Muscles 2 Flashcards
Threshold
Minimal voltage necessary to produce muscle contraction
Latent period
During and immediately after action potential when no visible change occurs in the muscle fiber (3-10 msec.)
Twitch
When muscle is given a single, brief stimulation, it shows a twitch which is a cycle of contraction and relaxation
Contraction phase followed by relaxation phase
All-or-none law
Muscle fiber exhibits a max contraction response or it exhibits none at all
Motor unit
Motor neuron + all the fibers it innervates
How is the strength of contraction of a whole muscle graded?
It differs as more motor units join in
Treppe
(Staircase phenomenon) Muscle exhibit in response to a series of stimuli of the same strength.
What is Treppe probably due to?
The inability of the muscle cells to fully return calcium to the sarcoplasmic reticulum
Example of something that exhibits Treppe
Successive increase in amplitude of the first few contractions of cardiac muscle that’s received a # of stimuli of the same intensity following a quiescent period
Refractory period
After a twitch, this is a brieft (1-2 msec.) period needed to restore the resting potential.
What happens during the refractory period
The sarcolemma is repolarizing and won’t respond to new stimulus
What happens if second stimulus arrived before the complete relaxation of a muscle
The muscle will achieve temporal summation (wave summation) and achieve a higher level of tension
what happens during temporal summation
The muscle will achieve a higher level of tension
When will temporal summation (wave summation) occur
If a second stimulation arrives before he complete relaxation of a muscle in the refractory period
Incomplete tetanus
If the stimuli are frequent enough that the muscle cannot relax completely in between
Complete tetanus
If there is no time to relax AT ALL between stimuli
Isometric contraction
Muscle contracts but does not change length (NO MOVEMENT)
Isotonic contraction
Muscle contracts with force greater/less than resistance and shortens/lengthens (MOVEMENT)
Ex: curls
Concentric contraction
Muscle contracts with force greater than resistance and shortens
Eccentric contraction
Muscle contracts with force less than resistance and lengthens
What accumulates during anaerobic fermentation when O2 is limited
Lactic acid
Phosphagen system
Phosphagen groups goes around recruiting phosphate to be ready to combine with ADP to make ATP
How do we get immediate energy
For short, quick spurts of energy we rely on the phosphagen system to supply ATP
What are the two phosphagen groups and what do they do
Myokinase and creatine kinase and they recruit phosphate groups
Short term energy
After the phosphagen system is exhausted muscle relies on fermentation (glycogen-lactic acid pathway) for ATP for 30-40 seconds
Long term energy
Aerobic respiration (cellular respiration with oxygen)
Where does lactic acid go
Back and forth between muscle and liver
What happens as glycogen is consumed
ATP synthesis declines. This shortage slows down the cells ability to maintain the resting membrane potential (NA, K pump)
What do too many potassium ions do
Reduces membrane potential, muscle fatigue
Why can’t we continue to live off of fermentation
Lactic acid lowers the pH of the sarcoplasm and impairs the action of enzymes
What happens if motor nerve fibers use up either ACh?
The CNS fatigues for unknown reasons
What does physical endurance depend on?
The max oxygen uptake of the athlete and the supply of organic nutrients (glucose)
Oxygen debt
Difference between the resting state of oxygen consumption and the elevated rate following an exercise (what you need vs what you got)
W/o enough oxygen you’re in debt
What do we use oxygen inhaled after exercise for?
Used to replace the body’s oxygen reserves, replenish the phosphagen system, oxidize lactic acid, and serve the now elevated metabolic rate
What does muscle strength depend on
Muscle size, size of active motor units, fascicles arrangement, multiple motor unit summation (recruitment), and temporal summation (wave summation)
Slow twitch fibers
Small and produce twitches up to 100 msec long. They have more mitochondria and capillaries, HIGH ENDURANCE FIBERS
Dark meat
Fast twitch fibers
Larger and produce twitches as short as 7.5 msec. Quick energy for stop/go activities. White meat
Can athletic conditioning change genetic component of ability?
No, individuals are born with different ratios of slow to fast twitch fibers
Resistance exercise (weight lifting)
Contention of muscles against a load that resists movement and is enough to stimulate muscle growth
Endurance (aerobic) exercise
Improves the fatigue-resistance of muscles. Slow twitch fibers squire a greater density of blood capillaries
Cross training
Optimal performance and skeletomuscular health require this which incorporates elements of both endurance and resistance
What is delayed muscle soreness due to
Micro trauma
Cramps
CNS occasionally triggers these painful spasmodic contractions
What are cramps initiated by
Extreme cold Heavy exercise Lack of blood flow Electrolyte depletion Dehydration Low blood glucose
Smooth muscle
Involuntary and ANS (autonomic nervous system) controls it
