Naming Skeletal Muscles

Action

Origin

&

Insertion

Shape

Number

Of

Origins

Size

Location

Direction of

Muscle

Fibers

Skeletal

Muscle

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

ABDUCTORMove bone away from

midlineAbductor Pollicis Longus

ADDUCTOR Move bone toward midline Adductor Longus

LEVATOR Produce upward movement Levator Scapulae

DEPRESSORProduce downward

movementDepressor Labii Inferioris

SUPINATOR Turn palm upward/anterior Supinator

PRONATORTurn palm

downward/posteriorPronator 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

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 terminology

Prefix myo refers to muscle

Prefix mys refers to muscle

Prefix sarco refers to flesh

Cardiac muscle tissue• Makes up myocardium of heart

• Unconsciously (involuntarily) controlled

• Microscopically appears striated

• Cells are short, branching & have a single

nucleus

Types of Muscle Tissue:

Smooth (visceral) muscle tissue

• Makes up walls of organs & blood vessels

• Tissue is non-striated & involuntary

• Cells are short, spindle-shaped & have a single nucleus

• Tissue is extremely extensible, while still retaining ability to

contract

Types of Muscle Tissue:

Types of Muscle Tissue:

Skeletal muscle tissue

• Associated with & attached to the skeleton (by tendons)

• Under our conscious (voluntary) control

• Microscopically the tissue appears striated

• Cells are long, cylindrical & multinucleate

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 skeletal muscles (pg. 131)

Skeletal

muscle

fiber (cell)

Muscle

Fascicle

Surrounded by

perimysium

Surrounded by

endomysium

endomysium

perimysium

Skeletal

muscle

Surrounded by

epimysium

epimysium

tendon

Play IP Anatomy of Skeletal muscles (IP p. 4-6)

Microanatomy of a Muscle Fiber

Organization of Skeletal Muscles

This is skeletal muscle

The bundled muscle

fascicles are surrounded

by epimysium

Epimysium

Muscle fascicle

Organization of Skeletal Muscles

This is a muscle

fascicle

It is surrounded by

perimysium and

contains muscle

fibers (cells)

perimysium

Muscle fiber

Organization of Skeletal Muscles

This is a muscle fiber.

Each muscle fiber is a

single cell with multiple

nuclei

It is surrounded by

endomysium and

contains many myofibrils

endomysium

myofibril

Organization of Skeletal Muscle

This is a myofibril

Each myofibril is

surrounded by

sarcoplasmic reticulum

(smooth ER)

Myofibrils are made up of

many sarcomeres (from

Z line to Z line)

Sarcoplasmic reticulum

Sarcomere (unit

between the Z lines)

Organization of Skeletal Muscle

This is a sarcomere

It is made up of thin

filaments and thick

filaments

Thick filament

Thin filament

Microanatomy of a Muscle Fiber (Cell)

sarcolemma

transverse

(T) tubules sarcoplasmic

reticulumterminal

cisternae

myofibril

thin

myofilament

thick myofilament

triad

mitochondria

nuclei

myoglobin

Muscle fiber

myofibril

Thin filaments Thick filaments

Thin myofilamentMyosin molecule of

thick myofilament

sarcomere

Z-line

Z line

Thin

myofilaments

M line

Thick myofilaments

Z line

Myofilaments of sarcomere

Thin Myofilament

(myosin binding site)

Thick myofilament

(has ATP

& actin

binding

site)

*Play IP sliding filament theory p.5-14 for overview of thin &

thick filaments

Sarcomere

Z lineZ line

A band

H zone

I band Zone of

overlap M lineZone of

overlapThin

myofilaments Thick

myofilaments

How do skeletal muscles

contract?

1. A signal is sent from the brain or the spinal

cord to the muscle via neurons

2. An action potential is generated in the

neuron, releasing Ca++ in the neuromuscular

junction

3. The influx of calcium ions causes

acetylcholine (AcH) to be released in the

synaptic cleft

4. AcH binds to the AcH receptors present in

the sarcolemma, increasing its permeability

5. Na++enter the sarcolemma, changing its

polarity and creating an action potential

6. Ca++ are released by the sarcoplasmic

reticulum, as the action potential travels down

the T-tubules in the muscle fiber

7. Ca++ bind with troponin C, causing the

myosin to bind on actin sites

8. ATP is hydrolyzed into ADP and phosphorus,

releasing energy

9. Myosin head bends and actin slides over the

myosin surface (contraction)

10. Myosin releases the ADP molecule

11. Actin is released and returns to original

position (relaxation)

Sliding Filament Theory

Sliding Filament Theory1. Myosin heads attach to actin molecules (at binding [active]

site)

2. Myosin “pulls” on actin, causing thin myofilaments to slide

across thick myofilaments, towards the center of the sarcomere

3. Sarcomere shortens, I bands get smaller, H zone gets smaller,

& zone of overlap increases

4. As sarcomeres shorten, myofibril shortens. As myofibrils

shorten, so does muscle fiber

• Once a muscle fiber begins to contract, it will contract maximally

• This is known as the “all or none” principle

Sliding Filament Theory

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