bio module 3

3 factors that ffect need for exchange system

size, surface area to volume ratio, level of activity

size for need for exchange system

body surface no logner sufficient after 2 cell layers

very small - all cytoplasm very close to envirnoment in which they live, so diffusion supplies enough oxygen and nutrients to keep cells alive and active

multiellular organisms - severl layers

any oxygen or nutrients diffusing in from outside have longer diffusion pathway

diffusion too slow to enable sufficient supply to innermost cells

surface area to volume ratio for need for exchange system

small - small surface area nad volume, so SA large enough to supply all cells with sufficeint oxygen

as size increases,v olume rises more qucily than surface area

so large organisms have small ratio

organisms can increase SA by adopting different shape eg flatworm

level of activity for need for exhcange system

metabolic activity uses energy from food and requires oxygen to release energy in aerobic respiration

cells of an active organism need good supplies of nutrients and oxygen to supply energy for movement

need for energy increased in animals, eg mammals that keep themselves warm

all good exchange surfaces features

large SA to provide more space cfor molecules to pass through

often acheived by folding walls and membranes involved
eg root hairs in plants


thin barrier to reduce diffusion distance
must be permeable to substances being exchanged - shown well in alveoli of lungs

good blood supply to bring fresh supplies of molecules to one side(supply side(

keeping concentraton high, or may remove molecuels from demand side to keep concentration low

important to maintain steep concentration gradient so diffusion can occur rapidly
eg gills

lung features

alveoli - tiny folds of lung epithelium to increase SA
bronchi and bronchioles - smalelr airways leading into lungs

diaphragm - layer fo mujscle benath lungs

intercostal muscles - between ribs, contratoin of external intercostal muscles raises ribcage

trachea - main arway from back of mouth to lungs

ventilation - refreshing of air in liungs so theres higher o2 concentraiton than in blood, and lower co2 concenration

gaseosu exchange system in mnammles description

lungs and associated airways that carry air in and outof lungs

lungs - pair of inflatable sacs lying in chest cavity

air can paass into lungs through nose and along trachea, bronchi and bronchioles

finalyl reaches alveoli - where gas exhcnage takes place

protected by ribcage
ribs held together by intercostal muscles

action of muscles and diaphragm helps to produce ventilation

gas exhcange in lungs

gaases pass by diffusion through thin walls of alveoli
oxygen passes from air in alveoli to blood in capiliaries

Co2 passes from blood in air in alveoli
lungs must maintain steep concentratino gradient in each direction to ensure diffusion can continue

lung adaptations - surface area

large to provide more space for molecules to pass through

individeoul alveoli small - about 100-300/l,M across
but so numerous - total surface area of lujngs larger than skin, 70m²

alveoli lined by thin layer of moisture, evaporates and lost as we breathe out

lungs msut produce surfactant - coats internal surface of alveoli to reduce cohesive forces between water molecules, as these forces tned to make alveoli collapse

lung adaptations - thin barrier

barrier to exchange - permeable to o2 and co2

comprise d of all of alveolus and wall of blood capillary
celsl and plasma membranes readily allow diffusion of oxygen and carbon dioxide, as molecuels small and non polar

THin barrier to reduce diffusion distance

alveolus and capillary wall 1 cell thick
both squamous cells - flattened
capillaries in close contact with alveolus walls, and so narrow that red blood cells squeezed against wall - making them closer to air in alveoli

so total barrier to diffusion only 2 flattened cells

lung adaptations - good blood supply

helps to maintain steep concentraiton gradient, so gases continue to diffuse

blood system transports co2 from tissues to lungs
ensures concenration of co2 in blood higher than that in air of alveoli

so co2 diffuses into alveoli

blood also transports oxygen away from lungs
so concentration of o2 in blood kept lower than that in alveoli - so oxygen diffuses into blood

lung adaptations - ventilation

replaces used air with fresh air, bringing in more o2 and removing co2
ensures

concenration of o2 in air of alveolus remains hgiher than that in blood
concenrttion of co2 in alveoli lower than that in blood


therefore concenrtation gradient necessary for diffusion maintained

inspiration

diaphragm contracts to move down and become flatter - displaces digestive organs downwards

external intercostal muscles contract to raise ribs

volume of chest cavity increased

pressure in cehst cavity drops below atmospheric pressure
air moved into lungs

expiration

diaphragm relaxes and pushed up by displaced organs underneath
external intercostal muscles relax and ribs fall
internal intercostal muscles cna contract to help push out air more forcefully - usually only during exercise or sneezing


volume of chest cavity drecerased

pressure of liungs increases and rises above pressure in surrounding atmosphere

air moved out of lungs

cartilkage, elastic fibres, goblet cells, smooth muscle

1 - form of connective tissue
ciliated epithilkuem - layer of cells that have many hair like extensions called cilia


