Circulatory & Respiratory Systems

• From the body:

  • blood is delivered to the right atrium from the superior and inferior vena cava
  • it then passes through the tricuspid valve and enters the right ventricle
  • from there, blood is pumped through the pulmonary semilunar valve and out the pulmonary arteries to the lungs
• from the lungs:

  • blood returns from the lungs through the pulmonary veins to the left atrium
  • the blood then passes through the bicuspid (mitral) valve and enters the left ventricle
  • the blood is then pumped through the aortic semilunar valve into the aorta where it is brought to muscles and organs around the body and returns to the heart by the vena cava
• arteries:

  • carry blood away from the heart
  • in systemic circulation they carry oxygenated blood from the left side of the heart to the body
  • in pulmonary circulation they carry deoxygenated blood from the right side of the heart to the lungs
• arterioles:

  • blood vessels that branch out from arteries and lead to capillaries
  • surrounded by smooth muscle that are controlled by the nervous system and local chemical factors released by tissues supplied by the arterioles
  • can be signaled by the nervous system to contract or relax the layers of smooth muscle, so the nervous system can control distribution of blood flow
  • influenced by autoregulation: which is when locally produced chemical compounds cause arterioles to relax, increasing the delivery of blood to the working muscle
• capillaries:

  • the smallest of blood vessels (one cell can pass through at a time)
  • exchange sites of water, oxygen, carbon dioxide, and waste between blood and tissues in the body
• blood return to the heart:

  • skeletal muscle pump
  • thoracic pump
  • nervous system
  • one-way valves in veins
• skeletal muscle pump:

  • when the skeletal muscle contracts, blood is pushed/massaged back to the heart because of the one-way valves found within veins
• thoracic pump:

  • with each breath, pressure in the chest cavity is very low for a few seconds while pressure in the abdominal cavity increases, which also causes the pressure of the veins in the chest cavity to drop at the same time as the pressure of the veins in the abdominal cavity increases
  • the difference in pressure between the veins in the thoracic and abdominal cavities pushes blood from the veins in the abdominal cavity into the veins in the thoracic cavity
• nervous system in blood return to the heart:

  • at times when cardiac output needs to be increased, the nervous system sends a signal to the veins, causing them to slightly constrict (venoconstriction), which helps to return more blood to the heart
• electrocardium:

  • P wave: represents depolarization of the atria
  • QRS complex: represents depolarization of the ventricles
  • T wave: represents repolarization of the ventricles
• blood components:

  • plasma
  • blood cells: red, white, & platelets
• plasma:

  • mostly water (90%); other 10% is plasma proteins and acids, salts, etc.
• blood cells:

  • red blood cells (erythrocytes): essential in oxygen transport
  • white blood cells (leukocytes): essential to the body's immune system
  • platelets: essential in the regulation of blood clotting
• cardiovascular disease refers to any disease affecting the heart/cardiovascular system, but is usually used to refer to coronary artery/heart disease
• coronary artery/heart disease (or atherosclerosis) is when the coronary arteries in the heart get plugged up by hard deposits of cholesterol lining the blood vessel, cutting off part of the heart from getting oxygen - which can lead to heart failure
• risk factors for coronary artery/heart disease include smoking, high blood lipids, hypertension/high blood pressure, family history/genetics, and physical inactivity
• a heart attack (or a myocardial infarction) is when blood flow to a section of the heart is cut off because of plaque buildup, resulting in that section of heart muscle to die
• cardiac output (Q) is the volume of blood pumped out of the left ventricle in one minute, and is determined by multiplying stroke volume by heart rate
• stroke volume is the amount of blood pushed out of the left ventricle in a single beat, and is regulated by:

