The Muscular System

Organs of the muscular system include:

Approximately 650 skeletal muscles, the heart, and organs containing smooth muscle like the stomach, bladder, blood vessels, etc.

What are the functions of the muscular system?

Producing movement by contracting (shortening) and relaxing (elongating), maintaining posture, stabilizing joints, and generating heat

What are the three types of muscles tissues?

Skeletal, cardiac, and smooth

Skeletal and smooth are elongated and are called

Fibers

Nonstriated; involuntary

Smooth Muscle

Spindle-shaped with a single nucleus.

Smooth Muscle

Contraction is slow and sustained.

Smooth Muscle

Striated; Involuntary

Cardiac Muscle

Found only in the heart.

Cardiac Muscle

Branching cells joined by special junctions called intercalated discs.

Cardiac Muscle

Contract slowly and in close coordination.

Cardiac Muscle

Striated; Voluntary

Skeletal Muscle

Contract rapidly and with great force, but tire easily and must rest after short periods of activity.

Skeletal Muscle

Muscle fibers are bundled together to form a fascicle which is wrapped by the epimysium.

Skeletal Muscle

Epimysia blend into strong tendons, which attach muscles indirectly to bones, cartilages, or connective tissue coverings. 

Skeletal Muscle

Functions of skeletal muscle:

Maintains posture, stabilizes joints, and generates heat

The 5 Golden Rules: 1st Rule

All skeletal muscles cross at least one joint

The 5 Golden Rules: 2nd Rule

The bulk of a skeletal muscle lies proximal to the joint crossed

The 5 Golden Rules: 3rd Rule

All skeletal muscles must have at least two attachments: the origin, and the insertion

The 5 Golden Rules: 4th Rule

Skeletal muscles can only pull; they never push

The 5 Golden Rules: 5th Rule

During a contraction, a skeletal muscle insertion moves toward the origin

Point attached to the immovable or less movable bone

Origin

Point attached to the movable bone

Insertion

Large muscles consist of thousands of single _______ that are contractile units.

Muscle fibers (muscle cells)

Muscle fibers are bound together by a connective tissue called __________.

Endomysium

**__________** wrap around a bundle of muscle fibers.

Perimysium

A bundle of muscle fibers is called a ________.

Fascicle

Many fascicles are bound together by the _________.

Epimysium

Epimysia blend into _______ which connect to bones, cartilages and other connective tissue coverings.

Tendons

**______** covers the epimysium to cover the entire muscle and runs into the tendon.

Fascia

The specialized plasma membrane of muscle cells.

Sarcolemma

Long organelles filling the cytoplasm of muscle cells.

Myofibrils

Contains only thin filaments called ______.

Actin

A darker midline interruption of the light I band.

Z disc

Contains entire length of thick filaments called ________.

Myosin

Lighter central area of the dark A band.

H zone

The center of the H zone

M line

Smallest unit of a muscle fiber that contracts

Sarcomere

What goes here?

Muscle

What goes here?

Fascicles

What goes here?

Muscle Fibers (Cells)

What goes here?

Myofibrils

What goes here?

Thick and Thin Filaments

What is A?

Tendon

What is B?

Epimysium

What is C?

Fascicle

What is D?

Muscle Fiber

What is E?

Sarcolemma

What is F?

Myofibril

What is G?

(A) Band

What is H?

(I) Band

What is I?

Sarcomere

What is J?

Thin (actin) myofilament

What is K?

Thick (myosin) myofilament

Ability to receive and respond to a stimulus.

Irritability

Ability to shorten when adequate stimulus is received.

Contractility

Ability of muscle cells to be stretched.

Extensibility

Ability of muscle cells to recoil and resume resting length after being stretched.

Elasticity

Muscles shorten and contract as the actin and myosin interact through a crossbridge formation

Sliding Filament Theory

Myosin heads attach to binding sites on the thin filaments forming a ___________.

Cross bridge

When a muscle is relaxed, regulatory proteins called ______ __and__ _______ cover part of the actin that myosin needs to bind to, preventing it from forming a cross bridge.

