Transcript Nerve activates contraction

CHAPTER 42
CIRCULATION AND GAS
EXCHANGE
Word List:
aorta - the biggest and longest artery (a blood vessel carrying blood away from the heart) in the body. It
carries oxygen-rich blood from the left ventricle of the heart to the body.
inferior vena cava - a large vein (a blood vessel carrying blood to the heart) that carries oxygen-poor blood
to the right atrium from the lower half of the body.
left atrium - the left upper chamber of the heart. It receives oxygen-rich blood from the lungs via the
pulmonary vein.
left ventricle - the left lower chamber of the heart. It pumps the blood through the aortic valve into the aorta.
mitral valve - the valve between the left atrium and the left ventricle. It prevents the back-flow of blood from
the ventricle to the atrium.
pulmonary artery - the blood vessel that carries oxygen-poor blood from the right ventricle of the heart to
the lungs.
pulmonary valve - the flaps between the right ventricle and the pulmonary artery. When the ventricle
contracts, the valve opens, causing blood to rush into the pulmonary artery. When the ventricle relaxes, the
valves close, preventing the back-flow of blood from the pulmonary artery to the right atrium.
pulmonary vein - the blood vessel that carries oxygen-rich blood from the lungs to the left atrium of the
heart.
right atrium - the right upper chamber of the heart. It receives oxygen-poor blood from the body through the
inferior vena cava and the superior vena cava.
right ventricle - the right lower chamber of the heart. It pumps the blood into the pulmonary artery.
septum - the muscular wall that separates the left and right sides of the heart.
superior vena cava - a large vein that carries oxygen-poor blood to the right atrium from the upper parts of
the body.
tricuspid valve - the flaps between the right atrium and the right ventricle. It is composed of three leaf-like
parts and prevents the back-flow of blood from the ventricle to the atrium.
Why is there a circulatory system?
• Get nutrients/wastes in/out of cells
• Diffusion – 100 sec. -> 1mm; 3hrs. -> 1cm! NOT EFFICIENT.
• Diffusion - needs thin, flat bodies - 2 cell layer or diploblastic - in
hydra (cnidaria), branching Gastrovascular cavity and flat/thin
body in planaria (Platyhelminthes)
Why is there a circulatory system?
• Circulatory system in all higher phyla:
• Heart - why?, blood vessels - closed or open system,
circulatory fluid - hemolymph/blood
•Closed circulatory system, blood is confined to vessels
• Open circulatory system- blood bathes organs
and is distinct from the interstitial fluid (liquid bathing
directly. There is no distinction between blood and
cells). Earthworms - heart is a tube.
interstitial fluid, collectively called hemolymph.
•earthworms, squid, octopuses, and vertebrates
• insects, other arthropods, and most mollusks
•Open circulatory system, hemolymph flows through open vessels and
is not distinct from the interstitial fluid. Heart (long tube) pumps fluid
into body spacs called sinuses and fluid reaches back through openings
called ostia.
•Molluscs, arthropods, echinoderms like seastars
Fig. 42.2a
What are the advantages
and disadvantages of
open circulation?
-less energy needed to
work it, build, and
maintain
-serves as skeleton in
molluscs
-less effective at
transport
What are the advantages
of closed circulation?
-very effective at
transport
-higher hydrostatic
pressure in vessels
-great for increased
metabolic need/larger
size
Cardiovascular system -Vertebrates
• The closed circulatory system
• Heart consists of atria, (receive blood returning to the heart),
ventricles, (pump blood out of the heart).
• Arteries (away from heart to capillaries), veins (towards heart
from capillaries), and capillaries - blood vessels.
• Arteries -> arterioles -> capillary bed -> venules -> veins
• Need a mechanism for oxygenating the blood (lungs, skin, gills)
• Fish heart has two chambers, one atrium and
one ventricle. One loop of circulation.
• Ventricle to the gills (the gill circulation) -> For
Oxygenation
• Systemic (body) circulation
- Oxygenated blood -> body
-Deoxygenated blood -> heart
Fig. 42.3a
Frogs and other amphibians - a three-chambered heart
with two atria and one ventricle.
Two loops of circulation
• Pulmocutaneous
-Deoxygenated blood ->
taken to lung + skin for
oxygenation
• Systemic circulations
- Oxygenated blood -> body
- Deoxygenated blood -> heart
Fig. 42.3b
• Reptiles - double circulation with pulmonary (lung)
and systemic circuits.
• less mixing of oxygen-rich and oxygen-poor blood
(ventricle is partially divided).
