Topic 1 – Lifestyle, health and risk
1. Define an open circulatory system.
a. A simple heart pumps blood out into cavities surrounding the animal’s
organs. Substances can diffuse between the blood and cells.
b. When the heart muscle relaxes, blood is drawn from the cavity back into the
heart through small, valved, openings along its length.
2. Define a closed circulatory system.
a. Many animals, including all vertebrates, have a closed circulatory system in
which the blood is enclosed within tubes – blood vessels. This generates
higher blood pressure as the blood is forced along fairly narrow channels
instead of flowing into large cavities. This means the blood travels faster and
so the blood system is more efficient at delivering substances around the
body.
b. The blood leaves the heart under pressure and flows along arteries and then
arterioles to capillaries. There are extremely large numbers of capillaries.
These come into close contact with most of the cells in the body where
substances are exchanged between blood and cells.
c. After passing along the capillaries, the blood returns to the heart by means of
venules and then veins, valves ensure the blood flows only in one direction.
3. Define a single circulatory system.
a. Animals with a closed circulatory system have either single or double
circulation. Fish, for example, have single circulation.
i. The heart pumps deoxygenated blood to the gills.
ii. 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.
iii. It is known as a single circulatory system as the blood flows through
the heart once for each complete circuit of the body.
4. Define a double circulatory system.
a. Birds and mammals have a double circulation:
i. The right ventricle of the heart pumps deoxygenated blood to the
lungs where it receives oxygen.
ii. 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.
b. As the blood flows through the heart twice for each complete circuit of the
body, it is known as a double circulatory system. The heart gives the blood
returning from the lungs an extra ‘boost’ that reduces the time it takes for
the blood to circulate round the whole body.
c. This leads to birds and mammals having a high metabolic rate.
5. What is mass flow?
a. In the circulatory system a liquid and all the particles it contains are
transported in one direction due to a difference in pressure in a process
known as mass flow.
6. What does the transport medium in animals contain?
, a. In animals the transport medium is usually called blood. The fluid, plasma, is
mainly water and contains dissolved substances such as digested food
molecules (e.g. glucose), oxygen and carbon dioxide. Proteins, amino acids,
salts, enzymes, hormones, antibodies and urea, the waste product from the
breakdown of proteins, are some of the other substances transported in the
plasma. Cells such as red blood cells, white blood cells and platelets are also
carried in the blood.
b. Blood is not only important in the transport of dissolved substances and cells,
but also plays a vital role in regulation of body temperature, transferring
energy around the body.
7. What are the properties of water that make it a good transport medium?
a. Water is a polar molecule; the hydrogen end of the molecule is slightly
positive, and the oxygen end is slightly negative because the electrons are
more concentrated at that end. Therefore, water is said to be a dipole. Due
to this dipole nature, water contains hydrogen bonding which leads to a high
boiling point.
b. Due to its polar nature, other polar substances, as well as ionic and
hydrophilic substances can easily dissolve in water.
c. Non-polar, hydrophobic substances such as lipids do not dissolve in water. To
enable transport in blood, lipids combine with proteins to form lipoproteins.
d. Water also has a high specific heat capacity, a large input of energy causes
only a small increase in temperature, so water warms up and cools down
slowly. This is useful for organisms, helping them to avoid rapid changes in
their internal temperature and enabling them to maintain a steady
temperature even when the temperature in their surroundings varies
considerably. This also means that bodies of water in which aquatic
organisms live do not change temperature rapidly.
8. What is the heart made of?
a. The heart is a double pump and is made of cardiac muscle.
9. Define the structure of an artery.
a. The artery contains an outer coating – connective tissue with collagen, which
is a tough fibrous protein, making them strong and durable. They also contain
elastic fibres that allow them to stretch and recoil. They also contain smooth
muscle cells in the walls which allow them to constrict and dilate. They also
contain an endothelium layer.
b. Arteries contain a narrow lumen, thicker walls, more collagen, smooth
muscle and elastic fibres and no valves.
10. Describe the structure of a vein.
a. The vein also contains an outer coating – connective tissue with collagen, a
tough fibrous protein, making them strong and durable. They also contain
elastic fibres that allow them to stretch and recoil. Additionally, they also
contain smooth muscle cells in the walls which allow them to constrict and
dilate. Like arteries they also contain an endothelium layer.
b. Veins contain a wide lumen, thinner walls, less collagen and smooth muscle,
with fewer elastic fibres. They however also contain valves.
11. Describe the structure of a capillary.
, a. The capillaries that join the small arteries (arterioles) and small veins
(venules) are very narrow, about 10um in diameter, with walls that are only
one cell thick.
