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