Physiology

7.1, 7.2, 7.3 - Human Energy Systems

Nutrients

• chemical substances obtained from food

• used by the body for processes

• bodies need to supply energy, regulate cellular activities

Three key energy nutrients

• carbohydrates

  • primary energy source

  • necessary for those who are very physically active

  • provides materials to build cell membranes and to provide energy used by cells

  • broken down into glucose

    • stored as glycogen in liver and skeletal muscle

  • ex. of carbs include sugars and starches

• lipids (fats)

  • most energy dense nutrient - most energy per gram - 9kcal/g

  • go-to energy source for long periods of low-moderate intensity activities

  • stored in body as adipose tissue

  • broken down into fatty acids, which are stored as triglycerides

• protein

  • only used when other energy stores are emptied out - starvation

  • 20 amino acids that are building blocks for protein

    • 9 are essential - must be obtained from food

  • 4kcal

  • no protein energy reserves in body

    • protein exists as body tissues

ATP - adenosine triphosphate

• obtained from food

• broken down from glucose

• energy is released during hydrolysis of ATP, which is used to fuel cellular processes

  • ATP → ADP + P + Energy

Two energy systems

• anaerobic system

  • occurs without oxygen

  • happens quickly in muscle fibres

  • high intensity - breathing heavily at the end of exercise

• aerobic system

  • does require oxygen

  • leads to the complete breakdown of glucose

  • can’t generate ATP quickly, but produces a lot of ATP

  • able to get in enough oxygen for the activity you’re doing

Three metabolic pathways

• ATP-PC (anaerobic alactic)

  • does not use glucose

  • alactic = no build up of lactic acid

  • used for activities that require high amounts of energy for short amount of time (10 seconds or under)

    • ex. shotput, weightlifting, 100 m sprint

  • allows for quick, intense muscle contraction

  • ATP fuels activity for about 2 seconds

  • ATP is produced from phosphocreatine - small amounts stored in muscle, readily available

    • PC → P + C + Energy

    • Energy is used to resynthesize ATP

      • PC + ADP → ATP + Creatine

    • after 10 seconds, no more PC in muscles - about 2-5 minutes to recover PC

• Glycolysis (anaerobic lactic)

  • when all of PC is used up, body uses this system

  • allows for longer bursts of energy - 10s - 2 minutes

  • partial breakdown of glucose yields 2 ATP molecules and pyruvic acid, which is converted into lactic acid in the absence of oxygen

  • too much lactic acid builds up around 2 minute mark - muscle shuts down

    • Lactic acid threshold - lactic acid build up is more than your body can remove - muscles shut down

      • training results in improved cardiorespiratory fitness

        • increased number of mitochondria, aerobic capacity, ability to clear lactic acid

        • untrained - 50-60% of maximum intensity

        • trained - 70-80% of max intensity

• Cellular respiration (aerobic)

  • main source of energy during endurance events (2 minutes or longer)

  • complete breakdown of glucose produces 36 molecules of ATP - but it takes a long time to break down, which is why cellular respiration is only used for low-moderate intensity activities

  • occurs in the mitochondria of cells

  • three sub-pathways

    • glycolysis: break down of glucose produces 2 ATP molecules and pyruvic acid

    • krebs cycle: pyruvic acid does not convert into lactic acid - instead, it’s converted into acetyl CoA, which enters the krebs cycle, which takes place in mitochondria - produces hydrogen ions and 2 ATP molecules

    • electron transport chain: hydrogen ions enter the electron transport chain - takes place in mitochondria and yields ~ 32-34 ATP molecules

  • fatty acids are used during the aerobic energy system

    • beta oxidation is the process where fatty acids are converted into acetyl-CoA

    • acetyl-CoA then enters the krebs cycle

7.4 - Muscle Fiber Types and Athletic Performance

Different types of muscle fibers - every person has a different distribution of fast & slow twitch muscle fibers, different muscle fibers function differently and are more adapted to one energy system than another

