Motor systems

Question 1

definition: motor unit

Answer 1

one alpha motor neuron plus all the skeletal muscle fibers it innervates

Question 2

definition: fasciculation

Answer 2

visible twitches of muscle that can be seen as ripples under the skin - can involve one or more motor units

Question 3

what contributes to the cause of fasciculations?

Answer 3

sensitivity of un-innervated receptors to circulating Ach

Question 4

definition: fibrillation

Answer 4

spontaneous activity within single muscle fibers - not visible clinically

Question 5

what are the symptoms of UMN damage?

Answer 5

1. spasticity 2. overactive DTR 3. Positive Babinski sign

Question 6

what are the effects of a transection of the spinal cord with respect to

Answer 6

1. loss of voluntary movement for muscles innervated by spinal segments below level of transection 2. loss of “true” sensation, anesthesia, for areas innervated by sensory neurons below level of transection

Question 7

what are the INITIAL effects of spinal cord transection?

Answer 7

1. spinal shock 2. flaccid paralysis 3. areflexia 4. loss of autonomic function

Question 8

what are the effects of spinal shock?

Answer 8

initial flaccid paralysis due to damage to descending motor pathways