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Questions and Answers
What is primarily generated by the muscular system besides body movement?
What is primarily generated by the muscular system besides body movement?
All skeletal muscles are under involuntary control.
All skeletal muscles are under involuntary control.
False
What is the term for the end of a muscle that is attached to a moving bone?
What is the term for the end of a muscle that is attached to a moving bone?
insertion
The muscle belly is the thickened portion between tendons.
The muscle belly is the thickened portion between tendons.
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Which type of lever has the load located between the effort and the fulcrum?
Which type of lever has the load located between the effort and the fulcrum?
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What is the name of the joint that acts as the fulcrum when looking up at the ceiling?
What is the name of the joint that acts as the fulcrum when looking up at the ceiling?
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Match the lever types with their examples:
Match the lever types with their examples:
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The load is always at the end of a third-class lever.
The load is always at the end of a third-class lever.
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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 latissimus dorsi permits lateral rotation of the arm.
The latissimus dorsi permits lateral rotation of the arm.
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What muscle is responsible for abducting the scapula?
What muscle is responsible for abducting the scapula?
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The _____ flexes the arm at the elbow joint.
The _____ flexes the arm at the elbow joint.
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Match the muscles to their primary actions:
Match the muscles to their primary actions:
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Which muscle originates on the occipital bone?
Which muscle originates on the occipital bone?
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The gluteus medius is located above the gluteus maximus.
The gluteus medius is located above the gluteus maximus.
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Which muscle group is often referred to as the hamstrings?
Which muscle group is often referred to as the hamstrings?
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The vastus lateralis, vastus medialis, and vastus intermedius all originate on the _____ .
The vastus lateralis, vastus medialis, and vastus intermedius all originate on the _____ .
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Match the muscle with its action:
Match the muscle with its action:
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What is the role of the flexor compartment of the thigh?
What is the role of the flexor compartment of the thigh?
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Moderate-intensity exercise helps protect against muscle injuries.
Moderate-intensity exercise helps protect against muscle injuries.
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What is the main function of the gluteus maximus?
What is the main function of the gluteus maximus?
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The _____ originates on the scapula and humerus and allows for extension of the forearm at the elbow joint.
The _____ originates on the scapula and humerus and allows for extension of the forearm at the elbow joint.
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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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Fixators stabilize the joints to allow for movement at other joints.
Fixators stabilize the joints to allow for movement at other joints.
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What is the role of synergist muscles during joint movement?
What is the role of synergist muscles during joint movement?
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The ___________ stabilizes one end of the bone so that the other end can move.
The ___________ stabilizes one end of the bone so that the other end can move.
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Which muscle is responsible for depressing the mandible?
Which muscle is responsible for depressing the mandible?
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Muscles are organized into __________, which are groups of muscles, their nerves, and blood vessels.
Muscles are organized into __________, which are groups of muscles, their nerves, and blood vessels.
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The triceps brachii acts as the agonist during elbow flexion.
The triceps brachii acts as the agonist during elbow flexion.
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Match the muscle to its action:
Match the muscle to its action:
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Which muscle acts on the anterior portion of the skull to raise the eyebrows?
Which muscle acts on the anterior portion of the skull to raise the eyebrows?
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What would occur if both the biceps brachii and triceps brachii contract simultaneously?
What would occur if both the biceps brachii and triceps brachii contract simultaneously?
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The rectus abdominis runs __________ along the anterior of the abdominal cavity.
The rectus abdominis runs __________ along the anterior of the abdominal cavity.
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The main function of the external obliques is to protect the abdominal viscera.
The main function of the external obliques is to protect the abdominal viscera.
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What type of connective tissue forms tendinous intersections?
What type of connective tissue forms tendinous intersections?
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The ___________ is the deepest muscle layer in the abdominal region.
The ___________ is the deepest muscle layer in the abdominal region.
