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Motor 1
All MovementInvolves therotation of
Skeletal Joints
Joints can rotate along:•One axis (knee)•Two axes (wrist)•Three axes (hip)
Muscles onlyGenerate force When theyContract
So muscles are alwaysArranged in pairs forRotating joints in bothdirections
Note tendons whichAttach muscles to theskeleton
Muscles Contract in Response toAcetyl Choline
Cholinergic Motor neurons make theseconnections
Muscles themselves areMade of fibers
Each fiber contractsIn response to Ach induceddepolarization
Muscle Has Different Fiber Types
Cat Gastrocmenius
Cat Soleus
Contractile Properties of Whole Muscles Vary
Muscles Have Heterogenous Properties
Twitch Contractions
The Motor Unit
Motor Units are Homogenous by Fiber Type
Fiber Types are Adaptive
Conduction Velocities of Alpha-MN Axons
soleus
Gastroc.
The Size Principle
Feedback Signals From Muscle
Muscles also have sensory transducersImbedded in them
Stretch receptors (alsoCalled spindles) haveA firing rate thatIndicates muscle length
The Stretch Reflex Circuit
The Motor Neuronal Pool
The Motor-Neuronal Pool
A pool of motor neuronsIn the spinal cordServes each muscle
These pools form aTopographic map(sort of)
The Law of Combination
-Elwood Henneman