Lecture 18, 30 Oct 2003Chapter 12, Circulation (con’t)

Chapter 13, Respiration, Gas Exchange, Acid-Base Balance

Vertebrate PhysiologyECOL 437

University of ArizonaFall 2003

instr: Kevin Boninet.a.: Bret Pasch

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Vertebrate Physiology 437

1. Circulation (CH12)

2. Blood-Gas Chemistry (CH13)

3. Announcements...

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14-34, Vander 2001

See (12-32)

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 4:00 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:

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Drew StasiakChem Minor

Elena CostinMCB

Gabriel ReinhardtMCB

Hemodynamics in Vessels

Vander 2001

14-11, Vander 2001

Flow depends primarily on pressure gradient and resistance

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Hemodynamics- Poiseuille’s Law:

Flow rate

8L

Q = (P1 – P2)r4

Pressure Gradient

radius4

length

viscosity

Use to approximate flow

Small change in radius large change in flow rate

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Hemodynamics- From Poiseuille’s Law:

Resistance

Q

R = (P1 – P2)

Pressure Gradient

radius4

Flow rate

viscosity

Small change in radius large change resistance

= 8L

r4

length

Modifiable if vessel distensible under pressure

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(12-25)

Summed resistance reduces pressure…

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(12-23)

Total Flow Rate same all along Circulatory System

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River

Lake

River

(12-24)

Shapes of curves slightly different because of RBCs (viscosity) and fact that they tend to flow in middle of lumen

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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

14-34, Vander 2001

(12-27)~Constant P and Q at Capillaries!

See (12-32)

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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 permeable1. continuous

2. Fenestrated (kidney, gut)

3. Sinusoidal (liver, bone)

Less permeable

- Movement across walls, between walls, in vesicles

More permeable

- Bulk Flow…

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Bulk Flow…

Fluid Pressurevs.Osmotic Pressure

(12-38)

Filtration > UptakeLymph System to return excess fluid

Faster than diffusion

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Bulk Flow… - Edema

- No RBCs; therefore not red

Lymph System

- Starvation

- Lungs

- Kidneys

- 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 Regulation1. Feed Brain and Heart First

2. Next Feed Tissues in Need3. 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 RegulationBaroreceptors increase AP firing rate when BP increases

Sensed at carotid sinus, aortic arch, subclavian, common carotid, pulmonary

Usually leads to Sympathetic suppression to decrease BP

(12-43)

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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)

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What about when not diving?

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 RegulationExtrinsic vs. Local Control

Neuronal or HormonalMost arterioles with sympathetic innervationAlso 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 RegulationExtrinsic vs. Local Control

Neuronal or HormonalNeuropeptide Y

- Acts by reducing IP3 levels

-decreases coronary blood flow-decreases heart contractility

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Circulatory System RegulationExtrinsic vs. Local Control

stretch

temp.O2

CO2

pHadenosineK+

Decreased O2 levels with opposite effect in lungs

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Circulatory System RegulationExtrinsic vs. Local Control

(12-45)

-Vasodilation-Relaxation

-Viagra acts by blocking breakdown of cGMP

NO (nitric oxide)

Released from vascular endothelium:

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Circulatory System RegulationExtrinsic vs. Local Control

-Vasodilation

Histamine

Released in response to injury of connective tissue and leukocytes:

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Chapter 13

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

2 2 2

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End

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