Chapter 6 Pt. 2 Flashcards
A muscle contracts when the _____ ________ slide along the myosin filaments, increasing the degree of overlap between actin and myosin and thus shortening the sarcomere
actin filaments
A muscle contracts when the actin filaments slide along the ________ _________, increasing the degree of overlap between actin and myosin and thus shortening the sarcomere
myosin filaments
A muscle contracts when the actin filaments slide along the myosin filaments, increasing the degree of overlap between _____ and ______ and thus shortening the sarcomere
actin
myosin
A muscle contracts when the actin filaments slide along the myosin filaments, increasing the degree of overlap between actin and myosin and thus shortening the __________
sarcomere
When many __________ shorten, the muscle as a whole contracts
sarcomeres
When many sarcomeres shorten, the muscle as a whole ________
contracts
The club-shaped _______ ______ are the key to the movement of actin filaments and, therefore, to muscle contraction
myosin heads
What are the steps of the sliding filament model? 1) 2) 3) 4) 5)
1) resting sarcomere
2) Cross-bridge attachment
3) Bending of myosin head (the power stroke)
4) Cross-bridge detachment
5) Myosin reactivation
At the start of each cycle, the myosin heads have already split a molecule of ATP to _____ and _________ _________ (___)
ADP
inorganic phosphate
(Pi)
What happens during Cross-bridge attachment?
myosin head binds to an actin filament and acts as a bridge between the thick and thin filaments
What happens during the Bending of myosin head (the power stroke) ?
the ADP and inorganic phosphate are released from the myosin head
What happens during the Cross-bridge detachment?
the new ATP molecules now bind to the myosin heads, causing the myosin heads to disengage form the actin
What happens during the Myosin reactivation?
the myosin heads split the ATP into ADP and Pi and store the energy, causing the contraction cycle to begin again
Muscle cells contain the proteins ________ and _________, which together form a troponin-tropomyosin complex
troponin
troponyosin
Muscle cells contain the proteins troponin and troponyosin, which together form a _______-_________ _______
troponin-tropomyosin complex
What is sarcoplasmic reticulum?
an elaborate form of smooth endoplasmic reticulum found in muscle cells
________ ions are stored inside sarcoplasmic reticulum
Calcium
What are transverse tubules (T tubules)?
tiny, cylindrical pockets in the muscle cells plasma membrane
transverse tubules (T tubules) carry signals from motor neurons deep into the muscle cell to virtually every _________
sarcomere
What is Rigor Mortis?
when muscles become stuff within a few hours after death
Why do muscles become stuff within a few hours after death?
calcium ions begin to leak out of the sarcoplasmic reticulum, initiating muscles contract
The muscles relax after __ to __ days after death
2 to 3
What is neuromuscular junction?
the junction between the tip of a motor neuron and a skeletal muscle cell
A muscle contraction is the result of these key steps:
1)
2) acetylcholine is released at the neuromuscular junction
3) when acetylcholine binds to receptors on the plasma membrane of the muscle cell, an electrochemical message is generated
4) the electrochemical message spreads through T tubules, causing the release of calcium ions form the sarcoplasmic reticulum
1) a nerve impulse reaches the neuromuscular junction
A muscle contraction is the result of these key steps:
1) a nerve impulse reaches the neuromuscular junction
2)
3) when acetylcholine binds to receptors on the plasma membrane of the muscle cell, an electrochemical message is generated
4) the electrochemical message spreads through T tubules, causing the release of calcium ions form the sarcoplasmic reticulum
2) acetylcholine is released at the neuromuscular junction
A muscle contraction is the result of these key steps:
1) a nerve impulse reaches the neuromuscular junction
2) acetylcholine is released at the neuromuscular junction
3)
4) the electrochemical message spreads through T tubules, causing the release of calcium ions form the sarcoplasmic reticulum
3) when acetylcholine binds to receptors on the plasma membrane of the muscle cell, an electrochemical message is generated
A muscle contraction is the result of these key steps:
1) a nerve impulse reaches the neuromuscular junction
2) acetylcholine is released at the neuromuscular junction
3) when acetylcholine binds to receptors on the plasma membrane of the muscle cell, an electrochemical message is generated
4)
4) the electrochemical message spreads through T tubules, causing the release of calcium ions form the sarcoplasmic reticulum
The contraction of ______ muscles then stretches the sarcomere back to its original length
other
What are muscle cramps(or spasms)?
forceful, involuntary muscle contraction
What are the possible causes of muscle cramps?
calcium, magnesium, or potassium
What happens if too many calcium ions enter the cell?
those ions can destroy proteins within the cell, causing it to die
What is muscular dystrophy?
a general term for a group of inherited conditions
What is Ducheme Muscular Dystrophy?
caused by a defective gene for production of the protein dystrophin
What is one of the most common forms of muscular dystrophy?
Ducheme Muscular Dystrophy
Ducheme Muscular Dystrophy:
dead muscle cells are replaced by ____ and _________ _______, so the skeletal muscles become progressively ________
fat
connective tissue
weaker
What are the 2 important ways to vary the contraction of whole muscles?
1) changing the number of muscle cells contracting at a given moment
2) changing the force of contraction in individual muscle cells by altering the frequency of stimulation
What is motor unit?
a motor neuron and all the muscle cells it stimulates
What is recruitment?
the process by which the nervous system increases the strength of a muscle contraction by increasing the number of motor units being stimulated
True or False: When a muscle is relaxed, all of its motor units are relaxed
False; Even when a muscle is relaxed, some of its motor units are active
What is the result of, “a muscle is relaxed, some of its motor units are active”?
the muscle is usually firm and solid, even when it’s not being used