12. How does the blood move through the vessels?
a. As the heart contracts (systole), blood is forced into arteries and their elastic
walls stretch to accommodate the blood. The thick artery walls can withstand
the high pressure generated as the blood is forced against the walls.
b. During diastole (relaxation of the heart), the elasticity of the artery walls
causes them to recoil behind the blood, helping to push the blood forward
and smoothing blood flow. The blood moves along the length of the artery as
each section in series stretches and recoils in this way. The pulsing flow of
blood through the arteries can be felt anywhere an artery passes over a bone
close to the skin.
c. By the time the blood reaches the arterioles and capillaries there is a steady
flow of blood. Blood flows more slowly in the capillaries due to their narrow
lumens causing more of the blood to be slowed down by friction against the
capillary wall. This slower steady flow allows exchange between the blood
and the surrounding cells through the one-cell-thick capillary walls. The
network of capillaries that lies close to every cell ensures that there is rapid
diffusion between the blood and surrounding cells.
d. The heart has a less direct effect on the flow of blood through the veins.
Blood flows steadily and without pulses in veins where it is under relatively
low pressure. In the veins blood flow is assisted by the contraction of skeletal
muscles during the movement of limbs and breathing. Low pressure
developed in the thorax (chest cavity) when breathing in also helps draw
blood back into the heart from the veins. Backflow is prevented by the
semilunar valves within the veins.
13. How does the heart obtain a blood supply?
a. Since the heart is a muscle, it needs a constant supply of fresh blood carrying
oxygen and glucose for aerobic respiration. The heart muscle does not obtain
oxygen and nutrients from the blood inside its pumping chambers due to the
large diffusion distances involved. Instead, the heart muscle is supplied with
blood through its own coronary circulation; two vessels called the coronary
arteries, a network of capillaries, and two coronary veins.
14. What is atrial systole?
a. Blood returns to the heart due to the action of skeletal and muscles involved
in breathing as you move and breathe.
b. Blood under low pressure flows into the left and right atria from the
pulmonary vein and vena cava.
c. As the atria fill, the increasing pressure of blood against the atrioventricular
valves pushes them open and blood begins to leak into the ventricle.
d. The atria walls contract forcing more blood into the ventricles. The
contraction of the atria is known as atrial systole.
15. What is ventricular systole?
a. After a slight delay, atrial systole is followed by ventricular systole. The
ventricles contract from the base of the heart upwards, increasing the
pressure in the ventricles.
1. Define an open circulatory system.
a. A simple heart pumps blood out into cavities surrounding the animal’s
organs. Substances can diffuse between the blood and cells.
b. When the heart muscle relaxes, blood is drawn from the cavity back into the
heart through small, valved, openings along its length.
2. Define a closed circulatory system.
a. Many animals, including all vertebrates, have a closed circulatory system in
which the blood is enclosed within tubes – blood vessels. This generates
higher blood pressure as the blood is forced along fairly narrow channels
instead of flowing into large cavities. This means the blood travels faster and
so the blood system is more efficient at delivering substances around the
body.
b. The blood leaves the heart under pressure and flows along arteries and then
arterioles to capillaries. There are extremely large numbers of capillaries.
These come into close contact with most of the cells in the body where
substances are exchanged between blood and cells.
c. After passing along the capillaries, the blood returns to the heart by means of
venules and then veins, valves ensure the blood flows only in one direction.
3. Define a single circulatory system.
a. Animals with a closed circulatory system have either single or double
circulation. Fish, for example, have single circulation.
i. The heart pumps deoxygenated blood to the gills.
ii. 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.
iii. It is known as a single circulatory system as the blood flows through
the heart once for each complete circuit of the body.
4. Define a double circulatory system.
a. Birds and mammals have a double circulation:
i. The right ventricle of the heart pumps deoxygenated blood to the
lungs where it receives oxygen.
ii. 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.
b. As the blood flows through the heart twice for each complete circuit of the
body, it is known as a double circulatory system. The heart gives the blood
returning from the lungs an extra ‘boost’ that reduces the time it takes for
the blood to circulate round the whole body.
c. This leads to birds and mammals having a high metabolic rate.
5. What is mass flow?
a. In the circulatory system a liquid and all the particles it contains are
transported in one direction due to a difference in pressure in a process
known as mass flow.
6. What does the transport medium in animals contain?
, a. In animals the transport medium is usually called blood. The fluid, plasma, is
mainly water and contains dissolved substances such as digested food
molecules (e.g. glucose), oxygen and carbon dioxide. Proteins, amino acids,
salts, enzymes, hormones, antibodies and urea, the waste product from the
breakdown of proteins, are some of the other substances transported in the
plasma. Cells such as red blood cells, white blood cells and platelets are also
carried in the blood.
b. Blood is not only important in the transport of dissolved substances and cells,
but also plays a vital role in regulation of body temperature, transferring
energy around the body.
