Int 9: Sensory Motor Systems, Pain and Analgesia

Question 1

How to mechanosensors in the skin respond to a) Touch, vibration, stretch, pressure or to b) high pressure, trauma

Answer 1

a) - specialised sensory endings
- can be rapidly adapting (fire only at onset) or slow adapting (maintained)
- Generally A-Beta myelinated axons

b) - Bare nerve endings
- Maintained responses
- A-delta (thinly myelinated) or C (unmyelinated) axons

Question 2

Note: There are a range of 6 thermo-sensitive TRP channels in sensory afferent animals that allow responses to mild to mild cold/warm temperatures or severe noxious heat/cold

Question 3

The touch pathway:
- ascends in the a)_____________
- relays at b)____________ in medulla
- crosses over into c)____________
- relays in the d)___________, projects to e)____________ (mainly contralateral)

• medial lemniscus
• SI cortex
• ipsilateral dorsal column
• cuneate / gracile nuclei
• thalamus

Answer 3

a) ipsilateral dorsal column
b) cuneate/gracile nuclei
c) medial lemniscus
d) thalamus
e) SI cortex

Question 4

The pain pathway:
- cross over in the spinal chord
- ascends in the a)______________________
- relays in the b)___________, projects to the c)____________ (mainly contralateral)

• thalamus
• contralateral ventrolateral column (spinothalamic tract)
• SI cortex

Answer 4

a) contralateral ventrolateral column
b) thalamus
c) SI cortex

Question 5

In relation to muscle and tendons, how do we have proprioception?

Answer 5

• Muscle spindle measure muscle stretch
• Golgi Tendon Organ measures tension

This is largely involved in balance

Question 6

Put the following events that are involved in visual transduction in order

a) Intracellular signalling regulating ion channels in rod cells
b) Light
c) Isomerisation of captive retinal within rhodopsin
d) Action potential firing in optic nerve cells
e) Rhodopsin (a GPCR in rod cells)

After this, there is a 50% crossover of input from each eye at the optic chiasm - info is then projected via lateral geniculate nuclei to the visual cortex

Answer 6

b)
e)
c)
a)
d)

Question 7

In simple terms, how does the hearing system work?

There is lots of crossover in the lower brainstem. Info then projects to Inferior Colliculus then to the Medial Geniculate Nucleus then to Auditory Cortex A1

Answer 7

• Arrays of hairs within the ear tuned to different frequencies
• Oscillations of basilar membrane cause torsion in hairs of sensory cells and rise/fall in membrane potential

Question 8

Vestibular sensory transduction is what allows us to balance.

In a nutshell, there is fluid in the Otolith organs (utricle and saccule). Fluid movement induced stretch of link fibres that causes depolarisation.

There is also connections to muscles and vision to co-ordinate balance. Example: Righting reflex of muscles caused by tilt and Vestibulo-Oculomotor reflex helps maintain direction of gaze during head rotation

Question 9

Movement is controlled via a co-ordination of sensory inputs. Match the area to the functions:

a) Inputs from the balance organs of the inner ear. Controls reflex balance responses in head, neck and lower body.
b) Is VITAL for interpretation of sensory inputs and voluntary control of movement
c) Proprioceptors and touch receptors from muscles, joints and skin. Drive local reflexes and projections to the brain, which can then modulate other reflexes

• Cortex
• Brainstem
• Spinal Chord

Answer 9

a) Brainstem
b) Cortex
c) Spinal chord

Question 10

Match the type of sensors to the function:

a) position the body regions and orientations/balance - largely involuntary reflexes
b) discriminate noxious from innocuous - both reflex and voluntary responses
c) alerting, advisory and some reflex

• Somatosensory mechanical and thermal sensors
• proprioceptors and vestibular sensors
• Telesensors - vision and hearing

Answer 10

a) Proprioceptors
b) Somatosensory sensors
c) Telesensors