Essentials of Living World: Circulation & Respiration

Circulation and Respiration

•  Learning changes everything.
•  Essentials of the Living World, Seventh Edition is the textbook.
•  The textbook authors are George Johnson and Joel Bergh.
•  Unicellular protists obtain oxygen and nutrients directly through simple diffusion.
•  Cnidarians and flatworms have cells directly exposed to the environment or gastrovascular cavity.
•  Large animals have tissues that are multiple layers thick, making surface exchange difficult.
•  Circulatory systems transport oxygen and nutrients from the environment and digestive cavity to body cells.
•  Two types of circulatory systems exist: open and closed.

Open Circulatory Systems

•  No distinction between circulating fluid (blood) and extracellular fluid.
•  The fluid is called hemolymph.
•  Insects have a muscular tube (heart) that pumps hemolymph through open-ended channels.

Closed Circulatory Systems

•  Circulating fluid (blood) is always contained within blood vessels.
•  Annelids (like earthworms) and all vertebrates have a closed circulatory system.
•  Blood flows away from the heart in arteries.
•  Gases and nutrients exchange through thin-walled capillaries.
•  Blood returns to the heart via veins.

Circulatory System Functions

•  Transportation of gases, nutrients, waste, and hormones.
•  Regulation of body temperature (e.g., countercurrent heat exchange in vertebrates).
•  Protection against injury and foreign microbes/toxins.

Vertebrate Circulatory System Architecture

•  Consists of a heart, blood vessels, and blood.
•  Blood travels from the heart through arteries, then arterioles, then capillaries for exchange, then venules, and finally back to the heart in veins.
•  Capillaries have a large total cross-sectional area, allowing efficient exchange.
•  Capillary beds can open and close based on tissue needs.

Artery Structure

•  Arteries are more than simple pipes, needing to expand with heart pressure.
•  Walls have three layers: innermost endothelial cells, middle elastic fibers and smooth muscle, and outermost connective tissue.

Capillary Structure

•  Capillaries are narrow with thin walls for exchange.
•  Almost all body cells are close to a capillary.
•  Blood pressure is lower in capillaries than in arteries.

Vein Structure

•  Vein walls are thinner than artery walls due to lower pressure.
•  Veins have unidirectional valves that prevent backflow.

Blood Plasma Composition

•  Blood plasma is a water solution with three dissolved substances: - Metabolites / wastes (e.g., glucose, vitamins, hormones). - Salts / ions (e.g., sodium, chloride, bicarbonate). - Proteins (help maintain water balance; include serum albumin, antibodies, globulins, and fibrinogen - important for clotting).

Cellular Components of Blood

•  Nearly half of blood volume is comprised of cells. - Red blood cells (carry oxygen using hemoglobin). - Hematocrit: The fraction of blood volume occupied by red blood cells (usually about 45% in humans). - White blood cells (part of the immune system). - Platelets (involved in blood clotting).

•  Red blood cells are flat disks with a central depression and are packed with hemoglobin.

•  White blood cells lack hemoglobin.

•  Platelets are cell fragments with a role in clotting.

Human Circulatory System

•  Humans and other mammals have a four-chambered heart with two pumping circuits.
•  One side pumps blood to the lungs for oxygen pickup, and the other side sends oxygenated blood to the body.
•  The heart cycle involves the atria and ventricles; valves regulate blood flow.
•  Oxygen-rich blood returns to the heart via pulmonary veins to the left atrium, then left ventricle and out to the body.
•  Deoxygenated blood goes from the body through the vena cavae to the right atrium, then right ventricle, then to the lungs via pulmonary arteries.

Heart Sounds

•  "Lub-dub" sounds are caused by valve closure during the heartbeat cycle.
•  A heart murmur indicates incomplete valve closure.

Blood Pressure Measurement

- Sphygmomanometer is used to measure blood pressure.

•  Systolic pressure is the peak pressure during ventricular contraction.
•  Diastolic pressure is the lowest pressure during atrial filling.

Heart Contraction

•  The heart's contraction is a coordinated process. - The SA node is the heart's pacemaker, initiating the rhythm and atria contraction. - The AV node delays the signal to the ventricles, allowing for the complete atrial contraction.
  - The impulse passes down to a bundle of His, and then to Purkinje fibers, causing the ventricles to contract almost simultaneously.
•  ECG (electrocardiogram) measures electrical signals during the heart cycle.

Respiratory Systems

•  Respiration involves oxygen uptake and carbon dioxide release.
•  Most primitive animals obtain O2 through direct diffusion from the environment.
•  More advanced animals have specialized respiratory organs such as gills, tracheae, and lungs; which improve the efficiency of respiration.

Human Respiratory System

•  Lungs are terrestrial adaptations.
•  A pair of lungs resides in the thoracic cavity.
•  Air enters through the nasal cavity, pharynx, larynx (voice box), trachea, bronchi, bronchioles, and then into alveoli (for gas exchange with blood).
•  The diaphragm and rib muscles drive breathing (inhalation and exhalation).
•  Negative pressure draws air into the lungs during inhalation, and pressure increases during exhalation.

Respiration (Gas Exchange)

•  Oxygen is transported by hemoglobin in the blood.
•  Hemoglobin carries O₂ in the lungs, and releases it in tissues under high CO2 levels.
•  CO2 is transported in the blood in several ways.