Chapter 8

Question 1

Why do multicellular organisms need transport systems ?

Answer 1

High metabolic rate- the demand for oxygen is too high to be supplied by diffusion over long distances
Size- the distance to inner cells is too far for diffusion to supply these cells with the oxygen needed
Surface area to volume ratio-. As an organism gets bigger the surface area to volume ratio becomes much smaller

Question 2

What is an open circulatory system

Answer 2

Insects have open circulatory systems
The heart pumps fluid called haemolymph through short vessels into a large cavity called the haemocoel
Here the haemolymph bathes the organs and tissues to diffuse substances
The heart relaxes and the haemolymph is sucked back via pores called Ostia

Question 3

What is a single closed circulatory system ?

Answer 3

The blood is enclosed in vessels and only passes through the heart once for each complete circuit of the body. Fish has single closed circulatory systems

Question 4

What is a double closed circulatory system?

Answer 4

The blood is enclosed in vessels and passes through the heart twice for each complete circuit

Question 5

What are arteries

Answer 5

Blood vessels which carry blood under high pressure away from the heart with thick muscular walls made of elastic fibres, smooth muscle and collagen
The elastic fibres allow them to stretch and recoil

Question 6

What are arterioles

Answer 6

Arteries branch into arterioles which have less smooth muscle and elastin
They can constrict and dialate to control the flow of blood to organs

Question 7

What are Capillaries?

Answer 7

Link arterioles and venules they are only one cell thick and have a large surface area for diffusion

Question 8

What are venules?

Answer 8

Venules link capillaries to veins they have very thin walls with a little smooth muscle

Question 9

What are veins?

Answer 9

Veins take blood under low pressure back to the heart. They have little elastic fibre or muscle tissue and large lumen to help flow. They have valves to prevent backflow

Question 10

What is the composition of blood?

Answer 10

It is 55% plasma which carries glucose, amino acids, hormones, proteins and mineral ions
It is 45% erythrocytes (red blood cells), platelets and leucocytes (white blood cells)

Question 11

How are tissue fluids formed ?

Answer 11

1) at the arteriole end of the capillary bed the blood has a higher hydrostatic pressure than the tissue fluid so fluid moves out of the blood into the tissue fluid
2) moving down the oncotic pressure caused by plasma proteins means water has a tendency to move into the blood by osmosis
3) at the venule end the hydrostatic pressure is much lower so fluid moves back into the capillaries
4) not all fluid re enters, the excess passes into a lymph vessel and becomes lymph where it is moved towards the main lymph vessel in the thorax and returned to the blood

Question 12

What is tissue fluid made up of?

Answer 12

Water, dissolved solutes, few white blood cells and few proteins

Question 13

What is lymph made up of?

Answer 13

Water, dissolved solids and white blood cells

Question 14

Draw a diagram of the structures of the heart

Answer 14

Diagram

Question 15

Explain the process of the cardiac cycle

Answer 15

1) SYSTOLE- Ventricles relax and atria contract decreasing thier volume increasing pressure causing the atrioventricular valves to open pushing blood into the ventricles
2) atria relax and ventricles contract decreasing thier volume and increasing thier pressure which forces the atrioventricular valves closed and the semi lunar valves open forcing blood out the pulmonary artery/ aorta
3) DIASTOLE The atria and ventricles relax the high pressure in the pulmonary artery and aorta cause the semi lunar valves to close preventing backflow . The low pressure caused the atrioventricular valves to open and the atria and ventricles to fill with blood

Question 16

Explain the process of heart activity

Answer 16

1) A wave of electrical excitement begins in the pacemaker area called the sino atrial node causing the atria to contract
2) A layer of non conducting tissue prevents the excitement from passing to the ventricles
3) The electrical activity from the sino atrial node is picked up by atrioventricular node which imposes a slight delay
4) The electrical activity is then passed on to the bundle of his, a bundle of conductive purkyne fibres
5) It splits into two branches of purkyne tissue which conducts the excitement to the apex of the heart then through each ventricle triggering a contraction from the bottom up.

Question 17

Cardiac output=

Answer 17

cardiac output= heart rate x stroke volume

Question 18

What is an electrocardiogram?

Answer 18

a machine that records the electrical activity of the heart.
The diagram consists of an P which is the contraction of the atria, the QRS complex- the contraction of the ventricle and T the relaxation of the ventricles.

Question 19

Problems that can be detected through electrocardiograms:

Answer 19

Tachycardia- heartbeat over 100 bpm
Bradycardia- heartbeat under 60 bpm
Atrial fibrillation- rapid contractions up to 400bpm
Ectopic heartbeat- extra heartbeats out of the normal rhythm

Question 20

What is haemoglobin?

Answer 20

A large protein that has 4 polypeptide chains each with a haem group each with an iron molecule. It has a high affinity for oxygen and can carry up to four molecules

Question 21

Write the equation for the formation of oxyhaemoglobin?

Answer 21

Hb + 4O2 –> HbO8

Question 22

How does partial pressure of oxygen affect haemoglobin

Answer 22

Haemoglobins affinity for oxygen increases the higher the partial pressure of oxygen

Question 23

Explain the s shape of the dissociation curve

Answer 23

The graph is s shaped because when the first oxygen molecule combines it alters its shape to make it easier for other molecules to join but as it becomes more saturated it is harder for more oxygen molecules to join

Question 24

Why do fetuses have different haemoglobin

Answer 24

The fetus gets its blood from the mothers placenta at which point the blood is at low saturation for the fetus to get enough oxygen to survive its haemoglobin must have a higher affinity for oxygen

Question 25

How does carbon dioxide affect haemoglobin ?

Answer 25

Haemoglobin gives up its oxygen more readily at higher partial pressures of carbon dioxide

1) CO2 produced diffuses into red blood cells where it reacts with water to form carbonic acid
2) The carbonic acid dissociates to form hydrogen and hydrogen carbonate ions
3) The hydrogen ions cause the haemoglobin to unload its oxygen and load the hydrogen ions forming haemoglobinic acid
4) The hydrogen carbonate ions diffuse into the plasma and chloride ions diffuse into the blood to compensate- chloride shift
5) when the blood reaches the lungs there is now loe pCO2, the hydrogen and hydrogen carbonate ions reform CO2 and are breathed out

Question 26

What is the bohr effect?

Answer 26

As CO2 levels increase the dissociation curve shifts right