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50 free Muscular System trivia questions with answers — science & nature quiz, new questions added Aug 2026.
The muscular system is the organ system of skeletal, cardiac and smooth muscle that moves the body, holds posture, pumps blood and generates most of our heat. Adults have more than 600 skeletal muscles, and the word itself comes from the Latin for little mouse. This quiz covers the three muscle types and what makes each one striated or involuntary, the sliding filament model with actin, myosin, calcium and ATP, fast- and slow-twitch fibers, how muscles are named, the biggest, smallest, longest and busiest muscles, tendons and the diseases that attack muscle. About a third of the questions are classroom-easy, a third are medium and the rest are for anatomy students. Every answer is checked against reference anatomy pages.
30 of 50 questions with answers and explanations. Play the quiz
Q 01How many distinct types of muscle tissue does the human body have?
Three
Skeletal, cardiac and smooth, and only the first is under voluntary control.
Q 02Roughly how many muscles does an adult human body contain?
Over 600
The exact count varies with the method used to count them.
Q 03Which organ system joins with the muscular system to form the musculoskeletal system?
The skeleton
Tendons connect the two, letting muscles pull on bones to create movement.
Q 04Which muscle type can work completely on its own, without the nervous system?
Cardiac
Its rhythm is set by the sinus node, which the autonomic nervous system only influences.
Q 05Which muscle type is non-striated?
Smooth
It lines organs and vessels and contracts slowly but strongly.
Q 06What are the basic building blocks of striated muscle tissue called?
Sarcomeres
Myofibrils are made of sarcomeres, and a contraction shortens every sarcomere at once.
Q 07Which theory best explains how muscle fibers contract?
Sliding filament model
Actin and myosin filaments overlap and slide toward each other within the sarcomere.
Q 08Which two proteins slide past each other to shorten a muscle?
Actin and myosin
Myosin forms the thick filaments and actin the thin ones.
Q 09Which molecule powers the swivelling of the myosin heads during contraction?
ATP
Used ATP becomes ADP, which muscles must constantly recharge.
Q 10Which ion is released from the sarcoplasmic reticulum to trigger contraction?
Calcium
It uncovers the binding sites on actin, then gets pumped back into storage when the muscle relaxes.
Q 11What fast-acting stored chemical helps regenerate ADP back into ATP in muscle?
Creatine phosphate
Its stores last only about ten seconds of all-out effort but refill within five minutes.
Q 12What neurotransmitter is released at the neuromuscular junction to fire a skeletal muscle?
Acetylcholine
It binds to receptors on the muscle cell and sets off the electrical changes that release calcium.
Q 13A fault at the neuromuscular junction causes the prolonged contractions of which disease?
Tetanus
A loss of function at the same junction produces paralysis instead.
Q 21Which tiny skin muscles make body hair stand up?
Arrector pili
They are the reason for goosebumps.
Q 22Which fiber class is slow-twitch, red and rich in myoglobin and mitochondria?
Type I
It sustains aerobic activity, which is why endurance athletes have more of it.
Q 23Which is the fastest-contracting muscle fiber class found in humans?
Type IIx
Some older books confusingly called it type IIB, a fiber humans do not actually express.
Q 24Why do rodents have such pale flesh?
Q 14A nerve cell plus all the muscle fibers it controls is called what?
A motor unit
Fine movements use few motor units; powerful ones recruit many.
Q 15Which part of the brain mostly coordinates motor units for fluid, unconscious movement?
Cerebellum
It is why you can drive a car without thinking about each muscle.
Q 16What connects a muscle to a bone?
A tendon
Ligaments, by contrast, connect bone to bone.
Q 17Roughly what share of a healthy young adult's body weight is skeletal muscle?
About 40%
Men average about 61% more skeletal muscle than women in Western populations.
Q 18The word muscle comes from the Latin musculus, meaning what?
Little mouse
A flexed biceps was thought to look like a mouse's back; Greek mys also means both.
Q 19What is the striped middle layer of the heart wall called?
Myocardium
The epicardium sits outside it and the endocardium inside.
Q 20Heart muscle cells connect at branching junctions known as what?
Intercalated discs
Skeletal muscle is arranged in regular parallel bundles instead.
Mostly type IIb white muscle
Type IIb is anaerobic, glycolytic and poor in myoglobin.
Q 25Muscle tissue is roughly how much denser than fat?
About 15%
Muscle is about 1.06 kg per liter against roughly 0.92 for fat.
Q 26About what share of the soleus muscle is slow-twitch type I fiber?
80%
The eye's orbicularis oculi is only about 15% type I, and the quadriceps about 52%.
Q 27Chimpanzee muscle is about 67% fast-twitch; how much more power does it produce than human muscle?
1.35 times
Humans win instead at aerobic tasks like walking long distances.
Q 28About how many muscle fibers does a young adult male's biceps contain?
253,000
A single 10 cm fiber in it can hold as many as 3,000 nuclei.
Q 29What is the cell membrane of a muscle fiber called?
Sarcolemma
The cytoplasm inside is the sarcoplasm, and the nuclei are pressed flat against the membrane.
Q 30Which dormant muscle stem population under the basement membrane supplies new nuclei for repair?
Satellite cells
Exercise or injury activates them to supply new nuclei for growth and repair.