circulation lecturer

8/9/2019 Circulation Lecturer.

1/38

Circulation

1. CIRCULATION IN ANIMALS Every organism must exchange materials with

its environment

This exchange ultimately occurs at the cellular

level

In unicellular organisms, these exchanges occur

directly with the environment

Simple diffusion adequate for exchange ofmaterials between cell and external environment

Diffusion alone is not adequate for internal

transport of material for animals with many cell

layers/multicellular organisms

A specialized circulatory system is required

which interacts with every organ system in the

body

1.1 Types of circulatory system1.1.1 Invertebrate circulatory system The wide range of invertebrate body size and

form is paralleled by a great diversity in

circulatory systems

Most invertebrate have a gastrovascular cavity

or a circulatory system for internal transport

HMM/SCM 1424.,CFS,IIUM

1


2/38


3/38

Circulation

Open circulatory system: (Refer Figure. 42.2,pg. 869)

Vessels have open ends

No distinction between blood and interstitial

fluid, both are referred as body fluid =

hemolymph.

In insects and other arthropods, the heart = an

elongated dorsal tube.

Heart contracts: hemolymph pumps intointerconnected sinuses surrounding the

organs allowing exchange between

hemolymph and body cells

Heart relaxes: hemolymph draws into the

circulatory system through pores/ ostia.

Body movements that squeeze the sinuses

help circulate the hemolymph.

Insects: hemolymph mainly distributesnutrients & hormones. Gases/oxygen is piped

directly to cells by the tracheal system

Mollusks & arthropods: hemolymphpigment = hemocyanin(contains blue colouredcopper which binds to oxygen)

Q : W h a t a re so m e a d va n ta g e s o f o p e nc i rcu la to ry sys tem ? Lower hydrostatic pressure less energy

expenditure


3


4/38

Circulation

Lack of extensive system of blood vesselless

energy required to build and maintain

Closed circulatory system (Refer Figure 42.3,pg. 869)

Annelids, cephalopods, echinoderms & all

vertebrates

Blood confined to vessels

Blood distinct from interstitial fluid

Heart pumps blood into large vessels that branch

into smaller vessels

Q: S ta te the ad vantages o f c lose c i rcu la to rys y s t e m .


Heart

Hemolymph insinusessurrounding ograns

Anterior

vessel

Tubularheart

Lateral

vessels

Ostia

(a) An open circulatorysystem

Figure 42.3a

4


5/38

Circulation

Higher blood pressuremore effective at

transporting fluids to meet the high metabolic

demands of the tissue and cells of larger and

more active animals.

Earthworms:

3 major vessel branch into smaller vessels thatsupply blood to various organ.

The dorsal vessel: The main heart, pumping

blood forward by peristalsis.

anterior: five pairs of vessels loop around the

digestive tract. Function = auxiliary hearts,

propelling blood ventrally

Blood contains hemoglobin dissolved in plasma

(in vertebrates hemoglobin red blood cells)


Figure 42.342.3b

Interstitialfluid

Hear

t

Small branch vesselsin each organ

Dorsalvessel(main heart)

Ventralvessels

Auxiliaryhearts

(b) A closed circulatorysystem

5


6/38

Circulation

1.1.2. Vertebrate Circulation/Cardiovascularsystem

The closed circulatory system of human and

other vertebrates is often called the

cardiovascular system.

Components:

(1) Heart

(2) blood vessels

(3) blood

1.1.2 Functions of vertebrate circulatorysystem

Q : L is t o u t th e fu n c t io n o f ve r te b ra tec i rcu la tory system

(1) Transport nutrients, oxygen, waste,

hormones

(2) Helps maintain fluid balance

(3) Defends body against invading

microorganisms

(4) Helps distribute metabolic heat within

body/maintain constant body temperature

for endotherms

(5) Helps maintain appropriate pH


6


7/38

Circulation

1.2. Blood Vessel (Refe r F igu re . 42 .9 , pg .8 7 5 )

1.2.1 Characteristics and functions of bloodvessels

Structural differences of arteries, vein andcapillary correlate with their differentfunctions.

