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Why do we breathe?
sustains cellar respiration (burn carbohydrates, lipids, and proteins & makes ATP)
What is Fick’s Law?
Rate of diffusion = k x A x (P2-P1)/D
When do the greatest amount of O2 and CO2 diffuse?
Surface area (A) is large
Respiratory surface is extremely thing (D small)
Partial pressure gradient is large
What is partial pressure?
the pressure of a particular gas in a mixture of gases
What makes total atmospheric pressure?
the sum of the partial pressure of a mixture of gases
What is bulk flow?
gas exchange with transport
What does Bulk flow in both ventilation and circulation require?
A pump to produce pressure (P) that drives flow (Q) against the resistance to flow (R)
Q =P/R
What is step 1 of Bulk flow?
Ventilation
breathing moves air (containing O2) into the lungs and air (containing CO2) out of the lungs
What is step 2 of bulk flow?
Gas exchange
diffusion across the respiratory surface: O2 diffuses from the lung into the blood and CO2 diffuses out of the blood into the lungs
What is step 3 of Bulk Flow?
Circulation
circulation by bulk flow: O2 and CO2 are transported by the circulatory system to and from cells
What is the 4th and final step of Bulk flow?
cellular respiration
diffusion between blood and cells: O2 diffuses from the blood into the cells and CO2 diffuses out of the cells into the blood
What are general kinds of gas exchange organs in different animals?
some animals breathe across their body surfaces
other animals need specialized organ for gas exchange to provide a greater surface area for gas exchange
What are gills?
highly folded delicate structures used for gas exchange in aquatic animals
What are external gills?
project from the body surface
Why are external gills efficient? But what is the problem with them too?
large surface area
direct contact with water requires no pump for bulk flow
Problem: easily damaged
What are internal gills?
bony fish gills
series of gill arches located on the sides of the head, covered by a flap of protective tissue, the operculum
What are gill arches?
composed of stacked rows of gill filaments
hundreds or thousands of thin sheet-like gill lamellae
What are lamellae
a bed of capillaries runs (to take up O2 and get rid of CO2) extend upward from each filament (sheet like gill
How do fish use internal gills?
water must be driven over gills
fish ventilate gills by opening and closing their mouths and a stiff gill flap (operculum)
What direction is water movement over gills?
unidirectional
What kind of system are fish gills?
countercurrent exchange system
lamellae oriented so blood and water flow in opposite directions
countercurrent flow makes fish gills extremely efficient in extracting oxygen - ensures large difference in O2 and CO2 concentrations between water and blood over entire respiratory surface
What is a countercurrent exchange system?
slight gradient between 2 solutions along entire length.
Both solutions cold at left and hot at right.
body solution cooled to cold
Blood flow to the gills (poor in O2)
blood flow from the gills (rich in O2)
What is a concurrent exchange system?
gradient between 2 solutions large at start, declines and disappears at end
body solution not cooled to cold
Why do fish have it tough?
(physics of water)
O2 content of air is 50x grater than in a smilier volume of water (O2 not very soluble in water)
O2 diffuses 8,000 times faster in air than in water
Water is 800x denser and 50x more viscous than air so harder to pump water across a respiratory surfaceW (viscous = resistance to flow)
How do fish cope with having to extract O2 from water?
unidirectional flow
countercurrent exchange
ectotherms, don’t need as much oxygen
What is the trachea?
form an extensive system of tubes that extend deep into the insect body
connect to the exterior though openings called spiracles which can be closed to minimize water loss by evaporation
What does the tracheal system transport and why?
transports air close enough to cells for gas exchange to take place directly so insects don’t require a circulatory system to breathe
How does the ventilation of human lung work?
