The muscular system

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Lesson notes

Overview of the Muscular System

The muscular system consists of **over 600 muscles** that work together to enable movement, maintain posture, and perform vital functions like breathing and digestion.
Muscles are attached to bones by tough, fibrous tissues called **tendons**.
When muscles **contract**, they pull on bones, creating movement at **joints** (where two or more bones meet).
Muscles can only **pull**; they cannot push.

Antagonistic Muscle Pairs

Muscles work in **antagonistic pairs**: one muscle contracts (shortens) while the other relaxes (lengthens).
This coordinated action allows for smooth, controlled movement.

Arm Movement: Biceps and Triceps

To **straighten** the arm, the **triceps contract** and the **biceps relax**.
To **bend** the arm, the **biceps contract** and the **triceps relax**.

Leg Movement: Hamstring and Quadriceps

To **bend** the leg, the **hamstring contracts** and the **quadriceps relax**.
To **straighten** the leg, the **quadriceps contract** and the **hamstring relax**.

Cardiac Muscle

The heart is made of **cardiac muscle**, a special type of muscle that works **involuntarily**.
Cardiac muscle contracts **rhythmically and continuously** to pump blood throughout the body.

The Diaphragm and Breathing

The **diaphragm** is a muscle located below the lungs that plays a key role in breathing.
When you **inhale**, the diaphragm **contracts and flattens**, allowing the lungs to expand and fill with air.

Antagonistic muscles of the arm: biceps and triceps.

The diaphragm and its role in breathing.

Slides

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Practice questions

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1.How many muscles are there in the human body?
Easy
- AOver 600
- BApproximately 300
- CExactly 1000
- DOver 200
2.What type of muscle is the heart made of?
Easy
- ACardiac muscle
- BSkeletal muscle
- CSmooth muscle
- DVoluntary muscle
3.Tendons attach muscles to which part of the body?
Easy
- ABones
- BOther muscles
- CSkin
- DJoints
4.When the arm is straightened, which muscles contract and relax?
Medium
- ATriceps contract, biceps relax
- BBiceps contract, triceps relax
- CBoth contract
- DBoth relax
5.What is the role of the diaphragm during inhalation?
Medium
- AIt contracts and flattens
- BIt relaxes and domes upward
- CIt contracts and domes upward
- DIt relaxes and flattens
6.Which of the following statements about antagonistic muscles is true?
Medium
- AThey work in pairs to produce movement
- BThey both contract at the same time
- CThey can both push and pull
- DThey are found only in the arms
7.Which muscles are antagonistic in the leg?
Hard
- AHamstring and quadriceps
- BBiceps and triceps
- CCardiac and smooth
- DDiaphragm and intercostals
8.The statement 'When a muscle contracts, it pushes on the bone it is attached to' is:
Hard
- AFalse, because muscles can only pull
- BTrue, because muscles push bones
- CFalse, because muscles do not contract
- DTrue, because contraction creates push

