Ch 9 Part 3) Muscles

Question 1

Energy for Contraction

Answer 1

• ATP supplies the energy needed fot muscle fiber too
  
  • Move and detach cross bridge
  • Pump calcium back into SR
  • and Pump Na+ and K+ in and out of cell
• ATP in muscles is depleted in 4-6 seconds
  
  • Because of this it must be regenerated via one of three mechanisims.

Question 2

Creatine Phosphate (CP)

Answer 2

• Creatine Phosphate (CP) is a high energy molecule used to donate a phospate to ADP to make ATP
  
  • Creatine Phosphate + ADP → ATP
  • Done so by enzyme creatine kinase
• Creatine creates enough ATP to power muscles for about 15 seconds

Question 3

Anerobic Pathway (Glycolosis and Lactic Acid)

Answer 3

• ATP can also be generated by breaking doww and using glucose as energy
• Glycolysis) first step in glucose breakdown
  
  • Does not require oxygen (anerobic)
  • Glucose is broken down into 2 pyruvic acid molecules
  • 2 ATP’s made per glucose (2 total)
• When in work, mucles can not get any oxygen to start conversion of pyruvic acid.
  
  • Pyruvic acid is made into Lactic Acid if no Oxygen is present
• Latic Acid
  
  • Diffuses into bloodstream where it is made back into pyruvic acid/ glucose in the liver.
• Anerobic Respiration only yealds about 5% of the ATP that Aerobic Respriation provides, but it is about 2 1/2 times faster
• With CP and ATP stores, muscle activity can continue for about 20 seconds.

Question 4

Aerobic Respriation

Answer 4

• Produces 95% of ATP during rest or during moderate excercise
  
  • must have O2 present
  • Consists of a series of chemical reactions that occur in the midocondria
• Glucose (C6H12O6) is broken into CO2 and H2O plus a large ammount of ATP (32 total)
  
  • C6H12O6→ CO2 + H2O + 32ATP
• Fuel for Aerobic Respriation
  
  • First Glycogen stored in Mucscles
  • Second Bloodbourne Glucose
  • Lastly Free Fatty acids will be burned
    
    • Main fuel after 30 mins of excercise.

Question 5

Which Pathway predominated during excercise?

Answer 5

• If the muscle has O2, Aerobic Respriation is used to create ATP. When the excercise demands exceede the capicity of Aerobic excercise we will switch to Anerobic pathways to generate ATP
• Aerobic Endurance) Length of time muscle contracts using aerobic pathways
• Anerobic Threshold) Point at which metabolism changes to anerobic pathway.

Question 6

Muscle Fatuige

Answer 6

• Defined as the physilogical inability to contract despite continued stimulation
• Possibe Causes of muscle fatuige include
  
  • Ionic Imbalances) K+, Na+, Ca2+ levels can be disturbed after continuious contraction
  • Increased Inorganic Phosphate levels may intefere with calcium release
  • Decreased Glycgoen levels
• Muscles almost never run out of ATP.

Question 7

Excess Postexcercise Oxygen Consumption (EPOC)

Answer 7

• For a muscle to return to its pre-excercise state:
  
  • Oxygen reserves in myoglobin are replenished
  • Lactic acid is reconverted to pyruvic acid
  • Glycogen stores are replenished
  • ATP and Creatine Phosphate (CP) reserves are restored
• These steps to restore the body need extra oxygen so this process is refered to as Excess Postexcercise Oxygen Consumption (EPOC)

Question 8

Force of Contraction

Answer 8

• Depends on number of cross bridges formed
• Affected by four factors
  
  1. Number of muscle fibers stimulated (recruitment)
     
     • more fibers = more force
  2. Relative size of Fibers
     
     • Bulkier Fibers = more tenstion it can hold
  3. Frequcney of Stimulation
     
     • higher= more force
  4. Degree of Muscle Stretch
     
     • Sarcomeres are at optimal strength at 80-120% length
     • any more or less and not all myosin heads form crossbridges.

Question 9

Velocity and Duration of Contractions

Answer 9

• How fast a muscle contracts and how long are influenced by
  
  • Muscle Fiber Type
  • Load
  • and Recritument

Question 10

Muscle Fiber Type

Answer 10

• Classified according to two charcteristice
  
  • Speed of Contraction (Slow or Fast)
    
    • How fast ATPases split ATP
    • pattern of eletrical acticity
  • Metabolic pathways used for ATP synthesis
    
    • Oxadative) use aerobic pathways
    • Glycolytic) use anerobic pathways.
• Sketeltal muscles can be classified into three types
  
  • Slow Oxidative Fibers) Low Intensity, Used for endurance activities
  • Fast Oxidative Fibers) Medium- intensity activities
    
    • Contract quickly but still depend on O2
  • Fast Glycolytic Fibers) Short-Intense movment
    
    • No O2 used
• All fibers in one Motor unit will be the same
• Genetics Dictate individual’s precentage of each type of fiber.

Question 11

Load and Recritment

Answer 11

• Load) Muscle Contract faster when there is no load
  
  • Greater the load, shorter the duration of contaction
  • More load = slower contraction
• Recritument) More units contracting = faster and longer contraction

Question 12

Aerobic Excercise (effects)

Answer 12

• Leads to incresesed
  
  • Muscle capillaries
  • Number of mitochondria
  • Myoglobin synthesis
• Results in greater endurance, strenght and resistance to fatuige.
• Fast Glycotic Fibers may convert into Fast Oxidative Fibers

Question 13

Resistance Excercise (effects)

Answer 13

• Resistance (anerobic) excercice leads to muscle hytrophy
  
  • Increase in muscle strenght and size
  • Increased mitochondria, myofilaments, glycogen stores, and conenctive tissue

Question 14

Atrophy

Answer 14

• Muscles must be used to remain healthy
• Atrophy is the loss of muscle mass due to unuse
  
  • Can be imobilized or have no stimulation
  • Begins almost immediately

Question 15

Regeneration of Muscle

Answer 15

• Skeletal Muscle) limited regenerative capicity
• Cardiac Mucle (cardiomyocytes) devide at a modest rate
  
  • Injuries to heart are generally replaced with CT
• Smooth Muscle) regenrated through life
• Aging muscles = Loss of muscle mass (sarcopenia)
  
  • Begins at age 30

Question 16

Develpoment

Answer 16

• Muscles develop head to toe
  
  • A baby can lift its head before it can wals.