Revision

Question 1

What is active vs passive eruption?

Answer 1

Active - bodily movement of the tooth
Passive - uncovering of the tooth by apical gingival migration

Question 2

Summary of eruption theories?

Answer 2

1. Root formation (push)
2. Bone formation (push)
3. Fluid pressure (push)
4. PDL (pull)

LIKELY THEORY: Pull (by PDL fibroblasts), push (by hydrostatic pressure)

Question 3

Mechanoreceptors: rapidly adapting vs slowly adapting

Answer 3

Rapidly adapting: only responds during change (when force is being applied or when its being removed)

Slowly adapting: remain firing during the application of the stimulus (information about steady state)

Question 4

Rapidly adapting mechanorecpetor

Answer 4

Meissner’s corpuscle
Pacinian corpuscle

Question 5

Slow adapting mechanoreceptor

Answer 5

Merkel cells
Ruffini ending

Question 6

Classification of mechanoreceptors

Answer 6

Rapidly adapting - RA I, RA II (small vs large receptive field)
Slow adapting - SA I, SA II (small vs large receptive field)

Question 7

Sensory pathway

Answer 7

1. Mechanoreception (transduction of stimulus —> propagation along primary afferent nerve)
2. Processing at first synapse (trigeminal nucleus)
3. Processing in thalamus
4. Conscious perception (somatosensory cortex)

Question 8

What is unique about the mesencephalic nucleus?

Answer 8

Collection of cell bodies in the central nervous system (every other one is in the periphery)

Proprioception nerves have their cell bodies in the CNS.

Question 9

Trigeminal pathways

Answer 9

1. Primary afferent cell bodies: V ganglion, mesencephalic nucleus (PDL)
2. Synapse: mainly in main sensory nucleus, project to spinal V nuclei as well
3. Project to : sensory cortex via thalamus

Question 10

Processing at the first synapse

Answer 10

Surround inhibition ( pre-synaptic inhibition) - “sharpens” touch perception

Question 11

How does surround inhibition work?

Answer 11

• Three nerves, point comes in, most activation on the central nerve, but some small distortion on the surrounding nerves.
• Surround inhibition, interneurones that are inhibitory, ‘cancel out’ the surrounding nerves to allow for sharpening of touch: able to discriminate between more specific points.

Achieve the best surround inhibition by: lots of nerves, small receptive fields that dont overlap.