2 - protein fibres that can deform then recoil to original size

3- cells that secret mucus

4 - involuntary muscle that ocntracts without need for conscious thought

lung tissue adaptations

alveoli comrprised fo squamous epitheliunma nd surrounded by blood capillaries, so that distance gases diffuse very short

alveolus walls contain elastic fibres that stretch during insirptaion but then recoil to help push air out during expriation

alveolus walls so thin that may not be possible to distinguish separate celsl under light microscope

airway requirements

large enough to allow sufficient air to flow without obstructrion
supported to prevent collapse when air pressure inside low during inspiration

flexible ino rder to allow movement

airways lined by ciliated epithelium, contributes to ekeping lungs healthy

Goblet cells in eptihelium release mucus - traps pathogens

cilia then move mucus up t o top of airway, where it is swallowed

treachea and bronchi adaptations

bronchi narrower than trachea

airways suported by rings of caritlage which prveent collapse during inspriaton

in trachea rings C shaped rather than complete which allows flexibiltiy and space for food to pass down oesophagus

bronchioles adpations

much narrower than bronchi
larger bronchioles may have some cartilage but smaller ones have none

wall comprised mostly of smooth muscle and elastic fibres

smallest bronchioles end in clusters of alveoli

smooth mnuscle in airways doesnt contribute to breathing movemnets

smooth muscle and elastic tissue

muscle can contract
action of smooth muscle wil lconstrict airway

makes lumen of airway narrower

constriction of lumen can restrict flow of air to and from alveoli

controlling flow of air to alveoli might be important if there are harmful substances in hte air

contraction of smooth muscle and control of airflow not voluntary act and may occur as a result of allergic reaction

once smooth muscle conttracted, cannot reverse efect on its own

smooth muscle elongated again by elastic fibres

when muscle contracts, deforms elastic fibres
as muscles relax, elastic fibres recoil to original size and shiape to dilate airway

some overeact to substances in air and bronchioels constrict unncessarily - asthma

breathing rate, oxygen uptake, tidal volume, spirometer, vital capacity

1 - number of breathsepr minute

2 - volume of oxygen absorbed by lungs in one minute

3 - voluem ofo air inhaled or exhaled in one breath, usually measured at rest
4 - device that can measrue movement of air in and out of lungs

5- greatest volume of air that can be expelled form lungs after taking deepsest possible breath

spirometer method

float chamebr spirometer constis of chamebr of air or medical grade oxygen floating on tank fo water

during isnpriation, air drawn from chamber so lid moves down

during expiration, air returns to chamber, raising lid

movements may be recorder on data logger

co2 rich air exhaled passed through chamebr of soda lime - abrosb co2

allows measurement of oxygen consumption

precautions using spirometer

should be healthy and free from asthma
soda lime should be fresh and functioning
noa ir leaks in apparuts, would give invalid or inaccurate results

mouthpiece should be sterlised
water chamber not be overfilled or water may enter air tubes


modern spirometes small and simple handheld devices, record movements of air in an out of lungs
however many cannot measure rate of oxygen consumption

lung volumes

total volume consits of vital capacity(can be measured) and residual volme(cant be measrued using spirometer

vital capacity - measured by taking dep breath and expirng all air possibel from lungs

depends on size(height), age, gender, level of exercise

usually 2.5-5.0dm³ but above in trrained athelets

residual and tidal volume

resudal - reamins in airways and alveoli - 1.5dm³

tidal - normally measured at rest, 0.5dm³

usually sufficint to suply all oxygen requred in body at rest

calculating oxygen uptake from spirometer trace

on trace, dar wline from initial oxgyen volume(A) down to horizontal axis

another lien from final oxygen volume(B) to horizontel axis

measure length of time between points

measure volume differenc ebetween A and B
DIVIDE by time taken for htis drecearse

unit - dm3s-1

breathing rate and oxygen uptake spirometer trace

count number of peaks each minute - breathing rate, usually 12-14 per mintue at rest

oxygen uptake higher result from icnraese ddemand eg exercise

will result from increased breathing rate and deeper breaths

bony fish gills

absorb oxygen dissolved inw ater and release co2 in water

o2 concentration typically much lower than found in air

most bony fish 5 pairs of gills covered in bony plate(operculum)

each gill - 2 rows of gill filaments(primary lamellae) attached to bony arch

filaments very thin, sruface folded into many secondary lamellae(gill plates)

prvides very large surface area

bloodc apillaries carry deoxygenated blood close to surface of secondary lamellae where exchange takes place

provides very large surfacea rea

blood capillaries carry deoxygenated blood close to surface of secondary lamellae where xchange takes place

countercurrent flow

blood flows along gill arch and out along filaments to secondary lamellae
blood then flows through capillaries in opposite direction to flow of water over lamellae

arragnement creates countercurrent flow - abosrbs maimum amount of xoygen from water

ventilation in bony fish

can keep water flowing over gills using buccal-opercular pump

buccal cavity(mouth) can change volume

floor of mouth moves downwards, drawing water into buccal cavity

mouth closes and floor raised again pushing water through gills

movements of operculum coordinated with movements of buccla cavity

as water pushed from buccal cavity, operculum moves outwards
movement reduces pressure in opercular pcavity, helong wate flow through gills

insects

do not transport oxygen in blood
open circulatory system - body fluiod acts as both blood and tissue fluid

circulation slow can be affect by body movents

air filled tracheal ssytem, usppleis air directly to all respiring tissues

air enters system via proie in each segment(spiracle)

air transported into bdy throuhg serious of tuibes called trachae

divide into smaller and smaller tubes, tracheoles
ned sof tracheols opena nd fillued with tracheeal fluid

gas exchange occurs between air in racheole and tracheal fluid
some can also occur across thin walls of tracheoles


