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study guide for Exercise Physiology Dr. Sophie Kim...

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1. Homeostasis & feedback control system • Define the term homeostasis. How does it differ from the term steady state? H       latively constant and “normal” internal environment during resting conditions. Dynamic constancy. Stressors to homeostasis are 1. Exercise (FITT) 2. Heat 3. Altitude 4. Resistance 5. Humidity -Steady state is a physiological variable that is unchanging, but not necessarily normal. Balance between the demands placed on the body and the body response to those demands. Ex. Body temp or arterial blood pressure • Explain the term negative and positive feedback.    e  response reverses the initial disturbance in homeostasis. Ex. Increase in extracellular CO2 triggers a receptor sends information to respiratory control centerrespiratory muscles are activated to increase breathing CO2 concentration returns to normal. Most control systems work via negative feedback - Positive feedback: response increases the original stimulus. Ex. Giving birth: head of baby pushes against cervixnerve impulses from cervix transmitted to the brainbrain stimulates pituitary gland to secret oxytocin oxytocin carried in the bloodstream to uterus oxytocin stimulates uterine contractions and pushes the baby toward the cervix the cycle repeats until baby is born • What is a biological control system? - A series of interconnected components that maintain a physical or chemical parameter at a near constant value. - Failure of any component of a control system results in a disturbance of homeostasis • Discuss the concept of gain associated with a biological control system -

The gain (precision) of a control system is the degree to which a control system maintains homeostasis (its capability). System with large gain is more capable of maintaining homeostasis than system with low gain. Ex pulmonary and cardiovascular systems have large gains. (which means they have a grater capability of maintaining homeostasis)

• The components of a biological control system (Figure 2.4, p32) - The major components: - Sensor of receptor o Detects changes in variable - Control center o Assesses input and initiates response - Effector o Changes internal environment back to normal • The five major cell signaling mechanisms that participate in the control of homeostasis and cellular adaptation (Figure 2.6, p35) -Intracrine: cell signaling within a cell -Juxtacrine: cell signaling from one cell to an adjacent cell (touching) -    ,           a    

               -Endocrine: cell produces chemical messenger, which is sent out and travels through the blood stream to target cells in remote tissue. -

2. Bioenergetics 

Define the following terms: 1) Glycolysis 2) Glycogenolysis 3) Glycogenesis 4) Gluconeogenesis 5) Glucose 6) Glucagon 7) lipolysis o Glycolysis: the breakdown of glucose or glycogen, it is an anaerobic process. It requires 10-12 enzymatic reactions to break down glycogen and lactice acid producing ATP. It occurs in the cytoplasm and provides about two minutes of energy. Without oxygen present, pyruvic acid gets turned into lactate o Glycogenolysis: The breakdown of glycogen into glucose o Glycogenesis: the formation of glycogen from sugar o Gluconeogenesis: glucose synthesis from a non-carbohydrate source o Glucose: carbohydrate, simple sugar, blood sugar, it can be found in foods or be formed in the digestive tract, used to make ATP in the body o Glucagon: hormone in the pancreas that promotes the breakdown of glycogen to glucose in the liver o Lipolysis: the breakdown of fat, slow process that only happens after several minutes of exercise

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Explain the following energy systems: 1) APT-PC 2) anaerobic metabolism

(Figure 3.14, p51) 3) Krebs Cycle 4) Electron Transport Chain o ATP-PC system: provides energy for muscular contraction at the onset of exercise and during short term high intensity exercise. It is an anaerobic process. PC+ADP ATP +C the reaction is catalyzed by the enzyme creatine kinase. o Anaerobic metabolism: glucose must be phosphorylated to form glucose 6-phosphate at the first step in glycolysis o Krebs cycle: in presence of oxygen the pyruvic acid gets converted into the acetyl CoA and this enters the krebs cycle and forms 2 ATP, carbon dioxide, and hydrogen. These hydrogen ions combine with NAD and FAD and these coenzymes carry it to the electron transport chain. o Electron Transport chain: splits NADH and FADH producing hydrogen ions, which are recombined with oxygen to produce water. Electrons produced from the split of NADH and FADH provide the energy for phosphorylation of ADP and ATP. One molecule of glycogen can generate up to 33 molecules of ATP 

What is the function of NAD+ and FAD in the Krebs cycle and the electron transport chain in the aerobic production of ATP The NAD and FAD in the krebs cycle and electron transport chain carry the hydrogen from the krebs cycle to the ETC in order to split and recombine with oxygen to produce water and from this split the electrons created provide energy for the phosphorylation of ADP to ATP. 1 NADH produces 2.5 ATP, one FADH produces 1.5 ATP.

