Muscles

tonic

continual partial contraction; ie. Posture

flexors

decrease angle of a joint

depression

down

abduction

out from medial line

reasons for names

1. action 2. direction of fibers 3. location 4. number of divisions 5. shape 6. points of attachment 7. size

Graded strength depends on

1. metabolism/health 2. length of fibers 3. number of fibers 4. load

General functions of the muscular system

1. movement 2. posture 3. heat production

Skeletal Muscle Tissue Characteristics

1. voluntary 2. cells are called fibers 3. fibers are arranged in bundles called fascicles 4. striated 5. attached to bones via tendons 6. supply the strongest contraction 7. mostly protein composed of filaments 8. many nuclei per fiber 9. many mitochondria per fiber 10. will fatigue 11. all or nothing law 12. graded response during contraction

Functions (Contractions)

Thick and thin filaments combine forming cross bridges. Thin filaments are pulled toward middle of sarcomere

endomysium

a broad sheet of dense connective tissue that may attach a muscle to a bone or to another muscle

muscle fiber

a single cell of skeletal muscle tissue

perimysium

a thick band of dense connective tissue that forms most connections between muscle and bone

cross striae

a) dark stripes called A bands; light H zone runs across midsection in each dark A band b) light stripes called I bands; dark Z line extends across center of each light I band

function-contraction - basic principles

a) skeletal muscles contract only if stimulated; natural or electric b) skeletal muscle contractions are of several types c) skeletal muscles contract according to the graded strength principle in contrast to individual muscle cells that compose them d) skeletal muscles produce movement by pulling on insertion bones across joints e) bones serve levers and joints fulcrums of these levers f) muscles that move a part of not usually lie over that part but proximal to it g) skeletal muscles usually act in groups

Names of bursar that frequently become inflamed (bursitis)

a. subarcomial b. olecranon c. prepatellar

fibrillation

abnormal contraction where different muscle fibers contract at different times causing a "flutter"

function of bursae

acts as cushion, relieving pressure between moving parts

synergist

assists

subarcomial

between deltoid muscle and head of humorous and acromion process

olecranon

between olecranon process and skin; known as students elbow

prepatellar

between platella and skin; inflammation called housemaids knee

Aponeurosis (connective tissue)

broad flat sheet of fibrous connective tissue

sarcoplasmic reticulum

calcium storage occurs here, it is similar to the endoplasmic reticulum of other cells

rotators

cause part to pivot on axis

Proteins (Thin Filaments)

composed of actin, tropomyosin, and troponin molecules arranged in a complex fashion, thick filaments attach to Z lines, extend from them in toward center of sarcomeres; thick and thin filaments alternate in myofibrils

Proteins (Thick Filaments)

composed of myosin molecules; heads of myosin molecules help form cross bridges for contraction

inguinal canal

contains spermatic cords; hernia in men most prevalent

age changes

decreased muscular strength, resulting in part from fibrosis

muscles that move a part

do not usually lie over that part but proximal to it

antagonist

does the coming back

Endomysium (connective tissue)

extension of perimysium between individual muscle fibers

Perimysium (connective tissue)

extensions of epimysium, portioning each muscle into bundles of fibers

umbilicus

feature of gastropod

Epimysium (connective tissue)

fibrous connective sheath that envelops each muscle

prime mover

first movement

skeletal muscles usually act in

groups rather than singly

femoral rings

hernia in females most prevalent

circumduction

in a circle

adduction

in to the medial line

extensors

increase angle of a joint

extension

increases angle of joint

deep fascia (connective tissue)

layer of dense fibrous connective tissue underlying superficial fascia under the skin; extensions of deep fascia form epimysium, etc., and enclose viscera, glands, blood vessels, nerves

flexion

lessens angle of joint

bones serve

levers and joints fulcrums of these layers

depressors

lower part

tensors

make rigid

mitochondria

most of the energy for the contraction of a muscle cell is furnished by the ATP of this

abductors

move bone away from midline of body

adduction

move bone toward midline of body

All-or-nothing law

muscle cells obey all-or-nothing law when they contract. They either contract with all force possible under exiting conditions or they don't contract at all

isometric

muscle length stays the same with increasing tension; no movement

isotonic

muscle shortens but its tension increases; produce movement

tension

no movement

Myofibrils

numerous fine fibers packed close together in sarcoplasm

nerve supply

one motor neuron, together with the skeletal muscle fibers it supplies is a motor unit. the fewer muscle fibers involved with each motor unit, the more precise the movement

supination

palms facing anterior

pronation

palms facing posterior

retraction

part backward

protraction

part forward

rotation

pivot

skeletal muscles produce movement by

pulling on insertion bones across joints

twitch

quick, jerky contraction in response to single stimulus; rare

levators

rais part

sphincters

reduce size of an opening

Sarcomere

section of myofibril extending from one Z line to the next; each myofibril consists of many sarcomeres

Bursae

small connective sacs lined with synovial membrane and containing synovial fluid

eversion

sole pointing laterally

inversion

sole pointing medially

treppe

staircase phenomenon; muscles contract more forcefully after they have contracted a few times

Tendon (connective tissue)

strong, touch cord continuous at one end with fibrous wrappings of muscle and at the other end with the tough covering of a bone (periosteum)

tetanic

sustained smooth contraction produced by a series of stimuli

elasticity

the ability of a cell to return to its resting form after stretching

contractility

the ability of a muscle cell to shorten in length

extensibility

the ability of a muscle cell to stretch

excitability

the ability to receive and respond to a stimulus

deep fascia

the connective tissue that binds a muscle and provides a route for blood vessels and nerves to travel

sarcoplasm

the cytoplasm of a muscle cell

epimysium

the outermost covering of the entire muscle

sarcolemma

the plasma membrane of a muscle cell

fascia

the type of fascia that surrounds a muscle

skeletal is found where

the type of muscle tissue found in the muscular system

plantar flexion

toes point flat

dorsiflexion

toes point up

opposition

touch all fingers to thumb

Tendon sheaths (connective tissue)

tubes of fibrous connective tissue that enclose certain tendons, notably those of the wrist and ankle; synovial membrane lines tendon sheaths

pronators

turn palm down

supinators

turn palm up

convulsion

uncoordinated tetanic contractions of varying groups of muscles

elevation

up

how to deduce muscle actions

where muscle is attached movement produced know origin and insertion

Location of Bursae

wherever pressure is exerted over moving parts a. between skin and bone b. between tendons and bone c. between muscles or ligaments and bone

Structure (size, shape, and fiber arrangement)

wide variation in different muscles

age changes- fibrosis

with advancing age some skeletal muscle fibers degenerate and are replaced with fibrous connective tissue