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Lecture 11 Outline (Ch. 42)
I.
II.
III.
IV.
V.
Circulatory Systems
Human Heart
Blood & Vessels
Cardiovascular disorders
Methods – bulk flow
vs. diffusion
VII. Gas exchange and partial
pressures
VIII. Breathing mechanisms
IX. Preparation for next lecture
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Circulation Overview
Circulation carries energy,
dissolved gasses, wastes
•
•
Connects individual cells in
distant parts of body
Requirements
– Blood – fluid for transport
– Blood vessels – channels for
transport
– Heart – pump for circulation
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Circulation Overview
Circulatory systems are open or closed
•
•
Open- bathes organs in a hemocoel
Closed- direct vessel connections to organs
Heart
Hemolymph in sinuses
surrounding organs
Pores
Heart
Blood
Interstitial
fluid
Small branch vessels
In each organ
Dorsal vessel
(main heart)
Tubular heart
(a) An open circulatory system
Auxiliary hearts
Ventral vessels
(b) A closed circulatory system
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Circulation Overview
Vertebrates have a closed circulatory system
•
•
More efficient
– Blood is 5 – 10% of body volume
– Flow is more rapid, pressure is higher
Multifunctional
– Transport dissolved gasses
– Distribute nutrients & hormones
– Transport waste
– Thermoregulation
– Circulate immunodefenses
Arteries – away from heart,
Veins – toward heart
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The Vertebrate Heart
•
Artery
Heart:
Atrium (A)
Ventricle (V)
Gill
capillaries
•
•
Atria collect blood
Ventricles send blood
through body
•
The heart has evolved
Vein
Body
capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
Bony fishes, rays, sharks
Set of muscular
chambers
Ventricle  gill
capillaries: gas
exchange
Blood collects - body
capillaries  gas
exchange
Blood returns to heart,
swimming helps
Single circulation
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The Vertebrate Heart
Pulmonary circuit
2 atria empty into 2 ventricles
Lung
capillaries
Complete septum (this varies) –
right side receives oxygen poor
blood from body – sends to lungs
Endotherms need to deliver 10X
as much dissolved gasses and
nutrients/waste as same size
ectotherms!
Double circulation –
pulmonary circuit
and systemic circuit
A
V
Right
A
V
Left
Systemic
capillaries
Key
Systemic circuit
Oxygen-rich blood
Oxygen-poor blood
Amphibians, reptiles, mammals
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4-chambered heart:
A closer look
Heart
Pulmonary artery
•
2 pumps
•
Right:
deoxygenated
blood
Left:
oxygenated
blood
•
Aorta
Pulmonary
artery
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Atrioventricular
valve
Right
Left
ventricle ventricle
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Heart
•
Right atrium receives deO2 blood from veins
– Superior vena cava
– Inferior vena cava
Right ventricle pumps
deO2 blood to
lungs through
pulmonary arteries
Pumps into right ventricle
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Heart
•
Oxygenated
blood returns to
left atrium from
lungs via
pulmonary veins
Oxygenated blood
pumped to body
through aorta
Pumps into left ventricle
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Heart
Keeping blood moving
•
•
•
Heart valves
maintain one-way
flow
Atrioventricular
valves
– Between
atria &
ventricles
Semilunar valves
– Between
ventricles &
arteries
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Heart
2 Atrial systole and ventricular
diastole
The Cardiac Cycle
1 Atrial and
ventricular diastole
0.1
sec
0.4
sec
0.3 sec
3 Ventricular systole and atrial
diastole
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Heart
The Cardiac Cycle & Blood Pressure
Normal blood pressure ~120/70
•
•
Systolic
– Ventricular contractions
(higher pressure)
Diastolic
– Period between contractions
(lower pressure)
sphygmomanometer
• “Lub-dup” sounds heard with stethoscope
– Lub – blood against closed AV valves
– Dup – blood against closed semilunar valves
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Heart
Cardiac muscle contracts
•
Present only in the heart
Cells linked by
intercalated discs
Prevents strong contractions
from tearing muscle
Allows rapid spread of
electrical signal for
simultaneous
regional
contraction
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Heart
Keeping blood moving
•
•
•
Pacemaker cells initiate and
coordinate contractions
Sinoatrial (SA) node
– Primary pacemaker
– Stimulates atrial
contractions
Atrioventricular (AV) node
– Delayed impulse received
from SA node
– Ventricular contraction
after atrial contractions
have filled them with
blood (delay ~0.1 sec)
