Download Resp. Circ. Systems

Lecture #18
Date _____
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Chapter 42 ~
Circulation and Gas
Exchange
Overview
Questioning
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What do you think is important for gas
exchange to occur?
What will allow for greater gas exchange?
Gas exchange
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Uptake of O2 and discharge of CO2
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All gas exchange occurs through diffusion
Rates depend on surface area and strength of
concentration gradients (surface area:volume ratio
needs to be large)
Respiratory surfaces – thin and have large surface area,
moist, O2 and CO2 are dissolved in water
Depends on lifestyle/metabolic demands (aquatic,
terrestrial, ecto/endotherm)
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Aquatic: •gills (ventilation & countercurrent exchange)
Terrestrial: •tracheal systems & lungs
Question
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How do you think simple organisms
respire? What is their body organization
like?
More complex organisms?
Diversity of gas exchange
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Bacteria/Protists – gas exchange across entire
organism
Sponges, cnidarians, flatworms – direct diffusion
Earthworm/amphibians – breath through skin
Birds – lungs with air sacs (1-way flow of air)
More complex organisms – highly branched and
folded respiratory organ (increase surface area)
Ventilation – current of water across
gills so fresh O2 is near the gills
Countercurrent
Exchange
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Countercurrent exchange – allows diffusion to
occur along the entire length of capillary
80% efficient
On land, gills would dry out and collapse (need
moist surface for diffusion)
Question
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What are the advantages of living on land
vs. living in water when it comes to
respiration?
Advantages of air over water
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Higher percentage of O2 (210ml vs 6 ml per
liter)
No ventilation required (gas diffuses faster)
However, respiratory surface has to be
internal to keep diffusion surfaces moist
TRACHEAL TUBES
-Air tubes bring O2 directly to cells
(no circulatory system involvement)
-Diffusion can move the air through or
-Flight muscles can flex tubes
(ventilation) to transport O2 more
efficiently
Lungs - Mammalian respiratory
systems – circulation involved
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Nasal cavity
Pharynx
Larynx (upper part of
respiratory tract) – vocal
cords
Trachea (windpipe)
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Bronchi (tube to lungs)
Bronchioles
Alveoli (air sacs)
Diaphragm (breathing muscle)
Warm-up Questions
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What allows for more efficient diffusion?
What strategies do different organisms use
to respire?
List the organs of the respiratory system in
order.
Respiratory Video
Question
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Describe the process of breathing in
humans.
Breathing
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Positive pressure breathing: pushes air into lungs (frogs)
Negative pressure breathing: pulls air into lungs (mammals)
Inhalation: diaphragm contraction; Exhalation: diaphragm relaxation
Tidal volume: amount of air inhaled and exhaled with each breath (500ml)
Vital capacity: maximum tidal volume during forced breathing (4L)
Residual air – increases with age or disease – efficiency goes down
Regulating breathing
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Regulation: monitors CO2
levels in blood (medulla
oblongata)
CO2 + water = carbonic
acid = lowers pH
Slight drop in pH triggers a
breathing response
O2 levels have little effect
on breathing unless O2 is
severely depleted
Breathing Facts
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We breathe 22,000 times a day
Hiccups – involuntary contractions of the
diaphragm
Sneeze – irritant in respiratory tract your body is
trying to get rid of
Yawn – not getting enough O2 to body (tiredness)
Fetuses have been seen yawning
Reading about yawning will make you yawn
Yawn Video
Next Step
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We have the oxygen in our lungs
How do we get it to our cells?
Two issues
– Every cell needs gas exchange
– Only 4.5 ml of oxygen will dissolve into
blood at 1 time (very inefficient) – need
help
Respiratory pigments: gas transport
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Needed for efficient transport of
oxygen
Oxygen transportHemocyanin: found in hemolymph
of arthropods and mollusks (Cu) –
blue blood
Hemoglobin: vertebrates (Fe)
Carbon dioxide transportBlood plasma (7%)
Hemoglobin (23%)
Bicarbonate ions (70%)
Deep-diving air-breathersMyoglobin: oxygen storing protein
Protein review
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Cooperativity – the
binding of one oxygen
to hemoglobin, causes
the other 3 active sites
to have a HIGHER
AFFINITY for
oxygen
Similar to allosteric
activation
What do you think the
optimal pH is for
hemoglobin?
How does hemoglobin load/unload?
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Individual whiteboard
– Partial pressure = percentage gas X 760 mmHg
– Write the partial pressures of O2 and CO2 in these
locations
• Inhaled air
• Blood leaving the alveoli
• Blood entering capillaries near body cells
• Blood leaving capillaries of the body cells
• Blood nearing the alveoli
• Exhaled air
Warm-up
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Describe how hemoglobin binds and
releases oxygen.
