Bio 1.1

Define Diffusion

The movement of molecules or ions from a region of their high concentration by relatively slow random movements of molecules

How are substances diffused in multicellular organisms

Through mass flow, where all the particles in a liquid move in one direction due to differences in pressure.

what are the three features of an open circulatory system

No blood vessels only cavities

diffusion occurs directly between blood and cells

State features of closed circulatory systems

Blood vessels

High blood pressure compared to open

Blood travels faster and more efficiently

Why is water a good transport medium?

Polar (dipole) molecule- slight opposite charges on hydrogen (positive) and oxygen (negative) molecules

Hydrogen bonding occurs between multiple water molecules and other polar molecules

What are cohesion forces?

Hydrogen bonds between water molecules

What are adhesion forces?

Hydrogen bonds between water molecules and other po

Why do ionic substances dissolve in water

Anions (such as Cl-) are attracted to the slightly positive hydrogen and cations (such as Na+) are attracted to slightly negative oxygen, allowing them to be surrounded and the bond becomes hydrated.

Describe the thermal properties of water

Water has a high specific heat capacity, so a large amount of energy only increases the temperature by a small amount

The hydrogen bonds in water are weak, but are so plentiful it takes a lot of energy to break them all

Describe features of arteries

Narrow lumen to maintain high pressure

Thicker walls to maintain high pressure

More collagen to withstand high pressure

More smooth muscle and elastic fibres to maintain high pressure

No valves

Describe the features of veins

Wide lumen

Thinner walls

Less collagen, smooth muscle and elastic fibres

Valves to prevent back flow of blood

How do you measure diameter of the lumen of a vein

From the widest possible points

What is the equation for magnification?

Image size / actual size = magnification

Describe the cardiac cycle

Cardiac diastole- muscles relax, atrioventricular valves begin closed but may open due to gravity, atria fill up with blood. Semilunar valves closed.

Atrial systole- atria contract, increasing pressure and pushing blood through atrioventricular valves. Semilunar valves are closed.

Ventricular systole- ventricles contract from the bottom up, pushing blood into aorta/ pulmonary artery. Semilunar valves are open, atrioventricular valves are closed due to the pressure of blood moving upwards.

What happens when blood reaches the capillaries

There is a steady flow of blood

Blood is slowed by the friction against the capillary wall

Substances exchange through the single-cell thick capillary walls

Describe how blood moves through the veins

Steadily and without pulses

Skeletal muscles push blood through

Low pressure in the thorax draws blood back into the heart

Valves close and open with the flow of blood, preventing back flow

What is atherosclerosis

When fatty deposits form in arteries, reducing blood supply and leading to conditions such as strokes or heart attacks

Describe the process of atherosclerosis

The endothelium is damaged due to high blood pressure or toxins from cigarettes

An inflammatory response occurs and white blood vessels accumulate at the site of damage.

White blood cells react with cholesterol to form a fatty deposit.

Calcium salts and fibrous tissue build up at the site forming a hardened plaque.

Smooth muscle grows over the atheroma, causing further narrowing of the lumen and a loss of elasticity in the artery

What happens when an atheroma causes a loss of elasticity

a positive feedback loop

Describe the steps of blood clotting

Platelets stick to eachother forming a platelet plug

Thromboplastin is released

In the presence of vitamin K and calcium ions, thromboplastin <converts> prothrombin into thrombin

Thrombin catalyses the <conversion>of fibrinogen into fibrin

Fibrin forms a mesh which traps platelets and red blood cells forming a clot.