Oral Receptors Flashcards
Why is it important to know about receptors in dentistry?
1) Malocclusion:
- CNS will detect + correct
- both upper and lower jaw
2) Bruxism:
- awareness of where jaw is
- drugs, iatrogenic
3) Orthodontics:
- chewing pattern must be re- programmed
You have to move teeth and do things so slowly, not only because you may destroy structure but your brain needs time to reprocess that.
4) TMJ disorders:
- trigeminal (sensory V3)
5) Pain!
- oral cavity a common site for pain
What are exteroreceptors, proprioceptors, and interoceptors?
Classified depending on their physical location throughout the body
Exteroceptors - just beneath the skin
Proprioceptors - within muscles and joints
Interoceptors - within the viscera
Exteroceptors - 1° for pain, touch temperature and pressure (nociceptor, mechanoreceptor, thermoreceptor)
Proprioceptors - position & movement, vibration and pressure, pain
Interoceptors - pressure (distention), pain
All of them can transmit pain.
Fastest neurotransmition for proprioceptors, NOT FASTEST FOR PAIN
How are receptors differentiated?
Receptors are differentiated on the basis of whether they are encapsulated or not
Encapsulated
Meissner's (mechanoreceptors) Pacinian (mechanoreceptors) Ruffini's (mechanoreceptors) Golgi Tendon (proprioceptors) Muscle spindle (proprioceptors)
Non-encapsulated
Merkel’s Disks (mechanoreceptors)
Free nerve endings
How are peripheral nerves classified?
Characteristics of peripheral nerves: They are classified according to different criteria: size conduction velocity whether possess a myelin covering
Basic Rule
Fibres that are required to transmit important information do so at much faster rates
Applies to both sensory and motor nerves
What are the motor and sensory neurons?
Only sensory nerves get numeric names (e.g. type 2 affterent)
If you’re using alphabetic it can be either motor or sensory.
Group 1 is faster because it has more myelin.
C type fibers have no myelin so they’re the slowest.
Most autonomic fibers are B type fibers, they are all motor (they aren’t on this chart!!!!!)
ABC motor and sensory. A alpha (Group I) is proprioceptors of skeletal muscle.
Abeta (group II) is mechanoreceptors of skin.
Adelta (Group III) is pain, temperature
C (group IV) are temperature, pain, and itch. Unmyelinated and therefore the slowest.
So once again Sensory fibres from the soma (Somatic afferents) have been classified according to where the information comes from (basically this is a physiological distinction), so what do types I - IV deliver?
Type I - muscle spindle / Golgi tendon endings
Type II - m. spindle / touch / pressure receptors
Type III - myelinated pain / temperature receptors
Type IV - unmyelinated pain / temp. receptors
What are the fastest transmitting fibers?
Muscle spindle and golgi tendon organ are the fastest transmitting.
What is the motor system and what is it divided into?
There is also a system that conveys motor information
This motor division is subdivided into
somatic efferent (muscles) and
visceral efferents (controlling glands, smooth muscle)
What is an example of a visceral efferent motor nucleus that is important for dentistry?
Inf. / Sup. Salivatory Nucl.
What is the most complicated/complex receptor and why?
The most complicated / complex receptor is the muscle spindle
This is because it has both a sensory component and a motor component
All other receptors have only the sensory component
What do neuromuscular spindles provide sensory data for?
Provide sensory data for
- reflex adjustments of muscle tonus
- contribution of cerebellum to motor function
- sensory / motor integration at cortical level
What is the organization of a muscle spindle?
Organization:(Fig 5 -1)
- C.Tissue capsule surrounding a group (2 - 10) of specialized muscle fibres (intrafusal fibres)
- Spindles exist in the body of the muscle itself amongst the extrafusal fibres (in parallel)
- Each spindle is expanded at its central region into a fluid filled bag
- have both motor input and sensory output
What are the two types of intrafusal fibers?
Nuclear - bag
Nuclear – bag
Thicker
3 - 4 nuclei clustered in the bag region
more centrally located within spindle
Nuclear - chain
Nuclear – chain
Thin
Nuclei distributed down the equatorial plane of each cell
more peripherally located in spindle
What is an intrafusal fiber?
But What is an Intrafusal fibre?
It is a specialized muscle / receptor cell, shaped like a spindle that has contractile regions on either end and a relatively more central region that is contacted by sensory nerve fibres and is non-contractile
What are the two different types of sensory nerve endings associated with the intrafusal fibers?
primary endings (annulospinal); and
secondary endings (flowerspray)
Report the length of muscle spindle back to the CNS
- under resting conditions, these sensory axons send ongoing information to the CNS that is mostly unconscious
these axons increase their firing rate when the muscle spindle is stretched )
Difference between the two endings is that the annulospinal are faster than the flowerspray.
What are primary endings in neuromuscular spindles?
Primary endings
Also called annulospiral endings
Classified as Type Ia afferent endings - very rapid conduction velocities
Associated with the central portions of both the nuclear - bag and nuclear - chain fibres
Annulospiral Endings - Ia afferents - Very rapid conduction velocities of sensory information – more centrally located and innervates both bag and chain
