Anatomy Chapter 6: The Muscular System

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Questions and Answers

What are the types of muscles?

Skeletal

Cardiac

Smooth

All of the above (correct)

What does 'myo-' refer to?

muscle

What does 'sarco-' refer to?

flesh

What does 'epi-' mean?

above/upon/over Signup and view all the answers

What does 'iso-' signify?

equal/same Signup and view all the answers

What does 'peri-' mean?

around Signup and view all the answers

Which characteristics describe skeletal muscle?

Cigar-shaped cells Signup and view all the answers

What is the function of endomysium?

encloses single muscle fiber Signup and view all the answers

What is the role of perimysium?

wraps around a fascicle of muscle fibers Signup and view all the answers

What is the function of epimysium?

covers entire skeletal muscle Signup and view all the answers

What are the main functions of muscles?

All of the above Signup and view all the answers

What is the definition of a motor unit?

1 motor neuron & all skeletal muscle cells stimulated by 1 neuron Signup and view all the answers

What is the process of aerobic respiration?

slower reaction that requires continuous delivery of oxygen & nutrients Signup and view all the answers

What occurs during anaerobic respiration?

used during heavy exercise Signup and view all the answers

What happens during isotonic contractions?

muscle shortens & movement occurs Signup and view all the answers

What characterizes isometric contractions?

tension increases but muscles don't shorten Signup and view all the answers

What is the purpose of resistance exercise?

increases muscle size and strength Signup and view all the answers

Which of the following is NOT one of the 5 Golden Rules of SM activity?

All muscles can push Signup and view all the answers

What is the function of the prime mover in muscles?

muscle with major responsibility for certain movement Signup and view all the answers

What does an antagonist muscle do?

opposes or reverses a prime mover Signup and view all the answers

What is the role of a synergist muscle?

aids prime mover in movement Signup and view all the answers

What is a fixator muscle?

specialized synergists that hold a bone still Signup and view all the answers

What are the criteria for classifying muscles?

All of the above Signup and view all the answers

Study Notes

Muscle Types

Three main types: skeletal, cardiac, smooth.

myo-: Refers to muscle.
sarco-: Refers to flesh.
epi-: Means above, upon, or over.
iso-: Means equal or the same.
peri-: Means around.

Skeletal Muscle

Cells are large, cigar-shaped, and multinucleate.
Known as striated and voluntary muscle, under conscious control.
Contracts rapidly upon stimulation.

Connective Tissue in Skeletal Muscle

Endomysium: Encloses a single muscle fiber.
Perimysium: Wraps around a fascicle (bundle) of muscle fibers.
Epimysium: Covers the entire skeletal muscle.

Smooth Muscle

Lacks striations and is involuntary.
Located in structures like pupils of eyes and arrector pili muscles.
Contractions are slow and sustained.

Cardiac Muscle

Striated and involuntary, found exclusively in heart walls.
Uninucleate cells interconnect through gap junctions (intercalated discs).

Muscle Functions

Maintains posture and body position.
Stabilizes joints.
Generates heat.

Microscopic Anatomy of Skeletal Muscle

Sarcolemma: Specialized plasma membrane.
Myofibrils: Long organelles vital for contraction, exhibit alternating dark (A band) and light (I band) bands.
Sarcomere: Basic contractile unit; defined by Z discs.

Muscle Fiber Structure

Composed of sarcolemma and myofibril.

Special Function of Skeletal Muscle

Contractility: Ability to forcibly shorten in response to a stimulus.

Motor Unit

Consists of one motor neuron and all skeletal muscle cells it stimulates.

Graded Responses

Not all muscle fibers are activated simultaneously, allowing for variations in force and shortening.

Energy Sources

ATP: Primary energy molecule utilized by the body.
Aerobic Respiration: Requires oxygen; slower but more efficient, used during rest or light exercise.
Anaerobic Respiration: Fast, less efficient, used during heavy exercise.

Types of Muscle Contractions

Isotonic Contractions: Muscle shortens and movement occurs.
Isometric Contractions: Muscle tension increases without shortening.

Resistance Exercise

Enhances muscle size and strength.

Golden Rules of Skeletal Muscle Activity

Muscles cross at least one joint.
Muscle bulk typically lies proximal to the joint they cross.
Muscles have at least two attachments: origin and insertion.
Muscles can only pull, never push.
During contraction, the muscle insertion moves toward its origin.

Types of Body Movements

Muscles attached at two points; contraction leads to movement across joints.

Origin and Insertion

Origin: Attachment to an immovable or less movable bone.
Insertion: Attachment to a movable bone.

Specific Movements

Flexion: Decreases the joint angle; brings bones closer together.
Extension: Increases the angle between bones.
Rotation: Movement of the bone around its longitudinal axis.
Abduction: Movement of a limb away from the midline.
Adduction: Movement of a limb toward the midline.
Circumduction: Combination of flexion, extension, abduction, and adduction, with the proximal end stationary.
Dorsiflexion: Lifting the foot so its superior surface points to the shin.
Plantar Flexion: Pointing toes away from the head.
Inversion: Turning the foot toward the midline.
Eversion: Turning the foot away from the midline.
Supination: Palm facing anteriorly.
Pronation: Palm facing posteriorly with radius and ulna crossing.

Muscle Classifications

Prime Mover: Muscle with primary responsibility for a specific movement.
Antagonist: Muscle that opposes or reverses the action of a prime mover.
Synergist: Muscle that assists the prime mover and reduces unwanted movements.
Fixator: Specialized synergists that stabilize the origin of the prime mover.

Muscle Characteristics

Classified by direction of muscle fibers, size, location, number of origins, origin and insertion locations, shape, and action.

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Anatomy Chapter 6: The Muscular System - Test

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