Wall of arteries & veins have 3 similar

layers:Outside: Connective tissue with elasticfibers & collagen allow the vessel tostretch and recoil.Middle: Smooth muscle & more elastic

fibers


7


8/38

Circulation

Inner layer/lining lumen: Endothelium/single layer flattened cells thatminimize resistance to blood flow.

Q : A r te r ie s h a ve th ic k e r m i d d le a n d o u te rl aye rs than ve ins .W hy?

T o a c c o m m o d a t e t h e h i g h p r e s s u re o f b l o o dp u m p e d f ro m t h e h e a r t.The i r e l as t ic i t y he lps m a in ta in b loodpressure even w hen the hear t re laxes .

In the thinner-walled veins, blood flowsback to the heart mainly as a result ofskeletal muscle action.Within larger vein, flaps of tissues act asone way valves that allow blood to flowonly toward the heart. (Re fe r F igu re 42 .10pg . 875 )

Capillaries: Has only endothelium &basement membrane, thus enhancingexchange.


8


9/38

Circulation

1.2.2. Comparison of blood vesselsQ : F il l in t he ta b le t o sh o w th e d if fe re n c e

betw ee n the b lood vesse l s .

Artery Capillaries VeinSmoothmuscle

Thick None Thin

Elastictissue

Abundant None Little

Lumen Small Large Large Bloodpressure

High Low Low

Valves In aorta andpulmonary

artery only

None Semilunar

valves/Ven

ous valves

Function Transportblood away

from heart

Exchange

of material

between

blood and

extra

cellular

fluid

Transport

blood back

to the

heart


9


10/38

Circulation

Q : O bs erv ed th e in te rre la tio ns hip o f b lo odf lo w v e lo c i ty , t o ta l c r o s s s e c t io n a l a r e ao f b lo o d v e s se ls , a n d b lo o d p r es s u re inF igu re 42 .11 pg . 876

Blood flow highest in aorta (force from

contraction of ventricle), decreases significantly

in arterioles, lowest in capillaries due to

increase in total cross-sectional area. Blood

velocity begins to increase in veins due to


10


11/38

Circulation

reduction in cross sectional area and

contractionof skeletal muscles squeezing the

veins

Blood pressure highest in aorta, arteries,

decreases as it passes through arterioles,&

capillaries due to peripheral resistance , lowest

in veins (pressure by pumping of heart has

dissipated, contraction of skeletal muscles

squeezing the veins help to create pressure for

blood flow in veins)

Enormous number of capillaries, small diameter

of capillaries makes capillaries have the

greatest cross sectional area than any other

vessel.

1.3 Heart1 . F ig ure 1 w i ll he lp y ou r ev ie w t he f lo w o f

b lo o d t hr ou g h a m a m m a l ia n c ir cu la to rys y st e m . L a b e l t h e in d ic a te d p a rt ,c o lo rth e o x yg e n -r ic h b lo o d c e l l an d th e nt ra c e t h e f lo w o f b l o o d b y n u m b e r in g t h ec ir cle s f r om 1 - 1 1 . S t ar t w ith n u m b er 1in the r ight ven t r ic le .


11


12/38

Circulation

Figure 42.5The mammalian cardiovascular

system : an overview

2 Id e n t i fy th e la b e le d s t ru c tu re s in th isd i a g ra m o f a h u m a n h e a r t.

Figure 42.6 The mammalian heart: a closer look


12


13/38

Circulation

1.3.1 Mechanism of heart electricalexcitat ion and contract ion of theheart (Refer Figure 42.8 pg. 874)

Some cardiac muscle cells = self-excitable.

Can contract without any signal from the

nervous system.

The sinoatrial (SA) node, located in the wall of

the right atrium or pacemaker sets the rate and

timing at which all cardiac muscle cells

contract.

