EXAM 3 - Exam 3 Information PDF

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Exam 3 Circulation Cardiovascular System ● Transport of material: gases, nutrients, waste, communication, defense against pathogens, temperature homeostasis ● Heart is a pump ○ Atria receives blood returning to heart ○ Ventricles pump blood out ○ Septum divides left and right halves ● Blood vessels ○ Veins, arteries and capillaries ○ Pulmonary and systemic circulation ○ Portal system joins two capillary beds in series ● Blood ○ Cells and plasma

Composition of blood ● Spun tube of blood yields three layers ○ Erythrocytes on bottom (~45% of whole blood) ■ Hematocrit: percent of blood volume that is RBCs ● Normal values: males 47% +- 5, females 42% +-5 ■ Most dense component ○ WBCs and platelets in buffy coat (100 bpm) ○ If persistent, may lead to fibrillation ● Bradycardia: heart rate slower than 60 bpm ○ May result in grossly inadequate blood circulation in nonathletes ○ May be desirable result of endurance training The Cardiac Cycle ● One part contraction followed by relaxation

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One cardiac cycle consists of the contraction (systole) and relaxation (diastole) of both atria, rapidly followed by the systole and diastole of both ventricles ○ Electrical events ○ Pressure changes ○ Heart sounds ○ Volume changes ○ Mechanical events 1. Late diastole - both sets of chambers are relaxed and ventricles fill passively 2. Atrial systole - atrial contraction forces a small amount of additional blood into vesicles 3. Isovolumic ventricular contraction - first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves 4. Ventricular ejection - as ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected 5. Isovolumic ventricular relaxation - as ventricles relax, pressure in ventricles falls … blood flows back into cusps of semilunar valves and snaps them closed Heart sounds ○ Two sounds (lub-dup) associated with closing of heart valves ■ First sound is closing of AV valves at beginning of ventricular systole ■ Second sound is closing of SL valves at beginning of ventricular diastole ○ Mitral valve closes slightly before tricuspid, and aortic closes slightly before pulmonary valve ■ Differences allo auscultation of each valve when stethoscope is placed in four different regions ■ Heart murmurs: abnormal heart sounds when blood hits obstructions Mechanical events of heart ○ Ventricular filling: mid to late diastole ■ Pressure is low; 80% of blood passively flows from atria through open AV valves into ventricles from atria (SL valves closed) ■ Atrial depolarization triggers atrial systole (P wave), atria contract, pushing remaining 20% of blood into ventricle ● End diastolic volume (EDV): volume of blood in each ventricle at end of ventricular diastole ○ Isovolumetric contraction ■ Atria relax; ventricles begin to contract ■ Rising ventricular pressure causes closing of AV valves ■ Isovolumetric contraction phase is split-second period when ventricles are completely closed (all valves closed), volume remains constant, ventricles continue to contract ■ When ventricular pressure exceeds pressure in large arteries, SL valves are forced open ○ Isovolumetric relaxation: early diastole ■ Following ventricular repolarization (T wave), ventricles ela ■ End systolic volume (ESV): volume of blood remaining in each ventricle after systole

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Ventricular pressure drops causing backflow of blood from aorta and pulmonary trunk that triggers closing of SL valves ● Ventricles are completely closed chambers momentarily … referred to as isovolumetric relaxation phase Closure of aortic valve raises aortic pressure as backflow rebounds off closed valve cusps ● Referred to as dicrotic notch ● Atria continue to fill during ventricular systole and when atrial pressure exceeds ventricular pressure, AV valves open; cycle begins again

Cardiac output ● CO is the volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute ● Stroke volume (SV) is the amount of blood pumped out of the ventricle in one beat ● CO (mL/min) = SV (mL/beat) x HR (beats/min) ● Regulation of stroke volume ○ 3 factors regulate stroke volume ■ Preload: degree of stretch of heart muscle ● Degree to which cardiac muscle cells are stretched just before they contract ● Most important factor in preload stretching of cardiac muscle is venous return - amount of blood returning to heart ■ Afterload: back pressure exerted by arterial blood ● Afterload is pressure that ventricles must overcome to eject blood ○ Back pressure from arterial blood pushing on SL valves is major pressure ■ Contractility: contractile strength at given muscle length ○ Mathematically: SV = EDV - ESV ■ EDV is affected by length of ventricular diastole and venous pressure (~120 mL/beat) ■ ESV is affected by arterial BP and force of ventricular contraction (~50 mL/beat) ■ Normal SV = 120 mL - 50 mL = 70 mL/beat ■ Ejection fraction is a measurement (%) of the percentage of blood leaving your heart each time it contracts ■ An LV ejection fraction of 55% or higher is considered normal, 50% or lower is considered reduced Types of blood vessels ● Arteries: carry blood away from heart ● Arterioles: are smallest branches of arteries ● Capillaries: are smallest blood vessels ○ Location of exchange between blood and interstitial fluid ● Venules: collect blood from capillaries ● Veins: return blood to heart ● Blood flow: arteries → arterioles → capillaries → venules → veins ●