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List the storage form of carbohydrate, fat, and protein o For carbohydrates, glucose is taken up by the muscles and the liver and converted to glycogen. Glycogen is stored in the cytoplasm of muscle cells where it can be quickly used to form atp. It is also stored in the liver where it is converted back to glucose as needed and transported by the blood to the muscle to form ATP o Body stores of fat are larger than carb reserves. Fat is less readily available for cellular metabolism though. Fat is stored as triglycerides and must be broken down to free fatty acids to be used in metabolism. o For protein, it can be used as a minor source of energy but it must be converted to glucose first. Proteins can generate FFA during starvation through lipogenesis. Discuss the interaction between aerobic and anaerobic ATP production during exercise o At the beginning of exercise, the anaerobic ATP production system is used but once it becomes prolonged steady state exercise the aerobic production sets in. Pyruvate that is produced during during glycolysis gets oxidized and goes into the krebs cycle. In anaerobic, it would convert to lactate. Anaerobic is used in short time length activities.

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Explain the Beta Oxidation (Figure 3.20, p57) ****** o Beta-oxidation is the process of oxidizing fatty acids to form acetyl CoA. This occurs in the mitochondria and involves a series of enzyme-catalyzed steps starting with “activated fatty acid” and ends with acetyl-CoA. After getting turned into acetyl-CoA, it goes into the Krebs cycle.

3. Exercise Metabolism 

Identify the predominant energy systems used to produce ATP during the following types of exercise (Figure 4.14, p82): - Short-term, intense exercise (less then 10 sec)

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Anaerobic glycolysis ATP-PCr

- 400-meter dash 

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ATP-PCr anaerobic glycolysis, may switch to oxidative pathways (glycolysis) depending on fitness level.

- 20-kilometer race (12.4 miles) 

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Briefly explain how the respiratory exchange ratio is used to estimate which substrate is being utilized during exercise. -

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Oxidative pathways o ETC and Krebs cycle

At low intensity exercises, fat is the main source of energy. The RER shows what percentage of energy being used is fat, and what percent of energy being used is carbohydrates. The starting value for RER is 0.7 at rest. As the intensity of the exercise increases, the RER moves closer to 1.0 which indicates mostly carbohydrate usage. The crossover concept is the point at which our body switches from using mostly fats, to carbs.

What is the Cori Cycle? •

The process of converting lactate that is made from contracting muscles in anaerobic conditions, to glucose which can be reused as a fuel source. This process occurs in the liver through gluconeogenesis where lactate is converted first to pyruvate before it is converted back into glucose.

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Discuss the lactate threshold and removal during exercise •

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Lactate is a byproduct of contracting muscles. The buildup of lactate is constant in the muscles up until about 60% of a subjects VO2 max. At this point, the buildup of lactate grows exponentially in the muscle. This is caused by hypoxia in the muscle to the point where the muscle is not receiving the oxygen needs to contract. This is more likely to occur in fast twitch muscle fibers where anaerobic glycolysis is more common. • Although lactate can be removed with rest, the best way to remove lactate is with low intensity exercise of the muscle between 30-40% of the VO2 max. Most lactate removal occurs within 40 minutes of high intensity exercise. What is VO2 max? •

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VO2 max is the variable used to measure how efficient our body is at utilizing oxygen. In early stages of training, the largest increase in VO2 max is caused by an increase in SV, while long term training training will show a greater increase in the a-vo2 difference Shows aerobic capacity and ability to produce ATP VO2 max = HR max * SV max * (a-vO2) max

