Biology - Topic 1 - Lifestyle, health and risks

What is the primary purpose of the heart and the circulatory system in the body?

To move substances around the body by mass flow

In small organisms (such as unicellular creatures) how are substances moved around? e.g oxygen, carbon dioxide

Via diffusion only

What is mass flow?

The transport of substances in bulk from one part of an organism to another

What is diffusion?

the net movement of molecules or atoms from a region of high concentration to a region of low concentration until evenly distributed (dynamic equilibrium)

Describe 4 features of a mass flow system:

• A system of vessels (usually tubes) - arteries, veins, capillaries - to carry substances

• A way of making sure the substance move in the right direction - valves in veins/high pressure generated by heart contraction

• A means of moving the substances fast enough to supply the needs of organisms - high pressure, fast blood flow

• A suitable transport medium

Why can’t large organisms rely on diffusion?

This process is too slow to meet their needs. Mass transport enables organisms to overcome the limitations of diffusion

4 features of open circulatory systems:

• Blood isn’t enclosed within blood vessels, blood flows into large cavities. Blood is in direct contact with body tissues

• When blood is in direct contact with tissues, only then exchange of materials takes place

• Lower blood pressure, blood travels slower, less efficient at delivering substances around the body

• Generally animals with open circulatory systems are smaller in size

4 features of closed circulatory systems:

• Blood is always enclosed in blood vessels i.e. arteries, capillaries, veins

• In capillaries, nutrients and waste materials are exchanged between tissues and blood by means of tissue fluid (faster removal of waste products)

• Higher blood pressure, blood travels faster, more efficient at delivering substance around the body - faster delivery of oxygen + glucose to cells for aerobic respiration

• Generally animals with closed circulatory systems are larger in size e.g. mammals

Describe the critical difference between an open and closed circulatory system:

Open - blood isn’t enclosed within blood vessels

Closed - blood is always enclosed in blood vessels

Give an example of an animal which has an open system, and another that has a closed system:

Open - cricket

Closed - monkey

What is the main disadvantage of an open circulatory system?

Lower blood pressure, blood travels slower, less efficient at delivering substances around the body

Describe the essential difference between a single and double circulatory system:

Single - Blood flows through the heart once for each complete circuit in the body

Double - Blood flows through the heart twice for each complete circuit in the body

Give an example of an animal that has a single, and another with a double system:

Single - fish

Double - human

What is the main advantage of a double circulatory system over a single circulatory system:

Blood is pumped at a higher pressure

What does the circulatory system provide cells with?

Oxygen and glucose needed for aerobic respiration

How is blood pumped from the left ventricle?

The LV pumps blood faster, and at a higher pressure to the body

How is blood pumped from the right ventricle?

The RV pumps blood slower, and at a lower pressure to the lungs. This is important as it reduces the risk of damage to the lung capillaries.

Describe why water is a polar molecule:

Oxygen is more electronegative, causing an uneven distribution of charge. Because the molecule is bent, the dipoles don’t cancel, so water has an overall dipole

What type of substances dissolve in water and why does this occur?

Hydrophilic substances - forming hydrogen bonds between substances

Why is it important for substances to dissolve in water?

So that the dissolved substances can be transported around organisms, via the blood - allows biochemical reactions to occur

Apart from being a solvent water has other important biological properties.. Describe 2 of these properties

• Water molecules are highly cohesive - molecules stick to each other

• Water is colourless - allows photosynthesis to occur in aquatic environments

What are hydrophilic substances?

Dissolve in water, water attracting

What are hydrophobic substances?

Do not dissolve in water, water repelling

In a water molecule…

the oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge

When sodium chloride is dissolved in water, the sodium ions…

are attracted to the oxygen atoms of water molecules

Hydrogen bonds…

hold water molecules to one another

When a glass is filled to the brim with water, the water appears to bulge from the sides of the glass due to..

cohesion

When liquid water is heated, most of the energy that the water initially absorbs is used to…

break the hydrogen bonds between the molecules

Why is water a good solvent?

It is a polar compound- uneven distribution of charge

Define the term cohesion:

Because each water molecule is polar (oxygen is slightly negative, hydrogens are slightly positive), hydrogen bonds form between molecules. This causes them to stick together.

When liquid water is heated, most of the energy that the water initially absorbs is used to…

break the hydrogen bonds between the water molecules

What kinds of substances besides water can be involved in hydrogen bonding?

Substances with H bonded to N, O or F — e.g. ammonia, HF, alcohols, carboxylic acids, amines

What property of water allows it to stick to a dry surface, such as a wooden countertop?

Adhesion

Define the term adhesion:

The attraction between water molecules and other polar molecules or surfaces, due to hydrogen bonding

How does water help cells keep an even temperature despite temperature changes in the environment?

Water has a high specific heat capacity, so it resists rapid temperature change and keeps cells stable

Water is often called the universal solvent because it dissolves most substances that are important to living things. What does this suggest about the nature of these substances?

This suggests that most substances important to living things are polar or ionic, so they can form interactions (like hydrogen bonds or ion-dipole interactions) with water

Why is it good many chemicals dissolve in water?

allow vital biochemical reactions to occur in the cytoplasm of cells.