Many inscts active and need godd supply of oxygen, when tissues avctive, trcheal fluoid can be withdrawn into body to increase surface area of tracheole wall exopsed to air
more oxygen bcan be absorbed when isnect active

ventilation in insects

larger insects ventilate tracheal system by movemnts of body


many insects, sections of tracheal system expanded and have flexbibele walls

act as air sacs -c an be squeezed by action of flight muscles
repettive expansion and contration of sacs ventilate tracheal system


some insects, movement of wings alter volume of thorax
as volume decreases, air in tracheal system put under pressure pushed out of tracheal system

when thorax increase in volume, pressure inside drops and air pushed into tracheal system from outside

locusts

can alter abdomen volume by specialised brathing movements
coordinated with opening and closing valves in spiracles

as abdomen expands, spiracles at front end of body open and air enters rracheal system

as abdomen reducse in volume, spiracles at rear end of body open and air can leave tracheal system


mechanism of ventilation in insects similar to that in mammals
increase in body cavity volume reduces pressure so air enters tracheal system
decrease in volume raises pressure to push air out again

double circulatory system, single circulatory system, transport

1 - one in which blood flows through heart twice for each circuit of the body

2 - one in which blood flows throuhg heart once for each circuit of the body

3 - movement of substances such as oxygen nutrients, hormones, waste and heat around body

features of good transport system

fluid or medium to carry nutritents, oxygen and wastes around body - blood
pump to create pressrue that will psuh fluid around body - heart

exhcnage surfaces enable substance sto enter blood and leave again where they are needed - capillaries


tubes or vessels to carry blood by mass flow
two circuits - one to pick up oxygen and another to dleiver to tissues

single circulatory system

fish
blood flows through heart ocne for each circuit of body

heart —> gills —> body —> heart

double circulatory system

mammals, two separte circuits
one carries blkood to lungs to pick up oxygen - pulmonary
other - carries oxygen and nutrients around body to tissues

systemic circulation
Blodo flows through heart twice for each circuit of body

heart —> body —> heart —> lungs —→ heart

advantages of double circulation

efificient - will deliver oxygen and nutrients quickly to parts of body where needed

Blood can be mde to flow more quickly by icncreasing blood pressure created by heart

disadvangages of single circulatory ssystem

blood pressure drops as blood passes through tiny capillaries of gills
Blood has low pressure as flows towards body

will not flow very quickly



rate at whic h oxygen and nutrients dielivered to respiring tissues, co2 and urea removed, liited

fish not as metabolicalyl acgive as mammals as they do not maintain body tremperature so need less energy

doubly circulatory system features

blood perssure must not be too high in puulmonary circulation, otherwise might dmaage delicate capillaries in lungs

heart can increase pressure of blood after passed throuhg lungs so blood under higher pressrue as it flows to bdoy and flows mroe quickly


system circulation can carry blood at higher pressure than pulmonary circulation

mammals active animals and maintain body temperatreu
supplyign energy for activity and ehat needed to keep body warm requires energy from food
energy released from food in process of respiration

to releast a lot of energy, cells need gooddd supply of both nutrients nad oxyge,n, as well as removal of waste products

arteries, arterioles, capillaries, closed circulatory system, open circulatory system, veins, venles

1 - vessels that carry blood away from ehart
2 - small blodo velslsels that edistruibute blood from an aartery to aapilalries
3 - veryu small vessels with very thin walls
4 - one in which blood held in vessels
5- blood not held in vessels
6 - vessels that cary blood back to heart
7 - small blodo velssels that collect blood from capillaris and lead into veins

open circulatory system

many animals, including inscet

blood not always held within blodo vissels - sintead, fluid circulates through body catvity so tissues and cells bathed directly in blood
movements of body helpt o circulate blood so without movement bloods stops moving

in inscets, muscular pumping organ like hart
long muscular tube that lies just under dorsal surface of body
blood from body enters heart through pores called ostia
heart then pumps blodo towards head by peristaliss
at forward end of heart blood simply piurs out uinto body cavity
Circulation can continue when insect is at rest but body movement smay still affect circulation

locst open circulation

larger and morea ctive insects

open ended tubes attached to herat
direct bklood towards active parts of body eg leg and wing muscles

open cirrculatory system:
blodo pressure flow, blood flow slow
circulation may be affected by body movemetns or lack

closed circulatory system

larger animals - blood entirely in vessels
closed circulatory system

separate fluid, tissue fluid bathes tissues and cells
adv:

