muscular system. muscles in humans there are approximately 650 muscles in the human body, each...
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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