Published on March 18, 2014
Exercise Physiology The Ventilatory and Cardiovascular Systems
INTRO • HOMEOSTASIS • Maintenance of a constant internal environment • Example: temperature, O2 levels • Exercise challenges this • GAS EXCHANGE – Transfer of oxygen & carbon dioxide between 2 systems
IMPORTANT POINT • The ventilatory & cardiovascular systems work together in a highly coordinated way to increase O2 delivery during exercise. • This is the body trying to maintain homeostatis
VENTILATORY SYSTEM • Movement of air in & out of the lungs is due to repeated contraction & relaxation of muscles by the diaphragm & chest wall to increase & decrease the volume (pressure) in the lungs.
I. Structure of the Ventilatory System A. Conducting Airways: *offers a low resistance pathway for air flow *warms and moistens air *mucus and ciliated cells filter air
II. Pulmonary Ventilation: the exchange of air between the atmosphere and lungs (breathing). A. Mechanics of Breathing: 1. Inhalation: *diaphragm contracts and lowers *chest cavity expands increasing volume and decreasing internal air pressure Why can our ribs expand?
2. Exhalation: *Diaphragm relaxes and moves up. *chest cavity volume decreases and internal air pressure increases. *during exercise the intercostal and abdominal muscles act on the ribs to produce greater exhalation
III. Total Lung Capacity: (TLC) maximum volume of lungs after maximum inhalation (vital capacity + residual vol.). A. Tidal Vol.: (TV) Volume of air breathed in and out in any one breath. B. Inspiratory Reserve Vol.: additional inspired air over and above tidal volume.
C. Expiratory Reserve Volume: volume of air in excess of tidal volume that can be exhaled forcibly D. Residual Vol.: (RV) volume of air still in lungs after maximum expiration. E. Vital Capacity: max volume of air exhaled after max inhalation
GAS EXCHANGE • DIFFUSION: Gas will move along a gradient from an area of higher pressure to lower pressure – (or concentration)
GAS EXCHANGE • Challenge during exercise is to ensure homeostasis of gases. • The ventilation and cardiovascular system must therefore make changes.
Explain the Mechanism of Ventilation • Include the actions of the diaphragm and the intercostal muscles, and the relationship between volume and pressure.
When inhalation occurs the external intercostal muscles contract, making the ribcage move up and out. The diaphragm contracts, becoming flat. These contractions increase the volume of the thorax, which drops the pressure inside it bellow atmospheric pressure. Air from outside the body flows to the lungs via mouth or nose. This continues until the pressure in the lungs rises to atmospheric pressure.
• Then during exhalation, the external intercostal muscles contract, moving the ribcage down and in. The abdominal muscles contract, pushing the diaphragm up. These contractions decrease the volume of the thorax, which increases the pressure inside it above atmospheric pressure. Air from the lungs flows out of the body through the mouth or nose. This continues until the pressure in the lungs falls back to atmospheric pressure.
VENTILATION • Minute ventilation = volume of air being exhaled per minute VE (L.min) = VT(L.breath) x Bf(breaths.min) • Complete green box on page 35 text. • What happens to VE during exercise? Why? • What happens when you exercise at altitude versus sea level? • How do ‘freedivers’ hold their breath for so long?
VO2 Max • VO2 Max – the maximum or optimum rate at which the heart, lungs, and muscles can effectively use oxygen during exercise, used as a way of measuring a person's individual aerobic capacity.
IV. CO2 transport in the blood: • CO2 is transported in the blood in the form of bicarbonate • O2 is less soluble in plasma, but easily attaches to hemoglobin – an iron-rich pigment
Increased Carbon dioxide content in blood Detected by respiratory center Ventilation increases because of direct result of blood acidity levels (low pH) D. What’s the role of CO2 in the control of pulmonary ventilation during exercise?
V.Oxygen Transport in the Blood: A. Hemoglobin: (Hb) iron containing pigment that binds with oxygen to form oxyhemoglobin. Hb + 4 O2 Hb4O8
VI. Gas Exchange in the lungs: A. Alveoli: thin membrane sacs at the end of the bronchioles. *serve as the site of gas exchange by diffusion.
Gas Exchange • In the lungs and other body tissues gas exchange takes place in a passive process known as diffusion. • High pressure to lower partial pressure
BLOOD • Total blood volume for a 70kg male is ~5litres • 55% blood fluid is plasma, 45% is blood cells and platelets
VII. Blood: transport vehicle for nutrients, hormones, waste products and electrolytes. 1. Blood Composition: A. Cellular: i. erythrocytes: (RBC’s) Contain hemoglobin that binds to oxygen for transport to tissues.
Electrolytes • Electrolytes are important because they are what your cells (especially nerve, heart, muscle) use to maintain voltages across their cell membranes and to carry electrical impulses (nerve impulses, muscle contractions) across themselves and to other cells. Your kidneys work to keep the electrolyte concentrations in your blood constant despite changes in your body.
