Lecture 13 Flashcards
What is muscle tension?
The force exerted by a muscle/ fiber determined by number of cross bridges formed
What determines how many cross bridges are formed?
Fiber length
Fiber size
Fatigue
What does a single muscle stimulus produce?
A twitch
How long does each section of a muscle movement last?
Action potential : 1 to 2 msec
Latent period : 2 msec
Contraction : 10 - 100 msec
Relaxation : depends
Single twitch vs. Wave summation
Single : 1 AP and relaxation
Wave : 2 AP and 1 relaxation with the second AP releasing more Ca+ for more tension
What is unfused tetanus?
Multiple wave summations building off one another with partial relaxation between contractions (quivering)
What is fused tetanus?
High frequency stimulus with no relaxation
Sustained contraction (complete tetanus)
All troponin are saturated with Ca+
What state is optimal for muscles and why?
Resting fiber length
Allows for max cross bridges = max tension
Why is shortened or lengthened fiber lengths not optional?
Short - thin filaments overlap = less cross bridges
Long - not all myosin heads interact with actin filaments
What does fiber size matter?
Thicker fibers mean more myofibrils which means more tension
What encourages muscle fiber growth?
Fibers thicken in response to exercise and testosterone
What effect does fatigue have on muscles?
Less contraction = reduced max muscle tension
Result in micro tears from strenuous exercise
What are the two types of muscle fibers?
Fast - contract ad relax rapidly ( white with low myoglobin)
Slow - contract and relax slow ( red with high myoglobin)
What type of muscle fiber would be used for marathons?
Slow muscle fibers because the myoglobin in it beings in more respiratory ATP
Is slow to work but lasts for longer time using respiratory ATP
What is the tension of whole muscles affected by?
Number of fibers contracting ( more motor units = greater tension)
Number of fibers per motor unit (100 fibers vs 100 fibers/ neurons)
Size of muscle (large muscle = more fibers = more tension)
Fatigue
How is muscle tone maintained?
By alternatively stimulating different motor units at low levels
What is the purpose of muscle tone?
Firmness to muscles
Isotonic vs. Isometric
Isotonic - muscle length changes and tension exceeds resistance is load (the lift)
Isometric - the muscle length is unchanged and tension does not exceed the resistance of the load (the hold)
Which whole muscle contraction requires ATP?
Both isometric and isotonic
What are the 3 ATP systems?
Creatine phosphate
Glyocolysis
Aerobic respiration
How is energy used during resting?
Using fatty acids through aerobic respiration
When is creatine phosphate produced?
During resting an excessive amount CrP ATP is created and stored
What is the duration of energy in a CrP unit?
15 seconds
What is the stored version of glucose?
Glycogen
Is ATP required to convert Glucose to its resting state?
Yes because it is an anabolic process
What is the order of ATP system used?
Free ATP - < 15 sec
Pcr - atp from creatine - < 15 sec
Glycolysis anaerobic - < 1 min
Aerobic respiration - 1 < + hrs
Where does aerobic respiration retrieve energy from?
Glucose from the liver and then fatty acids
Fatty acids take longer to convert to usable energy
What colour reflects the amount of myoglobin in muscles?
White = none to little
Pink = medium
Red = lots
Why do muscles show fatigue?
Due to the depletion of glycogen
Build up of end products (lactic acid reduces O2 delivery) / (Pi binds to Ca+ and slows cross bridges)
Failed AP (more K+ in tubules and stops Ca+ release)
CNS fails to command muscles effectively from lactic acid
What occurs after long term muscle fatigue?
Neurons run out of Ach even in healthy people
What is oxygen dept?
The recovery of oxygen consumption
What is oxygen used for?
Replenish glycogen, creatine, phosphate, O2 on hemo and myoglobin
Convert lactic acid to Krebs cycle and liver as glucose
Why does the body temp increase in exercise?
To increase O2 demand
Increases rate of chemical reactions means more ATP and more O2 in ETC to make ATP
Spasm vs. Cramp
Sudden involuntary contraction of single muscle
Painful and involuntary contraction of muscle
Why do cramps occur?
Inadequate blood flow to muscle
Prolonged position
Dehydration
Overuse of muscle
Electrolyte decrease
Injury
