Sports Science - Chapter 2 (physiology)

principal structures of the ventilatory system

principal structures of the ventilatory system

nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles, lungs, alveoli

low resistance pathway for air flow (function of conducting airways)

the nasal and oral passageway and the trachea and bronchi provide a lower resistance pathway for airflow where no gas exchange takes place

defence against chemicals and harmful substances (function of conducting airways)

the conducting airways are lined with membranes which filter the air that passes through, protecting the body from harmful substances that are inhaled

warming and moistening of the air (function of conducting airways)

air that passes through the conducting airways is warmed and moistened

pulmonary ventilation

inflow and outflow of air between the atmosphere and the lungs (also known as breathing)

total lung capacity

volume of air in the lungs after a maximum inhalation

vital capacity

maximum volume of air that can be exhaled after a maximum inhalation

tidal volume

volume of air breathed in and out in any one breath

expiratory reserve volume

volume of air in excess of tidal volume that can be exhaled forcefully

inspiratory reserve volume

additional air over and above tidal volume

residual volume

volume of air still contained in lungs after a maximum exhalation

physics principal re the movement of air

a substance (air) moves from an area of high pressure to an area of low pressure

inhalation mechanics of breathing at rest

1. the diaphragm contracts and flattens, at the same time the intercostal muscles contract and pull the ribcage up and out

2. This creates a vacuum of air between the lungs, chest walls and the diaphragm, which increases the volume of the lungs

3. The increase in lung volume = a decrease in air pressure, which causes the air to flow from the atmosphere into the lungs

inhalation mechanics of breathing during exercise

1. the internal intercostal muscles and pectoral muscles contract to pull the ribcage further upwards and outwards in order to increase the lung volume

2. more air flows in to the lungs from the atmosphere due to a further decrease in air pressure

exhalation mechanics of breathing during rest

1. the diaphragm relaxes and recoils (into a dome shape), at the same time the external intercostal muscles relax and the ribcage moves inwards and down

2. this decreases the volume of the lungs

3. the decrease in lung volume creates an increase in air pressure, which causes the air to move back into the atmosphere

exhalation mechanics of breathing during exercise

1. the rectus abdominus muscles contract to pull the ribcage down and inwards quicker to further compress and decrease the lung volume

2. more air flows out of the lungs due to a further increase in air pressure

nervous and chemical control of ventilation during exercise

lung stretch receptors —> prevent the over-inflation of the lungs, if excessively stretched, they induce exhalation

muscle proprioceptors —> detects an increase in movement, therefore increasing the rate and depth of ventilation

chemoreceptors —> detects an increase in blood acidity (low pH) due to a high carbon dioxide content in the blood, sending nerve impulses to the respiratory muscles, increasing ventilation

haemoglobin and oxygen transportation

98.5% of oxygen in the blood is transported by haemoglobin.

haemoglobin is a protein that allows oxygen to bind to a red blood cell, it contains a central iron ion which can hold up to 4 oxygen atoms per heme.

when binded with oxygen, oxyhaemoglobin is formed

the oxygen atoms are then diffused into the tissues once they reach their target, while diffusing they also pick up CO2 and return it back to the lungs to be exhaled into the atmosphere.

structure of alveoli

• walls are very thin (only 1 cell thick)

• large surface area, allowing for a greater uptake of oxygen

• supplied by a dense capillary network

the process of gaseous exchange in the alveoli

gaseous exchange takes part in the alveoli, which are attached to the branches of the bronchial passages

gases move from area of high partial pressures to low partial pressures

oxygen diffuses from the alveoli (high partial pressure) to the bloodstream (low partial pressure),

CO2 diffuses from the bloodstream (high partial pressure) into the alveoli (low partial pressure)

the process is constant to provide an ongoing supply of energy to active muscles

composition of blood

blood is composed of cells (erythrocytes, leukocytes and platelets) and plasma, also the transport vehicle for electrolytes, proteins, gases, nutrients, waste products and hormones.

erythrocytes

• makes up 40-45% of blood volume

• contains an oxygen-carrying pigment called haemoglobin, which gives oxygen its red colour and aids in oxygen transport around the body

leucocytes

• <1% of blood volume

• primarily involved in immune function and protecting the body from infection

platelets

• <1% of blood volume

• assists in the process of repair following an injury

heart blood flow order

1. superior vena cava

2. right atrium

3. tricuspid valve

4. right ventricle

5. pulmonary valve

6. pulmonary artery

7. lungs (deoxygenated blood gets oxygenated)

8. pulmonary veins

9. left atrium

10. bicuspid valve

11. left ventricle

12. aorta

autonomic nervous system

• responsible for control of involuntary bodily functions

• comprises of the sympathetic and parasympathetic nervous system

sympathetic system —> stimulates the heart to beat faster

parasympathetic system —> stimulates the heart to return to its resting state

describe the intrinsic and extrinsic regulation of heart rate

Sympathetic nervous system:

during exercise, 3 receptors are stimulated; proprioceptors, baroreceptors, chemoreceptors. these receptors send impulses (action potentials) to the cardiac control centre (medulla oblongata) which then sends an impulse through the sympathetic nervous system to stimulate the SA node of the heart where the HR increases.

Parasympathetic nervous system:

when exercise stops, the receptors pick up decreases in co2 levels, blood pressure and muscle movement, so impulses are sent to the cardiac control centre, and an impulse is sent to the parasympathetic nervous system which stimulates the SA node and heart rate decreases.

