Lab 6 Muscles

Supermacmaxial stimulus

1.5 x

Inhibit cross-bridge cycling

Build of ADP inorganic phosphate as ATP are consumed may directly inhibit cross-bridge cycling, thus delaying cross bridge detachment

Why do we wet the muscle? With what?

Frog ringer because the muscle is still alive.

Motor Neuron Action Potential

Potassium efflux and sodium influx allow membrane potential to approach 0 --> EPP always results in action potential in the muscle fiber

End plate potential happens by?

Potassium efflux and sodium influx allow membrane potential to approach 0 because muscle is normally at -90, So therefore causes depolarization.

Why do we calibrate?

Raw output from the force transducer is in millivolts. It needs to be calibrated to give the more meaningful units of Newtons (N). Force transducers also often have some residual offset voltage. When you make any measurement using a Marker, you can remove the residual offset voltage.

Where does the femur go?

Tighten the thumbscrew until the femur is set firmly in the clamp (you should not be able to move the bone at the knee joint). The tubing collar serves two purposes; it will prevent the bone from being crushed, and insulate any muscle tissue from reacting with the metal clamp.

Imagine in single twitch Ca saturate tropinin and now a lot of mysoin binding sites are available

chross bridge takes time so Ca2+ Begins to get pumped out, thus tropipin and tropain cause blocks of mysosin binding sites before cross bridging (actin and myosin) can occur

Acid Build UP

lactic acid build up during anaerobic respiration may alter number of muscle protein, not only actin and moysin but also proteins involved in calcium release

Complete tetanus

muscle is at maximal sustained contraction

Tension and force a muscle can generate is directly proportional to?

number of cross bridges of thick and thin filaments

When circumver too short

thick and thin have too much overlap before the contraction begins Thick myosin can move the think actin a very short distance before thin actin filaments from each circumver begin to overlap

Incomplete tetanus

translante relaxation allowed between each stimulus

In light of the "all or none" law of muscle contraction, how can you explain the graded response?

when stimulus amplitude keeps on increasing after reaching threshold, multiple muscle fibers are activated. THIS causes contractile forced to be summed and displayed in graded potential

supramaximal stimulus

supramaximal stimulus, enter this voltage in the Supramaximal Excitation table. The voltage that you enter is multiplied by 1.5 to obtain the supramaximal excitation voltage, shown in the second column.

How do graded action potentials occur?

-Recruitment -Stretch -Summation

Question 1:

A,B,E,C,D,F,G

Look at KuraCloud

And study

Tetanus

Average state staying constant

During tetanus continuous _______________ is released to saturate _________________________ all the time

Ca2+ and Tropinin Thus myosin can bind actin causing more force generation '

What can higher amplitude stimuli do?

Can recruit more motor units to achieve strong contractile forces, these may also be greater size which enhance the recruitment.. ONE WAY to increase muscle tension in a graded manner

Acetylcholine receptors are__________

Cation ion receptors allowing Sodium and Potassium to path through

What happens then to acetycholine?

Diffuses from muscle terminal to end plate THEN binds to ionic tropic acetylcholine receptors

Myosin thick filaments

Drive the movement of actin thin filaments

Continuous tetanus results in:

Fatigue

Any muscle contraction AP causes?

Intracellular release of calcium to bind tropinin so that myosin binding sites are exposed for cross bridge formation

What does the force transducer do?

Measure the force when stimulus is applied.

How do we calibrate?

Now balance a 5-gram weight on top of the pin of the force transducer (as shown in the diagram. Make sure the weight is only touching the pin!) and record for another 625 ms.

What happens when AP goes down motor unit

Open voltage gated Ca2+ Then binds with Acetylcholine vesicle and releases

Single twitch does not?

Represent the maximum force a muscle fiber can produce

Twitch

Single contraction and relaxation HAPPENs with one motor unit with one stimulus

Motor Unit

Single motor unit and all the muscle fibers innervates or connects to

Single muscle twitch is defined as: CAUSED BY EPP

Single relaxation and contraction of muscle Vary In: -Height curve -Duration -Slope -Thus in Speed and force of contraction AP can be couple millseconds but muscle contraction can be 100 milliseconds or more

When circumver too long

Sliding filaments interact minimally and cannot generate much force

'Maximum Excitation Voltage'

The stimulus voltage at which the response no longer increases

As rate stimulus increases

so does tension

Sliding Filament Theory

actin and myosin interact and slide past each other during contraction because of continuous formation and breaking of cross bridges

Conduction Failure

action potential continuous firing causing extracellular K to increase in the smaller t-tuble from repeated depolarization upsetting the ionic balance LEADING to failure of action potential conduction

Summation

as frequency increases

Optimal Length

intermediate; allowing numerous cross bridges to form allowing the highest amount of contraction

Where is the hook placed?

just blew the achillies tendon

What happens when you apply multiple stimuli in a short duration especially when the previous ones have not completely subsided?

see an increase in contractile force--> SUMMATION