Chapter 8 - The Heart and Lungs at Work

3 layers of tissue of the heart

• endocardium - innermost layer of smooth muscle

  • lines the chambers of the heart and allows blood to flow smoothly

• myocardium - thick and muscular middle layer

  • pumps the blood

• epicardium - thin outer layer

  • protects the heart

Pericardium

protective sac outside of the epicardium that loosely surrounds the entire heart

• allows it to expand and contract freely

chambers of the heart

• right ventricle

• pulmonary artery

• left ventricle

• aorta

• atria

• right atrium

• superior vena cava

• inferior vena cava

• left atrium

• pulmonary vein

ventricles of the heart ( + aorta and pulmonary artery)

• right ventricle - pumps deoxygenated blood to the lungs via the pulmonary artery

• pulmonary artery - only artery in the body that carries deoxygenated blood

• left ventricle - pumps deoxygenated blood to the rest of the body through the aorta

  • stronger than the right ventricle because its larger and muscle walls are stronger

• aorta - largest artery in the human body

atrium of the heart ( + superior and inferior vena cava AND pulmonary vein)

• atria (plural: atrium) - two small chambers that pump blood into ventricles to be distributed to the lungs and other parts of body

• right atrium - deoxygenated blood from peripheral organs and tissues enters here through two large veins:

  • superior vena cava (from upper part of body)

  • inferior vena cava (from lower part of body)

• left atrium - where blood passes through (via pulmonary vein) after being oxygenated

• pulmonary vein - only vein in the body that carries oxygenated blood

valves of the heart

• semilunar valves (2 of them) - allow blood to flow into the arteries during ventricular contraction

• prevent backflow during ventricular relaxation

• pulmonary valve - regulates blood flow from right ventricle into the pulmonary artery

• aortic valve - controls blood flow from left ventricle into aorta

• atrioventricular valves (2 of them) - regulate blood flow between atria and ventricles and NOT in opposite direction

  • tricuspid valve - allows blood to flow from right atrium into right ventricle

  • bicuspid valve (mitral valve) - allows blood flow from left atrium into left ventricle

Sinus node

small bundle of nerve fibres

• generates electrical impulse (action potential) which controls beating of the heart

action potential

the electrical charge that causes muscle walls of heart to contract

2 components of blood pressure

• systole - pressure in the ventricles when they contract and push blood into the body

  • contraction phase

• diastole - pressure in the heart ventricles are relaxed and filled with blood

  • relaxation phase

Systolic pressure vs. Diastolic pressure

• systolic pressure - provides estimate of how hard the heart is working and the strain against the arterial walls during contraction

  • normal systolic pressure = 120mm Hg in healthy young adults

• diastolic pressure - indicator of peripheral blood pressure (blood pressure of body outside of the heart)

  • normal diastolic pressure = 70-80mm Hg in healthy young adults

Hypertension (high blood pressure)

increases risk of heart disease and stroke

• AKA the silent killer

  • shows no early warning signs or symptoms

how to measure heart rate easily

feel the carotid or radial pulses with your middle 3 fingers

• carotid pulse is in between trachea and sternocleidomastoid muscle in the neck

• heart rate = (number of beats in 10 seconds) x 6

arteries, arterioles, and capillaries

• arteries - carry blood away from heart into smaller and smaller vessels called arterioles

  • don’t have valves

• arterioles - branch into smaller and smaller vessels until they are made up of vessels that are one red blood cell thick (they are capillaries now)

• capillaries - small vessels composed of endothelial cells

  • allow for exchange of oxygen and nutrients from the blood to muscles and organs

  • allow blood to pick up waste products and carbon dioxide from metabolism

venules

larger vessels formed from capillaries connecting

veins

larger vessels formed from venules merging

• facilitate the return of blood to the heart (sometimes against the pull of gravity)

