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Flashcards in Muscle Function Review - Ketchum Deck (9)

Distinguish between a muscle agonist and synergist.

Synergists are "secondary movers", and serve to assist the agonist in its actions.


What is the function and physiologic basis of reciprocal inhibition?

Functions to coordinate contraction for smooth activation and stopping, and to avoid muscle injury.

Antagonizing muscles are reciprocally inhibited by group Ia fibers.


What does electromyograpy assess?

Assess muscle function and nerve signaling (MUAPs & conduction).


What is the size principle?

In muscle contractions, the smallest motor units (slow-twitch) are recruited first.


What are the three types of contraction?

Isometric (no change in length, eg pushing a static object)

Concentric (shortening of muscle fiber length)

Eccentric (contraction under lengthening)


Recall the agonists and antagonists involved in wrist flexion.

Agonists: FCR(L/B), FCU, FDP, FDS.

Antagonists: ECR(L/B), Extensor ulnaris, extensor digitorum.


Recall the agonists and antagonists involved in hip flexion.

Agonists: Iliopsoas, rectus femoris, S/G/T, TFL, adductors longus/brevis.

Antagonists: Semitendinosus, Semimembranosus, Biceps femoris, Gluteus maximus, Adductor magnus.


Recall the clinical signs of an upper motor neuron lesion.

Hyperreflexivity, spasticity (positive signs)

Weakness (negative signs) *without atrophy


How does botulinum toxin impede muscle contraction?

Its heavy chain cleaves synaptobrevin, resulting in loss of ACh presynaptic release at the NMJ.