The pressure inside the chest cavity is ~5mmHg less than atmospheric pressure (at rest negative pressure)
negative pressure keeps lungs from collapsing
Inhalation
humans inhale by contracting the diaphragm and rib muscles, causing diaphragm to move down and ribs out
further lowers already negative pressure, as it drops, lungs expand and air flows in along the pressure gradient
Exhalation
passive process driven by the elastic recoil of the lungs and chest wall as the diaphragm and rib muscles relax
What is tidal ventilation?
(breathing in and out)
What is the order of which air flows through body (lung anatomy)
enters though nose or mouth
pass through the larynx
to the trachea which branches into
the 2 primary bronchi which branch further into
secondary bronchi and eventually into
smaler diameter branchioles
What are alveoli?
cluster of sacs where the smallest bronchioles terminate
where gas exchange takes place
greatly increase the surface area for gas exchange
What do specialized epithelial cells do?
in the bronchi
secrete mucus that lines the bronchi surface to trap foreign particles, which are moved out of the lung by cilia
What is surfactant?
a component of this mucus film, reduces surface tension to allow alveoli to expand
How do birds use their lungs?
move air through their respiratory system in 2 cycles of ventilation providing a continuous supply of fresh air
continuous motion in same direction (in and out)
What do respiratory system of birds consist of?
rigid lungs
2 sets of air sacs
Explain the steps of using bird lungs
posterior air sacs expand, drawing in air through mouth and trachea
Posterior air sacs compress, pumping air into lung
Anterior air sacs expand, drawing air out of the lungs
Anterior air sacs compress, sending air out of the trachea and mouth
How are air channels arrange in bird lungs?
arranged perpendicular to blood capillaries allowing for crosscurrent flow for gas exchange
How is breathing homeostasis?
the medulla respiratory center sets the respiratory rhythm
during exercise, pO2 in blood decreases and pCO2 increases
chemoreceptors in medulla detect decreases in pH and increases in CO2
Chemoreceptors in the carotid arteries and aorta detect pH and O2 levels
What is the response for breathing in homeostasis?
response sent to diaphragm and other respiratory muscles (contract more frequently and more strongly)
this control system can maintain stable levels of O2 and CO2 in blood during intense exercise
CO2 partial pressure primary stimulus. pO2 normally high enough to nearly saturate hemoglobin
Is breathing under voluntary control or involuntary control?
both!
What is hemoglobin?
consists of 4 polypeptide subunits, each of which. binds a non-protein molecule called a heme group
What does each heme contain?
an iron that can bind to an oxygen molecule
thus each hemoglobin molecule can bind up to 4 oxygen molecules
(in red blood, cells 98.5% of O2 is bound to hemoglobin (poor solubility, hemoglobin acts as a carrier)
What is myoglobin?
found in muscle cells, binds one molecule of oxygen, stores oxygen for use by mitochondria of muscle cells and gives muscle their red color
How long did hemoglobin evolve?
over 670 million years ago
What is the pO2 leaving lungs and in muscles?
100mm Hg leaving lungs
40 mm Hg in muscles
What does a partial pressure do for oxygen delivery?
partial pressure difference creates a diffusion gradient that drives O2 unloading from hemoglobin in blood to tissues
What is the oxygen-hemoglobin equilibrium curve or oxygen dissociation curve?
plots the percentage saturation of hemoglobin in red blood cells versus pO2 in blood
sigmoidal, indicating cooperative binding
What does cooperative binding mean
binding oxygen to one subunit induces a conformation change making remaining subunits more likely to bind oxygen
makes system very sensitive to small pO2 changes
How is myoglobin oxygen dissociation curve different from hemoglobin’s?
at any give pO2, myoglobin binds oxygen more readily than hemoglobin. As a result, hemoglobin delivers oxygen to myoglobin in muscle tissues
How is feteal vs adult hemoglobin curve different? why?
left shifted relative to that of maternal hemoglobin
allows fetus to take up O2 from the mothers circulation
How is hemoglobin sensitive to pH and temperature?
pH decreases (more acidic) and temperature increases alter hemoglobin conformation, make it more likely to release O2 at all pO2 levels
called Bohr shift
What does the Bohr shift cause?
makes hemoglobin more likely to release oxygen during exercise or other conditions in which pCO2 is high, pH is low and tissues are under O2 stress
What is the effect of pH on dissociation curve?
pH decreases, often result of increased cell activity, cause hemoglobin’s O2 dissociation curve to shift right
hemoglobin then releases more O2 to the active cells
What is the function of the circulatory system?
function is to carry blood (closed systems) or hemolymph (open systems) into close contact with every cell in the body
What is the Bohr Shift equation?