Q : D is tin gu is h be tw e e n a m yo ge nic h e artand neurogen ic hear t

Vertebrate heart = myogenic heart(Pacemaker

made up of specialized tissues located withinthe heart itself)

Most arthropod = neurogenic heart(Pacemaker

originate in motor nerves arising from the

outside)

The SA nodes generates electrical impulses that

spread across both atria simultaneously, via the

gap junctions in the intercalated discs between

cells

The AV (atrioventricular) node, located in the

lower right atrium, acts as a delay and relay

node


13


14/38

Circulation

After a slight delay, transmission continues into

the atrioventricular (AV) bundle

The AV bundle splits, sending branches upward

over both ventricles (Purkinje fibers) resulting in

ventricular contraction

Q : S ta te a nd e x p la in th e fac to rs th a ti n f luenced the pac e o f SA nodes .

The pacemaker is influenced by two set of

nerves with antagonistic signals, hormones,

body temperature, and exercise.

Symphatetic nerve speeds up the SA nodes

Parasympathetic/vagus nerve - slow it down

Hormones Ex. Epinephrine heart rate

Temperature SA nodes. An increase of only 1C

raises the heart rate by about 10 beats perminute

Exercise heart rate

Electrocardiogram (ECG or EKG) Spread of electrical activity through heart

creates currents that can be recorded from

surface of body using electrodes placed on limbs

and chest

Recording = an electrocardiogram

Depolarization contraction of the heart

chambers


14


15/38

Circulation

Repolarization relaxation of the heart

chambers

First peak P = depolarization of the atria

The second larger peak, QRS= ventricular

depolarization Last peak T= ventricular repolarisation

Sometimes a fourth peak is observed; U =

ventricular diastole


15


16/38

Circulation

1.3.2 The cardiac cycle (Refer Figure. 42.7,pg. 873)

The heart contracts and relaxes in a rhythmic

cycle called the cardiac cycle

Systole: The contraction, or pumping, phase of

the cycle

Diastole: The relaxation, or filling, phase of the

cycle

For a human at rest with a pulse (heart rate) of

about 75 beats per minute, one complete cycle

takes about 0.8 sec.

Consisting of atrial systole and ventricular

diastole followed by atrial diastole and

ventricular systole


16


17/38

Circulation

1: During the relaxation phase (atria and

ventricles in diastole) lasting about 0.4 sec,

blood returning from the large veins flows into

atria and ventricles.

2: A brief period (about 0.1 sec) of atrial systole

forces all the remaining blood out of the atria

and into the ventricles.

3: During the remaining 0.3 sec of the cycle,

ventricular systole pumps blood into the large

arteries.

Q : E x p la in w h a t c a u se s th e f i rs t a n dseconds hear t sound .

The lub heart sounds caused by the closing of

the AV valves and mark the beginning of

ventricular systole, then dup sound marks the

closing of the semilunar valves and the beginning

of ventricular diastole


17


18/38

Circulation

Q : D e f in e h e a rt m urm ur a n d e xp la in i tsc a u s e .

A heart murmur is the detectable hissing sound

of blood leaking back through a defective valve/

by valves that do not close properly

Cardiac output(CO):

the volume of blood that the left ventriclepumped into the systemic circulation per minute

CO = Stroke volume x heart rate/min

Stroke volume =volume of blood one ventricle

pumps during one beat/in each contraction

Average stroke volume in human 75 ml

Q : C a lc ula te th e c ard ia c o utp ut in re st in ga d u lt w he re th e s t ro k e vo lu m e is 7 0m l/s t ro k e a n d th e he a rt ra te is 7 5s t roke /m in .

Resting adult = 70ml/stroke x 75 strokes/min

=5250 ml/min (5.25L/min)

Stress/Heavy exercise , CO = 20 to 30 L/min

Blood pressure Force /hydrostatic pressure exerted by blood

against inner wall of blood vessels


18


19/38

Circulation

= blood flow x peripheral resistance

CO, blood flow , BP CO, blood flow , BP Blood volume (hemorrhage/chronic bleeding),

blood flow , BP Constriction of blood vessels (vasoconstriction)

reduce the diameter of vessel, friction between

blood and blood vessel , BP. Dilation of blood vessels (Vasodilation), friction

between blood and blood vessel , BP. BP reading = systolic pressure

--------------------------------

diastolic pressure

Q : D ef in e sys to lic p re ssu re a nd d ia sto licp ressure .

