PHYSIOLOGY EXAM 2 WITH 100% CORRECT QUESTIONS AND ANSWERS.

PHYSIOLOGY EXAM 2 WITH 100%
CORRECT QUESTIONS AND ANSWERS.

Organization of Skeletal Muscle - CORRECT ANSWERS.✔️✔S️ keletal Muscle consists of many bundles of
muscle cells

A muscle cell consists of many myofibrils

A bundle of muscle cells is called a fascicle

In a fascicle, there are sarcomeres, the contractile unit of skeletal muscle



Cardiac Muscle Tissue - CORRECT ANSWERS.✔️✔️Involuntary, only in heart, pumps blood



Smooth Muscle Tissue: - CORRECT ANSWERS.✔️✔️Involuntary, walls of hollow organs and small
arteries



Skeletal Muscle Tissue: - CORRECT ANSWERS.✔️✔️Voluntary, directly/indirectly attached to bones,
contraction and relaxation movements



Sarcomeres and Striations - CORRECT ANSWERS.✔️✔️lines, I band, A band, M line, and H band



Sliding Filament Theory - CORRECT ANSWERS.✔️✔️When muscles contract, thin filaments slide over
thick filaments

H and I bands get smaller

zones of overlap get larger

Z lines move closer together, but A bandwidth is unchanged

Sliding occurs in all sarcomeres in each myofibril

As myofibrils shorten, so does the muscle fiber (contraction)



Step 1 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Resting sarcomere: Myosin heads
are all "energized" and "cocked", Cocking head requires breakdown of ATP

,Myosin head acts as ATPase

ADP and P stay attached to head



Step 2 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Contraction cycle begins, Calcium
ions arrive from SR



Step 3 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Active sites exposed, Calcium
binds to troponin, Troponin changes position, moves tropomyosin and exposes active sites on actin



Step 4 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Cross-bridges form Myosin heads
bind to exposed active sites on actin Forms cross-bridges



Step 5 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Myosin heads pivot, Cross-bridge
formation causes myosin heads to pivot toward M line (center sarcomere), power stroke, ADP and P
release



Step 6 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Cross-bridges detach

A new ATP attaches to each myosin head

myosin releases from actin

Active site available to form another cross-bridge



Step 7 of a muscle fiber contraction cycle - CORRECT ANSWERS.✔️✔️Myosin reactivates

Free myosin head splits ATP into ADP and phosphate

Released energy used to "recock" myosin head



Crossbridge cycling: - CORRECT ANSWERS.✔️✔️multiple repititions of attach, pull, release, and reset to
fully contracted sarcomere



Sarcomere shortening: - CORRECT ANSWERS.✔️✔️What happens when a relaxed muscle becomes a
contracted muscle

,Relaxed Muscle: - CORRECT ANSWERS.✔️✔Z️ disc, thin filament, thick filament, m-line, thin filament, Z
disc; in between two thin filaments is called H zone



Contracted Muscle: - CORRECT ANSWERS.✔️✔️Z disc, M line, z disc (entire thing called A band)



Motor Unit: - CORRECT ANSWERS.✔️✔️made up of a motor neuron and the skeletal muscle fibers
innervated by that motor neuron's axonal terminals

Groups of motor units often work together to coordinate the contractions of a single muscle

all of the motor units within a muscle are considered a motor pool



Excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️link between generation of action potential
in sarcolemma and start of muscle contraction



Step 1 in excitation-contraction coupling - CORRECT ANSWERS.✔️✔️Neural Control



Step 2 in excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️Excitation



Step 3 in excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️Calcium lon Release,



Step 4 in excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️Contraction cycle begins,



Step 5 in excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️Sarcomeres shorten,



Step 6 in excitation-contraction coupling: - CORRECT ANSWERS.✔️✔️Muscle tension produced



Muscle Tension: - CORRECT ANSWERS.✔️✔️Force generated when a muscle is stimulated to contract;
muscle fiber either "on" (producing tension) or "off" (relaxed)



Peak Tension: - CORRECT ANSWERS.✔️✔️Four levels: Treppe, Wave summation, Incomplete tetanus,
complete tetanus

, Treppe: - CORRECT ANSWERS.✔️✔S️ timulation of muscle fiber immediately after relaxation phase
produces maximum tension



Wave Summation: - CORRECT ANSWERS.✔️✔️Adding of one twitch to another

stimulation of muscle fiber before relaxation phase ends produces increasing maximum tension

duration of twitch determines maximum time available to produce wave summation



Incomplete Tetanus: - CORRECT ANSWERS.✔️✔️Rapid Cycle of contraction/relaxation producing near
peak tension



Complete tetanus: - CORRECT ANSWERS.✔️✔️Higher stimulation eliminates relaxation phase

no calcium ions returns to sarcoplasmic reticulum

results in peak tension and continuous contraction



Fatigue (muscles) - CORRECT ANSWERS.✔️✔️Muscle can no longer perform at required level; major
factor is decreased pH; decreases calcium and troponin binding



Motor Unit Recruitment: - CORRECT ANSWERS.✔️✔️number of stimulated muscle fibers affects muscle
tension

activation of motor units to produce more tension

smaller units activated first

smooth steady increase in muscle tension



The Cori cycle: - CORRECT ANSWERS.✔️✔D
️ uring recovery period, Lactate diffuses out of muscle into
blood

Liver coverts lactate to pyruvate

ATP then used to convert remaining pyruvate to glucose

Glucose returns to muscle cells to rebuild glycogen reserves