Higher pressure so blodo flows more quickly
more rapid delievry of oxygen and nutrients
mroe rapid removal of carbon dioxide and other wastses

transport independent of body movements

blood vessels

each adapted to particular role in relation to distance from ehart

all have inner layer or lining made of single layer of cells - endothelium

thin layer particularly smooth to reduce friction with flowing blopod

arteries

carry blood away from ehart

at high pressure so artery wall mnust be thick to withstand pressure

Lumen small to maintain high pressure
inner wall folded to allow lumeen to expand as blod flow increases
wall 3 ylayers:

tunica intima - thin layer of elastic tissue whicha llows wallt o stretch then recoil to help maintain blood pleassure

tunica media - consits of thick layer of smooth muscle
tunica adventitia - relatively thick layer of collagen and elastic tissue
provdies strength to wirhstand high pressure, recoil to maintain prssure

arteries near hart have more ealstic tissue in wall, in order to allwo strethc and recoil, helps to evn out fluctuations in blood pressure created by heart

fruther - walls contain more muscle tissue

arterioles

small - distribute blood from aartery to capillaries
contain layer of smooth muscle, contraction will restric diameter of vessel
this icnreases resistance to flow and reduces rate of b;ood flow

constriction of arteriole wals can be used to divert flow of blood to regions that are demanding more oxygen

cappilaries

very thin walls, allow exchange of materials between blood and tissue fluid

Lumen very narrow 0 diamater same as red blodo cells

red blood ecells may be squeesezd agianst walls of capilarry as they pass alogn
thi shelps transfer ox oxygen, since reduces diffusion path to tuisseus, icnreses resitance and reduces rate of flow


walls consist fo single layer of flattened endothelialc ells
reduces diffusion distance for materials being exchanged

leaky walls - allow blood plasma and dissovled substances to leave blood

venules

from capillaries blood flows int o venules

colelct blood from capilary bed and lead into veins

venule wall consits of thin layuers of muscle and leastic tissue outside endothelium

thin outer layer of collagen

veins

carry blood back to heart
blood at low pressure and walsl dont need to be thick

large lumebnt o ease flow of blood
thiner layers of collagen, smooth muslce and elastic tissue tha nartery walls

no need to stretch and recoil
not actively constricted in order to reduce blood flow

main feature of veins - contain valves to help blood flow back to heart and prevent flowing in opposite direction

as walls thin, vein can be flattened by ation of surroundin skeletal mnuscle

contraction of surrounding skeletal mnuscle appleis rpessure to blood, forcing blodo to mvoe alongin direciton determined by valves

blood, hydrostatic pressure, lymph, oncotic pressure, plasma, tissue fluid

1 - fluid used to transsport materials around body
2 - pressure that fluid exerts when pushign against sides of vessel or container
3 - fluid held in lympahtic system, of tubes that treturns excess tissue fluid to blood system
4 -pressure created by osmotic effects of solutse

% - fluid portion fo blood

6 - fluid surrounding celsl and tissues

blood plasma

plasma contains many blood cells and dissovled substances
oxygen
co2
minerals
glucose
maino acids
hormones
plasma proteins

cells include erythrocytes, leucocytes and platelets

tissue fluid

does not contain plasma portiens

formed by plasma leaking from capilalries

suppleis cells with oxygen and nutrients

s blood plasma leaks from capillary, carries all dissolved substances into tissue fluid

mass flow rather than diffusion

waste produts from cell metabolism wilol be carried back into capillary as some of tissue fluid reurns to caillary

formation of tissue flouid

when artery reaches tissues, branches into smaller arterioles then network of capillaries

eventually link up with venules to carry blood back to veins

Therefore blood flowing into organ or tissue is contained in capilalries

arterial end of capillary - blood relatievely hydrostatic pressure
pressuer tneds to push blood fluid out of capillaries through capillary wall

fluid can leave through tiny gaps between cells in capillary wall


fluid that leaves blood constis ofplasma with dissolved nutrients and oxygen
all red blood celsl, lpaetelts and most white blood celsl remain in blood, and plasma proteins
too alrge to be pushed out thorugh gaps in capillary walL

tissue fluid surroudns body cells so gas and nutrient exchange can occur across plasma membreanes
occurs by diffisuoin, faciliated fdiffuosn and active uptake

tissue fluid returning to blood

blood pressure at venous end of capillary much lower

allows some tissue fludi to return to capillary cacrrying co2 and other waste substances into blood

nto all tissue fluid re enters blodo
some directed into tubular system(lymph or lymphatic)
drains excess tissue fluid out of tissues and retuns toblood system in subclavian vein in chest

lymph

lymphatic system fluid, similar in composition to tisue fluid
Contains more lymphocytes, sicne produced in lymph nodes
swellings found at intervals along lympahtic system, immune response


if tisse infected, capillries become more leaky and more fluid directed to lymph syustem - directs bacteria towards lymph nodes

blood plasma, tissue fluid, lymph features

1 - high hydrostatic pressure, more negative oncotic pressure than tissue fluid
red blood cells, neutrophils, lymphotcites, plasma proteins and fats trasported in lipoproteins