Systolic pressure = the pressure in the arteriesduring ventricular systole. The highest pressure

in the arteries

Diastolic pressure = the pressure in the arteries

during diastole

Can be measured using sphygmomanometer.

(Refer Figure 42.12, pg. 877)

Normal BP = 120/80

1.3.3 Control of the heart (Refer Figure42.12, pg. 820 Solomon)


19


20/38

Circulation

Heart rate is regulated by both nervous and

endocrine system.

Baroreceptors: receptors sensitive to changes

in blood pressure located at the arch of aorta

and carotid arteries.

Baroreceptors activate neurons, relay

information to cardiovascular control center

(CCC) in medulla oblongata.

Negative Feedback mechanism to restorehomeostasis. Blood pressure falls:

CCCsympathethic nerves (autonomic)

norepinephrine heart rate& strength of

contraction neuronsblood vessels of skin and viscera(internal organs)vasconstriction/constrictionof arterioles

Blood pressure high:

CCCparasympathetic

nervesacetylcholineheart rate& strength

of contraction

neuronsblood vessels of skin and viscera

(internal organs)vasodilation/dilation of

arterioles


20


21/38

Circulation

1.4 The Cardiovascular Disease (Refer pg.883)

Are disorders of the heart and the blood

vessels

Atherosclerosis: (Refer Figure 42.18, pg. 883) Definition: Accumulation of fatty material,

smooth muscle, cholesterol deposits, fibrin

deposits & cellular debris within walls of

arteries

Effect: lumen of artery to reduce/narrow/Blood

flow reduced

Factors that promote: genetic factors, smoking,

hypertension, high blood cholesterol levels

Prevention: diet low in cholesterol/fat, reducehypertension, stop smoking, regular exercise,

high fibre diet.


21


22/38

Circulation

Arteriosclerosis Definition: hardening of arteries/ thickening &

loss of elasticity to wall of arteries Cause: calcium deposition within arterial walls/

(severe atherosclerosis)

Effect: reduce blood flow/heart has to work

harder to pump blood.

Factors that promote: genetic factors, smoking,

hypertension, high blood cholestrol levels

Prevention: diet low in cholestrol/fat, reduce

hypertension, stop smoking, regular exercise,

high fiber diet

Hypertension (High blood pressure) 120-139/80-89 = Prehypertensive always > 140/90 = Hypertension Promotes atherosclerosis and increases the risk

of heart attack and stroke

Causes of hypertension: heredity, aging,

smoking, high salt intake, stress

Prevention: regular exercise, reduce salt intake,

stop smoking, limit alcohol, heart healthy diet,

reduce stress.

Q : B r ie f ly e x p la in th e d iso rd e r k n o w n a shypotens ion .

Refer to abnormally low blood pressure

Relative term because the blood pressure normally

varies greatly with activity, age and medication.


22


23/38

Circulation

Q : D is t in g u ish b e tw e e n a m yo c a rd ia li n fa rc t i on and a s t roke .

M yo card ia l i n fa rc t ionThe term myocardial infarction is derived from

myocardium (the heart muscle) and infarction

(tissue death due to oxygen starvation

Commomly known as heart attack

The death of cardiac muscle tissue resulting

from blockage of one or more coronary arteries.

St rokeThe death of nervous tissue in the brain, usually

resulting from rupture or blockage of arteries in

the head

The effects of a stroke and the individualschance depend on the extent and location of the

damaged brain tissue.

Angina pectoris Condition where a person feel occasional chest

pain

Due to partially blocked of coronary artery

A signal that part of the heart is not receiving

enough blood especially when the heart is

laboring because of physical or emotional stress.


23
http://en.wikipedia.org/wiki/Myocardiumhttp://en.wikipedia.org/wiki/Infarctionhttp://en.wikipedia.org/wiki/Myocardiumhttp://en.wikipedia.org/wiki/Infarction


24/38

Circulation

1.5 The Lymphatic System1.5.1 Components and function

The lymphatic system consists of lymphatic

vessels and lymph tissue (Refer Figure 43.5, pg.

