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 andvery entertaining speaker, he has won the most prestigious teachingawards 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

8Lη

Q = (P1 – P2)πr4

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

= 8Lη

πr4

length

Modifiable if vessel distensible under pressure

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(12-25)

Summed resistancereduces pressure…

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(12-23)

Total Flow Rate same allalong Circulatory System

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River

Lake

River

(12-24)

Shapes of curves slightly different because ofRBCs (viscosity) and fact that they tend to flowin 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) inchest to aid blood flow to heart

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Microcirculation

- endothelium in capillaries is permeable

1. 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 > Uptake

Lymph 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 lowerextremities of aquatic organismsnot pool as it may do in legs of

humans, giraffes, etc.?

FISH:

Blood tends to pool in tail b/c inertia andcompression 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 First2. Next Feed Tissues in Need3. Maintain volume, prevent edema, etc.

BaroreceptorsChemoreceptorsMechanoreceptorsThermoreceptors

Info. integrated at Medullary Cardiovascular Centermedulla 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

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

Usually leads to Sympatheticsuppression 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 pHleads 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+ excretionand therefore greater urine output

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Circulatory System Regulation

Extrinsic vs. Local Control

Neuronal orHormonal

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), levelof catecholamines (epi, norepi), etc.

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Circulatory System Regulation

Extrinsic vs. Local Control

Neuronal orHormonal

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.O2CO2pHadenosineK+

Decreased O2 levels withopposite effect in lungs

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Circulatory System Regulation

Extrinsic vs. Local Control

(12-45)

-Vasodilation-Relaxation

-Viagra acts by blockingbreakdown of cGMP

NO (nitric oxide)

Released fromvascular endothelium:

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Circulatory System Regulation

Extrinsic vs. Local Control

-Vasodilation

Histamine

Released in responseto injury of connectivetissue and leukocytes:

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Chapter 13

Gas exchangeAcid-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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