2 - low hydrostatic pressrue, less negative oncotic rpesusre than blood plasma
some neutropphils, especially infected areas - few portiens and fats

3 - low hydrogstatic pressure, less negative oncotic prussure than blodo plasma, contains lymphocytes, few prteins and mroe fats htan tissue fludi espceialyl near digestive system

movement of fludis - hyrostatic pressure

not only infleunce on movement of fluidin and out of capillary
tissue fluid has own hydrostatic pressure, oncotic pressure of solutes also has infleunceh

ydrostatic pressure movement of fluids

blood - tends to push fluid out into tissues
of tissue lfuid - pushes fluid into capilaries

oncotic pressure of blood - pulls water back into blood(negative figure)
oncotic pressure of tissue fluid - pulls water into tissue fluid

net result of forces creates pressure gradient to push fluid oout of capilalry at artieral end and into capillary at enule end

atriovencilar valves, cardiac muscle, semilunar valves

1 - valves between atria and ventircles, ensure blood flowsin correct direction
“ - specialised muscle found in walls of hear tchambers
3 - prevent blood re-entering heart from arteries

mammalian heart

muscular pump, 2 dides

right - pumps deoxygenated blood to lugns to be oxygenated
left - pumps oxygenated blood to rest of body

both sides - heart sequeezes blod, putting it under pressure
forces blood along arteires and throuhg circulatory system

external features of heart

humans - just off centre towards left of chst cavity

main prt - firm, dark-red muscle called ardiac muscle

pumping chambers - ventricles
thin walled chambers - atria, mkuch smaller than ventricles and easy to overlook

lying over sufrace ofh heart - coronary artieries, suppply oxgyenated blood to heart muscle

if become constricted, consequences - reduce delivery of xogyen and nutrients eg fattya cids or glucose

angina or heart attack(myocardial infection)

top of heart - tubular b lood vessels, carry blod into atria nad artier es carry blodo away from ehart

internal features of mamalian heart

atria receive blood from major veins
deoxygenated blood ffrom body through vena cava into right atrium

oxygenated from lungs flows through pulmonary vein into left atrium

From atria, through atriovencular valves into ventricles

attached to valves tendinous cords, prevent valves from turning inside out when ventricle walsl contract

wall(septum) separates ventricles from each ohter

ensures oxygnated blood in left side of heart and deoxygnated inright side kept separate

deoxygenated leaving right ventricle flows into pulmonary artery leading into lungs, oxygenated

oxygnated blood leaving left ventricle flows into aorta
caries blood to number of arteries that supply all parts of body
at base of major arteries, exit heart, semilunar valves
prevent blood returning toh heart as ventricles relax

blood pressure

higher pressure, further push blood
cardiac muscle in wall of each chamber contracts to create presusre


atria - muscle of walls very thin, chamebrs dont need to create much rpessure, function to receive blood from veins and puish into ventricles

right ventricle - walls thicker than atria walls, enables to pump blood out of heart
pumps deoxygenated blood to lungs, inc ehst cavity beside haert
so blood doesnt need to travel very far
alveoli in lungs very delicate and could be damged by very high blood pressure

left ventricle - walsl 2-3x thicker than right blood from here pumped ouit throuhg aorata and needs sufficient pressure to voercome resistance of systemic circulation

cardiac muscle

fibres that branch, producing cross bridges
help spread stimulus around heart

ensure muscle can produce squeezing action rather than simple length reduction

numerous mitochondria between myofibrils to supply energy fro contraction

muscel cells sepearated by intercalated discs, facilitate synchronised contraction

each cell ahs nucleus and divided into contractile units, sarcomeres

cardiac cycle

sequence of veents in one full beat of heart

atrial systole - both right and left atria contact together

musclein walls thin so only small increase in pressure created by contraction which helps pushb blood intro ventricles, strethcing walls and esnuring full of blood

Ventricular systole - both right and left ventricles pump together

Contraction starta t apex(base) of ehart so blood pushed upwards towards arteires

diastole - m uscular walls of all four chambers relax, elastic recoil causes chamebrs to increase in volume alolpwing blood to flow in from veins

atrioventricular valves

after systole, ventricular walls relax and recoil
presure in ventricles rapidly drops below pressure in atria

blood in atria pushes atrioventricular valves open
blood entering hertt flows straight through atria and into ventricles
pressure in atria and ventricles rise slowly as they fill with blood

valves remain open while atriac ontract but close when atria rleax

closure cauesd by swirling ction in blood arond valves when ventricle full

as ventricles begin to contract(systeole), pressure of blood in ventricle rises

presure rises above that in atria, blood starts to move upwards
movement fills valve pockets and keeps them closed
tendinous cords artached to valves prevent them fromturning inside out