Slow-twitch muscle fibers - type I fibers: slow oxidative

• red or dark in colour bc of high myoglobin content

• smaller

• able to hold oxygen better

• used in the aerobic energy system

• generate small amounts of energy slowly, but a lot of muscular endurance

  • good for long-distance or endurance activities

Fast-twitch muscle fibers - 2 types

• pale in colour

• generate large amounts of force quickly

• high intensity activities

• uses the anaerobic energy system

• type IIA: Fast-oxidative glycolytic

  • second fastest

  • used in anaerobic glycolysis system

• type IIB: Fast-glycolytic

  • fastest contraction speed

  • used in anaerobic alactic system

Tonic muscle

• muscles that assist with maintaining posture and stability

• able to stay contracted for long periods of time

• high percentage of type I fibers

Phasic muscles

• good for power activities → sprinting, jumping

• only used when needed/stimulated to contract

• higher percentage of type IIA and IIB muscle fibers

Myoglobin

• protein that stores oxygen in muscles

• slow twitch muscle fibers are high in myoglobin as they require oxygen to function

• fast twitch fibers have less myoglobin

Implications for training

• able to change muscle fiber make up

• a sprinter will benefit from doing powerful training exercises to increase the number of type II fibers

8.1 - The Structure of the Cardiovascular System

The heart

• Structure of the heart

  • Interventricular septum

    • separates the heart into left and right sides

    • prevents oxygenated blood from mixing with deoxygenated blood

  • Pulmonary circulation

    • pumps deoxygenated blood to the lungs

  • Systemic circulation

    • pumps oxygenated blood from the lungs to the rest of the body

  • Pericardium

    • tough protective sac that fits loosely over the heart

    • it’s loose bc the heart needs to expand and contract

  • Epicardium

    • outer layer of heart that lies against the pericardium

  • Myocardium

    • cardiac muscle that forms the walls of the heart

    • lies directly under the epicardium

  • Endocardium

    • inner-most layer of heart muscle

    • lines the inside of the heart

• Chambers of the heart

  • atria (sing. atrium)

    • upper chambers of heart

    • receives blood from body and pumps blood to ventricles

  • ventricles

    • lower chambers of heart

    • receives blood from atria and pumps blood to body

• Valves

  • atrioventricular valves

    • allow blood to flow from your atria to your ventricles

    • attached to ventricle wall by strands of strong tissue called chordae tendinae

    • tricuspid valve

      • right side of heart

      • 3 flaps

    • bicuspid valve

      • left side of heart

      • 2 flaps

  • semilunar valves

    • pulmonary semilunar valve

      • right side valve where blood leaves ventricles

    • aortic semilunar valve

      • left side

      • separates aorta from left ventricle

• Path of bloodflow

  • deoxygenated blood from your body enters the heart from the superior and inferior vena cava → enter right atrium → goes through tricuspid valve → enters right ventricle → goes out left and right pulmonary arteries → enters lungs → blood becomes oxygenated through gas exchange → blood pumped back into heart from right and left pulmonary veins → enters left atrium → goes through bicuspid valve → goes into left ventricle → goes through ascending and descending aorta and is pumped to body → gas exchange occurs in muscles and organs → deoxygenated blood travels through veins and returns to heart

Human vascular system

• aorta → large arteries → medium arteries → arteriole → capillaries → venules → medium veins → large veins → vena cava

• arteries

  • carry blood away from heart

• veins

  • carry blood towards the heart

  • one-way valves prevent backflow of blood

• arterioles

  • vessels in blood circulation that branch from arteries and lead to capillaries

  • surrounded by smooth muscle

    • regulates blood flow

    • contract: constricts arteriole and reduces amount of blood flow to certain area

    • relax: opens arteriole and increases the amount of blood flow to a certain area

    • arterioles that supply blood to muscles during exercise is vasodilated, increasing the blood flow to muscles

• capillaries

  • gas exchange from blood to tissues

• skeletal muscle pump

  • contraction of skeletal muscle pushes on veins, which causes blood to flow back to heart

  • 

• thoracic pump

  • inspiration → pressure in chest cavity decreases, pressure in abdominal cavity increases

  • veins in abdominal cavity has high pressure and veins in chest cavity has low pressure → blood flows from the veins in abdominal to chest cavity

• nervous system

  • venoconstriction

    • constricts veins to allow more blood to return to the heart

Composition of blood

• plasma

  • makes up 55% of blood

  • 90% water

• blood cells

  • make up 45% of blood

  • red blood cells

    • 99%

  • white blood cells

    • immune system

    • protects body from disease

    • >1%

  • platelets

    • clotting blood

    • >1%

Blood pressure

• systolic blood pressure

  • max pressure observed in arteries when the ventricles contract and ejects blood to body