901)

Lymph tissue: Composed of connective tissue

with many lymphocytes

Lymph nodes and nodules: Small masses of

lymph tissue. Lymph nodes function to filter the

lymph and attack viruses and bacteria.

Larger organ :The spleen, tonsils, and thymus

Tonsils: Masses of lymph tissue in the

pharyngeal region that filter out pathogens

Lymph vessels conduct lymph, derived frominterstitial fluid

Lymph capillaries are one-way vessels, which

join and merge to form larger lymphatics (lymph

veins)

Lymph vessels ultimately empty into the

subclavian veins via the larger thoracic duct and

the right lymphatic duct

Q : S ta te h o w th e ly m ph is m ove d in o n ed i rec t ion i n mam m als .


24


25/38

Circulation

Lymph is moved in mammals by differences in

pressure, pulsation of vessel walls, and

contraction of skeletal muscles

Lymph vessels have valves to prevent back flow

of fluid towards capillaries

The lymphatic system plays an important role in

fluid homeostasis

Functions of lymphatic system: return of interstitial fluid to the circulatory

system

immunity

absorption of lipids from the gastrointestinal

tract

1.5.2 The interrelationship between the lymphaticsystem and the circulatory system.

Fluid movement between blood and interstitial

fluid. (Refer Figure 42.14 pg. 870 and Figure

42.20, pg. 827 Solomon)


25


26/38

Circulation

Arterial end

of capillary

Blood

pressure

(+40)

Osmotic

pressure

of plasma

(- 28)

At arterial end of capillary, (high)

blood pressure (+40) forces plasma out of

capillary (into interstitial fluid)

Osmotic pressure of blood similar

at arterial & venular ends. Created by thepresence of nonfilterable plasma proteins

Some fluid reenters blood at

venular end due to osmotic pressure of plasma

greater than blood pressure at venular end

Most of interstitial fluid enter

lymph capillarieslymph


26


27/38

Circulation

Q : F il l in t he t ab le t o s ho w t he c o m p ar is onb etw e e n th e b lo od c irc u la to ry s ys te mand the l ympha t ic sys tem

Blood Cir. Syst. Lymphatic Syst.Type of

system

Closed Syst Closed Syst.

Pump Heart None Pressure

Depends on heart

pumping action for

arteries, depends

on external

pressures in veins.

Different pressure

in differentvessels

Depends on

external

pressures.

Generally low

pressure

Valvesinvessels

In vessel leading

towards heart,

(veins), pulmonary

artery, & aorta

In most vessels

Fluid invessels

Blood Lymph

Function

Transport of

nutrients, gas,

waste, for defend

Transport of fat,

filter foreign

particles,

lymphocytes

destroy foreign

bodies.


27


28/38


29/38

Circulation

Three available routes for lateral transport :

(Refer Figure 36.8(b) pg. 743)

1. Transmembrane route : repeated crossings of

plasma membranes /cell wall, solutes exit one

cell, enter next

2. Symplastic route : pathway within the

continuum of cytosol, require minimum of one

crossing of plasma membrane, move from cell

to cell via plasmodesmata

3. Apoplastic route : pathway consisting of cell

wall and extracellular spaces without entering

protoplast/no crossing of plasma membrane


29


30/38

Circulation

Presence of Casparian Strip within endodermis

ensures that no minerals reach vascular tissue

without crossing a selectively permeable plasma

membrane.

