AP Biology, Chapter 42
Circulation and Gas Exchange

SUMMARY
INTRODUCTION

CIRCULATION IN ANIMALS
	Transport systems functionally connect the organs of exchange with the body cells:  		an overview
		1. Describe the need for circulatory and respiratory systems due to increasing animal 
		body size.
			a. Not enough surface area exposed to environment
			b. Internal gas exchange and transport substitutes for direct contact
	Most invertebrates have a gastrovascular cavity or a circulatory system for internal 
	transport
		2. Explain how a gastrovascular cavity functions in part as a circulatory system.
			a. Opens to the aqueous environment
			b. Extensions go through all parts of the organism
		3. Distinguish between open and closed circulatory systems.
			a. Open
				i. Heart pumps blood into major vessels towards the head
				ii. Vessels open, hemolymph washes over organs
				iii. One-way ostia in the heart suck the hemolymph back up
			b. Closed
				i. Blood stays in continuous system of blood vessels
				ii. Materials exchanged through capillary walls
	Vertebrate phylogeny is reflected in adaptations of the cardiovascular system
		4. List the structural components of a vertebrate circulatory system and relate their 
		structure to their functions.
			a. Heart moves the blood in specific directions: atria  ventricle
			b. Blood vessels carry materials and allow exchange
			c. Blood carries dissolved materials and cells
		5. Describe the general relationship between metabolic rates and the structure of the 
		vertebrate circulatory system.
			a. Low metabolic rate; fish
				i. Two-chambered heart: bodyatriumventriclegillsbody
				ii. Low pressure after gills; can't deliver as much oxygen
			b. Medium energy requirements; terrestrial ectotherms
				i. Three-chambered heart: blood returned to heart after gas exchange
				ii. Partially oxygenated blood pumped at higher pressure
			c. High metabolism; endotherms
				i. Four-chambered heart: blood returning from lungs kept separate
				ii. Left ventricle pumps pure oxygenated blood to body under high 
				pressure
	Double circulation in mammals depends on the anatomy and pumping cycle of the 
	heart
		6. Distinguish between pulmonary and systemic circuits and explain the functions of 
		each.
	a. Pulmonary: O-poor R ventricle, pulmonary arteries, lungs; O-rich, pulmonary 
	veins, left atrium
	b. Systemic: O-rich L ventricle, aorta, body tissues; O-poor, venae cavae, R 
	atrium

		7. Define a cardiac cycle, distinguish between systole and diastole, and explain what 
		causes the first and second heart sounds.
			a. Cardiac cycle: atria contract, then ventricles, then both rest and refill
			b. Systole is contraction, diastole is rest
			c. Sounds
				i. "Lub": blood recoils against closed AV valves
				ii. "Dup": blood recoils against closed semilunar valves
		8. Define cardiac output and describe two factors that influence it.
			a. Cardiac output is volume pumped by left ventricle per minute
			b. Factors: heart rate, stroke volume
		9. List the four heart valves, describe their location, and explain their functions.
			a. Tricuspid b/w R atrium and R ventricle; blocks RVRA
			b. Bicuspid b/w L atrium and L ventricle; blocks LVLA
			c. Pulmonary semilunar b/w R ventricle and pulmonary trunk; blocks pul.RV
			d. Aortic semilunar b/w L ventricle and aorta; blocks aortaLV
		10. Define heart murmur and explain its cause.
			a. Valve defect causes altered heart sound
			b. Caused by development, infection, wear-and-tear
		11. Define pacemaker and describe the location of two patches of nodal tissue in the 
		human heart.
			a. Pacemaker
				i. Sinoatrial node of cardiac conduction system
ii. Highest rate of depolarization
				iii. Takes the lead, the rest of the heart responds to it
			b. Atrioventricular node can initiate but is slower		
		12. Describe the origin and pathway of the action potential (cardiac impulse) in the 
		normal human heart.
			a. SA node, AV node, AV bundle, bundle branches, Purkinje fibers
		13. Explain how the pace of the SA node can be modulated by sympathetic and 
		parasympathetic nerves, changes in temperature, physical conditioning, and exercise.
