Chapter 9 - Muscles Flashcards
What is myology?
The scientific study of muscles.
What mass of the body is muscle?
45%.
Functions of muscle?
Maintain posture and body position, movement, heat production, guard orifices, and support visceral organs.
Muscle tissue is?
Excitable, extensible, elastic, and contractile.
What does excitability mean?
The ability to receive and respond to electrical or chemical stimuli.
What does contractility mean?
The ability to shorten forcibly when stimulated.
What does elasticity mean?
The ability to return to original shape after being stretched.
What does extensibility mean?
The ability to be stretched without damaging the tissue.
Are muscles organs?
Yes.
What do muscles consist of?
Connective tissue, arteries/veins nerves, lymphatics, and contractile muscle cells.
Characteristics of skeletal muscle?
Attaches to bone, skin or fascia, striated with light & dark bands, voluntary control, long, thin and multi-nucleated fibers, attach to and cover bony skeleton, contracts rapidly, but tires easily, and may exert great force.
1 muscle cell equals?
Fiber.
What is the belly of the muscle?
Main portion of a muscle.
Where does the belly attach?
Tendons.
Tendons attach to what?
Bone.
What is deep fascia?
Dense irregular CT around muscle, holds it in place and separates it from other muscles.
What is subcutaneous fascia?
Loose CT beneath skin, surrounds several muscles.
What is superficial fascia?
Areolar and adipose tissue layer and sits deep to cutaneous membrane.
What are many muscle fibers bundled together into groups called?
Fascicles.
Characteristics of fascicles?
10-100 muscle cells (fibers), several fasicles make up a muscle.
What are the connective tissues of skeletal muscle?
Epimysium, perimysium, and endomysium.
What is epimysium?
Surrounds the whole muscle.
What is perimysium?
Surrounds fascicles.
What is endomysium?
Separates individual muscle fibers (cells).
All connective tissue extend beyond the muscle belly forming?
Tendon.
What is a tendon that is a thick flattened sheet?
Aponeuroses.
What are myoblasts?
Embryonic cells that fuse to form muscle fibers.
What are myosatellite cells?
Myoblast that do not fuse.
What do myosatellite cells do?
Assist in repair of damaged cells.
What are muscle fibers composed of?
Sarcoplasm, Sarcolemma, and Transverse (T) tubules.
What is sarcoplasm?
Fiber cytoplasm.
What is sarcolemma?
Plasma membrane of a fiber.
What are transverse (T) tubules?
Extensions of the sarcolemma into the sarcoplasm.
What are myofibrils?
Contractile organelles that extend the length of fiber and surrounded by sarcoplasmic reticulum.
What is a functional unit of a myofibril?
Sarcomere.
What are sarcomeres made of?
Thick and thin filaments.
What are thick filaments composed of?
Myosin.
Myosin characteristics?
Twisted protein with globular heads, 1.6um long, and 500/thick filament.
What are thin filaments composed of?
Actin and Regulatory proteins.
Actin characteristics?
Structural protein and coiled “beads”
Regulatory protein characteristics?
Allow/prohibit attachment between actin and myosin.
What are the 2 types of regulatory proteins?
Tropomyosin and troponin.
These cause the striated appearance?
Sarcomere “bands”.
What are the types of sarcomere bands?
A bands, I bands, H bands, and zone of overlap.
A band?
Entire thick filament range.
I band?
Only thin filaments.
H band?
Only thick filaments.
Zone of overlap?
Both filaments.
These divide and flank the sarcomere?
Sarcomere “lines”.
Types of sarcomere lines?
Z line and M line.
Z line?
The end of the sarcomere, made of actinin protein, and anchor thin filaments.
M line?
Middle of the sarcomere and stabilize thick filaments.
What are the types of structural proteins?
Titin, Nebulin, and Actinin.
What does titin do?
Anchors a thick filament to a Z line and accounts for elasticity and extensibility.
What does nebulin do?
Holds F actin together on thin filaments.
What does actinin do?
Makes up Z line.
What is the sliding filament theory?
Actin sliding over the myosin.
What happens as actin slides over myosin?
Zone of overlap enlarges, H band shrinks, I band shrinks, A band remains the same, and the Z line moves closer to the A band.
What comprise the neuromuscular junction?
motor unit, synaptic terminal, motor end plate, synaptic cleft, and neurotransmitter.
What is the neuromuscular junction?
The point of contact between the neuron and the muscle.
How is the tension produced by a muscle determined?
The frequency of stimulation and number of motor units stimulated.
What is the All-or-None law?
All fiber in a motor unit fully contract if stimulated.
What is recruitment?
Steady increase in tension by increasing the number of contracting motor units.
