Chapter 07: Muscular System

The Neuromuscular Junction: 1) Action potential comes down axon terminal 2. Arrives at synaptic end bulb 3. Synaptic vesicles release Acetylcholine 4. Ach diffuses across synaptic cleft 5) Binds to receptors on motor end plate 6. Triggers action potential in sarcolemma 7. Acetylcholinesterase breaks down acetylcholine to stop the process

What is each muscle classified as?

an organ.

What surrounds the whole muscle?

Epimysium

Whats a tendon?

Tendons are strong cords of connective tissue that connect muscle to bone.

What is the basic unit of skeletal muscle?

muscle fiber

What is the function of myofibrils?

bundles of protein filaments that are responsible for muscle contraction.

What is the role of acetylcholine at the neuromuscular junction?

binds to receptors on the motor end plate to trigger an action potential in the muscle fiber.

What causes rigor mortis after death?

calcium ions leak out of the sarcoplasmic reticulum, allowing myosin heads to bind to actin when ATP synthesis has ceased.

What is the difference between isotonic and isometric contractions?

Isotonic contractions involve muscle changing length; isometric contractions involve tension without changing length.

What is muscle tone?

involuntary contraction of a small number of motor units that keeps muscles firm.

What are the two primary types of muscle fatigue?

Physiological inability to contract and contracture.

Define atrophy

“Wasting away” of muscles

Aponeurosis

: a strong sheath of connective tissue that extends from muscle to muscle

Fascicle

group of skeletal muscle fibers

Myofibrils

bundle of protein filaments inside muscle fibers

Thin filaments

Actin

Thick filaments

Myosin

1 thick filament=

6 thin filaments

Regulatory proteins

turn contraction on and of

Structural proteins

provide proper alignment, elasticity and extensibility

Motor unit

motor neuron and the muscle fibers it stimulates

Neuromuscular junction

site where axon terminal of a motor neuron meets the muscle fiber sarcolemma

Contraction

shortening or increase in tension

Tension

a stretching or pulling force

Twitch

brief contraction of all the muscle fibers in a motor unit in response to a single action potential

Latent period

time during which impulse is traveling along sarcolemma and down T tubules to SR

Wave summation

the increased strength of a contraction resulting from the application of a second stimulus before the muscle has completely relaxed

Tetanus

when a muscle fiber is stimulated so rapidly it does not relax between stimuli

Recruitment

process of increasing the number of active motor units

Asynchronous motor unit summation

motor units are activated on a rotating basis

Spasm

: involuntary contraction of single muscle caused by rapid firing of motor neuron

Tremor

rhythmic, involuntary contraction of opposing muscle groups

Flaccid paralysis

paralysis with loss of muscle tone

Spastic paralysis

paralysis with rigidity

Muscle fatigue

physiological inability to contract

Contracture

state of continuous contraction