As Blood Transport

8/8/2019 As Blood Transport

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F211

Exchange and Transport

Heart and Circulation


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LO: explain the need for transport systems in multicellular

animals in terms of size, activity and surface area to volume

ratio

All cells need energy, where do they get it from?

How is the energy released?

How do the food molecules and oxygen get to the cells in

simple organisms and complex organisms? How does the organisms activity level influence how fast the

food molecules and oxygen have to get to the cells?

Does the fact that some organisms are ectothermic (cold

blooded) and some are endo thermic (warm blooded) affecthow fast these molecules need to be supplied to cells?


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What are the features of an efficient oxygen and

nutrient molecule transport system?

A fluid medium to carry molecules

A pump to push the fluid round

Exchange surfaces for oxygen and nutrients toenter and leave the blood

Vessels to carry the fluid medium round the

organism Separate circuits to pick up oxygen from the

environment and deliver it to the cells.


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Explain the meaning of the terms single and double

circulation with reference to the systems of fish and mammals

What are the disadvantages of

this system?

Heart cannot pump at highpressure

Reduced blood pressure in

capillaries of gills to reduce

chance of damage

Slow rate of flow in rest of body

Limited rate of delivery of oxygen

and glucose to tissues

Fish have a single circulation

system. Blood flows from the heartto the gills and then on to the

body before returning to the heart


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What are the advantages of themammalian system?

Heart can increase blood pressure

after blood passes through lungs Increased speed of delivery

Increased blood pressure in systemicsystem, oxygen and glucose get totissues quickly

Lower blood pressure in pulmonarysystem decreases the chance ofdamaging capillaries in the lungs

Mammals have double

circulatory systems. One circuit

(pulmonary) takes blood from

the heart to the lungs and back,the other(systemic) takes blood

from heart to body tissues and

back.


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To see how the heart and

circulatory systems haveevolved go to:

http://mhhe.com/biosci/genbio/biolink/j_explorations

/jhbch05.htm


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Learning outcomes

Describe the external and internal structure of

the mammalian heart.

Explain the differences in thickness of the

walls of the different chambers of the heart in

terms of their functions.


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Heart diagrams

Label as much as you can on the diagram

using the labels on the sheet supplied.


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External view of Heart


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Describe the cardiac cycle with reference to the action of the

valves in the heart.


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For animation of the cardiac cycle and explanation of

the changes in pressure that take place

http://library.med.utah.edu/kw/pharm/hyper

_heart1.html


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Be able to link

changes in pressure

and volume shown on

the graph with the

stages of the cardiac

cycle.


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Control of the Cardiac cycle

Read text book pages 58-59

Make notes on the meaning of:

Myogenic

Sinoatrial nodeAtrioventricular node

Purkyne (Purkinje) tissue


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Control of the cardiac cycle

Non conducting

tissue


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Interpret and explain electrocardiogram (ECG) traces

with reference to normal and abnormal heart activity.


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ECG interpretation

P-R interval (usually 0.12 to 0.2 secs) greater than 0.2 secs means a delay

in the transmission of the excitation wave to the ventricles due to damage

to the AV node or Purkine tissue

QRS complex is usually 0.06 to 0.1 sec in duration, if longer it indicates

problems with the conduction of the excitation wave across the ventricles. Small unclear P waves indicate atrial fibrillation due to damage to the SAN,

this means that the ventricles are not filled during atrial systole, so

ventricle contraction doesnt expel the normal amount of blood.

No regular PQRS pattern discernible indicates fibrillation of the atria and

ventricles, uncoordinated weak contractions of the chambers so thatblood is not pumped out of the heart effectively.

Deep S waves indicate an increase in ventricle thickness due to increase in

blood pressure.


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Interpret and explain electrocardiogram (ECG) traces with reference to

normal and abnormal heart activity.

P shows atrial excitationjust prior to atrial

systole QRS shows ventricle excitation that causes

ventricular systole

T shows repolarisation of the heart muscle

during diastole

Top ECG normal

Any changes to the shape and length of each

section of the trace can indicate heart

abnormalities

Raised ST section indicates heart attack, no

ion pumps workinging to repolarise cells

Fibrillation is unco-ordinated contraction ofeither / or / both atria and ventricles

Hypertrophy: extra muscle growth to

overcome increased blood pressure due to

blockages in blood vessels


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Complete the question on ECG traces


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Explain the meaning of the terms open and closed

circulatory systems with reference to insects and fish

Closed circulatory system

Vertebrates, and a few invertebrates, have a

closed circulatory system. Closed circulatory

systems have the blood closed at all times

within vessels of different size and wall

thickness. In this type of system, blood is

pumped by a heart through vessels, anddoes not normally fill body cavities.

Open circulatory system

The open circulatory system is common to

molluscs and arthropods. Open circulatory

systems (evolved in crustaceans, insects,

mollusks and other invertebrates) pump blood

into a hemocoel with the blood diffusing back to

the circulatory system between cells. Blood ispumped by a heart into the body cavities, where

tissues are surrounded by the blood.


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Describe the structure of arteries,

veins and capillaries


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Describe the structures and functions

of arteries, veins and capillaries

Cut up the table thatyou have been givenand sort it out!

When completedcollect a correct version

Learn the sequence oftissues that make up

the walls of arteries andveins. ie: endothelium,elastic fibres, smoothmuscle, collagen fibres

Make notes on thefunctions of:endothelium, elastic

fibres, smooth muscleand collagen fibres

How does skeletalmuscle help blood flowback to the heart?

What are valves for inveins?


