Exam 1 exercise physiology unl

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4 factors that affect force production in a muscle


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4 factors that affect force production in a muscle

  1. of activated motor units

  2. size of motor units 3)# of fibers in activated motor units 4)relation between stimulation and inhibition in force production

Most common inhibitor

Gamma amino butyric acid (GABA)

Most common stimulant

Acetylcholine (ACH)

Stimulus threshold

Amount of stimulant needed in order to cause an action potential ( all or nothing )

How can you increase force production in a motor unit

By increasing the frequency of stimulation

What is tetanus

The plateau of stimulation of a muscle fiber when a motor unit is stimulated frequently

Task dependency model of fatigue

The cause of fatigue depends on the activity you are doing

Increase in motor unit recruitment and stimulation frequency will

increase force

relationship between recruitment and firing rate is concurrent until

80-90% of max force

after 80-90% of max force what happens

Firing rate increases

in order to avoid exhaustion, what percentage of motor units does the hand allow to be recruited

about 50%

Accumulation Hypothesis

Build up of metabolic byproducts cause fatigue

Examples of metabolic by products

Lactate, inorganic phosphate, ammonia

Depletion hypothesis (neuro fatigue)

The depletion of ACH at the myoneural junction causes fatigue

Depletion hypothesis (energy substrates)

The depletion of energy substrates causes fatigue

Example of energy substrates

Phosphagen, ATP, Glycogen

Under what conditions does the accumulation hypotheses cause us to fatigue

85-95% of max, maintained for 30 seconds - 3 minutes Ex: 200, 400, 800m run

Primary energy pathway in accumulation hypothesis and why

Anaerobic glycolysis Lactic acid build-up causes fatigue

Why lactate may not be the bad guy

Lactate can be used as an energy source for other cells

The dissociated hydrogen from lactic acid is what causes fatigue due to pH increasing

four ways lactate can cause fatigue

Interference with the release of calcium from the SR

Lactate build-up interferes directly with actin/myosin bonding strength

Lactic acid interferes with ATP breakdown

Lactic acid interferes with ATP production

How to effect lactic acid build up

Exercise training Increasing the buffering capacity of the cell Sodium Bicarbonate supplements

4 ways inorganic phosphate interferes with force production

interferes with actin-myosin binding affinity

interferes with calcium-troponin binding affinity

interferes with calcium release by the SR

interferes with calcium reuptake by SR

Ammonia is a byproduct of what reaction

ADP+ADP->Adenylate kinase->AMP+ATP AMP-->AMP deaminase-->Ammonia + IMP

How does ammonia build-up effect fatigue

It effects action potential propagation along the SR

At what intensity is ATP-PC system used

High-max intensity

What increases creatine phosphagen storage

Exercise training and creatine supplementation

What naturally forms creatine

Arginine glycine and thymine

Explain creatine loading phase

20 g of creatine a day for 5-7 days or 3-5 g a day for 30 days it boosts your creatine phosphate storage by about 20%

Where do we store ATP

The only place is bound to the myosin Head

This is only enough for about 3-4 seconds of exercise.

Primary ATP production pathway in a marathon

Aerobic oxidation of carbohydrates

When is the Aerobic oxidation of carbohydrates depleted

when glycogen stores run out

How long does Aerobic oxidation of carbohydrates last when running

about 20 miles

What happens when a runner "hits the wall"

Glycogen stores are depleted and they are using fats as energy

Fatigue from fats is from the accumulation theory

Glycogen supercompensation

Also known as carbo-loading

Deplete glycogen stores a week before the race Eat low or zero carbs until three days before the race then eat about 80% carbs Your body will super compensate causing glycogen stores to be nearly doubled.

3 muscle fiber types

Slow twitch Oxidative, Fast twitch glycolytic, and Fast twitch oxidative glycolytic

3 types of muscle

cardiac, smooth muscle, and skeletal muscle

what causes cardiac muscle to contract

SA Node

What NS influences heart rate

Autonomic nervous system (sympathetic and parasympathetic)

What muscle is striated

cardiac and skeletal

What muscle is not striated

smooth muscle

What NS innervates skeletal muscle

Somatic nervous system

What is the outer layer of skeletal muscle that connects to tendon


What surrounds the Fasciculus


What surrounds the muscle fibers


What is a fasciculus

it is what houses muscle fibers

What is the function of connective tissue outside of muscles

energy transfer and protection

Force of a muscle fiber is directly proportional to


cell membrane of muscle fibers is the


Cytoplasm of muscle cells