PLTW HBS Make up of a Muscle & Building Muscle 1.2.2 - 1.2.3

Endomysium

Connective tissue surrounding a muscle fiber

Epimysium

covers the entire skeletal muscle

Perimysium

Connective tissue surrounding a fascicle

tendon

Connects muscle to bone

Muscle cell (fiber)

bundle of myofibrils

Myofibril

tightly packed filament bundles found within skeletal muscle fibers

6 muscle rules

1. must have 2 attachments and cross at least 1 joint

2. muscles always pull and get shorter

3. the attachment that moves is known as insertion and the stationary attachment is known as the origin

4. muscles that *decrease* the angle between ventral surfaces of the body are known as *flexors*; muscles that *increase* the angle are *extensors*

5. muscles work in opposing pairs

6. muscle striations point to the attachments and show the direction of pull

origin

attachment of a muscle that remains relatively fixed during muscular contraction

Insertion

The attachment of a muscle tendon to a moveable bone or the end opposite the origin

Brachialis

flexes forearm

triceps brachii

extends forearm

intercostal muscles

Muscles which move the rib cage during breathing

pectoralis major

Adducts and flexes humerus

pectoralis minor muscle

protracts and depresses scapula

flexor

a muscle that bends a part of the body, such as an arm or a leg

extensor

muscle that straightens a joint