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KNSS 202: Exercise Physiology > Midterm Review > Flashcards

Flashcards in Midterm Review Deck (212):
1

Name the steps of muscle fibre contraction: excitation-contraction coupling.

1. Action potential (AP) starts in brain
2. AP arrives at axon terminal, releases acetylcholine (ACh)
3. ACh crosses synapse, binds to ACh receptors on plasmalemma
4. AP travels down plasmalemma, T-tubules
5. Triggers Ca2+ release from sarcoplasmic reticulum (SR)
6. Ca2+ enables actin-myosin contraction

2

How do muscles create movement?

process of actin-myosin contraction

3

Describe what happens during relaxed state.

- No actin-myosin interaction at binding site
- Myofilaments overlap a little

4

Describe what happens during contracted state.

- Myosin head pulls actin toward sarcomere center (power stroke)
- Filaments slide past each other
- Sarcomeres, myofibrils, muscle fiber all shorten

5

Describe what happens after power stroke ends.

- Myosin detaches from active site
- Myosin head rotates back to original position
- Myosin attaches to another active site farther down

6

The muscle filament process continues until:

- Z-disk reaches myosin filaments or
- AP stops, Ca2+ gets pumped back into SR

7

What energy is used for muscle contraction?

adenosine triphosphate (ATP)

8

What does ATP bind to for muscle contraction?

- binds to myosin head
- ATPase on myosin head
- ATP --> ADP + Pi + energy

9

What happens when AP ends?

electrical stimulation of SR stops

10

What is pumped back into SR for muscle relaxation? What happens with it? What is required?

- Ca 2+
- stored until next AP arrives
- requires ATP

11

What happens without Ca2+ for muscle relaxation?

- troponin and tropomyosin return to resting conformation
- Covers myosin-binding site
- Prevents actin-myosin cross-bridging

12

Approx. 50% of fibres in an average muscle are what type?

type 1

13

Type 1 muscle fibres hit peak tension in how long?

110 ms (slow twitch)

14

Type 2 muscle fibres hit peak tension in how long?

50 ms (fast twitch)

15

Type 2 muscle fibres make up what percent of fibres in an average muscle each?

appox. 25%

16

What varies between type 1 and type 2 muscle fibres?

speed of myosin ATPase

17

Fast myosin ATPase =

fast contraction cycling

18

Slower myosin ATPase =

slower contraction cycling

19

What happens during a muscle biopsy?

- Small (10-100 g) piece of muscle removed
- Frozen, sliced, examined under microscope

20

What is gel electrophoresis?

- Type I versus II fibers have different types of myosin
- Separates different types of myosin by size

21

How do type 1 and type 2 fibres vary in terms of SR?

- Type II fibers have a more highly developed SR
- Faster Ca2+ release, 3 to 5 times faster Vo

22

How do type 1 and type 2 fibres vary in terms of motor units?

- Type I motor unit: smaller neuron, <300 fibers
- Type II motor unit: larger neuron, >300 fibers

23

What are the 2 types of muscle contraction?

- static (isometric) contraction
- dynamic contraction

24

Describe static (isometric) contraction.

- Muscle produces force but does not change length
- Joint angle does not change
- Myosin cross-bridges form and recycle, no sliding

25

Describe dynamic contraction.

- Muscle produces force and changes length
- Joint movement produced

26

Describe motor unit recruitment for type 1 and type 2 motor units.

- type 1 motor units = less force
- type 2 motor units = more force
- fewer small fibres versus more large fibres

27

What are the 3 different frequency of stimulation (rate coding)?

- twitch
- summation
- tetanus

28

What is the length-tension relationship?

- Optimal sarcomere length = optimal overlap
- Too short or too stretched = little or no force develops

29

What is the speed-force relationship?

- Concentric: maximal force development decreases at higher speeds
- Eccentric: maximal force development increases at higher speeds

30

Define substrates.

- Fuel sources from which we make energy (adenosine triphosphate [ATP])
- Carbohydrate, fat, protein

31

Define bioenergetics.

- Process of converting substrates into energy
- Performed at cellular level

32

Define metabolism.

chemical reactions in the body

33

How can we calculate energy release?

can be calculated from heat produced

34

1 calorie (cal) =

heat energy required to raise 1 g of water from 14.5 °C to 15.5 °C

35

1000 cal =

1 kcal = 1 Calorie (dietary)

36

What are substrates?

- fuel for exercise
- carbohydrate, fat, protein
- carbon, hydrogen, oxygen, nitrogen

37

Energy from chemical bonds in food stored in what?

high energy compound ATP

38

Resting: ___% carbohydrate, ___% fat

50% carbohydrate, 50% fat

39

Exercise (short):

more carbohydrate

40

Exercise (long):

carbohydrate, fat

41

All carbohydrate converted to:

glucose

42

What happens with carbohydrate that have been converted to glucose?

