BIOLOGY - CLUTCH CH.42 - CIRCULATORY...

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BIOLOGY - CLUTCH

CH.42 - CIRCULATORY SYSTEM

CONCEPT: GAS EXCHANGE AND CIRCULATION ● Respiratory system – draws in gases from the environment, intakes O2 and outputs CO2 ● Circulatory system – transports O2, CO2, nutrients, hormones, and blood cells □ Delivers O2 to cells for cellular respiration, and removes waste CO2 ● Ventilation – movement of air, or water, through organs of gas exchange, like lungs or gills ● Gas exchange – diffusion of O2 and CO2 at respiratory tissue surface ● Circulation – transport of diffused gases throughout the body ● Cellular respiration – O2 is final electron acceptor of ETC, and CO2 is byproduct of glycolysis and citric acid cycle EXAMPLE:

● Pulmonary circulation – carries deoxygenated blood from the heart to the lungs, and oxygenated blood to the heart □ Deoxygenated blood carrying CO2 from tissues is moved from the heart to the lungs □ Waste CO2 diffuses into the lungs, where it is exhaled □ Inhaled O2 diffuses into the blood, and the oxygenated blood return to the heart ● Systemic circulation – oxygen-rich blood moves through arteries to tissues throughout the body □ O2 diffuses into cells, to be used in the mitochondrial matrix □ Delivers nutrients and carries away waste from tissues □ Deoxygenated blood carrying CO2 returns to the heart from the tissues

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CONCEPT: VASCULATURE ● Endothelium – epithelial tissue that lines the interior surface of blood vessels and lymphatic vessels ● Arteries – transport blood away from the heart, oxygenated in systemic loop, deoxygenated in pulmonary loop - Have elastic walls, and are wrapped in smooth muscle allowing them to change their diameter

- Arterioles – small arteries that branch off by capillary beds, have smooth muscle, and smaller diameter ● Veins – transport blood to the heart, deoxygenated in systemic loop, oxygenated in pulmonary loop - Have less smooth muscle than arteries, but many veins run through skeletal muscles - Contain valves to prevent backflow of blood, since pressure is lower than in arteries - Veinules – converge to form veins, formed from capillaries converging ● Capillaries – tiny vessels with walls only one-cell thick with a diameter roughly equivalent to that of a red blood cell □ Only site of exchange between blood and tissues, endothelial tissue with no smooth muscle □ Capillary beds – diffuse networks of capillaries running through tissues - Pre-capillary sphincters – control blood flow to specific capillary beds EXAMPLE:

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CONCEPT: HEART ANATOMY ● Heart – muscular organ that contracts to generate pressure waves that push blood through blood vessels

□ Atria – receive blood from veins □ Ventricles – receive blood from atria, and pump blood into arteries □ Atrioventricular valves – prevent backflow from ventricle to atrium, tricuspid valve on right, mitral valve on left □ Semilunar valves – prevent backflow from arteries to ventricles, pulmonary valve on right, aortic valve on left

- Heart murmur – blood moves back across a valve, often due to damage or infection in valve ● Pulmonary artery – delivers deoxygenated blood from the heart to the capillary beds in the lungs ● Pulmonary veins – delivers oxygenated blood from the lungs back to the heart ● Aorta – delivers oxygenated blood from the heart to the tissues ● Venae cavae (superior and inferior) – delivers deoxygenated blood to the heart from capillary beds in the bodies tissues EXAMPLE:

● Pulmonary circulation – right atrium à right ventricle à pulmonary artery à lungs à pulmonary vein à left atrium □ Oxygenates the bloods in capillary beds at the alveoli of the lungs, gets rid of waste CO2 ● Systemic circulation – left atrium à left ventricle à aorta à body tissues à venae cavae à right atrium

□ Delivers O2 to tissues via capillary beds throughout the body, and picks up waste CO2

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CONCEPT: LUNG ANATOMY ● Pharynx – throat area behind the mouth, shared passage way for air, food, and water ● Trachea – brings air from pharynx to lungs, supported by c-shaped cartilage rings □ Larynx – beginning of the trachea, contains the vocal folds

