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
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
2
Circulation Overview
Circulatory systems are open or closed
•
•
Open- bathes organs in hemolymph
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
3
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
4
The Vertebrate Heart
Artery
Heart:
Atrium (A)
Ventricle (V)
•
Set of muscular
chambers
•
•
Atria collect blood
Ventricles send blood through
body
•
The heart has evolved
Gill
capillaries
Vein
Body
capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
Bony fishes, rays, sharks
Ventricle  gill
capillaries: gas
exchange
Blood collects - body
capillaries  gas
exchange
Blood returns to heart,
swimming helps
Single circulation
5
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
6
4-chambered heart: A
closer look
Heart
Pulmonary artery
Aorta
Pulmonary
artery
Right
• 2 pumps
atrium
• Right:
deoxygenated
blood
Semilunar
• Left:
valve
oxygenated
blood
Atrioventricular
Left
atrium
Semilunar
valve
Atrioventricular
valve
valve
Right
Left
ventricle ventricle
7
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
8
Heart
•
Oxygenated blood
returns to left atrium
from lungs via
pulmonary veins
Oxygenated blood
pumped to body
through aorta
Pumps into left ventricle
9
Heart
Keeping blood moving
•
•
•
Heart valves
maintain one-way
flow
Atrioventricular
valves
– Between
atria &
ventricles
Semilunar valves
– Between
ventricles &
arteries
10
For each term, determine whether the region
contains oxygenated or deoxygenated blood:
Oxygenated
Aorta
Inferior vena cava
Left atrium
Left ventricle
Pulmonary arteries
Deoxygenated
Pulmonary veins
Right atrium
Right ventricle
Superior vena cava
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
12
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
13
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
14
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)
15
What’s in blood?
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
17
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
18
Blood
White blood cells: leukocytes
•
•
Less than 1% of blood cells
Disease defense
– Consume foreign
– particles
– (macrophages)
– Produce antibodies
– (lymphocytes)
19
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
20
Artery
Vein
SEM
Blood is carried
in vessels!
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
21
Blood Vessels
Arteries
Arterioles
Arteries
• Carry blood away from heart
• Thick-walled:
Heart
Capillaries
• Smooth muscle/elastic fibers
• Withstand high pressure
Veins
Venules
22
Blood Vessels
Arteries
Arterioles
Arterioles
• Control distribution of blood flow
• Smooth muscle expands / contracts
• Under hormone / NS control
Capillaries
Heart
Veins
Venules
23
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
24
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
25
Blood Vessels
Arteries
Arterioles
Venules & Veins
• Carry blood towards the heart
Heart
Capillaries
• Thin-walled; large diameter
• One-way to prevent backflow
Veins
Venules
26
Blood Vessels
Skeletal Muscle Pump:
Vein Valve:
27
Blood Vessels
Varicose veins occur if the vein valves become inefficient
28
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
(a) Normal artery
Endothelium
Plaque
50 µm (b) Partly clogged artery
29
250 µm
Thought Question:
If you are an athlete who trains at high elevations, what
happens if you compete at a lower elevation?
30
Overview
Living things process energy
• They need oxygen for this - Why?
31
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
32
Gas Exchange Systems
•
Aquatic gas exchange
Gills
• Elaborately folded ( surface area)
• Contain capillary beds
• Gill size inversely related to [O2]
• Large gills = low [O2]
33
Gas Exchange Systems
•
Dissolved O2 is < 1% of
water (21% of air)
•
Countercurrent
exchange increases
efficiency
Fish Efficiency
34
Gas Exchange Systems
Reptiles & Mammals use lungs exclusively
• Lack permeable skin
• Lungs are more efficient
– Especially birds!
35
Mammals
Human Respiration
•
•
•
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)
36
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
37
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.
Human Respiration
1 Inhaled air
8 Exhaled air
• 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
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
39
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
40
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
41
Breathing Mechanisms
• Inhalation:
Rib muscles
contract to
expand rib
cage
Diaphragm
contracts
(down)
expands the
volume of
thorax and
lungs
1
Rib cage
expands.
2
Air
inhaled.
Rib cage gets
smaller.
Air
exhaled.
Lung
Diaphragm
• Thoracic cavity expands, produces negative pressure
which draws air into the lungs
42
Breathing Mechanisms
Breathing is
involuntary
•
•
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
43