• Crocodiles, birds, and mammals- the ventricle is
completely divided
• Left – Oxygenated Blood
• Right – Deoxygeneated blood
• Double circulation- meets needs of
endotherm (higher metabolic rate)
Fig. 42.3c
• Right ventricle -> pulmonary
artery - >
• Lungs - > capillaries load up
oxygen, unloads CO2 ->
pulmonary veins ->
• Left atrium - > (pulmonary
circulation)
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• Left Ventricle -> Aorta ->
arteries -> capillaries near body
cells (systemic circulation)
• -cells get oxygen and give back
CO2 to blood in capillaries
• Capillaries -> venules -> veins > venacava
• Right Atrium
• -> Right ventricle
• DOUBLE CIRCULATION
Fig. 42.5
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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• Coronary arteriessupply the heart!
• Cardiac cycle - one complete sequence of
contraction (systole) and relaxation (diastole).
• Cardiac output (L/min.) depends on two factors:
the rate of contraction or heart rate (number of
beats per second) and stroke volume (the amount
of blood pumped by the left ventricle in each
contraction).
• The average stroke volume for a human is about 75 mL.
• The typical resting cardiac output, about 5.25 L / min, is
about equivalent to the total volume of blood in the
human body.
• Cardiac output can increase about fivefold during heavy
exercise.
• Heart rate can be measured indirectly by measuring your
pulse - the rhythmic stretching of arteries caused by the
pressure of blood pumped by the ventricles.
• Four valves in the heart, each consisting of flaps of
connective tissue, prevent backflow and keep blood
moving
the heart
correct
direction.
•Theinfirst
sound
(“lub”) is created by the
recoil of blood against the closed AV valves.
• Atrioventricular (AV) valve – (A and V)
•The second sound (“dup”) is the recoil of blood
• Two sets of Semilunar valves- (LV and Aorta; RV and
against the semilunar valves.
Pulmonary artery)
•Defect in valve= heart murmur (swoosh, clicks)
•Cardiac
muscle
cells
electrically
by intercalated
• The
cardiac
cycle
isare
regulated
by coupled
electrical
impulses
disksradiate
between
adjacent cells.
that
throughout
the heart.
•Stimulus
spreads
to Atrioventricular
theand
junction
• Pacemaker
– Sinoatrial
(SA) Node -(AV)
sets node
heart at
rate
of pumpingright atrium
and right
ventricle;
Signal waits
for 0.1muscle
sec here
in right
atrium;
Self- excitation
of heart
(allows
empty fully
before ventricles contract)
starts atrium
here(myogenic
vs neurogenic)
•Purkinje fibers then carry contraction impulse to rest of heart
Fig. 42.7
• Currents can be detected by electrodes and
recorded as an electrocardiogram (ECG or
EKG).
What influences heart rate?
• Exercise
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• Sex
• Age
• Flight or fight response
• Temperature
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Structural differences of arteries, veins, and
capillaries correlate with their functions
Outside- a layer of connective tissue with elastic fibers
allows the vessel to stretch and recoil.
Middle layer -smooth muscle and more elastic fibers.
Endothelium- Lining the lumen (cavity), a single layer of
flattened cells - capillaries have only this layer- WHY???
Thick middle layermaintains pressure in
vessels even if heart is
relaxed
Thin middle layer- low
velocity and pressure as
blood flows back
• Will blood flow faster in a big fat aorta or thin capillaries
•Blood flows >1000 times faster in Aorta than capillaries
•Will blood flow in veins be faster/slower than capillaries?
• Faster- flow depends on total cross sectional area
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Fig. 42.9
Blood flow review
• Heart contracts (systole)
• Aorta-> Arteries ->
Arterioles ->
• Capillaries
• Venules -> Veins ->
Venacava
• Heart relaxes (diastole)
• Blood back to heart
The elastic walls of the
 What is a diastole?
arteries snap back during
 What is a systole?
diastole, but the heart
 Blood pressure, the
contracts again before
hydrostatic force that
enough blood has flowed
blood exerts against
into the arterioles to
vessel walls, is much
completely relieve pressure
greater in arteries than in
in the arteries- the diastolic
veins and is highest in
pressure (80 mmHg)
arteries when the heart
This is called peripheral
contracts during
resistance
ventricular systole,
 Blood pressure
creating the systolic
depends on peripheral
pressure (120 mm Hg)
resistance and cardiac
Fig. 42.10
output (hmmm???)
• A sphygmomanometer measures blood pressure
(depends on cardiac output and peripheral resistance;
gravity, stress, exercise, age, sex…???)
• 120 mm Hg at systole and 70 mm Hg at diastole.
Fig. 42.11
• Capillaries have sphincters- control flow
• Solutes and water leave the capillaries and move into
space around cells (interstitial fluid)- WHY?
Fig. 42.12
•85% of the fluid that leaves reenters
•Remaining 15% is eventually returned to the
blood by the vessels of the lymphatic system.
