A&P 10-3 Muscle physiology

Define motor unit

One motor neuron and all the muscle fibers it innervates

______ motor units have fine control of motion.

small

_______ motor units develop bigger strength of contraction

large

1

latent period

2

contraction

3

Relaxation

latent period

Neurotransmitter binds to the receptors and opens sodium channels

latent period

Action potential spreads through sarcolemma

Depolarization reaches T-tubules

latent period

Sarcoplasmic reticulum releases calcium into sarcoplasm

latent period

Calcium binds to troponin

latent period

Tropomyosin moves off the active sites on actin molecules.

latent period

Myosin heads bind to actin and deliver a power stroke

contraction

ATP breaks the cross-bridge. Myosin heads are cocked and form new cross-bridges

contraction

Calcium is pumped back into sarcoplasmic reticulum

relaxation

Elastic component stretches the muscles

relaxation

Single stimulus causes a brief muscle contraction

twitch

Increase in tension (force) of contraction is observed with recurring stimulation of the muscle

treppe

Muscle relaxes only partially before being stimulated and contracting again

Unfused (incomplete) tetanus

Multiple frequent stimuli result in muscle contraction without attempt to relax between the stimuli

Fused tetanus

isotonic eccentric

isotonic concentric

isometric

Fulcrum

point of support

Effort

muscle that does the work

Load

weight or resistance against which the work is done