Motor Control Flashcards
Where are MN for particular muscle are clustered in groups with associated gamma neurons? What is another name for this cluster?
Ventral horn
Lamina IX
AKA MN POOL
Somatotopic MN arrangement in ventral horn?
Extensors - ventral Flexors - dorsal Trunk - medial Axilla - mid Extremities - lateral
How does threshold compare for large vs small motor units?
Low for small
High for large
How does muscle spindle input compare for large vs small motor units?
Much input for small
Little input for large
How does amt of capillaries compare for large vs small motor units?
Many for small
Few for large
Hennemens size principle dictates that smaller neurons are recruited first. Recruitment of individual MNs progresses from sm to lg in stereotypic fashion except in ____________ type movements in which all units recruited nearly simultaneously.
Ballistic
What percent of most everyday movements do smaller motor units contribute?
40%
Active factors in muscle stiffness?
Actin and mysosin cross bridging during contraction
Intrinsic factors in muscle stiffness?
Weak actin myosin bonds at rest. Longer duration, more bonds.
Passive factors in muscle stiffness?
CT like Titin: keeps sarcomere from being pulled apart when muscle is stretched and keeps myosin in center of sarcomere.
What factor contributes to normal muscle stiffness?
Titin.
Type Ia quick stretch NOT activated by slow stretch. Normally type II stretch response NOT activated. Weak actin myosin bonds give way.
Describe the characteristics of abnormal stiffness due to UMN lesion.
Inc active factors of hyperreflexia
Inc UMN activity -> Hyperactive quick stretch reflex (+DTR)
Slow stretch reflex may manifest
Disuse can lead to contracture and more weak actin myosin bonds
Describe the characteristics of abnormal stiffness due to contracture.
Loss of sarcomeres -> muscle shortens
Less Titin -> remaining Titin stretches more (passive factor)
More actin myosin bonds (intrinsic bonds)
Reduced muscle stiffness corresponds with reduced DTR (hyporeflexia). What else?
LMN lesion: less actin myosin bonds to LMN: less intrinsic factor
Dec UMN activity: dec active factors
What is spinal shock called?
Diaschesis
In acute SC injury what happens to resting membrane potential? Why?
Diaschesis is due to inability of membrane to reach threshold. CNS Lesion results I’m decreased EPSPs.
Voluntary movement (automatic, routine, unique) is ___________ while reflexive movement is ___________.
Adaptive (closed loop)
Stereotyped (open loop) -> same output every time
What type of movement is a “helper” and what type of movement is primarily responsible for motor control?
Reflexive helps
Voluntary is responsible
True or false: you can consciously inhibit all reflexes.
False. Can inhibit some but not all reflexes.
What factors contribute to information planning of proprioception and kinesthesia (the schema that dictates motor plan creation and adaptation)?
Muscle spindles
GTOs
Joint receptors
Cutaneous receptors
Feed forward is associated with _________ loop.
Open
Feedback is associated with _________ loop.
Closed
Which loop requires real time adaptation and adjustment? How long?
Closed. Occurs at least 150-200 ms.
Which loop is preprogrammed and too fast to use sensory info?
Open.
GTOs can facilitate extensor muscle spindles during stance phase and inhibit the same muscle spindles in swing phase. This is an example of what response?
Bimodal response.
Networks of spinal INTERNEURONS that activate LMN in reciprocal patterns of flex/ext for walking are called:
CPGs : central pattern generators
CPGs adapt based on _________ input and are driven by __________.
Sensory input
Higher centers
Crossed effects where activity on one side of spinal cord affects activity on other side is due to:
Central pattern generators
