Transcript chapter 42 - MagnusonScience

Circulation and Gas
Exchange
• Cells exchange material with
external environment.
• Respiration - aerobic organisms
take in O2, release CO2.
• Cells produce waste (nitrogenous)
needs to be removed; need to
obtain nutrients.
http://home.earthlink.net/~dayvdanls/FormingATP.GIF
• Simple organisms (protozoans,
cnidarians, sponges) - small body
size, close proximity of cells to
external environment allows direct
exchange of materials.
• True for roundworms, flatworms.
• Large multicellular organisms no
passive diffusion between cells and
environment - circulatory system to
move fluids in body to carry
nutrients to tissues, wastes away.
• Circulatory system - blood, heart,
vessels that carry blood throughout
body.
http://www.bodyandmind.co.za/healthweb/gifs/circulatory%20system%20copy.gif
• Circulatory systems can be closed
(blood always contained within
blood vessels) or open (blood in at
least part of body mixes directly
with tissues in open sinuses).
Invertebrate Circulatory
Systems
• Most cells in earthworms (annelids)
not in direct contact with external
environment.
• Internal closed circulatory system
indirectly brings materials from
external environment to cells.
• Blood travels toward anterior heart
through dorsal blood vessels.
http://biology.unm.edu/ccouncil/Biology_203/Summaries/Protostomes.htm
• 5 aortic arches (like hearts) force
blood to ventral vessel, carries
blood to posterior, up to complete
circuit.
• Blood carries O2, CO2 between cells
and skin of earthworm where gas
exchange occurs.
• Circulates nutrients from digestive
tract to rest of body.
http://www.nrwmg.vic.gov.au/images/ana1.gif
• Arthropods, mollusks utilize open
circulatory system - blood flows
through dorsal vessel, out into
spaces called sinuses.
• In sinuses, blood not enclosed in
blood vessels but directly bathes
cells.
http://biology.unm.edu/ccouncil/Biology_203/Images/Protostomes/clam_labeled_1.jpg
• Air exchange in arthropods is
accomplished through tracheal
system of air tubes; heart is simple
beating tube.
• Closed system more efficient than
open.
http://www.emc.maricopa.edu/faculty/farabee/biobk/insectexch.gif
Vertebrate Circulatory
Systems
• Vertebrate system closed chambered heart that pumps blood
through arteries that lead away
from heart to capillaries.
• Capillaries - extremely small vessels
in tissues where exchange of
material between circulation,
tissues occurs.
http://bio.rutgers.edu/~gb102/lab_10/circuits_du.jpg
• From capillaries, blood carried back
to heart through veins.
• Valves in heart, veins help to
prevent blood from flowing
backward through system.
• Atria in heart receive blood from
body; ventricles - muscular
chambers that pump blood out
through arteries to body.
http://www.starsandseas.com/SAS_Images/SAS_Physiol_Images/SAS%20cardiopics/heart_valves.jpg
• Fish heart - 2 main chambers, 1
atrium, 1 ventricle.
• Blood pumped from ventricle to gills
(gill circulation) where it picks up
O2, disposes of CO2 across capillary
walls.
• Frogs - 3-chambered heart with 2
atria, 1 ventricle.
• Blood pumped through 2 systems.
• Ventricle pumps blood to lungs +
rest of body at same time through
2 major arteries.
http://academic.emporia.edu/sievertl/verstruc/frogin.JPG
• Allows oxygenated blood from lungs
+ deoxygenated blood from body to
mix in ventricle before delivered
back to body.
• Allows higher arterial pressure in
blood pumped to tissue.
• Reptiles - double circulation with
pulmonary (lung) and systemic
circuits.
• Crocodilians, birds, mammals, ventricle completely divided into
separate right and left chambers.
• Left side receives, pumps only
oxygen-rich blood; right side
handles only oxygen-poor blood.
http://kvhs.nbed.nb.ca/gallant/biology/reptile_heart.jpg
• Pumping blood through capillary bed
with large number of small vessels
creates resistance.
• Heart creates pressure in
circulatory system when it
contracts to force blood through
system.
