Lab 5 Flashcards
What muscle will you attempt to stimulate in order to conduct the muscle twitch experiment?
FLEXOR DIGITORUM SUPERFICIALIS
What is tetanus?
A SMOOTH SUSTAINED CONTRACTION OF MAXIMAL STRENGTH
Define motor unit! What is motor unit recruitment?
A MOTOR NEURON & ALL OF THE MUSCLE FIBERS IT INNERVATES. WHEN MORE TENSION IS
NEEDED MORE MOTOR UNITS ARE ACTIVATED.
What protein makes up thick filaments?
Myosin
What proteins make up the thin filaments? What are their functions?
ACTIN – SHAFT OF THE THIN FILAMENT. POSSESSES MYOSIN BINDING SITES SO THAT MYOSIN
CAN BIND TO IT & INITIATE THE “POWERSTROKE”
TROPONIN – REGULATORY PROTEIN THAT BINDS CALCIUM & THEN SHIFTS TROPOMYOSIN OUT
OF THE WAY SO MYOSIN CAN BIND TO ACTIN
TROPOMYOSIN – COVERS THE MYOSIN BINDING SITES ON ACTIN
Where is myosin ATPase located? What is its function?
ON THE MYOSIN HEAD. TO HYDROLYZE ATP AND RE-SET THE MYOSIN HEAD TO THE
“ENERGIZED” POSITION
Where would you find dihydropyridine receptors? What do they respond to?
MBEDDED IN THE T-TUBULE MEMBRANE. THEY are VOLTAGE SENSORS respond to muscle AP
What is the function of the ryanodine receptors/channel?
RELEASE CALCIUM IONS FROM THE SR
What is creatine kinase? What is creatine phosphate?
CREATINE KINASE IS AN ENZYME THAT CREATES CREATINE PHOSPHATE FROM CREATINE AND
ATP
What is the difference between neuromuscular fatigue & psychological fatigue?
NEUROMUSCULAR FATIGUE IS WHEN THE ACETYLCHOLINE SYNTHESIS CANNOT KEEP UP WITH
DEMAND
PSYCHOLOGICAL FATIGUE IS WHEN MOTOR NEURON ACTIVITY ITSELF HAS STOPPED
What is the difference between hypertrophy & hyperplasia?
HYPERTROPHY IS AN INCREASE IN MYOFIBER DIAMETER DUE TO AN INCREASE IN MYOSIN AND
ACTIN SYNTHESIS
HYPERPLASIA IS AN INCREASE IN THE NUMBER ON MYOFIBERS
What lines mark the end of the sarcomere?
Z LINES/DISCS
What is a sarcomere?
THE SMALLEST CONTRACTILE UNIT WITHIN A MYOFIBRIL
What is the neurotransmitter used at the neuromuscular junction?
AcH
Why is ATP needed for relaxation?
SO THE MYOSIN HEAD CAN UNBIND FROM THE ACTIN
What is the function of the sarcoplasmic reticulum?
STORE & RELEASE CALCIUM
What is the function of magnesium in cross-bridge cycling?
IT IS NEEDED FOR THE HYDROLYSIS OF ATP
What is rigor mortis?
STIFFNESS OF DEATH
What is the function of the calcium ATPase pump?
PUMP CALCIUM BACK INTO THE SR
Define latent period
THE PERIOD OF TIME BETWEEN THE GENERATION OF A MUSCLE ACTION POTENTIAL AND THE
ACTUALLY MOVEMENT/CONTRACTION OF THE MUSCLE CELL
How can muscle contractions be varied in strength?
THE NUMBER OF MUSCLE FIBERS CONTRACTING WITHIN A MUSCLE – MOTOR UNIT
RECRUITMENT
THE TENSION DEVELOPED BY EACH CONTRATING FIBER
How can tension be developed in individual fibers?
THE FREQUENCY OF STIMULATION
THE LENGTH OF THE FIBER AT THE ONSET ON CONTRACTION
THE EXTENT OF FATIGUE
THE THICKNESS OF THE FIBER
Describe twitch summation.
FREQUENCY OF STIMULATION OF THE MUSCLE. MUSCLE CELL IS STIMULATED AT A HIGH
FREQUENCY TO PREVENT A DECREASE IN INTRACELLULAR CALCIUM LEVELS
What does it mean by optimal muscle length?
SARCOMERE LENGTH IS OPTIMUM WHEN THERE IS A MAXIMUM NUMBER OF CROSS BRIDGES CAN
BE FORMED
Why is tension development less in a shortened or lengthened sarcomere?
IN A SHORTENED SARCOMERE, THERE IS A DECREASE IN CALCIUM RELEASE BY THE SR & THE
ABILITY OF CALCIUM TO BIND TO TROPONIN IS INHIBITED
IN A LENGTHED SARCOMERE, THE MAXIMUM NUMBER OF CROSS BRIDGES CAN’T BE FORMED
Define isotonic and isometric contractions
ISOTONIC CONTRACTION IS WHEN THE MUSCLE WILL CHANGE LENGTH BUT MAINTAIN A CONSTANT
TENSION
ISOMETRIC CONTRACTION IS WHEN THE MUSCLE WILL CHANGE TENSION, BUT MAINTAIN A
CONSTANT LENGTH
What is the function of myoglobin?
INCREASE OXYGEN TRANSFER BETWEEN THE BLOOD AND THE MUSCLE
What is disuse atrophy? What is denervation atrophy?
DISUSE ATROPHY IS A DECREASE IN MUSCLE MASS DUE TO INACTIVITY
DENERVATION ATROPHY IS A DECREASE IN MUSCLE MASS DUE TO A LOSS IN NERVE SUPPLY
How can the ATP synthesizing capacity of a skeletal muscle be changed?
INCREASE MITOCHONDRIAL CONTENT
INCREASE VASCULARIZATION
What could be a chemical cause of fatigue?
Lactic Acid buildup in muscles
In fatigue, what happens to force production over time?
Force falls
Stimulus Intensity vs stimulus frequency?
Intensity refers to increases in the force of a stimulus and frequency is how often the stimulus is applied
What has happened in the muscle when the maximal stimulus is achieved?
All the individual nerve fibers have been recruited.
What is the key variable in an isometric contraction?
Muscle Length