7. What are the properties of water that make it a good transport medium?
a. Water is a polar molecule; the hydrogen end of the molecule is slightly
positive, and the oxygen end is slightly negative because the electrons are
more concentrated at that end. Therefore, water is said to be a dipole. Due
to this dipole nature, water contains hydrogen bonding which leads to a high
boiling point.
b. Due to its polar nature, other polar substances, as well as ionic and
hydrophilic substances can easily dissolve in water.
c. Non-polar, hydrophobic substances such as lipids do not dissolve in water. To
enable transport in blood, lipids combine with proteins to form lipoproteins.
d. Water also has a high specific heat capacity, a large input of energy causes
only a small increase in temperature, so water warms up and cools down
slowly. This is useful for organisms, helping them to avoid rapid changes in
their internal temperature and enabling them to maintain a steady
temperature even when the temperature in their surroundings varies
considerably. This also means that bodies of water in which aquatic
organisms live do not change temperature rapidly.
8. What is the heart made of?
a. The heart is a double pump and is made of cardiac muscle.
9. Define the structure of an artery.
a. The artery contains an outer coating – connective tissue with collagen, which
is a tough fibrous protein, making them strong and durable. They also contain
elastic fibres that allow them to stretch and recoil. They also contain smooth
muscle cells in the walls which allow them to constrict and dilate. They also
contain an endothelium layer.
b. Arteries contain a narrow lumen, thicker walls, more collagen, smooth
muscle and elastic fibres and no valves.
10. Describe the structure of a vein.
a. The vein also contains an outer coating – connective tissue with collagen, a
tough fibrous protein, making them strong and durable. They also contain
elastic fibres that allow them to stretch and recoil. Additionally, they also
contain smooth muscle cells in the walls which allow them to constrict and
dilate. Like arteries they also contain an endothelium layer.
b. Veins contain a wide lumen, thinner walls, less collagen and smooth muscle,
with fewer elastic fibres. They however also contain valves.
11. Describe the structure of a capillary.
, a. The capillaries that join the small arteries (arterioles) and small veins
(venules) are very narrow, about 10um in diameter, with walls that are only
one cell thick.
12. How does the blood move through the vessels?
a. As the heart contracts (systole), blood is forced into arteries and their elastic
walls stretch to accommodate the blood. The thick artery walls can withstand
the high pressure generated as the blood is forced against the walls.
b. During diastole (relaxation of the heart), the elasticity of the artery walls
causes them to recoil behind the blood, helping to push the blood forward
and smoothing blood flow. The blood moves along the length of the artery as
each section in series stretches and recoils in this way. The pulsing flow of
blood through the arteries can be felt anywhere an artery passes over a bone
close to the skin.
c. By the time the blood reaches the arterioles and capillaries there is a steady
flow of blood. Blood flows more slowly in the capillaries due to their narrow
lumens causing more of the blood to be slowed down by friction against the
capillary wall. This slower steady flow allows exchange between the blood
and the surrounding cells through the one-cell-thick capillary walls. The
network of capillaries that lies close to every cell ensures that there is rapid
diffusion between the blood and surrounding cells.
d. The heart has a less direct effect on the flow of blood through the veins.
Blood flows steadily and without pulses in veins where it is under relatively
low pressure. In the veins blood flow is assisted by the contraction of skeletal
muscles during the movement of limbs and breathing. Low pressure
developed in the thorax (chest cavity) when breathing in also helps draw
blood back into the heart from the veins. Backflow is prevented by the
semilunar valves within the veins.
13. How does the heart obtain a blood supply?
a. Since the heart is a muscle, it needs a constant supply of fresh blood carrying
oxygen and glucose for aerobic respiration. The heart muscle does not obtain
oxygen and nutrients from the blood inside its pumping chambers due to the
large diffusion distances involved. Instead, the heart muscle is supplied with
blood through its own coronary circulation; two vessels called the coronary
arteries, a network of capillaries, and two coronary veins.
14. What is atrial systole?
a. Blood returns to the heart due to the action of skeletal and muscles involved
in breathing as you move and breathe.
b. Blood under low pressure flows into the left and right atria from the
pulmonary vein and vena cava.
c. As the atria fill, the increasing pressure of blood against the atrioventricular
valves pushes them open and blood begins to leak into the ventricle.
d. The atria walls contract forcing more blood into the ventricles. The
contraction of the atria is known as atrial systole.
15. What is ventricular systole?
a. After a slight delay, atrial systole is followed by ventricular systole. The
ventricles contract from the base of the heart upwards, increasing the
pressure in the ventricles.
