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Questions and Answers
Which type of lever has the fulcrum located between the effort and the load?
Which type of lever has the fulcrum located between the effort and the load?
Skeletal muscles operate under involuntary control.
Skeletal muscles operate under involuntary control.
False
What term describes the end of a muscle attached to the moving bone?
What term describes the end of a muscle attached to the moving bone?
insertion
The _____ is the force required to move a load.
The _____ is the force required to move a load.
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Match the lever types with their characteristics:
Match the lever types with their characteristics:
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What is the primary function of skeletal muscles mentioned in the content?
What is the primary function of skeletal muscles mentioned in the content?
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Muscles can only perform one type of action at a time.
Muscles can only perform one type of action at a time.
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What are two main functions of muscles in the muscular system?
What are two main functions of muscles in the muscular system?
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Which muscle acts as the agonist during elbow flexion?
Which muscle acts as the agonist during elbow flexion?
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The triceps brachii must contract for the biceps brachii to move the forearm.
The triceps brachii must contract for the biceps brachii to move the forearm.
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What is the function of fixators in muscle movement?
What is the function of fixators in muscle movement?
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The muscles arranged at angles to each other in the abdominal region provide _________ to the visceral organs.
The muscles arranged at angles to each other in the abdominal region provide _________ to the visceral organs.
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Match the muscles to their primary actions:
Match the muscles to their primary actions:
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What happens when both the biceps brachii and triceps brachii contract simultaneously?
What happens when both the biceps brachii and triceps brachii contract simultaneously?
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Synergists are the muscles that oppose the action of the agonist.
Synergists are the muscles that oppose the action of the agonist.
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Name one function of facial muscles.
Name one function of facial muscles.
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The _________ muscle elevates the mandible and is essential for chewing.
The _________ muscle elevates the mandible and is essential for chewing.
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What type of muscle arrangement helps to provide additional protection to the abdominal viscera?
What type of muscle arrangement helps to provide additional protection to the abdominal viscera?
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The rectus abdominis muscle is responsible for the '6-8 pack' appearance.
The rectus abdominis muscle is responsible for the '6-8 pack' appearance.
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What does the term 'RMA' stand for in the context of muscle action?
What does the term 'RMA' stand for in the context of muscle action?
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The ________ ligament helps to connect the frontal and occipital bellies of the occipitofrontalis muscle.
The ________ ligament helps to connect the frontal and occipital bellies of the occipitofrontalis muscle.
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Match the following muscles with their actions:
Match the following muscles with their actions:
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What is the primary function of the diaphragm?
What is the primary function of the diaphragm?
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The trapezius muscle only permits elevation of the scapula.
The trapezius muscle only permits elevation of the scapula.
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Name one muscle that assists in abduction of the scapula.
Name one muscle that assists in abduction of the scapula.
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The _____ is the largest muscle in the lower limb responsible for leg extension at the hip joint.
The _____ is the largest muscle in the lower limb responsible for leg extension at the hip joint.
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Match each muscle to its primary action.
Match each muscle to its primary action.
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Which muscle is known as the 'swimmer’s muscle'?
Which muscle is known as the 'swimmer’s muscle'?
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The gastrocnemius muscle is involved in both plantar flexion of the foot and flexion of the lower limb at the knee joint.
The gastrocnemius muscle is involved in both plantar flexion of the foot and flexion of the lower limb at the knee joint.
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What is the primary function of the flexor compartment of the thigh?
What is the primary function of the flexor compartment of the thigh?
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The _____ muscle originates from the ilium and is responsible for abduction and medial rotation of the femur.
The _____ muscle originates from the ilium and is responsible for abduction and medial rotation of the femur.
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Match the muscle with the correct origin.
Match the muscle with the correct origin.
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Which of the following muscles is primarily responsible for supination of the hand?
Which of the following muscles is primarily responsible for supination of the hand?
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The primary action of the hamstrings is to perform extension at the knee joint.
The primary action of the hamstrings is to perform extension at the knee joint.
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What is the role of the patellar tendon?
What is the role of the patellar tendon?
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The main action of the tibialis anterior is _____ of the foot.
The main action of the tibialis anterior is _____ of the foot.
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Study Notes
The Muscular System
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All skeletal muscles are under voluntary control.
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The muscular system supports body movement and generates heat.
Muscle Anatomy
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The origin of a muscle is the end attached to the stabilised or stationary bone, usually proximal.
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The insertion of a muscle is the end attached to the moving bone, usually distal.
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The muscle belly is the thickened portion between tendons.
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Actions are the possible movements when a muscle contracts.
