LMN reflexes

Question 1

In motor neurons what is the function of the brain & spinal cord?

Answer 1

• Brain= Initiation, Integration, Co-ordination

- SC=Simple reflexes, pattern generation

Question 2

What is the proposed function, sensory afferent & sensory stimuli of myotatic reflex?

Answer 2

• Posture
• Movement
• Antigravity
• 1a
• Change in muscle length

Question 3

What is the proposed function, sensory afferent & sensory stimuli of an inverse myotatic reflex?

Answer 3

• Tension feedback
• Overload protection
• 1b
• Change in muscle tension

Question 4

What is the proposed function, sensory afferent & sensory stimuli of a flexor withdrawal reflex?

Answer 4

• Damage limitation of avoidance
• Maintained balance on limb withdrawal
• A-delta, C, group III/IV
• Painful or damaging stimuli

Question 5

What is the definition of a reflex?

Answer 5

A fast, predictable automatic response to a change in the environment or a stimulus

Question 6

What are the types of integration that can occur?

Answer 6

• Monosynaptic=1 synapse, rapid

- Polysynaptic=2 or more synapses, slower more complex

Question 7

What does addition of a load to the arm lead to?

Answer 7

• Stretch of flexor biceps brachii & activation of the 1a afferent
• Direct excitation of agonist (flexor) muscle group-biceps
• Indirect inhibition via 1a inhibitory interneuron of agonist muscle group (extensor)-triceps

Question 8

What does the golgi tendon provide

Answer 8

Tension feedback mechanism

Question 9

What does an increased muscle tension lead to in a golgi tendon organ?

Answer 9

• Golgi Tendon Organ excitation
• Inc firing in Ib afferent
• Indirect inhibition via an inhibitory interneuron (disynaptic link) of the motor neuron
• Relaxation/inhibition of the homonymous muscle

Question 10

If you stand on a pin with your right foot, what needs to happen to lift your foot up? What type of reflex is this?

Answer 10

• Crossed extensor/flexor withdrawal reflex
• Inc activity in A-delta &c afferents
• Ipsilateral polysynaptic excitation of flexors & polysynaptic inhibition of extensors
• Contralateral polysynaptic inhibition of flexors & excitation of extensors
• Ensures that when leg is lifted you don’t fall over-maintains balance

Question 11

What is activated by tapping the patella tendon?

Answer 11

1a afferent fibres