Chapter 10 Flashcards
Why are skeletal muscles on either sides of joints?
to stabilize them
What is contractility?
shorten using energy; return to shape when relaxed
What is excitability?
electrical events can be started in skeletal muscles (called an action potential)
What does it mean that a skeletal muscle is conductive?
muscles are long, so the whole muscle can get “excited”
What is distensibility?
stretch
What is elasticity?
recoil
How do muscle fibers develop?
through fusion of myoblasts
How do myoblasts form muscle fibers?
myosatellite cells give rise to new myoblasts that fuse together to form muscle fiber
Where do nuclei sit in skeletal muscle fibers?
on the edges (peripheral); right up under plasma membrane
What causes striations in mature muscle cells?
proteins
What is one of the roles of muscle fiber nuclei?
constantly fixing proteins in cells and making proteins
What is the sarcolemma?
plasma membrane of the muscle fiber
surrounds sarcoplasm
What is the sarcolemma capable of?
changing charge
a change in transmembrane potential at the sarcolemma begins contractions
What are transverse (T) tubules?
tunnels that have inside open to ECF
filled with positive fluid, compared to negative charge inside cell
How does an action potential travel in the muscle cell?
travels down sarcolemma and down t-tubules, setting off charge change
What is the sarcoplasmic reticulum?
a membranous structure surrounding each myofibril
stores calcium necessary for muscle contraction
has end chambers (terminal cisternae) attached to t-tubules
What is a triad?
one t-tubule and 2 terminal cisternae from 2 different SR
What does an action potential allow the cisternae and SR to do?
release calcium
Where do the terminal cisternae release calcium into?
the sarcoplasm
What are myofibrils?
overlapping myofilaments
What are myofilaments responsible for?
muscle contractions
Where do thin filaments attach to?
z-disc
Where do thick filaments attach to?
m-line
What is the sarcomere?
contractile unit of muscle
What is the A-band?
always the length of the thick filament
What is the H zone?
thick filaments only
What is the I band?
thin filaments only
Where does the sarcomere run to and from?
z-disc to z-disc
What is the zone of overlap?
both myofilaments overlap
What is a fascicle?
a bundle of muscle fibers
What surrounds a fascicle?
the perimysium
What covers the skeletal muscle as a whole?
epimysium
What covers individual muscle fibers?
endomysium
What controls the skeletal muscles?
nerves of the somatic system
What is the epimysium?
external collagen layer
connected to deep fascia
separates muscle from surrounding tissues
What is the perimysium?
surrounds fascicles
contains blood vessel and nerve supply to fascicles
What is the endomysium?
surrounds individual muscle fibers
contains capillaries and nerve fibers contacting muscle cells
contains myosatellite (stem) cells that repair damage
Where do the epimysium, perimysium, and endomysium meet?
at ends of muscles to form connective tissue
What is apneurosis?
typically connects muscle to muscle (sheet like)
How is tendon attachment described?
cord-like bundle
What is the sliding filament theory?
z-discs move toward m-line, increasing overlap between thin and thick filaments
What happens to the A zone in the sliding filament theory?
the width stays the same
What happens to the Z-discs in the sliding filament theory?
they move closer together
What happens to the H zone and I bands in the sliding filament theory?
they get smaller
What happens to the zone of overlap in the sliding filament theory?
it gets bigger
What is the plasma membrane impermeable to?
charged ions like sodium and potassium
How do the ions get through the plasma membrane?
leak channels
gated channels
How is an excitable membrane described?
potassium high inside cell
sodium high outside cell
What does the electrical gradient do?
attracts ions of opposite charge
Where do positively charged ions want to be?
inside the cell
What is the charge of the cell at rest?
positive outside
negative inside
What is the electrical and concentration gradient of potassium?
electrical gradient wants to go inside cell
concentration wants to go out
What is the electrical and concentration gradient of sodium?
concentration gradient to go inside cell
electrical gradient to go inside cell
What is a neuromuscular junction?
a synapse (where a neuron and a muscle fiber connect)
What do neuron synaptic terminals contain?
vesicles containing Ach at the end of the neuron
What is Ach?
a neurotransmitter
What is a synaptic cleft?
the space between a neuron and a muscle
What is the communication at the synapse?
action potential releasing neurotransmitter to make things happen
What is the motor end plate?
contains Ach receptors
What has to happen to initiate an action potential?
it has to reach the axon terminal
What happens when the action potential reaches the axon terminal?
it opens calcium channels
What happens when calcium enters the cell?