More questions

9.What is a joint?
Easy
- AWhere two or more bones meet
- BWhere muscles attach to bones
- CA type of muscle
- DA tendon
10.Which muscle is located below the lungs and helps with breathing?
Medium
- ADiaphragm
- BCardiac muscle
- CBiceps
- DTriceps
11.To bend the leg, which muscle contracts?
Hard
- AHamstring
- BQuadriceps
- CBiceps
- DTriceps
12.Which of the following is an example of involuntary muscle?
Hard
- ACardiac muscle
- BBiceps
- CTriceps
- DHamstring
13.The diagram shows a simple model of the arm. A weight is held in the hand with the arm bent at 90°. Which statement correctly describes the forces on the bones when the biceps contracts?
Medium
- AThe biceps pulls the forearm upward, rotating it about the elbow joint.
- BThe biceps pushes the forearm upward, rotating it about the elbow joint.
- CThe biceps pulls the forearm downward, rotating it about the elbow joint.
- DThe biceps pushes the forearm downward, rotating it about the elbow joint.
14.A student measures the maximum force produced by a muscle as it contracts. The force is 50 N when the muscle is at its resting length. When the muscle is stretched to 110% of its resting length, the force increases to 55 N. If the muscle is stretched to 120% of its resting length, what is the most likely force?
Hard
- A60 N
- B55 N
- C50 N
- D65 N
15.Which of the following is a function of the muscular system?
Easy
- APumping blood around the body
- BDigesting food in the stomach
- CFiltering waste from the blood
- DProducing hormones
16.The table shows the number of muscles in different body parts. Which body part has the most muscles?
Medium
- ALegs
- BArms
- CBack
- DFace
17.A student investigates the effect of temperature on the contraction speed of a frog muscle. The muscle is stimulated electrically and the time to contract is measured. Which graph shows the most likely relationship?
Medium
- AA curve decreasing to a minimum then increasing
- BA straight line increasing
- CA straight line decreasing
- DA curve increasing to a maximum then decreasing
18.In an experiment, a muscle is attached to a lever and a weight. The muscle is stimulated and lifts the weight. The work done is calculated as force × distance. If the muscle exerts a force of 10 N and lifts the weight 0.05 m, what is the work done?
Hard
- A0.5 J
- B0.05 J
- C5 J
- D0.2 J
19.The diagram shows a muscle fibre. Which part stores calcium ions that are released during contraction?
Medium
- ASarcoplasmic reticulum
- BMyofibril
- CSarcolemma
- DT-tubule
20.Which type of muscle is found in the walls of blood vessels?
Easy
- ASmooth muscle
- BCardiac muscle
- CSkeletal muscle
- DStriated muscle
21.A student measures the oxygen consumption of a muscle at rest and during exercise. At rest, the muscle uses 0.2 mL O₂ per gram per hour. During moderate exercise, it uses 1.5 mL O₂ per gram per hour. If the muscle mass is 200 g, what is the total oxygen consumption during 30 minutes of exercise?
Hard
- A150 mL
- B75 mL
- C300 mL
- D0.15 mL
22.The graph shows the force generated by a muscle as it is stimulated at different frequencies. What is the frequency that produces the maximum force?
Medium
- A50 Hz
- B20 Hz
- C10 Hz
- D100 Hz
23.Which structure connects a muscle to a bone and is made of tough, fibrous tissue?
Medium
- ATendon
- BLigament
- CCartilage
- DJoint
24.A patient has a condition where the diaphragm is partially paralyzed. Which of the following would be a likely symptom?
Hard
- ADifficulty breathing in
- BDifficulty breathing out
- CInability to bend the arm
- DIncreased heart rate
25.Which of the following statements about muscles is true?
Easy
- AMuscles can pull and push.
- BMuscles can only pull.
- CMuscles can only push.
- DMuscles can neither pull nor push.
26.When the arm is straightened, which of the following occurs?
Medium
- AThe biceps contract and the triceps relax.
- BThe triceps contract and the biceps relax.
- CBoth biceps and triceps contract.
- DBoth biceps and triceps relax.
27.A student investigates the effect of temperature on the contraction speed of a frog muscle. The muscle is stimulated electrically and the time to contract is measured. Which of the following is a controlled variable in this experiment?
Hard
- AThe temperature of the muscle
- BThe contraction time
- CThe strength of the electrical stimulus
- DThe type of frog used
28.In an experiment, a muscle is attached to a lever and a weight. The muscle is stimulated and lifts the weight. The work done is calculated as force × distance. If the weight is 0.5 kg and the lever moves 0.1 m, what is the work done? (Assume g = 10 N/kg)
Hard
- A0.5 J
- B5 J
- C0.05 J
- D50 J
29.A student measures the oxygen consumption of a muscle at rest and during exercise. At rest, the muscle uses 0.2 mL O₂ per gram per hour. During moderate exercise, it uses 0.8 mL O₂ per gram per hour. What is the percentage increase in oxygen consumption?
Hard
- A300%
- B400%
- C75%
- D25%
30.A student measures the maximum force produced by a muscle as it contracts. The force is 50 N when the muscle is at its resting length. When the muscle is stretched to 110% of its resting length, the maximum force is 40 N. Which of the following conclusions is most likely?
Hard
- AThe muscle produces more force when stretched.
- BThe muscle produces less force when stretched.
- CStretching has no effect on force production.
- DThe muscle produces the same force regardless of length.
31.What is the primary function of the muscular system?
Easy
- ATo help the body move, maintain posture, and perform essential functions like breathing and digestion
- BTo pump blood throughout the body
- CTo digest food
- DTo produce hormones
32.How many muscles make up the muscular system?
Easy
- AOver 600
- BExactly 600
- COver 300
- DExactly 500
33.What are tendons?
Easy
- ATough, fibrous tissues that attach muscles to bones
- BTissues that attach bones to bones
- CTissues that attach muscles to muscles
- DTissues that cover the ends of bones
34.Which of the following statements is true?
Easy
- AMuscles can only pull, they cannot push
- BMuscles can both push and pull
- CMuscles can only push, they cannot pull
- DMuscles can neither push nor pull
35.When you inhale, what does the diaphragm do?
Medium
- AContracts and flattens
- BRelaxes and domes upward
- CContracts and domes upward
- DRelaxes and flattens
36.To straighten your arm, which muscles contract and relax?
Hard
- ATriceps contract, biceps relax
- BBiceps contract, triceps relax
- CBoth contract
- DBoth relax
37.To bend your leg, which muscles contract and relax?
Hard
- AHamstring contracts, quadriceps relax
- BQuadriceps contract, hamstring relax
- CBoth contract
- DBoth relax
38.The diagram shows a simple model of the arm with a weight in the hand. The biceps and triceps are shown. Which statement correctly describes the forces when the arm is bent at 90° holding a weight?
Medium
- AThe biceps pulls the forearm up and the triceps pulls it down.
- BThe biceps pushes the forearm up and the triceps pulls it down.
- CThe biceps pulls the forearm up and the triceps relaxes.
- DThe biceps and triceps both pull equally.
39.A student investigates the effect of temperature on the contraction speed of a frog muscle. The muscle is stimulated electrically and the time to contract is measured at different temperatures. The results are shown in the table. Temperature (°C): 10, 20, 30, 40, 50 Contraction time (ms): 120, 80, 50, 40, 90 What is the optimum temperature for fastest contraction?
Hard
- A20°C
- B30°C
- C40°C
- D50°C
40.A student measures the oxygen consumption of a muscle at rest and during exercise. At rest, the muscle uses 0.2 mL O₂ per gram per hour. During moderate exercise, it uses 1.5 mL O₂ per gram per hour. If the muscle has a mass of 100 g, how much more oxygen does it use per hour during exercise compared to rest?
Medium
- A130 mL
- B150 mL
- C170 mL
- D200 mL

