Transcript Chapter 7 (Circulation)

Internal Systems and
Regulation
Transportation and Circulation
What does the transport
system do?
Nutrients travel to and wastes away from all cells
2. Pathway for disease fighting agents and hormones
3. Control of body temperature – homeostasis
1.
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Vascular system = system of fluid tissue that plays a role
in transporting nutrients to cells in the body
 Circulatory system = system in which the progress of
fluid is controlled by muscle movements
 Cardiovascular system = circulatory system in which the
vascular fluid is moved around by a pump
Internal Transport
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Unicellular – no need for organized transport
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One cell so diffusion allows movement of substances in and out
(eg. Amoeba)
Cytoplasm streaming is utilitized to move substances once
inside the cell
Multicellular – some do not require organized
transport
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Cnidaria (eg. hydra and jellyfish) fluid taken in through the
mouth enters a body cavity that extends through the body of the
organism.
Cells are no more then a few layers thick at any point so
diffusion is key once again.
Internal Transport
Specialization – required for most multicellular
organisms
 Open Transportation Systems (p. 243, fig. 4)
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Blood does not always stay contained within blood vessels
Fluid is moved around the chambers (sinuses) of arthropods by
coordinated movements of the body muscles
Circulation occurs from the aorta to the sinuses relatively
slowly – transport is not rapid
Remember that insects have a tracheal respiratory system which
is separate from this transport system
Internal Transport
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Closed Transportation System (p.243, fig. 5)
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Blood does not bathe the cells directly, but rather is pumped
around the body using a network of vessels
Fluid circulates only in one direction, passing through the gas
exchange system in the cycle
Specialized
Internal Transport
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Fish
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Blood travels through the heart only once
during each complete circuit around the
body
Blood travels out of heart via the ventral
artery to the capillaries in the gills. From
there the blood travels to the dorsal artery
where the body receives oxygenated blood
– Advantage = all blood traveling from
the heart is oxygenated in the gills
– Disadvantage = blood pressure created
by the heart is lost in the capillaries in
the gills (they are elastic)
Specialized Internal Transport
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Amphibians – frogs, toads, salamanders
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As fish have two chambers, animals in class Amphibia have
three chambered hearts.
Blood travels from heart to lungs, then back to heart where it is
pumped again into the arteries to the body
Blood that returns from the lungs and blood that returns from
the body mixes – this is an inefficiency
The extra chamber though, in relation to the fish, allows a
double circulation to occur and remember that amphibians are
able to breathe at a more significant level through their skin as
well.
Specialized Internal Transport
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Birds and Mammals
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1.
High energy requirements means lots of oxygen delivered
quickly to the entire body and wastes to be removed. Two
more adaptations:
Oxygenated and deoxygenated blood must be kept completely
separate – a fourth chamber for the heart
 Two atria and two ventricles
 Blood enters right atrium, drops to right ventricle then pumped to
lungs (oxygenation)
 From the lungs back to the heart and into left atrium, down into left
ventricle and out into the aorta and then other arteries.
2.
Blood pressure is maintained by arterial system
Mammalian Circulatory System
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Discoveries over time
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Ancient Greeks – heart was seat of intelligence
Galen (Greek physician) – in second century theorized that
blood ebbed and flowed like tides
– Arteries and veins were separate and blood flowed out of each to the
body
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William Harvey – in the seventeenth century theorized that we
have a cyclic circulatory system
– Was never able to find the point were blood stopped traveling away
from heart and started back
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Marcello Malpighi – in 1657 identified capillaries to back
Harvey’s findings
Mammalian Circulatory System
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Three primary closed cycles:
1.
2.
3.
Cardiac circulation = pathway of blood within the heart
Pulmonary circulation = blood from the heart to lungs and back
Systemic circulation = blood from the heart to the rest of the body
Facts
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male has 5 to 6 litres while a female has 4 to 5 litres of blood
80-90% of blood is in systemic system, most of rest is in pulmonary system
There are three main elements to a circulatory system:
1.
2.
3.
Transport medium – fluid being moved around (talk about next)
Transport vessels – fluid from one area to another (later)
A pumping mechanism (last)
Transport Medium
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Blood – collection of specialized cells and is
therein considered a tissue
Contains two distinct elements:
1.
Plasma = 55% of blood
– Water, gases, proteins, sugars, vitamins, minerals, waste
2.
Cells = 45% of blood
 Red blood cells (44%), White blood cells, Platelets
Blood Cells
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Red Blood Cells – Erythrocytes (44%)
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Average male has 5.5 million rbc/ml of blood
Specialized for oxygen transport (each rbc is packed with 280
million molecules of the pigment hemoglobin) and transports
98% of O2 in body
Each hemoglobin molecule contains 4 iron atoms which each
have a binding site or heme group
In theory 4 molecules of oxygen can bind to one molecule of
hemoglobin
Blood Cells
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Other important facts about erythrocytes:
– O2 forms a loose bond with the heme group whereas CO forms a
strong bond.