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Reverse muscle actions (RMAs) occur when the origin and insertion are reversed.
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Some muscles are capable of both actions and RMAs.
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Bones are levers that are moved by muscle action
- A load is resistance against effort
- Effort is the force required to move a load
Classes of Levers
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First-class lever: Fulcrum is between effort and load.
- Like a see-saw or a pair of scissors.
- Rare in the human body.
- Example: looking up at the ceiling.
- Effort: Posterior neck muscles
- Fulcrum: Atlanto-occipital joint
- Load: Weight of anterior skull
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Second-class lever: Load is between effort and fulcrum.
- Like a wheelbarrow.
- Produces a mechanical advantage.
- Little effort is needed to move a load a short distance.
- Example: Standing on your toes.
- Effort: Gastrocnemius (calf) muscles
- Load: Body weight
- Fulcrum: Metatarsophalangeal joints (ball of the foot)
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Third-class lever: Effort is between the fulcrum and the load.
- Like forceps.
- Most common levers in the body.
- Produces a mechanical disadvantage.
- Requires a lot of effort to move small loads a short distance.
- Example: Bending your elbow.
- Fulcrum: Elbow joint
- Effort: Biceps brachii muscles
- Load: Weight of the distal upper limb
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Third-class levers are advantageous because you can move the load the fastest.
Muscle Actions
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Muscles usually work in opposing pairs.
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Example: Flexion at the elbow joint.
- Agonist: Biceps brachii (contracts)
- Antagonist: Triceps brachii (relaxes)
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When both the biceps brachii and triceps brachii contract simultaneously, the elbow joint is stabilised.
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Muscles usually span more than one joint.
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Synergists muscles stabilize intermediate joints to ensure movement occurs only around one joint.
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Fixators stabilise one end of a bone so the other end can move.
- They help to prevent unwanted movement at the joint.
- Example: abduction of the arm
- Agonist: Deltoid muscles
- Fixators: Pectoralis minor, trapezius, serratus anterior
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Muscles are organised into compartments; groups of skeletal muscles, their nerves and blood vessels with specific functions.
- Example: flexor compartments of the upper limb are the anterior muscles.
- Example: extensor compartments of the upper limb are the posterior muscles.
Naming Muscles
- Muscles are named according to their:
- Direction
- Size
- Shape
- Action
- Number of origins
- Location
- Origin and insertion
Muscles of the Face
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Facial muscles permit facial expressions.
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Functions include:
- Expression of emotions
- Speech and vocalization
- Chewing (mastication)
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Orbicularis oculi closes the eyelid.
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Orbicularis oris:
- Closes the lips.
- Purses the lips.
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The occipitofrontalis has two bellies:
- Frontal belly: raises eyebrows and wrinkles the forehead.
- Occipital belly: raises hair and pulls the scalp posteriorly.
- These bellies are connected by the epicranial aponeurosis.
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Platysma:
- Pulls the corners of the mouth laterally and inferiorly.
- Permits frowning.
- Depresses the mandible.
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Masseter and temporalis:
- Elevate the mandible.
Muscles of the Neck
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The sternocleidomastoid muscles (one on each side of the neck) originate anteriorly at the manubrium and insert posteriorly at the temporal bone.
- Muscle action: rotates the head.
- Can also extend the head at the atlanto-occipital joint.
- Capable of RMA: elevation of the sternum.
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Contraction of one sternocleidomastoid muscle results in tilting the head to the side of the contracted muscle and rotating it to the opposite side.
Muscles of the Abdomen
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Function:
- Protect the abdominal viscera.
- Move the vertebral column.
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External obliques are the most superficial.
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Internal obliques are intermediate to the external obliques and transversus abdominis.
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Transversus abdominis is the deepest muscle.
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The fascicles of the abdominal muscles are arranged at angles to one another:
- External obliques: medially and inferiorly.
- Internal obliques: medially but superiorly.
- Transversus abdominis: transversely to the abdominal cavity.
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This arrangement creates a mesh network to provide additional protection to the abdominopelvic cavities.
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The rectus abdominis runs longitudinally along the anterior abdominal cavity.
- Divided by tendinous intersections.
- Responsible for the "6-8 pack" definition.
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The diaphragm permits breathing.
- It bounds the thoracic cavity inferiorly.
- Circular muscle with origins on many bones and tissues.
- Inserts on the central tendon.
- Contraction of the diaphragm moves it down, expanding the lungs.
Muscles that move the Pectoral Girdle
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Function:
- Move the clavicle and scapula, or
- Stabilise the scapula during movement of the humerus.