Fig. 42.13
The lymphatic system returns fluid to the
blood and aids in body defense
Blood has RBCs (erythrocytes) and WBCs
(leukocytes), and platelets (clotting) as
cellular elements
Fluid in blood = Plasma (50%)
Has water, ions, proteins like
immunoglobins (antibodies),
Blood transports nutrients, gases,
wastes,hormones
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Blood is made in bone marrow
from adult stem cells
EPO - hormone stimulates RBC
production (doping)
CHAPTER 42
GAS EXCHANGE
Fig. 42.18
Gas exchange is the uptake of O2 and the
discharge of CO2
Aquatic
.
Simple
.
Diffusion
“Aquatic”
“Aquatic”
Skin –
respiratory
organ!
Gills–
respiratory
organ
“Terrestrial”
“Aquatic”
“Terrestrial”
Tracheae–
respiratory
organs
Gills–
respiratory
organ
Lungs–
respiratory
organs
• Gills = Aquatic environment; need ventilation
(movement of water over gills)
Fig. 42.19
• Fish Gills =Counter current exchange -water
moves opposite to blood in gills
• Blood meets water with
MORE oxygen at every
point. Diffusion gradient all
Fig. 42.20
along the capillary favors
oxygen exchange
•The tracheal system of insects is composed of air tubes
that branch throughout the body (why is this different
from lungs?).
•WHY AIR IS BETTER THAN H2O
•More O2 in air than in water (less dissolved O2 in
warm/salty ocean water)
•Gases diffuse faster in air – less ventilation
•Air is lighter
•Problem – evaporation; Solution – Closed Circulatory
LUNGS: Spiders, terrestrial snails, and vertebrates
• System of branching tubes: trachea, bronchi, bronchioles,
alveoli
• Respiratory surface – capillary network surrounding alveoli
• Circulatory system transports gases between the lungs and
the rest of the body.
Negative pressure breathing.
• This works like a suction pump, pulling air instead of pushing it
into the lungs. Muscle action (diaphgram and rib muscles)
changes the volume of the rib cage and the chest cavity,
and the lungs
follow suit.
Fig. 42.24
HOW MUCH AIR???
• The volume of air an animal inhales and exhales with
each breath is called tidal volume.
• About 500 mL in resting humans.
• The maximum tidal volume during forced breathing is
the vital capacity,
• about 3.4 L and 4.8 L for college-age females and
males, respectively.
• The lungs hold more air than the vital capacity, but some air
remains in the lungs, the residual volume, because the
alveoli do not completely collapse (stale and fresh air mix)
• Besides lungs, birds have eight or nine air sacs that do not
function directly in gas exchange, but act as bellows that keep
air flowing through the lungs. Birds can carry more oxygen =
better performance under some conditions such as???
Fig. 42.25
Control centers in the brain regulate
breathing
• Breathing control
centers are located in
two brain regions, the
medulla oblongata and
the pons.
• medulla and pons -trigger
contraction of the
diaphragm and rib muscles
(rate of breathing).
• Stretch receptors in ribs
inhibits the breathing
center (Negative-feedback
mechanism)
• Sensors in aorta, and other
arteries detect O2 changes
and signal medulla to
What are
alveoli?
Gases diffuse down pressure gradients
• Partial pressure- the contribution of a particular gas
to the overall total pressure.
• At sea level, the atmosphere pressure = 760 mm Hg.
• 21% oxygen; the partial pressure of oxygen (abbreviated
PO2) is 0.21 x 760, or about 160 mm Hg.
• The partial pressure of CO2 is only 0.23 mm Hg.
Respiratory pigments transport gases and
help buffer the blood
• A person exercising consumes almost 2 L of O2 per
minute, but at normal body temperature and air pressure,
only 4.5 mL of O2 can dissolve in a liter of blood in the
lungs.
• If 80% of the dissolved O2 were delivered to the tissues
(an unrealistically high percentage), the heart would need
to pump 500 L of blood per minute - a ton every 2
minutes.
• O2 is bound to special proteins called respiratory
pigments instead of dissolved in solution.
Hemocyanin Arthropods
Hemoglobin -Vertebrates
• Coopertive binding of Oxygen To Hemoglobin: Dissociation Curve and Bohr’s
Shift
• Hemoglobin protein has 4 subunits- binding of one subunit to oxygen causes
other 3 subunits to bind O2 faster
• Release of one oxygen also leads to release of the other 3 co-operatively
Fig. 42.29
Fig. 42.29, continued
What does pollution do to your lungs?
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Deep-diving air-breathers stockpile oxygen
and deplete it slowly
Fig. 42.30
• Diving vertebrates not only start a dive with a
relatively large O2 stockpile, but they also have
adaptations that conserve O2.
• They swim with little muscular effort and often use
buoyancy changes to glide passively upward or
downward.
• Their heart rate and O2 consumption rate decreases
during the dive and most blood is routed to the brain,
spinal cord, eyes, adrenal glands, and placenta (in
pregnant seals).
• Blood supply is restricted or even shut off to the
muscles, and the muscles can continue to derive ATP
from fermentation after their internal O2 stores are
depleted.