• have valves

• valves - open with the flow of blood in the direction of return to the heart

  • close to prevent blood flow in the opposite direction

Components of blood

• plasma - fluid that acts as transport medium for platelets, white blood cells, and red blood cells

• platelets (thrombocytes) - form clots

• white blood cells (leukocytes) - fight infection

• red blood cells (erythrocytes) - carry oxygen

  • most abundant cell in the blood (45% of blood volume)

hematocrit

percentage of blood that is made up of blood cells

hemoglobin

special oxygen-binding substance

• allows red blood cells to carry oxygen from lungs to the tissues and carbon dioxide from the body back to the lungs

reticulocytes

new red blood cells

carbaminohemoglobin

compound formed from binding of carbon dioxide and hemoglobin

Haldane effect

• higher concentration of oxygen in the lungs promotes release of CO2 from hemoglobin

carbonic anhydrase

enzyme that helps CO2 combine with water to form carbonic acid

chloride shift

• when carbonic acid dissociates into hydrogen ion and bicarbonate, the hydrogen ion is buffered by hemoglobin

• bicarbonate ion diffuses from red blood cells since in exchange for a chloride ion

• chloride shift helps maintain ionic equilibrium in the peripheral tissues and is reversed in the lungs

How do Cardiac Output and Hematocrit affect VO2max

• cardiac output determines amount of blood delivered to the body

  • changes to cardiac output will affect how effective blood carries oxygen to tissues

• hematocrit can alter oxygen uptake by increasing or decreasing amount of oxygen supplied to working tissues

Capillarization (and how it affects VO2max)

capillarization - number of capillaries in tissue

• increase capillarization can affect ability of circulatory system to replace red blood cells close to tissues that are using oxygen

  • this increases ability of those tissues to extract oxygen due to shorter diffusion distance

Components of Respiration Zone

• ALVEOLI - tiny air sacs where gas exchange occurs

  • clustered in bunches like grapes that open into ALVEOLAR DUCT

  • ALVEOLAR SAC - cluster of alveoli

Ventilation

involves movement of air into (inspiration) and out of (expiration) the lungs

which muscles help change size of thoracic cavity (which allows us to inhale and exhale)

diaphragm and intercostal muscles

inspiration

thoracic cavity expands via muscle contractions

• causes air pressure inside to be lowered which forces a flow of air into the lungs

expiration

thoracic cavity shrinks via muscle relaxation

• increased pressure inside causes air contained in lungs to flow out

gas exchange

• gas exchange between air and blood in lungs happens at the alveoli

• occurs by gas diffusion

gas diffusion in gas exchange

oxygen from atmosphere (oxygen rich) diffuses through alveolar membrane into pulmonary capillaries (oxygen poor) carrying deoxygenated blood

• CO2 diffuses in opposite direction

  • from pulmonary blood (CO2-rich) into the alveoli (CO2-poor)

erythropoiesis

formation of new red blood cells

• increases total blood volume when stimulated

effects of exercise on Cardiorespiratory system

• Cardiac output - endurance training increases heart size due to larger atria and ventricles, which means greater volume of blood being pumped

• capillary supply - increased capillarization means greater surface area and reduced distance between blood and surrounding tissues

  • increases diffusion capacity of O2 and CO2

• blood volume - training increases total blood volume through stimulation of erythropoiesis in bone marrow

• ventilation - breathing becomes more deeper and rapid during dynamic exercise

why is hyperventilating sometimes bad

• increases normal CO2 amount which changes pH balance, influencing other physiological systems

• acute mountain sickness (AMS) can occur

exercising in the heat

in humid conditions, more difficult for sweat to evaporate causing heat to be stored in the body

• core temp increases as a result

• increases risk of developing hyperthermia or heat stroke

exercising in the cold

harder for body to adapt physiologically to cold than to heat

• body responds with vasoconstriction of skin and skeletal muscle circulation

  • results in reduced blood flow to periphery and subsequent transfer of heat to the core

• can result in hypothermia