-
sarcolemma
muscle plasma membrane
-
sarcoplasm
cytoplasms of a muscle cell
-
myo, mys, and sarco refer to what?
muscle
-
-
-
fascle
bundle of muscle fibers
-
muscle fibers
- long, cylindrical cell
- multiple nuclei underneath sarcoloma
-
myofibrilis
- (muscle fibers)
- contractile elements
- most of muscle volume
-
sarcomeres
- smallest contractile unit of muscle
- 2 types- thick and thin
-
ACTIN
- thick filaments
- thin filaments
-
thick filaments
- extend the entire length of an A band
- myosin
-
thin filaments
- extend across the I band and partway into the A band
- actin, tropomyosin and troponin
-
Z disc
- or Z line
- coin shaped sheet of proteins (connnectins) that anchors the thin filaments and connects myofibrils to one another
-
thin filaments do not what?
overlap thick filaments in the lighter H zone
-
tropomysosin and troponin
regulatory subunits bound to actin
-
sliding filament model of contraction?
- in relax state, thin and thick filaments overlap only slightly
- upon stimulation, myosin heads bind to actin (cross bridge formation) and sliding begins
- think filaments slide past thick filaments
- overlap of actin and myosin filaments increases
-
skeletal muscle contraction
- 1. be stimulated by nerve ending
- 2.produce an electrical current, or action potential, along the sarcolemma
- 3.have a ruse in intracellular Ca levels
-
action potential
electrical current
-
-
-
skeletal muscles are stimulated by what?
motor neurons of the somatic nervous system
-
each muscle is served by?
one nerve containing numerous neurons
-
motor unit?
muscle fibers
-
each neuron controls what?
a number of muscle fibers (motor unit)
-
what is acetyl choline?
a neurotransmitter
-
nerve stimulus of skeletal muscle (phase 1)
- Acetyl Choline is released from presynaptic neuron
- ACh binds its receptors at the postsynaptic motor end plate
- binding opens chemically gated channel
- Na+ diffused through channel and the interior of sarcolemma becomes less negative (depolarization)
- depolarization leads to and action potential that spreads in all directions across the sarcolemma
-
depolarization
when Na+ diffused through channel and the interior of sarcolemma becomes less negative
lose K and gain Na
-
repolarization
- immediately after the depolarization wave passes, Na+ channels are closed and K+ channels open
- K+ diffused from the cell, restoring the electrical polarity in the sarcolemma
-
sarcoplasmic recticulum (SR)
- regulates intracellular calcium levels
- (like the smooth endoplasmic reticulum)
-
T tubules
- penetrate into the cell's interior at each A abnd band junction
- associate with the terminal ciscternae to form triads
- they conduct action potentials to the deepest regions of the muscle
- and signal the release of Ca
-
phase 2
- AP travels across the entire sarcolemma
- AP travels along T tubules
- SR releases Ca; Ca binds to troponin; myosin-binding sites (activate sites) on actin exposed
- myosin heads bind to actin;contracting begins
-
working(power) stroke
myosin head pivots and oulls actin filament toward M line
-
axon terminal does what?
attaches to neuron
-
motor unit
a motor neuron and all the muscle fibers it supplies
-
contraction of a single motor units does what?
causes a weak contraction in the entire muscle
-
muscle that control fine units (fingers and eyes)
have small motor units
-
large weight-bearing muscles(thing, hips)
have large motor units
-
graded muscle responses
- variations in the degree of muscle contraction
- it varies in the # of motor units involved and changing of frequency of stimulation
-
muscle twitch
the responses of a a muscle (single motor unit) to a single, brief threshold stimulus
-
three phases of a muscle twith?
- latent period
- period of contraction
- period of relaxation
-
latent period
excitation contraction coupling is taking place( getting ready to contract, very short)
-
period of contraction
cross bridges actively form and the muscle shortens
-
period of relaxation
Ca is reabsorbed into the SR and muscle tension goes to zero
-
a single stimulus results in a single contractile reponse
muscle twitch
-
wave summation
frequently delivered stimuli (muscle does not have time to relax) increases contractile force (harder twitch)
-
tenanus
- continuous, repeated stimuli results in a maximal sustained contraction
- the muscle locks up
-
the force of contraction is precisely controlled by what?
multiple motor unit summation
-
recruiment
as more neurons are activated, more motor units are stimulated to contract
-
contraction
refers to the force generated by the formation of myosin across bridges
-
shortenin
tension generated by the cross bridge exceeds forces opposing shortening
-
isometric contractions
increasing muscle tension (muscle does not shorten during contraction)
-
isotonic (concentric) contraction
decreasing muscle lengh (muscle shortens during contraction)
-
eccentric contraction
the muscle contracts as it lengthens
-
muscle metabolism
- creatine phospahte 1
- anaerobic glycolysis 2
- aerobic respiration 3
-
muscle fatigue
the muscle is in a state of physiological inability to contract
-
what causes muscle fatigue?
- ATP production fails to keep pace with ATP use
- Myosin crossbridges cannot slide and get "stuck" causing contractures
- the inability to mantain na and K gradients
- lactic acid accumulates and causes pain
-
what must happen so muscle can return to a resting state?
- oxygen reserves must be replenished
- ATP and CP reserves must be resynthesized
- lactic acid must be converted to pyruvic acid
- glycogen must be replaced
-
oxygen debt
the extra amount of O2 needed for the muscle to return to a resting state
-
-
glycolitic
- fermentation
- quick but inefficient supply of ATP
- requires alot of glucose
-
oxidative
- slow but alot of ATP
- response is limited by krebs cycle and ETC
-
fast muscle fibers
- White
- glycolytic
- need alot of glucose
- rapid power contractions
-
slow muscle
- red
- oxidative
- sustained contraction
-
peristalsis
wavelike series of contractions that move things in smooth muscle like food
|
|