□ Primary bronchi – first branches into the lungs ● Bronchi – branches from the primary bronchi that diffuse through the lungs, supported by cartilage □ Bronchioles – smallest branches of the bronchi, supported by smooth muscle ● Lungs – organs of respiration that inhale air to absorb O2, and exhale waste CO2 from cellular respiration

□ Alveoli – grape-like ends of the smallest bronchioles where gas exchange occurs between air and blood - Thin, aqueous interface between air and surrounding capillary bed - Surfactant – mix of phospholipids and proteins produced by some alveoli to reduce surface tension

● Diaphragm – sheet of muscle that separates thoracic (chest) and abdominal (belly) cavities EXAMPLE:

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CONCEPT: BLOOD COMPOSITION ● Blood – fluid that flows through blood vessels, transports nutrients and wastes, and performs gas exchange with tissues ● Plasma – special extracellular matrix that composes the liquid part of blood □ Made of water, electrolytes, organic compounds, and dissolved gases ● Platelets – small cell fragments that are involved in the blood clotting wound response □ Rapidly plug holes, while other factors are recruited to help seal the wound site □ Thrombus – clot that forms in a blood vessel blocking blood flow ● White blood cells (leukocytes) – immune system cells that help identify and fight infections ● Red blood cells (erythrocytes) – carry O2 from the lungs via hemoglobin, lack nuclei and organelles at maturity □ Erythropoietin – hormone secreted by the kidney to stimulate RBC production in bone marrow EXAMPLE: ● Respiratory pigments – molecules that increase the oxygen-carrying capacity of blood, change color from O2 binding

□ Hemoglobin – protein made of 4 polypeptide subunits that contain hemes to bind oxygen - Heme – iron-containing cofactor with porphyrin ring that is reduced/oxidized to transport O2 in RBCs

□ Myoglobin – primary pigment of skeletal muscles, contains only 1 heme, binds O2 tighter than hemoglobin ● Sickle-cell disease – abnormal form of hemoglobin aggregates in RBCs, distorting shape, and inhibiting functions EXAMPLE:

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CONCEPT: LYMPHATIC SYSTEM ● Lymphatic system – network of lymphatic vessels that carry lymph toward the heart

□ Drains plasma from interstitial fluid, and plays important role in the immune system □ Lymph – clear fluid that circulates through lymphatic system, forms when interstitial fluid enters lymphatic ducts □ Lymph nodes – organs of the lymphatic system that are critical to immune function

□ Spleen and thymus important organs of lymphatic system

EXAMPLE:

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CONCEPT: HEART PHYSIOLOGY ● Heart circulates blood by filling it’s chambers up from veins, then pushing the blood through arteries

□ Atria – thinner, less muscular walls than ventricles that receive blood from veins □ Ventricles – thicker, more muscular walls that atria for powerful pumping into arteries

EXAMPLE: ● Cardiac cycle – complete cycle of pumping out blood, and filling up with blood

□ Systole – contraction phase of the cardiac cycle □ Diastole – relaxation phase of the cardiac cycle □ Atria and ventricles in diastole – blood flows into atria and ventricles □ Atria in systole, ventricles in diastole – blood in atria pushed into through AV valves ventricles □ Atria in diastole, ventricles in systole – blood in ventricles pushed into arteries through semilunar valves

EXAMPLE:

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CONCEPT: HEART PHYSIOLOGY ● Heart beats in response to electrical signals call action potentials □ Action potentials are generated by the movement of ions across the membrane □ Action potentials in the heart move between cells through gap junctions

□ Intercalated discs – special structure in heart muscle connecting neighboring cells, contains gap junction EXAMPLE: ● Sinoatrial node (SAN) – group of cells in the right atrium that initiate heart contraction in vertebrates □ Pacemaker cells – cells in SAN node that control rate and timing of heartbeat by starting action potentials ● Atrioventricular node (AVN) – group of cells that pass the action potential from the atria to the ventricles

