The Muscular SystemPSE 4U

Mr. S. Kelly

North Grenville DHS

Muscle Basics in

Review

• Three main types of muscles

• Skeletal: voluntary and striated (striped appearance under a

microscope)

• Cardiac: of the heart, form the wall of the heart,

involuntary, striated, directed by autonomic nervous system

• Smooth: surround body’s internal organs, involuntary

The musculoskeletal

system

AKA the locomotor system

Allows us to create movement

Comprised of muscles, bones, connective tissues

(ligaments, tendons, joint capsules, cartilage)

Muscular system and skeletal system can be examined

independently but are rarely considered separately

when studying movement, health, and exercise

Naming Muscles

Muscles are named with the following influences:

Action: flexor digitorum, extensor carpi ulnaris

Direction of fibers: rectus abdominus

Location: tibialis anterior

Number of divisions or heads: biceps, triceps

Shape: deltoid, trapezius

Point of attachment: sternocleidomastoid

Muscle pairs

• Muscles are often arranged in pairs… WHY?

• When muscles contract, they PULL on bones to create movement… therefore movement in the OPPOSITE direction requires an OPPOSING muscle (or group of muscles)

• Muscles responsible for a given movement are called agonistor prime mover

• The counteracting muscle (lengthens while agonist contracts) is called the antagonist

• Any complex movements require both agonist, antagonist, and stabilizer muscles working in conjuction

Short List of

Examples

Agonist (prime mover) Antagonist

Biceps brachii Triceps brachii

Deltoids Latissimus Dorsi

Pectoralis major Trapezius / Rhomboids

Rectus Abdominus Erector Spinae

Quadriceps Hamstrings

Gastroc/soleus complex Tibialis Anterior

Muscle Attachments

• Muscles attach to bones directly with the outer muscle

membrane attaching to the outer skeletal membrane

(pretty rare)

• Common form of attachment is indirect, via tendons

• The origin of a muscle is its attachment on the LEAST

moveable of the attachment sites

• The insertion of a muscle is its attachment on the

MORE moveable of the attachment sites

A look at the Muscle

Muscle Anatomy and

Terms

• Muscle fiber: a basic unit of skeletal muscle

• Endomysium: sheath of tissue covering each muscle fiber

• Fascicle (fasciculus): bundle of skeletal muscle fibers

• Perimysium: sheath of tissue that groups muscle fibers into fascicles

• Epimysium: tissue that envelopes the entire muscle (changes properties, tensile strength as it transitions from muscle to tendon)

Levels of Skeletal

Muscle Anatomy

Muscle Fiber

anatomy and terms

• Sarcolemma: cell membrane directly beneath the endomysium, contains cell’s cytoplasm

• Sarcoplasm: skeletal muscle cell’s cytoplasm

• This differs from cytoplasm of other cells in that it contains higher conc. of stored glycogen, myoglobin, Ca, mitochondria

• Myofibrils: thread-like structures running the length of the muscle fibe

• Sarcomeres: repeating structural compartments along myofibril; contain myosin and actin

Levels of muscle

anatomy

Proteins and

filaments

• Myosin: looks a bit like a golf club, possesses a head

and a tail; head has a binding site for actin

• Actin: possesses binding site for myosin head, also has

two other proteins…

• Troponin: has a binding site for calcium

• Tropomyosin: cord-like structure, resembles a string,

covers binding site on actin filament

Next…

• Sliding Filament Theory

• Neuromuscular system

• Excitation-contraction coupling

• Muscular system lab… may be in conjunction with

energy systems…