chapter 10 flashcards
major functions of muscle tissue
movement, temp, posture
contractability
ability to contract and pull proteins together, respond to a stimulus in order to contract
excitability
the ability of muscle fibers to generate electrical impulses in response to stimuli
conductivity
respond to electrical signal , continue to travel
distensibility
able to stretch without being damaged
elasticity
able to return to normal position after being stretched
sliding filament theory
thin filaments slide towards the center of each sarcomere
resting membrane potential
90 mV, muscle cell potential
polarized membrane potential
difference in electrical charge across cell membrane
ion channels
ions cannot diffuse through lipid component of plasma membrane , rely on specific protein channels
leak channels
always open , continuously allow ions to flow down concentration gradients between cytosol and ecf
gated channels
closed at rest, open in response to specific stimulus
electrochemical gradient
diffusion of ion across plasma membrane is determined by both concentration gradient and electrical gradient
concentration gradient
diffusion of an ion from high to low concentration, move out
electrical gradient
movement of ion away from a like charge and towards opposite charge, move in
generating a resting potential
electrical gradient favoriting diffusion out , potassium out sodium in
action potentials
brief changes in membrane potential of cell from resting negative value to positive value then back to resting negative , generated by opening and closing of gated sodium and potassium channels in plasma membrane in response to stimulus
resting stage
before stimulus arrives the membrane is resting membrane potential and gated na and k are closed
depolarization stage
response to stimulus , na and k channels open and sodium enters cell making membrane less negative
repolarization stage
sodium channels close while k channels open and k leaves the cell making membrane potential more negative inside positive and outside negative
propagation
action potential able to move entire length of cell membrane
neuromuscular junction
connection between a motor nerve and a muscle fiber that allows electrical impulses to convert into muscled contractions
motor neuron
send motor message, to do, message
synapse
where single motor neuron communicates with many muscle fibers
axon terminal
bulb, end of motor neuron
synaptic cleft
space between neuron and muscle cell
motor end plate
region of muscle cell directly under axon
excitation phase
- Action potential arrives at the axon terminal and triggers calcium channels in axon terminal to open
- Calcium ions move into the axon terminal and trigger exocytosis of synaptic vesicles.
- Synaptic vesicles release ACh into synaptic cleft
- ACh binds to receptors on the motor end plate
- Sodium ion channels open and sodium ions enter the muscle fiber
- Sodium entry depolarizes the sarcolemma creating an end-plate potential
excitation contraction coupling
- End-plate potential stimulates an action potential
- Action potential is propagated down the T-tubules
- T-tubule depolarization leads to the opening of calcium ion channels in the sarcoplasmic reticulum and calcium ions enter the cytosol
- Calcium ions bind to troponin
- Tropomyosin moves and the active sites on actin are exposed
contraction phase (crossbridge)
- ATP hydrolysis “cock” the myosin head
- Myosin head binds to actin
- Power stroke occurs when the phosphate detaches from the myosin head and myosin pulls actin toward the center of the sarcomere (m line)
- ATP breaks the attachment of myosin to actin
muscle relaxation
- Acetylcholinesterase degrades the remaining ACh and the repolarization occurs
- The sarcolemma returns to its resting membrane potential and calcium ion channels in SR close
- Calcium ions are pumped back into the SR
- Troponin shifts and pulls tropomyosin back into position to block active sites of actin and the muscle relaxes
- Relaxation is a passive process
creatine phosphate
muscle fibers, easily can donate phosphate ion
anaerobic catabolism
glucose breaks down absorb into muscle , 2 pyruvate molecules and 2 atp, no oxygen needed
aeorbic catabolism
reactions that require oxygen
muscle twitch
smallest muscle contraction
latent period
time for action potential to propagate across sarcolemma
contraction period
repeated crossbridge cycles generate tension
relaxation period
calcium ions levels reduced in cytosol by SR pumps :tension diminishes
refractory period
between the start of latent period and into start of contraction period where the muscle fibers cannot respond to another stimulus
wave summation
repeated stimulation of muscle fiber
unfused (incomplete) tetanus
pause in between twitch, tension is low
fused (complete)tetanus
brain sends message so fast allowing fast contraction
type 1 fiber, slow twitch
-small diameter, slow-twitch fibers; contract slowly, produce less force for longer period of time
-Rely on oxidative catabolism; large numbers of mitochondria and myoglobin molecules, well-developed blood supply; “dark muscle”
-Predominate in postural muscles; sustain contractions for long durations
type 2 fibers, fast twitch
-large diameter, fast twitch fibers, fatigue quickly
-High myosin ATPase activity; rely mainly on glycolytic catabolism for ATP production
-Fewer mitochondria, lower levels of myoglobin, less extensive blood supply; “white muscle”
motor units
a single motor neuron and all fibers it innervates , signals for movement
recruitment
- initiation of contraction activates a small number of motor units as greater force is needed more motor units are activated
muscle tone
-when a muscle is at rest still has a degree of tension due to background level of motor unit activity, ready to respond to movement
hypotonia
low muscle tone
hypertonia
abnormally high muscle tone
isotonic
causes muscle to change in length
concentric
muscle tension exceed resistance , muscle able to shorten
eccentric
to lengthen
isometric
-muscle stays the same length but still create peak tension
physical training
repeated use and how it changes the structure
endurance training
looking at more repetition, long lasting performance (mitochondria), only works with oxygen type 1 fibers
resistance training
fewer repetition, working without oxygen, have to have enough glucose, type 2 fibers
disuse
decreased myofibrils, decreased muscle diameter, use it or lose it, can developed atrophy if not used
muscle fatigue
-no energy to do more
Depletion of key metabolites (CP, glycogen, glucose)
-Decreased availability of oxygen
-Environmental conditions
similarities between smooth vs skeletal
need calcium, action and myosin
differences between smooth vs skeletal
-no striations, arranged in unique way and make own crossbridge , -involuntary, no sarcoplasmic reticulum, no t tubules
simialrites between cardiac vs skeletal
striations, sarcomeres, calcium actin myosin arranged the same, t tubules, sarcoplasmic reticulum
differences between cardiac vs. skeletal
involuntary, short cells, one nucleus, intercalated discs, autorhythmic