□ Slightly delays the signal to give the atria time to empty completely into ventricles ● Purkinje fibers – spread action potential through ventricles from the bottom to the top ● Electrocardiogram (EKG) – records the electrical activity of the cardiac cycle EXAMPLE:

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CONCEPT: HEART PHYSIOLOGY ● Diastole – relaxation of ventricles and atria fills heart with blood □ SAN initiates atrial systole, causing the atria to contract

□ AVN delays action potential, allowing atria to completely empty into ventricles ● Systole – action potential starts at the bottom of the ventricles, and moves up through Purkinje fibers □ Ventricles contract and push blood through arteries ● Cardiac output – volume of blood per minute that is pumped by the ventricles

□ Heart rate – heartbeats per minute □ Stroke volume – volume of blood pumped by a single ventricle contraction

EXAMPLE:

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CONCEPT: HEART PHYSIOLOGY ● Systolic blood pressure – highest blood pressure, measured at the peak blood pumping out of the ventricles □ Pulse – rhythmic bulging of an artery with heartbeat allowing systolic blood pressure to be measured ● Diastolic blood pressure – lower blood pressure measured right before ventricles contract and pump out blood □ Doctors give two numbers for blood pressure measurement: systolic bp/diastolic bp ● Hypertension – long-term, abnormally high blood pressure EXAMPLE: ● Arteries have muscle fibers and elastic fibers to deal with the high pressure from ventricle contractions □ Aorta is especially dense with elastic fibers allowing it to withstand immense systolic pressure ● Blood slows as it moves through capillaries, experiencing a substantial drop in velocity and pressure ● Veins have the lowest blood pressure, have valves to prevent backflow □ Veins in extremities pass through skeletal muscles that contract to help push blood toward the heart ● Interstitial fluid – fluid that leaks from capillaries and enters space outside of cells

□ Hydrostatic pressure outward from capillaries to interstitial space due to pressure from heart □ Osmotic gradient inward from interstitial space to capillaries due to solute concentration in blood □ Arteriole end: hydrostatic pressure>osmotic pressure, venous end: hydrostatic pressure<osmotic pressure

EXAMPLE:

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CONCEPT: HEART PHYSIOLOGY ● Blood pressure must be regulated through a homeostatic system

□ Baroreceptors – pressure sensors found in the heart and arteries □ Cardiac output is increased in response to low blood pressure □ Vasoconstriction of specific arterioles diverts blood to important tissues □ Veins constrict to divert blood volume to heart and arteries □ Vasodilation of arteries leads to a drop in blood pressure

EXAMPLE: ● Cardiovascular disease – disorders that affect the heart or vasculature ● Arteriosclerosis – hardening of arteries due to accumulation of fat deposits □ Cholesterol is transported in blood as low-density lipoprotein (LDL) and high-density lipoprotein (HDL) - LDL delivers cholesterol, and HDL scavenges excess cholesterol ● Myocardial infarction – “heart attack” due to blockage of coronary arteries leading to damage of heart muscle tissue ● Stroke – damage to nervous tissue in the brain from lack of O2, often due to blocked or ruptured artery EXAMPLE:

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CONCEPT: RESPIRATORY PHYSIOLOGY ● Gas exchange allows animals to get O2 for cellular respiration, and get rid of waste CO2 from metabolism ● Small animals can perform gas exchange across their body surfaces due to high SA:V ● Respiratory organs provide surface area for gas exchange in larger organisms EXAMPLE: ● Positive pressure is like pushing, negative pressure is like pulling

□ Positive pressure ventilation – air is pushed into the lungs □ Negative pressure ventilation – air is pulled into the lungs - Diaphragm pulls downward and ribs pull upward on thoracic cavity, creating negative pressure

EXAMPLE:

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CONCEPT: RESPIRATORY PHYSIOLOGY ● Dead space – inhaled air that does not take part in gas exchange, trachea, bronchi, and bronchioles ● Tidal volume – volume of air inhaled and exhaled with each breath ● Vital capacity – volume of air at maximum inhalation and exhalation ● Residual volume – air that remains after forced exhalation EXAMPLE: ● Partial pressure (PX) – hypothetical pressure of a gas alone, but occupying the same volume at same temperature □ Partial pressure = total pressure x % composition of gas mixture □ At high altitude and sea level the % of each gas in atmosphere is the same, but the total pressure differs - Partial pressures of gases are lower at higher altitudes □ Gases diffuse based on partial pressures, move from higher partial pressure to lower partial pressure EXAMPLE:

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CONCEPT: RESPIRATORY PHYSIOLOGY ● Fick’s law of diffusion – gases diffuse based on 5 criteria, most importantly surface area, distance, and partial pressure □ Increasing surface area for gas exchange increases rate of diffusion □ Decreasing the distance gases must travel, like the thickness of a membrane, increases rate of diffusion □ Increasing the difference in partial pressure between the two environments increases rate of diffusion ● Partial pressure drives O2 and CO2 diffusion in the lungs, blood, and tissues

□ PO2 in the lungs is higher than PO2 in the blood, and PO2 in the blood is higher than PO2 in the tissues □ PCO2 in the lungs is lower than PCO2 in the blood, and PCO2 in the blood is lower than PCO2 in the tissues □ Muscles tend to have particularly low PO2, especially during exercise when energy demands increase

● In mammals each breath mixes fresh air mixes with oxygen-depleted air, so PO2 in alveoli is less that atmosphere EXAMPLE: ● Hemoglobin binds O2 to transport it in the blood, and unloads O2 at the tissues ● Cooperative binding – in a binding system, the binding of one thing alters binding of subsequent things

□ When hemoglobin binds one O2, it experiences a conformational change making it easier to bind another O2

● High PO2 in lungs allows Hb to pick up lots of O2, low PO2 in tissues allows Hb to unload lots of O2 EXAMPLE:

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CONCEPT: RESPIRATORY PHYSIOLOGY ● Oxygen dissociation curve, oxygen-hemoglobin equilibrium curve, or oxyhemoglobin saturation curve

□ Sigmoidal curve that shows the O2 saturation of Hb at different PO2 ● Bohr shift – shift to the right of the oxygen dissociation curve due to decreasing pH and increasing PCO2

□ Increasing PCO2 lowers Hb affinity for oxygen - Tissues that are consuming a lot of O2 will generate a lot of CO2, increasing PCO2

□ Lowering pH (increasing acid concentration) lowers Hb affinity for oxygen - CO2 combines with water to form carbonic acid in blood, lowering pH EXAMPLE: ● Carbonic anhydrase – enzyme that catalyzes the formation of carbonic acid (H2CO3) from CO2 and H2O □ Lowers PCO2 in blood, and lowers pH, inducing the Bohr shift and making Hb better at unloading O2

● pH detectors in the respiratory center of the medulla oblongata help regulate ventilation EXAMPLE:

Factors That Affect O2-Binding—The Bohr Effect and Others:

● Several variables affect Hb’s affinity for O2. These are all typical of “working” (e.g. exercising) tissue that needs O2.

□ ↑Temperature→↓Hb Affinity

-Exercising tissue is warmer.

□ ↑2,3-diphosphoglycerate (2,3-DPG)→↓Hb Affinity

-2,3-DPG is a byproduct of glycolysis. Produced more when exercising and at high altitude (where low O2).

□ ↑[H+] (↓pH)→↓Hb Affinity

-Exercising tissues make lactate acid & CO2→↓pH.

□ ↑PCO2→↓Hb Affinity

-Exercising tissues use more O2 and make more CO2.

□ Bohr Effect is combination of ↑PCO2 and ↓pH→↓Hb Affinity

□ All the opposite changes—↓Temp, ↓2,3-DPG, etc.—cause ↑Hb Affinity.

Increased PCO2

Decreased PCO2

PHYSIOLOGY - CLUTCHCH. 16 - RESPIRATORY PHYSIOLOGY

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