Blood vessel structure

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In general, a blood vessel has 3 layers Tunica interna: innermost layer, adjacent to lumen ■ Inner lining of vessel ○ Tunica media: middle layer, smooth muscle and elastic fibers ○ Tunica externa: outermost layer, adjacent to surrounding tissue Artieries: carry blood away from the heart to the tissue ○ The walls of the arteries are elastic , which allows them to absorb the pressure created by ventricles of the heart as they pump blood into the arteries ○ Because of the smooth muscle in the tundica media, arteries can regulate their diameter ○ First received blood ejected rom ventricles of the heart Capillaries: are microscopic vessels that usually connect arterioles and venules ○ Capillary walls are composed of a single layer of cells and a basement membrane ■ Because their walls are so thin, capillaries permit the exchange of nutrients and wastes between blood and tissue cells ○ Blood flow through capillaries ■ Capillaries branch to form an extensive capillary network throughout the tissues and are found near almost every cell in the body \ ○ Continuous capillaries - most common ■ Tiny pores in walls, limited passage of substances ■ Ions remain in blood ■ Formed by endothelial cells ○ Fenestrated capillaries - in kidneys - filter small molecules ■ Larger pores, permit more filtration ■ Endocrine glands - permit absorption of hormones from endocrine cells into bloodstream ○ Sinusoid capillaries - in liver - leaky, allow passage of large molecules and recycled RBC components ■ Liver contains sinusoids ■ Detoxification … destroys toxins through sinusoids Venules: smallest veins that are formed by the union of several capillaries ○ Venules drain blood from capillaries into veins Veins: veins are formed from the union of several venules ○ Compared to arteries, veins have a thinner tunica interna and media and a thicker tunica externa ■ Veins have less elastic tissue and less smooth muscle than arteries ○ Veins contain valves ■ Help move blood back to heart

Blood distribution ● At rest, the largest portion of the blood is in systemic veins and venules, which are considered blood reservoirs Capillary exchange ● Substances cross capillary walls by ○ Diffusion

○ Transcytosis - endo + exocytosis ○ Bulk flow ● Diffusion and transcytosis ○ Substances such as oxygen, carbon dioxide, glucose, amino acids, and some hormones cross capillary walls via simple diffusion ○ Large, lipid-insoluble (like insulin) cross capillary walls in vesicles via transcytosis ● Bulk flow ○ Bulk flow is a passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction ■ Bulk flow occurs from an area of higher pressure to an area of lower pressure, and it continues as long as a pressure difference exists ○ Bulk flow is more important for regulation of the relative volumes of blood and interstitial fluid Filtration and reabsorption ● Filtration is pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid ○ Blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IFOP) promote filtration ● Reabsorption is pressure-driven movement of fluid and solutes from interstitial fluids into blood capillaries ○ Interstitial fluid hydrostatic pressure (IFHP) and blood colloid osmotic pressure (BCOP) promote reabsorption Blood flow ● Blood flow is the volume of blood that flows through any tissue in a given time period (in mL/min) ● Total blood flow is cardiac output (CO), the volume of blood that circulates through systemic (or pulmonary) blood vessels each minute ○ CO = heart rate (HR) x stroke volume (SV) ○ CO = mean arterial pressure (MAP) / resistance ® ● Velocity of flow is the distance a fixed volume of blood travels in a given period of time ● Fluid flow through a tube depends on the pressure gradient ● Flow through a tube is directly proportional to the pressure gradient ○ Flow ~ change in P ○ The higher the pressure gradient, the greater the fluid flow ○ Fluid flows only if there is a positive pressure gradient ○ Flow depends on the pressure gradient, not the absolute pressure ● Resistance opposes flow ● Small change in radius has a large effect on resistance to blood flow ○ Vasoconstriction is a decrease in blood vessel diameter/radius and decreases blood flow ■ Increased resistance ○ Vasodilation is an increase in blood vessel diameter/radius and increases blood flow ■ Decreased resistance ● Flow of blood in the cardiovascular system is ○ Directly proportional to the pressure gradient

