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CHAPTER 8 : TRANSPORT SYSTEM

SUBTOPIC : 8.1 Mammalian heart and its regulation

LEARNING OUTCOME :

a) Explain the initiation of heart beat

b) Explain cardiac cycle

c) Explain ECG emphasizing on P wave, QRS complex and T wave

d) Explain the factors affecting heart beat: pH and temperature

MAIN IDEAS / KEY

POINT EXPLANATION NOTES

a) Initiation of heart

beat

Structure of heart

The internal cavity of the heart is divided into 4 chambers:

Right atrium:

Receives deoxygenated blood from the whole body through

vena cava

Left atrium:

Receives oxygenated blood from the lungs through pulmonary

veins

Right ventricles:

Pumps out deoxygenated blood to the lungs through pulmonary

arteries for gaseous exchange

Left ventricles:

Pumps out oxygenated blood to the whole body through aorta

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MAIN IDEAS / KEY

POINT EXPLANATION NOTES

Initiation of heart beat

● Impulses from the pacemaker or Sinoatrial (SA) node first spread rapidly through the walls of the atria, causing both

atria to contract in unison.

● During atrial contraction, the impulses originating at the SA node reach atrioventricular (AV) node.

● Here the impulses are delayed for about 0.1 second before spreading to the heart apex.

● This delay allows the atria to empty blood completely before the ventricles contract.

● Then the signals from the AV node are conducted to the heart apex and throughout the ventricular walls by bundle branches

and Purkinje fibers.

● Stimulates the ventricles to contract from the apex towards atria driving blood into the aorta & pulmonary arteries.

b) Cardiac Cycle

Definition

• The sequence of events of heart beat involve the alternating and continuing contractions and relaxations of the heart/

cardiac muscle.

• About 0.8 seconds.

Phases

● Systole: contraction phase→ it pumps blood

● Diastole: relaxation phase → chambers filled with blood

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MAIN IDEAS / KEY

POINT EXPLANATION NOTES

Stages of cardiac cycle

3 stages

1. Atrial and ventricular diastole - 0.4 sec ● Atria and ventricles are relaxed ● Ventricles relax & ventricular pressure is below that of

aorta & pulmonary arteries

● Semilunar valves close to prevent backflow of blood from arteries to the ventricles

● The closing of semilunar valves and recoil of blood against semilunar valves produce ‘dup’ sound

● AV valves open ● Allow blood to pass through to the ventricles. ● Deoxygenated blood from the superior and inferior vena

cava flows into the right atrium

● Oxygenated blood from pulmonary veins flows into left atrium.

2. Atrial systole and ventricle diastole – 0.1 sec

● SA node triggers the atria to contract. ● All blood is pumped out of atria into ventricles ● The AV valves open ● Atria empty its content into the ventricles.

3. Ventricular systole and atrial diastole - 0.3 sec

● Ventricles receives impulses from the Purkinje fibers and contract

● High pressure of blood forces semilunar valves to open ● Forcing blood into pulmonary arteries (deoxygenated

blood) and aorta (oxygenated blood)

● Pressure generated by powerful contraction of ventricles closes AV valves

● The closing of the AV valves and the recoil of blood against closed AV valves produce ‘lub’ sound

● Prevents the blood from flowing back into atria.

c) Explain ECG Definition

● A test that records the electrical activity of the heart. ● Impulses from SA node spread rapidly within heart tissue

generates currents that are conducted to the skin via body

fluids

● These electrical currents can be detected by electrodes placed on the skin and is recorded as an electrocardiogram (ECG)

● The resulting graph of current against time has a characteristic shape that represents the stages in the cardiac cycle

Functions

• ECG is used to diagnose the heart abnormalities.

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MAIN IDEAS / KEY

POINT EXPLANATION NOTES

d) Factors effecting

heartbeat

pH

• High CO2 cause pH drop

• Stimulate brain to accelerate heart rate

• Enhances delivery of oxygen rich blood to body tissue

• CO2 reach blood to the lungs for removal of CO2

• Blood pH back to normal

Body temperature

• Increasing of body temperature increase the heartbeat.

• Increasing 1oC will increase heart beat (10 times/minute)

• Lowering the body temperature (hypothermia) decreased the heartbeat.

• Depending on the temperature relative to the body, blood vessels will either dilate or contract.

• If temperature increase, blood vessels dilate (releases heat), blood pressure will decrease

• To keep blood pressure stable, the heart has to pump faster.

