Heart and Lungs

Question 1

The Heart

Answer 1

• Right heart refers to patient right and left heart refers to patient left (opposite of what we look at)
• Blood enters the right atrium from the superior__/anterior vena cava, and passes to the right ventricle
• Pulmonary arteries pass blood from the heart to lungs and pulmonary veins pass blood from the lungs to the heart
• Blood reenters the left atrium, goes to the left ventricle, and pumps blood to the aorta

Question 2

Aorta and Arteries

Answer 2

• Aorta is the largest, 5cm² cross sectional area
• 120 mmHg to 80 mmHg blood pressure
• Volume of blood fround in aorta and arteries is about 16% to 20%
• Deal with a lot of pressure, and therefore have thick walls and are composed of smooth muscle and connective tissue, containing collagenous and elastic fibers

Question 3

Systole and Diastole

Answer 3

• Systole is when the left ventricle contracts, and sends blood out of the aorta (120 mmHg)
• Diastole is when the ventricles begin to relax and fill with blood (80 mmHg)

Question 4

Arterioles

Answer 4

• Arterioles are important because they are the source of the major portion of resitance in the cardiovascular system
• Have strong muscular walls

Question 5

Capillaries

Answer 5

• Diffusion occurs at the capillaries
• Capillaries have signficant cross sectional area - 3000 cm²; walls are made of endothelial cells
• 5% to 7% of total blood; 25 mmHg

Question 6

Veins

Answer 6

• Blood flows from the capillaries to the veins; blood pressure drops to between 0 mmHg and 25 mmHg
• 7 cm² cross sectional area, with faster moving blood than capillaries
• 50% of blood is in veins at any given time
• Veins have valves to prevent backflow of blood

Question 7

Blood Flow in the Heart

Answer 7

• Atrioventricular valves pass blood from atriums to ventricles
  
  • Produce “lub” sound
• Semilunar valves (pulmonary and aortic) pass blood from ventricles to pulmonary artery and aorta
  
  • Produce “dub” sound

Question 8

Electrical Activity of the Heart

Answer 8

• Sinoatrial node (SA) is the pacemaker, lacated near the junction of the superior vena cava and the right atrium
• SA node produces the electrical impulse, and propogates through the rest of the heart; spreads to the atrioventricular node (AV)
• AV node stimulates the bundle of His, which stimulates the contraction of the ventricles, starting at the apex, travelling to the center

Question 9

Cardiac Output

Answer 9

• Amount of blood which is pumped per minute by each of the two individual ventricles
• Equal to stroke volume (L/beat) times heart rate (beat/min)

Question 10

Poiseuille’s Law

Answer 10

• Defines the relationship between the radius and length of a tube, the change in pressure between the two ends of the tube, the viscosity, and the flow rate of a fluid in that tube
• Proportional to r⁴
  
  • ^​Flow rate is highly dependent on radius
• Inversely proportional to the length of the vessel and viscosity
  
  • Shorter and less viscous a fluid, faster the rate of flow
• Change in pressure drives blood flow

Question 11

Osmosis

Answer 11

• Osmolarity measures to concentration of solute particles that we have in solution
• Osmotic pressure is the amount of pressure that stops osmosis; directly proportional to the differnce in height of the water in the u-tube
  
  • Also proportional to the number of dissolved molecules in solution; higher osmolarity, higher osmotic pressure

Question 12

Lymphatic System

Answer 12

• Lymphatic system runs parallel to circulatory system; collects liquid that leaks into interstitial space
• Lymph nodes help filter out particulates in the blood

Question 13

Blood Clotting

Answer 13

• Occurs as a cascade process
• Thrombin allows for fibrinogen to fibrin
• Fibrin has optimal charge to allow polymerization of fibrin monomers; generates soft clot
• Transglutaminase generates the hard clot which has cross-linked fibrin monomers
• Vitamin K is fat-soluble and necessary for proper blood clotting
• Vitamin K antagonists hinder blood clotting
  
  • Warafarin, Dicoumarol

Question 14

Mechanics of Breathing

Collapsed Lung

Answer 14

• As the diaphragm contracts, the muscles of the rib cage contract as well, causing the rib cage to move upward and out, enlarging the are of the thoracic cage that contain the lungs
• As this happens, effective negative pressure builds in the lungs, resulting in inspiration
• After the muscles stop contracting, their elastic nature brings them back to their normal shape, resulting in expiration
• A collapsed lung occurs when the lungs are separated from the visceral pleura, which provide rigidity for the otherwise structureless lungs

Question 15

Gas Exchange

Answer 15

• Deoxygenated blood has a PO₂ of 40 mmHg and a PCO₂ of 46 mmHg
• Oxygen diffuses down its concentration gradient from the alveoli to capillaries; carbon dioxide does the opposite
• Oxygenated blood has a PO₂ of 100 mmHg and a PCO₂ of 40 mmHg

Question 16

Hemoglobin

Answer 16

• Hemoglobin​ (Hb) is the oxygen transport protein in blood
• Hb is a tetramer, each monomer has an ferrous group that binds oxygen; each tetramer can bind 4 diatomic oxygen molecules
• When PO₂ = 100 mmHg (alveoli), Hb is 98% saturated; when PO₂ = 40 mmHg (tissue), Hb loses about 25% of oxygen

Question 17

pH and Hemoglobin

Answer 17

• Normal blood pH is about 7.4
• If pH drops, Hb’s affinity for oxygen decreases
• This leads to greater oxgyen deposition in tissue
  
  • Since affinity for oxygen decreases, more oxygen is released from Hb than in normal pH blood at same PO₂
• This is what happens when you exercise

Question 18

Temperature and Hemoglobin

Answer 18

• Average internal body temperature is 37^oC
• Increasing temperature decreases Hb’s affinity for oxygen
  
  • Same situation with decreasing pH (increasing acidity)

Question 19

2,3-Bisphosphoglycerate and Hemoglobin

Answer 19

• 2,3-bisphosphoglycerate (2,3-BPG) binds to Hb, and decreases Hb’s affinity for oxygen
• 2,3-BPG is a byproduct of glycolysis, and is generated when humans inhabit higher altitudes where atmospheric PO₂ is decreased
• 2,3-BPG ensures greater oxygen deposition in deep tissue to counter the thinner air of high altitudes

Question 20

Carbon Dioxide in the Blood

Answer 20

• Carbon dioxide can travel:
  
  • Dissolving in the plasma/blood cells (10%)
  • Binding to Hb (20%)
  • As bicarbonate (70%)
• In deep tissue, carbon dioxide will diffuse down its concentration gradient into blood
• Carbonic anhydrase convert carbon dioxide and water to carbonic acid and vice versa

Question 21

Control of Breathing

Answer 21

• Breathing rhythm is controlled by the medulla and the pons (in brainstem)
• Contraction of pulmonary muscles (the action of breathing) is stimulated by carbon dioxide and proton concentrations
  
  • Affects chemosensitive areas in the medulla
• Oxygen levels are sensed by chemoreceptors in the aorta

Question 22

What Happens When You Breath into a Bag?

Answer 22

• As you breath into a bag, the concentration of carbon dioxide increases
• This stimulates your body to breath deeper and faster becuase there is too much carbon dioxide in the blood
• Relatedly, if you were to breath pure oxygen, your body would respond by breathing slower and less deep