• Highest pressure in blood vessels
found in arteries leading away from
heart to capillaries.
http://www.brianmac.demon.co.uk/heartsec.gif
• Birds, mammals (endotherms)
require more energy more efficient
circulation.
• Needs to be complete separation of
blood flow to lungs and other
tissues of body.
• Birds, mammals evolved hearts with
4 chambers: 2 atria, 2 ventricles.
http://library.thinkquest.org/19347/media/Heart.jpg
• Mammal hearts -2 pumps in one.
• 1 atrium, 1 ventricle involved in
pumping blood to lungs pulmonary
circulation.
• Other atrium and ventricle involved
with pumping blood to rest of body
through systemic circulation.
• Avoids mixing of oxygenated and
deoxygenated blood; allows high
arterial pressure needed for fast
delivery of material to tissue.
http://www.baa.duke.edu/companat/Heart/bat/tinybat.jpg
The heart
• Human heart - 4-chambered pump
with 2 collecting chambers (atria
and ventricles).
• R ventricle pumps deoxygenated
blood to lungs through pulmonary
artery.
• Oxygenated blood returns to heart
through pulmonary vein to L atrium.
Fig. 42.5
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• From there it passes to L ventricle,
pumped through aorta and arteries
to rest of body.
• 4 valves that help prevent backflow
into each chamber.
• Between each atrium and ventricle atrioventricular (AV) valve which
keeps blood from flowing back into
atria when ventricles contract.
http://webanatomy.net/histology/cardiac/av_valve.jpg
• 2 sets of semilunar valves, 1
between L ventricle and aorta,
other between R ventricle and
pulmonary artery, prevent backflow
from vessels into ventricles while
they are relaxing.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 42.6
• Heart formed from 2 weaker atria,
2 stronger ventricles.
• Cardiac cycle - 1 complete sequence
of pumping, as heart contracts, and
filling, as it relaxes and chambers
fill with blood.
• Contraction = systole
• Relaxation = diastole
http://www.bhf.org.uk/appg/furniture/heart.jpg
• Heart sounds made from opening
and closing of valves.
• 1st sound made from recoil of blood
against closed AV valves (“lub”)
• 2nd sound made from recoil of blood
against semilunar valves. (“dup”)
• Heart murmurs result of incomplete
valve closure resulting in swishing
noise.
http://www.nhlbi.nih.gov/health/dci/images/heart_murmur.jpg
• Heart made of cardiac skeletal
muscle.
• Striated, involuntary.
• Cytoplasm of each cell connected to
next to allow electrical impulses
(action potentials) to pass through
and cause contraction of atria and
ventricles in unison.
http://cellbio.utmb.edu/microanatomy/muscle/muscle12.jpg
• Allows them to not need signal from
nervous system.
• Cells synchronized by sinoatrial
(SA) node (located in R atrium), or
pacemaker, which sets rate and
timing at which all cardiac muscle
cells contract.
http://www.sjm.com/assets/popups/electsys.gif
• Cells maintain negative membrane
potential across plasma membrane resting potential.
• Wave of depolarization by action
potential triggers muscle
contraction.
• In SA node, pacemaker cells
spontaneously depolarize membrane
potential at steady rate on their
own, causing voltage-gated channels
in pacemaker to open.
• When action potential initiated in
pacemaker cells, spreads rapidly
throughout both atria to cause
atria to contract together.
• Action potential cannot pass to
ventricular cells - no direct path
between atria and ventricles (no
cell to cell connections).
http://www.lib.mcg.edu/edu/eshuphysio/program/section3/3ch2/3ch2img/page10.jpg
• Impulse carried through
atrioventricular (AV) node from
atria to ventricles, then through
bundle of His and Purkinje fibers all carry action potential to
ventricles where it will spread
throughout cardiac muscle rapidly
from cell to cell.
http://www.owensboro.kctcs.edu/gcaplan/anat2/notes/Image345.gif
• Passage of impulse through AV node
delays impulse so that timing of
contraction by ventricles coincides
with completion of atrial
contraction.
http://images.med.cornell.edu/body/greystone/em_0018.jpg
• Heart rate regulated by
sympathetic and parasympathetic
nervous systems (both part of
autonomic nervous system).
