Exam 2 Opening Questions

What is the definition of a reflex?

involuntary response trigger by a specific stimulus

What is the term for a diminished reflex?

hyporeflexia (hypoactive reflex)

What is the term for an exaggerated reflex?

hyperreflexia (hyperactive reflex)

What are the five components of the reflex arc?

sensory receptor, afferent neuron, central processing unit, efferent neuron, muscle/effector

What type of proprioceptor/receptor is involved in a monosynaptic reflex?

muscle spindle

When stimulating/measuring the H-reflex, why is the electrical stimulation applied to both the sensory and motor neurons instead of just the sensory neurons?

in peripheral nerves, both sensory and motor axons run through it

What specifically causes the H-reflex?

stimulation of Ia afferents

What is the pathway of the H-reflex through the nervous system?

Ia afferents -> spinal cord (CPU) -> alpha motoneurons -> muscle (effector)

What specifically causes the M-response/wave?

stimulation of alpha motoneurons

What is the pathway of the M-response through the nervous system?

alpha motoneurons -> muscle

Why does the H-reflex diminish when a high intensity electrical stimulation is applied to a peripheral nerve?

action potential collision

Why does the H-reflex diminish when high frequency stimulation is applied to a peripheral nerve?

central synapse refractory period

What happens to the H and T-reflex when the patient voluntarily activates the agonist muscle before the reflex is stimulated? What happens when they voluntarily activate the antagonist muscle?

it gets bigger because it has more excitability in the alpha MNs; it gets smaller because of reciprocal inhibition

What are 3 differences between monosynaptic and polysynaptic reflexes?

1. mono- is 1 synapse, poly- is many synapses

2. mono- is specific to only 1 type of receptor (muscle spindle), poly- will have multiple different types of receptors

3. mono- only excites 1 muscle or muscle group, poly- will excite multiple

What happens at the threshold of the tonic stretch reflex?

reflexive recruitment of alpha MNs in the muscle group being stretched or lengthened

What happens to muscle spindle activity when a muscle lengthens?

increases

What happens to the activity of the Ia afferents when a muscle lengthens?

increases

What happens to the activity of the alpha motoneurons due to the activity of the Ia afferents?

increases

What happens to muscle force due to the activity of the alpha motoneurons?

increases

What happens to the H-reflex when vibration is applied to a muscle? Why does the H-reflex decrease?

weaker/decreases; presynaptic inhibition

What is a pre-programmed reaction/long loop reflex?

semi-automatic reaction to a stimulus

What is the latency of a pre-programmed reaction?

50 - 100 ms

Put the following responses in order from the fastest to the slowest: pre-programmed reaction, voluntary correction, reflex

reflex, pre-programmed reaction, voluntary correction

What type of stimulus can trigger a pre-programmed reaction?

any type of perturbation