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SUBTOPIC : 8.2 Human Lymphatic System

LEARNING OUTCOME :

a) Describe the pathway of lymph from tissue to blood circulatory system

b) Describe the transport of lipids from small intestine into the blood stream

MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

a) Describe the

pathway of lymph

from tissue to blood

circulatory system

Lymphatic system

• The networks of vessels that conveys lymph from the tissue fluids to the bloodstream

• Consists of :

• Lymph - fluid that resembles plasma but contain high concentration of suspended protein

• Lymphatic vessels - carry fluid called lymph throughout body

• Lymph nodes - Filters lymph for foreign particles or pathogens

Lymphatic organs

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

Lymphatic organs Functions

Bone marrow produce lymphocytes and sites of

maturation for B lymphocytes.

Thymus gland sites of maturation for T lymphocytes

Spleen destroy worn-out erythrocytes and

pathogens

Tonsil trap and destroy pathogens that enter

through mouth by secreting antibody

Lymph nodes small glands that filter lymph, the clear

fluid that circulates through the

lymphatic system

Functions of lymphatic system

• Transport excess interstitial fluid back to the blood

• Absorbed and transport fats and some vitamins from small intestine to the blood

• Provide immunological defense against disease -causing agents.

Fluid return by lymphatic system

• High hydrostatic pressure in the blood capillary cause small amount of fluid enter the tissue spaces

➔ Become interstitial fluid

• Not re-enter the blood capillaries but return to blood via lymphatic vessels.

• This fluid enters the lymphatic system by diffusing into tiny dead, space-end lymphatic capillaries that are intermingle

among blood capillaries

➔ Called lymph

• Lymph circulates within the lymphatic system before

draining into a pair of large veins of the cardiovascular

system at the base of the neck.

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

• Pathway of lymphatic fluid :

• The movement of lymph from peripheral tissues to the heart relies on many of the same mechanisms that assist blood from

vein.

• Lymph vessel, like veins have valves that prevent the backflow of fluid.

• Rythmic contraction of vessel wall help draw fluid into small lymphatic vessels.

• In addition, muscle contractions play a role in moving lymph.

• Along a lymph vessel are small lymph-filtering organs called lymph nodes which play an important role in body’s defense

b) Describe the

transport of lipid

from small intestine

into the blood stream

● Lipid is digested into fatty acids and glycerol (monoglyceride)

● Fatty acid and glycerol enter the villi of the small intestine ● By diffusion/facilitated diffusion/active transport ● Triglycerides are resynthesized from fatty acids and

glycerol and then combine with protein to form

chylomicrons / lipoprotein

● Chylomicrons / lipoprotein enter the lymphatic system through lacteal.

● Lacteal are lymphatic capillaries in the villi of the small intestine

● Lymph containing chylomicrons / lipoproteins is known as chyle.

● Chyle is then transported through lymphatic vessels into lymphatic system.

Blood

capillaries

Interstitial

fluid

between

cells

1.Lymphatic

capillaries

Subclavian

veins

2. Lymphatic

vessels

3. Lymphatic

nodes

4. Lymphatic

trunks

5. Lymphatic

ducts

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

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SUBTOPIC : 8.3 Transport In Plants

LEARNING OUTCOME :

a) State the pathway of water movement in root

b) State the water and mineral movement via xylem in stem

c) State the Pressure Flow hypothesis in phloem

d) Explain the lateral pathway of water and mineral is transported from surrounding soil to the root vascular

system

e) Describe water movement via xylem by transpiration-cohesion-tension mechanism and root pressure

f) Explain the Pressure Flow Hypothesis in phloem

MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

a) State the pathway of

water movement in

root

Water enters the plants through:

Soil → epidermis → cortex → xylem

b) State the water and

mineral movement

via xylem in stem

• Once water move into tracheids and vessel elements of root xylem, it travels upward through continuous network of

these hollow, dead cells from root to stem to leaf.

• Dissolved minerals are carried along passively in the water.

• Water moves to the top of plants either pushed up from the bottom of the plant or pulled up from the top of the plant by

:

• Root pressure

• Cohesion-tension mechanism

• Transpiration

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

d) Explain the lateral

pathway of water

and mineral is

transported from

surrounding soil to

the root vascular

system

• Roots are highly selective about which ions they take up in any quantity from the soil

• They may move into the roots by facilitated diffusion or against concentration gradient by active transport

• Example of mineral ions: Na+, K+, Ca2+, Mg2+, S, Fe, Zn, Cu2+.

