9/14/21 Regulation of carbohydrate metabolism and exercise effects Flashcards
what occurs when there is increase breathing and heart rate?
increased O2, nutrients, eliminates CO2 and metabolic waste products, transport hormones, maintain body temp, acid-base balance
what occurs when there is increased contraction of muscles
ability to extract O2, choose energy sources and eliminate metabolic waste
what are the two types of fiber that makes up muscle?
fast and slow fiber
slow fiber
type I myosin
fast fiber
type II myosin (IIa and IIB)
what color are slow twitch fibers and why
red due to large amounts of myoglobin
what does slow twitch contain?
large numbers of oxidative enzymes, more mitochondria, more capillaries
what capacity is slow twitch muscle fibers used for?
large capacity for aerobic metabolism, high resistance to fatigue, long distance running
Type IIa fast twitch fiber
hybrid of type I and II, red, lots of mitochondria, use both aerobic and anaerobic for ATP, mid distance running
Type IIb fast glycolytic fibers
white, low myoglobin levels, few mitochondria, use anaerobic metabolism for ATP, short sprints
what are slow twitch fibers better adapted for?
aerobic activity
what can fast twitch fibers maximum generate
tension, but can fatigue quickly
energy source used during exercise in first hours
muscle glycogen provides ~50% of energy, muscle triglycerides and plasma free fatty acids ~25% each
energy source used during exercise in second hour
blood glucose and plasma free fatty acids are providing more of the energy nutrients, as muscle glycogen and triglycerides are being depleted.
energy source used during exercise in third hour
> 70% of energy needs are being provided by blood glucose and plasma free fatty acids.
energy source used during exercise in fourth hour
hours >90 of energy fuel is provided by blood glucose and plasma free fatty acids. Muscle glycogen is fully depleted and muscle triglycerides provide >10% of energy needs.
muscle force- velocity relationship
fast fibers produce greater muscular force at a faster speed than slow fibers.
fast fibers possess higher ATPase activity and more myosin cross bridges than do slow fibers. Therefore ATP is broken down more rapidly in fast fibers when compared with slow fibers.
muscle contractility
measured and expressed as maximal tetanic force or as specific force generated.
Specific force
the max force divided by muscle cross sectional area
Myostatin or growth differentiation factor 8 (GDF8)
- an inhibitor of muscle differentiation and growth
- member of the TGF-β superfamily and binds to the activing type II receptor.
what are the changes in muscle that occur naturally? (3)
- Both endurance and resistance (weight) training result in a shift from a fast 2b myosin to 2a myosin
- Age is associated with a loss of muscle mass (Sarcopenia).
- Muscle loss also occurs with paralysis and with disuse atrophy (broken arm/leg).
Skeletal Muscle Contraction
- The active site on actin is exposed as calcium binds to troponin.
- The myosin binds actin at its actin-binding site, forming the cross-bridge.
- During the power stroke, the phosphate generated in the previous contraction cycle is released. This results in the myosin head pivoting toward the center of the sarcomere, after which the attached ADP and phosphate group are released.
- A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach.
- The myosin head hydrolyzes ATP to ADP and phosphate, which returns the myosin to the cocked position.
Sources of ATP required for muscle contraction (4)
- glycolysis
- Krebs (TCA) cycle
- Glycogenolysis
- Fatty Acid Oxidation
Glycogen
glycoprotein, consists of core protein “glycogenin”, highly branched 1,6- and 1,4 glycosidic bonds