4. Hormonal Responses to Exercise • Discuss different pathways between steroid and non steroid hormones (p 93) • Steroid hormones  Formed from cholesterol  Lipid soluble  Receptors are in the cytoplasm or in the nucleus  Capable of direct gene activation  mRNA activation promotes protein synthesis o x.  A        Ovaries (estrogen and progesterone)  Testes (testosterone)  Placenta (estrogen and progesterone)     1. Hormone passes through the plasma membrane 2. Inside target cell the hormone binds to a receptor protein in the cytoplasm or nucleus 3. Hormone-receptor complex binds to hormone response element on DNA, regulating gene transcription 4. Protein synthesis 5. Change n protein synthesis is cellular response • Nonsteroid Hormones  Protein or peptide, and amino acid-derived  Not lipid soluble  Water colube  Triggers a series of intracellular events through second messenger systems, cAMP

Activates cellular enzymes Changes membrane permeability Promotes protein synthesis Changes cellular metabolism Stimulates cellular secretion  Ex.  Thyroid gland (thyroxine and triiodothyronine)  Adrenal medulla (epinephrine and norepinephrine) • Discuss the Hormone-Receptor Interactions (downregulation, upregulation, saturation) • D  decrease in receptor number in response to high concentration of hormone • Upregulation is an increase in receptor number in response to low concentration of hormone • Saturation is when all receptors are bound to the hormone o o o o o

• How do the endocrine hormones (insulin and glucagon) control blood glucose (sugar) levels? •

Insulin stimulates glucose uptake by the cells therefore decreasing blood glucose levels. Glucagon promotes mobilization of glycogen breakdown and glucose release from the liver, therefore increasing blood glucose levels.

• Discuss the regulation of glucose metabolism during exercise (glucagon, epinephrine, norephinephrine, cortisol) •

There is an increase in glucagon, which promotes liver glycogen breakdown and glucose formation from amino acids. An increase in epinephrine promotes glycogenolysis. An increase in norepinephrine also promotes glycogenolysis. An increase in cortisol promotes protein metabolism.

• • Discuss the use of testosterone and growth hormone as aids to increase muscle size and strength •

Testosterone is an anabolic steroid released from the testes that promotes muscle tissue building. It enhances performance and stimulates protein synthesis. Growth hormone stimulates the release of insulin-like growth factors (IGFs) from the liver. IGF-1 promotes muscle growth. Additionally, growth hormone promotes amino acid uptake and protein synthesis which leads to tissue growth.

• Discuss the Hormone Regulation of Fluid and Electrolyte Balance During exercise

(ADH, aldosterone) •

Hemoconcentration, increased plasma osmolarity, and low plasma volume stimulate the release of ADH. ADH promotes the retention of water in the kidneys in an effort to dilute plasma electrolyte concentrations back to normal. Aldosterone secretion is stimulated by a decrease in plasma sodium, blood volume, and blood pressure, as well as an increase in plasma potassium concentration. Aldosterone promotes renal reabsorption of sodium causing the body to retain sodium. Renin’s best friend is aldosterone**

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5. The Nervous System 

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Define depolarization, action potential, repolarization, and hyperpolarization o Action potential: rapid substantial depolarization of the cell membrane o Depolarization: when the inside of the cell becomes less negative relative to the outside of the cell and is caused by a change in the membranes Na+ permeability. Na+ enters the cell. Voltage gated K+ channels slowly begin to open. o Repolarization: returns the cells membrane potential to a negative value. K+ moves from the cell to the extracellular fluid o Hyperpolarization: when the inside of the cell becomes more negative relative to the outside. Sodium potassium pump needed to restore resting membrane potential. Cannot receive any impulses during hyperpolarization. Sodium potassium pump needed to restore resting membrane potential Define motor unit o A single neuron and all the muscle fibers it innervates. It is the smallest division that the system can control individually. Briefly explain resting membrane potential o Resting membrane potential is the difference between the electrical charges inside and outside a cell, caused by separation of charges across the cell membrane, there is a high concentration of K+ inside of the neuron and Na+ on the outside of the neuron. Outside is more positive and inside is more negative. The resting membrane potential is maintained AT -70mV. 3 Na+ out of the cell and 2 K+ into the cell Discuss the function of Golgi tendon organs and muscle spindles. o Golgi tendon organs detect the tension of a muscle on a tendon, providing information about the strength of the muscle contraction. o Muscle spindles sense how much a muscle is stretched, muscle length

What is the difference between synapse and neuromuscular junction? o Synapse: small gap between presynaptic neuron and postsynaptic neuron.

