LMN Reflexes Flashcards
What are the 5 functional components of a reflex arc?
1) Stimulus eg. pain
2) AP along afferent spinal nerve
3) Integration centre within spinal cord - pass from sensory to motor
4) Motor neuron AP
5) Muscle/ gland responds
In a myotactic stretch reflex, activation of the muscle spindle causes AP firing in what kind of nerve fibre?
1a afferent
In the myotactic stretch reflex, contraction of the agonist muscle is a result of increased activity in which type of neuron?
Alpha motor neuron
The myotactic stretch reflex requires 2 components, how many neurons is involved in each?
1) Contraction of agonist muscle (2 neurons - no interneuron)
2) Reciprocal inhibition of antagonist muscle groups (3 neurons requires an inhibitory interneuron)
In reciprocal inhibition of the antagonist muscle groups during the myotatic reflex, what type of fibre is the interneuron?
1a inhibitory neuron
The patellar tap reflex is an example of what kind of reflex?
Myotatic reflex
The Golgi tendon reflex is an example of what kind of reflex?
Inverse myotatic reflex
With increased muscle tension, Golgi tendon organ excitation causes increased firing in what king of neuron?
1b afferent
How many neurons are involved in the inverse myotactic reflex?
3 - an inhibitory interneuron is involved
Does the inverse myotatic reflex lead to contraction or relaxation of homonymous muscle (the one the signal came from)?
Relaxation - it is a protective mechanism
The inverse myotatic reflex leads to decreased firing in what kind of nerve fibre via an interneuron?
alpha motor neuron fibre
How does the inverse myotatic reflex affect antagonist muscle groups and how?
Contraction of antagonist muscle groups
Excitation of alpha motor neuron via an excitatory interneuron
The myotatic stretch reflex and the inverse myotatic reflex are ipsilateral or contralateral?
Ipsilateral - all work on the same side from which the stimulus came
What is the principle of the crossed extensor/ flexor withdrawal reflex?
Stimulus such as pain causes withdrawal on the ipsilateral side (flexion) and extension on contralateral side so don’t fall over
In the crossed extensor/flexor withdrawal reflex, on activation of the cutaneous nociceptor there is increased activity in which 2 kinds of fibres?
A-delta and C afferents
What is the effect on the ipsilateral flexors in the withdrawal reflex?
Polysynaptic activation of ipsilateral flexors (via excitatory interneuron)
What is the effect on the ipsilateral extensors in the withdrawal reflex?
Polysynaptic inhibition of ipsilateral extensors (via an inhibitory interneuron)
How many neurons are involved in the crossed extensor/ flexor withdrawal reflex to the contralateral side?
4 (2 interneurons)
What is the effect on the contralateral extensors in the withdrawal reflex and how?
Polysynaptic excitation of the contralateral extensors via 2 excitatory interneurones
What is the effect on the contralateral flexors in the withdrawal reflex and how?
Polysynaptic inhibition of the contralateral flexors via an excitatory neuron followed by an inhibitory neuron
What type of fibre is the sensory afferent in the myotatic reflex?
1a
What is the sensory stimulus in the myotatic reflex?
Change in muscle length
What are the 3 proposed functions of the myotatic reflex?
1) Antigravity
2) Posture
3) Movement
What type of fibre is the sensory afferent in the inverse myotatic reflex?
1b