Stress hormones (adrenaline and noradrenaline) are released in adrenal glands and also stimulate the SA node, increasing heart rate

sequence of excitation of the heart

1. impulse is generated in the sino-atrial node (SA)

2. Impulse spreads to the walls of the atria

3. atria contracts, sending the blood to the ventricles

4. impulse passes through the atrio-ventricular node

5. impulse moves into the bundle of His

6. the bundle of His branches into Purkynje fibres

7. the impulse spreads into the walls of the ventricle, and the ventricle contracts

pulmonary circulation

delivers deoxygenated blood from the right side of the heart to the lungs for oxygenation and then back up to the left side of the heart

systemic circulation

delivers the oxygenated blood from the left side of the heart to the other tissues of the body where oxygen is used up, then delivers the deoxygenated blood back up to the heart

stroke volume

the volume of blood pumped out of the left ventricle of the heart during systolic contraction

during exercise it increases, depending on how you exercise (increases more during aerobic exercise because more blood is needed to be pumped around the body)

during an upright physical activity like jogging, stroke volume increases from about 50 mL to at rest to about 120 mL at maximal exercise intensity

the fitter you are, the greater your stroke volume will be because the heart pumps more efficiently

cardiac output

the quantity of blood being pumped out of the heart

cardiac output = stroke volume x heart rate

explain cardiovascular drift

• occurs during submaximal exercise in a hot environment

• a gradual rise in heart rate when exercise is performed at a constant work rate at a constant state over a prolonged period

• compensatory increase in heart rate to maintain a constant cardiac output (because stroke volume decreases)

• there is a rise in core temperature causing a redistribution of blood to the skin to release excess heat which causes a lower venous return to the heart and also a small decrease in blood volume from sweating. Therefore, there is a decrease in stroke volume, so the heart rate must increase in order to maintain cardiac output.

• blood viscosity also increases (making it more difficult to return back to the heart)

• dehydration speeds up this process

cardiac output, stroke volume and heart rate in different populations at rest

• men have a higher stroke volume than women because their hearts are bigger, and therefore they have a lower resting heart rate, but their cardiac output at rest is slightly higher

• younger people have a greater stroke volume than older people, but a similar heart rate, young people have a higher cardiac output at rest

cardiac output, stroke volume and heart rate in different populations at rest

• trained people have a higher stroke volume than untrained people as their hearts have undergone hypertrophy as a result of endurance training, and therefore have a lower resting heart rate to achieve an equal cardiac output at rest

• during exercise young people have a higher maximum heart rate and stroke volume and can achieve a greater cardiac output

systolic blood pressure

the force exerted by blood on arterial walls during ventricular contraction

diastolic blood pressure

the force exerted by blood on arterial walls during ventricular relaxation

systolic and diastolic blood pressure during rest and exercise

at rest, a heavier, unhealthier individual will have a greater diastolic and systolic blood pressure than a healthy individual.

dynamic exercise

• the systolic pressure increases at a lower rate than static exercise because the breathing frequency is much higher and therefore the pressure is lower

• the diastolic pressure remains the same because the muscles are moving constantly, so there is no added pressure on constant contraction and arteries are dilated as vasodilation is occuring

static exercise

• diastolic pressure significantly increases because the pressure on the arterial walls is increased, even during relaxation and because breathing is more constricted (less oxygen) so the heart must work harder to pump the blood it has to supply the muscles with enough oxygen to continue the static exercise

• systolic pressure significantly increases because there is an increase in the volume of blood and contraction rate

the distribution of blood at rest and redistribution of blood during exercise

blood pressure must be maintained at the correct level so that there is sufficient blood flow around the body

the body regulates blood pressure by restricting and/or allowing more blood to flow to areas of the body to maintain cardiovascular function - this is done by altering the diameter of the arteries, arterioles and the opening/closing of capillaries

during exercise:

1. the muscles being used have a higher demand for blood flow

2. the cardiac output increases (both HR and stroke volume increase), but in addition more blood is directed to the muscles

3. the arterioles supplying the muscles dilate, opening more of the capillary network within the muscle

4. to prevent a drop in blood pressure, arterioles constrict and pre-capillary sphincters close to other organs in the body e.g., liver and kidneys

cardiovascular adaptations occurring from endurance training

resting heart rate

• as the stroke volume increases, to maintain the cardiac output, the resting heart rate decreases

stroke volume

• the increase in the size of the heart enables the left ventricle to stretch more and therefore be filled with more blood

• the increase in muscle wall thickness also increases the contractibility, resulting in increased stroke volume at rest and during exercise, increasing blood supply to the body

cardiac output

• the cardiac output increases significantly during maximal exercise because of an increased stroke volume

• this results in a greater oxygen supply, waste removal and hence improved endurance performance

explain maximal oxygen consumption

• the maximum volume of oxygen you can consume while exercising at your maximum capacity

• maximum amount of oxygen in mililiters one can use in one minute per kilogram of bodyweight

• trained individuals have higher vo2 max values and can exercise more intensely than those who are untrained

• you can increase your vo2 max by exercising aerobically consistently and more intensely

vo2 max in different groups

children have a lower absolute vo2 max than adults, as they are smaller in size, however have a similar relative vo2 max

trained athletes can use oxygen more efficiently, and therefore have a higher vo2 max

men have a greater percentage of lean body weight, and therefore more of their body weight is capable of using oxygen, and therefore men have a higher vo2 max than women

vo2 max in different sports

modes of exercise which utilise more muscles have a higher oxygen consumption e.g., running utilises the legs, which is a bigger muscle than the arms, so will utilise more oxygen than a bicep curl

generally exercise which utilises both the arms and the legs (e.g., XC skiing) have the highest oxygen consumption

swimmers consume less oxygen due to being in the prone position and the water bearing the body’s weight