Chapter 14 - Transport in humans

Question 1

Describe the need for a transport system in humans

Answer 1

• Humans have large bodies, with cells deep inside the body
• All these regions need materials
• Diffusion will be too slow to supply all these regions with materials

Question 2

State where the heart is situated

Answer 2

Behind the sternum, between the lungs in the thoracic cavity

Question 3

Name the major part of the heart which is made up of cardiac muscle

Answer 3

Myocardium

Question 4

Name the inner lining of the heart

Answer 4

Endothelium

Question 5

Name the membrane by which the heart is covered

Answer 5

Pericardium

Question 6

Name the part of the heart by which the two atria are seperated

Answer 6

Interatrial septum

Question 7

State the function of the pulmonary vein

Answer 7

Brings oxygenated blood from the lungs to the left atrium

Question 8

Name the two veins which brings blood to the right atrium

Answer 8

• Vena cava inferior

- Vena cava superior

Question 9

Name the artery which takes oxygenated blood from the heart

Answer 9

Aorta

Question 10

Name the part of the heart by which the two ventricles are seperated

Answer 10

Interventricular septum

Question 11

Name the valve between the right atrium and right ventricle

Answer 11

Tricuspid valve

Question 12

Name the valve between the left atrium and left ventricle

Answer 12

Bicuspid valve

Question 13

Name the blood vessels which supply the heart with oxygen and nutrients

Answer 13

Coronary arteries/veins

Question 14

How to describe the functions of the different parts of the heart

Answer 14

Now that you know the main structure of the heart, you will be able to infer their functions. Always remember to refer to the parts, type of blood and the valves where necessary.

Question 15

Name the three stages of the cardiac cycle

Answer 15

• Atrial systole
• Ventricular systole
• Diastole

Question 16

Describe what happens during atrial systole

Answer 16

• Muscles in the walls of both atria contract (0.15 seconds)
• Volume in the atria decrease and the pressure in the blood increases
• Valves in veins stop blood from returning to the vena cavae and the pulmonary vein
• Atrio-ventricular valves (bi- and tricuspid valves) open
• Blood passes into the ventricles

Question 17

Describe what happens during ventricular systole

Answer 17

• Muscles in the walls of the ventricles contract
• Volume inside the ventricles decreases and the pressure in the blood increases
• Atrio-ventricular valves close and prevent backflow of blood
• Semi-lunar valves (aortic and pulmonic) open
• Blood enters the pulmonary artery and aorta

Question 18

Describe what happens during diastole

Answer 18

• Muscles in the walls of the atria and ventricles relax (0.4 seconds)
• Volume inside the atria and ventricles increases, and the pressure decreases
• Blood flows into both atria
• Semi-lunar valves close and prevent backflow of blood into arteries
• Pressure in atria and ventricles force all valves to close

Question 19

Explain the difference in thickness of muscle walls in the heart

Answer 19

• The atria ony have to pump blood to the ventricles over a short distance with little pressure. Thin walls (2mm) with less cardiac muscle is required.
• The left ventricle has to pump blood to the entire body over a longer distance with greater pressure, and requires very thick walls (16mm) of cardiac muscle.
• The right ventricle has to pump blood to the lungs over a shorter distance with less pressure, and therefore requires only thick walls (9mm) of cardiac muscle

Question 20

Describe what is meant by the term “myogenic”, with reference to the heart

Answer 20

It means that the heart beat is initiated from inside the heart muscle itself rather than by a nervous impulse from outside the heart

Question 21

State the position and function of the sino-atrial node

Answer 21

• Known as the pacemaker, and is the initial stimulus for the heart to beat
• Located in the wall of the right atrium near where the vena cavae enter
• Sends a wave of excitations which spread across both atria, causing them to contract simultaneously
• The impulse stops between the atria and ventricles at the atrio-ventricular node
• This node delays the impulse for 0.1 seconds in order for atrial systole to complete

Question 22

State the position and function of the atrio-ventricular node

Answer 22

• Situated between the atria and ventricles
• Joined by long muscle fibres known as Purkyne fibres which make up the bundle of his
• This node receives the stimulus from the SAN, and sends a wave of excitation down the Purkyne fibres

Question 23

State the function of the Purkyne fibres

Answer 23

• Conducts the wave of excitation down the inter-ventricular septum to the apex of the heart. The wave then spreads upwards through the walls of the heart. This causes ventricular systole from the apex upwards.

