Chapter 14 - Transport in humans Flashcards
Describe the need for a transport system in humans
- 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
State where the heart is situated
Behind the sternum, between the lungs in the thoracic cavity
Name the major part of the heart which is made up of cardiac muscle
Myocardium
Name the inner lining of the heart
Endothelium
Name the membrane by which the heart is covered
Pericardium
Name the part of the heart by which the two atria are seperated
Interatrial septum
State the function of the pulmonary vein
Brings oxygenated blood from the lungs to the left atrium
Name the two veins which brings blood to the right atrium
- Vena cava inferior
- Vena cava superior
Name the artery which takes oxygenated blood from the heart
Aorta
Name the part of the heart by which the two ventricles are seperated
Interventricular septum
Name the valve between the right atrium and right ventricle
Tricuspid valve
Name the valve between the left atrium and left ventricle
Bicuspid valve
Name the blood vessels which supply the heart with oxygen and nutrients
Coronary arteries/veins
How to describe the functions of the different parts of the heart
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.
Name the three stages of the cardiac cycle
- Atrial systole
- Ventricular systole
- Diastole
Describe what happens during atrial systole
- 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
Describe what happens during ventricular systole
- 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
Describe what happens during diastole
- 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
Explain the difference in thickness of muscle walls in the heart
- 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
Describe what is meant by the term “myogenic”, with reference to the heart
It means that the heart beat is initiated from inside the heart muscle itself rather than by a nervous impulse from outside the heart
State the position and function of the sino-atrial node
- 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
State the position and function of the atrio-ventricular node
- 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
State the function of the Purkyne fibres
- 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.
How long does one cardiac cycle last? Also state the average heartrate of a human
- 0.8 seconds
- 75 beats per minute
Name the effects of exercise on the heart beat
- 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
List the likely causes of heart diseases
- Eating a high colestrol diet
- Obesity
- Stress
- Smoking
- Not taking regular exercise
- Genetic predisposition
Explain how atherosclerosis can cause a heart attack
- 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)
Explain how heart diseases can be prevented
- Follow a low cholestrol diet
- Not being obese
- Reduce stress levels
- Do not smoke and reduce alcohol intake
- Take regular exercise
What is the blood pressure inside an artery?
High blood pressure (10-16 kPa)
Describe the flow of blood inside an artery
Blood moves in pulses and flows rapidly
What are small arteries called?
Arterioles
Name the two arteries which do not transport oxygenated blood
- Pulmonary artery
- Umbilical artery
Name the adaptations of arteries
- 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
State the pressure at which blood flows inside veins
1 kPa
Describe how the blood flows inside veins
Slowly with no pulses
Name the two veins which carry oxygenated blood
- Pulmonary vein
- Umbilical vein
Describe the adaptations of veins
- 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
Name the adaptations of capillaries
- 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
Describe the double circulatory system
- 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
State the advantage of double circulation
Oxygenated and deoxygenated blood is kept seperate
