Topic 3

Insects gas exchange 5 points

• air moves into the trachea through the spiracles ( surface pores)

• Oxygen travels down the conc gradient towards the cells

• Trachea branch off into tracheoles and go to individual cells - oxygen directly into respiring cells

• CO2 diffuse to spiracles into atmosphere

• Insects use rhythmical abdominal movements to move air in and out spiracles

Plant gas exchange

Guard cells open and close stomata

Mesophyll cells inside leaf have special pores stomata

How do insects minimise water loss

Can close spiracles with muscles

Tiny hairs around spiracles reduce evaporation

Waxy cuticle - waterproof body

How do plants minimise water loss

Water enters guard cells makes them turgid and open, when dehydrated pore closes

Xerophytic plant adaptions

waxy cuticles, reduced stomata

Alveoli adaptions fro gas exchange

Thin exchange surface

Large surface area

Inspiration ( 6 points)

• external intercostal and diaphragm contract

• Rib cage up and out

• Diaphragm flattens

• Vol increase thoracic cavity, pressure decrease

• Air high to low pressure

• Active process - requires energy

Expiration ( 6 points)

• external intercostal and diaphragm muscles contract

• Rib cage down and in

• Diaphragm curves

• Vol decrease, pressure increase

• Air high to low pressure

• Passive process

Forced expiration

internal intercostal muscles contract

External intercostal muscles relax

Dissecting fish gills

Pull back operculum

Use scissors to remove gills

Cut each gill arch through bone top and bottom

Gill filaments

Haemoglobin structure

Protein, 4 polypeptide chains

Haemoglobin when p02 is low

Low affinity - unloading e.g. at respiring tissues

Haemoglobin when p02 is high

high affinity - loading e.g. in lungs

Bohr effect 3 points

1 - when cells respire they release co2 raising partial pressure of co2

2 - this increases rate of 02 unloading so curve shifts right

3 - saturation of blood with 02 is lower for that p02 meaning more oxygen released

Higher affinity for oxygen which way shift?

Left shift

When do AV valves open

When ventricle pressure lower than atria pressure

Which ventricle thicker

left

What do cords do

Attatch AV valves to ventricles so there not forced into atria on contraction

Heart contraction 3 steps

1- ventricles relax, atria contract

2- ventricles contract, atria relax

3 - both relax, atria refill

Arteries adaptations for function (4)

• thick muscular walls

• Elastic tissue

• Folded endothelium

• Smaller lumen

  (These help keep high pressure)

Veins adaptations for function (3)

• wider lumen

• Valves to stop back flow

• Blood flow helped by contraction fo surrounding body muscles

Capillaries adaptations for function ( 3)

• near cells and tissues

• One cell thick

• Large number of them

Tissue fluid contents

• blood plasma, no RBC or big proteins

• Metabolic waste

Pressure filtration

• at start of capillary bed, hydrostatic pressure higher in capillaries

• Pressure forces fluid out of capillaries into spaces around cells

• Venule end of capillary low hydrostatic pressure

• Water potential at venule end lower than in tissue fluid

• Water re enters capillaries via osmosis

• Excess drained into lymphatic system

Myocardial infraction

Coronary artery gets blocked so no oxygen to part of heart

Xylem transport

1- water evaporates from leaves at top of xylem

2- creates tension pulling water

3- water cohesive so whole column of water moves

4- more water enters stem from roots

Mass flow hypothesis

• active transport loads solutes from companion cells to sieve tubes of phloem at source

• Lowers the water potential in sieve tubes

• Osmosis from xylem and companion cells, high pressure source end

• Sink end solutes remove increasing WP inside sieve tubes

• Water leaves tubes via osmosis lower pressure end

• Pressure gradient, solute moves source end to sink end