Revision notes

## The Muscular System - Over 600 muscles work together for movement, posture, breathing, and digestion. - Muscles are attached to bones by **tendons**. When muscles contract, they pull on bones to create movement at **joints** (where two or more bones meet). - Muscles **can only pull**, not push. So they work in **antagonistic pairs**: one contracts (shortens) while the other relaxes (lengthens). ### Arm Movement (Biceps & Triceps) - **Straighten arm**: triceps contract, biceps relax. - **Bend arm**: biceps contract, triceps relax. ### Leg Movement (Hamstring & Quadriceps) - **Bend leg**: hamstring contracts, quadriceps relax. - **Straighten leg**: quadriceps contract, hamstring relax. ### Other Muscles - **Cardiac muscle**: makes up the heart; works involuntarily, contracts rhythmically to pump blood. - **Diaphragm**: muscle below lungs; when you inhale, it contracts and flattens, allowing lungs to expand. **Key Points**: - Muscles only pull. - Antagonistic pairs enable smooth movement. - Some muscles (like cardiac and diaphragm) work involuntarily.

Tendon: Tough, fibrous tissue that attaches muscle to bone.
Joint: Where two or more bones meet.
Antagonistic pair: Two muscles that work together: one contracts while the other relaxes to produce movement.
Contract: To shorten (as a muscle does when it pulls on a bone).
Relax: To lengthen (as a muscle does when its partner contracts).
Cardiac muscle: Special involuntary muscle that makes up the heart and pumps blood.
Diaphragm: Muscle below the lungs that contracts and flattens during inhalation to allow lungs to expand.

Flashcards

What are the three main functions of the muscular system?

The muscular system helps the body move, maintain posture, and perform essential functions like breathing and digestion.

What are tendons?

Tendons are tough, fibrous tissues that attach muscles to bones.

How do muscles create movement at joints?

When muscles contract, they pull on bones, creating movement at the joints.

What is a joint?

A joint is where two or more bones meet.

Can muscles push?

No, muscles can only pull; they cannot push.

What are antagonistic muscles?

Antagonistic muscles are pairs of muscles that work opposite each other: one contracts (shortens) while the other relaxes (lengthens).

Describe how the biceps and triceps work to straighten the arm.

To straighten the arm, the triceps contract and the biceps relax.

Describe how the biceps and triceps work to bend the arm.

To bend the arm, the biceps contract and the triceps relax.

What are the antagonistic muscles in the leg?

The hamstring and quadriceps are antagonistic muscles in the leg.

Describe how the hamstring and quadriceps work to bend the leg.

To bend the leg, the hamstring contracts and the quadriceps relax.

Describe how the hamstring and quadriceps work to straighten the leg.

To straighten the leg, the quadriceps contract and the hamstring relax.

What type of muscle makes up the heart?

The heart is made up of cardiac muscle.

Is cardiac muscle voluntary or involuntary?

Cardiac muscle works involuntarily; it contracts rhythmically and continuously without conscious control.

What is the diaphragm?

The diaphragm is a muscle located below the lungs that plays an important role in breathing.

Describe how the diaphragm helps during inhalation.

When you inhale, the diaphragm contracts and flattens, allowing the lungs to expand and fill with air.

True or false: When a muscle contracts, it pushes on the bone it is attached to.

False. When a muscle contracts, it pulls on the bone.

True or false: The biceps and triceps are antagonistic muscles.

True.

True or false: The heart is made of cardiac muscle.

True.

True or false: There are over 600 muscles in the human body.

True.

How many muscles are in the human body?

There are over 600 muscles in the human body.

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