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35 Cards in this Set

  • Front
  • Back
what are slow twitch Type 1 fibers used for? what are their characteristics?
long term exercise

small diameter
low glycogen
high myoglobin, O2 capaciy, resistance to fatigue
what are fasttwitch Type 2b fibers used for? what are their characteristics?
short term energy need

large fiber diameter
high glycogen
low myoglobin, O2 capacity, resistance to fatigue
How do cardiac muscles get energy? What are their characteristics?
oxidative phosphorylation (except when well fed)

rich in mito
little glycogen
How does smooth muscle get energy? What does it do?
maintains tension for a long period of time

does not need much energy
what are 3 types of muscle weakness?
insufficient energy supply (not enough ATP)

impaired neurological control (not enough intracellular Ca++)

deficiency in muscle strucutral proteins
what are examples of deficiencies in muscle structural proteins?
muscular dystrophies (Duchenne, Becker)
(Dystrophin deficient - links muscle fibers to sarcolemma)

cardiomyopathies
what are examples of deficiencies in muscle energy supply?
ichemia (lack of O2) like myocardial infarction

genetic diseases of fuel metabolism, like McArdle (Glycogen), Carnitine (FA)
what are examples of deficiencies in muscle Ca+=supply?
myasthenia gravis

neurocontrol compromised acetylcholine receptors
What are the 2 major sources of ATP in muscles (metabolic pathways)? What molecules do they use?
Glycolysis - glucose - from glycogen or blood glucose

Oxidative Phosphorylation - NADH and FADH2 from TCA cycle, B oxidation FAs, oxidation of branched chain AAs like Ile, Leu, Val, conversion lactate to pyruvate
What is the role of creatine phosphate in muscle energy metabolism?
way to store high energy phosphate (ATP)

creatine --creatine phospokinase --> creatine phosphate
why cant ATP be stored as it is?
is an allosteric regulator of many enzymes
what do increased blood creatine levels indicate?
impaired kidney function
How is ATP regenerated?
adp --adenylate kinase --> ATP + AMP
What does AMP upregulate?
glycolysis
glycogenolysis
B oxidation of FAs
Which disease would cause an increase in creatine kinase levels in a patient's blood?
McArdle Syndrome

usually not secreted in circulation unless muscle is damaged
What is the key regulated enzyme in glycolysis?

How does its regulation differ in liver, skeletal and cardiac muscle?
Phosphofruktokinase 2 (PFK2)

liver - glucagon/epinephrine -> phosphorylate PFK2 > downregulate glycolysis

skeletal - no phosphorylation > no regulation at PFK2 level > glycolysis just occurs

cardiac - insulin/epinephrone, AMP -> phosphorylation PFK2 -> glycolysis upregulated
What is the major regulated step of B oxidation?

what inhibits it?
Carnitine palmitoyl transferase 1 (CPT1)

inhibited by malonyl coA (cant get into mito matrix)


High ACC2 = high MCoA = CPT1 inhibited and cant degrade FAS

High MCoADC = low MCoA = FA degradation
how is energy produced in the heart when fasting blood glucose levels?
degradation of long chain fatty acids
> high levels acetyl coA and citrate
> limit energy production from glucose through glycolysis (PFK1 and PDH inhibited)

favors TCA not glycolysis
how is energy produced in the heart when high blood glucose levels?
increase glycolysis through insulin (GLUT 4 uptake)
> activates PFK2
> activate PFK1
> activates glycolysis
When you eat carbs, what enzyme is activated by phoshorylation throug h action of insulin in heart muscle?
PFK-2
What is the effect of ischemia in cardiac muscle (cant get O2 to muscle)?
no O2 > mito ATP synthesis and B oxidation FAs inhibited

> elevated AMP/ATP ratio

> glucose uptake, PFK1 and PFK2 activation

> glycolysis

> pyruvate converted to lactate
what is the source of energy for resting skeletal muscle?
aerobic metabolism = oxidative phosphorylation, FA oxidation

high blood glucose > glycogen

high branched AAs> make energy

high citrate > reduced glycolysis (reduce PFK1) and B oxidation FAs (activate ACC2)
what is the source of energy for fasting skeletal muscle?
glucose uptake downregulated (GLUT 4 levels decrease)

FA used as fuel

low ATP > high AMP > activate AMP-PK > deactivate ACC2 > low malonyl coA > B oxidation FAs > actyl coA . inhibit pyruvate dehydrogenase > limit use of glucose as energy source
what is the source of energy for onset exercise of skeletal muscle?
first minute = anaerobic glycolysis > quick ATP supply

then glucogenolysis and glycolysis activated (need O2) by AMP and increased Ca++
What is the most sensitive reflection of energy in skeletal muscles during exercise?
AMP

changes more than ADP or ATP do when resting and exercising
What changes in metabolite levels of skeletal muscle would be observed after sprinting?
decreased ATP

decreased creatine phosphate

increased lactate
what provides energy during high intensity exercise?
B oxidation of FAs and TCA cycle

not fast enough > AMP still high > activate PFK1 > anerobic glycolysis > pyruvate which cant enter TCA cycle because it is blocked up > lactate
Why cant high intensity exercise be maintained for a long time?
musle glycogen stores depleted

lactic acidosis
what happens to lactate in resting skeletal, cardiac muscle, and liver?
liver > cori cycle > gluconeogenesis > glucose others can use

muscle > lactate dehydrogenase converts it back to pyruvate if low NADH/NAD ratio > energy
what compensates for lactic acidosis during exercise?
purine nucleotide cycle accelerated
> fumarate > TCA cycle
and AMP > IMP which produces NH3 > transported fro muscle (glutamine) to kidney (glutamine) > NH3 helps to excrete protons in urine
what is the source of energy for long term exercising skeletal muscle?
aerobic oxidation of FAs and glucose (BOTH)

less lactate made

40 min > liver flycogen

4 hours> gluconeogenesis increases, glucogenolysis decreases

then use FAs from fat
What do muscles preferentially get energy from?

when dont they?
fatty acids

except right after eating
What relies on glucose for energy?
anaerobic glycolysis like at start of exercise or high intensity

long term exercise

fast twitch muscles (limited oxidative supply)
what enzymatic modification is most characteristic in liver of marathon runner 35 min into race?
phosphorylation of glycogen phosphorylase (epinephrine)
What is the most characteristic metabolic change in fast twitch muscles of the legs of a sprinter during a 100 m event?
Increased glycogen degradation

normal B oxidation