Upper and lower motor neuron disorders - Pickering Flashcards
What are the 5 basic steps for spinal reflex as a basis for motor control?
1) Sensory neuron
2) Action potential fires
3) Synapsing with interneuron (intergration)
4) Motor neuron
5) Muscle/gland contracts/secrete
What is the definition of a reflex?
a fast, predictable automatic response to a change in the environment/stimulus
What are the 5 events that occur in the patellar tap reflex?
1) Tap quadriceps tendon = stretch of quadriceps muscle
2) Activation of the muscle spindle and increased firing of 1a afferent fibres
3) Afferent terminal synapses with and excites the alpha motor neuron
4) Increased alpha motor neuron efferent axon activity
5) Contraction of agonist homonymous muscle - kicking of the leg
In the patella reflex, what muscles are activated and what muscles are inhibited?
Activated: quadriceps
Inhibited: Hamstrings
What is meant by the term ‘agonist homonymous’?
supportive muscle and same muscle from which the afferent arose
How are the hamstring muscles inhibited in the patella reflex?
via 1a inhibitory neuron of motor neuron innervating antagonist muscle group
The patella and bicep reflex come under the category of what reflex?
Myotatic strech reflex
What is another name for the golgi tendon relfex?
The inverse myotatic reflex
What is the function of the golgi tendon reflex?
Protects muscle to avoid injury
Provides a tension feedback mechanism
What are the 4 steps of the golgi tendon reflex?
1) Golgi tendon organ becomes excited
2) Increased firing of 1b afferent fibres
3) Indirect inhibition via inhibitory interneuron of a alpha motor neuron
4) Relaxation of homonymous muscle
Explain how the inverse myotatic reflex works in leg muscle groups
1) Increased muscle tension = activation of tendon organ
2) Excites 1b afferents
3) Indirect inhibition via inhibitory interneuron of motor neurons = homonymous muscle relaxation
3) Indirect excitation of motor neurons innervating antagonist muscle groups
In what situation would the crossed extensor/flexor withdrawal reflex occur?
Standing on a pin
Ipsilateral = flexion
Contralateral = extension
The interneuron that supplies the motor neurons of the contralateral side cross where?
via a commisure
What are the 5 steps involved in the crossed extensor/flexor withdrawal reflex?
1) Increased activity in A-delta & C afferents
2) Polysynaptic activation of ipsilateral flexors
3) Polysynaptic inhibition of ipsilateral extensors
4) Polysynaptic inhibition of contralateral flexors
5) Polysynaptic activation of contralateral extensors
What type of fibre is the sensory afferent for myotatic (stretch) reflex?
1a