What is the purpose of the circulatory
system?
Bohr shift
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Hemoglobin releases oxygen (has less affinity
for oxygen) at lower partial pressure for oxygen
and at lower pH’s (more CO2)
Circulation system evolution, I
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Gastrovascular cavity (cnidarians, flatworms)
Open circulatory •hemolymph (blood & interstitial fluid) •sinuses
(spaces surrounding organs)
Closed circulatory: blood confined to vessels
Cardiovascular system •heart (atria/ventricles) •blood vessels
(arteries, arterioles, capillary beds, venules, veins) •blood
(circulatory fluid)
Gastrovascular Cavity
Circulation system evolution, II
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Fish: 2-chambered heart; single circuit of blood flow
Amphibians: 3-chambered heart; 2 circuits of blood flowpulmocutaneous (lungs and skin); systemic (some mixing)
Mammals: 4-chambered heart; double circulation; complete
separation between oxygen-rich and oxygen poor blood
Double circulation
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From right ventricle to lungs
via pulmonary arteries through
semilunar valve (pulmonary
circulation)
Capillary beds in lungs to left
atrium via pulmonary veins
Left atrium to left ventricle
(through atrioventricular valve)
to aorta
Aorta to coronary arteries; then
systemic circulation
Back to heart via two venae
cavae (superior and inferior);
right atrium
The mammalian heart
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Cardiac cycle: sequence of
filling and pumping
Systole- contraction
Diastole- relaxation
Cardiac output: volume of
blood per minute
Heart rate- number of beats per
minute
Stroke volume- amount of blood
pumped with each contraction
Pulse: rhythmic stretching of
arteries by heart contraction
Tricuspid Valve
Aortic Valve
Pulmonary Valve
Mitral Valve
The heartbeat
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Sinoatrial (SA) node (“pacemaker”): sets rate and timing of cardiac
contraction by generating electrical signals
Atrioventricular (AV) node: relay point (0.1 second delay to ensure
atria empty) spreading impulse to walls of ventricles
Electrocardiogram (ECG or EKG)
Why do the blood vessels have
different structure?
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Capillaries
•endothelium (lining of
smooth cells = less resistance to
blood flow); basement membrane –
cell attachment & selective
permeability
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Arteries
•thick connective tissue;
thick smooth muscle; endothelium;
basement membrane
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Veins
•thin connective tissue; thin
smooth muscle; endothelium;
basement membrane
Blood flow in veins
Why is important to maintain blood
pressure?
Water Potential Review
Diffusion
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O2 and CO2 passively diffuse
Other solutes can travel between cells
through bulk flow (caused by pressure)
Arterial end of a capillary – net diffusion is
out of capillary
Venous end – net diffusion is in
85% of fluid that leaves the blood vessel
will return at the venous end (other 15 %
will be recycled by the lymphatic system)
The lymphatic system
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Lymphatic system: system of
vessels and lymph nodes,
separate from the circulatory
system, that returns fluid and
protein to blood
Lymph: colorless fluid, derived
from interstitial fluid
Lymph nodes: filter lymph and
help attack viruses and bacteria
Body defense / immunity
Blood
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Plasma: liquid matrix of blood in which cells are suspended (90% water)
Erythrocytes (RBCs): transport O2 via hemoglobin
Leukocytes (WBCs): defense and immunity
Platelets: clotting
Stem cells: pluripotent cells in the red marrow of bones
Blood clotting: fibrinogen (inactive)/ fibrin (active); hemophilia; thrombus
(clot)
Cardiovascular disease
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Cardiovascular disease (>50% of
all deaths)
Heart attack- death of cardiac
tissue due to coronary blockage
Stroke- death of nervous tissue in
brain due to arterial blockage
Atherosclerosis: arterial plaques
deposits
Arteriosclerosis: plaque hardening
by calcium deposits
Hypertension: high blood pressure
Hypercholesterolemia:
LDL, HDL
LDL vs HDL
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To Decrease LDL, try:
minimize the intake of
Saturated Fats
minimize the intake of Trans
Fats
include foods with Soluble
Fiber
include Soy Proteins
include Omega 3 -rich food
such as Salmon, Fish Oils and
Flaxseed
include Garlic
keep a healthy weight
keep an active lifestyle
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To Increase HDL, try:
stay active
reduce total fat intake to <30%
quit smoking
include Omega 3 -rich food
such as Salmon and Fish Oils
moderate amount of Red Wine
may help
Practice
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Discuss the processes of exchange of O2
and CO2 that occur at the alveoli and
muscle cells of mammals. Include in your
answer a description of the transport of
these gases in the blood.