Upper and lower motor neurone disorders Flashcards
What 3 things is the brain involved in?
- initiation
- integration
- co-ordination
What 2 things is the spinal cord involved in?
- simple reflexes
2. pattern generation
What is the proposed function of the myotatic (stretch) reflex? (3)
- antigravity
- posture
- movement
What is the proposed function of the inverse myotatic reflex? (2)
- tension feedback
2. overload protection
What is the proposed function of the flexor withdrawal reflex? (2)
- damage limitation of avoidance
2. maintained balance on limb withdrawal
What are the 5 functional components of the reflex arc?
- pain
- AP fires
- Integration
- motor neuron
- muscle/gland responds
What is a reflex?
a fast, predictable automatic response to a change in the environment or a stimulus.
How many synapses does monosynaptic integration involve and what is the speed of transmission like?
HOW MANY
- 1
SPEED
-rapid
How many synapses does polysynaptic integration involve and what is the speed of transmission like?
2 or more synapses
Slower but more complex
What is another name for the patellar tap reflex?
myotatic stretch reflex
What are the sequence of events involved in the patellar tap reflex? (5)
- tap quadriceps tendon and stretch of quadriceps muscle
- activation of the muscle spindle and increased firing of 1a afferent
- afferent terminals synapse directly with and excite the alpha motor neuron - it is a monosynaptic reflex
- increased alpha motor neuron efferent axon activity
- contraction of the agonist homonymous muscle - muscle from which afferent arose
What happens to the antagonist muscle groups during a myotatic reflex?
reciprocal inhibition
- one muscle is activated and he other one isn’t
What does tapping the patellar tendon activate and what does this lead to? (2)
ACTIVATES
Ia afferent
- direct excitation of motor neurons innevrating agonist (extensor) muscle groups
- indirect inhibition via the Ia inhibitory interneuron of motor neurons innvervating antagonist (flexor) muscle groups
What does addition of a load lead to in the myotatic stretch reflex in arm muscle groups? (3)
- stretch of the flexor biceps brachii and activation of the Ia afferent
- direct excitation of agonist (flexor) muscle groups (biceps)
- indirect inhibition via the Ia inhibitory interneuron of antagonist (extensor) muscle groups (triceps brachii)
What is another name for the golgi tendon reflex?
the inverse myotatic reflex
What does the golgi tendon reflex provide?
a tension feedback mechanism
What does increased muscle tension lead to in the golgi tendon reflex? (4)
- golgi tendon excitation
- increased firing in Ib afferent
- Indirect inhibition via an inhibitory interneuron (disynaptic link) to the alpha motor neuron
- relaxation/inhibition of the homonymous muscle
What doe sin creased muscle tension lead to in the inverse myotatic reflex in leg muscle groups?
- activates the tendon organ and excites Ib afferents
- this leads to indirect inhibition via an inhibitory interneuron of motor neurons innervating the homonymous muscle and relaxation
- simultaneously there is indirect excitation of motor neurons innervating antagonist muscle groups
Where is the input from in the crossed extensor/ flexor withdrawal reflex?
nociceptor afferent
What is inhibited and excited contralaterally in the crossed extensor/ flexor withdrawal reflex?
FLEXORS
- inhibited
EXTENSORS
- excited
What is inhibited and excited ipsilaterally in the crossed extensor/ flexor withdrawal reflex?
FLEXORS
excitation
EXTENSORS
inhibition
What happens on activation of the cutaneous nociceptor in the crossed extensor/flexor (nociceptive) withdrawal reflex? (5)
- increased activity in A-delta and C afferents
- polysynaptic activation of ipsilateral flexors
- polysynaptic inhibition of ipsilateral extensors
- polysynaptic inhibition of contralateral flexors
- polysynaptic excitation of contralateral extensors
What is the sensory afferent for the following:
- myotatic (stretch) reflex
- inverse myotatic
- flexor withdrawal (x3)
- myotatic (stretch) reflex
- 1a - inverse myotatic
- 1b - flexor withdrawal
- A-delta
- C
- Group III/IV
What is the sensory stimulus in the following:
- myotatic (stretch) reflex
- inverse myotatic
- flexor withdrawal
- myotatic (stretch) reflex
- change in muscle length - inverse myotatic
- change in muscle tension - flexor withdrawal
- painful or damaging stimuli