• Mineral ions: – dissolved in water – enter roots hair cells mostly by active transport – crossing root cortex through apoplast and

symplast pathway

– By facilitated diffusion or active transport until they reach endodermis

Pathway

3 pathways of water transported from the surrounding soil to the

root :

• Apoplastic pathway

• Symplastic pathway

• Vacuolar pathway

1. Apoplastic pathway

• Water & mineral ions are transported along the cell wall without passing through the membrane

• Casparian strip effectively blocks the apoplastic pathway at the endodermis.

• Water enters the stele through the symplastic pathway.

• Prevents leakage of water from xylem vessels and aids the development of root pressure (an upwards force

pushing water up the stem).

2. Symplastic pathway

• Water & ions are transported through the cytoplasm/ protoplasm

• From a cell to another cell through plasmodesmata.

3. Vacuolar pathway

• The symplast can also have the subdivision of the vacuolar pathway

• Water & ions are transported from vacuole to vacuole of the neighbouring cells across the cytoplasm & tonoplasts.

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

Apoplast pathway and symplast pathway

Vacuolar pathway

e) Describe water

movement via xylem

by transpiration-

cohesion-tension

mechanism and root

pressure.

Structures of xylem

Xylem is a mixture of different cells

• Parenchyma

• Sclerenchyma fibers

• 2 types of conducting cells that allowing water and dissolved minerals to move

✓ Tracheid - thin with tapered, overlapping ends joined by pits

✓ Vessel elements - the end walls of some vessel elements are absent, and others have narrow

openings that connect adjacent vessel elements

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

Water movement via xylem

1. Root pressure

• The pressure in the xylem sap as a result of the active absorption of mineral ions

• Mineral ions that are actively absorbed from the soil lowers the water potential in root cells

• Water potential in the soil become higher

• Water moves into the root cells by osmosis

• Water accumulate in root tissues

• Produces hydrostatic pressure (root pressure

• Pushes xylem sap to move upward from root to leaves through the xylem

2. Cohesion

• In the stem

• The force of attraction between water molecules caused by hydrogen bonding.

• Allow unbroken column of water to be pulled up along the xylem.

3. Adhesion

• Attractive force between water molecules and the xylem walls

• Help to prevent the water column from moving down

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

4. Transpiration pull

• Water evaporates from the mesophyll cells into the atmosphere

• The loss of water lowers the water potential of the mesophyll cells

• Produces tension in the xylem

• Creates a force that pulls water upward.

• Water moves into the mesophyll cells by osmosis from the adjacent cells (higher water potential)

f) Explain Pressure

Flow hypothesis in

phloem

Translocation

Movement of organic solute from the leaves (source)

to the sieve tubes and to be carried to other parts of the plant

(sink)

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

Structure of phloem

• Phloem is a mixture of different cells

Sieve tube members

▪ Structure: long cylindrical ▪ arranged end-to-end forming long sieves tube ▪ Porous cross walls called sieve plates in between the sieve

tube cells

Companion cells

▪ Closely associated with the sieve tube ▪ Smaller and shorter than sieve tube ▪ Connected to the sieve tube by plasmodesmata

Components involve in translocation

• Sugar source: sugar production organ - Leaves

• Sugar sink: sugar storage organ

- Growing roots, tips, stems and fruits

Pressure Flow Hypothesis

• At the source cell (example leaf), glucose is produced by photosynthesis and converted to sucrose.

• Sucrose is loaded from the source cells into the sieve tube by active transport.

• The companion cell supplies the ATP for active transport

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MAIN IDEAS / KEY

POINT

EXPLANATION NOTES

• The accumulation of sucrose (solute) lowers the water potential in the sieve tube

• Water moves by osmosis from the xylem into the sieve tube.

• The entry of water generates a high hydrostatic pressure (or turgor pressure) in the sieve tube near the source cells.

• Hydrostatic pressure in the sieve tube near the sink cells (example: fruits) is low.

• This creates a difference of hydrostatic pressure along the sieve tube -between the source and sink

• Hydrostatic pressure forces phloem sap to flow along sieve tube from source to the sink cells.

• Sucrose is unloaded from sieve tube into the sink cells by active or passive transport depends on the concentration of

sucrose in the sink cells.

• This increased the water potential in the sieve tube near the sink.

• Water moves out from sieve tube into the xylem by osmosis.