lecture 14 outline (ch. 42) i. circulatory systems ii.human heart iii. blood & vessels...
TRANSCRIPT
Lecture 14 Outline (Ch. 42)
I. Circulatory Systems
II. Human Heart
III. Blood & Vessels
IV. Cardiovascular disorders
V. Methods – bulk flow vs. diffusion
VII. Gas exchange and partial pressures
VIII. Breathing mechanisms
IX. Summary
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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
Circulation Overview
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Circulatory systems are open or closed• Open- bathes organs in hemolymph• Closed- direct vessel connections to organs
Circulation Overview
Heart
Hemolymph in sinusessurrounding organs
Heart
Interstitialfluid
Small branch vesselsIn each organ
Blood
Dorsal vessel(main heart)
Auxiliary hearts Ventral vessels
(b) A closed circulatory system(a) An open circulatory system
Tubular heart
Pores
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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
Circulation Overview
Arteries – away from heart, Veins – toward heart
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• Set of muscular chambers
• Atria collect blood• Ventricles send blood through
body
• The heart has evolved
The Vertebrate Heart
Ventricle gill capillaries: gas exchange
Blood collects - body capillaries gas exchange
Blood returns to heart, swimming helps
Single circulation
Artery
Heart:
Atrium (A)
Ventricle (V)
Vein
Gillcapillaries
Bodycapillaries
Key
Oxygen-rich blood
Oxygen-poor blood
Bony fishes, rays, sharks
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The Vertebrate Heart
2 atria empty into 2 ventricles
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!
Systemic circuit
Systemiccapillaries
Right Left
A A
VV
Lungcapillaries
Pulmonary circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Amphibians, reptiles, mammals
Double circulation – pulmonary circuit and systemic circuit
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4-chambered heart: A closer look
• 2 pumps• Right:
deoxygenated blood
• Left: oxygenated blood
Heart
Pulmonary artery
Rightatrium
Semilunarvalve
Atrioventricularvalve
Rightventricle
Leftventricle
Atrioventricularvalve
Semilunarvalve
Leftatrium
Pulmonaryartery
Aorta
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Right ventricle pumps deO2 blood to lungs through pulmonary arteries
Pumps into right ventricle
Heart
• Right atrium receives deO2 blood from veins– Superior vena cava
– Inferior vena cava
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• Oxygenated blood returns to left atrium from lungs via pulmonary veins
Oxygenated blood pumped to body through aorta
Pumps into left ventricle
Heart
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Keeping blood moving• Heart valves
maintain one-way flow
• Atrioventricular valves– Between
atria & ventricles
• Semilunar valves– Between
ventricles & arteries
Heart
For each term, determine whether the region contains oxygenated or deoxygenated blood:
Aorta Pulmonary veins
Inferior vena cava Right atrium
Left atrium Right ventricle
Left ventricle Superior vena cava
Pulmonary arteries
Oxygenated Deoxygenated
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The Cardiac Cycle & Blood Pressure
Heart
Normal blood pressure ~120/70
• “Lub-dup” sounds heard with stethoscope– Lub – blood against closed AV valves– Dup – blood against closed semilunar valves
• Systolic– Ventricular contractions
(higher pressure)• Diastolic
– Period between contractions (lower pressure)
sphygmomanometer
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The Cardiac Cycle
Heart
Atrial andventricular diastole
0.4sec
1
Atrial systole and ventricular diastole
0.1sec
2
Ventricular systole and atrialdiastole
0.3 sec
3
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Cardiac muscle contracts
• Present only in the heart
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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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)
Heart
What’s in blood?
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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
Blood
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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
Blood
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White blood cells: leukocytes
• Less than 1% of blood cells• Disease defense
– Consume foreign – particles – (macrophages)– Produce antibodies – (lymphocytes)
Blood
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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
Blood
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Artery Vein
SEM100 µm
Endothelium
Artery
Smoothmuscle
Connectivetissue Capillary
Basal lamina
Endothelium
Smoothmuscle
Connectivetissue
Valve
Vein
Arteriole Venule
Red blood cell
Capillary
15 µ
mL
M
Blood is carried in vessels!
