Sensory Processing

Question 1

How is the selectivity of afferent fibres partly conferred?

Answer 1

protein macromolecules

Question 2

What are C-MH fibres?

Answer 2

C-fibres responsive to heat and mechanical stimuli

Question 3

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

Answer 3

42-45º

Question 4

Where is elkin1 present?

Answer 4

Aβ , Aδ and some C afferent fibres

Question 5

What is elkin1 important for?

Answer 5

non-noxious stimuli response

Question 6

What is Elkin1 a modulator of?

Answer 6

non-painful cutaneous responses

Question 7

What are TRP receptors for?

Answer 7

sensing noxious thermal stimuli

Question 8

What is mechanical noxious stimulus mainly driven by?

Answer 8

other molecules not present on Aβ afferent fibres

Question 9

Why do different afferents show selectivity to different stimuli?

Answer 9

because of protein macromolecules present on the associated receptors

Question 10

What is adequate stimulus property?

Answer 10

the kind of stimulus to which a receptor is especially sensitive

Question 11

What are label lines?

Answer 11

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

Question 12

How do warm excited neurons respond to warmth?

Answer 12

by increasing their activity

Question 13

What is TRPV1 important for?

Answer 13

response in the painful range

Question 14

What is TRPM8 important for?

Answer 14

response in the non-painful range

Question 15

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

Answer 15

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

Question 16

What does PMBC do?

Answer 16

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

Question 17

What is disinhibition?

Answer 17

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

Question 18

What is disinhibition important for?

Answer 18

motor control, sensory processing, and emotional regulation

Question 19

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

Answer 19

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

Question 20

What is frequency code?

Answer 20

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

Question 21

What is population code?

Answer 21

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

Question 22

What is the duration of an AP signalled by?

Answer 22

the speed of adapting

Question 23

What are rapidly adapting receptors important for?

Answer 23

detecting changes in stimuli, such as the onset or removal of pressure e.g. pressure to the skin

Question 24

What is the receptive field?

Answer 24

the area monitored by a receptor

Question 25

Where is the receptor and afferent most strongly excited?

Answer 25

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

Question 26

How can a signal be further modulated?

Answer 26

inhibition in the CNS

Question 27

What do first order neurons do?

Answer 27

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

Question 28

What do second order neurons do?

Answer 28

contact other neurons and also inhibitory neurons via a side branch

Question 29

What do inhibitory neurons do?

Answer 29

contact second order neurons in adjacent areas

Question 30

What is stimulus location encoded and sharpened by respectively?

Answer 30

• encoded by receptive field
• sharpened by inhibition

Question 31

What is the first sensory relay of the CNS?

Answer 31

spinal cord

Question 32

What does a cross section of the spinal cord show?

Answer 32

• 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 33

Where do pain pathways cross the midline?

Answer 33

in the spinal cord

Question 34

Where do fine touch pathways cross the midline?

Answer 34

in the medulla

Question 35

Where do sensory pathways synapse?

Answer 35

in the thalamus

Question 36

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

Answer 36

transmitting touch, pressure, and proprioception

Question 37

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

Answer 37

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 38

What is the pain (spinothalamic) pathway responsible for?

Answer 38

transmitting pain, temperature, and crude touch sensations

Question 39

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

Answer 39

1. nociceptors in the skin or tissues detect painful stimuli and generate nerve signals
2. these nerve signals travel through Aδ /C afferent fibres and enter the spinal cord, where they immediately synapse with neurons in the dorsal horn
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, acting as a relay station, forwards the signals to the primary somatosensory cortex, where the sensation is processed and perceived

Question 40

What does lesion in the dorsal column result in?

Answer 40

deficit in sensations of fine touch

Question 41

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

Answer 41

loss of pain