Muscular System

Muscles in Humans

There are approximately 650 muscles in the human body, each performing a unique role.

Muscles are the driving force behind the musculoskeletal systems, enabling us to sit, stand, walk, talk and do anything else that requires movement.

They also keep our heart beating and help us breathe. In order to function, they must be able to react to

stimuli, contract, extend and return to their normal shape.

Muscular System

Muscles are responsible for all types of body movement

3 basic muscle types are found in the bodySkeletal muscleCardiac muscleSmooth muscle

Characteristics of Muscles

Muscle cells are elongated (muscle cell = muscle fiber)

Contraction of muscles is due to the movement of microfilaments

All muscles share some terminologyPrefix myo refers to musclePrefix mys refers to musclePrefix sarco refers to flesh

Nervous system to muscles

Within the nervous system, nerve impulses travel from neuron to neuron along complex nerve pathways. The junction between the parts of two such neurons is called a "synapse.“

If a sufficient amount of the substance (called "neurotransmitter") is released, the membrane is stimulated, and a nerve impulse is triggered

Neuromuscular junction occurs when a nerve cell contacts a muscle 

Comparison of Types of Muscle

Types of Muscle, cont.

Myofilaments

Muscle cells are unique because of the contractible protein fibers, called myofilaments, within them. 

the filaments of myofibrils constructed from proteins are of two types, thick and thin. Thin filaments consist primarily of the protein actin. Thick filaments consist primarily of the protein myosin.

Muscle contraction occurs because of the myosin filaments pull on actin filaments

Skeletal Muscle Characteristics

Most attach to bones by tendon

Cells are multinucleate

Striated—have visible binding

Voluntary Cells surrounded &

bundled by connective tissue

Smooth Muscle Characteristics

Has no striations Spindle-shaped

cells Single Nucleus Involuntary—no

conscious control Found mainly in the

walls of hollow organs

Characteristics of Cardiac Muscle

Has striations Usually has a single nucleus Joined to another cardiac

muscle cell Involuntary Found only in the heart Connects cytoplasm

between 2 cells (Gap junction)Gap junctions are responsible for electrochemical and metabolic coupling. They allow Each heart muscle cell is coupled to its neighbors electrically by tiny holes, producing depolarization of the heart muscle

Skeletal Muscle

Functions of Skeletal Muscle Produce Movement Maintain posture Stabilize joints Generate Heat

Sites of Muscle Attachment Bones Cartilage Connective tissue

coverings

Muscle Fibers blend into a connective tissue attachment

Tendon—cordlike structure Aponeurosis—sheet-like

structure Properties of Muscle

Irritability – ability to receive and respond to a stimulus

Contractibility – ability to shorten when an adequate stimulus is received

Extensibility – ability to lengthen when an adequate stimulus is received

Elasticity – ability to return to normal shape

Anatomy of a Muscle Cell

Each fiber is built up from smaller strands called myofibrils, and each myofibril contains interlaced filaments of muscle proteins.

Naming Skeletal Muscles

Action

Origin&

Insertion

ShapeNumber

OfOrigins

Size

Location

Direction ofMuscleFibers

SkeletalMuscle

Direction of Muscle Fibers

Relative to the Midline RECTUS = parallel to the

midline Rectus Abdominus

TRANSVERSE = perpendicular to midline Transverse Abdominus

OBLIQUE = diagonal to midline External Oblique

Location

Structure near which muscle is found FRONTALIS =

near FRONTAL bone

OCCIPITALIS = near OCCIPITAL bone

Size

Relative Size of Muscle MAXIMUS = largest

Gluteus Maximus MEDIUS = middle

Gluteus Medius MINIMUS = smallest

Gluteus Minimus LONGUS = longest

Fibularis Longus BREVIS = short

Fibularis Brevis TERTIUS = shortest

Fibularis Tertius

Number of Origins

Number of tendons of origin

BICEPS = Two Biceps Brachii Biceps Femoris

TRICEPS = Three Triceps Brachii

QUADRICEPS = Four Quadriceps Femoris

Shape

Relative Shape of the Muscle

DELTOID = triangular shape Δ

TRAPEZIUS = trapezoid shape SERRATUS = saw-toothed ♒

RHOMBOIDEUS = rhomboid shape

TERES = round ○

Origin & Insertion

Origin – attachment to an immoveable bone

Insertion – attachment to a movable bone

ILIO COSTALIS= attaches to the ilium & ribs (costal = ribs)

