Reflexes Flashcards
What is a stretch reflex?
It is monosynaptic reflex found in all muscles
What causes a stretch reflex?
A sharp tap to the tendons (which are inelastic) which transfers the force to muscle fibres which stretch and stimulate the spindles
What is the process of the stretch reflex?
Alpha motor neurones are activated and the agonist muscle contracts. The antagonist muscle relaxes as the spindle activates inhibitory interneurones which decreases alpha motor neurones to the antagonists
What is an example of a stretch reflex?
Knee jerk
Can the stretch reflex be overridden?
Yes, if what is being held is of importance due to descending voluntary excitation of alpha motor neurones
What is a GTO mediated reflex?
A polysynaptic reflex which is a result of muscles contracting and pulling on the tendons which increased GT bodies discharge.
What type of interneurone are activated to agonist muscles in GTO mediated reflexes?
Inhibitory (causing contraction)
What type of interneurone are activated to antagonist muscles in GTO mediated reflexes?
Excitatory
What is an example of a GTO mediated reflex?
Clasp-knife reflex
Why are GTO mediated reflexes protective?
Prevents over contraction and the muscle from tearing the tendon insertion points away from the bones
Can GTO mediated reflexes be overridden?
Yes
Where are interneurones involved?
Polysynaptic reflexes
What is the function of interneurone?
They allow a different response from the same sensory information
What type of muscle do interneurones act?
Antagonistic
What is reciprocal inhibition?
When an agonist contracts the antagonists stretches which causes activation of inhibitory interneurone which decrease the activation of alpha motor neurones to the antagonist which then relaxes
What are the 2 types of reflexes?
Ipsilateral (same side) and contralateral (opposite side)
What is the flexor-withdrawal reflex?
It is a polysynaptic reflex that uses information from the nociceptors in skin, muscles and joints and withdraws the body part affected by stimulus
What is the process by which flexor-wirhdrwal reflexes operate?
Sensory stimulus causes an increase in agonist flexor muscles via excitatory interneurones, while inhibitory neurones work on antagonists extensors. If this happens on one leg, then the other leg has to take the strain
How can contralateral muscles exchange strain?
Excitatory interneurones which cross the spinal column cause the extensor muscles to contract while the other interneurones inhibit contralateral flexors
What happens as the pain stimulus is increased?
The spinal spread increases which causes a larger response so more alpha motor neurones are engaged
How is stimulus increased?
Facilitation
What do pain fibres facilitate?
The action of muscle spindles by maintaining the alpha motor neurones in a more depolarised state