– 45% of CO2 is carried by erythrocytes forming a compound called
carbaminohemoglobin.
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9% is carried in the plasma.
– The rest combines with water to form carbonic acid (H2CO3)
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This keeps the partial pressure of CO2 in the blood low so that more CO2 can
diffuse out of cells.
– Carbonic acid will dissociate into H+ ions and HCO3- ions. This
would increase the acidity of the blood however hemoglobin also
picks up and rids the body of H+ ions to maintain blood pH.
Blood Cells
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Death of an erythrocyte
– Lives 3-4 months
– Travels to the liver where much of the iron is salvaged
and recycled
– One to two million rbc’s replaced every second
– Any reaction that causes a reduction of O2 in blood will
cause our bone marrow to increase production of rbc’s
– People who travel to high altitudes might increase the
number of rbc’s by a factor of 2
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Sport training?
Blood Cells
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White blood cells – Leukocytes
– Leukocytes = 1% of blood however their number will
double when fighting infection (pathogens)
– Have a nuclei and appear colorless
– Macrophages = phagocytic cells that can pass through
capillary walls to engulf and digest pathogens and
pseudopodial action to move.
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Part of the body’s innate immune response which is the body’s
generalized response to infection.
Blood Cells
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Lymphocytes – non-phagocytic cells that facilitate the
body’s acquired immune response
– Enables the body to recognize and fend off specific pathogens
– Two main types of lymphocytes:
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T cells = mature in thymus
B cells = arise in bone marrow
Several kinds of each in the body that contribute to specific parts of the
immune response
– Can not only fight disease but also can become a variety of cell
types under particular conditions
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Enter bone marrow and become rbc’s
Enter other tissues can play role of different kinds of connective tissues
Blood Cells
Platelets – not actual cells but fragments of cells created
when larger cells in the bone marrow break apart.
Extremely vital to blood clotting.
 Contain no nucleus and break down quickly in blood (7-10
days).
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Blood will not clot unless a blood vessel is broken
Substances released by the broken blood vessel will attract platelets
As the platelets collect they will rupture and release certain chemicals
These chemicals combine with others in the plasma to produce the enzyme
thromboplastin.
If Ca2+ is present, thromboplastin will combine with prothrombin (protein
created in liver) to produce thrombin.
Thrombin is an enzyme that reacts with fibrinogen (another plasma protein)
to produce fibrin.
Fibrin is an insoluble material that forms a mesh of strands around the
wound and stops cells from escaping.
Plasma
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Fluid portion of the blood but it has many functions:
– Contains substances that ensures blood’s well-being and
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maintenance
Serum albumin = maintains blood volume and pressure
Serum globulin = antibodies to defend against disease
Fibrinogen = blood clotting
Transport of CO2 in the form of H2CO3
When fibrinogen and other clotting agents removed the
liquid that remains is called serum.
– Serum immune to a particular disease (even if from an animal) can
be injected into a patient to provide temporary immunity to that
disease.
Human Blood Groups
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Due to Harvey’s findings = transfusions
– Within 50 years of his work
– Many successful however dramatic failures as well.
Transfusions were outlawed in 1678 in England.
– Early 1900’s the major blood groups were identified.
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A, B, AB, O (p. 247, table 1)
Characterized by presence or absence of two protein markers
on the walls of the rbc’s.
Agglutination if improper blood types mixed
Universal Donor  Type O blood
Universal Acceptor  Type AB blood
Human Blood Groups
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Rhesus factor – another protein marker
– If you have it you are Rh+, if not Rh–
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An Rh- individual can donate to an Rh+ individual however…
An Rh+ donor into Rh- recipient is usually okay as the anti-Rh
antibodies develop over two to four month period after the
transfusion. A second transfusion would be deadly as the body
now has the appropriate antibodies for an immediate response
(same as an inappropriate ABO transfusion).
Transport Vessels
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Arteries – blood away from heart
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Arterioles
Oxygenated blood*
Three different structural layers:
– Outer = connective tissue and elastic fibres
– Middle = thickest and contains elastic fibres and smooth muscle
– Inner = smooth epithelial cells (reduce friction)
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Elasticity is key for pressure (p. 250, fig 1)
Veins – blood to the heart
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Venules
Deoxygenated blood*
Less elasticity but greater capacity (2x as much blood)
Thinner wall and larger inner circumference then artery
Gravity defied due to skeletal muscle and valves in veins (p. 250, fig 1)
Transport Vessels
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Capillaries
– Smallest blood vessel (8 um in diameter)
– Regulates movement of fluids into and out of blood
– Blood flows quickly however friction in capillaries slows blood
down to allow nutrient and waste exchange to occur (p. 252, fig. 3)
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*Exception to the rule*
– Pulmonary artery carries deoxygenated blood from heart to lungs
and pulmonary vein returns oxygenated blood from the lungs to
the heart.