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○ Inversely proportional to the resistance flow Vascular resistance ® - friction between blood and walls of blood vessels ○ The higher the resistance the smaller the blood flow ○ R is the opposition to blow flow due to friction between blood and the walls of blood cells ■ The higher the R, the smaller the blood flow ○ R depends on ■ Size of blood vessel lumen - smaller diameter higher R ■ Blood viscosity - flowability, thickness or stickiness of blood ● Blood is much more viscous than water because it contains formed elements (primarily RBCs) and plasma proteins ■ Total blood vessel length - the longer the vessel, the greater the resistance ● Bigger people can have low blood pressure problems Blood pressure (BP) ○ Contraction of the ventricles generates BP ○ BP is determined by CO, blood volume, and vascular resistance ○ The higher the BP, the greater the blood flow ○ When ventricles contract, arteries receive blood at highest pressure ■ Higher force generated by left ventricle = higher BP ○ Max BP occurs during systole ■ Systolic BP … 100 mmHg ○ BP = systolic pressure / diastolic pressure ○ Pulse pressure = systolic - diastolic pressure ○ Mean arterial pressure = diastolic + ⅓ pulse pressure Venous return: the volume of blood flowing back to the heart through the systemic veins, occurs due to the pressure generated by contractions of the heart’s left ventricle ○ Increased VR leads to greater cardiac output ○ Assisted by ■ Valves - help to move blood in low BP vessels ■ Respiratory pump - thoracic cavity action ● Inhaling decreases thoracic pressure ● Exhaling raises thoracic pressure ■ Skeletal muscle pump ● Exercising improves circulation ● Squeeze veins when skeletal muscles contract ○ Distal valve closes + prevents pulling of vein, squeezing opens proximal valve, increases pressure ○ Determines stroke volume ■ How much blood is pumped out of heart ■ Higher VR, more stretching of heart, greater stroke volume, greater cardiac output, higher BP

Control of BP and blood flow ● Baroreceptors are important pressure sensitive sensory neurons that monitor stretching of the walls of blood vessels and the atria ○ Provide input to cardiovascular system and medulla oblongata, activate cardiac accelerator nerve, which stimulates SA node to generate AP at faster rates which increases BP ● Blood pressure BP ○ Systemic arterial BP is measured indirectly by auscultatory methods using a sphygmomanometer ■ Wrap cuff around arm superior to elbow ■ Increase pressure in cuff until it exceeds systolic pressure in brachial artery ■ Pressure is released slowly, and examiner listens for sounds of Korotkoff with a stethoscope ○ Systolic pressure: normally less than 120 mmHg ■ Pressure when doudna first occur as blood starts to spurt through artery ○ Diastolic pressure: normally less than 80 mmHg ■ Pressure when sounds disappear because artery no longer constricted; blood flowing freely Circulatory routes ● Systemic circulation ● Pulmonary circulation ● Hepatic portal circulation

Ventilation and Gas Exchange Breathing and respiration ● Respiration is the exchange of gases between the atmosphere, blood, and cells ● The combination of 3 processes is required for respiration to occur ○ Ventilation (breathing) ○ External (pulmonary) respiration ■ Oxygenation of blood ○ Internal (tissue) respiration ■ Exchange of oxygenated blood and tissue ● The cardiovascular system assists the respiratory system by transporting gases Structures of the respiratory system ● Structurally, the components of the respiratory system are divided into two parts ○ Upper respiratory system - consists of the nose, pharynx, and associated structures ○ Lower respiratory system - consists of the larynx, trachea, bronchi, and lungs ● Functionally, the components of the respiratory system are divided into two zones ○ Conducting zone ■ Trachea, main bronchi, lobar and segmental bronchi, bronchioles and terminal bronchioles ○ Respiratory zone ■ Respiratory bronchioles, alveolar ducts, alveolar sacs ● The lungs are paired organs in the thoracic cavity ○ Branching of the bronchial tree: trachea → main bronchi → lobar bronchi → segmental bronchi → bronchioles → terminal bronchioles ●

Alveoli ○ When the conducting zone ends at the terminal bronchioles, the respiratory zone begins ○ The respiratory zone terminates at the alveoli, the air sacs found within the lungs ○ There are two kinds of alveolar cells, type I and type II ● Respiratory membrane is composed of ○ A layer of type I and type II alveolar cells and associated alveolar macrophages that constitutes the alveolar wall ○ An epithelial basement membrane underlying the alveolar wall ○ A capillary basement membrane that is often fused to the epithelial basement membrane ○ The capillary endothelium Pulmonary ventilation ● In pulmonary ventilation, air flows between the atmosphere and alveoli of the lungs because of alternating pressure differences created by contraction and relaxation of respiratory muscles ○ Inhalation ○ Exhalation ● Boyle’s law: pressure changes that drive inhalation and exhalation are governed, in part, by

