Lecture 10 — Muscle Contraction & Muscle Actions

Somatic motor neuron

Neuron that stimulates skeletal muscle

Neuromuscular junction

Synapse between motor neuron and muscle fiber

Motor end plate

Specialized region of muscle membrane at NMJ

Neurotransmitter at NMJ

Acetylcholine

Motor unit

One motor neuron and all muscle fibers it innervates

Recruitment

Increasing muscle force by activating more motor units

All-or-none contraction

Sarcomere contracts completely or not at all

Sarcolemma

Muscle cell membrane

T-tubules

Tunnels that transmit electrical signals into muscle fiber

Sarcoplasmic reticulum

Organelle that stores calcium ions

Role of calcium in contraction

Allows actin and myosin interaction

Energy for muscle contraction

ATP

Concentric contraction

Muscle shortens while producing force

Eccentric contraction

Muscle lengthens while producing force

Isometric contraction

Muscle produces force without changing length

Origin

Muscle attachment that does not move

Insertion

Muscle attachment that moves

Agonist

Primary muscle responsible for movement

Antagonist

Muscle that produces opposite movement

Synergist

Muscle assisting the agonist

Type I muscle fibers

Slow twitch, endurance, high mitochondria

Type II muscle fibers

Fast twitch, high power, fatigue quickly