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Study Notes
Muscular system
- All skeletal muscles are under voluntary control
- Generate heat
- Origin - end of muscle attached to stabilized or stationary bone
- Insertion - end of muscle attached to moving bone
- Muscle belly is the thickened portion between tendons
- Muscle actions are the movements possible when the muscle contracts
- Reverse muscle actions (RMAs) result when the origin and insertion are reversed
- Levers can lift loads using effort
- Effort - force required to move a load
- Bones are levers that are moved by the effort of muscle action
Types of levers
- First-class levers: fulcrum is between effort and load, like a see-saw or pair of scissors, rare in the human body
- Second-class levers: load is between effort and fulcrum, like a wheelbarrow, produce a mechanical advantage, little effort to move load a short distance
- Third-class levers: effort is between the fulcrum and the load, like forceps, most common levers in the body, always produce a mechanical disadvantage, a lot of effort to move small loads a short distance
Muscle groups
- Most muscles work in opposing pairs
- Agonist - exerts effort to move lever (bones of forearm)
- Antagonist - opposes agonist
- Synergist - stabilizes intermediate joints when contracted
Muscle organization
- Muscles are organized into compartments
- Compartments - groups of skeletal muscles, their nerves, and their blood vessels
- Specific functions
Muscle naming
- Direction: Transversus abdominis muscles run perpendicular to the midline
- Size: Latissimus dorsi muscles are the widest of the back
- Shape: Serratus anterior muscles have a saw-shape at the anterolateral portion of the chest
- Action: External anal sphincter decreases the diameter of the anus
- Number of origins: the biceps brachii have two origins
- Location: the occipitofrontalis has has a frontal and occipital belly
- Origin and insertion: the sternocleidomastoid originates on the sternum and inserts on the mastoid process of the temporal bone
Muscles of the face
- Facial muscles permit facial expressions
- Expressions of emotions
- Speech and vocalization
- Chewing or mastication
Muscles of the eye and mouth
- Orbicularis oculi closes the eyelid
- Orbicularis oris: closes the lips, purses the lips
- Occipitofrontalis: two bellies - frontal and occipital
- Frontal belly: raises eyebrows, wrinkles forehead
- Occipital belly: raises hair (pulls scalp posteriorly)
- Bellies connected by the epicranial aponeurosis
Muscles that move the mandible
- Platysma: pulls the corners of the mouth laterally and inferiorly, permits frowning, depresses the mandible
- Masseter and temporalis: elevate the mandible
Muscles of the neck
- Two sternocleidomastoid muscles
- One on each side of the neck
- Originates anteriorly (manubrium) and inserts posteriorly (temporal bone)
- Rotates the head
- Extends the head at the atlanto-occipital joint
- Capable of RMA - Elevation of sternum
Muscles of the abdomen
- Protect the abdominal viscera
- Move the vertebral column
- External, internal, and transversus abdominis muscles
- External obliques - most superficial
- Internal obliques intermediate to external obliques and transversus abdominis
- Transversus abdominis - deepest muscle
- Fascicles of the abdominal muscles are arranged at angles to one another
- Rectus abdominis - runs longitudinally along the anterior of the abdominal cavity
- Divided by tendinous intersections
- Responsible for definition of the “6–8 pack”
- Diaphragm permits breathing
- Bounds the thoracic cavity inferiorly
- Circular muscle with origins on many bones and tissues
- Inserts on the central tendon
- Contracts, it moves down the lungs expand
Muscles that move the pectoral girdle
- Move the clavicle and scapula, or
- Stabilize the scapula during movement of the humerus
- Serratus anterior - abducts the scapula
- RMA: Elevation of the ribs
- Trapezius muscle - rotates, adducts, depresses, and stabilizes the scapula
Muscles that move the upper limb
- Move the humerus
- Pectoralis major- adducts, medially rotates, and flexes the arm
- Deltoid muscles - abducts, medially/laterally rotates, flexes/extends the arm
- Latissimus dorsi - extends, adducts, and medially rotates the arm
- RMA: elevation of the vertebral column and torso
Muscles that move the forearm
- Move the radius and ulna
- Biceps brachii: two heads (originate on the scapula), inserts on the radius, flexes the arm at the elbow joint, supinates the hand
- Triceps brachii: originates on scapula and humerus, inserts at the olecranon of the ulna, extends the forearm at the elbow joint
- Brachioradialis: flexes the arm at the elbow joint, controls speed of movement, supinates and pronates the hand
Muscles that move the lower limb
- Gluteal muscles function to move the femur
- Gluteus Maximus - one of the largest muscles in the body, extends the leg at the hip joint, laterally rotates the femur at the hip joint
- RMA: extension of the torso
- Gluteus medius - abducts, and medially rotates the femur
Flexor compartment of the thigh
- Includes the “hamstrings” - flex the distal lower limb at the knee joint, extend the leg at the hip joint
- Biceps femoris - two heads (long and short), lateral hamstring
- Semitendinosus - intermediate hamstring
- Semimembranosus - medial hamstring
Extensor compartment of the thigh
- The “quads” - four muscles, anterior to the flexor compartment of the thigh, extend the distal lower limb at the knee joint, flex the leg at the hip joint (rectus femoris)
- Vastus lateralis, vastus medialis, and vastus intermedius - all originate on the femur
- Rectus femoris originates on the ilia
- All insert on the patellar tendon
Medial compartment of the thigh
- Gracilis: originates on the pubis, adducts the thigh at the hip, medially rotates the thigh, flexes the leg around the knee joint
Muscles that move the foot
- Soleus and gastrocnemius: superficial posterior compartment of the leg
- Soleus: originates at the fibula and tibia, inserts at the calcaneal (Achilles) tendon, permits plantar flexion of the foot at the ankle joint
- Gastrocnemius: originates on the femur, inserts at the calcaneal tendon, permits plantar flexion of the foot at the ankle joint, flexes the lower limb at the knee joint
- Tibialis anterior: originates on the tibia, inserts on the metatarsals and tarsals, permits dorsiflexion of the foot at the ankle joint, supination (inversion) of the foot at intertarsal joints
Homeostatic imbalances of the muscular system
- Muscle injuries are often activity-related
- Regular, moderate-intensity exercise helps protect against injury
- Stretching, good nutrition, and sleep also help!
- Minor injuries include spasms, cramps, and muscle soreness
- Spasm - involuntary contraction of a muscle or group of muscles
- Painful spasms are called cramps
- Most common cause - dehydration
- Other causes: injury, overuse, prolonged periods in one position, and inadequate blood flow to muscle(s)
- Muscle soreness - often due to microscopic damage to muscles
- May be accompanied by swelling or inflammation
- May be delayed (24–48 hours following high-intensity exercise)
- Minor injuries (e.g.strains) should be treated with PRICE - Protection rest ice compression and elevation
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Description
Explore the structure and function of the muscular system, including muscle control and types of levers in the body. Understand the roles of muscles, origins, insertions, and how mechanical advantages are achieved through levers. Test your knowledge on muscle actions and lever classifications.