Name some ionic molecules that dissolve easily in water

Sodium Chloride (NaCl)

Describe how sodium chloride dissolves 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

Name some polar molecules that also dissolve easily in water

OH(-) group in sugars, or the amine group (-)NH2 in amino acids

Describe Diastole:

• Semi-lunar valves close, preventing backflow 

• Atrioventricular valves open 

• Blood flows into the ventricles

• Atria and ventricular muscles are relaxed

• Pressure in ventricles drop

Describe Atrial Systole:

• Muscles in walls of atria contract 

• Pressure in atria is above pressure in ventricles

• So atrioventricular valves open 

• Blood flows from the atria to the ventricles 

• Semi-lunar valves are closed

Describe Ventricular Systole:

• Muscles in walls of ventricles contract 

• Pressure in ventricles rises above pressure in atria 

• Atrioventricular valves close and prevent backflow of blood to the atria 

• Pressure in ventricles rises above pressure in arteries 

• Semi-lunar valves open

• Blood flows from the ventricles to the arteries 

Describe how valves open and close:

• Open when pressure is higher behind the valve 

• Close when pressure is higher in front of the valve

• Prevent backflow of blood

Explain how the AV valves open and close:

• Atrioventricular valves open when the pressure is higher in the atria compared to the ventricles 

• They close when the pressure is higher in the ventricles compared to the atria

Explain how to the semi-lunar open and close:

• Semi-lunar valves open when the pressure is higher in the ventricle compared to the arteries 

• They close when the pressure is higher in the arteries compared to the ventricles 

What does myocardial infarction mean?

(heart attack) death to areas of cardiac muscle due to lack of oxygen/blood flow as a result of a blockage in a coronary artery

What does a stroke mean?

sudden death of some brain cells due to lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain

What does aneurysm mean?

a localised, blood-filled balloon-like bulge in the wall of a blood vessel

What does thrombosis mean?

the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system

What does endothelial dysfunction mean?

Damage to the delicate endothelial cells lining blood vessels e.g can be caused by harmful chemicals from cigarette smoke (e.g CO) by viral infection, high blood pressure etc.

List 2 reasons for endothelium damage:

• Hypertension

• Smoking

What causes an inflammatory response?

damage to the endothelium/ wall of arteries

Name 3 irritants:

• Lipids (LDL cholesterol)

• Toxins (cig. smoke)

• High blood pressure (hypertension)

What is an atheroma?

the accumulation of cholesterol

What do the white blood cells unsuccesfully do?

Try to eat the cholesterol accumulated so they die off and also accumulate around the endothelial cells

What builds up around the atheroma?

calcium salts and fibrous tissue build up forming a plaque- atherosclerosis

In turn, what ends up happening to the lumen of the blood vessel?

As atherosclerosis happens it will narrow the lumen of the vessel

Why is this narrowing of the lumen bad?

A narrower lumen means less elastic walls so there will be higher blood pressure- further damage to the artery walls (positive feedback)

What particles does the blood contain that cause the blood to clot?

Platelets

What do these platelets come into contact (are attracted to) with in the artery wall?

Collagen

What do these platelets do?

Stick to damaged area and each other forming a platelet plug

What do these platelets and damaged tissue release?

Thromboplastin (enzyme)

What is then present?

Calcium ions and Vitamin K

What does thromboplastin catalyse?

Catalyses the conversion of prothrombin (inactive enzyme) into an enzyme called thrombin

What does this thrombin do?

Catalyses the conversion of fibrinogen into fibrin 

What does this fibrin do?

It is insoluble in water and forms a mesh over the damaged area

Define risk:

the probability of ocurrence of some unwanted event or outcome

Define probability:

has a precise mathematical meaning and can be calculated to give a numerical value for the size of the risk i.e. the extent to which an event is likely to occur, measured by the ratio of the favourable or unfavourable cases to the whole number of cases possible

Define correlation:

a change in one of the variables is reflected by a change in the other variable 

Define causation:

when a change in one variable is responsible for a change in another variable

List at least 6 factors that increase the risk of cardiovascular disease:

• Smoking

• Obesity - increases blood pressure

• High salt diet - sodium

• Age - increasing age blood vessels loose elasticity 

• Gender - estrogen in women reduce the build up of plaque 

• Lack of exercise 

Name the controllable risk factors:

• Smoking

• Excessive alcohol consumption

• Obesity 

• Lack of exercise 

• High blood cholesterol levels 

• High blood pressure 

List the controllable dietary factors:

• High salt diet

• High saturated fat diet

• High cholesterol diet 

• High calorie diet 

• Low levels of antioxidants in diet (fruits and veg)

Name the uncontrollable risk factors:

• Age - getting older

• Gender - being male 

• Genetics - a family history of CVD 

• Also diabetes (type 1) GENETIC

Define hypertension:

Permanent or sustained high blood pressure (could be diastolic, systolic or both- each is indicative of a pathological condition) 

Define systolic blood pressure:

The pressure in an artery is highest during the phase of the cardiac cycle when the ventricles have contracted and forced blood into the arteries 

Define diastolic blood pressure:

Pressure is at its lowest in the artery when the ventricles are relaxed 

Define sphygmomanometer

A device used to measure blood pressure