Lesson 1: Skeletal Muscle Flashcards
_____ and _____ which lie parallel to muscle fibers provide blood supply.
Arteries; veins
What is the benefit of having a diffuse, widespread network of blood supply to/from muscle?
Allows for increased oxygen supply/CO2 removal during rhythmic contractions
During prolonged high-force contractions, blood flow is ______ and aerobic/anaerobic energy systems provide fuel (ATP)
occluded; anaerobic
Capillary density increase with ________ training
chronic endurance/aerobic
Capillary density
Increased amount of capillaries per muscle fiber
Angiogenesis
Formation of new blood vessels
Benefits of angiogenesis
Allows for more efficient delivery of O2 and removal of CO2
Provides more prolonged capacity for aerobic ATP re-synthesis
Intramuscular PCr will increase with _________ training
chronic strength
Benefits of chronic strength training
Allows for improvements in anaerobic ATP re-synthesis during high force contractions when blood supply is limited
Sarcolemma
Thin, elastic membrane that encloses the fiber’s cellular contents
Plasmalemma
Muscle cell membrane that fuses with tendon and conducts action potential
Satellite cells
Precursor to skeletal muscle cells (stem cells)
What is the purpose of satellite cells?
Muscle growth/development, response to injury, immobilization, training
Sarcoplasm
Cytoplasm of the muscle cell
Unique features of sarcoplasm:
Glycogen storage, myoglobin, carries and stores oxygen for muscle cells specifically
Transverse tubules
Extensions of plasmalemma which carry action potential deep into muscle fiber
Sarcoplasmic reticulum (SR)
Area of calcium (CA2+) storage
SR stores _____
calcium
Transverse tubule carries _____ ____
electrical signal
A person who trains aerobically would have more/less mitochondria
More
How does a muscle fiber grow?
More myofibrils
Basic contractile element of skeletal muscle
Sarcomere
The full myofibril length is the length of the _____
sarcomere
Dark stripes of a sarcomere
A-bands
Light stripes of a sarcomere
I-band
Middle of the A-band
H-zone
Middle of the H-zone
M-band
Common boundary structure between the ends of the sarcomere
Z-line
Actin is thin/thick
thin
Myosin is thin/thick
thick
I-band contains only actin/myosin filaments
Actin
A-band contains actin/myosin filaments
actin & myosin
H-zone contains only actin/myosin filaments
myosin
Actin is made up of _ proteins
3
Proteins that make up actin:
Actin, tropomyosin, troponin
The ___ protein of actin contains myosin-binding site
actin
The _____ protein of actin covers the active site at rest
tropomyosin
The ____ protein of actin is anchored to the actin and moves the tropomyosin
Troponin
Actin is anchored at the _______
Z-disk
Myosin is made up of the protein ____
myosin
Myosin is essentially two intertwined filaments with _____ _____
globular heads
The globular heads protrude ____ degrees from the thick filament axis
360
The _______ of myosin interact with actin filaments for contraction
globular heads
When the globular heads of myosin attach to actin, they form a ______
cross-bridge
Myosin and actin will attach and shorten the sarcomere for a ______ ______
muscle contraction
Tell me about the relaxed state of the sarcomere in the sliding filament theory
No actin-myosin interaction (not attached)
Actin and myosin overlap a little (troponin covers myosin binding site)
Tell me about the contraction state of the sarcomere in the sliding filament theory
Myosin head attaches to binding site
Myosin head pulls actin toward sarcomere center (power stroke)
Filaments slide past each other
Sarcomeres, myofibrils, muscle fiber ALL shorten
What happens after the power stroke?
Myosin detaches from active site and rotates back to OG position. The myosin then attaches to another active site farther down.
Sarcomere contraction continues until the _____ reaches myosin filaments OR the _____ stops and calcium gets pumped back into the SR
Z-disk; action potential
What is the role of ATP in muscle contraction?
ATP binds to the myosin head. The ATPase on the myosin head initiates the reaction ATP –> ADP + P + energy, which allows for the power stroke of the myosin head through the release of the high energy phosphate (P)
Is ATP necessary for muscle contraction?
Yes
Without ___ and ___, there would be no movement during a muscle contraction
Calcium; ATP (nervous control, too)
Beyond the mechanical action described in the sliding filament theory, ______ must occur involving the nervous system
Excitation
Alpha-motor neuron innervate ____ ____ and are directly responsible for ______
muscle fibers; excitation
What makes up a motor unit?
Single a-Motor neurons + all fibers it innervates
The more operating motor units, the more/less contractile the force.
More
The site of communication between a neuron and muscle is the _____
neuromuscular junction
What is the neuromuscular junction made of?
A synapse between a a-Motor neurons and muscle fiber
6 steps of Excitation-Contraction Coupling:
1.) AP starts in brain
2.) AP arrives at axon terminal, released ACh
3.) ACh crosses synpase and binds to ACh receptors on plasmalemma
4.) AP travels down the plasmalemma and deeper into muscle through T-tubules
5.) Triggers calcium release from SR
6.) Calcium binds to troponin, which moves the tropomyosin, allowing myosin to bind to actin and contract.
In short, what role does the nervous system have in muscle contraction?
Triggers the release of calcium !
What about the steps of the excitation-contraction coupling in muscle relaxation?
1.) AP ends, so electrical stimulation of SR stops
2.) Calcium is pumped back into SR, where it is stored until the next AP arrives
3.) Without calcium, troponin and tropomyosin return to resting conformation, which covers the myosin-binding site and prevents actin-myosin cross-bridging
Three types of muscles:
Smooth, skeletal, cardiac
Which type of muscle is involuntary and is found in hollow organs
Smooth
Which type of muscle is involuntary and found in the heart
Cardiac
Which type of muscle is voluntary and found near the skeleton
Skeletal
A tendon connects _____ to _____
muscle; bone
Epimysium
Sheath of fibrous CT surrounding the entire muscle
Perimysium
Layer of CT surrounding a bundle of up to 150 fasciculi
Fasciculi
Bundle of muscle fibers
Endomysium
A fine layer of CT wrapping each muscle fiber
Muscle cell
Cylindrical, multinucleated fiber that makes up skeletal muscle
Muscle structures from largest to smallest:
Muscle
Epimysium
Perimysium
Fasciculi
Endomysium
Muscle fiber
Myofibrils
