muscle function

Question 1

agonists vs antagonists vs synergists

Answer 1

Agonist- primary mover, responsible for the initiation and execution of a specific action at a joint, often considered as a functional muscle group (elbow flexors)

Antagonists: oppose or reverse the action of the prime mover

Synergists- assist the prime mnover in its actions

Question 2

Reciprical inhibition

Answer 2

Ensures smooth movement of a joint
sk musc typically function in pairs for maximal muscle efficiency speed control. (Agonist: increases its tone in prep for full activation) (Antagonist muscle prepares to slow down the intended function), the muscle pair needs to coordinate their contractions to avoid muscle injury

In neurologically intact (Ia afferent enters the sp cd, synapses on the alpha motor neuron and causes the agonist to contract; at the same time the other branch of the I a afferent synapses on the Ia inhibitory inhibotory interneuron which synapse on the alpha motor neuron

In neurologic comprimised pts: lack of reciprocal inhibition (lack of descending inhibtion–> spasticity)

Question 3

Planes of movement

Answer 3

Frontal/ coronal: abduction/adduction

Sagittal: fex and extend

Transverse: internal and external rotation

Question 4

types of contraction

Answer 4

Isotonic: concentric (muscle shortens), eccentric (muscle elongates)

Isometric (muscle length remains the same)

Eccentric contractions: greatest amount of forse with less metabolic energy

20 yo with Achilles tendinophathy: eccentric exercises
75 yo with CAD w/ MI should avoid isometric exercises

Question 5

EMG

Answer 5

certain disease processes, nerve compression, hereditary or acquired diseases or myopathy would result in alteration of the normal recorded electrical signals and recruitment patterns

These can be diagnosed using EMG tests sk musc mostly type 1 slow twitch and nerve conduction studies that test motor sensory and mixed nerves

When individual axon depolarized–> AP propagates down the nerve, depolarization of all fibers in motor unit creates an electrical potential (Motor unit action potential MUAP)

Analysis of MUAPs and assessment of baseline electrical signal at rest serves as the foundation for EMG

Question 6

Anatomy of motor unit

Answer 6

Innervation ration: number of muscle fibers that belong to a single axon (low for fine motor, and high for gross motor)

Higher innervation ratio the greater the force generated by that motor unit
All muscle fibers innervated by one unit are of the same fiber type

Question 7

Henneman size principle

Answer 7

at first a few motor units are recruited then more and more

Nerve conduction studies (component of EMG, studies assess the integrity of the peripheral nervous system)

Compound muscle AP (NCS

Sensory nerve AP

Question 8

spasticity

Answer 8

positive sign of UMN

Velocity dependent increase in tonic stretch reflex, muscle tone, hyper excitability of stretch reflex

decreased reciprocal inhibition