- 4.1 kcal/g; ~2,500 kcal stored in body
- Primary ATP substrate for muscles, brain
- Extra glucose stored as glycogen in liver, muscles

43

When is glycogen converted back to glucose?

when needed to make more ATP

44

Describe glycogen stores.

- limited (2500 kcal)
- must rely on dietary carbohydrate to replenish

45

What is the energy substrate during starvation?

protein

46

What happens with protein used as energy?

- 4.1 kcal/g
- Must be converted into glucose (gluconeogenesis)

47

Protein can also be converted into what? What is this used for?

- FFAS (lipogenesis)
- For energy storage
- For cellular energy substrate

48

Energy is released at a controlled rate based on what?

- availability of primary substrate
- enzyme activity in metabolic pathway

49

What is the mass action effect?

- Substrate availability affects metabolic rate
- More available substrate = higher pathway activity
- Excess of given substrate = cells rely on that energy substrate more than others

50

Name 4 characteristics of enzymes.

- Do not start chemical reactions or set ATP yield
- Do facilitate breakdown (catabolism) of substrates
- Lower the activation energy for a chemical reaction
- End with suffix -ase

51

ATP is broken down by:

ATPase

52

Enzymes determine ____ yield.

ATP yield

53

Each step in a biochemical pathway requires specific ______.

enzyme(s)

54

More enzyme activity =

more product

55

What is rate-limiting enzyme?

- Can create bottleneck at an early step
- Activity influenced by negative feedback
- Slows overall reaction, prevents runaway reaction

56

Why must the body constantly synthesize new ATP?

ATP storage is limited

57

What are the 3 ATP synthesis pathways?

- ATP-PCr system (anaerobic metabolism)
- Glycolytic system (anaerobic metabolism)
- Oxidative system (aerobic metabolism)

58

What type of system is the ATP-PCr system?

- anaerobic
- substrate level metabolism

59

What is the duration of the ATP-PCr system?

3 to 15s

60

What pathway is used to reassemble ATP because ATP stores are very limited?

ATP-PCr system

61

How does phosphocreatine (PCr): ATP recycling work?

- PCr + creatine kinase --> Cr + Pi + energy
- PCr energy cannot be used for cellular work
- PCr energy can be used to reassemble ATP

62

The ATP-PCr system replenishes what?

ATP stores during rest

63

The ATP-PCr system recycles ATP during _____ until _____.

recycles ATP during exercise until used up (~3-15 s maximal exercise)

64

What type of system is the glycolytic system?

anaerobic

65

What is the duration of the glycolytic system?

- 15s to 2 min.
- need another pathway for longer durations

66

The glycolytic system is the breakdown of ______.

glucose via glycolysis

67

How does the glycolytic system use glucose or glycogen as its substrate?

- Must convert to glucose-6-phosphate
- Costs 1 ATP for glucose, 0 ATP for glycogen

68

The glycolytic system pathway starts with ____, ends with _____.

starts with glucose-6-phosphate, ends with pyruvic acid\

69

The glycolytic system has how many enzymatic reactions total?

10-12

70

Where does the glycolytic system occur?

all steps occur in cytoplasm

71

What is the ATP yield for glycolytic system?

- 2 ATP for glucose
- 3 ATP for glycogen

72

What are the pros of the glycolytic system?

- Allows muscles to contract when O2 limited
- Permits shorter-term, higher-intensity exercise than oxidative metabolism can sustain

73

What are the cons of the glycolytic system?

- Low ATP yield, inefficient use of substrate
- Lack of O2 converts pyruvic acid to lactic acid
- Lactic acid impairs glycolysis, muscle contraction

74

What is Phosphofructokinase (PFK)?

- rate limiting enzyme
- dec. ATP (inc. ADP) --> inc. PFK activity
- inc. ATP --> dec. PFK activity
- also regulated by products of Krebs cycle

75

Glycolysis will give you ~ ___ min maximal exercise.

~2 minutes

76

What type of system is the oxidative system?

aerobic

77

What is the ATP yield of the oxidative system?

- depends on substrate
- 32 to 33 ATP/1 glucose
- 100+ ATP/1 FFA

78

What is the duration of the oxidative system?

steady supply for hours

79

Which is the most complex of the 3 bioenergetic systems?

oxidative system

80

Where does the oxidative system occur?

in the mitochondria, not cytoplasm

81

What are the 3 stages of oxidation of carbohydrate?

