Unit 5: The Muscular System

A-band

an area where actin and myosin overlap

Actin

a muscle protein; a major component of the I-band and helps to compose the thin filaments

Cardiac muscle

the principal involuntary-muscle tissue of the vertebrate heart made up of striated fibers joined at usually branched ends and functioning in synchronized rhythmic contraction

Cramp

a painful, involuntary muscle contraction, usually caused by fatigue or strain

Fascia

a sheet of tissue that covers or connects parts inside the body (such as muscles)

I-band

the small gap between the myosin and the Z-band at the end of the sarcomere

Involuntary

a type of muscle that contracts without conscious control

Myocyte

muscle cell

Myofibril

located within the muscle cells; composed of thick (myosin) and thin (actin) filaments

Myosin

a muscle protein; a major component of the A-band; thick filaments

Muscle

a tissue that has the ability to contract to help with movement

Muscle contraction

when the sarcomere shortens and the Z-lines move closer together

Sarcomere

the basic unit of muscle contraction; segment between two neighboring Z-lines

Skeletal muscle

striated muscle that is attached to the bones of the skeleton and is usually under voluntary control.

Sliding filament theory

theory that explains how sarcomeres contract; myosin filaments use energy from ATP to 'walk' along the actin filaments with their cross bridges; myofilaments slide past one another and contract the myocyte

Smooth muscle

muscle tissue that lacks cross striations, is made up of elongated spindle-shaped cells having a central nucleus and is found especially in vertebrate hollow organs and structures (as the digestive tract and bladder) as thin sheets performing functions not subject to direct voluntary control

Sprain

an injury to the joints caused by overstretching

Strain

an injury to the muscle caused by overstretching

Superficial muscles

muscles that are located in the layer closest to the skin

Tendon

a tough piece of tissue in your body that connects a muscle to a bone

Visceral muscle

smooth muscle found in the digestive, respiratory and circulatory systems.

Voluntary

a type of muscle that is controlled by the individual, such as the striated muscle

Maintains posture

Muscles adjust continuously to provide coordination of movement, stabilizing joints.

Generating heat

As ATP is used to provide energy for muscle contraction, almost 75% of the energy escapes as heat, providing the majority of body heat needed for survival.

Myocytes

Muscle cells that make up every muscle in the body.

Voluntary muscles

Muscles that are under conscious control.

Involuntary muscles

Muscles that are not under conscious control.

Types of muscles

There are three types of muscles in the body: skeletal (stratified), smooth, and cardiac.

Muscle Cell Contraction

Muscle contraction starts with a signal from the nervous system.

Myofibrils

Hundreds of organelles contained in each muscle fiber.

Myofilaments

Bundles of contractile proteins that make up each myofibril.

Sarcomeres

Functional units arranged along the muscle fiber, and the basic unit of muscle contraction.

Z line

The area between two Z lines defines the sarcomere.

A band

The area in the sarcomere where myosin and actin overlap.

Muscle fiber contraction

A muscle fiber either contracts fully, or it doesn't contract at all.

Strength of muscular force

Determined by the number of fibers that contract; more fibers contracting at the same time results in greater force.

Skeletal muscle structure

Each skeletal muscle is an organ consisting of skeletal muscle tissue, connective tissue, nerve tissue, and vascular tissue.

Endomysium

The connective tissue that wraps each individual muscle fiber.

Fascicles

Bundles in which muscle fibers are arranged.

Perimysium

The connective tissue that separates and surrounds fascicles.

Epimysium

The outermost layer of connective tissue that surrounds the fascicles.

Connective Tissue

Multiple layers of connective tissue give support and protection to the delicate muscle fibers and allow them to withstand the force of contraction.

Transport System

Active skeletal muscle needs an efficient transport system to provide the muscle with oxygen and nutrients needed for contraction and to remove waste products.

Origin

The bone that does not move during contraction.

Insertion

The bone that does move during contraction.

Flexion

An action that decreases the angle at a joint.

Flexor

A muscle that causes the angle of a joint to become smaller.

Extension

An action that straightens or extends a joint.

Extensor

A muscle that causes a joint to straighten out.

Antagonistic Pairs

Groupings of muscles that work against each other to move parts of the body in opposite directions.

Agonist

A muscle that causes a movement to occur through its own contraction.

Antagonist

A muscle that opposes the specific movement of the agonist muscle, controlling and slowing its motion.

Skeletal Muscle Variability

Skeletal muscles can vary in size, shape, and arrangement of fibers.

Parallel Fiber Pattern

Fibers run parallel to the direction of the muscle, functioning similarly to a single muscle fiber.

Convergent Fiber Pattern

Fibers fan out from a common point of attachment, allowing for a more versatile type of movement.

Pennate Fiber Pattern

Muscles have one or more tendons running through the body with fascicles forming an oblique angle to the tendons, able to generate greater tension.

Sphincter

Also known as circular muscles, arranged concentrically around an opening or recess, getting smaller as they contract.

Biceps Brachii

A muscle that, when contracted, pulls on the radius bone, causing the arm to move up.

Triceps Brachii

A muscle that contracts to extend or straighten the arm, opposing the biceps brachii.

Prime Movers

Muscles that are primarily responsible for generating a specific movement.

Muscle Relaxation

Muscles extend after contraction only passively through relaxation.

Vastus

Huge

Maximus

Large

Longus

Long

Minimus

Small

Brevis

Short

Deltoid

Triangular

Rhomboid

Like a rhombus

Latissimus

Wide

Teres

Round

Trapezius

Like a trapezoid

Rectus

Straight

Transverse

Across

Oblique

Diagonally

Orbicularis

Circular

Pectoralis

Chest

Gluteus

Buttock or rump

Brachii

Arm

Supra-

Above

Infra-

Below

Sub-

Under or beneath

Lateralis

Lateral

Biceps

Two heads

Triceps

Three heads

Quadriceps

Four heads

Sternocleidomastoideus

Origin on the sternum and clavicle, insertion on the mastoid process

Brachioradialis

Origin on the brachium or arm, insertion on the radius

Abductor

To abduct a structure

Adductor

To adduct a structure

Levator

To lift or elevate a structure

Masseter

To chew

Muscle hypertrophy

The increase in muscle mass due to exercise, particularly weight training