			a. Nervous: sympathetic up, parasympathetic down
			b. Temperature: high up, low down
			c. Conditioning: exercise up, but resting rate may be lower
	Structural differences of arteries, veins, and capillary vessels correlate with their 
	different functions
		14. Relate the structures of capillaries, arteries, and veins to their functions.
			a. Capillaries: thin-walled for exchange
			b. Arteries: thick-walled to contain and modulate high pressure
			c. Veins: thinner and valved to keep low-pressure blood flowing toward the heart
	Physical laws governing the movement of fluids through pipes affect blood flow and 
	blood pressure
		15. Explain why blood flow through capillaries is substantially slower than it is through 
		arteries and veins.
			a. Capillaries have a much smaller diameter
			b. But there are many more of them, much higher cross-sectional area
		16. Define blood pressure and describe how it is measured.
			a. Hydrostatic force against blood vessel walls
			b. Measured
				i. Block a major artery
				ii. Slowly release the pressure
				iii. When blood first is heard to flow  systolic pressure
				iv. When no longer heard  diastolic pressure
		17. Explain how peripheral resistance and cardiac output affect blood pressure.
			a. Peripheral resistance: elastic arteries and arterioles squeeze blood during 
			diastole
			b. Cardiac output: the more blood the heart is pumping, the higher the pressure
		18. Explain how blood returns to the heart even though it must sometimes travel from 
		the lower extremities against gravity.
			a. Muscles squeeze the veins
			b. Vein smooth muscles contract
			c. Pressure changes during breathing 
	Transfer of substances between the blood and the interstitial fluid occurs across the 
	thin walls of capillaries
		19. Explain how blood flow through capillary beds is regulated.
			a. Arteriole smooth muscles can reduce flow to capillary beds
			b. Precapillary sphincters can close off beds
	The lymphatic system returns fluid to the blood and aids in body defense
		20. Describe the composition of lymph and explain how the lymphatic system helps the 
		normal functioning of the circulatory system.
			a. Lymph is similar to blood plasma
			b. Leaks out of capillaries, washes over tissues, returned to veins by lymphatic 
			vessels after filtering
	Blood is a connective tissue with cells suspended in plasma
		21. Describe the composition and functions of plasma.
			a. 90% water; carries dissolved solutes
			b. Components
				i. Proteins buffer, maintain osmotic balance, function in immunity
				ii. Ions are delivered for cells to maintain membrane potential
				iii. Nutrients are delivered to cells
				iv. Wastes are carried for disposal
				v. HDL and LDL droplets carry lipids for disposal and deposit, 
				respectively
		22. Relate the structure of erythrocytes to their functions.
			a. No nuclei, thin in the center
			b. Small with high surface area to exchange gases quickly
			c. Flexible so they can squeeze through capillaries
		23. List the general functions of white blood cells.
			a. Phagocytize debris and invading organisms
			b. Trigger inflammation
			c. Produce antibodies
			d. Specifically attack and kill cancer and pathogens
			e. Memorize self- and nonself- antigens
		24. Relate the structure of platelets to their functions.
			a. Small cell fragments with stored signals for hemostasis
			b. Functions
				i. Bind to exposed collagen at site of damage
				ii. Release molecules to attract more platelets forming the plug
				iii. Release serotonin to make the bleeding vessel spasm or constrict
				iv. Provide molecules required for the clotting reaction
				v. Clotting cascade ends with soluble fibrinogen forming the fibrin mesh
		25. Explain what prevents spontaneous clotting in the absence of injury.
			a. Clotting reactions are very sensitive to concentration
			b. Anticlotting factors are present
	Cardiovascular diseases are the leading cause of death in the United States and most 
	other developed nations
		26. Distinguish between a heart attack and a stroke; and atherosclerosis and 
		arteriosclerosis.
			a. Heart attack: blood clot in capillary artery starves heart muscle of oxygen
			b. Stroke: blood clot in brain artery starves brain tissue of oxygen
			c. Atheroclerosis: plaques grow to block arteries
			d. Atherosclerosis: plaques damage arterial walls making them less elastic 
		27. List the factors that have been correlated with an increased risk of cardiovascular 
		disease.
			a. Smoking (duh), obesity, lack of exercise, high blood pressure, heredity

GAS EXCHANGE IN ANIMALS
	Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide:  
	an overview
		32. Describe the general requirements for a respiratory surface and list the variety of 
		respiratory organs that have adapted to meet them.