Those that are not already within the

symplastic route will be excluded from the


30

Endodermis

Only minerals already

in simplast or entering

pathway by crossing

plasma membrane of

an endodermal cell

can pass into xylem

VascularcylinderXylem

Water from soil

Root epidermis

Soil solution (water +

minerals) absorbed by root

hair surface

Cortex

Apoplastic/extracellular

route(cell wall &

intercellular space)

Symplastic route(cytoplasmic

continuum with

plasmodesmata)

A belt/layer of waxy

material within

endodermal cell wall-

CASPARIAN STRIP

Passage of water

and minerals

through apoplast is

blocked

Regions


31/38

Circulation

vascular tissueselective/preferential transportof minerals from soil to xylem

Long distance transport : Bulk flow transport : Movement of fluid

driven by pressure (high to low)

Phloem: loading of sugar createspositive pressure at one end forcing sap to move

to other end

Xylem: tension/negative pressure at

leaves (transpirational pull) creates tension

pulling water from root (high pressure) to top

(low pressure)


31


32/38

Circulation

1.6.1 Xylem and ascend of sap

Xylem sap flows upward to veins that branch

throughout each leaf, providing each with water.

Rises against gravity to reach heights of more

than 100 m in the tallest trees.

Pushing xylem sap: Root pressure

At night: transpiration~0, minerals

constantly pumped into cells by active transport

s (solute potential) root alwayshigher than soil

(water potential) root always lowerthan soil

water always diffuse into rootroothair always turgid

Root cells continue pumping mineral

ions into the xylem of the vascular cylinder,

lowering the water potential

Water flows in from the root cortex

generating a positive pressure called root

pressureforces fluid up the xylem.

Guttation (water droplets at tips of

leaf/grass)- when more water enter leaves than

are transpired (at night & dawn)


32


33/38

Circulation

Root pressure-is actually a minor

mechanism to force water up. At most able to

push only a few metres up.

After sunrise it is the transpirational pull that

provides the major force that causes upward

flow of water and minerals in xylem

Pulling Xylem Sap :

Transpiration-Cohesion tension

mechanism( Refer Figure 36.12 pg. 747)

90% of water absorbed by root is lost

through transpiration

Transpiration- pull creates -ve pressure/ -ve

water potential at surface of leaves/ top of plant)

Cohesion and adhesion of water (hydrogen

bonding) transmits upward pull along the entirelength of xylem to roots. Producing a continuous

column of water

Water vapor diffuse from air space to

atmosphere through stomata


33

Negative

pressure at air-

water interface

Mesophyll cells

Xylem

Direction of

water flow

Root ( high water

potential)


34/38


35/38

Circulation

1 .6 .2 . P hlo em an d T ra ns lo ca tio n

Translocation of organic

nutrients occur within sieve tubes of phloem

Sieve plates allow sap to flow

along sieve tube

Phloem sap-primarily sucrose,

other solutes: minerals, amino acids, hormones

Direction that phloem sap

travel can vary, always from a sugar source to a

sugar sink.

Q: Define sugar source and sugar sink.

Sugar source: plant organ that

is a net producer of sugar (photosynthesis or

starch breakdown) e.g. leaves

Sugar sink: organ that is a net

consumer or store of sugar, e.g. growing roots,

buds, stems, fruits Storage organs(may be eithera source or a sink depending on the season)

Mass Flow/Pressure Flow Hypothesis:The mechanism of translocation inangiosperms


35


36/38

Circulation

Phloem loading: Sucrose manufactured in

mesophyll cells either can travel to sieve tube

member via symplast or by active transport via

aploplast (Refer Figure 36.17 a and b, pg. 752)

Active transport :using the proton pump and

cotransport of sucrose and H+ mechanism

Loading of sugar/sucrose into sieve tube

reduces water potential of the sieve tube.

Water enters sieve tube from xylem by osmosis

sieve tube take up water by osmosis (from

xylem)

Positive pressure/hydrostatic pressure

generated

Phloem sap flows along phloem from region of

high pressure to lower pressure (sink)

Unloading of sugar (passive) occurs at sink

followed by water. (hence sink always lowerpressure compared to source)

Unloaded sugar used for respiration/growth

metabolism/converted into insoluble starch at

sink

Some water from phloem at sink diffuses back

to xylem and is recycled back to source. (Refer

Figure 36.18 pg. 753)


36


37/38

Circulation

Loading of sucrose into floem

Pressure flows in a sieve tube


37


38/38

circulation lecturer

Documents