Action

NAME ACTION EXAMPLE

FLEXOR Decrease angle at a joint Flexor Carpi Radialis

EXTENSOR Increase angle at a joint Extensor Carpi Ulnaris

ABDUCTOR Move bone away from midline Abductor Pollicis Longus

ADDUCTOR Move bone toward midline Adductor Longus

LEVATOR Produce upward movement Levator Scapulae

DEPRESSOR Produce downward movement Depressor Labii Inferioris

SUPINATOR Turn palm upward/anterior Supinator

PRONATOR Turn palm downward/posterior Pronator Teres

Types of Muscle--Actions

Prime mover (Agonist) – 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

Fixator – stabilizes the origin of a prime mover

Head & Neck Muscles

Head & Neck Muscles

Frontalis: elevate eyebrows

Orbicularis Oculi: close eyelid

Zygomaticus: draw angle of lip upward

Buccinator: draws cheeks against teeth

Orbicularis Oris: closes mouth

Platysma: draws lower lip down & back

Cranial Aponeurosis: connects frontalis to occipitalis

Temporalis: elevates mandible

Occipitalis: draws scalp back

Masseter: elevates mandible

Sternocleidomastoid: Flexes head Draws head toward

shoulder

Muscles of Mastication

Masseter: elevates mandible

Temporalis: elevates mandible

Medial pterygoid: elevates mandible

Lateral pterygoid: depresses mandible

Key Muscles of Facial Expression

Smiling Muscles Orbicularis Oculi Nasalis Levator Labii

Superioris Levator Anguli

Superioris Zygomaticus Risorius

Frowning Muscles Frontalis Orbicularis Oris Depressor Anguli

Oris Depressor Labii

Inferioris Mentalis Platysma

Muscles of the Axial Skeleton

Muscles of the Axial Skeleton

Intrinsic Muscles Erector Spinae:

maintain posture of back/extension

• Spinalis• Longissimus• Iliocostalis

Oblique Muscles: rotation of the vertebrae

• Semispinalis• Multifidus• Rotatores

Muscles of Quiet Respiration Diaphragm External Intercostals Internal Intercostals—

deep breaths Abdominal Muscles

External Obliques Internal Obliques Transverse

Abdominus Rectus Abdominus

Quadratus Lumborum

Muscles of Scapular Stabilization

Trapezius: Retraction (M) Elevation (S) Depression (I) Upward Rotation (S, M)

Rhomboid—retraction Levator Scapular—Elevation Pectoralis Major—Protraction Serratus Anterior—Protraction

Anterior Muscles of Shoulder

Deltoid Flexion (A, M)/Extension (P,

M) Abduction (M)/Adduction (A) Internal (A) /External Rotation

(P) Pectoralis Major

Adduction Flexion Extension Internal Rotation

Biceps Brachii—Flexion

Posterior Muscles of Shoulder

Teres Major Adduction Extension Internal Rotation

Latissimus Dorsi Adduction Extension Internal Rotation

Triceps Brachii Adduction Extension

Rotator Cuff Muscles (SITS)