			a. Requirements: moist and large enough to exchange for all the body cells
			b. Organs
				i. Outside and inside surface in cnidarians
				ii. Skin/outer covering in worms and amphibians
				iii. Gills in many aquatic vertebrates and invertebrates
				iv. Tracheal tubes in insects
				v. Lungs in vertebrates
	Gills are respiratory adaptations of most aquatic animals
		34. Describe respiratory adaptations of aquatic animals.
			a. Simple bumps on starfish
			b. Part of parapodia on annelids
			c. Under shell/exoskeleton in mollusks, decapods
		35. Describe the advantages and disadvantages of water as a respiratory medium.
			a. Advantage: no problem keeping membranes moist
			b. Dis-: lower [O2] in water, changes with temp. and salinity
		36. Describe countercurrent exchange and explain why it is more efficient than the 
		concurrent flow of water and blood.
			a. Blood flows one direction, water flows opposite
			b. Efficiency
				i. Flow in the same direction, diffusion would make them equal
				ii. Flow opposite, highest [O2] water flows by highest [O] blood
	Tracheal systems and lungs are respiratory adaptations of terrestrial animals
		37. Describe the advantages and disadvantages of air as a respiratory medium and 
		explain how insect tracheal systems are adapted for efficient gas exchange in a 
		terrestrial environment.
			a. Advantages: rapid diffusion, high [O2], less dense = less energy to get it
			b. Dis-: dries membranes
			c. Insects
				i. Small can simply diffuse gases through tubes to each cell
				ii. Large pump air through tracheae especially during flight
		38. For the human respiratory system, describe the movement of air through air 
		passageways to the alveolus, listing the structures that air must pass through on its 
		journey.
			a. Nose+mouth  nasal cavity+pharynx  larynx  trachea  bronchi  
			bronchioles  alveoli
		39. Compare positive and negative pressure breathing. Explain how respiratory 
		movements in humans ventilate the lungs.
			a. Positive: air pushed down into lungs, like swallowing
			b. Negative: air pulled down, like into a syringe
			c. Human
				i. Diaphragm and rib muscles increases the volume of the thorax
				ii. Airtight seal between lungs and thorax wall
				iii. When the wall expands, the lungs expand
		40. Distinguish between tidal volume, vital capacity, and residual volume.
			a. TV: normal breath
			b. VC: forced in, forced out
			c. Residual: amount remaining after forced exhalation
		41. Explain how the respiratory system of birds is different from that in mammals.
			a. Mammals have dead end passageways
			b. Birds have posterior air sacs and flow-through lungs
	Control centers in the brain regulate the rate of depth of breathing
		42. Explain how breathing is controlled.
			a. Breathing can be voluntary but is mainly automatic
			b. Sensors
				i. Blood CO2  pH of cerebrospinal fluid; low pH, faster breathing
				ii. Stretch receptors in lungs prevent over-inflation
				iii. O2-sensors in major arteries; speed up heart rate for very low [O2]
			c. Control centers
				i. Medulla: sets rhythm
				ii. Pons: moderates/coordinates/smooths out
	Gas diffusion down pressure gradients in the lungs and other organs
		43. Define partial pressure and explain how it influences diffusion across respiratory 
		surfaces.
			a. Partial pressure is concentration of a gas in a liquid or gas solution
			b. Diffusion of gases: greater pp to lower pp
				i. Alveoli: high O2, low CO2
				ii. Blood around alveoli: vv
	Respiratory pigments transport gases and help buffer the blood
		44. Describe the adaptive advantage of respiratory pigments in circulatory systems. 
		Distinguish between hemocyanin and hemoglobin.
			a. Pigments store/carry more O2 than can simply dissolve
			b. Diversity
				i. Hemocyanin: protein+porphyrin+Cu; arthropods and mollusks
				ii. Hemoglobin: protein+porphyrin+Fe; annelids, mammals
		45. How is O2 carried in the blood? 
			a. Most attached to hemoglobin 
			b. A little dissolved in the plasma 
		46. How is CO2 carried in the blood?
			a. Most as bicarbonate ion after reaction with water 
			b. Some attached to hemoglobin 
			c. A little dissolved in the plasma 
	Deep-diving mammals stockpile oxygen and consume it slowly
		47. Describe respiratory adaptations of diving mammals and the role of myoglobin.
			a. Weddell seal
				i. Twice as much blood per kg
				ii. 24 L spleen
				iii. Stores 25% of its oxygen in muscle attached to myoblobin
			b. Myoglobin: monomeric homologue to hemoglobin in muscle cells