities?

Answer 1

Unit of sensation, due to different types of receptors

Question 2

What are the modalities associated with the dorsal column pathway?

Answer 2

• fine touch
• 2 point discrimination
• vibration
• proprioception

Question 3

What are the modalities associated with the spinothalamic tract?

Answer 3

• temp
• pain
• pressure/crude touch
• stretch

Question 4

Where is the dorsal column pathway found?

Answer 4

In the dorsal funiculus

Question 5

Where is the spinothalamic system found?

Answer 5

On the cap on the surface of the ventral horn

Question 6

True or false: a strong receptor activation leads to an increased frequency AP

Answer 6

TRUE

Question 7

What are rapidly adapting units?

Answer 7

Good at detecting changes in AP eg rapidly adapting mechanoreceptors in skin

Question 8

What are slowly adapting units?

Answer 8

Frequency of AP stays the same eg nociceptors/pain

Question 9

What is a receptive field?

Answer 9

Region of sensory space in which a stimulus will modify the firing of that neuron (multiple receptors feed into sensory neurone)

Question 10

What is acuity inversely proportional to?

Answer 10

Size of receptive field

Question 11

Where is the cell body of the primary sensory neurone?

Answer 11

Dorsal root ganglion (DRG)

Question 12

Where is the cell body of secondary sensory neurone?

Answer 12

Dorsal horn/medulla

Question 13

Where is the cell body of tertiary sensory neurone?

Answer 13

Thalamus

Question 14

Where does the tertiary sensory neurone project to?

Answer 14

Primary sensory cortex in post-central gyrus

Question 15

True or false: primary sensory neurone decussates

Answer 15

FALSE - secondary decussates

Question 16

In the dorsal column pathway, where does the lower body map to?

Answer 16

Medial portion of tract

Question 17

In the spinothalamic tract, where does the lower body map to?

Answer 17

Lateral parts of tract

Question 18

What is the cuneate nucleus in the dorsal column pathway responsible for?

Answer 18

Upper 1/2 of body

Question 19

What is the gracile nucleus in the dorsal column pathway responsible for?

Answer 19

Lower 1/2 of body

Question 20

What is the name of the pathway in the dorsal column pathway in which the secondary neurones travel?

Answer 20

Medial lemniscus pathway

Question 21

Where does the secondary neurone decussate in the spinothalamic tract?

Answer 21

White ventral commissure

Question 22

In a complete cord hemisection in which a single cord segment is destroyed, which structures are destroyed unilaterally?

Answer 22

• dorsal horn
• ventral horn
• all other cord grey matter
• all white matter pathways
• dorsal and ventral roots

Question 23

What are the signs of Brown-Sequard syndrome?

Answer 23

• ipsilateral complete segmental anaesthesia affecting single dermatome
• ipsilateral loss of dorsal column modalities below the lesion
• contralateral loss of spinothalamic modalities below the lesion

Question 24

Which fibres carry impulses from mechanoreceptors in damaged skin?

Answer 24

A fibres

Question 25

Which fibres carry pain which runs through the spinothalamic system?

Answer 25

C fibres

Question 26

What alleviates pain?

Answer 26

Activation of mechanoreceptors and heat by exciting inhibitory enkephalinergic interneurones in the cord which inhibits secondary spinothalamic neurones

Question 27

How can pain be psychologically inhibited?

Answer 27

Descending inputs from the brain activate inhibitory interneurones