Biceps brachii: Front of the upper arm; bends the elbow Triceps brachii: Back of the upper arm; straightens the elbow Deltoid: Shoulder muscle that lifts the arm Pectoralis major: Large chest muscle Latissimus dorsi: Broad muscle of the back Trapezius: Muscle across the upper back and neck Abdominals: Muscles of the belly that help the trunk bend and twist Gluteus maximus: The largest muscle in the body, in the buttock Quadriceps: Four muscles at the front of the thigh that straighten the knee Hamstrings: Muscles at the back of the thigh that bend the knee Gastrocnemius: The big calf muscle Soleus: Calf muscle lying below the gastrocnemius Tibialis anterior: Muscle on the front of the shin Sartorius: Long strap-like muscle of the thigh Masseter: Chewing muscle in the jaw Orbicularis oculi: Muscle that closes the eyelids Diaphragm: Muscle that helps you breathe Intercostals: Muscles between the ribs Rotator cuff: Group of shoulder muscles that stabilize the joint Achilles tendon: Strong tendon that connects the calf muscles to the heel Skeletal muscle: Voluntary muscle attached to bones; striped Smooth muscle: Involuntary muscle in organs such as the stomach Cardiac muscle: Muscle of the heart Voluntary muscle: One you can control Involuntary muscle: One that works without you thinking Tendon: Connects muscle to bone Ligament: Connects bone to bone Contraction: When a muscle shortens Muscles can only: Pull; they cannot push Antagonistic pair: Two muscles that work in opposite ways, like biceps and triceps Flexor: A muscle that bends a joint Extensor: A muscle that straightens a joint Muscle fiber: A long muscle cell Myofibril: Thread-like part inside a muscle fiber that contracts Actin and myosin: Proteins that slide to make muscles contract ATP: The energy molecule muscles use Lactic acid: A by-product that can build up in tired muscles Muscle tone: The small constant tension in resting muscles Atrophy: Muscle shrinking from not being used Hypertrophy: Muscle growing larger from use Cramp: A sudden painful tightening of a muscle Sprain: An injury that stretches or tears a ligament Strain: An injury that stretches or tears a muscle or tendon Warm up: Gentle exercise before activity to prepare muscles Protein: A nutrient that helps build and repair muscle Fast-twitch fibers: Muscle fibers that contract quickly for sprints Slow-twitch fibers: Muscle fibers that work for a long time without tiring How many muscles do people have, about?: More than 600 Which muscle in the body never rests?: The heart Neuromuscular junction: Where a nerve meets a muscle to tell it to contract Extraocular muscles: The six muscles that move each eye Sphincter: A ring-shaped muscle that opens and closes an opening Peristalsis: Waves of smooth muscle squeezing food along Sarcomere: The basic contracting unit of a muscle fiber Free flashcards from Peabody at peabody.kids/flashcards/bio-muscles