Exercise Science Ch 1-6 Flashcards
Muscle Fiber type that relaxes slowly
Type 1
Muscle Fiber type that relaxes rapidly
type 2 a and 2b
3 types of joints
Fibrous ( sutures, skull)
synovial ( elbow knee)
cartilaginous ( IV discs)
outer layer of muscle
epimysium
surrounding each fasciculus, or group of fibers
perimysium
surrounds individual muscle fibers
endomysium
sarcomere
smallest contractile unit of muscle
calcium binds with what protein during muscle contractions and leads to what
troponin, tropomyocin moving to allow actin and myosin cross-bridging
hydrolysis or power stroke
shortening of muscle ATP -> ADP +P
recharge phase of muscle contraction
ATP is
available to assist in uncoupling the myosin from the actin, and
sufficient active myosin ATPase is available for catalyzing the
breakdown of ATP.
Which bands elongate
I and H
Steps of Muscle Contraction
Initiation of ATP splitting (by myosin ATPase) causes myosin head to be in an
―energized‖ state that allows it to move into a position to be able to form a bond with
actin.
2. The release of phosphate from the ATP splitting process then causes the myosin head
to change shape and shift.
3. This pulls the actin filament in toward the center of the sarcomere and is referred to as
the power stroke; ADP is then released.
4. Once the power stroke has occurred, the myosin head detaches from the actin but
only after another ATP binds to the myosin head because the binding process
facilitates detachment.
5. The myosin head is now ready to bind to another actin (as described in step 1), and
the cycle continues as long as ATP and ATPase are present and calcium is bound to
the troponin.
the maximal amount of force the motor unit can develop.
tetanus
Type I muscle fiber
(slow-twitch)
efficient and fatigue resistant have a high capacity for aerobic energy
supply, but they have limited potential for rapid force development, as
characterized by low myosin ATPase activity and low anaerobic power
Type 2a muscle fier
(fast-twitch)
inefficient and fatigable and as having low aerobic power, rapid force
development, high myosin ATPase activity, and high anaerobic power
Type 2b muscle fiber
IIx (fast-twitch)
show less resistance to fatigue then Type IIa
How Can Athletes improve Force Production?
Incorporate phases of training that use heavier loads in order to
optimize neural recruitment.
x Increase the cross-sectional area of muscles involved in the desired
activity.
x Perform multimuscle, multijoint exercises that can be done with
more explosive actions to optimize fast-twitch muscle recruitment.
Muscle spindle
When a muscle is stretched, deformation of the muscle spindle
activates the sensory neuron, which sends an impulse to the spinal cord, where it synapses with a motor neuron, causing the muscle
to contract.
Golgi Tendon Organs (GTO)
Golgi tendon organs are proprioceptors located in tendons near the
myotendinous junction.
x They occur in series (i.e., attached end to end) with extrafusal
muscle fibers.
x When an extremely heavy load is placed on the muscle, discharge
of the GTO occurs.
x The sensory neuron of the GTO activates an inhibitory interneuron
in the spinal cord, which in turn synapses with and inhibits a motor
neuron serving the same muscle.
Hemoglobin and RBC
Hemoglobin transports oxygen and serves as an acid–base buffer.
• Red blood cells facilitate carbon dioxide removal.
What type of lever is triceps extension
first class, ( I know stupid)
Power
work x Time (s)
Power (W)
Work
Force x displacement(m)
Work ( J)
negative work
work performed on a muscle rather than by a muscle
Rotation work
Torque ( Nm) x angular displacement
force and speed of contraction relationship
force capability of muscle declines as the
velocity of contraction increases.
strength to mass ration small and large athletes
Given constant body proportions, the smaller athlete has a higher strength-
to-mass ratio than does the larger athlete.
Catabolism:
the breakdown of large molecules into smaller molecules, associated with
the release of energy.
Anabolism:
the synthesis of larger molecules from smaller molecules; can be
accomplished using the energy released from catabolic reactions.
Metabolism:
the total of all the catabolic or exergonic and anabolic or endergonic
reactions in a biological system.
Three basic energy systems exist in muscle cells to replenish ATP:
The phosphagen system
• Glycolysis
• The oxidative system
Phosphagen System
Provides ATP primarily for short-term, high-intensity activities
active at the start of all exercise regardless of
intensity
The phosphagen system uses the creatine kinase reaction to maintain the
concentration of ATP.
• The phosphagen system replenishes ATP rapidly.
Glycolysis
The breakdown of carbohydrates, either glycogen stored in the muscle or glucose
delivered in the blood, to resynthesize ATP
The end result of glycolysis (pyruvate) may proceed in one of two directions:
1) Pyruvate can be converted to lactate.
• ATP resynthesis occurs at a faster rate but is limited in duration.
• This process is sometimes called anaerobic glycolysis (or fast
glycolysis).
• 2) Pyruvate can be shuttled into the mitochondria.
• When pyruvate is shuttled into the mitochondria to undergo the Krebs
cycle, the ATP resynthesis rate is slower, but it can occur for a longer
duration if the exercise intensity is low enough.
• This process is often referred to as aerobic glycolysis (or slow
glycolysis).
Glycolysis and the Formation of Lactate
The formation of lactate from pyruvate is catalyzed by the enzyme lactate
dehydrogenase.
• The end result is not lactic acid.
• Lactate is not the cause of fatigue.
• Glucose + 2Pi + 2ADP → 2Lactate + 2ATP + H2O
• Lactate can be transported in the blood to the liver, where it is converted
to glucose.
• This process is referred to as the Cori cycle.
Glycolysis Leading to the Krebs Cycle
Pyruvate that enters the mitochondria is converted to acetyl-CoA.
• Acetyl-CoA can then enter the Krebs cycle.