• Sympathetic system causes heart
rate to increase by acting on
sinoatrial node pacemaker through
epinephrine.
http://www.becomehealthynow.com/images/organs/nervous/sympathetic.jpg
• Parasympathetic nervous system
more important in regulation of
heart rate with vagus nerve of
system directly innervating SA
node and slowing heart rate.
http://www.becomehealthynow.com/images/organs/nervous/parasympathetic.jpg
Heart Disease
• More than ½ of all deaths in US
due to heart disease.
• Heart attack - death of cardiac
tissue due to prolonged blockage.
• Stroke - death of nervous tissue.
• Both usually occur because of
thrombus that gets caught in
coronary artery or an artery in
brain.
http://nonstandardized.com/pao2/images/heart_attack.jpg
• Heart damage can interrupt
electrical conduction of heart
causing individual to stop breathing,
heart stops beating.
• Most heart attacks result of
atherosclerosis (narrowing of
arteries) mostly from increased
levels of LDL in blood.
• Plaque begins to build in artery and
artery begins to thicken as deposits
of cholesterol are added.
• Can lead to arteriosclerosis hardening of arteries.
• Arteries more likely to capture a
thrombus - turns into embolus.
Blood vessels
• Capillaries lack 2 outer walls, only
have endothelium and basement
membrane.
• Arteries - thicker middle and outer
layers than veins - under higher
pressure than veins.
• Veins thinner - passive blood flow.
• Also have flaps - act as valves to
prevent backflow.
http://www.livescience.com/images/060619_artery_anatomy_02.jpg
• Arteries carry blood away from
heart, branch into smaller arteries
called arterioles.
• Arterial blood oxygenated except
for pulmonary artery - carries
deoxygenated blood from tissues to
lungs.
• Veins carry blood from capillaries
to heart.
• No pulse, carry dark red
deoxygenated blood, except for
pulmonary vein -carries oxygenated
blood from lungs.
• Capillaries permit exchange of
materials between blood and body’s
cells.
• Fluid seeps from thin-walled
capillaries by osmosis.
Regulation of blood flow
• Needs for blood flow increase and
decrease; flow of blood regulated
locally in tissues to match supply of
blood to metabolic needs.
• Smooth muscle in walls of
arterioles constrict to reduce blood
flow to capillaries in tissue.
• Smooth muscle relaxes when blood
leaving capillaries low in O2.
http://www2.uerj.br/micron/atlas/atlasenglish/Muscle/Liso1.jpg
• Allows more blood to flow through
arteriole and through capillaries
increasing oxygen supply to tissue.
• Levels of carbon dioxide can also
cause relaxation of arteriole
smooth muscle to increase blood
flow.
• Nervous system regulates blood
flow by autonomic nervous system.
http://cti.itc.virginia.edu/~psyc220/kalat/JK365.fig12.5.nervous_syste.jpg
• Sympathetic nervous system causes
constriction of arteries in many
tissues (i.e. digestive tract) causes
dilation in skeletal muscle.
• Control of blood flow occurs in
medulla of brain - receives
information from sensors in aorta
about stretching, from oxygen
sensors in other arteries.
http://www.brainexplorer.org/brain-images/medulla_oblongata2.jpg
• If aorta stretched, arterial blood
pressure is high - causes control
center in medulla to inhibit
sympathetic nervous system.
• Relaxes arteries in periphery, slows
heart rate.
• If blood is lost, decreasing arterial
pressure, stretch sensors trigger
response from sympathetic nervous
system.
http://www.med.umich.edu/1libr/aha/dilation.gif
• Causes vessels to constrict,
increases heart rate.
• Also occurs if decrease in oxygen
levels by oxygen sensors.
• Epinephrine increases heart rate,
constricts arteries - increases
arterial pressure.
• When blood pressure in arteries
fall, kidney secretes enzyme (renin)
- activates angiotensin.
• Acts on smooth muscle in
arterioles, causes constriction to
increase central pressure.
