Muscle Function: Analysis and Clinical Demonstration Flashcards
Define an agonist
- “Primary mover”
- Often considered as functional muscle group
- Responsible for the initiation and execution of a specific action at a joint
What is an antagonist?
A muscle that opposes or reverses the action of the prime mover
What are synergists?
Muslces that assist the prime mover in its actions
What is reciprocal inhibition
Skeletal muscle functions usually include pairs of muscles
Depending on the muscle function, one of the paired muscles works as the agonist muscle and the other the antagonist muscle
How does reciprocal inhibition leads to maximal muscle efficiency
- Increased tone in preparation for full activation
- The antagonist muscle prepares to slow down/stop the intended function
- The muscle pair need to coordinate their contractions to avoid muscle injury
What type of inhibition contributes to antagonist suppression during movement?
Group Ia-mediated reciprocal inhibition
Depolarization of all the fibers in a motor unit creates an electrical potential called…
A motor unit action potential (MUAP)
How are MUAPs used in electromyography
MUAPs generated by contraction of an individual muscle can be recorded by using a surface or needle electrode
What is the innervation ratio?
Number of muscle fibers innervated by a single axon/motor neuron
Which types of muscles have a high innervation ratio? Which have a low innervation ratio?
High for gross motor (soleus)
Low for fine motor (extraocular muscles)
What is the size principle?
Smaller fibers are recruited first in a movement and progressively larger fibers are then recruited as needed
Difference between nerve conduction studies and electromyography
Nerve conduction studies test motor, sensory and mixed nerves
Electromyography tests skeletal muscle fibers - most test type I fibers
Types of contraction
Isometric
Concentric
Eccentric
In a normal gait, are their more eccentric or concentric contractions?
Eccentric
Wrist flexion agonists
- Flexor carpi radialis
- Flexor carpi ulnaris
- Flexor digit profundus
- Flexor digit sublimis
Wrist flexion antagonists
- Extensor carpi radialis longus and brevis
- Extensor ulnaris
- Extensor digitorum
Hip flexion agonists
- Iliopsoas
- Rectus Femoris
- Adductor longus and brevis
- Pectineus
- Gracilis
- Sartorius
- Tensor fasciae latae
Hip flexion antagonists
- Biceps femoris
- Semitendinosis
- Semimebranosis
- Gluteus maximus
- Adductor magnus
What is upper motor neuron syndrome?
Lesion of the uppor motor nueron in the central nervous system (brain or spinal cord)
UMN syndrome
Positive signs:
Negative signs:
Positive signs (overactivity): Hyperreflexia; spasticity
Negative signs (underactivity): Weakness
What is spasticity?
- Velocity dependent increase in tonic stretch reflex (muscle tone)
- Hyperexcitability of the stretch reflex
- One component of the upper motor neuron syndrome
Uses of botulinum neurotoxin
- Injections can be used to reduce focal muscle overactivity
- Affects both intrafusal and extrafusal muscle
- Can be used to block salivary and sweat glands
- Used to treat numerous disorders: dystonia, spasticity, opthalmologic, GI/GU, dermatologic and pain
Botulinum toxin can affect nociceptor pathways via…
C and A delta fibers and substance P
Types of Electromyography
- Surface EMG
- Needle EMG
- Tests type I fibers