Ach is released from the vesicles via exocytosis
What happens to Ach once released from the vesicles?
It diffuses across the synaptic cleft and binds onto Ach receptors (sodium channels)
What kind of channels are the calcium channels?
voltage gated calcium channels?
What kind of channels are the Ach receptors?
ligand-gated ion channels (sodium channels)
What happens when Ach binds onto the Ach receptors?
Ach opens the channels
Sodium moves into the cell, initiating an action potential
What happens to the sarcolemma sodium moves into the cell?
depolarizes
What is tropomyosin?
on actin filaments
prevents actin-myosin interaction
What is troponin?
Binds tropomyosin to actin
controlled by calcium
What is the sarcomere function in excitation-contraction coupling?
t-tubules encircle the sarcomere near zones of overlap
What causes thick and thin filaments to interact?
release of calcium from SR
What is a crossbridge?
where thick and thin filaments connect
What kind of channels are on terminal cisternae?
voltage-gated calcium channels
What is the 1st step of excitation-contraction coupling?
activation of myosin head by ATP hydrolysis
What is the 2nd step of excitation-contraction coupling?
myosin head binds to actin
What is titin?
spring/coil that runs from ends of thick filaments to z-discs
dumps calcium back into SR
pushes z-discs away to return muscle fiber to shape
How does a muscle fiber return to resting length?
elastic forces (titin)
opposing muscle contractions
gravity
What causes rigor mortis?
ions pumps cease to function; ran out of ATP
calcium builds up in sarcoplasm
SR leaks calcium
What is glycotic catabolism?
occurs in cytosol
anaerobic
2 ATP per glucose
What is oxidative catabolism?
occurs in mitochondria
aerobic
34 ATP per glucose
How does ADP become ATP again?
steals a phosphate from creatine phosphate in the presence of creatine kinase
How does the muscle store glucose?
as glycogen for ATP production
How does muscle generate ATP?
breaks down 6 carbon molecule into 2 three-carbon molecules (pyruvate and 2 ATP)
What happens to pyruvate during ATP generation?
it becomes lactic acid and lactic acid acid stays in the muscle fiber or is put into the blood
What happens when muscle runs out of oxygen?
It relies on glycolysis
pyruvic acid builds up and converts to lactic acid
What does tension of a single muscle fiber depend on?
the # of cross bridges
the fiber’s resting length at the time of stimulation
the frequency of stimulation
What is a twitch?
a single neural stimulation that produces a single contraction in response to a single batch of Ach binding
What is tetanus?
repeated frequency of stimulus with no relaxation
max tension
what is a type 1 muscle fiber?
slow to contract and slow to fatigue
contain myoglobin
more mitochondria, less myofibrils and contractile proteins
relies on O2 and ability to make ATP
What is a type 2 muscle fiber?
contracts very quickly, fatigues quickly
less mitochondria, more myofibrils and contractile proteins
relies on glucose
What happens when the motor unit is smaller?
the motor control is finer
What is a motor unit?
a motor neuron and the muscle fiber or fibers it controls
What is smooth motion?
increase tension by adding motor units until desired tension is reached for specific task
When is max tension achieved?
when all motor units reach tetanus
What is a hypotonic contraction?
no tension (flaccid)
What is a hypertonic contraction?
contractures (brain inhibits motor neurons)
What is an isotonic concentric contraction?
muscle shortens
What is isotonic eccentric contraction?
muscle lengthens
What is an isometric conctraction?
muscle stays the same length but changes tension
What does endurance affect?
increases # of mitochondria and their efficiency
increases blood supply to muscles
What happens when a muscle fatigues?
it relies on glycolytic metabolism
build-up of pyruvate to lactic acid
What does lactic acid do to muscle?
damages the sarcolemma and SR
calcium leaks out
causes pain and muscle cramps
moves into the blood
How does muscle recovery occur?
-needs oxygen and build up of ATP and creatine phosphate reserves
-heat moves into blood, vasodilates and releases into atmosphere
-calcium is pumped back into SR
-correction of lactic acid PH by exhaling CO2
When is epinephrine (adrenaline) released?
during times of stress from adrenal glands
What does adrenaline do?
increases duration and force of contraction for short time
How does an action potential spread in cardiac muscle tissue?
through the intercalated discs
What does cardiac muscle tissue rely on?
extracellular and intracellular calcium
relies on mitochondrial ATP production
What makes smooth muscle tissue special?
it is not worried about tension and always has an active actin site for myosin
relies exclusively on extracellular calcium for contraction
no sarcomere