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Serratus anterior:
- Fan-shaped muscle.
- Originates on ribs and inserts on scapula.
- Abducts the scapula.
- RMA: Elevation of the ribs.
- Assists in pushing and punching.
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Trapezius:
- Originates on the occipital bone and inserts on the scapula.
- Permits: rotation, adduction, depression and stabilisation of the scapula.
Muscles that move the Upper Limb
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Function: Move the humerus.
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Pectoralis major:
- Permits adduction, medial rotation, and flexion of the arm.
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Deltoid:
- Wraps the shoulder posteriorly, laterally, and anteriorly.
- Permits: abduction, medial/lateral rotation, flexion/extension of the arm.
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Latissimus dorsi:
- Strongest and widest muscle of the back.
- Triangular posterior and lateral muscle.
- "Swimmer's muscle."
- Muscle actions: extension, adduction, medial rotation of the arm.
- RMA: elevation of the vertebral column and torso.
Muscles that move the Forearm
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Function: Move the radius and ulna.
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Biceps brachii:
- Two heads.
- Originate on the scapula and insert on the radius.
- Permits: flexion of the arm at the elbow joint and supination of the hand.
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Triceps brachii:
- Originates on the scapula and humerus.
- Inserts at the olecranon of the ulna.
- Permits: extension of the forearm at the elbow joint.
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Brachioradialis:
- Flexes the arm at the elbow joint.
- Controls speed of movement.
- Supinates and pronates the hand.
Muscles that move the Lower Limb
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Gluteal muscles function to move the femur.
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Gluteus maximus:
- One of the largest muscles in the body.
- Originates on the pelvis and inserts on the fascia of thigh muscles.
- Permits: extension of the leg at the hip joint and lateral rotation of the femur at the hip joint.
- RMA: extension of the torso.
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Gluteus medius:
- Deep to the gluteus maximus.
- Originates at the ilium and inserts on the femur.
- Permits: abduction and medial rotation of the femur.
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Flexor compartment of the thigh, also known as the "hamstrings."
- Three muscles: biceps femoris, semitendinosus, semimembranosus.
- Flex the distal lower limb at the knee joint and extend the leg at the hip joint.
- Biceps femoris: two heads (long and short).
- Semitendinosus: intermediate.
- Semimembranosus: most medial.
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Extensor compartment of the thigh, also known as the "quads."
- Four muscles: rectus femoris, vastus lateralis, vastus medialis, vastus intermedius.
- Anterior to the flexor compartment of the thigh.
- Permits: extension of the distal lower limb at the knee joint and flexion of the leg at the hip joint (rectus femoris).
- All insert on the patellar tendon.
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Medial compartment of the thigh:
- Gracilis: originates on the pubis and inserts on the tibia.
- Permits: adduction of the thigh at the hip, medial rotation of the thigh, and flexion of the leg around the knee joint.
Muscles that move the Foot
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Soleus and gastrocnemius belong to the superficial posterior compartment of the leg.
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Soleus:
- Originates at the fibula and tibia and inserts onto the calcaneal (Achilles) tendon.
- Permits plantar flexion of the foot at the ankle joint.
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Gastrocnemius:
- Originates on the femur and inserts at the calcaneal tendon.
- Permits: plantar flexion of the foot at the ankle joint and flexion of the lower limb at the knee joint.
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Tibialis anterior:
- Originates on the tibia and inserts on the metatarsals and tarsals.
- Permits: dorsiflexion of the foot at the ankle joint and supination (inversion) of the foot at intertarsal joints.
Homeostatic Imbalances of the Muscular System
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Muscle injuries are often activity-related.
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Regular moderate-intensity exercise helps protect against injury.
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Stretching, good nutrition, and sleep also help.
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Minor injuries include spasms, cramps, and muscle soreness.
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A spasm is an involuntary contraction of a muscle or group of muscles.
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Painful spasms are called cramps.
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Most common cause: Dehydration.
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Other causes: injury, overuse, prolonged periods in one position, and inadequate blood flow to muscle(s).
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Muscle soreness is often due to microscopic damage to muscles.
- May be accompanied by swelling or inflammation.
- May be delayed (24–48 hours following high-intensity exercise).
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Minor injuries (e.g., strains) should be treated with PRICE: Protection, Rest, Ice, Compression, and Elevation.
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Description
Explore the intricacies of the muscular system, including muscle anatomy, actions, and classes of levers that facilitate movement. This quiz covers key concepts such as voluntary control of skeletal muscles, the roles of origin and insertion, and the mechanics behind lever systems in the body.