- Stage 1: Glycolysis
- Stage 2: Krebs cycle
- Stage 3: Electron transport chain

82

Which systems interact for all activities?

- all 3 systems
- no one system contributes 100%
- one system often dominates for a given task

83

Type 1 fibres have _____ oxidative capacity. Why?

- greater
- more mitochondria
- high oxidative enzyme concentrations
- type II better for glycolytic energy production

84

Describe how endurance training effects fibre type composition.

- enhances oxidative capacity of type II fibres
- develops more (and larger) mitochondria
- more oxidative enzymes per mitochondrion

85

As intensity goes up, so does ...

ATP demand

86

What happens in response to increased intensity?

- Rate of oxidative ATP production increases
- O2 intake at lungs increases
- O2 delivery by heart, vessels increases

87

O2 storage is limited, meaning:

use it or lose it

88

What is a accurate estimate of O2 use in muscle?

O2 levels entering and leaving the lungs

89

The sensory division transmits information from ______ to _____.

periphery to brain

90

What are the 5 major families of sensory receptors?

- Mechanoreceptors: physical forces
- Thermoreceptors: temperature
- Nociceptors: pain
- Photoreceptors: light
- Chemoreceptors: chemical stimuli

91

Name 3 special families of sensory receptors.

- joint kinesthetic receptors
- muscle spindles
- golgi tendon organs

92

Joint kinesthetic receptors are sensitive to:

joint angles, rate of angle change

93

Joint kinesthetic receptors sense:

joint position, movement

94

Muscle spindles are sensitive to:

muscle length, rate of length change

95

Muscle spindles sense:

muscle stretch

96

Golgi tendon organs are sensitive to:

tension in tendon

97

Golgi tendon organs sense:

strength of contraction

98

The motor division transmits information from _____ to _____.

brain to periphery

99

What are the 2 divisions of the motor division?

- autonomic: regulates visceral activity
- somatic: stimulates skeletal muscle activity

100

The autonomic nervous system controls:

involuntary internal functions

101

Name some exercise-related autonomic regulation.

- HR, BP
- lung function

102

What are the 2 complementary divisions of the autonomic nervous system.

- sympathetic nervous system
- parasympathetic nervous system

103

Describe the sympathetic division of the autonomic nervous system.

- fight or flight
- prepares body for exercise

104

Sympathetic stimulation results in:

- increased HR, BP
- increased blood flow to muscles
- increased airway diameter (bronchodilation)
- increased metabolic rate, glucose levels, FFA levels
- increased mental activity

105

Describe the parasympathetic division of the autonomic nervous system.

- rest and digest
- active at rest
- opposes sympathetic effects

106

Parasympathetic stimulation results in:

- increased digestion, urination
- conservation of energy
- decreased heart rate
- decreased diameter of vessels and airways

107

A _____ ______ carries AP to muscle.

motor neuron

108

AP spreads to _____ ______ of motor unit.

muscle fibres

109

Fine motor control means _____ fibres per motor unit.

fewer

110

Gross motor control means _____ fibres per motor unit.

more

111

Describe the homogeneity of motor units.

- Fiber types not mixed within a given motor unit
- Either type I fibers or type II fibers
- Motor neuron may actually determine fiber type

112

Nervous system = ______ communication.

electrical

113

Endocrine system = ______ communication.

chemical

114

The endocrine system is _____ responding and _____ lasting than the nervous system.

- slower responding
- longer lasting

115

The endocrine system maintains homeostasis via ______.

hormones

116

What are hormones?

- chemicals that control and regulate cell/organ activity
- act on target cells

117

The endocrine system constantly monitors ____ ____.

internal environment

118

The endocrine system coordinates...

integration of physiological systems during rest and exercise

119

The endocrine system maintains ______ during exercise.

homeostasis

120

How does the endocrine system maintain homeostasis during exercise?

- controls substrate metabolism
- regulates fluid, electrolyte balance

121

______ is appetite control centre of brain.

hypothalamus

122

Satiety centre is in _____ _____.

ventromedial nucleus

123

Hunger centre is in _____ _____.

lateral hypothalamus

124

___ _____ releases hormones that affect hunger signals.

GI tract

125

What is cholecyctokinin (CCK)?

- stimulated when stomach is full
- decreases appetite

126

What is glucagon-like peptide (GLP-1)?

- released in small intestine
- decreases appetite

127

What is peptide YY (PYY)?

- released in small intestine
- decreases appetite

128

What is ghrelin?

increases appetite

129

Adipose is an _____ organ.

endocrine

130

Leptin is released from where? What does it do?

