Biology topic 1 lifestyle health and risk (1.1)

health definition

a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity

Why is the circulatory system important?

because we use mass transport systems to overcome limitations of diffusion meeting the requirements of organisms

why do unicellular organisms not have circulatory systems?

unicellular organisms such as bacteria and amoeba can obtain nutrients and secrete waste simply by diffusion

Why do larger organisms need specialised transport systems?

increased transport distances.

surface area: volume ratio.

increasing levels of activity they have more cells so more nutrients, gases and waste products.

as well as being more complex therefore needing more energy.

what do circulatory systems need?

-> pump.
-> vessels.
-> transport medium.

what does the pump in a circulatory system do?

contracts to put pressure on the transport medium (blood). the pressure generates movement of the fluid and transport by mass flow.

what do vessels do in a circulatory system?

keep the fluid at high pressure so can move greater distances.

what does the transport medium do?

transports substances by dissolving them and moving them by mass flow.

What are cardiovascular diseases?

diseases of the heart and blood vessels

Diffusion definition

movement of molecules or ions from a region of their high concentration to a region of their low concentration by relatively slow random movement of molecules

describe how open circulatory systems work

blood circulates in large open spaces. A simple heart pumps blood into cavities surrounding the animal's organs. substances can diffuse between the blood and cells. when the heart muscles relax blood is drawn from the cavity back into the heart through small valved openings along its length.

open circulatory system advantages

- receives less energy for distribution.
- more suited to animals with slower metabolism and smaller body.

open circulatory system disadvantages

- due to absence of arteries, blood pressure remains low and oxygen takes longer to reach body cells
- almost impossible to increase blood distribution
- because the heart causes blood to fill into body cavities, the total capacity of the system is filled with every heartbeat. makes it difficult to increase velocity or distribution

describe how blood flows through a closed circulatory system

- The blood leaves the heart under pressure and flows along the arteries and then arterioles to capillaries.
- the capillaries come into close contact with most of the cells in the body where substances are exchanged between blood and cells
- after passing along the capillaries the blood returns to the heart by venules then veins
- valves ensure blood only flows in one direction

describe how blood flows through a fish with a single circulatory system

- the heart pumps deoxygenated blood to the gills.
- gaseous exchange takes place in the gills; there is diffusion of carbon dioxide from the blood into the water that surrounds the gills, and diffusion of oxygen from this water into the blood within the gills.
- the blood leaving the gills then flows round the rest of the body before eventually returning to the heart.

so the blood flows through the heart once for each complete circuit of the body.

what animals have double circulation?

birds and mammals

describe what happens in double circulation

- the right ventricle of the heart pumps deoxygenated blood to the lungs where it receives oxygen.
- the oxygenated blood then returns to the heart to be pumped a second time (by the left ventricle) out to the rest of the body.

how does a double circulatory system boost metabolism?

the heart gives the blood returning from the lungs an extra boost that reduces the time it takes for the blood to circulate the whole body. this allows birds and mammals to have a high metabolic rate as oxygen and food substances required for metabolic processes can be delivered more rapidly to cells and meet the needs or the organism.

what do both the walls of veins and arteries contain

collagen

what features do arteries have

- thick, smooth muscular walls.
- elastic fibre/tissue.
- folded endothelium.
- narrow lumen.
- smooth lining.
- collagen

what do the arteries thick smooth muscular walls do?

maintain high pressure without damage.
contract/exert pressure

what do arteries elastic fibre/tissue do?

elastic stretch to accommodate high pressure/recoil to maintain pressure on blood

what does the folded endothelium do?

allows stretching to accommodate high pressure

what does a narrow lumen im arteries do?

maintains high pressure

what does a smooth lining in an artery do?

reduce friction/resistance to blood flow

what does collagen do?

avoid damage/rupture

describe the structure of an artery

lumen, endothelium, muscle and elastic tissue and outer coat (connective tissue with collagen fibres)

what features does a vein have?

thinner walls, valves, large lumen.

describe the structure of a vein

outer coat, muscles and elastic tissue, endothelium, lumen

what does a veins thin walls do?

allow skeletal movement and low heart pressure to draw blood to heart

what does a veins valves do?