Prevents blood flowing back into atria

semilunar valves

befiore ventricular contractionm,pressure in major artieries higher than pressure in ventricles
means emilunar valves closed

ventricular systole raises blood presure in ventricles very quickly
Pnce pressure in ventricles rises above rpessure in major artier,es semilunar valves pushed open

blood under very hgih pressure, forced out of ventricles in poewrful spurt

once finished contracting, heart muscle starts to relax(diastole)

elastic tissue in walsl of ventricles recoils

stretches muscle out agian and returns ventricle to is original size

causes pressure in ventircles to drop quickly

as dorps below pressure in mnaojor artier,s blod starts to flow back towards ventricles

semilunar valves pushed closed by blood collecting in pockets of valves

prevents blood returning to ventricles

presure wave crated when left semilunar vlave closes is pulse we can easily feel at wrist or neck

pressure in blodo vessels changes

blood enters aorta and pulmnonary artery in rapid spurt but tisuses require blod to be delivered in even flow

artery walls close to the hart have a lot of elastic tissue
when blood leaves hart, walsl stretch
blood moves on and out of aorta, aorta pressure starts to drop
elastic recoil of walls helps maintain blood pressure in aorta

further blood flows along artiers, more persure drops and fluctuations become less obvious

important to maintain pressure gradient btween aorta and arterioles, as this keeps blood flowing towards tissues

bradycardia, ectopic haertbat, electrocardiogram, fibrillation, myogenic muscle, purkyne tissue, sinoatrial node, tachycardia

1 - slow ehart rythm
2 - extra beat or early beat of ventricles
3 - trace that recorsd electrical activity of herat
4 - uncoordinated contrction of atria and ventricles

5 - muscle that can initiate its own contractoin
6 - consists of specially adapted muscle fibres that conduct wave of excitaiton from AVN down the septum to ventricles
7 - heart pacemaker - small patch of tissue, sends out waves of electrical excitation at regular intervals to intiate contactions

8 - rapid hearth rhythm

need for coordination

heart/cardiac muscle unusual
can initiate own contraction
becaus eof proerty, msucel mygenic
will contract and relax rhytmically even if not cnnected to body

muscles from atria and ventrricles each have natural frequency of conta2ction
atrial msucle tensd to contract at higher frequency than ventricular muscle
property could cause inefficient pumping if contractions of champers not synchronised - fibrillation

needs mechanisms - can coordinate contactions of all 4 chambers

initiation and control of heartbeat

top of right atrum, near point where vena cava empties blood into atrium, SAN
small patch of tissue - generates electrical activity
initiates wave of exciation at regular intervals

55-80 times per minute, apcemaker

contraction of ventricles

after short delay, wave of excitaiton carried away from AVN and down specialised conducting (purkyne tissue)

Runs odwn interventricular septuem
at base, ewave of exciation speads out over alwlas of ventricles

as spreads upwards from apex of ventricels, causes muscles to contract
means ventricles contract from base upwards

pushes blood up towards major artereis at top of heart

electrocardiograms

can monitor electrical acvitiy at heart
involves attaching sensors to skin
some electrical activity gnerated spreads through tissues next o heart and outwards to skin

sensors on skin pick up eexcitation created by heart and convert into trace

trace nelectrocardiogram

particular shape
P - exciattion of atria
QRS - exciatoin of ventricles
T - diastole

shape of ecg trace can indicate when pat of heart msucle not healthy, used to diagnose hartp roblems

affinity, dissasociation, fetal haemoglobin, haemoglobin

1 - strong attraction
2 - relasing oxygen from oxyhaemoglobin
3 - type usually only found in fetus
$ - red pigment used to transport oxygen in blood

hamoglobin

oxygen transproted in erythrocytes
contain protein haemoglobin, becoms oxyghameoglobin


hameolglobin complex rpotein with 4 subunits
each subunit - polypeptide chain and haem(non protein) group
haem group - single iron ion in form of Fe
can attract and hold oxygen molecule
high affinity for oxygen

each hame group can hold 1 oxygen, each haemgolobin molceules 4 oxygen molecules
280m in each red blood cell
so red blood cell can carry over 1b molecuels


association - lungs where pO2 high
dssiascocation - titssues where pO2 low

transport of oxygen

absorbed into blood as pass4es alveoli in lungs
molecuesl diffusing into blood plasma enter red blod cells
here become associated with haemoglobin

oxygen binsd reversibly to haemoglobin
takes oxygen molecuesl otu of solutoin and maintains steep concetrnation grdient, allwoing more oxygen to ener blood from lungs and fifuse intoc ells

blood carries oxgygen from lungs back to heart, before travelling around body to supply tissues