- released from adipose stores
- reduces hunger

131

Leptin and ghrelin act in _______ ways.

opposing

132

Obese people have higher ____. Why doesn't this work properly?

- leptin
- resistant to effects

133

*_____ affects hunger and satiety hormones.

exercise

134

*Acute, vigorous exercise increases ____ and ___, doing what to hunger?

- PYY and GLP-1
- reducing hunger

135

*How does exercise training affect ghrelin?

does not affect it except in energy deficit

136

Looking at substrate metabolism efficiency, 40% of substrate energy -->

ATP

137

Looking at substrate metabolism efficiency, 60% of substrate energy -->

heat

138

Heat production increases with _____ production.

energy

139

How can energy expenditure be measured with direct calorimetry?

- Can be measured in a calorimeter
- Water flows through walls
- Body temperature increases water temperature

140

What are the pros of measuring energy expenditure with direct calorimetry?

- Accurate over time
- Good for resting metabolic measurements

141

What are the cons of measuring energy expenditure with direct calorimetry?

- Expensive, slow
- Exercise equipment adds extra heat
- Sweat creates errors in measurements
- Not practical or accurate for exercise

142

How can energy expenditure be measured indirectly?

- estimate total body energy expenditure based on O2 used, CO2 produced
- measures respiratory gas concentrations
- only accurate for steady-state oxidative metabolism

143

Older methods of measuring energy expenditure indirectly are ______ but ____.

accurate but slow

144

New methods of measuring energy expenditure indirectly are ______ but ____.

faster but expensive

145

What is VO2?

- volume of O2 consumed per minute
- rate of O2 consumption
- volume of inspired O2 [minus] volume of inspired CO2

146

What is VCO2?

- volume of CO2 produced per minute
- rate of CO2 production
- volume of expired CO2 [minus] volume of inspired CO2

147

What are 3 ways of measuring energy expenditure?

- directly
- indirectly
- respiratory exchange ratio

148

O2 usage during metabolism depends on...

type of fuel being oxidized

149

More carbon atoms in molecule =

more O2 needed

150

Glucose (C6H12O6) < ______

palmitic acid (C16H32O2)

151

What is the respiratory exchange ratio (RER)?

- Ratio between rates of CO2 production, O2 usage
- RER = VCO2 / VO2

152

RER for 1 molecule glucose =

1.0

153

Work out why RER for 1 molecule glucose is 1.0.

- 6 O2 + C6H12O6--> 6 CO2 + 6 H2O + 32 ATP
- RER = VCO2 / VO2 = 6 CO2/6 O2 = 1.0

154

RER for 1 molecule palmitic acid =

0.70

155

Work out why RER for 1 molecule palmitic acid is 0.70.

- 23 O2 + C16H32O2 --> 16 CO2 + 16 H2O + 129 ATP
- RER = VCO2 / VO2 = 16 CO2/23 O2 = 0.70

156

The RER predicts:

- substrate use
- kilocalories/O2 efficiency

157

Name 4 indirect calorimetry limitations.

- CO2 production may not = CO2 exhalation
- RER inaccurate for protein oxidation
- RER near 1.0 may be inaccurate when lactate buildup ( ) CO2 exhalation
- Gluconeogenesis produces RER <0.70

158

What is metabolic rate?

rate of energy use by body

159

Based on whole-body O2 consumption and corresponding caloric equivalent, what is RER at rest?

~0.80

160

Based on whole-body O2 consumption and corresponding caloric equivalent, what is VO2 at rest?

~0.3 L/min

161

Based on whole-body O2 consumption and corresponding caloric equivalent, what is metabolic rate at rest?

~2000 kcal/day

162

What is basal metabolic rate (BMR)?

rate of energy expenditure at rest

163

When is BMR taken?

- In supine position
- Thermoneutral environment
- After 8 h sleep and 12 h fasting

164

Minimum energy requirement for living is related to...

fat-free mass (kcal x kg FFM^-1 x min^-1)

165

Name 5 factors that affect BMR.

- body SA
- age
- stress
- hormones
- body temperature

166

What is resting metabolic rate (RMR)?

- Similar to BMR (within 5-10% of BMR) but easier
- Doesn’t require stringent standardized conditions
- 1,200 to 2,400 kcal/day

167

Total daily metabolic activity includes...

normal daily activities

168

What is the normal range for total daily metabolic activity?

1800 to 3000 kcal/day

169

What is the total daily metabolic activity range for competitive athletes?

up to 10,000 kcal/day

170

Metabolic rate increases with _____ _____.

exercise intensity

171

Slow component of O2 uptake kinetics during submaximal aerobic exercise means:

- At high power outputs, VO2 continues to increase
- More type II (less efficient) fiber recruitment

172

What is VO2 drift?