CO2 + H2O ←→ H2CO3 ←→ H+ + HCO3-
What do the most sophisticated circulatory systems consist of?
hearts
arterites
capillaries
veins
animals may lack some or all of these
What are hearts?
one or more pumps in a circulatory system
What are arteries?
tough thick walled vessels that carry blood away from the heart under high pressure
What are capillaries?
vessels whose walls are just one cell layer thick, allowing gases and other molecules to diffuse efficiently with tissues in networks called capillary beds
What are veins
vessels that return blood to the heart under low pressure
What are 2 types of circulatory systems?
open
closed
What is an open circulatory system?
blood flows through a vessel with muscular thickenings that act as a pump
blood empties into an open body cavity to. supply the tissues with nutrients and is return to the circulation
What has open circulatory system
insects and many mollusks (clams)
What is hemolymph?
pumped by one or more hearts into blood vessels that empty into the body cavity to bathe tissues
returns to heart when heart relaxes and its internal pressure is lower than the body cavity
transports wastes and nutrients as well as oxygen but ability to direct flow to specific tissues is limited
What is a closed circulatory system?
blood flows through connected blood vessels, pumped by muscular hearts
blood flows through vessels to supply tissues with nutrients
How do vessels maintain blood flow through the circuit and still have gas exchange?
very large total capillary cross sectional area
What are arteries?
large high pressure vessels that carry blood away from heart
walls are tough and thick, containing muscle and elastic layers composed of elastin and collagen
What are arterioles?
the smallest arteries, have smooth muscle fibers in their walls wrapped around their circumference that act asa sphincters to allow diameter to be regulated by signals from the nervous system, to increase or decrease blood flow as needed
What are capillaries?
smallest, thinnest, vessels
walls one cell layer thick, allowing gases, nutrients, and wastes to be exchanged between blood and other tissues in dense networks called capillary beds
What are venules?
smallest veins that lead to veins
after passing through capillaries, blood enters venues
What are veins?
carry deoxygenated blood back to the heart; blood pressure is relatively low
much thinner walls and much larger interior diameters than arteries
How do large valves relate to the speed of blood? What prevents back flow?
large veins are compressed by muscle activity in the extremities which helps speed return of blood to heart
contain one-way valves (thing flaps of tissues) to prevent blood back flow
Why do capillaries not rupture?
Blood pressure is lower than in any other type of blood vessel
What do vertebrate hearts contain?
one heart
at least 2 chambers
What do fish hearts contain?
one circuit (heart to gills to body to heart)
2 chambers
What do amphibian hearts contain?
2 circuits
3 chambered heart (2 atria, 1 ventricle)
mixed pulmonary (to the lungs) and systemic (to the body) circulation
What do the hearts of birds and mammals contain?
2 circuits
4 chambered heart (2 atria, 2 ventricles)
separate pulmonary and systemic circulations
How do fish heart and circulatory system work?
deoxygenated blood enters the atrium from a main vein and is pumped into the ventricle
Deoxygenated blood is pumped from the ventricle into a main artery
What is the problem with fish heart and circulatory system?
gill capillaries small
large resistance to flow
much of blood pressure therefore lost in gills, limits flow of oxygenated blood to body tissues
How do amphibian heart and circulatory system work?