• Vasopressin secreted by posterior
pituitary in response to stretch
sensors (increases central
pressure)
http://content.answers.com/main/content/wp/en-commons/thumb/8/8a/600px-Renin-angiotensin-aldosterone_system.png
• Inflammation of local tissues cause
arterioles to expand, increasing
flow of fluid into capillaries and
tissues causing swelling.
• Histamine released in allergic
reaction, causes increased blood
flow and permeability of capillaries.
• Generalized swelling (edema) occurs
if osmotic balance of plasma is low.
http://www.uth.tmc.edu/courses/dental/pulpalmicro/pics/fig5large.jpg
Blood
• Blood - liquid component - plasma contains dissolved nutrients,
wastes, proteins, hormones,
fibrinogen.
• Fraction of blood without cells left
after clotting – serum; contains
glucose, lipids, salts, hormones,
albumin.
http://www.ndsu.nodak.edu/instruct/tcolvill/435/plasma.gif
• Materials suspended in plasma - red
blood cells, white blood cells,
platelets.
http://ucdavismagazine.ucdavis.edu/issues/fall04/graphics/BloodParts.jpg
• Blood placed in centrifuge cells can
separate out; volume of cells
measured.
• Percent of blood occupied by cells hematocrit - about 40% of total
blood volume.
Fig. 42.14
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Red blood cells (erythrocytes) most numerous.
• Main function - oxygen transport depends on rapid diffusion of
oxygen across red cell’s plasma
membranes.
• Formed in bone marrow, lose nuclei
and become disk like.
http://nmhm.washingtondc.museum/news/imgs/red_blood_cells_lg.jpg
• Red blood cell production
stimulated by erythropoietin produced by kidneys.
• Wear out after 4 months destroyed in spleen and liver.
• Contain hemoglobin - unites with
oxygen to form oxyhemoglobin.
http://sickle.bwh.harvard.edu/hctchart.gif
• Tissues - partial pressure of oxygen
low; hemoglobin releases oxygen.
• Lactic acid buildup also stimulates
oxygen release by hemoglobin.
• Carbon monoxide binds to
hemoglobin permanently, preventing
it from binding to oxygen +
delivering to tissues.
http://www.beliefnet.com/healthandhealing/images/si55551241_ma.jpg
• When RBCs mature - lose
mitochondria - can’t perform
aerobic respiration.
• Prevents them from using oxygen to
perform respiration themselves.
• Manufacture 2 major types of
antigens: A + B.
• In any individual, one, both, or
neither can be present.
http://www.ncbi.nlm.nih.gov/projects/mhc/images/otherimages/rbc_antigens.jpg
• Plasma of every individual contains
antibodies for antigens not present
on individual’s red blood cells.
• Type A have anti-B antibodies - if
they come into contact with it,
blood will clump.
http://medicalimages.allrefer.com/large/antibodies.jpg
• 5 major types of white blood cells,
or leukocytes: monocytes,
neutrophils, basophils, eosinophils,
lymphocytes.
• Function to fight infection.
• Monocytes, neutrophils phagocytes, engulf and digest
bacteria and debris from our cells.
Fig. 42.13
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Platelets not really cells - cell
fragments produced in marrow as
pieces of megakaryocyte cells.
• At site of bleeding injury,
activation of thrombin cleaves
fibrinogen protein in blood to make
fibrin that forms net across wound,
trapping more cells and blocking
flow of blood.
Fig. 42.16
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The lymph system
• Fluids, some blood proteins leak
from capillaries into interstitial
fluid returned to blood via
lymphatic system.
• Fluid (lymph) diffuses into lymph
capillaries.
• Drains into circulatory system.
http://www.acm.uiuc.edu/sigbio/project/updated-lymphatic/thymus_p.gif
• Along lymph vessels - organs called
lymph nodes.
• Lymph nodes filter lymph, attack
viruses and bacteria through cells
specialized for fighting infection.
• When body is fighting, lymph nodes
will become swollen and painful.
• Lymph system transports fats from
digestive system to circulatory
system.