What is tetanus?
Muscle never begins to relax, continuous fused contraction.
What is muscle tone?
Motor units contract randomly and tension, but no movement.
What can muscle tone do?
Stabilize joints, hold objects in place, and maintain posture.
What is hypertrophy?
Constant, exhaustive stimulation increases the number of organelles/ proteins in a fiber and overall enlargemtn of the muscle.
What does hypertrophy increase?
Mitochondria, glycolytic enzyme reserves, myofibrils, filaments within myofibrils.
Do muscle fibers reproduce?
No.
What is atrophy?
Lack of constant motor neuron stimulation reduces organelles and proteins.
What causes atrophy?
Age, hormones, lack of use, and nerve damage.
Is muscle atrophy reversible?
Yes, if the fiber is not dead.
What is the origin of a muscle?
Attachment site that does not move.
What is the insertion of a muscle?
Attachment site that moves.
Parallel muscle characteristics and example?
Fasicles parallel to long axis and unidirectional force. Biceps brachii.
Convergent muscle characteristics and example?
Fan shaped, multidirectional force, versatility, and generates least amount of force. Pectoralis major.
Pennate muscle characteristics and example?
Feather-shaped, fascicles oblique to long axis, tendon passes through muscle, and greatest force. Deltoid.
Circular muscle characteristics and example.
Concentric fascicles around openings, and contraction decreases lumen diameter. Orbicularis oculi.
What is uniaxial and movements?
Rotation around one axis. Rotation (atlanto-axial and pivot joints) Angular (Knee and interphalangeal joints).
What is biaxial and movements?
Movement occurs along 2 axes. Angular motion: flexion/extension and abduction/adduction.
What is multiaxial and movements?
Movement on all axes. Angular motion : flexion/extension and abduction/adduction, rotation and circumduction.
Events of muscle contraction?
Ach stored in synaptic vesicles, Ach released, Ach crosses gap & binds to receptors, impulse travels through motor end plate down T tubule to SR Ca2+ diffuse into sarcoplasm, Ca2+ exposes active site, myosin binds, ATP is used and contraction occurs, and contraction keeps occuring as long as Ca2+ concentration is high.
Events of muscle relaxation?
Ach decomposed by AChE, Ca2+ transported back to SR, actin & myosin links broken, cross-bridges move back, and active site is blocked once again.
Types of muscle action?
Agonist, antagonist, synergist and fixator.
What does agonist mean?
Main muscle causing directional force.
What does antagonist mean?
Muscle that contracts to oppose agonist.
What does synergist mean?
Muscle that assists/ modifies movement.
What does fixator mean?
Muscle that stabilizes elements associated with agonist.
Levers can change what?
Magnitude of force, speed, direction, distance of limb movement.
What are the components of lever system?
Lever (L) = skeletal element
Effort (E) = applied force (AF)
Fulcrum (F) = joint
Resistance (R) = body part or object moved.
Types of levers?
First class, second class, and third class.
What is a first class lever?
See-saw, R opposite of E with F central.
What is a second class lever?
Wheel-barrow, E opposite of F to move R.
What is a third class lever?
Shovel, E in between F and R.
What are the types of skeletal muscle fibers?
Fast fibers, slow fibers, and intermediate fibers.
Fast fiber characteristics?
Fast acting, high energy requirement, anaerobic, large diameter, densely packed myofibrils, large glycogen reserves, few mitochondria, and rapid, powerful brief contractions (light color).
Slow fiber characteristics
More myoglobin. slower sustained contraction, aerobic, small diameter, longer to contract, and contract for longer time (dark color).
Intermediate fiber characteristics?
Attributes of both, similar to fast fibers, greater resistance to fatigue, and exercise or lack of can change one muscle type to another.
Smooth muscle characteristics?
Attached to hair follicles in skin, in walls of hollow organs & BVs, nonstriated, involuntary control, contractions are slow and sustained, spindle shaped, very elastic, and resistant to fatigue.
Smooth muscles are stimulated by?
Nervous system, hormones, ions, stretching.
Types of smooth muscle?
Single-unit and multi-unit.
Single-unit characteristics and examples?
Many gap junctions, sheets of spindle-shaped cells, contracrt together BVs, digestive, respiratory, and urinary tracts.
What is the term for contracts together?
Syncytial contraction.
Multi-unit characteristics and examples?
No or few gap junctions, separate fibers, contract independently, and only contract when stimulated by motor nerve. Walls of large BVs, uterus, and iris of eye.
Cardiac muscle characteristics?
Striated in appearance, involuntary control, autorhythmic, network of fibers with intercalated disks at ends, and found only in heart.