• diastolic blood pressure

  • minimum pressure in arteries when ventricles relax and is filling with blood

• high blood pressure → arteries and veins burst

• low blood pressure → poor blood flow

8.2 - Function of cardiovascular system

heart’s electrical conduction system

• syncytium

  • heart with contract with an electrical stimulus

• sinoatrial node

  • located at the entrance of the superior vena cava in the right atrium

  • natural pacemaker - dictates how quick or slow heart contracts

  • electrical impulse starts at sa nodes, stimulates atria to contract and travels to the av node

• atrioventricular node

  • located near tricuspid valve

  • receives signal from sa node, then travels to the bundle of HIS, divided into the left and right bundle branches, and then to the purkinje fibers, which pass the signal to the myocardium that forms the ventricles

electrocardiogram

• p wave

  • atrial depolarization (contraction)

• qrs complex

  • atrium repolarizes (relaxes)

  • ventricle depolarization

• t wave

  • ventricle repolarization

• bradycardia

  • heart rate of 60 beats per minute or less at rest

  • occurs from aerobic exercises

    • heart gets better at pumping blood → less pumps needed

• tachycardia

  • resting heart rate more than 100 beats per minute

cardiovascular dynamics → dramatic changes occurring in the cardiovascular system during exercise

• cardiac output (q)

  • volume of blood pumped out of the left ventricle (blood going to body) in one minute

  • measured by taking stroke volume multiplied by heart rate

    • Q = SV(HR)

    • stroke volume

      • amount of blood per beat going out the left ventricle

      • LVEDV (left ventricular end diastolic volume)

        • amount of blood in the left ventricle after contraction of left atrium

      • LVESV (left ventricular end systolic volume)

        • amount of blood remaining in left ventricle after contraction of the ventricle

      • SV = LVEDV - LVESV

      • affected by LVEDV, blood pressure in aorta, strength of the heart, amount of blood returning to heart (venous return)

  • at rest → 5-6 L/min

  • during exercise → 30 L

    • more blood being pumped out

    • most of blood being redirected to working muscles

Venous return

• venoconstriction

• skeletal muscle pump

• thoracic pump

• nervous stimulation of heart

  • increase in the force of contraction of the heart increases SV

heart diseases

• coronary circulation

  • system of vessels that supply essential materials via blood to the heart muscle

• myocardial infarction (heart attack)

  • blood flow to section of heart becomes blocked due to plaque buildup

  • part of heart is not getting enough oxygen

• coronary artery disease (atherosclerosis)

  • plaque build up

    • accumulation of hard deposits of cholesterol in blood vessels

  • causes

    • poor diet

    • smoking

    • elevated blood lipids

    • hypertension

    • family history

    • lack of physical activity

8.3 - respiratory system

Function of the respiratory system

• supply oxygen to blood

• remove co2 from blood

• regulate blood pH level

respiration

• external respiration

  • occurs in lungs

  • exchange of o2 and co2

• internal respiration

  • exchange of gasses at the tissue level

  • o2 is delivered and co2 is removed

• cellular respiration

  • process in which the cells use o2 to generate energy in the mitochondria

structure of the respiratory system

• conductive zone

  • structures that transport filtered air to the lungs

  • includes the mouth, nasal cavity, pharynx, larynx, trachea, primary and secondary bronchi, and tertiary bronchioles and terminal bronchioles

  • humidifies the air, filters air

• respiratory zone

  • gas exchange between inspired air and blood

  • includes the bronchioles, alveolar ducts, alveolar sacs

  • alveoli has large surface area and moisture ideal for gas exchange

mechanics of breathing

• inspiration

  • active process

  • requires contraction of respiratory muscles

  • diaphragm and intercostal muscles contract, causing air to flow in

  • 

• expiration

  • passive → does not require much energy

  • active → forced breathing during exercise requires the contraction of muscles in thoracic cavity and abdominal wall

