Sensory Processing

Question 1

What are C-MH fibres?

Answer 1

C-fibres responsive to heat and mechanical stimuli

Question 2

What is the temperature at which sensation becomes noxious to humans and animals?

Answer 2

42-45º

Question 3

Where is elkin1 present?

Answer 3

Aβ , Aδ and some C afferent fibres

Question 4

What is Elkin1 a modulator of?

Answer 4

non-painful cutaneous responses

Question 5

What are TRP receptors for?

Answer 5

sensing noxious thermal stimuli

Question 6

Why do different afferents show selectivity to different stimuli?

Answer 6

because of protein macromolecules present on the associated receptors

Question 7

What is adequate stimulus property?

Answer 7

the kind of stimulus to which a receptor is especially sensitive

Question 8

What are label lines?

Answer 8

the primary afferents and their associated receptors important for encoding the nature of the stimulus

Question 9

How do warm excited neurons respond to warmth?

Answer 9

by increasing their activity

Question 10

What is TRPV1 important for?

Answer 10

response in the painful range (hot temperatures)

Question 11

What is TRPM8 important for?

Answer 11

response in the non-painful range (cool temperatures)

Question 12

What happens to warm inhibited sensory neurons when they are cooled and warmed?

Answer 12

• cooled = increase in activity of primary afferent
• warmed = decrease in activity of afferent i.e. no AP discharged

Question 13

What does PMBC do?

Answer 13

block TRPM8 channels and affect the ability of animals to detect warmth

Question 14

What is disinhibition?

Answer 14

the reduction or removal of inhibitory control within neural circuits, leading to an increase in the activity of certain neurons or pathways

Question 15

What is disinhibition important for?

Answer 15

motor control, sensory processing, and emotional regulation

Question 16

What 4 properties of a signal can an AP encode and what concept is associated with each?

Answer 16

• quality - label line
• intensity - frequency and population code
• duration - slowly adapting receptor
• location - receptive field

Question 17

What is frequency code?

Answer 17

the number of APs; relates to the strength of the stimulus

Question 18

What is population code?

Answer 18

the number of receptors activated; proportional to the force of contact

Question 19

What is the duration of an AP signalled by?

Answer 19

the speed of adapting

Question 20

What are rapidly adapting receptors important for?

Answer 20

detecting changes in stimuli, such as the onset or removal of pressure

Question 21

What is the receptive field?

Answer 21

the area monitored by a receptor

Question 22

Where is the receptor and afferent most strongly excited?

Answer 22

at the point of contact i.e. point of maximum force

Question 23

How can a signal be further modulated?

Answer 23

inhibition in the CNS

Question 24

What do first order neurons do?

Answer 24

enter into the spinal cord and provide input to second order neurons

Question 25

What do second order neurons do?

Answer 25

contact other neurons and also inhibitory neurons via a side branch

Question 26

What do inhibitory neurons do?

Answer 26

contact second order neurons in adjacent areas

Question 27

What is stimulus location encoded and sharpened by respectively?

Answer 27

• encoded by receptive field
• sharpened by inhibition

Question 28

What is the first sensory relay of the CNS?

Answer 28

spinal cord

Question 29

What does a cross section of the spinal cord show?

Answer 29

• grey matter rich in neurons
• white matter rich in axons
• dorsal horn in grey matter
• dorsal column in top of white matter
• ventrolateral column in bottom of white matter

Question 30

Where do pain pathways cross the midline?

Answer 30

in the spinal cord

Question 31

Where do fine touch pathways cross the midline?

Answer 31

in the medulla

Question 32

Where do sensory pathways synapse?

Answer 32

in the thalamus

Question 33

What is the touch (dorsal column) pathway responsible for?

Answer 33

transmitting touch, pressure, and proprioception

Question 34

What are the 5 steps of the touch (dorsal column) pathway?

Answer 34

1. sensory receptors in the skin detect touch, pressure, or body position changes and generate nerve signals
2. nerve signals travel through afferent fibres and enter the spinal cord through the dorsal column on the same side of the body
3. the signals continue upward and reach the medulla, where they synapse with neurons in the dorsal column nuclei (gracile and cuneate nuclei)
4. neurons in the medulla send their axons across to the opposite side of the brain, forming the medial lemniscus pathway
5. the signals travel to the thalamus, which acts as a relay station, and then project to the primary somatosensory cortex, where the touch information is processed and perceived

Question 35

What is the pain (spinothalamic) pathway responsible for?

Answer 35

transmitting pain, temperature, and crude touch sensations

Question 36

What are the 5 steps of the pain (spinothalamic) pathway?

Answer 36

1. nociceptors in the skin or tissues detect painful stimuli and generate nerve signals
2. nerve signals travel through Aδ /C afferent fibres and enter the spinal cord, where they synapse with dorsal horn neurons
3. neurons in the dorsal horn send their axons across to the opposite side of the spinal cord, where they join the spinothalamic tract
4. the signals ascend through the spinothalamic tract, passing through the brainstem and reaching the thalamus
5. the thalamus forwards the signals to the primary somatosensory cortex, where the sensation is processed and perceived

Question 37

What does lesion in the dorsal column result in?

Answer 37

deficit in sensations of fine touch

Question 38

What does damage to the anterolateral (spinothalamic) tract result in?

Answer 38

loss of pain