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Movement

muscular contraction allows locomotion and movement of body contents

Stability

maintain posture by resisting gravity and preventing unwanted movements

Communication

facial expression, body language, writing, speech

Control of body openings and passages

sphincter: ring of muscle

Heat Production

skeletal muscles produce up to 85% of body heat

Muscle Cells

are also called muscle fibers- 10-100um diameter, <30cm long

Endomysium

areolar connective tissue sheath surrounding every muscle cell/fiber

Fascicle

bundle of muscle fibers, make grain in muscle tissue

Perimysium

connective tissue sheath surrounding each fascicle

Muscle

bundle of fascicles

Epimysium

connective tissue sheath around whole muscle

Deep fascia

epimysium sheet between muscles

Superficial Fascia

epimysium sheet between muscles and skin

Tendon

collagen fibers of epimysium that merge into periosteum of bone

Aponeurosis

broad, sheet-like tendon

Retinaculum

band of connective tissue that covers multiple tendons

Origin

stationary end of a muscle; also called the head of the muscle

Insertion

mobile end of the muscle; insertion is pulled towards origin

Belly

middle of muscle

Fusiform

thick in the middle, tapered at the ends; strong contraction

Parallel

long strap-like muscles of uniform width; weaker contraction

Convergent

broad at origin and narrow at insertion; very strong

Pennate

feather-shaped with all fascicles inserting on a long tendon

Circular

(sphincters) rings of muscle around body openings

Muscle Actions

individual muscles may have more than one action

Prime Mover

(agonist) muscle that produces most of force in a joint

Synergist

assists and stabilizes prime mover

Antagonist

opposes prime mover

Fixator

muscle that prevents a bone from moving

Naming muscles: Size

maximus, medius, minimus, major, minor

Naming muscles: Shape

deltoid, trapezius, rhomboideus

Naming muscles: Location

orbicularis oculi, quadriceps femoris, brachialis

Naming muscles: Direction of Fibers

rectus abdominus, external obliques

Rectus

parallel to the body midline

Oblique

diagonal to the body midline

Transverse

horizontal to the body midline

Naming muscles: # of Attachments

biceps brachii, sternocleidomastoid

Naming muscles: Action

pronator teres, adductor magnus, flexor carpi ulnaris

Responsiveness/Excitability

when stimulated by chemical signals, stretch, and other stimuli, muscle cells respond with electrical impulses

Conduction

stimulation can occur locally, but the impulse travels in a wave of excitation over the entire cell

Contractility

muscle cells are unique in their ability to shorten when stimulated

Extensibility

muscle cells can be stretched beyond their resting length

Elasticity

muscle cells recoil to their original resting length after stretching and/or contracting

Skeletal Muscle

attached to one or more bones, has striations of light and dark bands in each cell, has multinucleate cells, and is usually voluntary;

Vermiform Cells

(worm-like) are multinucleate due to their formation from multiple stem cells called myoblasts

Sarcoplasm

Cytoplasm of a muscle cell with an abundance of glycogen (stored glucose polymer) and myoglobin (red pigment to store oxygen)

Sarcolemma

Plasma membrane of a muscle cell. This organelle can receive neurotransmitters from connected neurons and conduct an electrical impulse over its surface and into the interior of the cell

Transverse Tubules (t-tubules)

tube-like extensions of the sarcolemma that descend into the interior of the muscle cell and out the other side

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