Chp 9: Muscles Flashcards
What percentage of person’s body mass is muscle tisuse?
40%
Skeletal Muscle
Attached to bones or (some facial muscles) skin
Facial expression, movement, heat, posture
Multinucleate cells, cylindrical, obvious striations, fibers parallel
Voluntary control
Cardiac Muscle
Walls of the heart
Pumps blood continuously
Branching chains of cells, uni or bi-nucleate, striations, intercalated discs
Involuntary
Smooth muscle
GI tract, uterus, eye, blood vessels
Peristalsis, blood pressure, pupil size, erects hair
One central nucleus, no striations
Direct attachment to bone
Aka fleshy
Epimysium of muscle is fused to periosteum of bone or perichondrium of cartilage
Indirect attachment to bone
Muscle’s connective tissue wrappings extend beyond muscle as ropelike tendon or sheetlike aponeurosis
Indirect attachments more common b/c of durability and small size
Sarcolemma
Plasma membrane of muscle cell
Epimysium
Overcoat of connective tissue that covers whole muscle
Perimysium
Connective tissue of collagen and elastic fibers that surrounds each fascicle
Endomysium
Connective tissue that surrounds each individual muscle fiber
Muscle tissue organization at tissue level
Each muscle fiber (muscle cell) is wrapped in endomysium
Each bundle of muscle fibers is called a fascicle, which is wrapped in perimysium
The epimysium surrounds the whole muscle
fiber- endomysium –> fascicle-perimysium –> muscle- epimysium
Sarcoplasm
cytoplasm of muscle cell
Myofiber
Muscle cell
Myofibril
Cytoskeletal elements in sarcoplasm, contains sarcomeres
Sarcomere
Region of myofibril between 2 successive Z discs; functional unit of skeletal muscle
“muscle segment”
A bands
Dark bands on myofibrils
Myosin filaments
I bands
Light bands on myofibrils
Actin only
Sarcoplasmic Reticulum
Elaborate smooth endoplasmic reticulum; interconnecting tubules surround each myofibril
Regulates intracellular levels of ionic calcium
T Tubule
Elongated tube, continuation of sarcolemma extending deep into cell interior Conduct impulses (signal for every myofibril to contract at same time)
Motor Unit
One motor neuron and all the muscle fibers it innervates
Many motor neurons per muscle
The fewer # of fibers per neuron, finer the movement
Blood and Nerve Supply of skeletal muscles
One nerve and its branches (voluntary control)
An artery and its branches
One or more veins and their branches
Origin
Attachment of muscle to immovable bone
Insertion
Attachment to moveable bone
Skeletal muscle regions: Anterior View (10)
Facial Neck Shoulder Arm Forearm Thorax Abdomen Pelvis/Thigh Thigh Leg
Skeletal muscle regions: posterior view (7)
Neck Shoulder Arm Forearm Hip Thigh Leg
H zone
where only thick filaments are present
striated appearance of skeletal muscles
Repeated overlapping of I and A bands
H zone
where only thick (myosin) filaments are present
M Line
Proteins of M Line connects central portion of each thick (myosin) filament to its neighbors
Dark staining proteins, help stabilize positions of thick filaments
Myosin
thick contractile protein
each molecule resembles 2 golf clubs twisted together
myosin heads (cross bridges) extend toward thin filaments
Actin
Thin filaments
The myosin-binding site on each actin molecule is covered by tropomyosin in relaxed muscle
Regulatory proteins
turn contraction on/off
troponin and tropomyosin
Structural proteins
provide proper alignment, elasticity, and extensibility
titin, myomesin, nebuilin, dystrophin
Prime Movers/ Agonist
muscle responsible for most of the movement
ex// biceps brachii, flexion of forearm
Antagonists
Extensor/Flexor pair
oppose/reverse particular movement
ex// triceps brachii/biceps brachii
Synergists/Fixators
Help agonists
Add extra force to movement or reduce undesirable/unnecessary movement
ex// extensor carpi muscles are synergists for flexor digitorum when you clench fist
