Muscles Flashcards
What are the functions of muscles mentioned in class?
Generating heat= thermogenesis
Movement
Balance
Stopping movement (sphincters= a ring constricting muscle that relaxes to open body cavities)
What is a sphincter muscle?
A ring constricting muscle that relaxes to open body cavities. Located on both sides of the stomach, bladder, anus
What is a myofibril and what is its relationship to a muscle fiber? To a sarcomere?
Muscle fibers are made up of myofibrils, and myofibrils are made up of sarcomeres.
What is a fascicles and what is its relationship to a muscle? To muscle fibers?
Muscles are made up of fascicles, and fascicles are made up of muscle fibers.
What is the individual unit that contracts in a muscle in a sarcomere?
The actin?
What is the sarcolemma?
The plasma membrane around muscle fiber
What are t-tubules?
The transverse invaginations of sarcolemma.
What is the sacroplasmic reticulum?
looks like smooth ER, but function is to store Ca2+
- -SR surrounds myofibrils
- -meets w/T-tubules
What is sarcoplasm?
Like cytoplasm but in the muscle?
What are the thick and thin filaments made from?
Thick= myosin Thin= actin
How do troponin and tropmyosin fit in with the think and thin filaments?
The tropnin and the tropomyosin slide off the actin binding sites
What is the role of ACh (acetylcholine) and AChE (acetylcholine esterase) in contraction of a sarcomere?
- ACh binds to receptors on muscle fiber
- binding starts action potential along sarcolemma
- Acetylcholine esterase (AChE) destroys ACh
What is the role of t-tubules in contraction of a sarcomere?
action potential runs to T-tubules, causes SR to release Ca2+
What is the role of the SR in sarcomere contraction?
The SR releases calcium.
What is the role of Ca2+ in sarcomere contraction?
Ca binds to troponin,
–causing shape change
that slides troponin/ tropomyosin strand along actin (thin f.)
How do troponin, tropomyosin, actin, and myosin interact in sarcomere contraction?
When the troponin/tropomyosin reacts with the Ca2+, then it slides off the myosin binding sites on the actin, the sites then bind with the swivel heads on the myosin creating a contraction.
What is the role of ATP in sarcomere contraction?
-myosin grabs ATP and detaches from actin
• ATP hydrolyzes to ADP & P, re-cocking myosin for next
crossbridge
What is a myosin binding site and where do you find it? And what is its purpose?
A myosin binding site is like a little ridge covered in troponin on the actin. When the troponin is removed, the myosin binding sites bond to the myosin making the heads in the myosin swivel until they are inside the sites. Then a contraction is created.
What is happening to a muscle when it atrophies? When it hypertorphies?
-increase in muscle size, HYPERTROPHY, is increase in fiber diameter. Caused by packing in more myofibrils, mitochondria, SR, etc.
• same parts can disappear = ATROPHY
What molecule makes red meat red and what is the job of that molecule?
High amounts of myoglobin/oxygen
What do muscles store to use as energy?
Glycogen, oxygen, and phosphate?
What are the origin and insertion of muscles?
Origin – “anchor point” for muscle
Insertion – what the muscle moves
What is a motor unit?
A motor unit is motor neurons that are densely branched, which enables on such axon to connect to many muscle fibers.
What is a twitch?
The contractile response of a single muscle fiber to a single impulse