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Boyle’s Law ○ The volume of a gas varies inversely with its pressure Dalton’s law and partial pressures ○ Composition of air ■ 78.6% N2 ■ 20.9% O2 ■ 0.5% H2O ■ 0.04% CO2 ○ Atmospheric pressure (760 mmHg) ■ Produced by air molecules bumping into each other ○ Each gas contributes to the total pressure ■ In proportion to its number of molecules (Dalton’s Law) Diffusion between liquids and gases ○ Henry’s law ■ When gas under pressure comes in contact with liquid ● Gas dissolves in liquid until equilibrium is reached ■ At a given temperature ● Amount of a gas in solution is proportional to partial pressure of that gas ■ The actual amount of a gas in solution (at given partial pressure and temperature) ● Depends on the solubility of that gas in that particular liquid ■ Increasing the pressure drives gas molecules into solution until an equilibrium is established ■ When the gas pressure decreases, dissolved gas molecules leave the solution until a new equilibrium is reached Pressure changes in pulmonary ventilation ○ At rest, when the diaphragm is relaxed, alveolar pressure is equal to atmospheric pressure and there is no air flow ○ During inhalation, the diaphragm contracts and the external intercostals contract. The chest cavity expands, and the alveolar pressure drops below atmospheric pressure. Air flows into the lungs in response to the pressure gradient and the lung volume expands. During deep inhalation, the scalene and sternocleidomastoid muscles expand the chest further, thereby creating a greater drop in alveolar pressure ○ During exhalation, the diaphragm relaxes and the external intercostals relax. The chest and lungs recoil, the chest cavity contracts, and the alveolar pressure increases above atmospheric pressure. Air flows out of the lungs in response to the pressure gradient, and the lung volume decreases. During forced exhalations, the internal intercostals and abdominal muscles contract, thereby reducing the size of the chest cavity further and creating a greater increase in alveolar pressure Factors affecting pulmonary ventilation ○ Surface tension ■ Inwardly directed force in the alveoli which must be overcome to expand the lungs during each inspiration ○ Elastic recoil ■ Decreases the size of the alveoli during expiration

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Compliance - ease with which the lungs and thoracic wall can be expanded ■ An indicator of expandability ■ Low compliance requires greater force ■ High compliance requires less force ■ Depends on stretchability of elastic fibers within lungs and surface tension inside alveoli ■ Other factors that affect compliance ● Connective tissue structure of the lungs ● Level of surfactant production ● Mobility of the thoracic cage Intrapulmonary and intrapleural pressures ● The intrapulmonary pressure ○ Also called intra-alveolar pressure ○ Is relative to atmospheric pressure ○ In relaxed breathing, the difference between atmospheric pressure and intrapulmonary pressure is small ■ About -1 mmHg on inhalation or +1 mmHg on exhalation ● The intrapleural pressure ○ Pressure in space between parietal and visceral pleura (covering around lungs) ○ Remains below atmospheric pressure throughout respiratory cycle Respiratory rates and volumes ● Respiratory system adapts to changing oxygen demands by varying ○ The number of breaths per minute (respiratory rate) ○ The volume of air moved per breath (tidal volume) ● The respiratory minute volume (Ve) ○ Amount of air moved per minute ○ Is calculated by: respiratory rate x tidal volume ○ Measures pulmonary ventilation ● Alveolar ventilation (Va) ○ Volume of air that actually reaches the respiratory zone … will actually participate in gas exchange ○ Only a part of respiratory minute volume reaches alveolar exchange surfaces ○ Volume of air remaining in conducting passages is anatomic dead space ○ Alveolar ventilation is the amount of air reaching alveoli each minute ○ Calculated as ■ (tidal volume - anatomic dead space) x respiratory rate ● Relationships among Vt, Ve, and Va ○ Determined by respiratory rate and tidal volume ■ For a given respiratory rate: ● Increasing tidal volume increases alveolar ventilation rate ■ For a given tidal volume ● Increasing respiratory rate increases alveolar ventilation ● Tidal volume: the amount of air moved into and out of lung with each breath ○ ~ 500 mL

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Inspiratory reserve volume (IRV): amount of air that can be inspired forcibly beyond the tidal volume ○ 2100-3200 mL ● Expiratory reserve volume (ERV): amount of air that can be forcibly expelled from lungs ○ 1000-1200 mL ● Residual volume (RV): amount of air that always remains in lungs ○ Needed to keep alveoli open Breathing patterns and respiratory movements ● Eupnea - quiet breathing or resting respiratory rate ○ Adults: 12-18 breath/min ● Apnea - the cessation of breathing ● Dyspn...