Functions of circulationFunctions of circulation

To transport:

1. Solutes

- gases

- nutrients

- chemical wastes

- chemical signals- hormones

2. Heat - insects

3. Force

- use in locomotion (e.g. spiders, slugs)

- use in ultrafiltration across membranes

4. Immunity

5. Clotting

A version of proposed evolutionary relationships between animal phyla

A version of proposed evolutionary relationships between animal phyla

Radialsymmetry

Poriphera

Cnidaria

Ctenophora

Platyhelmintha

NematodaAnnelida

ArthropodaMollusca

Echinodermata

Chordata

Unicellularorganisms

Hemichordata

Vertebrata

No body cavities

Urochordata

Multicellulariity

No tissues

True tissueorganization

Bilateral symmetry

Have body cavitiesand blood vascularsystem

Body cavitydevelops frommesoderm

Body cavitydevelops fromother cells

Evolution of Circulatory systems

Comparative circulatory systems

1. Pump

2. Channels

3. Blood/Hemolymph

Components of circulation systemComponents of circulation system

Methods of circulationMethods of circulation

Circulation of external medium in Poriphera and Cnidaria(propulsion by cilia, flagella, or muscle contraction)

Open circulatorysystem of arthropods and most molluscs

heart

hemocoelheart

respiratorysurface

Closed circulation in annelids and cephalopod molluscs; respiratory surface may be skin or gills

Closed Open•Blood remains in vessels •Blood directly bathes tissues

•High pressure •Usually lower pressure

•Regulate flow to each organ •Less regulated flow

•Return to heart rapid •Return to heart slower

•Found in: •Found in:

vertebrates, echinoderms, most arthropods, urochordates

cephalopods* (why?) most other molluscs

annelids*

Open vs. closed systemsOpen vs. closed systems

Vertebrate respiratory mechanismsVertebrate respiratory mechanisms

Efficiency of O2 extraction

Types of pumps:Types of pumps:

Peristaltic e.g. squirt; insect; worms

Contractile chamber e.g. vert. branchial heart

Tube chamber with separate muscles e.g. vert. veins

Flow in rigid tubesFlow in rigid tubes

Q = (P1-P2) š r2

8 L

Poiseuille’s LawFlow in a rigid tube can be described by:

Q is flow volume rate

(P1-P2) is pressure diff.

r is radius of tube

L is length of tube

is fluid viscosity

Average flow velocity will be flow volume rate Q divided by the x-sectional area

Q = Velocity

š r2

Q = P / R

Flow dynamicsFlow dynamics

E=(pv)+(mgh)+(1/2mu^2

Bernoulli’s theorem: Energy = Pressure + Kinetic + Gravity

Where does the energy go?

Flow dynamicsFlow dynamics

assume flow rate steady (no other path)

Bernoulli’s theorem: Energy = Pressure + Kinetic + Gravity

Flow from high E to low E

(not high P to low P)

compliance- (1/spring constant)

• Veins are volume reservoir and high compliance. Terrestrials!! Stand up and you might get a head rush, which is actually an “out of head rush”. Compensated by adrenergic fibers. If you prick me and I bleed, do I not vasoconstrict?

• Arteries are pressure reservoir. Less compliance. Smooth heartbeat. Keep pressure relatively constant to not strain capillaries. Also maintain efficiency of diffusion with constant velocity.

Vessels are not rigid tubesVessels are not rigid tubes

The body plan of platyhelminths makes diffusion an effective mechanism of transport.

The body plan of platyhelminths makes diffusion an effective mechanism of transport.

O2

nutrients

Fick equation:

J = k(Cs - Cx)

where J = quantity of a commodity moved per unit time

k = a constant related to how readily the commodity can move

Cs = concentration at the source

Cx = concentration some distance away from the source

Only good when: very small, very thin, very inactive--or all three

What energy drives this?

S/V= 6 L2/L3

radial canal

Each canal is lined with beating cilia

ring canal

Aequorea victoria,

A very simple distributing system: the gastro-vascular system of Cnidaria

A very simple distributing system: the gastro-vascular system of Cnidaria

Open circulation in insectOpen circulation in insect

septa

Low metabolism?

Pulsatile organs

Dorsal diaphragm

Nerve cord

Insect circulationInsect circulation

Anterior dorsal aorta peristalsis

External muscles assist filling of dorsal heart (“suction”)

Accessory pumps for antennae, legs, wings

Typical crustacean circulation

THE ANIMAL OF THE DAY

Hagfish (Ph:Chordata; ?:Agnatha)THE ANIMAL OF THE DAY

Hagfish (Ph:Chordata; ?:Agnatha)

<2 feetWhy is it interesting?