tisseues - cells need oxygen for aerobic respiration

so oxyhaemoglobin must be able to relaese oxgyebh, dissacosiation

haemoglobin and oxygen transport

ability of haemoglobin to associate with and relase oxygen depensd on concentration of o2 in surrounding tissues

concetnraiton measured by relative pressure that it contribuest to mixture of gasse-s partial pressure of oxgygen or pO2
oxygen tension, kPA

normal liqiuid - convcetntation of oxygen absorbed into luciid rriectly proportional to oxgyen tension in air surruodning

not case with haemoglobin, can oassociated with oxygen that produes S shape curve

haemoglobin dissociation curve

low oxygen tension, haemoglobin doesnt readily asociate with o2 molecules

becaues haem groups that atract oxygen in centre
mekasz diffuclt for o2 molecule to reach haem and associate

diffuclt in combining first o2 molecule accounts for low saturation level at low oxygen tionson

what happens when oxygen tension rises

diffusion gradient into haemoglobin molecule increaes
eventually one o2 molecule enters haemoglobin molecule and assoicates with one of haem groups
causes slight change in shape of haemoglobin molecule(conformatioational change)

allows more oxygen molecules to enter haemoglobin molecule, associate with other haem groups|
accounts for steepness of curve as oxygen tension rises

as approaches 100% satruation, curve levels off, cretint S shaped curve

mammalian haemogblob well adpated to tarnsporting oxygen to tissues

oxygen tionson in lungs sufficient to produce sloe to 100% saturation
o2 tension in respiring tissues sufficiently low to cause oxygen to doissoaciate readily from oxyhaemoglibin

fetal haemoglobin

higher affinity for o2 than adult
so dissaociaton curve for fetal is to the left of adult curve
fetal must be able to asoiace tiwh ow in environment where o2 tension low enough to make adult haemoglobin release o2

in placent,a o2 tension low, fetal will abosrb oxygenf rom surrounding fluid
reduces o2 tension even further

so oxygen diffuses from mothers blood fluid into placenta
reduces oxugen tension within mothersblod wich makes maternal haemoglobin release more o2(dissasociation)

carbonic anhydrase, chloride shift, bohr effect, haemoglobinic acid

enzyme that catalyses combination of carbon dioxide and water
movemento f chloride ions into erythrocytes ot balance cahrge as hydrocarbonate ions leave cell

3 -effect that extra co2 has on haemoglobin, explaining relaes of more oxygen
4 - compounf roemd by buffering ction of haemoglobin as it comnbuines with excess hydrogen ions

the role of haemoglobin

co2 released from respiring itssues

must be removed and transported by blood to lunsg for extrection

3 ways: 5% in plasma direclttyy
10% combined directly with haemogliobin to form carbaminohaemoglobin
85% in form of hydrogencarbonate ions(HCO3-)

formation of hydrogencarbonate ions

co2 in blodo pslamsa diffues into red blodo cells
combines with water to form weak acid called carbonic acid

catalsyed by enzynme carbonic anhydrase
CO2 + H2O —> H2CO3
dissasociates to reales H+ ions and hydrogencarbonate ions

H2CO3 → HcO3- + H+

hydrogencarbonate ions diffuse out of red blood cell into plasma
charge inside red blood cell mkainted by movement of Cl- ions from plasma into redb lood cell

hdyrgon ion sbuilding up in cell could cause contects to become very acidic, so h2 ions taken out by assoicating with haemoglobin to produce haemoglobinic acid(HHb) - haemoglobin acting as buffer

effects of increastion co2 concetrntation

blood entering repsiritng tissues carries o2 as oxyhameoglobin
partial pressure of 2o in repsiring tissues lwower than that in lugns

SINCE OXYGEN USED IN RESPIRATION

SO OXYHAEMOGLOBIN BEGINS TO dissasociate and eleases oxygen tot issues

haemoglobin available to take up hydrogen ions, farmong haemoglobinic acid

where tissues active there is more carbon dioxid released
Dramatic effect on haemoglobin

bohr effecgt

co2 etnters red blood cells froming carbonic acid, dissacoiates to relaes h+ ions
h+ ion safefct ph of cytpolasm, making it more acidic

with any protein, changs in pH can affect tertiary strucutr eof haemoglobin
reduces affinity of haemoglobin for oxygen
unable to hold as much oxygen, o2 releasd from oxyhaemoglobin to tisseus
where rtissues repsiring more, cmore co2

so more h+ ions in red blood cells, mkaking oxyhaemoglobin release more oxygen


so more co2 present, haemoglobin less satureatd with oxygen
rfelcting in dissociation curve, xownars and to right - borh shift, reasutls i mor eoxygen being released - just what muscles need for aerobic respiration to continue

