A.1.3 Transport

Adapted from class notes.

The Respiratory System: Overview

• For mainly the transport of O2 used in exercise

• Mostly involuntary, but you can control it when necessary

• Key Concept: Passive movement from high concentration to low concentration

• Inhalation:The diaphragm made contact and flattens, increasing the volume of lungs, and lowers the pressure inside

• Exhalation: The diaphragm muscle releases and returns to a dome-like shape, decreasing the volume of the lung, and increasing the pressure inside the lungs

Muscles of the Respiratory System

• During rest, the diaphragm is enough to account for the required respiration rate

• During exercise, breathing rate needs to increase as well as be more forceful

  • Breathing gets additional help from intercostal muscles

  • Internal intercostal muscles work to reduce chest cavity volume (exhale)

  • External intercostal muscles work to increase chest cavity volume (inhale)

The Respiratory System: Air Flow

• Air flows in the nasal cavity, then the pharynx (throat, then larynx (vocal chords), trachea (wind pipe), bronchis (major branches), diaphragm below lungs)

• The purposes of each of these is to warm, moisten, and filter air. No gas exchange

The Respiratory System: Gas Exchange

• Gas exchange happens in the atveoli

• Small sacs for large surface area to volume ratio and are attached to capillaries

• Inspired air has lots of O2, little CO2

• Oxygen diffuses into the blood (high concentration in alveoli, low in blood)

• CO2 diffuses out of blood (high concentration in blood, low in alveoli)

• Expired air has less O2, more CO2

• Differences between blood O2/CO2 and inspired O2/CO2 increase with exercise

The Respiratory System: Lung Volume

• You don’t use your entire lung volume with every breath

• Normal breaths are called “Tidal Volume”

• Big inhales to maximum capacity are “inspiratory reserve volume”

• Big exhales are “expiratory reserve volume”

• The air left over after your maximum exhale is “residual volume”

• Vital capacity is the IRV + ERV + TV

• Total lung capacity is VC + RV

• Minute ventilation is the volume of air exhaled per minute (tidal volume times breaths per minute)

• Average lung size at 25 is about 5.5 L (~200mL at birth)

• Typically, men ahve larger lungs than females

• Vital capacity increases with height

• Hyperventilation quickly reduces arterial CO2 levels, causing a reduced stimulus to breathe

• Rebreathing (into a paper bag for panic attacks) and breath holding both work off arterial CO2

The Cardiovascular System: Blood

• Blood functions to transport gases, nutrients, watse, hormones, and heat

• Blood volumes total around 5L in a 70kg person (154lbs)

• Made up of:

  • Plasma - 55% of blood volume. Water and nutrients

  • Platelets - <1% of blood volume. Repair and clotting

  • White blood cells - <1% of blood volume. Immune function. Called leucocytes

  • Red blood cells - 40-45% of blood volume. oxygen and CO2 transport. Called hematocrit

  • CO2 mainly travels in the form of bicarbonate (HCO2)

  • Oxygen mainly transported through attachment to haemoglobin of RBC

  • Erythropoletin (EPO) stimulates the bone marrow to produce RBC

  • Blood doping involves using someone’s own blood to increase RBC concentration

  • Synthetic EPO can also be used to illegally produce more RBC/haemoglobin

The Cardiovascular System: Structure

• Arteries: Carry blood AWAY from the heart

  • Usually carry oxygenated blood to the body

  • The pulmonary artery carries deoxygenated blood to the lungs

  • Usually higher pressure and thick muscular walls

• Veins: Carry blood TOWARD the heart

  • Usually carry deoxygenated blood to the heart

  • The pulmonary vein carries oxygenated blood from the lungs back to the heart

  • Lower pressure and contain valves to prevent backward flow

• Capillaries: Connect arteries to veins

  • This is where gas exchange happens (diffusion from high to low concentration)

  • Around the body, O2 leaves the blood and CO2 enters

  • In the lungs, CO2 leaves and O2 enters

• Systematic Circulation - For oxygenation of the body

• Pulmonary Circulation - For oxygenation of the blood

The Cardiovascular System: The Heart

• The heart has four chambers:

  • Two atria on top where blood collects

    • The right atria collects blood from the body

    • The left atria collects blood from the lungs

  • Two ventricles on the bottom where blood pumps out

    • The right ventricle pumps blood to the lungs

    • The left ventricles pumps blood to the body

• The vena cava are the large veins that return blood to the heart from the body

• The aorta sends oxygenated blood to systematic circulation

• Valves exist between atria and ventricles, and ventricles and artery:

  • Tricuspid - between right A and V

  • Mitral - between left A and V

  • Pulmonary - between right V and pulmonary artery

  • Aortic - between left V and aorta

• The heart is primarily made up of cardiac muscle tissue

• This muscle contracting is how blood is pumped from chamber to chamber, and chamber to system

• Typically, people who do cardiovascular exercise experience cardiac hypertrophy

  • Hypertrophy is muscle growth

  • The right ventricle pumps blood to the lungs, right next to the heart

  • The left ventricle is responsible for pumping blood to the whole body

  • Hypetrophy of the heart typically is increased muscle in the left ventricle to make circulation to the body easier

The Cardiovascular System: Blood Pressure

• Blood pressure is the force that the blood exerts on the blood vessels

• This force is different depending on atrtery (higher, measured) or vein (low)

• Pressure changes depending on if the heart is contracting or relaxing

• The contracting phase is called systole, and is higher pressure

  • Healthy resting systolic blood pressure is 90-120 mmHg

• The relaxing phase is called diastole, lower pressure

  • Healthy restin diastolic blood pressire is 60-80 mmHg

The Caridovascular System: Blood Distribution

• During exercise, the distribution of the blood supply in the body changes

• Smooth muscles surrounding arteries constrict or relax to change how much blood can flow

• Overall blood flow increases through heart rate and stroke volume

• Majority of increase in blood flow goes to muscles

• Many other organs decrease in blood flow

• Muscle goes from about 20% of the blood flow to about 84% during exercise

• Kidneys in liver decrease in both percentage (from about 50% to <5%) and overall blood volume

• Blood sent to tissue of the heart increases in volume, but roughly same percentage

• The brain recieves more blood, but lower percentage

The Cardiovascular System: Acute Responses to Exercise

• Cardiax outpit is the total volume (L) in blood pumped from the left ventricle per minute

• Cardiac Output = (heart rate (bpm) times stroke volume (mL))/1000

• Stroke volume is the blood pumped by the left ventricle (systematic) for every beat of the heart

• During exercise, stroke volume increases as the heart pumps more forcefully

• Heart rate also increases during exercise

• Cardiac output can increase by around 5x during exercise

• Fitness level affects CO:

  • More trained individuals have higher stroke volume

  • This allows for lower heart rate to have equal CO

  • Trained individuals are then able to have greater CO while maintaining a lower heart rate

• Cardiovascular Drift:

  • During sustained/prolonged exercise

  • CO must remain the same

  • Due to icnrease in temperature/sweating, stroke volume decreases

  • Heart rate must increase to maintain CO

The Cardiovascular System: VO2 Max

• VO2 max = the maximum rate O2 can be brought in and used

• VO2 is measured by gas concentrations of inhale/exhale

  • Increases during exercise

  • The highest this gets to si the VO2 max

• Higher VO2 max relates to highly trained athletes

• VO2 Max Equation: 15.3 times (max heart rate/resting heart rate)

• A-VO2diff measures the concentration of oxygen in arteries compared to veins. Higher means more O2 used