ensures blood continues to move towards heart

what does a veins large lumen do?

ensures blood flows back to heart under low pressure

capillary features

very thin walls, large network near cells of tissue, narrow lumen

why are capillary walls thin

reduces diffusion distance, higher rate of diffusion

why is there a large network of capillaries

increase surface area, higher rate of diffusion

why does a capillary have a narrow lumen

just large enough for one red blood cell. reduces diffusion distance between RBC and tissue cells

how does blood move through vessels

Every time the heart contracts (systole) blood is forced into the arteries and their elastic walls stretch to accommodate the blood.
During relaxation of the heart (diastole) the elasticity of the artery walls cause them to recoil pushing the blood forward.
By the time the blood reaches smaller arteries and capillaries there is already a steady flow of blood. blood flows more slowly in capillaries due to their narrow lumen causing more of the blood to be slowed down by friction against the capillary walls.
This slower flow allows exchange between blood and the surrounding cells.

What type of molecule is water?

polar molecule

What makes water a polar molecule?

It has a positive hydrogen side and a negative oxygen side. water is dipole.

what properties does water have due to its hydrogen bonds?

- high melting and boiling temperatures.
- high specific heat capacity.
- high latent heat of vaporisation.
- cohesion.
- adhesion.
- lower density on freezing.

what do waters solvent properties allow it to do?

- act as a transport medium (dissolving important substances)
- act as a medium for biochemical reactions (dissolving the substrates and products)
- acts as a habitat allowing aquatic organisms to exchange substances with their environment

why do many chemicals dissolve easily in water?

due to their dipole nature allowing vital biochemical reactions to occur in the cytoplasm

what happens when ionic substances such as sodium chloride dissolve in water?

the negative CL- ions are attracted to the positive ends of the water molecules while the positive Na+ ions are attracted to the negative ends of the water molecules. The chloride and sodium ions become hydrated in aqueous solution, they become surrounded by water molecules.

what do polar substances do in water?

dissolve easily. their polar groups become surrounded by water and go into solution. such polar substances are hydrophilic

what do non-polar substances do in water?

non-polar substances, hydrophobic substances do not dissolve in water

what do lipids do to enable transport in blood?

lipids are hydrophobic substances so do not dissolve in water. to enable transport in blood, lipids combine with proteins to form lipoproteins.

describe the specific heat capacity of water?

high because a large amount of energy is required to break hydrogen bonds. a large input of energy only affects temperature a little bit.

why is water having a high specific heat capacity useful for organisms?

helps them to avoid rapid changes in internal temperature and enabling them to maintain a steady temperature even when the temperature in their surroundings changes considerably. this is also means the temperature of the bodies of water in which aquatic organisms do not change rapidly.

cohesion definition

tendency of water molecules to stick to each other. cohesion of water leads to a high surface tension

adhesion definition

The tendency of molecules to be attracted to other molecules of a different type

where is the heart located

• between the two lungs and above the diaphragm.

• enclosed by the pericardium.

• pericardial fluid is secreted between them to aid movement.

• the pericardium protects the heart from over expansion

What does the pericardium do?

Protects and anchors the heart.

Prevents overfilling of the heart with blood.

Allows for the heart to work in a relatively friction-free environment

describe the structure of the heart

- the heart is divided into two sides by a wall of muscle called the septum.
- the left side of the heart is thicker than the right.
- there are four chambers in the heart - two atria and two ventricles.

describe the structure and function of the atria

they are the two upper chambers on the left and right side of the heart.
receive blood from the lungs / rest of the body.
the atria pump blood to the lower chambers (ventricles).

describe the structure and function of the ventricles

the ventricles pump blood out of the heart.
the right ventricle pumps to the lungs and the left to head and body. this is why the left side is more muscular.
the atria and ventricles are separated by valves.
these valves are held in place by tough tendons - heart strings.
these tendons are attached to the heart wall via papillary muscles.

what are the valves on the right side of the heart?

tricuspid valves, three flaps of tissue

what are the valves on the left side of the heart

bicuspid valves - two flaps of tissue

what are the valves in the pulmonary artery and aorta?

semi-lunar valves. they prevent blood flowing back to the heart, allowing it to pass to the rest of the body or lungs.