Lecture 18, 30 Oct 2003

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Lecture 18, 30 Oct 2003 Chapter 12, Circulation
(cont) Chapter 13, Respiration, Gas Exchange,
Acid-Base Balance Vertebrate Physiology ECOL
437 University of Arizona Fall 2003 instr
Kevin Bonine t.a. Bret Pasch
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Vertebrate Physiology 437
1. Circulation (CH12) 2. Blood-Gas
Chemistry (CH13) 3. Announcements...
See (12-32)
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Thursday, 30 October -- the ARLDN's 2003 Edmund
A. ArbasLecturer, Prof. Peter M. Narins from the
Dept. of Physiological Science atUCLA, will give
his public lecture in Economics 110 at 400 pm.
The titleof his lecture is "Science on Seven
Adventures of an ExpeditionaryBiologist."Narins
is renowned for his elegant work on hearing and
auditorycommunication in frogs and is a world
leader in neuroethology, animalbehavior, and
auditory neurophysiology. He is also a legendary
fieldbiologist, having led 39 expeditions to
remote and exotic field sites onseven continents
over the last quarter century. A masterfully
clear and very entertaining speaker, he has won
the most prestigious teaching awards atUCLA.
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Name that student
Drew Stasiak Chem Minor
Elena Costin MCB
Gabriel Reinhardt MCB
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Hemodynamics in Vessels
Flow depends primarily on pressure gradient and
resistance
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Hemodynamics
Use to approximate flow
- Poiseuilles Law
Pressure Gradient
radius4
Flow rate
Q (P1 P2)?r4
8L?
viscosity
length
Small change in radius ? large change in flow rate
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Hemodynamics
- From Poiseuilles Law
Pressure Gradient
length
Resistance
viscosity
R (P1 P2)
8L?
?r4
Q
radius4
Flow rate
Small change in radius ? large change resistance
Modifiable if vessel distensible under pressure
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Summed resistance reduces pressure
(12-25)
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Total Flow Rate same all along Circulatory System
(12-23)
River
River
Lake
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Shapes of curves slightly different because of
RBCs (viscosity) and fact that they tend to flow
in middle of lumen
(12-24)
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Peripheral Circulation
- Endothelium lining vessels
- Middle layer with smooth muscle (esp. arteries)
- Outer fibrous layer
Capillaries with only Endothelium
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(12-26)
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Peripheral Circulation
Compliance vs. Elasticity
Veins vs. Arteries
Volume Reservoir vs. Pressure Reservoir
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Volume Reservoir vs. Pressure Reservoir
See (12-32)
(12-27)
Constant P and Q at Capillaries!
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Venous System
- low pressure (11 mm Hg or less)
- thin walled veins with less muscle
- more compliant and less elastic
- valves
- blood moved by skeletal muscle (and smooth)
- breathing creates vacuum (low pressure) in
chest to aid blood flow to heart
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Microcirculation
- endothelium in capillaries is permeable
1. continuous
Less permeable
2. Fenestrated (kidney, gut)
3. Sinusoidal (liver, bone)
More permeable
- Movement across walls, between walls, in
vesicles
- Bulk Flow
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(12-38)
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Bulk Flow
Fluid Pressure vs. Osmotic Pressure
Faster than diffusion
Filtration gt Uptake
Lymph System to return excess fluid
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- Edema
Bulk Flow
- Starvation
- Lungs
- Kidneys
Lymph System
- No RBCs therefore not red
- Drains interstitial spaces
- has valves and smooth musculature
- empties into thoracic duct at vena cavae
- transport system for large hormones and fats
into blood stream
- filariasis, elephantiasis
- Reptiles and Amphibians with lymph hearts
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Giraffe example pgs. 504-505
Why does blood in the lower extremities of
aquatic organisms not pool as it may do in legs
of humans, giraffes, etc.?
FISH
Blood tends to pool in tail b/c inertia and
compression waves when swimming

• Veins in middle of body
• Accessory caudal (tail) heart in some species

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Circulatory System Regulation
1. Feed Brain and Heart First
2. Next Feed Tissues in Need
3. Maintain volume, prevent edema, etc.
Baroreceptors
Chemoreceptors
Mechanoreceptors
Thermoreceptors
Info. integrated at Medullary Cardiovascular
Center
medulla oblongata and pons
Depressor Center ? Parasympathetic Effectors
Pressor Center ? Sympathetic Effectors
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Circulatory System Regulation
Baroreceptors increase AP firing rate when BP
increases
(12-43)
Sensed at carotid sinus, aortic arch, subclavian,
common carotid, pulmonary
Usually leads to Sympathetic suppression to
decrease BP
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Circulatory System Regulation
Arterial Chemoreceptors in carotid and aortic
bodies
(More details when discuss ventilation)
e.g., low O2, high CO2, low pH leads to
bradycardia and peripheral vasoconstriction
(diving and not inflating lungs)
What about when not diving?
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Circulatory System Regulation
Cardiac Mechanoreceptors and Chemoreceptors
Alter heart rate AND blood volume
e.g., ANP (Atrial Natruiretic Peptide) released
in response to stretch
- leads to increased Na excretion and therefore
greater urine output
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Circulatory System Regulation
Extrinsic vs. Local Control
Neuronal or Hormonal
Most arterioles with sympathetic innervation
Also respond to circulating catecholamines
-At high levels, alpha adrenoreceptors are
stimulated ? vasoconstriction (to increase BP)
-At low levels, beta2 adrenoreceptors are
stimulated ? vasodilation (to increase flow to
tissue)
-Response depends on tissue type, receptor
type(s), level of catecholamines (epi, norepi),
etc.
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Circulatory System Regulation
Extrinsic vs. Local Control
Neuronal or Hormonal
Neuropeptide Y
- Acts by reducing IP3 levels

• decreases coronary blood flow
• decreases heart contractility

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Circulatory System Regulation
Extrinsic vs. Local Control
stretch temp. O2 CO2 pH adenosine K
Decreased O2 levels with opposite effect in lungs
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Circulatory System Regulation
Extrinsic vs. Local Control
NO (nitric oxide)
Released from vascular endothelium

• Vasodilation
• Relaxation

• Viagra acts by blocking breakdown of cGMP

(12-45)
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Circulatory System Regulation
Extrinsic vs. Local Control
Histamine
Released in response to injury of connective
tissue and leukocytes

• Vasodilation

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Chapter 13
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• Gas exchange
• Acid-base balance

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Gas composition in air O CO N of
dry air 21 0.03 78 pp at 760 mm
Hg 159 0.23 594 380mmHg (at
6000m) 79.6 0.11
297 Solubility in water (ml/L) 34
1,019 17
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End