intro motor system Flashcards Preview

MEDICAL PHYS EXAM FINAL > intro motor system > Flashcards

Flashcards in intro motor system Deck (15)
Loading flashcards...
1
Q

define alpha motoneurons

A
  • also called LMN, can be called anterior or ventral horn cell when in spinal cord
2
Q

define final common path (FCP)

A
  • Lower motor neurons are only link between central nervous system and skeletal muscles
  • thus they are COMMON PATH by which all other parts of the nervous system control skeletal muscles
3
Q

define motorneuron pool

A
  • all of the motor units that serve a single muscles are considered a motor unit pool
4
Q

define motor unit

A
  • one alpha motor neuron plus ALL the skeletal muscles fibers its innervates
5
Q

define poliomyelitis

A
  • affects the size of the motor unit
  • can result in very large motor units in affected muscles
  • due to surviving motor units ADOPTING orphaned muscle fibers
  • Post-polio syndrome partially caused by stress on surviving motor neurons b/c nerve-muscles connects undergo repeated remodeling with denervation and reinnervation
6
Q

define fibrillations

A
  • spontaneous activity within single muscle fibers
  • not visible clinically since they are too small to be seen as movement through the skin
  • can only be recognized by electromyography
7
Q

define fasiculation

A
  • visible twitched of muscle that can be seen as ripples under the skin
  • can involve one or more motor units
8
Q

describe graded muscle contractions

A
  • Increase muscle force production via:
  • -> recruitment or multiunit summation (increase number of motor units activated)
  • -> Increase firing rate of activated motor units
9
Q

What size motor units are expected in extra-ocular eye muscles, muscles controlling fingers, large postural muscles, and limb muscles that have been affected by polio

A
  • Extra-ocular eye muscles/muscles controlling individual fingers HAVE MANY SMALL MOTOR UNITS
  • Large postural muscles/limb muscles that have been affected by polio = LARGE MOTOR UNITS
10
Q

affects of LMN damage

A
  • profound muscle atrophy
  • decreased muscle tone/flaccid paralysis or weakness
  • weak or absent stretch reflexes (HYPOREFLEXIA)
  • Fibrillations present
  • fasciculations present
  • Negative for Babinski
11
Q

affects of UMN damage

A
  • Hypertonic muscles (spasticity, clasp-knife effect, clonus)
  • hyperreflexia (deep tendon reflexes)
  • positive babinski sign
  • fibrillations and fasiculations are ABSENT
12
Q

Immediate effects of spinal cord trasected

A
  • spinal shock = initial flaccid paralysis due to damage to descending motor pathway
  • flaccid paralysis
  • areflexia (loss of reflexes)
  • loss of autonomic function
13
Q

What are permanent effects of spinal cord transection

A
  • loss of voluntary movement for muscles innervated by spinal segments below level of transection
  • loss of TURE sensation, anesthesia, for areas innervated by sensory neurons below level of transaction
14
Q

describe the patients changes over time

A
  • recovery from spinal shock usually takes 1 to 6 weeks
  • -> patient shows HYPERREFLEXIA, different types of reflexes return at different times.
  • After spinal shock, SLOW RETURN of reflex activity in the following order:
  • -> Babinski sign > flexor spasms > alternate flexor and extensor spasms > predominant extensor spasms > release phenomena > spastic paralysis
15
Q

babinski sign

A
  • AKA estensor plantar response
  • BIG TOE DORSIFLEXES and other toes FAN OUT (Positive sign)
  • indicates damage to UMN in the thoracic or lumbar region or brain disease constituting damage to the corticospinal tract
  • Normal primitive reflex seen in infants, disappears at around 1 yo