Test 3 - Ch 13 Flashcards
What are the steps of the motor system to move?
decision - frontal plan - frontal speed and project - BG and cerebellum motor tracts motor neurons
What are all the parts of a muscle fiber
myofibril sarcomeres- contractile -z-line : ends of sarcomere -m-line : what myosin hangs on - titin : rubber band that keeps muscle from overstretching and becoming damaged (goes from one end of sarcomere to other myofilaments -actin : @ end of myosin and climbs when contraction -myosin : attached to m-line
How does a M contract?
A-alpha brings ACL to t-tubule- EPSP - depolarizes
Mm only relax when gas pedal is not pushed
What is occurring when a contracture is present?
Titin does not slack
cross bridges when actin grabs myosin
Total M resistance to stretch?
- Titin - reached elastic limit
- Active contraction - cross-bridges being formed
- Weak actin-myosin bonds - lightly stuck velcro
- Proprioceptive information - m spindles - depolarize motor neurons
Where does a LMN/motor neuron cell bodies lie and where does it synapse?
cell bodies- ventral horn of SC
synapses in M
How are the motor neurons oriented horizontally in the ventral horn?
medial - core and proximal Mm
Lateral- distal Mm
anterior- extensors
posterior - flexors
How are the motor neurons oriented vertically in the ventral horn?
all of cell bodies that contribute to a particular M
cluster into a vertical pool
every spinal level contributes to more than one M
What motor neuron makes Mm contract?
A-Alpha
What motor neuron makes intrafusal fibers maintain sensitivity?
a-gamma
What axon is afferent from M spindle?
1a
What does a motor unit consist of?
A motor neuron and all m fibers it connects to
Describe a slow twitch M fiber. size metabolism tension fatigue
smaller
oxidative
less tension
fatigue resistant
Describe a fast twitch M fiber. size metabolism tension fatigue
large
glycolytic
high tension
easy fatigue
What is fiber placement in gross movement muscles?
many fibers per axon
increase strength, decrease control
What is fiber placement in fine movement muscles?
few m fibers/axon
decrease strength, increase control
What can any 1 Alpha neuron receive convergent information from?
brain and sensory receptor
deep tendon pressure inhibits alpha motor neuron
What is proprioceptive body schema?
self-perpetuation in walking, only need to initiate
need input from GTO
What afferents inhibit the alpha efferent to antagonist?
1a
Fasiculations
quick twitch spontaneous depolarization of a motor neuron (and all fibers) benign - no co-morbidities pathologic - w/co-morbidities quick twitch
myoclonus
whole body jerk
fibrillations
one m fiber spontaneous depolarization
always pathologic
denervated
Tremors
oscillating movements
Signs of LMN lesions - damage to A-Alpha
trauma -sharp
infection - polio - kills cell body in horn
degenerative disorder - ALS - glutamate excitotoxicity
vascular - compromise of Vv supply
tumor (trauma) - peripheral tumors grow on and press N
hypotonic
loss of some a-alpha - spinal N
flaccidity
loss of all m tone -peripheral N
“flaccid paralysis”
loss of m tone and inability to contract
