The Muscular System

MUSCLES

are responsible for all types of body movement – they contract or shorten and are the machine of the body

MUSCLES

the body such as the intestines and blood vessels, and it makes up nearly half the body’s mass

mus

Latin word, “little mouse.”

SKELETAL MUSCLE

Most are attached by tendons to bones

Skeletal muscle, Cardiac muscle, Smooth muscle

MUSCLE TYPES

SKELETAL MUSCLE CHARACTERISTICS

Cells are multinucleate

SKELETAL MUSCLE

Striated-have visible banding

SKELETAL MUSCLE

Voluntary – subject to conscious control

SKELETAL MUSCLE

Cells are surrounded and bundled by connective tissue = great force, but tires easily

Endomysium

around single muscle fiber

Perimysium

around a fascicle (bundle) of fibers

Epimysium

covers the entire skeletal muscle

Fascia

on the outside of the epimysium

Epimysium

blends into a connective tissue attachment

Tendon

cord-like structure in bones

Aponeuroses

sheet-like structure in bones

Bones, Cartilages, Connective tissue coverings

Sites of muscle attachment in skeletal muscle

SMOOTH MUSCLE

Has no striations

SMOOTH MUSCLE

Spindle-shaped cells

SMOOTH MUSCLE

Single nucleus

SMOOTH MUSCLE

Involuntary – no conscious control

SMOOTH MUSCLE

Found mainly in the walls of hollow organs

SMOOTH MUSCLE

a type of muscle that is Slow, sustained and tireless

CARDIAC MUSCLE

found in only one place in the body—the heart, where it forms the bulk of the heart walls

CARDIAC MUSCLE

Has striations

CARDIAC MUSCLE

Usually has a single nucleus

CARDIAC MUSCLE

Joined to another muscle cell at an intercalated disc

CARDIAC MUSCLE

Involuntary

nervous system

can also stimulate the heart to shift into “high gear” for short periods, as when you run to catch a bus

Cardiac muscle

usually contracts at a fairly steady rate set by the heart’s “in-house” pacemaker

Produce movement

responsible for our body’s mobility, including all locomotion

MUSCLE FUNCTIONS

Maintain posture

MUSCLE FUNCTIONS

Stabilize joints

MUSCLE FUNCTIONS

Generate heat

ATP

is used to power muscle contraction, nearly three-quarters of its energy escapes as heat. This heat is vital in maintaining normal body temperature

Nuclei

just beneath the sarcolemma of skeletal muscles

Myofibril

Bundles of myofilaments

Myofibril

Myofibrils are aligned to give distinct bands

I band

light band

A band

dark band

Sarcomere

Contractile unit of a muscle fiber

Thick filaments

myosin filaments

Thick filaments

Composed of the protein myosin

Thick filaments

Has ATPase enzymes

Thin filaments

actin filaments

Thin filaments

Composed of the protein actin

Myosin filaments

have heads (extensions, or cross bridges)

Myosin and actin

overlap somewhat

Irritability

ability to receive and respond to a stimulus

Contractility

ability to shorten when an adequate stimulus is received

Extensibility

ability to be stretched

Elasticity

ability to recoil and resume resting length

Skeletal muscles

must be stimulated by a nerve to contract (motor neuron)

Neuromuscular junctions

association site of nerve and muscle

Synaptic cleft

gap between nerve and muscle

Synaptic cleft

Nerve and muscle do not make contact

Synaptic cleft

Area between nerve and muscle is filled with interstitial fluid

Neurotransmitter

chemical released by nerve upon arrival of nerve impulse

acetylcholine

The neurotransmitter for skeletal muscle

Neurotransmitter

attaches to receptors on the sarcolemma

Sarcolemma

becomes permeable to sodium (Na+)

muscle contraction

Once started, cannot be stopped

Graded responses

different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus

CP

high-energy molecule

Anaerobic glycolysis

Reaction that breaks down glucose without oxygen

Aerobic Respiration

This is a slower reaction that requires continuous oxygen

Anaerobic glycolysis

Glucose is broken down to pyruvic acid to produce some ATP

Lactic acid

produces muscle fatigue

Aerobic Respiration

Series of metabolic pathways that occur in the mitochondria

Aerobic Respiration

Glucose is broken down to carbon dioxide and water, releasing energy

oxygen debt

The common reason for muscle fatigue

Increase acidity and lack of ATP

causes the muscle to contract less

Isotonic contractions

Myofilaments are able to slide past each other during contractions

Isotonic contractions

The muscle shorten

Isometric contractions

The muscle is unable to shorten

Movement

is attained due to a muscle moving an attached bone

Muscles

are attached to at least two points

Origin

attachment to a moveable bone

Insertion

attachment to an immovable bone

Flexion

decreases angle of joint and brings two bones closer together

Extension

opposite of flexion

Rotation

movement of a bone in longitudinal axis, shaking head “no”

Abduction/Adduction

towards the midline of the body

circumduction

movement of a body region in a circular manner

Dorsiflexion and plantar flexion

Up-and down movements of the foot at the ankle

Inversion and eversion

are also special movements of the foot

Supination and pronation

refer to movements of the radius around the ulna

Opposition

This is the action by which you move your thumb to touch the tips of the other fingers

Prime mover

muscle with the major responsibility for a certain movement

Antagonist

muscle that opposes or reverses a prime mover

Synergist

muscle that aids a prime mover in a movement and helps prevent rotation

rectus

straight

maximus

largest

triceps

three heads

sterno

on the sternum

deltoid

triangular

Direction of muscle fibers

rectus

Relative size of the muscle

maximus

Number of origins

triceps

Location of the muscle’s origin and insertion

sterno