Muscle Contractions

myology

Study of muscles

orthopedics

A branch of medicine concerned with the prevention or correction of disorders of the muscular and skeletal systems

three types of muscle tissue

Striated (skeletal), smooth, cardiac

does striated have striations

Yes

where is striated located

On or around bones

function of striated

To move

why does skeletal muscle have a limited capacity for regeneration

Due to the presence of a small number of cells that can undergo cell division

is striated voluntary

Yes

does smooth muscle have striations

No

is smooth voluntary

No

where is smooth muscle found

In the walls of hollow organs that help with digestion, blood vessels, airways

function of smooth

Helps things move along

does smooth have a high capacity for cell regeneration

Compared with other types, yes

is cardiac voluntary

No

does cardiac have striations

Yes

where is cardiac found

Only in the heart

function of cardiac

Pumps blood

can cardiac regenerate

Under certain conditions

how much of the total body weight does muscle tissue make up

40-50%

functions of muscles

Movement, produces heat, stabilizes body positions, moves substances through the body, regulates organ volume

muscle properties

Enable muscles to function and contribute to homeostasis

what are the four muscle properties

Electrical excitability, contractility, extensibility, elasticity

electrical excitability

Ability to respond to certain stimuli by producing electrical signals called action potentials (impulse)

contractility

The ability of muscle tissue to contract forcefully when stimulated by an action potential

extensibility

The ability to stretch within limits without being damaged

which type has the most extensibility

Smooth

which has the least extensibility

Cardiac

elasticity

Ability to return to its original length and shape after contraction

direction

The orientation of muscle fibers relative to the body's midline

direction of internal obliques

Diagonally towards midline

direction of transverse

Perpendicular to body midline

rectus

Parallel to body midline

what are different ways muscles are named

Direction, size, shape, action, number of origins, location, origin and insertion

what muscles are named by size

Gluteus maximus (large), adductor longus (long)

shape

Shape of the muscle

what muscles are named by shape

Rhomboid (rhombus), deltoid (triangle), plat (flat)

what muscles are named by their action

Flexor, adductor

what muscle is named by the number of origins

Biceps (2)

what muscle is named by its location

Temporalis (temples)

what muscle is named by its origin and insertion

Brachioradialis

how do skeletal muscles produce movement

By pulling on tendons which pull on bones

which bones are involved during movement

Stationary bone and movable bone

origin

The attachment of a muscle by means of a tendon to the stationary bone

insertion

The point on the movable bone where muscles attach by means of a tendon

origin is

Proximal

insertion is

Distal

belly

The fleshy part between the tendons of the origin and insertion

what is each skeletal muscle composed of

Hundreds of thousands of muscle fibers

what does skeletal muscle tissue require

A large amount of ATP

what does muscle tissue have a large supply of

Blood vessels and nerves that penetrate it

components of connective tissue

Fascia, epimysium, perimysium, endomysium

fascia

A sheet of connective tissue found beneath the skin and around muscles and organs

two types of fascia

Superficial and deep

superficial fascia

Under the skin, made up of areolar connective tissue and adipose connective tissue

deep fascia

Holds muscles together and separates them into functional groups (bundles)

what tissue is deep fascia made up of

Dense and irregular

epimysium

Covers the entire muscle

perimysium

Surrounds bundles of 10 to 100 or more muscle fibers called fascicles

endomysium

Wraps around individual muscle fibers

which components extend to form tendons

Epimysium, perimysium, endomysium

tendons

Made up of collagen fibers and dense regular connective tissue and forms a cord

muscle fibers

There are hundreds to thousands making up skeletal muscles arranged parallel to each other

sarcolemma

Plasma membrane around each muscle fiber

plasma membrane

Cell membrane

transverse tubules

Tunnel-like extensions of the sarcolemma that pass through muscle fibers from side to side

sarcoplasm

Cytoplasm of the muscle fiber that contains many mitochondria which produce a large amount of ATP

sarcoplasmic reticulum

A network of fluid-filled membrane-enclosed tubules that stores Ca+2 ions for muscle contractions

what is sarcoplasmic reticulum similar to

Smooth endoplasmic reticulum

myoglobin

Red pigment found in the sarcoplasm that gives color to the skeletal muscles and stores oxygen until needed by the mitochondria to generate ATP

myofibrils

Cylinder structures found inside the muscle fibers made up of thin and thick filaments

sarcomere

Basic functional units of striated muscle fibers, compartments of filaments overlapping in a specific pattern

z discs

Zigzagging zones of dense protein materials separating sarcomeres from each other

a bands

A darker area within the sarcomere that extends the entire length of the thick filaments

h zones

Narrow part of the thick filament that is at the center of each A band

i band

A lighter colored area on either side of the A band which contains the rest of the thin filaments which extend into two sarcomeres

what makes up striations

Alternating darker A bands and lighter I bands

thick filaments

Made up of a protein called myosin

what are thick filaments shaped like

Two golf clubs twisted together

what is the head of the golf clubs called

Myosin heads

what are the shafts called

Myosin tails

thin filaments

Made up of a protein called actin

what do individual actin molecules join to form

Actin filaments that twist into a double helix

what does each actin molecule have on it

A little brown spot called the myosin binding site

what other protein molecules are present

Tropomyosin and troponin

what do these proteins do

Cover the myosin binding sites on actin in a relaxed muscle fiber

what has to happen before a skeletal muscle fiber can contract

It must be stimulated by an electrical signal called a muscle action potential delivered by its neuron called a motor neuron

what does each nerve impulse usually elicit

One muscle action potential

motor unit

A single motor neuron along with all the muscle fibers it stimulates

what does ACh stand for

Acetylcholine

ACh

Neurotransmitter