Mammalian Heart
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Pumps 70 times per minute (90000 times/day)
 Pumps fluid through 160 000 km of vessels
 Steady flow by adjusts quickly to demands of
increases and decreases in pressure
 Pumps in two directions at once with no mixing of
fluids
 Life expectancy of ~ 80 years
 All this in the size of your fist
Mammalian Heart
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Blood enters the atria (left and right) and exits from the
ventricles (left and right)
– The atria contract simultaneously as do the ventricles.
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As blood returns from the body it is collected in the superior
vena cava which flows into the right atrium
Blood then is pumped into the right ventricle as the atria
contract and then blood is moved out to the pulmonary arteries
as the ventricle contracts
The same process is going on on the other side of the heart as
blood is returning from the lungs in the pulmonary veins into
the left atria.
This blood is pumped to the left ventricle and then as the left
ventricle contracts the blood is pumped out the aorta to the
body.
Mammalian Heart
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Contractions
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Atria are thin walled
Ventricles are more muscular with the left ventricle being the thickest
Valves
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Between the right atrium and right ventricle there is an atrioventricular valve
(tricuspid)
Between the left atrium and the left ventricle there is an atrioventricular
valve (bicuspid)
Between the left ventricle and the aorta and between the right ventricle and
the pulmonary artery semilunar valves are used.
Lub-dub sound is created by these valves opening and closing in the heart
– Lub = atrioventricular valves
– Dub = semilunar valves
Mammalian Heart
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Control of the Heart
– The impulse that causes a heart to beat is actually in the
heart itself so the heart can beat for a while on its own.
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A bundle of special muscle tissue, located in right atrium,
stimulates muscle fibres to contract and relax rhythmically.
This tissue is called the sinoatrial node or S-A node. Also
known as the pacemaker.
S-A node gives electrical impulse to both atria and causes them
to contract simultaneously.
The pulse will then reach the atrioventricular node (A-V node)
located between the two ventricles to start their contraction.
Mammalian Heart
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Recording a Heart Rate (p.260, fig. 3 & 4)
– Electrocardiograph (ECG) can monitor all of the impulses
– Small voltage increase as the electrical depolarization that
accompanies contraction of the atria (P)
– Large spike accompanies the contraction of the ventricles
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Ventricular depolarization (QRS)
– As the ventricles recover another small spike shows the electrical
repolarization that precedes the next firing of the S-A node (T)
– Ventricular fibrillation – ventricles contract randomly
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Can be sometimes stopped. A strong electrical current to the heart and S-A
node can take over again.
Mammalian Heart
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Chemical Regulators
– Increased activity requires increased heart rate
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Running causes an increase of CO2 in blood
Receptors in blood vessels pick this up and send a signal to the medulla
oblongata
Your medulla will release noradrenaline which when it reaches the S-A node
will cause the node to fire more rapidly
– Decreased activity changes the heart rate back
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Fast heart means high blood pressure and this info is carried to the medulla,
picked up by the blood vessels again
Medulla will cause the nervous system to release acetylcholine to slow down
the firing of the S-A node
– Adrenaline – the “fight or flight” response
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If adrenaline is released into your bloodstream by your nervous system your
heart rate will increase as well.
Mammalian Heart
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Heart Defects
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Common problems at birth – valves, walls dividing chambers
of heart or structure of blood vessels near the heart
– Septal defect – hole in the septum (separates right and
left ventricles)
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Oxygenated and deoxygenated blood are able to mix
– Murmurs – one or more of heart valves not closing
properly
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Mitral valve prolapse – flaps of the mitral valve close unevenly
allowing blood to flow from the left ventricle into the left
atrium
– Arrhythmia – irregular heartbeat (p. 267, fig. 1)
Homeostasis
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Blood Pressure
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Fluctuations can be created due to increased demands on the body and how
readily the body reverts back to a normal level is indicative of one’s overall
fitness.
High pressure – when left ventricle is pumping and this is called systolic
pressure.
Low pressure – just before another contraction of the ventricles and is called
the diastolic pressure.
Average is 120/80 mm of Hg and is measured using a sphygmomanometer
Hypertension – chronic high blood pressure
– High pressure against arterial walls due to increase in volume or loss of
elasticity
– Salt = blood will retain more water, increase volume
– Cholesterol = arteries will clog, reduce elasticity
– Caffeine, nicotine and alcohol imitate noradrenaline and increase heart rate
– Age, heredity, lack of exercise, smoking and obesity
Homeostasis
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Hypertension
– Plaque build up in arteries can cause damage to platelets and
therein can start to lead to a blood clot (embolism).
– Treatment
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Exercise, better diet and medications
– Aspirin – helps prevent platelets from sticking to one another
– Digitalin – produced in foxgloves and is toxic at high levels however at lower
levels it strengthens heart contractions and slows heart rate
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Surgery
– Angioplasty = fine plastic tube inserted into artery and when a constricted
region is identified a balloon is blown up to force the vessel open
– Coronary bypass = involves removing a segment of healthy blood vessel from
one part of your body and using it to go around a blockage near the heart.
• The term double or triple refers to the number of blood vessels containing
blockages that must be bypassed. (p.258, fig. 3)