- Upward drift observed even at low power outputs
- Possibly due to ventilatory, hormone changes?

173

What is VO2 max?

- maximal O2 uptake
- Point at which O2 consumption doesn’t increase with further increase in intensity
- Best single measurement of aerobic fitness
- Not best predictor of endurance performance

174

When does VO2 max plateau?

after 8 to 12 weeks of training

175

What allows athletes to compete at higher percentage of VO2 max?

more training

176

VO2 max is expressed in:

- L/min
- easy standard units
- suitable for non-weight-bearing activities

177

What is the VO2 max for untrained young men?

44-50 L/min

178

What is the VO2 max for untrained young women?

38-42 L/min

179

Why is there a sex difference in VO2 max?

women's lower FFM and hemoglobin

180

Can any activity be 100% aerobic or anaerobic?

no

181

Estimates of anaerobic effort involve:

- excess postexercise O2 consumption
- lactate threshold

182

What is postexercise O2 consumption?

- O2 demand > O2 consumed in early exercise
- O2 consumed > O2 demand in early recovery

183

If O2 demand > O2 consumed in early exercise, what happens?

- Body incurs O2 deficit
- O2 required − O2 consumed
- Occurs when anaerobic pathways used for ATP production

184

If O2 consumed > O2 demand in early recovery, what happens?

- Excess postexercise O2 consumption (EPOC)
- Replenishes ATP/PCr stores, converts lactate to glycogen, replenishes hemo/myoglobin, clears CO2

185

What is lactate threshold?

point at which blood lactate accumulation increases markedly

186

When lactate threshold is reached, lactate production rate > ____ _____ ____.

lactate clearance rate

187

Lactate threshold is an interaction of _____ and _____ systems.

aerobic and anaerobic

188

Lactate threshold is a good indicator of ...

potential for endurance exercise

189

Lactate threshold is usually expressed as:

percentage of VO2 max

190

Higher lactate threshold =

better endurance performance

191

For 2 athletes with the same VO2 max, higher lactate threshold predicts...

better performance

192

Why is anaerobic capacity hard to measure?

no clear, VO2 max like method for measuring anaerobic capacity

193

Name 3 imperfect but accepted methods for measuring anaerobic capacity?

- maximal accumulated O2 deficit
- wingate anaerobic test
- critical power test

194

What are the 2 definitions of fatigue?

- Decrements in muscular performance with continued effort, accompanied by sensations of tiredness
- Inability to maintain required power output to continue muscular work at given intensity

195

Fatigue is reversible by ____.

rest

196

Fatigue can be caused by:

- metabolic by-products
- muscle soreness

197

How does heat alter metabolic rate?

- increased rate of carbohydrate utilization
- hastens glycogen depletion
- high muscle temperature may impair muscle function

198

At what temperature is time to exhaustion longest?

11 degrees celsius

199

At what temperature is time to exhaustion shortest?

31 degrees celsius

200

Muscle ______ prolongs exercise.

precooling

201

Where does muscle soreness come from?

exhaustive or high-intensity exercise, especially the first time performing a new exercise

202

When is muscle soreness felt?

- can be felt anytime
- acute soreness during and immediately after exercise
- delayed-onset soreness one to two days later

203

What is DOMS?

delayed-onset muscle soreness

204

When is DOMS felt?

1-2 days after exercise bout

205

What does DOMS feel like?

ranges from stiffness to severe, restrictive pain

206

What is a major cause of DOMS? What is it not caused by? Give an example.

- caused by eccentric contractions
- ex. level run pain < downhill run pain
- not caused by blood lactate concentrations

207

Describe the sequence of events in DOMS.

1. high tension in muscle = structural damage to muscle, cell membrane
2. membrane damage disturbs Ca 2+ homeostasis in injured fibre
3. after a few hours, circulating neutrophils
4. products of macrophage activity, intracellular contents accumulate
5. fluids and electrolytes shift into the area, creating edema

208

What happens when membrane damage disturbs Ca 2+ homeostasis in injured fibre?

- inhibits cellular respiration
- activates enzymes that degrade z-discs

209

What happens when intracellular contents accumulate?

- histamine, kinins, K+
- stimulate pain in free nerve endings

210

DOMS = ______ muscle force generation

decreased

211

DOMS results in loss of strength because of 3 factors:

- physical disruption of muscle
- failure in excitation-contraction coupling (appears to be most important)
- loss of contractile protein

212

Name 3 strategies to reduce DOMS.

- Minimize eccentric work early in training
- Start with low intensity and gradually increase
- Start with high-intensity, exhaustive training (soreness bad at first, much less later on)