dicotyledonous plants, meristem, phloem, vascular tissue, xylem

1 - plants with 2 seeds leaves and branching pattern of veins the leaf

2 - layer of dividing cells, ehre its claled pericycle

3 - tranports dissovled asimilates

4 - consists of cells specialiesd for transporting fluids by mass flow

5 -transports water nad minerals

need for trransport system in plants

larger plants small SA:V ratio

so neeed specialiesd exhcnage surface antd trapostt system

plant respoiration rate low - so demenad for oxygen lwo, met by diffusion

demand for water and sugars still high - gcnanot oabsorb sugars from coil, only water and minerals

lmove water and mireals up to leaves, sugards from leaves to rest opf plant

vascular tissues

transport system in plants consist of specialised vascular tissue

water and soluble mineral ions travel upwards in xylem tissue

assimilates eg sugards travel up or down in phloem tissue
both xylema nd phloem highly specialiesd to carry out transport fucntion|

but unlike in animals, no pump
respiratory gases not carried by tissues

distribution of vascular tissue

dicotyledonous plants those have 2 seed leaves

also very characteristc distribution of vascular tisseu
tistributed throuhgout plant

xylem and phloem found together in vascular bundles

bundles contain other tissue sometimss eg collenchyma and scelerenchyma that give bundle strength and help support plant

xylem and phloem in young root

vascular bundle found at centre of young root

central core of xylem in shape of X

phloem found inbetween arms of x shaped xylem tissue

provides strnegth to withstand puling focrse to which roots exposed

around vascular bundle - special sheath of cells , endodermis

key role n getting water into xylem vessels

inside indederis layer of mersitem cells(pericycle)

xylebm and phloem in steam

vascular bundles near out eredge of stem
non woody plants - bundles separate and discrete

woody - bundles separate in young stems, but continuous ring in older stems
compelte ring of vascular tissue just under tree bark
provides strength and felxiibility to withstand bending forces


xylem found towars inside of each vascular bundle and phloem towards outsied

inbetween xylem and phloem cambium

meristem cellst hat divide to produce new xylem and phloem

xylem and phloem in leaf

vascular bundles form midrib and veins of leavf

dicotylededonus l,eaf - breahing network ov veins that ge smaller as they spread awya from midrib

within each vein, xylem located ontop of phloem

best plants to dissect and stain to view vascualr tissue - cellery and busy lizzies

companion cells, sieve tube elemnts,, xylem vessels

1 - cells that help load sucrose into sieve tuibes
2 - make uip tubes in phloem tissue that carry sap up and down plant, separated by sieve platse

3 - tubes which carry water up the planjt

structure and function of xylem

tissue used to tarnsport water and minerail ions from roots up to leaves and other parts of plant
consits ofo:

vessels to carry water and idssolved mineral ions
fibnres to help support plant

living parenchyma cells,a ct as packign tissues to separte fd suppot vessels

xylem vessels

as develop, lignin imprevnates walls of cells, makign wals waterporoof
kills cells
end walls and contenst of cells decay

leaing long columndf dead cells with no contents - xylem vessels

lignin strenthens vesel alls and prevents from colapsing

keeps open even when water in short supply

lignin thickening forms ptters in cell wall

sprial, annulr(rings) or reticulate(network of broken ringsz0

prevens vessel from being too rigid and allows some flexibility ost tsem or branch

osme places lignification not cpmlete, leving gaps in cell wall

gaps form pits/bordered pits
they in two adjcent vessels aligned to allow ater to leav one and pssii nto next, allowa water gto leave xylem and pass into living parts of plnt

adaptations of xylem to function

can carry wazter and mineral ions from roots to very top -of plant


madefrom dead cells aligned end to end to form continuos column

tubes narrow so water column doesnt break esily and capillary action can be effective

boredred pits in lignified wall to alow water to move sideways frmi one vessel ot another

Lignin deposited in walls in psiral, annular or reticuoate patterns allwos xylem to stretch as plant gros
enables stem of brach to bend

why flow oofw ater not inpeded in xylem

no cross walls
no cell contents, nucelus or cytpolasm
lignin thickening roprventes walls from collapsing

structure and function of phloem

tissue, consits of cells that perform function of transporting sucrose

main cell types siveve tube lements and companion cells

Phloem tissue used to transport assimialtes(sucrose and amino acids) around plant

sucrose dissolved in water to form sap

Phloem tissue constsi fo sieve tubes - made of sieve tube elemst and companion cells

sieve tube elemts

elongated sieve tube elemtsn lined up ende to end to form sieve tubes
no nucles very littl cytoplasm

Leavins pace for mas flow of sap to occur

ends of sieve tube elmetns perforated clos walsl(sieve plates)

perforations i n sieve plate allwoe movement of sap from one elemtn to next

sieve tubes have very thin walls and when seen in transevrse setion usualyl 5 or 6 sided

first sight - sieve plats appear to have no rewal function and actualyl obstuct feew flow of sap in sieve tube
may act to support tube- keeping lumen open
more imporantl, mechanism to block sieve tuibe after injury or infection

pores in sieve plate rapidly become blocked by deposition of callose(compex carbohydrate) - prevnts loss of sap and inhibits tranpost of pathogens around plant