Muscle
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Introduction
Muscle accounts for over one-third of the body's mass and play a number of different key roles.
Types of Muscle
- skeletal muscle
- smooth muscle
- cardiac muscle
Skeletal Muscle
red muscle - lots of microtubules, weak, slow, sustained - S motorneurons
intermediate muscle - intermediated - FR motoneurons
white - few microtubules, strong, fast, fatiguable - FF motoneurons
Smooth Muscle
Cardiac Muscle
Muscle Structure
Fasicles
Fibres
Fibrils
Muscle Tone
tone is passive resistance to movement
Hypertonia
Decreased inhibition of upper motor neurons
spasticity
- suggests upper motor neuron causes
- velocity dependent - going slow doesn't induce it, but going quickly does
- unidirectional (anti-gravity muscles) while rigidity is bi-directional
rigidity
- suggests basal ganglia problems (ie Parkinson's)
- same resistance in all directions
- can be cog-wheeling - likely due to concurrent tremor
Hypotonia
Also known as flaccidity
normally due to lower motor neuron disease, but can also follow acute sponal cord injury for a few days (spinal shock)
Muscle Function
According to Dr Brownstone, the brain views muslces as against gravity - extensors.
extensor muscles are antigravity muscles - gastrocnemius
rest are flexors
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