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Heart
Arteries Arterioles
Capillaries
VenulesVeins
• Carry blood away from heart• Thick-walled:
• Smooth muscle/elastic fibers• Withstand high pressure
Arteries
Blood Vessels
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Heart
Arteries Arterioles
Capillaries
VenulesVeins
• Control distribution of blood flow• Smooth muscle expands / contracts• Under hormone / NS control
Arterioles
Blood Vessels
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• 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
Blood Vessels
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Heart
Arteries Arterioles
Capillaries
VenulesVeins
• Nutrients/waste exchanged with cells:• Vessel wall one-cell thick• Blood flow very slow
• Materials exit/enter via diffusion
Capillaries
Blood Vessels
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Heart
Arteries Arterioles
Capillaries
VenulesVeins
• Carry blood towards the heart• Thin-walled; large diameter
• One-way to prevent backflow
Venules & Veins
Blood Vessels
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Skeletal Muscle Pump:
Vein Valve:
Blood Vessels
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Blood Vessels
Varicose veins occur if the vein valves become inefficient
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Cardiovascular Disorders:• Leading cause of death in the United States
1) Hypertension = High blood pressure• Resistance in vessels = work for heart
Blood Vessels
2) Atherosclerosis = Deposits (plaques) collect in vesselsConnectivetissue
Smoothmuscle Endothelium Plaque
(a) Normal artery (b) Partly clogged artery50 µm 250 µm
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If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation?
Thought Question:
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Living things process energy
• They need oxygen for this - Why?
Overview
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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
Gas Exchange Systems
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Gills• Aquatic gas exchange
Gas Exchange Systems
• Elaborately folded ( surface area)• Contain capillary beds
• Gill size inversely related to [O2]
• Large gills = low [O2]
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Gas Exchange SystemsFish Efficiency
• Dissolved O2 is < 1% of water (21% of air)
• Countercurrent exchange increases efficiency
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Reptiles & Mammals use lungs exclusively
• Lack permeable skin• Lungs are more efficient
– Especially birds!
Gas Exchange Systems
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Human Respiration
• Air enters through nose and mouth to pharynx
• Travels through larynx (voice box)
• Epiglottis directs travel
Mammals
Pharynx
Larynx(Esophagus)
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
Leftlung
Nasalcavity
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On to the lungs
• Trachea • Bronchi • Bronchioles • Alveoli
Human Respiration
Air is warmed & cleaned• Dust & bacteria trapped by mucus • Swept up and out by cilia
• provide enormous surface area
• Surfactant keeps surface moist
• Association with capillaries– Diffusion of
gasses Capillaries
Alveoli
Branch ofpulmonary artery
Branch ofpulmonary vein
Terminalbronchiole
Both mammals and reptiles must maintain homeostasis and use aerobic respiration.
A. Would you expect the lungs of a lizard (ectotherm) to have more or fewer alveoli per unit area than lungs of a rat (endotherm)? Explain why.
B. Would you expect the heart rate of the lizard to be higher or lower than the heart rate of the rat? Explain.
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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
Exhaled air Inhaled air
Pulmonaryarteries
Systemicveins
Systemicarteries
Pulmonaryveins
Alveolarcapillaries
AlveolarspacesAlveolar
epithelialcells
Heart
SystemiccapillariesCO2 O2
Body tissue
CO2 O2
8 1
2
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6 4
5
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CO2 Transport
• CO2 binds hemoglobin loosely
• Dissolved in plasma• Combines with H20 to
form bicarbonate (HCO3
-)– More CO2 = lower pH
Transport of gasses
The Bohr Effect:
Hemoglobin binds more tightly to O2 when pH is increased and loosely when pH is decreased
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O2 Transport
• Binds to hemoglobin– Removes O2 from plasma
solution– Increases concentration
gradient; favors diffusion from air via alveoli
Transport of gasses
CO binds more tightly to hemoglobin than O2
Prevents O2 transport
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Breathing Mechanisms• Inhalation:Rib muscles contract to expand rib cageDiaphragm contracts (down) expands the volume of thorax and lungs
• Thoracic cavity expands, produces negative pressure which draws air into the lungs
Rib cageexpands.
Airinhaled.
Airexhaled.
Rib cage getssmaller.
1 2
Lung
Diaphragm
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Breathing is involuntary
• Controlled by respiratory center of the brain
• Adjusts breath rate & volume based on sensory input– Maintain a constant
concentration of CO2
Breathing Mechanisms Homeostasis:Blood pH of about 7.4
CO2 level
decreases. Stimulus:Rising level ofCO2 in tissues
lowers blood pH.Response:Rib musclesand diaphragmincrease rateand depth ofventilation.
Carotidarteries
AortaSensor/control center:Cerebrospinal fluid
Medullaoblongata