437lect19 ch20-24 2005

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Lecture 19, 25 Oct 2005Chapter 20-24

Circulation, Oxygen and Carbon Dioxide Transport

Vertebrate PhysiologyECOL 437 (aka MCB 437, VetSci 437)

University of ArizonaFall 2005

instr: Kevin Boninet.a.: Kristen Potter

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1. Circulatory System 2. Respiration

Text:Chapters 23 & 24(skip the invert material if you like)Then chapters 21 & 22(skim Chapter 20)

14-25, Vander 2001

3Knut Schmidt_Nielsen 1997

Gravityand BP

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(Eckert, 12-4)To

Lungs

From body

To BodyviaAORTA

FromLungs

Mammalian Heart

Chordae tendinae

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(Eckert, 12-8)

(Q,R,S masks atrial repolarization)6

(Eckert, 12-8)

P

Q, R, S

T

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714-25, Vander 2001

WiggersDiagram

Valves open/close where pressure curves cross

760 mmHg = 1 atm= 9.8 m blood

1:2

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Sherwood 1997

Atrial Kick

Heart filled ~same with increased HR

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Sherwood 1997

Vander 2001

Frank-Starling Curve

Systole = Ventricular Emptying

Diastole = Ventricular Filling (rest)

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Cardiac Output:

CO = cardiac output (ml/min from 1 ventricle)

SV = stroke volume (ml/beat from 1 ventricle)

= EDV – ESV (end-diastolic – end-systolic volume)

HR = heart rate (beats/min)

CO = HR x SV

- Heart can utilize different types of energy sources (unlike brain)

MABP = CO x TPRMABP = DP + 1/3(SP-DP)

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Knut Schmidt-Nielsen 1997

Exercise

OxygenConsumptionX 20

Cardiac Output 6x

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Cardiac Output Control

Sympathetic speeds heart rateand increases contractility

1. Norepinephrine binds to beta1 adrenergic receptors

2. Increases cAMP levels and phosphorylation

3. Activates cation channels (Na+) and increases HR

4. Epi and Norepi activate alpha and beta1adrenoreceptors which increase contractility and rate of signal conduction across heart

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13Vander 2001

How increase contractility?

More Ca2+

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HR control

Parasympathetic vs. Sympathetic

(Eckert, 12-5)

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HR control

Parasympathetic slows heart rate

-Innervate Atria (Vagus nerve = Xth cranial nerve)

-Cholinergic (ACh)

-Alter SA node pacemaker potential by ⇑ K+ permeability

⇓ Ca2+ permeability

Parasympathetic innervation of AV node slows passage of signal between atria and ventricles

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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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(Eckert,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

(Eckert, 12-27)~Constant P and Q at Capillaries! 20

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

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

(Eckert,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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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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Baroreceptors 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

(Eckert, 12-43)

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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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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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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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stretch

temp.O2CO2pHadenosineK+

Decreased O2 levels with opposite effect in lungs

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(Eckert, 12-45)

-Vasodilation-Relaxation

-Viagra acts by blocking breakdown of cGMP

NO (nitric oxide)

Released fromvascular endothelium:

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-Vasodilation

Histamine

Released in response to injury of connective tissue and leukocytes:

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(Hill et al., 2004Fig 23.11)

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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 pressure36

(Eckert, 12-25)

Summed resistance reduces pressure…

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(Eckert, 12-23)Total Flow Rate same all along Circulatory System

River

Lake

River

38(Eckert, 12-24)

Shapes of curves slightly different because of RBCs (viscosity)

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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

40Hill et al., 2004, Fig. 21.1

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Lung Anatomy

Nonrespiratory-Trachea ->-Bronchi ->-Bronchioles ->

Respiratory-Terminal bronchioles ->-Respiratory bronchioles ->-Alveoli

-Cilia and Mucus

(Eckert, 13-21)

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(Eckert, 13-22)

-Gas Diffusion Barriers:

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43Hill et al., 2004, Fig. 20.4 44Hill et al., 2004, Fig. 20.4

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Lung Ventilation

-Small mammals with greater per gram O2 needs and therefore greater per gram respiratory surface area

-Dead Space (anatomic and physiological)

Swan (Eckert, 13-24)

46(Eckert, 13-23)

Lung Ventilation

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Mammalian Ventilation

-lungs are elastic bags

-suspended in pleural cavity within thoracic cage (ribs and diaphragm define, fluid lines)

-low volume pleural “space” between lung and thoracic wall

-negative pressure to inflate lungs (increase volume)

-pneumothorax

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Mammalian Ventilation (Eckert, 13-28)

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Mammalian Ventilation

(Eckert, 13-30)

-expiration usually passive


MammalianLung

Alveoli and Capillaries

RBC (not to scale)


Bird Lung Ventilation

Unidirectional!!

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Bird Ventilation

(Eckert,13-32)

-lung volume changes very little, air sacs instead

Unidirectional

(Eckert,13-32)

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Knut Schmidt_Nielsen 1972

Bird LungParabronchi

Mammal LungAlveoli

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Frog Ventilation

(Eckert, 13-33)

-Positive pressure ventilation

1. Into mouth (buccal cavity)

2. Close nares, open glottis and force air into lungs by raising buccalfloor

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Pulmonary Surfactants-Reduce liquid surface tension in alveoli

-Lipoproteins

-keep alveoli from getting stuck closedAtelectasis = collapsed lung

-premature babies may need artificial surfactant

-Allows for compliance and low-cost expansion of lung


Panting Dogs?


Fish Gill

58Hill et al., 2004, Fig. 20.3

59Hill et al., 2004, Fig. 21.10 60Knut Schmidt_Nielsen 1997

Relative Gill Surface Area in Fishes

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Knut Schmidt_Nielsen 1997

Fish Gill

-breathing in water

-need much higher ventilation rate

-unidirectional

-pump water across gills (or ram ventilation)

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GILLS – breathing in water

-need much higher ventilation rate

-unidirectional

-pump water across gills (or ram ventilation)

(Eckert, 13-40)

Floor of Mouth (buccal cavity)


Lake Titicaca Frog

(Bolivian Navy; Peru-Bolivia border)

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Hill et al., 2004, Fig. 21.8Gas ExchangeAcrossSkin

65Hill et al., 2004, Fig. 21.7 66Hill et al., 2004, Fig. 21.7

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Rate and Depth Regulation -Primarily via CO2changes (central)

-O2 controls respiration in aquatic vertebrates

(Eckert, 13-46)

-Innervate MedullaryRespiratory Center(phrenic nerve to diaphragm and intercostals)

-Peripheral ChemoreceptorsPO2, PCO2, pH

-Emotions, sleep, light, temperature, speech, volition, etc.

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Rate and Depth Regulation

(Eckert, 13-48)

-Central Chemoreceptors

Long term

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To Diaphragm

alveolar

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Hering-Breuer reflex

-Stimulation of stretch receptors inhibits medullaryinspiratory center

-Prevent overinflation

-Ectotherms often breathe intermittently

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(Eckert, 13-45)

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1

2

2

To Diaphragm

72Hill et al., 2004, Fig. 20.5

Oxygen Partial Pressure

437lect19 ch20-24 2005

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