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Blood
Plasma
•
•
Primarily water
Dissolved proteins and electrolytes
Blood
•
•
Plasma fluid
Cells
– Red blood cells – transport
– White blood cells – defense
– Platelets – clotting
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Blood
Red blood cells: Erythrocytes
•
•
•
Most abundant blood cells (over 99%)
Transport O2 and CO2
Iron-based hemoglobin protein binds to O2 and
transports from areas of high concentration to
low concentration
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Blood
Erythrocytes are short-lived
•
•
•
•
Formed in bone marrow
Lack nuclei (cannot divide or make proteins)
Dead cells are removed by liver and spleen
– Iron is recycled, although some is excreted
Number of erythrocytes
maintained by negative
feedback
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Blood
White blood cells: leukocytes
•
•
Less than 1% of blood cells
Disease defense
–
–
–
–
–
Consume foreign
particles
(macrophages)
Produce antibodies
(lymphocytes)
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Blood
Platelets
•
•
•
Cellular fragments
aid blood clotting
Ruptured cells and
platelets work together
to produce substances
that plug damaged
vessels
Scabs are platelets
embedded in web of
fibrin proteins
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Blood is
carried in
vessels
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Artery
Vein
SEM
Valve
100 µm
Basal lamina
Endothelium
Smooth
muscle
Connective
tissue
Endothelium
Smooth
muscle
Capillary
Connective
tissue
Artery
Vein
Capillary
15 µm
Red blood cell
Venule
LM
Arteriole
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Blood Vessels
Arteries
Arterioles
Arteries
• Carry blood away from heart
• Thick-walled:
Heart
Capillaries
• Smooth muscle/elastic fibers
• Withstand high pressure
Veins
Venules
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Blood Vessels
Arteries
Arterioles
Arterioles
• Control distribution of blood flow
• Smooth muscle expands / contracts
• Under hormone / NS control
Capillaries
Heart
Veins
Venules
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Blood Vessels
•
•
•
•
Arterioles
Contract walls: redirects blood to heart and muscles
when needed (stress, exercise, cold)
Relax walls: brings more blood to skin capillaries to
dissipate excess heat
Precapillary sphincters control blood flow to
capillaries
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Blood Vessels
Arteries
Arterioles
Capillaries
• Nutrients/waste exchanged with cells:
• Vessel wall one-cell thick
• Blood flow very slow
Capillaries
Heart
• Materials exit/enter via diffusion
Veins
Venules
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Blood Vessels
Arteries
Arterioles
Venules & Veins
• Carry blood towards the heart
Heart
Capillaries
• Thin-walled; large diameter
• One-way to prevent backflow
Veins
Venules
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Blood Vessels
Skeletal Muscle Pump:
Vein Valve:
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Blood Vessels
Varicose veins occur if the vein valves become inefficient
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Blood Vessels
Cardiovascular Disorders:
• Leading cause of death in the United States
1) Hypertension = High blood pressure
•  Resistance in vessels =  work for heart
2) Atherosclerosis = Deposits (plaques) collect in vessels
Connective
tissue
Smooth
muscle
Endothelium
Plaque
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(a) Normal artery
50 µm (b) Partly clogged artery
250 µm
Thought Question:
If you are an athlete who trains at high elevations, what
happens if you compete at a lower elevation?
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Overview
Living things process energy
• They need oxygen for this - Why?
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Gas Exchange Systems
Respiratory systems enable gas
exchange
• Bulk flow
– Movement in bulk
– Air/water to respiratory
surface
– Blood through vessels
• Diffusion
– Individual molecules move
down concentration
gradients
– Gas exchange across
respiratory surface
– Gas exchange in tissues
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Gas Exchange Systems
•
Aquatic gas exchange
Gills
• Elaborately folded ( surface area)
• Contain capillary beds
• Gill size inversely related to [O2]
• Large gills = low [O2]
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Gas Exchange Systems
•
Dissolved O2 is < 1%
of water (21% of air)
•
Countercurrent
exchange increases
efficiency
Fish Efficiency
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Gas Exchange Systems
Reptiles & Mammals use lungs exclusively
•
•
Lack permeable skin
Lungs are more efficient
– Especially birds!
