H-reflex

Question 1

efferent nerve across the ……….. to cause a muscle action potential (MAP)

Answer 1

neuromuscular junction

Question 2

Compound Muscle Action Potential

Answer 2

currents associated with each muscle fibre action potential combined- are graded (different amplitudes)

Question 3

Why is the EMG of irregular shape?

Answer 3

because individual muscle fibre action potentials, which sum to make the EMG, fire asynchronously

Question 4

the amplitude of the signal is related to …..

Answer 4

number of muscle fibres that are activated at any one time and hence to the tension developed

Question 5

reflex

Answer 5

sudden stretching of the muscle spindles in the muscle connected to the tendon causes afferent nerve impulses to pass into the SC to the synapses that connect with motorneurones.

The motorneurones are activated and the whole muscle twitches

Question 6

Why is the response fast?

Answer 6

there is only one synapse in the circuit

Question 7

what do we record in EMG?

Answer 7

recording the Soleus muscle, stimulating the Achilles tendon

Question 8

Do tendon jerk vary from one individual to the next?

Answer 8

yes

Question 9

What is the latency?

Answer 9

the time it takes for the action potentials to travel from the soleus to the recording electrodes

Question 10

How can you calculate the conduction velocity?

Answer 10

divide the total distance travelled by action potentials / latency