Question 24

How long does one cardiac cycle last? Also state the average heartrate of a human

Answer 24

• 0.8 seconds

- 75 beats per minute

Question 25

Name the effects of exercise on the heart beat

Answer 25

- Heart rate will increase - More oxygen pumped to respiring cells and reaches active muscles - Faster respiration will occur - Faster respiration results in more energy will be released for the muscle cells - More carbon dioxide will be pumped to the lungs for faster excretion thereof

Question 26

List the likely causes of heart diseases

Answer 26

- Eating a high colestrol diet - Obesity - Stress - Smoking - Not taking regular exercise - Genetic predisposition

Question 27

Explain how atherosclerosis can cause a heart attack

Answer 27

- Atherosclerosis causes the hardening of arteries - A build up of cholestrol (fatty diposits) occurs in the linings of coronary arteries - Causes the narrowing of arteries which obstructs blood flow to the heart muscles - Eventually a blockage in the arteries form - Less or no blood can flow through the artery - The heart muscle does not recieve sufficient glucose and oxygen - Anaerobic respiration will occur due to lack of oxygen\ - No removal of lactic acid and carbon dioxide occurs - The cardiac muscle contracts less powerfully or stops - This results in a heart attack (cardiac arrest)

Question 28

Explain how heart diseases can be prevented

Answer 28

- Follow a low cholestrol diet - Not being obese - Reduce stress levels - Do not smoke and reduce alcohol intake - Take regular exercise

Question 29

What is the blood pressure inside an artery?

Answer 29

High blood pressure (10-16 kPa)

Question 30

Describe the flow of blood inside an artery

Answer 30

Blood moves in pulses and flows rapidly

Question 31

What are small arteries called?

Answer 31

Arterioles

Question 32

Name the two arteries which do not transport oxygenated blood

Answer 32

- Pulmonary artery | - Umbilical artery

Question 33

Name the adaptations of arteries

Answer 33

- Thick musclular walls to withstand pressure and prevent bursting - Single layer of endothelium to reduce friction - Thick layer of elastic smooth muscles and elastic tissues to stretch outwards with the pressure of the heartbeat - Smaller lumen to maintain pressure - The beginning of arteries connected to the heart have semi-lunar valves to prevent backflow of blood into the heart - Arteries have no valves because blood can not blow back due to the high pressure

Question 34

State the pressure at which blood flows inside veins

Answer 34

1 kPa

Question 35

Describe how the blood flows inside veins

Answer 35

Slowly with no pulses

Question 36

Name the two veins which carry oxygenated blood

Answer 36

- Pulmonary vein | - Umbilical vein

Question 37

Describe the adaptations of veins

Answer 37

- Thinner walls (low pressure) - Smooth layer of endothelium to reduce pressure - Less elastic fibres as there is no need for stretching - Tough walls with collagen to prevent bursting - One way valves to prevent the backflow of blood - Large lumen allows blood to flow with minimum resistance - Thin walls allow skeletal muscles to squeeze veins and cause blood to move forward

Question 38

Name the adaptations of capillaries

Answer 38

- Numerous to carry different matrerials to and from tissues - Very thin walls of one cell layer to facilitate easy exchange of different materials to and from blood - Gaps between cells of the wall for exchange to and from blood, for white blood cells to squeeze out and tissue fluid to leak out - High hydrostatic pressure inside so most components of plasma can filtrate outside the capillary. This is then known as tissue fluid

Question 39

Describe the double circulatory system

Answer 39

- Blood flows twice through the heart during one full circulation of the body - Pulmonary circulation carries blood to and from the lungs - Systemic circulation carries blood to and from the body

Question 40

State the advantage of double circulation

Answer 40

Oxygenated and deoxygenated blood is kept seperate