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Mammals
Human Respiration
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•
•
Air enters through
nose and mouth
to pharynx
Travels through
larynx (voice box)
Epiglottis directs
travel
Nasal
cavity
Pharynx
Left
lung
Larynx
(Esophagus)
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
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Human Respiration
On to the lungs
•
•
•
•
•
•
•
Trachea 
Bronchi 
Bronchioles
 Alveoli
Air is warmed & cleaned
•
•
Dust & bacteria trapped by mucus
Swept up and out by cilia
Branch of
pulmonary vein
provide enormous
surface area
Surfactant keeps
surface moist
Association with
capillaries
– Diffusion of
gasses
Branch of
pulmonary artery
Terminal
bronchiole
Alveoli
Capillaries
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Human Respiration
• Gas exchange is
driven by differences
in pressures
• Blood from body with
low O2, has a partial
oxygen pressure
(PO2) of ~40 mm Hg
• By contrast, the PO2
in the alveoli is about
100 mm Hg
• Blood leaving lungs,
thus, normally
contains a PO2 of
~100 mm
1 Inhaled air
8 Exhaled air
Alveolar
epithelial
cells
2 Alveolar
spaces
CO2
O2
Alveolar
capillaries
7 Pulmonary
arteries
3 Pulmonary
veins
6 Systemic
veins
4 Systemic
arteries
Heart
CO2
O2
Systemic
capillaries
5 Body tissue
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Transport of gasses
CO2 Transport
•
•
•
CO2 binds
hemoglobin loosely
Dissolved in plasma
Combines with H20
to form bicarbonate
(HCO3-)
–
More CO2 = lower pH
The Bohr Effect:
Hemoglobin binds more tightly to O2 when pH is
increased and loosely when pH is decreased
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Transport of gasses
O2 Transport
•
Binds to hemoglobin
– Removes O2 from
plasma solution
– Increases concentration
gradient; favors diffusion
from air via alveoli
CO binds more tightly to
hemoglobin than O2
Prevents O2 transport
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Breathing Mechanisms
• Inhalation:
Rib muscles 1
contract to
cage
expand rib Rib
expands.
cage
Diaphragm
contracts
(down)
expands the
volume of
thorax and
lungs
2
Air
inhaled.
Rib cage gets
smaller.
Air
exhaled.
Lung
Diaphragm
• Thoracic cavity expands, produces negative pressure
which draws air into the lungs
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Breathing Mechanisms
Breathing is
involuntary
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•
Homeostasis:
Blood pH of about 7.4
CO2 level
decreases.
Controlled by respiratory
center of the brain
Adjusts breath rate & volume
based on sensory input
– Maintain a constant
concentration of CO2
Response:
Rib muscles
and diaphragm
increase rate
and depth of
ventilation.
Stimulus:
Rising level of
CO2 in tissues
lowers blood pH.
Carotid
arteries
Sensor/control center:
Cerebrospinal fluid
Aorta
Medulla
oblongata
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Things To Do After Lecture 11…
Reading and Preparation:
1.
Re-read today’s lecture, highlight all vocabulary you do not
understand, and look up terms.
2.
Ch. 42 Self-Quiz: #2, 3, 4, 6, 7 (correct answers in back of book)
3.
Read chapter 42, focus on material covered in lecture (terms,
concepts, and figures!)
4.
Skim next lecture.
“HOMEWORK” (NOT COLLECTED – but things to think about for studying):
1.
Compare and contrast veins and arteries in terms of structure and
function.
2.
Diagram the path blood takes from the body, to the heart and lungs,
back to the body.
3.
Explain in detail how oxygen is carried in the bloodstream and
exchanged in the lungs and at cells, from drawing a breath to bulk flow
in blood to diffusion at cells. What do cells use this oxygen for?
4.
Explain homeostatic control of breathing.