  • the amount of blood returned to the ventricle before it contracts (this amount can increase as a result of venoconstriction, the skeletal muscle & thoracic pumps, and the nervous stimulation of the heart)
  • aortic blood pressure
  • the strength of the ventricular contraction
• heart rate refers to the amount of times the heart contracts in one minute
• at rest, a typical adult's cardiac output is about 5-6 L/min, but can increase to up to 30 L/min during intense exercise
• the average heart rate of an adult with no intervention from the parasympathetic nervous system is 100 bpm
• blood pressure is the force exerted by blood against the walls of the arteries and other vascular vessels, and is written as systolic blood pressure over diastolic blood pressure: a normal blood pressure varies from 90/60 mmHg to 120/80 mmHg
• hypertension refers to prolonged high blood pressure (over 140/90 mmHg) and is a major risk factor for cardiovascular disease - it can be caused by obesity, smoking, aging, kidney disease, or by genetic factors
• during exercise, working skeletal muscle has a greater need for oxygen and the cardiovascular system alters blood distribution to increase the amount of oxygen to the muscles by limiting blood flow to less active organs, however blood flow to certain areas is constant:

  • the brain always receives 720mL
  • the heart always receives 4%
• cardiovascular effects of training include:

  1. increase in mass and dimensions of the heart
  2. increase in ventricular volume, which causes an increase in stroke volume (referred to as the Frank-Starling mechanism)
  3. increase in ventricular wall thickness, which increases the force of contraction
  4. increase in blood volume
  5. increase in amounts of red blood cells and hemoglobin
  6. increase in the amount of myoglobin, mitochondria, and enzymes needed for aerobic processes
  7. increase in a-VO2 difference
• the conductive zones is the area made up of structures that bring air from the outside of the body to the lungs:

  • mouth and nose
  • pharynx
  • larynx
  • trachea
  • bronchi
  • bronchioles
  • terminal bronchioles
• the respiratory zone is the area made up of respiratory bronchioles, alveolar ducts, and the alveolar sacs - all of which are involved in gas exchange
• areas of the brain that are important in the regulation of ventilation are the medulla oblongata and pons
• the medulla oblongata is the inspiratory and expiratory centres, and the nerves generate a rhythmic signal that is sent to the respiratory muscles, the diaphragm, and external intercostal muscles
• the two specialised respiratory centres found in the pons are call the pneumotaxic and apneustic centres, which ensure that transition from inhalation to exhalation is smooth
• oxygen transport is the process by which oxygen is absorbed in the lungs by hemoglobin and blood plasma in circulating deoxygenated red blood ells and carried to body tissues
• carbon dioxide transport is the process by which carbon dioxide in the blood is moved into the alveoli and exhaled from the body:

  • small percentage is dissolved into blood plasma
  • also can bind to hemoglobin and be released when the blood arrives in the lung (which has a higher concentration of oxygen)
  • also can be transported by the bicarbonate system
• the bicarbonate system:

  • CO2 diffuses into the red blood cells and reacts with water forming a weak acid
  • the acid dissociates into a hydrogen ion and a bicarbonate ion
  • the hydrogen ion binds to the hemoglobin and the bicarbonate diffuses into blood plasma
  • in the lungs when the pressure of CO2 is low, the process is reversed and CO2 is free to diffuse into the alveoli and be exhaled
• factors controlling the rate of diffusion include:

  • size of concentration gradient
  • thickness of barrier between two areas where diffusion occurs
  • surface area
• asthma is a disease characterized by the spasm of the smooth muscles that line the respiratory system, an oversecretion of mucus, and the swelling of the cells lining the respiratory tract
• COPD (or chronic obstructive pulmonary disorder) is a general term for a family of diseases that cause a dramatic reduction in airflow through the respiratory system
• a-VO2 difference is the difference between the amount of O2 in the arteries and the veins (this can give an idea of the amount of oxygen being delivered to the muscle)
• VO2 max refers to the maximum amount of oxygen that a person can use during intense exercise
• EPOC (or Excess Post-Exercise Oxygen Consumption) refers to the amount of oxygen the body needs after exercise to return to a resting state, and is equal to oxygen deficit