deoxygenated blood from tissues enters the right atrium from a major vein and is pumped into the single centricle
oxygenated blood from the lungs enters the left atrium and is pumped into the ventricle
mixed oxygenated and deoxygenated blood is pumped out of the common ventricle into separate arteries leading to the lungs and tissues
What is the problem with amphibian heart and circulatory system?
oxygenated and deoxygenated blood mixed in heart
How do amphibian hearts compare to fish hearts?
oxygenated blood pumped to body at higher pressure than in fish
Gas Exchange, O2 delivery improved
metabolic rate and activity higher
Is there separation of pulmonary and systemic circulation in mammalian hearts? (includes crocodile and alligator) Why?
yes
allows pumping blood to lungs at low pressure
increasing O2 uptake
pumping blood to body at high pressure
How do mammalian hearts compare to fish and amphibian hearts?
still higher possible metabolic rates and activity
More O2 for energy use by body tissues
How does blood circulate through the heart in a human? (specifically use deoxygenated and oxygenated blood)
Deoxygenated blood enters the right atrium from the inferior and superior vena cavae
deoxygenated blood passes through the right AV valve and enters the right ventricle
deoxygenated blood is pumped into the pulmonary arteries through the pulmonary valve
oxygenated blood returns from the lungs through the pulmonary veins to the left atrium
oxygenated blood enters the left ventricle through the left AV valve
Oxygenated blood is pumped by the left ventricle through the aortic valve into the systemic circulation
Why are walls of the right ventricle thinner than the left?
blood exits at lower pressure, allowing for greater oxygenation (my note: also only pumping to lungs)
What is the pulmonary circuit?
moves blood between heart and lungs
transports deoxygenated blood to the lungs to absorb oxygen and release carbon dioxide,
oxygenated blood then flows back to the heart
What parts of the human heart are in the pulmonary circuit?
venae cavae
right atrium
(through AV valve to) right ventricle
pulmonary arteries & valve
pulmonary viens
left atrium (receiving oxygenated blood)
What is the systemic circuit?
move blood between the heart and the rest of the body
What parts of the human heart are in the systemic circuit?
left atrium (contracting to send oxygenate blood)
(through AV valve to) to left ventricle
aortic valve
Why are the left ventricle walls thick?
so blood is ejected at high pressure
also gas exchange in lungs and tissues is rapid relative to rate of blood flow
What causes heart murmurs?
when blood flow is disturbed (turbulent) due to structural defects in heart valves or abnormal passages for blood flow in the heart
What is diastole?
relaxation phase, ventricular filling
atrioventricular valves open
blood flows from atria to ventricles (70% of filling)
atrial contraction (30%) more filling of ventricles)
in diastole, the atria contract, filling the ventricles with blood
What is systole?
contraction phase
left and right atrioventricular valves close (1st sound “lub”)
ventricular contraction begins
aortic and pulmonary valves opens
blood flows to aorta and lungs as ventricles contract
aortic and pulmonary valves close (2nd sound, “dub”)
In systole, the ventricles contract, pumping blood out of the heart
When do cardiac muscle cells of the atria and ventricles contract?
contraction a coordinated fashion
atria during diastole
ventricles during systole
What do specialized cardiac cells in the SA node do?
act as the heart’s pacemaker
they fire action potentials without input
What are cardiac muscles connected by? Why?
gap junctions
allowing the action potential to pass cell-to-cell throughout the heart
Why do the ventricles and the atria contract independently?
the atria are not electrically coupled to the ventricles
What are the steps of electrical activation of the heart?
pacemaker generates action potentials that spread through the atria. the atria contract
signals from the pacemaker reach the AV node, which is activated and fires (also delays the signal slightly allowing ventricles to fill)
action potentials are transmitted through a set of modified muscle fibers to the base of the ventricles
depolarization spreads from the modified muscle fibers through the entire ventricle → ventricles contract
How do sympathetic and parasympathetic stimulations affect heart rate?
sympathetic - speeds up heart rate
parasympathetic - slows down heart rate
Note 
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