Mechanoreception

Question 1

What is mechanoreception?

What is exteroception?

Proprioception?

Touch?

Answer 1

• detection of mechanical stimuli
• peripheral receptor = mechanoreceptor - activated by a mechanical event
• adequate stimulus: mechanical distortion: pressure, vibration and tension

Exteroception: give information about things coming into contact with the body

Proprioception: awareness of position

Touch: sensory experience when mechanoreceptors are excited - involves CNS

Question 2

Give some examples of oro-facial mechanoreceptors:

Answer 2

Mucosa and skin:

• food texture
• important for mastication

PDL: forces on teeth

Muscles: muscle spindles –> muscle length

Joint receptors: joint position and movement

Question 3

What is the effect of stimulating a mechanoreceptor?

What are the types of mechanoreceptor?

Answer 3

• sensation of touch
• reflexes: jaw muscle reflexes, salivary reflexes (chewing gum)
• interact/modulate other sensory modalities - the effect of rubbing a painful area (gate control)

Types of mechanoreceptor:

• physiological classification: adaptation properties, receptive field size
• anatomical classification: what they look like down the microscope

Question 4

What nerve fibre is likely to be attached to a mechanoreceptor?

How do rapidly adapting and slowly adapting mechanoreceptors behave to force?

What is the receptive field?

What does a slow receptive field allow for?

Answer 4

• A-beta fibres, smaller than A-alpha but bigger than c and a-delta fibres

Rapidly adapting: getting used to the state very quickly, responds when force is applied and when removed

Slow adapting: responds throughout the duration of a stimulus

Receptive field: area of mucosa where a stimulus will affect the receptor e.g. patch of skin that responds to a poke

Small receptive field = localisation

Question 5

What are PDLMs and what roles do they have?

What nerve endings, afferents and cell bodies are in PDLMs?

Where is innervation most dense?

What is the adequate stimulus?

Answer 5

Periodontal ligament Mechanoreceptors (PDLMs)

• exteroceptive role and proprioceptive role

Nerve endings: ruffini

Afferents: a-beta axons ~300 per tooth

Cell bodies: V ganglion, mesencephalic nucleus

• no branched axons between adjacent teeth PDLs –> easy to localise (TTP)
• innervation density higher at apex

Adequate stimulus = tension

Question 6

What is the sensory pathway of mechanoreception?

Answer 6

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