Sensory Receptors Flashcards
What are the 5 main classes of sensory receptors found in the body?
- mechanoreceptors
- chemoreceptors
- nociceptors
- electromagnetic receptors
- thermoreceptors
Name the 3 touch receptors in the skin
Pacini’s corpuscle
Meissner’s corpuscle
Merkel discs
Name the stretch receptor in the skin
Ruffini corpuscle
Describe pacini’s corpuscle
- largest mechanoreceptor
- onion-like encapsulation of nerve endings
- found in deep layers of dermis and detects high frequency (40-500Hz) vibrations
- alpha/beta fibres - glabrous and hairy skin
- rapidly adapting due to slick viscous fluid between layers
- low activation threshold
Describe meissner’s corpuscle
- encapsulated nerve endings similar to Pacini’s but much smaller
- stacks of discs interspersed with nerve endings found between dermal papillae
- detects touch, flutter and low frequency vibrations
- alpha/beta fibres - glabrous skin
- rapidly adapting
- low activation threshold
Describe Merkel discs
- non-encapsulated nerve endings consisting of specialised epithelial cell and nerve fibres
- found just under skin surface e.g. finger tips
- good discrimination and detects static touch and light pressure
- alpha/beta fibres, all skin types
- slowly adapting and low activation threshold
- work with Meissner’s corpuscles to detect texture
- much better than meissner’s and pacini’s corpuscles at detecting pressure
what information do muscle spindles provide?
main proprioceptors that provide information about the state of musculature.
Where are muscle fibres found?
They lie within muscle in parallel with skeletal muscle fibres, more are found when the muscle is involved in fine motor control.
How are muscle spindles innervated?
innervated by gamma motor neurons (efferent) and group Ia and II afferent fibres. Afferents respond to muscle stretch while gamma efferent activity regulates sensitivity of the spindle.
What are muscle fibres made up of?
2 intrafusal fibres:
- nuclear bag fibres
- nuclear chain fibres
When are primary afferents activated?
primary afferents are associated with rate of change so are activated during contraction/stretching
When are secondary afferents activated?
secondary afferents are associated with static changes in length so whether the end muscle length is longe or shorter than the original muscle length before contraction or stretching.
What do GTOs provide information about?
The force of muscle contraction
How do GTOs work?
As the tendon is pulled, it stimulates the free encapsulated nerve endings which is what generates an action potential.
Which fibres are associated with GTOs?
Afferent Ib fibres