• Unlike other chordates, hagfish possess several hearts.• A systemic heart & accessory hearts to help with venous return.• Mostly closed circulation, but some sinuses w/o endothelium.• As much as 80% of O2 through skin.• Systemic heart is myogenic, & not innervated. • Blood pressure is quite low.

THE ANIMAL OF THE DAY

Hagfish (Ph:Chordata; ?:Agnatha)THE ANIMAL OF THE DAY

Hagfish (Ph:Chordata; ?:Agnatha)

Amphibian (bullfrog, Rana)Amphibian (bullfrog, Rana)

separate at high flow rates

S = O2 saturation

What happens when the frog dives?

* crocodiles dive too???

Control of heart rateControl of heart rate

1. Neurogenic hearts- beat initiated by CNS

- annelids, crustaceans, arachnids

2. Myogenic hearts - they got rhythm

- vertebrates, most molluscs, some insects

- are modulated by autonomic CNS

sympathetic v. parasympathetic input

(noreprinephrine v. acetyl choline)

How change amount transported?How change amount transported?

The volume transported over time (Q) can be changed by:

1. Increased rate of pumping (f). e.g birds, mammals

2. Increase volume (V) for each stroke of the pump.

e.g. fish

3. Increased carrying capacity of the fluid

(i.e. blood).

Q = f • V

Each of these can account for individual differences or species diff.

Heart rate decreases w/sizeHeart rate decreases w/size

mammals

Heart rate decreases w/ mammal sizeHeart rate decreases w/ mammal size

log scale

log scale mammals Why? (slope)

Other methods?

(predict slope)

logarithmic relationship: r = k • M b (b = slope = –.25)

log r = log k • b(logM)

Heart mass directly proportional to body mass (0.6%) in mammals

Heart mass directly proportional to body mass (0.6%) in mammals

Stroke volume is proportional to body mass in mammals, and can not account for phylogenetic variation in metabolism.

h.m. = k • b.m 0.98

Heart rate v. Stroke volumeHeart rate v. Stroke volume

*

* What else is changing?

Lower volume Q compensated by carrying capacityLower volume Q compensated by carrying capacity

Hemocyanin is an O2 carrying pigment found in many invertebrate bloods. Unlike Hb, it is dissolved in the hemolymph.

The total cross-sectional area of the vessels increases with distance from the heart.

Consequently, the velocity of flow decreases, and then increases after passing the capillaries.

Why?

Q = Velocity

š r2

Blood pressure decreases away from heartBlood pressure decreases away from heart

As x-sectional area increases, pressure decreases in arterioles.

When x-sectional area decreases again in venules, the pressure does not return due dissipation due to friction w/ capillaries.

Distribution of blood

Control of cardiovascular systemsControl of cardiovascular systems

Baroreceptors

- atrial tonic receptors cause reflexive compensation

Chemoreceptors (CO2, O2, pH)

- if CO2 increases or O2, pH decrease, then slow heart if not breathing (how maintain B.P.?)

Stretch receptors

- increased atrial volume changes hormones to inc. urine

Thermoreceptors

Sympathetic v. parasympathetic centers & signals

Feedback control in circulationFeedback control in circulation

Control of capillariesControl of capillaries

Nervous system:

- Sympathetic norepinephrine to -adrenergic receptors.

- Parasympathetic ACh release.

(effects on heart rate?)

Local control:

NO; peptides; histamine

Adaptation to posture changesAdaptation to posture changes

tree snakes have tight skin and anteriorly displaced hearts

ground snakes will pass out if held upright too long

Pressure in humans

Giraffe (Ph:Chordata, Ge:Giraffa)Giraffe (Ph:Chordata, Ge:Giraffa)

Lowering head could result in aneurysm.

Giraffe (Ph:Chordata, Ge:Giraffa)Giraffe (Ph:Chordata, Ge:Giraffa)

• prehensile tongueWhat color?

• lower heart pressure & vasodilation

• tight skin around legs prevents pooling

Don’t worry, sea slugs also have the same problem

Don’t worry, sea slugs also have the same problem

1) Vasodilation in muscles; reduce resistance, reflex increases cardiac output.

2) Increased heart rate and force; stroke vol. in fish.

3) Release RBCs from spleen.

ExerciseExercise

Diving verts need to limit consumption of O2.

If CO2 builds up, and lungs not stretched, then peripheral vasoconstriction -> reduced heart rate.

(vice-versa if lungs stretched)

Bradycardia shown by forced dive animals.

Not in free diving animals, unless chased.

DivingDiving

Distribution of blood flow

Relative osmotic pressure & exchangeRelative osmotic pressure & exchange

not quite even; lymph

Ultrafiltration.

protein colloids regain some fluid

Phylogeny of respiratory pigments

Respiratory Pigments