Causes depolarization of postsynaptic membrane o Neuromuscular junction: the site where an α-motor neuron communicates with a muscle fiber. Action potential causes the muscle fibers to contract 

What is the neurotransmitter released at the neuromuscular junction? o Acetylcholine

6. The Skeletal Muscle System 

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Draw and label the microstructure of a skeletal muscle fiber o Myofibrils             o S  Includes Z line, M line, H zone, A band, I band o SR  Storage sites for calcium  Terminal cisternae o TT  Extend from sarcolemma to sarcoplasmic reticulum

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Compare and contrast the major biochemical and mechanical properties of the three primary types of muscle fibers found in human skeletal muscle o Age related muscle loss is associated with sarcopenia o     Slow-twitch fibers  Slow-oxidative fibers  Low intensity  High volume  Low velocity  Have higher aerobic endurance and are well suited to low intensity endurance activities  Ageing may cause increase (shift from type II) o T      Intermediate fibers  Fast-oxidative glycolytic fibers  Medium intensity  Medium volume  Medium velocity  Play a major role in high intensity exercise  With training there is an increase (shift from type IIx)  Ageing causes a decrease (shift to Type 1) o T      Fast-twitch fibers  Fast-glycolytic fibers  High intensity  Low volume  High velocity  Are activated when the force demand of a muscle is high  With training there is a decrease (shift to type IIa)

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Explain three types of muscles o Smooth  Involuntary muscle  Controlled by the autonomic nervous system  Like in the intestine o Cardiac   

Controlled by the autonomic nervous and endocrine systems  The heart o Skeletal  Voluntary muscle  Controlled consciously by the somatic nervous system 

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List the contractile process. Use a step-by-step format illustrating the entire process, beginning with the nerve impulse reaching the neuromuscular junction o Neuromuscular junction is the space between motor neuron and muscle fiber  Motor unit: motor neuron and all fibers it innervates o M    Pocket formed around motor neuron by sarcolemma o Neuromuscular cleft  Short gap between neuron and muscle fiber o Acetylcholine is released from the motor neuron  Causes an end-plate potential (EPP)  Depolarization of muscle fiber o Excitation 1. N       2. A                         n    3. Sodium influx causes depolarization that is conducted down transverse tubules o Contraction 4. Depolarization of t-tubules causes release of Ca++ from sarcoplasmic reticulum (SR) 5. Ca++ binds to troponin, causing shift in tropomyosin to uncover myosin binding sites on actin 6. Myosin binds to actin to form cross bridge 7. Pi released from myosin and cross bridge movement occurs 8. New ATP attaches to myosin, breaking the cross-bridge. Then ATP is broken down to ADP+Pi, which energizes myosin o Relaxation 9. Motor neuron stimulation ends, acetylcholine is no longer released, and muscle fiber repolarizes. 10. Ca++ is pumped back into SR and tropomyosin returns to original position covering myosin-binding sites on actin, and muscle relaxation occurs.

7. The Pulmonary System 

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What is the primary function of the pulmonary system? o Functions of the pulmonary system include ventilation and exchange of O2 and CO2 in the lungs. o During exercise respiration is needed for  Gas exchange between the environment and the body  Regulation of acid-base balance Define the following terms: 1) Hypoxia 2) Ventilation o Hypoxia: a deficiency in the amount of oxygen reaching a tissue  it occurs with failure of the lung to adapt to training.  occurs in elite athletes near-maximal exercise with a decrease of 30-40 mmHg in the lungs.  Approximately 40-50% of elite athletes experience this. o Ventilation: ventilation is the mechanical process of moving air into and out of the lungs Explain the lung volumes and capacities at rest (Figure 10.9, p 223)

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Discuss O2 transport in muscle (Figure 10.18, p 230) Myoglobin is a key player. It delivers oxygen from the muscle cell membrane to the mitochondria to be used for ATP. It can only bind one oxygen molecule at a time.

8. The Cardiovascular System  

Compare the structural and functional differences/similarities between heart muscle and skeletal muscle (Table 9.1, p 190)

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o Discuss the distribution of cardiac output during rest and maximal exercise (Figure 9.23/24, p206-207) o At rest, the majority of blood is sent to the organs. o During exercise, the blood is redistributed to th...