Lab Quiz 9

Question 1

what are the premotor and primary motor cortexes responsible for?

Answer 1

premotor: motor planning, anatomically part of superior, middle and inferior frontal gyri
primary motor: motor initiation, origin of corticospinal tract, anatomically part of the precentral gyrus

Question 2

which cranial nerves are motor?

Answer 2

CN 3-7 and CN 9-12

Question 3

upper vs lower motor neurons?

Answer 3

upper: from gray matter in the brain and brain stem, these neurons have direct descending projections to lower motor neurons, which are referred to as the descending motor system
lower: have their cell bodies in spinal cord and brain stem nuclei and their axons leave the CNS to reach target skeletal muscles for excitation
upper motor neurons travel through internal capsule to reach lower motor neurons

Question 4

what does an upper motor neuron lesion cause?

Answer 4

spastic paralysis accompanied by severe hypotonia

Question 5

what does a lower motor neuron lesion cause?

Answer 5

affects aons traveling from the alpha motor neurons in neurons in anterior horn to the muscle, causes flaccid paralysis, can no longer generate reflexes

Question 6

what is an extensor/Babinki sign?

Answer 6

when toes fan up in response to the bottom of the foot being touched, indicates a upper motor neuron lesion, Babinski sign is present from infancy to 2 years old