Exam #5 Info Flashcards
(232 cards)
Cocontraction
Partial or full contraction of muscles on both sides of a joint or “around” a “body segment”
Static Cocontraction
Stiffly lock a joint
Dynamic Cocontraction
Control movement of a joint
Two types of lower motor neurons
Alpha motor neuronsGamma motor neurons
Alpha motor neurons
A-alphaExtrafusalGo to the sarcomeres that make the muscle shorten
Gamma motor neurons
A-gammaIntrafusalGo to the muscle spindles
Motor units
One alpha motor neuron and all muscle fibers it connects to
T/F: One motor unit is either fast or slow twitch; NOT mixed
True
Order of Recruitment (Henneman’s size principle)
Slow twitch firstFast as speed and/or intensity increase
Exceptions to order of recruitment
Need explosive/high level levels of force right away
Gross motor control
Many muscle fibers for each motor axon (LMN)
Fine motor control
Few muscle fibers for each motor axon (LMN)
Alpha-gamma coactivation DEFINITION
Voluntary movement causes UMN to send parallel messages to alpha and gamma motor neurons-Alpha message: move muscle, contract-Gamma message: keep spindle sensitive to stretch
Alpha-gamma coactivation FUNCTION
Keeps spindle sensitive during movement
Sources of convergence of information on alpha motorneurons
1) From an UMN with a message to move (movement pathway)2) From a sensory receptor (mechanoreceptors, spindles, touch/pain receptors)
Motor Neuron Pools
Gray matterVentral hornAxons from a pool project to a single muscle
Vertical organization of Motor Neuron Pools
Single pool may include several spinal levels and several myotomes
Medial Motor Neuron Pools
Axial and proximal muscles
Reciprocal inhibition
When the brain makes one muscle contract, it makes the opposite muscle contract
Reciprocal inhibition connections
Upper motor neurons –> alpha motorneuronsMuscle spindle afferents –> alpha motorneurons
Muscle synergies
Many muscles working together
Muscle synergies are created by…
Activation of multiple motor neurons-brain activates more UMN to contract many LMNBranching of upper motor neurons-UMN branch and go to several musclesInterneuron networks-little networks of neurons that increase connections between muscles
“Normal” muscle synergies
Group of muscles that work under control for a functional outcome
“Abnormal” muscle synergies
Group of muscles that work without control and do not produce a functional outcome