Respiration
• Vital function of organisms is
ability to exchange gases with
environment (respiration).
• Most organisms rely on oxidation of
glucose through aerobic respiration
to generate energy.
• Oxygen final electron acceptor in
ETC of aerobic respiration to
produce ATP.
http://www.stanford.edu/group/hopes/treatmts/ebuffer/f_j13electtrans.jpg
• CO2 produced as waste product
from burning glucose in Krebs cycle.
• Diffuse easily across plasma
membranes - molecules move into
and out of cells by simple diffusion
across concentration gradient.
• Prokaryotes, protists, sponges, etc.
have cells exposed to external
environment, respiratory gases
easily exchanged through cell
membranes.
http://www.findhealer.com/glossary/images/krebs.gifs
• Complex multicellular organisms
need more complex ways of
exchanging gases with environment.
• Annelid (earthworm) secretes
mucus on external surface of body
which provides moist surface for
gas exchange from air to blood
through diffusion.
• Circulatory system brings O2 to
cells and CO2 to skin to be
excreted.
http://www1.istockphoto.com/file_thumbview_approve/527708/2/istockphoto_527708_earth_worm_macro_against_a_white_background.jpg
• Arthropods - series of respiratory
tubules (trachae)
• Tubules open to outside in orifices
(spiracles).
• Inside body, trachae subdivide into
smaller and smaller branches so
they can maintain close contact
with most cells.
http://www.esu.edu/~milewski/intro_biol_two/lab__12_annel_arthro/images/romalea_abdomen.jpg
• System allows for direct intake,
distribution, removal of respiratory
gases between air and body.
• No specialized cells for
transporting oxygen.
• No blood system intervenes with
transport of gases to body’s
tissues, so system is very efficient
and fast.
• Arthropods can produce large
amounts of energy, limits their size
because of system.
Respiration in fish
• Water contains less oxygen, more
difficult to breathe in water.
• Oxygen limiting resource in water,
not on land.
• Aquatic organisms require large
surface area to gas exchange.
• Gills of fish divided into numerous
thin-walled, threadlike filaments
well fed by capillaries.
• Walls of gills thin to maximize
diffusion of gases between blood
and water; also to minimize distance
these substances must travel.
• Gills protected from outside by
opercular flap so other organisms
won’t eat them.
Fig. 42.20
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• As water passes over filaments, O2
diffuses into blood, CO2 leaves
blood enters water.
• Arteries transport oxygenated
blood throughout body.
• Water passes out of body through
openings of sides of head, takes
CO2 with it.
http://www.agriteach.com/lessonfiles/aquaculture/basic_fish_anatomy.jpg
• Countercurrent exchange
maximizes exchange of gases
between blood in gills and water
flowing over gills.
• Blood flowing through gills moves in
opposite direction as water moving
across gills outside.
• Maximizes concentration gradient
of gases in blood and water, which
maximizes gas exchange.
Respiration in humans
• Amphibians evolved lungs - moved
to land - consist of simple air sacs
with very little surface area.
• Decreased surface area requires
exchange of gases across moist
skin.
• Mammals cannot exchange gases
across skin - respiratory system
evolved to meet demands.
http://www.ama-assn.org/ama1/pub/upload/images/446/respiratorydetail.gif
• Humans - complex system of
respiration to transport oxygen to
cells, get rid of CO2.
• Air passages involved - nose,
pharynx, larynx, trachea (windpipe),
bronchi (lead into each lung),
bronchioles that branch throughout
lungs, end in tiny sacs (alveoli) - site
of gas exchange.
Fig. 42.23
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Amount of alveoli create large
surface area for gas exchange.
• Lungs must move air in and out bring external air in contact with
alveoli.
• Found in chest (pleural cavity)
bound by ribs, separated from
abdomen by diaphragm.
http://www.aduk.org.uk/gfx/lungs.jpg
• Negative pressure in pleural cavity
keeps pleural membrane drawn
tightly outward against walls of
chest cavity.
• Keeps lungs inflated.
• If pleural cavity punctured, lungs
can collapse.
