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