Muscular System

MUSCULAR SYSTEM ¡ 600+ muscles in the body

¡ Bundles of muscle fibers held together with connective tissue

¡ Properties of muscles ¡ Excitability/irritability ¡ Contractibility ¡ Extensibility ¡ Elasticity

Properties of Muscles ¡  Excitability: the muscles ability to respond to a

stimuli, from a nerve

¡  Extensibility: the muscles ability to be stretched

¡ Contractibility: the ability of the muscle to become shorter in response to stimuli

¡  Elasticity: The muscles ability to return to it’s normal shape

MUSCLE TYPES

¡ Cardiac—involuntary

¡ Visceral or smooth—involuntary

¡ Skeletal—voluntary

Cardiac Muscle Characteristics ¡  Located in heart

¡  Short Branching fibers

¡  Striated

¡  They contain a single nucleus that is centrally located

¡  Contains intercollated discs, that act as junctions in order for contractions to move faster within fibers

¡  Perform rapid involuntary contractions

Smooth Muscle Characteristics ¡  Located in the walls of hollow

organs: intestines

¡  Long spindle shaped fibers

¡  Single nucleus

¡  Non-striated

¡  Involuntary Control

¡  Fibers are linked together which allows fibers to excite each other: allows peristalsis

Skeletal Muscle Characteristics ¡  Found in skeletal muscles

¡  Notable striations alternating light and dark

¡  Multinucleated

¡  Voluntary Contractions: Rapid and Forceful

Functions of Muscles

¡ Attach to bones to provide movement

¡ Produce heat and energy

¡ Help maintain posture

¡ Protect internal organs

Attachments to Bone ¡ Tendon: Strong connective tissue that

is capable of undergoing tension ¡ Fascia: connective tissue that

surrounds muscle and other structures ¡ Origin: attachment end of the muscle

to the non-moving bone ¡  Insertion: attachment of the muscle

to the moving bone

Actions or Movements of Muscles ¡ Adduction

¡ Abduction

¡ Flexion

¡ Extension

¡ Rotation

¡ Circumduction

Muscle Tone ¡ Partially contracted at all times ¡ Muscle tone allows for state of readiness

¡ Atrophy: loss of muscle tone/size

¡ Hypertrophy: increase in muscle size

Major Muscles of the body: Upper body ¡  Biceps Brachii: Produces

elbow flexion: flexes the lower arm towards upper arm

¡  Triceps Brachii: Produces elbow extension: extends the lower arm away from upper arm

Muscles of the upper body Trapezius: 3 total muscles in group

Upper Trapezius

Middle Trapezius

Lower Trapezius

Responsible for extending the head and moving the shoulder

Major Muscles ¡  Deltoid: 3 total in group

¡  Anterior Deltoid

¡  Middle Deltoid

¡  Posterior Deltoid

¡  Responsible for shoulder abduction

¡  Common injection site

Major Muscles: torso

¡  Sternocleidomastoid

¡  Located in neck

¡  Responsible for turning and flexing head

¡  Pectoralis: 2 muscles total in chest

¡  Pectoralis Major

¡  Pectoralis Minor

¡  Together responsible for adduction of arm: moving arm across body

Major Muscles ¡  Intercoastal Muscles:

¡  Located in between each rib

¡  Assist with breathing

¡  Rectus Abdominus:

¡  Located on front of abdomen

¡  Assists with flexing torso: compressing the upper torso

Major Muscles: lower leg ¡  Tibialis Anterior: located on

front of shin

¡  Responsible for pulling the foot upward towards shin and inverting foot

¡  Gastrocnemius: located on back of lower leg

¡  Responsible for plantarflexion: pointing toe

¡  Achilles Tendon: attaches gastroc to heal

¡  Major tendon in body

Major Muscles: thigh ¡  Quadriceps Muscles: 4 total

muscles

¡  Rectus Femoris: Center of thigh

¡  Vastus Medialis: Medial thigh

¡  Vastus Laterallis: Lateral thigh

¡  Vastus Intermedius: Under Rectus Femoris on center of thigh

¡  As a group: Responsible for knee extension: straightening the leg

Major Muscles: thigh ¡  Hamstrings: 3 total muscles

¡  Semimembranosis: posterior medial thigh

¡  Semitendinosis: posterior lateral thigh

¡  Biceps Femoris: Center of posterior thigh

¡  As a group: responsible for flexing knee: bending knee

¡  Sartorius: longest muscle in body

¡  On front of thigh: abducts and flexes leg

Major Muscles: thigh ¡  Gluteal Muscles: 3 total

¡  Gluteus Maximus: common injection site

¡  Gluteus Medius

¡  Gluteus Minimus

¡  As a group: responsible for hip abduction: moving leg away from body: midline