Muscle Function: Analysis and Demonstration Flashcards
Agonist
Primary mover; responsible for the initiation and execution of a specific action at a joint
Antagonist
Opposes or reverses the action of the prime mover
Synergist
Assists the prime mover in its actions
Reciprocal inhibition
Skeletal muscles function in pairs; one of the muscles works as the agonist muscle and the other the antagonist
Electromyography
Analysis of motor unit action potentials (MUAP) and assessment of baseline electrical signal at rest
Recorded using a surface or needle electrode
Can be used to monitor a muscle’s activity during a certain action and to assess integrity of the muscle and nerves supplying it
What is a motor unit?
All the muscle fibers innervated by one nerve
Innervation ratio
The number of muscle fibers innervated by a single axon/motor neuron
- Varies widely between muscle
- Low for fine motor (extra ocular muscles)
- High for gross motor (soles)
What are some of the different kinds of muscle action potentials?
Motor unit action potential
Sensory nerve action potential
Compound muscle action potential
What is the size principle?
Motor units are recruited from smallest to largest size.
How can electromyography be used to diagnose disease?
Tests skeletal muscle fibers
Standard needle electromyography mostly tests type I muscle fibers
How can Nerve conduction studies be used to diagnose disease?
Tests motor, sensory and mixed nerves
What are the three types of contraction?
Isometric
Concentric
Eccentric
Concentric contraction
Limb is shortening
Eccentric contraction
Limb is lengthening
Isometric contraction
No movement but still contracting
When you walk are there more eccentric or concentric contractions?
Eccentric
Name some agonists of wrist flexion.
Flexor carpi radialis
Flexor carpi ulnaris
Flexor digit profundus
Flexor digit sublimis
Name some antagonists of wrist flexion.
Extensor carpi radialis longus and brevis
Extensor ulnaris
Extensor digitorum
Name some agonists of hip flexion.
Iliopsoas Rectus femoris Add long/brev Pectineus Gracilis Sartorius Tensor fasciae latae
Name some antagonists of hip flexion.
Biceps femoris Semitendinosus Semimembranosus Gluteus maximus Adductor magnus
What is upper motor neuron syndrome?
Lesion of upper motor neuron in the CNS
Overactivity – hyperreflexia, spasticity
Underactivity – weakness
No inherent muscle atrophy
What is spasticity?
Velocity-dependent increase in tonic stretch reflex (muscle tone)
What can be used to reduce focal muscle overactivity?
Botulinum neurotoxin
Effects intrafusal and extrafusal muscle
May affect nociceptor pathways via C and A delta fibers and substance P
Can also be used to block salivary and sweat gland
Botulinum toxin mechanism of action
Heavy chain targets presynaptic membrane
Light chain goes in, gets endocytosed and cleaves SNAP-25
Local, temporary cholinergic chemodenervation