Example • When you exercise heavily, you lose electrolytes in your sweat, particularly sodium and potassium. These electrolytes must be replaced to keep the electrolyte concentrations of your body fluids constant. So, many sports drinks have sodium chloride or potassium chloride added to them.
ii. Leukocytes: (WBC’s) defend the body against disease. *produce antibodies *destroy bacteria and viruses *produce marker proteins
iii. Platelets: (thrombocytes) play a role in the clotting of blood.
B. Liquid Component: i. Plasma: 60% total volume of blood. 90% water and 10% solutes • Metabolites and wastes (gases, hormones, vitamins) • Salts (ions) • Plasma proteins
BLOOD • Q&A – What is EPO? And what does it do? – Why is it advantageous for an endurance athlete to have a higher concentration of RBC’s? – How can an athlete naturally increase their RBC stores? – What are some ways athletes are illegally to increase their RBC’s?
Ventilation and Blood Review • During exercise what is the primary function of blood? • Transport from various tissues- gases, nutrients, waste products, hormones, or even heat. • During exercise what is the relationship between the ventilation system and blood? • Ventilation increases as a direct result of increases in blood acidity levels due to increased carbon dioxide content of the blood.
What is the role of the following: • Platelets – Repair after injury • Leucocytes (WBC) – Protecting the body from infection • Erythrocytes (RBC) – Contain hemoglobin and O2 attaches to hemoglobin
VII. Anatomy of the Heart Superior vena cava Tricuspid valve Right atrium Aortic Arch Pulmonary Valve Left atrium Left pulmonary artery Mitral valve or bicuspid valve Septum Left pulmonary veins Left ventricle Right ventricle Inferior vena cava Aortic valve
HEART • PULMONARY CIRCULATION – Delivers deoxygenated blood from right side of the heart to the lungs • SYSTEMIC CIRCULATION – Delivers oxygenated blood from left side of the heart to the body
CIRCULATION PATHWAY Arteries Arterioles Capillaries Venules Veins
CIRCULATION • Arteries: thick muscular walls; O2 rich; transport blood away from the heart • Veins: deoxygenated blood; less muscular; valves to prevent back flow • Capillaries: narrow vessels with thin walls; site of exchange between blood & tissue
THE CARDIAC CYCLE • Atrium: receives blood from a vein • Ventricle: thicker walled, pushes blood out of the heart into arteries • Valves: between chambers; ensures blood travels in 1 direction only • Look at figure 2.3 the Cardiac Cycle
THE CARDIAC CYCLE • Contraction of the heart is initiated by an impulse in the pacemaker (SA and AV node) • The impulse travels through the heart muscle causing contractions in the correct sequence • Contraction rate is affected by hormones & the nervous system
• Use the following website to help you practice your heart anatomy: • http://www.wisc- online.com/Objects/ViewObject.aspx?ID= AP12504 • Do activity: The anatomy of the Heart.
4 5 6 3 2 1
Explain the path of blood from the body to the heart and back out to the body. (8 marks)
• Deoxygenated blood comes from the body to the inferior and superior vena cava. • Blood enters right atrium, pressure increases and tricuspid valve opens • Deoxygenated blood enters right ventricle pressure increases and pulmonary valve opens • Deoxygenated blood goes to the lungs via pulmonary artery where diffusion occurs in the capillary beds- CO2 and O2 exchange occurs
• Oxygenated blood returns via pulmonary veins • Blood enters left atrium pressure increases and bicuspid valve opens • Blood flows into left ventricle pressure increases aortic valve opens • Oxygenated blood flows to the body via aortic arch
By the end of today’s class: • How the heart is stimulated by electrical impulse • Describe the intrinsic and extrinsic regulation of heart rate • Relationship between pulmonary and systemic circulation • Blood and response to exercise
A. Heart Rate: is regulated by both intrinsic and extrinsic factors. i. Intrinsic regulation: a. Sinoatrial (S-A) node: a mass of specialized cardiac muscle located on the exterior wall of the right atrium. Initiates the electrical impulse.
b. Atrioventricular (A-V) node: receives impulse from the S-A node and delays it about .10 sec. for atrial contraction. c. A-V Bundle of His: speeds the impulse over the ventricles to the Purkinje system causing simultaneous contraction of the ventricles. Video
ii. Extrinsic Regulation: the autonomic nervous system can override the myocardial rhythm. a. Sympathetic Influence: epinephrine is released when stimulated causing heart rate to increase. b. Parasympathetic Inf: releases acetylcholine to slow heart rate.