Troponin, tropomyosin

________are needed to bind to these regulatory proteins and change their shape and position on the actin. This Ca²⁺ is released from the _______.

Calcium ions, sarcoplasmic reticulum

In order for the myosin heads to release, energy from ______________ is needed.

Adenosine Triphosphate (ATP)

Without ATP, the myosin cannot release the actin so the muscle stays contracted

Rigor Mortis

One motor neuron and all the skeletal muscle cells it stimulates.

Motor Unit

Long, thread-like extensions of the neuron that reach the muscle cell and branch into axon terminals.

Axons

Branches of axons that form junctions with the sarcolemma of a muscle cell to form neuromuscular junctions.

Axon Terminals

Junctions between the nerve and muscle, specifically the motor neuron and sarcolemma, that contain vesicles filled with a chemical referred to as a neurotransmitter.

Neuromuscular Junctions

Chemical released by nerve upon arrival of nerve impulse in the axon terminal.

Neurotransmitter

The neurotransmitter that stimulates skeletal muscle.

Acetylcholine

Although the nerve endings and the sarcolemma are very close, they never touch. This gap between them is filled with tissue fluid and is called the ___________.

Synaptic Cleft

Naming Skeletal Muscles: Direction of muscle fibers

Rectus Femoris, Transversus Abdominis

Naming Skeletal Muscles: Relative size of the muscle

Gluteus Maximus, Gluteus Medius

Naming Skeletal Muscles: Location of the muscle

Temporalis, Frontalis

Naming Skeletal Muscles: Number of origins

Triceps Brachii, Biceps Brachii

Naming Skeletal Muscles: Location of the muscle’s origin and insertion

Sternocleidomastoid, Brachioradialis

Naming Skeletal Muscles: Shape of the muscle

Trapezius, Deltoid

Naming Skeletal Muscles: Action of the muscle

Flexor Carpals Ulnaris, Adductor Muscle

Movement that decreases the angle of the joint and brings two bones closer together; typical of a hinge joint

Flexion

Movement that increases the angle or distance between two bones or parts of the body; the opposite of flexion; typical of straightening elbow or knee

Extension

Extensions beyond 180°

Hyperextension

Movement of a bone around its longitudinal axis; common of ball-and-socket joints; example is moving the atlas around the axis (shaking your head “no”)

Rotation

Movement of a limb away from the midline or median plane of the body

Abduction

Movement of a limb towards the body midline; opposite of abduction

Adduction

A combination of flexion, extension, abduction, and adduction; common of ball-and-socket joints; proximal end of bone is stationary, and distal end  moves in a circle

Circumduction

Lifting the foot so that the superior surface approaches the shin (towards the dorsum)

Dorsiflexion

Depressing the foot (pointing the toes); “planting” the foot toward the sole

Plantar Flexion

Turning sole of the foot medially

Inversion

Turning the sole of the foot laterally

Eversion

Forearm rotates laterally so palm faces anteriorly; radius and ulna are parallel

Supination

Forearm rotates medially so palm faces posteriorly; radius and ulna cross each other like an X

Pronation

Moving the thumb to touch the tips of the fingers on the same hand

Opposition

Muscle that has major responsibility for causing a particular movement

Primer Mover

Muscles that oppose or reverse a movement

Antagonist

Help prime movers by producing the same movement or reducing undesirable movements

Synergist

Myofilaments are able to slide past each other during contractions, shortening the muscle and movement occurs.

Isotonic Contractions

tension in the muscle increases due to myosin “spinning their wheels”; myosin is trying to slide, but the muscle is pitted against some immovable object ending in the muscle being unable to shorten or produce movement.

Isometric Contractions

Continuous partial contractions of muscle fibers as a result of a staggered series of nerve impulses being delivered to different muscle cells.

Muscle Tone

If the nerve supply is damaged, the muscle is no longer stimulated in this manner and loses tone, becomes paralyzed, and begins to _______: waste away.

Atrophy

Result in stronger, more flexible muscles with greater resistance to fatigue thanks to an increase in the number of blood vessels; improves digestion and coordination

Aerobic (Endurance) Exercises