• The NADH molecules enter the electron transport system, where they can
also be used to resynthesize ATP.
• Glucose + 2Pi + 2ADP + 2NAD+ → 2Pyruvate + 2ATP + 2NADH +
2H2O
Energy Yield of Glycolysis
Glycolysis from one molecule of blood glucose yields a net of two ATP
molecules.
• Glycolysis from muscle glycogen yields a net of three ATP molecules.
Control of Glycolysis
Stimulated by high concentrations of ADP, Pi, and ammonia and by a
slight decrease in pH and AMP
• Inhibited by markedly lower pH, ATP, CP, citrate, and free fatty acids
• Also affected by hexokinase, phosphofructokinase, and pyruvate kinase
Lactate Threshold and Onset of Blood Lactate
Lactate threshold (LT) represents an increasing reliance on anaerobic
mechanisms.
• LT is often used as a marker of the anaerobic threshold.
• Lactate threshold (LT): the exercise intensity or relative intensity at which
blood lactate begins an abrupt increase above the baseline concentration.
• LT begins at 50% to 60% of maximal oxygen uptake in untrained
individuals.
• It begins at 70% to 80% in trained athletes.
• OBLA is a second increase in the rate of lactate accumulation.
• It occurs at higher relative intensities of exercise.
• It occurs when the concentration of blood lactate reaches 4 mmol/L.
The Oxidative (Aerobic) System
Primary source of ATP at rest and during low-intensity activities
• Uses primarily carbohydrates and fats as substrates
• Glucose and Glycogen Oxidation
• Metabolism of blood glucose and muscle glycogen begins with glycolysis
and leads to the Krebs cycle. (Recall: If oxygen is present in sufficient
quantities, the end product
of glycolysis, pyruvate, is not converted to lactate but is transported to the
mitochondria, where it is taken up and enters the Krebs cycle.)
• NADH and FADH2 molecules transport hydrogen atoms to the electron
transport chain, where ATP is produced from ADP.
Fat Oxidation
Triglycerides stored in fat cells can be broken down by hormone-sensitive
lipase. This releases free fatty acids from the fat cells into the blood,
where they can circulate and enter muscle fibers.
• Some free fatty acids come from intramuscular sources.
• Free fatty acids enter the mitochondria, are broken down, and form acetyl-
CoA and hydrogen protons.
• The acetyl-CoA enters the Krebs cycle.
• The hydrogen atoms are carried by NADH and FADH2 to the
electron transport chain.
Protein Oxidation
Protein is not a significant source of energy for most activities.
• Protein is broken down into amino acids, and the amino acids are
converted into glucose, pyruvate, or various Krebs cycle inter-mediates to
produce ATP.
Control of the Oxidative (Aerobic) System
Isocitrate dehydrogenase is stimulated by ADP and inhibited by ATP.
• The rate of the Krebs cycle is reduced if NAD+ and FAD2+ are not
available in sufficient quantities to accept hydrogen.
• The ETC is stimulated by ADP and inhibited by ATP
Effect of event duration and intensity on primary energy system used 0-6 6-30 30-2min 2-3min > 3min
- 0-6 seconds, extremely high intensity, phosphagen
- 6-30 seconds, very high intensity, phosphagen and fast glycolysis
- 30 sec – 2 minutes, high intensity, fast glycolysis
- 2-3 minutes, moderate intensity, fast glycolysis and oxidative system
- > 3 minutes, low intensity, oxidative system
Ranking of rate and capacity of ATP production
• 1 = fastest/greatest, 5 = slowest/least
Phosphagen: Rate of ATP production: 1, Capacity: 5
• Fast Glycolysis: Rate of ATP production: 2, Capacity: 4
• Slow Glycolysis: Rate of ATP production: 3, Capacity: 3
• Oxidation of Carbohydrates: Rate of ATP production: 4, Capacity: 2
• Oxidation of Fats/Proteins: Rate of ATP production: 5, Capacity: 1
Substrate Depletion and Repletion
• Phosphagens
Creatine phosphate can decrease markedly (50-70%) during the first stage (5-30
seconds) of high-intensity exercise and can be almost eliminated as a result of
very intense exercise to exhaustion.
• Postexercise phosphagen repletion can occur in a relatively short period; complete
resynthesis of ATP appears to occur within 3 to 5 minutes, and complete creatine
phosphate resynthesis can occur within 8 minutes.
Substrate Depletion and Repletion
Glycogen
The rate of glycogen depletion is related to exercise intensity.
• At relative intensities of exercise above 60% of maximal oxygen uptake,
muscle glycogen becomes an increasingly important energy substrate; the
entire glycogen content of some muscle cells can become depleted during
exercise.
• Repletion of muscle glycogen during recovery is related to postexercise
carbohydrate ingestion.
• Repletion appears to be optimal if 0.7 to 3.0 g of carbohydrate per kg of
body weight is ingested every 2 hours following exercise.
Bioenergetic Limiting Factors in Exercise Performance
Light Marathon
Most limiting to least limiting Muscle Glycogen: 5 • Liver Glycogen: 4-5 • Fat Stores: 2-3 ATP and Creating Phosphate: 1 Lower pH: 1
Bioenergetic Limiting Factors in Exercise
Moderate (1500 m run)
Most limiting to least Muscle Glycogen: 3 Lower pH: 2-3 Liver Glycogen: 2 ATP and Creating Phosphate: 1-2 Fat Stores: 1-2
Bioenergetic Limiting Factors in Exercise Performance
Heavy (400 m run)
Most limiting to least Lower pH: 4-5 ATP and Creating Phosphate: 3 • Muscle Glycogen: 3 • Liver Glycogen: 1 • Fat Stores: 1