Supraspinatus Abduction

Infraspinatus External Rotation

Teres Minor External Rotation

Subscapularis Internal Rotation

Muscles of the Elbow/Forearm

Triceps Brachii—Extension

Bicep Brachii— Flexion Supination

Brachialis—Flexion Brachioradialis—

Flexion Pronation

Pronator Teres Pronator Quadratus Supinator Longus

Muscles of the Wrist & Hand

Flexor Carpi Ulnaris

Flexor Carpi Radialis

Flexor Digitorum Extensor Carpi

Ulnaris Extensor Carpi

Radialis Extensor Digitorum

Anterior (Palmar) View Posterior (Dorsal) View

Muscles Of Hip:Anterior Muscles

Muscles of Hip:Anterior Muscles Medial/Adductor

Muscles: Adductor Magnus Adductor Longus Adductor Brevis Gracilis

Anterior Muscles Iliopsoas—Flexion Pectineus—

• Flexion• Adduction

Sartorius—• Flexion• Lateral Rotation

Muscles of Hip: Gluteal Muscles

Gluteus Maximus—Extension

Gluteus Medius—Abduction

Gluteus Minimus—Abduction

Tensor Fasciae Latae— Flexion Abduction

** Gluteus Minimus is under the Gluteus Medius

Muscles of Anterior Thigh

“Quadriceps” Rectus Femoris—

• Hip flexion• Knee extension

Vastus Lateralis—knee extension

Vastus Medialis—knee extension

Vastus Intermedius—knee extension

Sartorius—• Hip & Knee Flexion• Lateral Hip Rotation

**Vastus Intermedius is beneath Rectus Femoris

Muscles of Posterior Thigh

“Hamstrings” Responsible for

Knee Flexion & Hip Extension

Semimembranosus Semitendinosus Biceps Femoris

Gastrocnemius Knee Flexion

Muscles of the Lower Leg

Anterior Compartment Tibialis Anterior—Dorsiflexion &

inversion Extensor Digitorum Longus Fibularis Tertius—dorsiflexion &

eversion Posterior Compartment

Gastrocnemius—plantarflexion, knee flexion

Soleus—plantarflexion Lateral Compartment

Fibularis Longus—plantarflexion & eversion

Fibularis Brevis—plantarflexion & eversion

Throwing Movement

Running & Kicking

Tendinitis

Inflammation of tendons and of tendon-muscle attachments

Many patients report stressful situations in their life in correlation with the beginnings of pain which may contribute to the symptoms. If the symptoms of tendinitis last for several months or longer it is probably tendinitis.

Muscular Diseases

Muscular Dystrophy Muscular Dystrophy (MD) is a group of genetic diseases that cause

the muscle fibers to become easily damaged. There are over one dozen different types, but the most common

general symptoms are muscle weakness, lack of coordination and loss of mobility.

The most severe type, Duchenne's muscular dystrophy, can cause mental retardation and primarily affects young boys.

MD is diagnosed through genetic tests, muscle biopsies, blood tests that measure for high levels of creatine kinase and ultrasounds.

There is no cure for MD but it can be treated to reduce the severity with physical therapy, medication, surgery and special braces.

Muscular Diseases Compartment Syndrome

Compartment syndrome occurs when too much pressure builds up in and around the muscles.

It can result from crushing injuries, extended pressure on a blood vessel, swelling inside a cast or complications from surgery.

Symptoms include severe pain, a feeling of fullness or tightness in the muscle and a tingling sensation.

Numbness indicates cellular death and it may be difficult to restore full function once it reaches that point. Surgery to relieve the pressure is usually required.

Fibromyalgia is a medical disorder characterized by chronic widespread

pain and allodynia, a heightened and painful response to pressure

Fibromyalgia is estimated to affect 2–4% of the population, with a female to male incidence ratio of approximately 9:1

Fibromyalgia is considered a controversial diagnosis, due to lacking scientific consensus to its cause

Signs and symptoms: Muscle spanms, weakness, nerve pain, muscles twitching,

palpitations, bowel disturbances, sleep disturbances, short/long term memory, impaired speed performace, inability to multitask, anxiety, depression, RA, headaches, etc…

Mitochondrial Myopathies On biopsy, the muscle

tissue of patients with this disease category usually demonstrate 'ragged red' muscle fibers.

These 'ragged red' fibers contain mild accumulations of glycogen and neutral lipids, and may show an increased reactivity for succinate dehydrogenase and a decreased activity for cytochrome c oxidase.

Examples of Mitochondrial myopathy include:

varying degrees of cognitive impairment and dementia

lactic acidosis (breakdown food) strokes transient ischemic attacks hearing loss Dysmotility (digestive muscles don’t work) weight loss cardiac conduction defects