2.3 Adaptations for transport

What is an open circulatory system?

• blood bathed over tissues directly

• moved by muscular movements

• no respiratory pigment

Open circulatory system example

insects

• blood moves in spaces called haemocoel

• dorsal tube shape heart

What is a closed circulatory system and example?

• blood remains in blood vessels

• moved by heart pumps

• organs not in direct contact with blood

• respiratory pigment to carry gases

• e.g. earthworm

What is a single circulatory system and example?

• blood passes through heart once in a complete circulation

• e.g. fish

What is a double circulatory system and example?

• blood passes through heart twice in complete circuit

• e.g. mammals

Systems in double circulatory system

• pulmonary - to lungs

• systemic - to body

Double circulatory system advantages

• maintains higher pressure

• oxygenated and deoxygenated blood separated

• blood constantly delivered to cells

Blood vessel structure

• Tunica externa - collagen to resist stretching

• Tunica media - elastic fibers to sustain pressure

• Endothelium - thin/smooth to reduce friction

• Lumen

Arteries

• usually carry oxygenated blood away from heart

• thicker tunica media to allow recoil

• smaller branches called arterioles

• high pressure

Veins

• usually carry deoxygenated blood to heart

• valves prevent back flow

• large lumen for increased volume

• smaller branches called venules

• low pressure

Capillaries

• connect arteries and veins

• close contact with cells

• endothelium for short diffusion path

• exchanges substances

Heart pathway

Heart structure

What vessels surround the outer heart?

Coronary arteries

Atrial systole

• atria contract

• bi/tri cuspid valves open

• blood flows into ventricles

Ventricular systole

• ventricles contract

• bi/tri cuspid valves close

• semilunar valves open

• blood flows into arteries

• great pressure

Ventricular diastole

• heart muscle relaxes

• pressure decreases in ventricles

• semilunar valves close

Diastole

• whole heart relaxes

• blood flow into atria

• cardiac cycle begins again

What happens at sino-atrial node

1. stimulus to contract comes from sino-atrial node, found in right atrium

2. electrical impulse from SAN cause the two atria to contract

3. a thin layer of tissue prevents stimulus spreading to ventricles

What happens at atrio-ventricular node?

1. the atrio-ventricular node found between atria and ventricles delays the impulse before passing it onto ventricles

2. the AVN passes the impulse down the bundle of HIS which has branches of Purkinje fibers

3. the impulses are conveyed upwards along the Purkinje fibers which cause a wave of ventricular contraction from the bottom of the ventricle to the top

Electrocardiogram (ECG)

• P - atrial systole

• Q,R,S - ventricle depolarisation (contract after spike)

• T - ventricular diastole

Pressure changes around heart

Red blood cells

• carry 4 oxygen molecules a time

• made of haemoglobin

• made in bone marrow

• no nucleus

• biconcave disc shape - large SA

Bohr effect on oxygen dissociation curve

• more carbon dioxide

• shifts to right

• lower affinity for oxygen so more oxygen released

Foetal effect on oxygen dissociation curve

• cant mix with mothers

• shifts to left

• greater affinity for oxygen so more picked up

Low oxygen level effect on oxygen dissociation curve

• e.g. lugworm and llama

• shifts to left

• greater affinity for oxygen so more picked up

Chloride shift

1. Carbon dioxide produced by respiring tissues diffuses into fluid and cell

2. Carbonic Anhydrase catalyses the reaction between Carbon Dioxide and Water to form Carbonic Acid

3. Carbonic Acid dissociates to form H⁺ and HCO₃^- ions

4. HCO₃^- ions diffuse out and Cl^- ions diffuse in to maintain electrochemical neutrality

5. Oxyhaemoglobin and H⁺ ions form Haemoglobinic acid and Oxygen (buffering effect to maintain pH)

6. Oxygen diffuses out of cell into fluid and respiring tissue

When is chloride shift opposite way?

Lungs

How can Carbon dioxide be transported?

• chloride shift

• in solution in plasma

• bound to haemoglobin

Tissue fluid

1. blood coming into arteriole end is under high hydrostatic pressure so small molecules are forced out of capillary walls into tissue fluid

2. this is opposed by reduced water potential of blood due to plasma proteins not diffusing out

3. at the venous end blood hydrostatic pressure is lower so water passes into capillaries via osmosis

4. carbon dioxide and other excretory substances diffuse back into capillaries

Structure of TS root

Structure of TS stem

Root hair cell structure and functions

• water absorption

• mineral absorption by active transport

Adaptations of root hair cell

• extended cell wall + vacuole = large SA

• thin cell wall

• mitochondria for active transport

Apoplast water movement

• through cell walls

• after endodermis, goes symplast route

Symplast water movement

through cytoplasm and plasmodesmarta

Vacuolar water movement

through vacuole

Endodermis

• Contains a Casparian strip which controls the flow of water as it is waterproof due to the suberin in it

• Slows apoplast flow

Xylem structure

• 4 cells; vessels, tracheids, fibres, parenchyma

• vessels, tracheids, fibres dead as lignin is deposited in cell wall so impermeable to water

• parenchyma store water for support

• contains pitted walls and vessels

Xylem adaptations

• small diameter

• pit vessles so water moves laterally

• lignified for strength

What is root pressure

• osmotic pressure that build up within root cells forcing water up xylem

• nutrients pumped into xylem cause water to follow via osmosis

Transpiration

root > xylem > evaporation through stomata

Cohesion-tension theory

• Cohesion - hydrogen bonds

• Adhesion - stick to xylem walls

How does humidity affect transpiration

• decrease rate of evaporation

• lower concentration gradient

How does wind speed affect transpiration

• increase rate of evaporation

• wind removes water

• maintains concentration gradient

How does temperature affect transpiration

• increase rate of evaporation

• more kinetic energy

• too high will close stomata and stop evaporation