Muscle Activity
What chemical is released at the neuromuscular junction to start muscle contraction?
Acetylcholine (ACh)
What movement bends a joint and decreases the angle between bones?
Flexion
What term describes the muscle mainly responsible for a movement?
Prime Mover
What large chest muscle acts to adduct and flex the arm?
Pectoralis Major
A patient has difficulty standing on their toes, weak hip stabilization while walking, and struggles to flex the elbow. Using your knowledge of gross anatomy and muscle function, identify three muscles that are likely impaired and explain one main action for each.
Gastrocnemius – plantar flexes the foot (standing on toes)
Gluteus medius – stabilizes pelvis during walking / hip abduction
Biceps brachii – flexes the elbow and supinates the forearm
What ion rushes into the muscle cell to start an action potential?
Sodium
What movement straightens a joint, increasing the angle?
Extension
What do you call muscles that oppose the prime mover?
Antagonists
What shoulder muscle is the prime mover of arm abduction and gives your shoulder its rounded shape?
Deltoid
What autoimmune disease causes weakness because acetylcholine receptors are damaged at the neuromuscular junction?
Myasthenia gravis
What structure connects a motor neuron to a muscle fiber?
Neuromuscular junction
Moving a limb away from the body’s midline is called what?
Abduction
Muscles that help stabilize joints and assist movement are called what?
Synergists
What large back muscle helps extend and adduct the humerus, especially during swimming or pulling motions?
Latissumus Dorsi
What group of three posterior thigh muscles flex the knee and extend the hip?
Hamstrings
According to the sliding filament theory, what two filaments slide past each other to shorten the muscle?
Actin and Myosin
Turning the palm downward is called what?
Pronation
If a muscle name includes “biceps,” how many origins does it have?
Two
What paired abdominal muscle runs vertically down the front of the abdomen and helps flex the vertebral column?
Rectus Abdominus
What muscle stabilizes the pelvis during walking and acts as a hip abductor beneath the gluteus maximus?
Gluteus Maximus
What form of sustained contraction happens when stimuli are so rapid that the muscle cannot relax?
Tetanus (Complete Tetanus)
Standing on your toes is an example of which movement
Plantar Flexion
What term describes muscles that hold a bone steady so movement can occur?
Fixators
Which calf muscle inserts into the heel via the Achilles tendon and is the prime mover of plantar flexion?
Gastrocnemius
What developmental pattern describes how muscle control progresses from head to toe in infants?
Cephalic to caudal development