Muscle System Flashcards
sarco-
flesh
myo-
muscle
mys-
muscle
functions of muscle system
- movement
- maintain posture
- stabilizes joints
- generates heat
types of tissue
- skeletal
- cardiac
- smooth
anatomy of skeletal muscle
- fibers are enclosed by endomysium
- many endomysii are wrapped together by the perimysium
- one group of fibers wrapped in perimysium is called a fascicle
- all fascicles are wrapped together in epimysium
- blended into tendons or aponeuroses
aponeuroses
layers of flat, broad tendons
sarcolemma
plasma membrane of skeletal muscle
myofibrils
long, ribbon-like organelles filling majority of cytoplasm
sarcomere
basic unit of muscle (I and A bands)
I and A bands
myofilaments
-give the appearance of striation
2 types of myofilaments
- thick
- thin
thick filaments
composed of myosin and ATP enzymes
thin filaments
composed of actin and regulatory proteins
sarcoplasmic reticulum
- surrounds each myofibril
- plays a role in storing and releasing calcium during contraction
2 main functions of muscles
-irritability and contractility
irritability
-receive and respond to stimuli
contractility
shorten when stimuli is applied
nerve stimulis
- muscle cells must be stimulated by nerve impulses to contract
- cells join at neuromuscular junctions
- gap b/w is called synaptic cleft
- when impulse reaches neuromuscular junction, a neurotransmitter is released
- neurotransmitter travels across synaptic cleft and attaches to sarcolemma
- if enough neurotransmitter reaches the sarcolemma, then Na ions rush into muscle cell and generate electrical current called action potential
- causes contraction
neuromuscular junctions
- where muscle cells join
- don’t touch, but very close
synaptic cleft
gap between neuromuscular junctions
-filled w/ fluid
motor unit
1 neuron and all skeletal muscles that it stimulates
muscle contraction mechanism(sliding filament theory)
- when muscle fibers are activated by the nervous system, cross bridges attach and detach to myosin on the thin filaments and sliding begins
- powered by ATP
- contraction requires Ca until action potential ends, then Ca is stored into sarcoplasmic reticulum
contraction of skeletal muscle
- skeletal muscles consist of thousands of muscle cells
- react with graded responses
- produced by changing frequency of muscle stimulation or changing # of muscle cells being stimulated
graded responses
different degree of shortenings
muscle twitches
single, brief, jerky contractions
fused tetanus(complete tetanus)
muscles move through an accumulation of nerve impulsed
unfused tetanus(incomplete)
steps leading to fused tetanus
of stimuli in contraction
force of muscle contraction depends on how many cells are stimulated
- when only a few cells are stimulated, contraction as a whole will be slight
- when all motor units are active, contraction is very strong
ATP for contraction
- as muscles contract, the bonds of ATP are hydrolyzed to release needed energy
- muscles store only 4-6 seconds worth, so ATP must be regenerated
3 pathways for ATP regeneration
- direct phosphorylation of ADP by creatine phosphate
- aerobic respiration
- anaerobic respiration
direct phosphorylation of ADP by creatine phosphate
- CP transfers high energy phosphate to ADP molecule, resulting in ATP (yields 1 ATP per CP)
- anaerobic
- muscles store 5x as much CP as ATP; however, CP supplies are exhausted in about 15-20 seconds
aerobic respiration
- glucose is broken down into CO2, H2O, and up to 36 ATP (per 1 glucose model)
- requires O2, amino acids, fatty acids
- slow process but allows muscles to contract for hours
anaerobic glycolysis and lactic acid formation
- glycolysis breaks glucose into pyruvic acid and 2 ATP (per 1 glucose molecule)
- if O2 is not present then pyruvic acid is broken into lactic acid (yields 5% of ATP for aerobic respiration) (faster process and provides ATP for 30-60 seconds of strenuous muscle activity)
muscle fatigue
inability of a muscle to contract even though it is being stimulated
- occurs bc of O2 debt
- depending on blood supply, lactic acid accumulation and low ATP, causes muscle to contract less and less effectively, then stop
o2 debt
-person can’t take up enough o2 fast enough to keep muscle supplied
types of muscle contractions
isotonic
-isometric
isotonic contraction
- myofilaments slide, causing muscle to shorten and movement occurs
- ex: bending knee, rotating arm, smiling
isometric contractions
- myofilaments attempt to slide but are unable to due to immovable object and tension builds up
- ex: attempting to move 400 lbs alone or pushing against a wall
adduction
movement of a limb toward the body midline
circumduction
combination of flexion, extension, abduction, and adduction, where proximal end of limb is stationary and its distal end moves in a circle
dorsiflexion
standing on heels
plantar flexion
pointing the toe
inversion
-turning the sole of the foot medially
eversion
-turning the sole laterally
opposition
movement of the thumb to touch the tips of the other fingers
supination
rotating the forearm laterally so the palm faces anteriorly (anatomical position)
pronation
rotating the forearm medially so the palm faces posteriorly