Adrenaline • Influences heart rate • Plays a larger role in metabolic action, i.e. increasing glycogen and lipid breakdown
B. Circulation of Blood: i. Pulmonary Circulation: deoxygenated blood is pumped from the right side of the heart through the pulmonary arteries to the lungs. Oxygenated blood is returned by the pulmonary veins.
ii. Systemic Circulation: oxygen rich blood is pumped from the left side of the heart through the aorta to the rest of the body.
iii. Cardiac Output: the volume of blood pumped by the heart in one minute. Equal to stroke vol. x heart rate. a. Stroke Vol.: the volume of blood pumped by one ventricle with each beat. Approx. 70 ml. Stroke vol.=EDV-ESV
iv. Cardiovascular Drift: an increase in heart rate during steady exercise due to a reduction in stroke volume. Caused by: *exercising in heat *rise in core temp. *decrease in plasma vol.
C. Blood Pressure: the pressure exerted on the walls of the arterial system. i. Systolic pressure: – The force exerted by blood on arterial walls during ventricular contraction ii. Diastolic pressure: – The force exerted by blood on arterial walls during ventriuclar relatation
Cardiac Cycle • The cardiac cycle is the order of events making up one heartbeat. Cycle lasts for approx. 0.8 seconds and occurs approx. 72 times a minute • Cardiac cycle includes a period of relaxation, known as diastole (0.5 secs), followed by a period of contraction, known as systole (0.3 secs)
BLOOD PRESSURE • Healthy blood pressure = 120mmHg (systolic) 80mmHg (diastolic) • Low blood pressure = 90-100/50-60 • High blood pressure = 140/100
iii. Blood Pressure Response to Exercise: a. Dynamic Exercise: systolic pressure increases with intensity with relatively little change in diastolic pressure. Ex. Walking, jogging, swimming, cycling.
b. Static Exercise: heavy resistance training increases blood pressure due to muscular contractions compressing peripheral arteries. Ex. Weightlifting, isometrics
iv. Distribution of Blood Rest (cardiac output 5,000 ml) *liver = 1350 ml *kidneys = 1100 ml *muscle = 1000 ml *brain = 700 ml *skin = 300 ml *heart = 200 ml Exercise (cardiac output 25,000 ml) *liver = 500 ml *kidneys = 250 ml *muscle = 21,000 ml *brain = 900 ml *skin = 600 ml *heart = 1000 ml
v. Cardiovascular Adaptations to Exercise: a. Lower resting heart rate. b. Increased left ventricular volume. c. Increased stroke vol. and cardiac output. d. Capillarization: increase in capillary surface area in muscles. e. Greater arteriovenous oxygen diff. (a-vO2)
D. Maximal Oxygen Consumption: (VO2) refers to the maximum amt. of O2 that an individual can utilize during maximal training. *measured as ml of O2 used in one minute per Kg of body weight. (ml Kg-1 min-1)
BP Q&A • What is your blood pressure? • TO DO: green box p.41 • Explain what happens to blood flow distribution during exercise • Draw Figure 2.7 (page 42) • What is cardiac output and how is it measured? • What happens to cardiac output during exercise and why? • TO DO: green box p.43 • READ ‘To think about’ p. 43
VO2max • There are limits to how far the body can be pushed • Each person has different tolerance levels • VO2max is commonly used to measure aerobic capacity – It is the maximum rate an individual can take in and use oxygen
VO2max • Amount of air going in and out is measured as exercise intensity progressively increases • VO2max is reached when the person can no longer continue “aerobic capacity”
VO2max • VO2max quantifies the maximum rate that an individual can take in and use O2 • This value is of great interest for elite endurance athletes = aerobic capacity
FICK EQUATION Relationship bw max cardiac output, arterio- venous O2 difference & VO2max VO2max = max cardiac output X max arterio- venous O2 difference *Complete ‘To do’ p. 44
VO2max • ABSOLUTE VO2max = L.min -1 • RELATIVE VO2max = ml.kg-1.min-1 – (takes body mass into account; used for weight bearing activities) *Read p.45 text 1. Explain how gender, age and type of exercise affect VO2max 2. How does training increase VO2max?
SUMMARY • Read Theory of Knowledge box on p.48 – Can you think of at least 2 factors (geographical, physiological, training, psychosocial, economic or cultural) that East Africans have to their advantage when producing endurance athletes? • Review self-study questions p. 48-49
Cardiac SystoleAtrial Systole – SA node sends electrical impulse to the atrium walls causing the atrium to contract – Contractions force all remaining blood into the ventricles and the antrioventricular valves close Ventricular Systole – Pressure inside the ventricles pushes open the semilunar valves (Pulmonary and aortic) – Electric signal travels down the Purkinje Fibers stimulating contraction of the ventricular myocardium – Blood flows into the pulmonary (lungs) and systemic (around the body) systems.
Cardiac Diastole • During relaxation the atria fill with blood while the tricuspid and bicuspid vales are closed • Valves then are pushed open due to increase in atrial pressure and ventricles begin to fill with blood
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