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Features of arteries, veins and

capillariesFeature Arteries Capillaries veins

Wall thickness Thicker than veins Very thin, walls only

one cell thick

Thinner than arteries

Muscle in wall Thick muscle layer NO muscle layer Thin muscle layer

Elasticity of wall Thick layer of elastic

tissue

NO elastic tissue Little elastic tissue

Inner surface Smooth endothelium,

often folded, can

unfold when stretched

Only one layer of cells

made of endothelium

Smooth endothelium,

not folded

Shape of cross section Round round Irregular or flattened

Size of lumen small Tiny (only 7 m across) Larger than artery

Direction of blood flow From heart towards

organs

From arterioles to

venules

From organs back to

heart

Pressure of blood high low low

valves No valves apart from

at exit of ventricles

(semi-lunar valves)

No valves Pocket valves all along

length


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Sequence of tissues in arteries, veins

and capillaries


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Functions of tissues

Endothelium provides a smooth lining that offers little friction to slow down the

passage of blood. It may be folded lining arteries to allow it toexpand when blood surges though and the artery stretches

Elastic fibres-

allow vessels to stretch as high pressure blood flows through; andrecoil to maintain pressure in arteries when heart is in diastole.

Smooth muscle

in arteries and arterioles can be contracted to constrict the vesseland decrease the volume of blood flowing through

Collagen-

forms a strong external layer to withstand high pressure generatedby ventricular systole


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Importance of pocket valves in veins

Because blood pressureis low in veins there is atendency for blood topool due to the effects

of gravity. Valves prevent blood

flowing backwards

Veins are situatedbetween skeletal muscle,

when this contracts itsqueezes blood up theveins and assists in itsreturn to the heart


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Explain the differences between blood, tissue

fluid and lymph.Feature Blood Tissue fluid Lymph

Cells Erythrocytes(red) Leucocytes

(white) and platelets

phagocytes lymphocytes

Proteins Hormones and plasma

proteins

Hormones and protein

secreted by body cells

Few proteins

Fats Some transported as

lipoproteins (HDL, LDL)

NONE More than in blood (absorbed

from lacteals in small intestine)

Glucose 80-120mg per 100cm3 Less than in blood Gets

absorbed by cells

Less than in blood and tissue

fluid

Amino acids More than in other fluids Less than in blood Gets

absorbed by cells


fluid

Oxygen More than in other fluids Less than in blood Gets

absorbed by cells


fluid

Carbon dioxide Little More than in blood.Gets

absorbed by cells

More


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Describe how tissue fluid is formed

from plasma.

Arteries branch into arterioles andthen into capillaries around thetissues of organs

The contractions of the heartmaintain some pressure in thecapillaries (hydrostatic pressure)

This squeezes fluid out betweenthe endothelial cells of thecapillaries

The fluid contains oxygen, aminoacids and glucose; but no cellsapart from a few phagocytes andno plasma proteins which are toolarge to go through the pores


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Exchange in the capillary bed

Tissue fluid bathes the cells Nutrients (glucose, mineral ions

and amino acids) and oxygenare taken into cells by diffusion,

facilitated diffusion and activetransport

Waste such as CO2 and urea areremoved from cells by similarprocesses

Tissue fluid must now return tothe circulatory system tomaintain blood volume


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How does the fluid return to the

blood? Plasma proteins which remain in the

blood give blood a lower waterpotential than tissue fluid so watertends to flow back into thecapillaries down a water potentialgradient, solutes diffuse down theirconcentration gradients.

At the arteriole end of the capillaryhydrostatic pressure is greater thanosmotic pressure (solute potential)so there is net outflow from thecapillary

At the venule end of the capillarythe hydrostatic pressure hasdropped considerably due to fluidleaving the blood, it is now lowerthan the osmotic pressure(solutepotential);so there is net inflow tothe capillary


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Importance of the lymphatic system

Without the lymphatic system tissuefluid could accumulate and causeoedema

The lymph nodes contain largenumbers of phagocytic lymphocytesthat engulf and kill bacteria. Theyare part of the immune system


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Uptake of oxygen by haemoglobin

Rate of uptake of oxygen depends onthe partial pressure of oxygen

Partial pressure can be thought of asthe amount of a particular gas in amixture of gases measured in kPa

At low partial pressures it is difficult for

oxygen molecules to associate withhaemoglobin; it is hard for the firstoxygen molecule to get in to thecomplex and reach the haem group.

Once one oxygen molecule is in, the Hbmolecule changes shape and this makesit easier for more oxygen to get in.

Second and third O2 moleculesassociate quite easily To get the fourth one in and get almost

100% saturation the partial pressureneeds to be very high


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Uptake of oxygen by haemoglobin

This means that in areaswhere the partial pressureof oxygen is high,such asthe lungs, haemoglobin is

almost saturated. In areas where the partial

pressure of oxygen is low,such as respiring tissues,the oxygen dissociates from

the haemoglobin easily andthen diffuses out of theblood plasma to the cellsthat need it.


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Uptake and release of oxygen by

haemoglobin

faet

Foetal haemoglobin has ahigher affinity for oxygenthan adult haemoglobin

As the mothers blood

flows through theplacental tissue the PO2 islow so the oxygendissociates from thehaemoglobin

The foetal haemoglobinpicks up the releasedoxygen.


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Oxygen availability at altitude

The % of oxygen in the air is the same as at sea level but theatmospheric pressure is much lower

This means that fewer molecules of oxygen are inhaled per

breath, so % saturation of haemoglobin in the lungs is greatly

reduced

Lack of oxygen at altitude results in heavy breathing, and

increased heart rate as the body tries to maintain normal

levels of oxygen supplied to tissues.

Dizziness, headaches, nausea, increasing confusion, inability

to walk straight may follow

In extreme cases this can turn into HACE (high altitude

cerebral edema) or HAPE (high altitude pulmonary edema)

which are potentially life threatening conditions unless the

person descends to an area where oxygen availabilty is higher

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