• Diaphragm curved upward when
relaxed, flattens when contracted.
• Chest muscles move ribs up and out
as diaphragm moves - creates
larger chest cavity + vacuum that
draws air into respiratory passages
(inhalation).
• When diaphragm and rib muscles
relax, chest cavity size decreases air forced out of lungs (exhalation).
• Exhalation passive - muscle
contraction not part of it.
• During strenuous exercise, muscles
activate exhalation.
• Breathing rate regulated in medulla
to supply tissues with correct levels
of O2 and CO2 removal.
http://www.brainexplorer.org/brain-images/medulla_oblongata2.jpg
• Excess CO2 in blood stimulates
medulla to send message to
diaphragm to increase frequency of
respiration.
• Less sensitivity to O2 levels.
• All air, whether inhaled or exhaled,
passes through trachea at same
time.
http://graphics.cs.ucr.edu/projects/simulatedBreathing/images/a4.jpg
• Some air not involved in gas
exchange.
• Even with strongest exhalation, still
air left in lungs - residual volume.
• Air breathed in mixes with air
already in lungs, diffuses to alveoli.
http://www.cptc.ctc.edu/library/Bio%20118%20Lecture%20Notes%20Rev%200105_files/image172.jpg
• Air in alveoli - different
composition from air in atmosphere.
• More water vapor, more carbon
dioxide, less oxygen.
http://upload.wikimedia.org/wikipedia/en/thumb/d/db/Alveoli_diagram.png/300px-Alveoli_diagram.png
Gas transport and exchange
• Alveoli - thin, moist walls,
surrounded by thin-walled
capillaries.
• Moist allows for gases to dissolve in
thin layer of fluid then diffuse
across respiratory membranes.
• O2 diffuses from alveolar air into
blood through alveolar and capillary
membranes.
http://library.thinkquest.org/19347/media/alveoli.jpg
• CO2, H2O diffuse out in same way.
• Gases always diffuse from high
concentration to low concentration.
• In tissues, O2 diffuses into tissues,
CO2 leaves.
• In lungs, O2 diffuses out of lungs,
CO2 enters because of increased O2
pressure.
Fig. 42.29
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 42.29, continued
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Inside alveoli liquid mostly water high surface tension - draws walls
of alveoli together with liquid gives potential to collapse, lose
ability to exchange gases.
• Prevented by secretion of
surfactant - reduces surface
tension.
• Premature infants may not have
this when born - causes difficulty in
breathing.
http://www.ees.adelaide.edu.au/research/enviro/evol_physiology/Fig%201%20synthesis%20and%20secretion%20diag%20large%20&%20higher%20res.jpg
• O2 transported in blood by RBCs.
• Contain oxygen transport protein
(hemoglobin).
• O2 binds to hemoglobin - allows
efficient delivery of O2 to tissues.
• Under normal conditions,
hemoglobin saturated with O2 in
lungs.
http://www.kacr.or.kr/img/gene_expression/hemoglobin.jpg
• As blood travels to tissues, low O2
levels in tissues allows some of O2
bound to hemoglobin to be released,
diffuse into tissue.
• Allows small changes in O2 needs in
tissues to cause large changes in
delivery of O2 to tissues.
http://www.shands.org/images/ency/fullsize/19510.jpg
• Increased pH during exercise
decreases affinity of hemoglobin
for O2 which allows more O2 to be
delivered to muscles.
• CO2 carried in blood as dissolved
carbonate ions, does not have
specific protein carrier.
http://www.gly.fsu.edu/~salters/GLY1000/6_Minerals/Slide55.jpg
• When CO2 dissolves in blood in
tissues, enters RBCs, converted by
enzyme carbonic anhydrase into
bicarbonate ions to be transported
back into blood.
• Lungs - enzyme converts
bicarbonate back into CO2 to be
exhaled.
http://www.breathcoach.co.uk/assets/images/hh_balance02.jpg
• Bicarbonate also pH buffer in
blood, regulated by kidney to
maintain plasma pH within normal
range.
http://www.egms.de/figures/journals/cto/2005-4/cto000007.f8.png