  • diaphragm and intercostal muscles relaxes, causing air to go out

  • 

control of ventilation

• stimulation from CNS conducts the contraction of muscles

• breathing depends on overall need of o2, metabolic processes, muscle activity, and production of co2

gas exchange

• alveoli are surrounded by capillaries

• walls of each capillary are one cell thick, making gas exchange easy

• diffusion mediates gas exchange

  • movement of gas, liquid or solid from a region of high concentration to a region of low concentration

  • only occurs if there is a difference in concentration, called a concentration gradient

  • factors that affect diffusion

    • size of concentration gradient (ratio of oxygen to co2)

      • bigger concentration gradient = faster diffusion rate

    • thickness of membrane

      • thinner = easier diffusion

    • surface area between the 2 areas where diffusion occurs

      • more surface area = faster bc more space for gas exchange to occur

oxygen transport

• process by which o2 is absorbed in the lungs and carried throughout body

• binds to hemoglobin

carbon dioxide transport

• process by which co2 in blood is moved into the alveoli and then exhaled from the body

• dissolves in plasma

• binds to hemoglobin

• bicarbonate system

a-vO2: arteriovenous oxygen difference

• difference between amount of oxygen in arteries and veins

• reflects amount of oxygen delivered to the muscle

8.4 - functioning of the respiratory system

respiratory dynamics

• pulmonary ventilation (VE) - breathing

  • exchange of air between the lungs and the environment

  • depends on the intensity of work being done

  • 3 phases

    • rapid on phase

      • very rapid increase in rate to match onset of activity

    • slower exponential increase

    • levelling off at a new steady state level

      • body has had enough time to catch up to the demands of oxygen

• tidal volume

  • normal volume of air displaced during breathing

• respiratory frequency

  • number of breaths taken per minute

• external respiration

  • total gas exchange at lungs

  • factors that increase external respiration

    • increase in breathing

    • increase in blood flow to lungs

• internal respiration

  • exchange of gasses at the tissue level

  • factors that increase internal respiration

    • increase in o2 concentration gradient

    • increase in concentration of co2

    • decrease in pH level

    • increase in temperature

      • warm → increase in gas movement

bohr shift

• results from unloading o2 when theres an increase in co2 production

• during exercise

  • increase in o2 demands for cellular respiration in skeletal muscle

    • greater difference between o2 in blood and muscle → greater gradient → increases diffusion from blood to muscle

  • increase in muscle activity

    • causes an increase in co2 which decreases pH, increases lactic acid, and increases temperature

    • decreases bond between o2 and hemoglobin, resulting in oxygen unbinding from hemoglobin and going into muscle

respiratory diseases

• asthma

  • disease characterized by spasm of the smooth muscles that line the respiratory system, over secretion of mucous, and swelling of the cells lining the respiratory tract

  • can be controlled through the use of medication

• COPD - chronic obstructive pulmonary disease

  • general term that describes a group of diseases that lead to a dramatic decrease in air flow

  • experience shortness of breath when doing normal activities

vo2max

• maximum rate at which oxygen can be used during sustained, intense physical activity

• max volume of oxygen in mL that the body can use in one minute per kilogram of body weight while breathing air at sea level

• tells how efficient oxygen is being delivered → measures aerobic fitness

• limiting factors

  • respiratory system

    • inadequate ventilation

    • oxygen diffusion limitations

  • cardiovascular system

    • inadequate blood flow, cardiac output, or inadequate oxygen-carrying capacity (hemoglobin concentration)

  • working muscle

    • lack of mitochondria

• vo2

  • volume of oxygen consumed

  • proportional to the amount of work being done

  • more work = higher vo2

o2 deficit

• build-up to get to steady state

• difference between oxygen required to perform a task and the oxygen actually consumed prior to reaching a new steady state

• diff between oxygen we need and oxygen we have

• trained individuals reach the steady-state quicker → smaller oxygen deficit

• ventilatory threshold

  • state which ventilation increases more rapidly than workload

  • breathing harder than work demands

• lactate threshold

  • blood lactate concentration begins to rise

  • onset of blood lactate accumulation

    • when lactate levels begin to accumulate rapidly

oxygen uptake during steady state exercise graph

• first 10 seconds

  • o2 requirement is low bc our body is using ATP PC system

• 10 seconds to 2 minutes

  • o2 levels go up

• steady state

  • oxygen we have is matched by the oxygen we need

• oxygen debt

  • breathing hard

  • replenishing oxygen that was used up