3.1.2 - Transport in animals Flashcards
Give 4 reasons why specialist transport systems are needed
- Metabolic demands of most animals is high
- SA:V decreases as animal size increases so diffusion distances increase whilst SA available becomes relatively smaller
- Molecules need to be moved large distances
- Waste products of metabolism need to be removed from cells and transported to excretory systems
As an organism gets larger what happens to the diffusion distance ?
It gets larger
Why does a greater level of activity in an organism increase demand for glucose and oxygen ?
- More activity requires more energy
- More energy requires more aerobic respiration
- Which requires more reactants (oxygen and glucose)
Why does a greater volume of an organism mean a greater demand ?
- Greater volume means greater number of cells
- Each cell requires energy
- So demand for energy/glucose/oxygen increases
Define mass flow
The movement of fluids down a pressure or concentration gradient, from high to low
Define circulatory system
The transport system of an organism
Define open circulatory system
A transport system with a heart but with few vessels to contain the transport medium
Define closed circulatory system
The transport medium is enclosed in vessels and does not come into contact with the cells of the body
Define haemolymph
The blood like fluid contained in insects
Define single circulatory system
A circulatory system where the blood flows through the heart once during a complete circuit of the body
Define double circulatory system
A circulatory system where the blood flows through the heart twice during a complete circuit of the body
Define pulmonary circulation
The part of the circulatory system which carries deoxygenated blood away from the right ventricle of the heart to the lungs and returns oxygenated blood to the left atrium
Define systemic circulation
The part of the circulatory system which carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart
Give examples of organisms with a single closed circulatory system
- Fish
- Annelid worms
Give examples of organisms with a double closed circulatory system
- Birds
- Most mammals
Give an example of an organism with an open circulatory system
Insects
Why are fish able to be highly active despite having a single closed circulatory system ?
- The countercurrent exchange mechanism means they can take up a lot of O2 from water
- Their body weight is supported by the water
Why are single closed circulatory systems not very efficient ?
Blood pressure drops considerably so blood flows slowly back to the heart
Why are double closed circulatory systems very efficient ?
- Each circuit passes through only one capillary network this maintains relatively high blood pressure
- So fast flow of blood back to the heart is maintained
What are the general features of circulatory systems ?
- Fluid to transport dissolved gases, nutrients, and waste
- A pumping mechanism to move fluid
- Sometimes vessels to carry the fluid
How are open and closed circulatory systems different ?
- Blood is enclosed in vessels in a closed system but not in an open system
- In open systems, the fluid fills body cavities
- An open system is less efficient
What is an advantage of having an open circulatory system ?
Less vulnerable to pressure
What is an advantage of closed circulatory systems ?
More efficient
What is a disadvantage of open circulatory systems ?
Requires low metabolic rate so does not work for larger animals
What is a disadvantage of closed circulatory systems?
Requires more energy
What is the disadvantage of single circulatory systems ?
They are less efficient
What are the differences between single and double circulatory systems ?
- Blood goes through the heart once in one complete circuit in a single system and twice in a double system
- Single system has two sets of capillaries while double system has one set of capillaries
- Double system maintains a higher pressure than a single system
What is plasma?
Liquid component of blood
What is the function of plasma?
Transports dissolved substances
What does plasma transport ?
e.g glucose, amino acids, mineral ions, hormones, albumin and fibrinogens
Why is albumin important ?
It helps to maintain oncotic pressure
Why are fibrinogens important ?
They are involved in blood clotting
What are platelets?
Small fragments of cells
Which is the function of platelets?
Start the process of blood clotting
What triggers blood clotting?
- A rough surface
- Exposure to air
What are the functions of blood as a whole?
- Transport of oxygen and carbon dioxide to and from respiring cells
- Transport hormones
- Transport nitrogenous waste products from cells to excretory organs
- Transporting cells and antibodies involved in the immune response
- Helps to maintain steady body temperature
- Acts as a buffer to minimise pH change
What are the 3 layers of arteries called?
- Tunica intima
- Tunica media
- Tunica externa
What makes up the tunica intima of the arteries?
Squamous epithelial cells
What makes up the tunica media of the arteries?
Smooth muscle and elastic fibres
What makes up the tunica externa of the arteries?
Collagen
Why is the tunica intmia of arteries smooth?
So blood flows over it easily
What do the elastic fibres in the tunica media of the arteries do?
Stretch to receive blood and recoil between contractions of the heart which helps to maintain pressure and even out blood flow
They allow for elastic recoil
What is the function of collagen in the tunica externa of arteries?
Prevents blood vessels from bursting under high pressure
What are the functions of the arteries?
Carry oxygenated blood away from the heart apart from the pulmonary artery
What is blood flow into arteries like?
- High pressure
- Pulsatile
- Fast
Why do arteries need to maintain high pressure of the arteries?
So that blood can reach tissues in the body
What does contact of blood with artery walls cause?
- Friction
- Slows blood down
- Evens out pulsatile flow
What is the function of the arterioles?
Regulate the flow of blood into the capillaries
Do arterioles have a higher proportion of smooth muscle than arteries?
Yes
Why do arterioles have a lower proportion of elastin in their walls compared to arteries?
The blood flow isn’t very pulsatile
Why is blood slower in the arterioles?
Due to friction with the vessel walls
How does the slightly wider lumen in arterioles affect pressure?
Reduces it slightly
What is the function of the smooth muscle?
It is neurally stimulated to cause vasoconstriction or vasodilation which controls the flow of blood into capillaries
What is the function of capillaries?
To exchange substances between the blood and tissues
What is the advantage of capillaries being one cell thick?
Gives a short diffusion pathway
What is the advantage of blood flow being slow through capillaries?
Gives a longer time for the exchange of substances
Why is the blood pressure low through the capillaries?
- The pressure is spread across many blood vessels
- Prevents them from bursting
What is blood flow like through capillaries?
Smooth, low pressure, slow
What is the function of venules?
To link capillaries to veins
What are the walls of venules mostly made of?
Collagen
Why do venules have a thin tunica media?
They flow at low pressures so don’t require muscle or elastic fibres as they don’t have to withstand high pressures
Why do veins have a wide lumen?
To accommodate the large volume of blood carried
What is the blood flow through veins like?
Very slow, low pressure and smooth
Why are valves present in veins?
They prevent back flow
What 3 mechanisms aid blood flow back to the heart?
- Skeletal muscles contract/relax and pushblood through veins as they lie near the surface
- Valves prevent back flow
- Breathing mechanism causes negative pressure in the thorax so pulls blood towards the heart
What is tissue fluid?
A liquid produced from the circulatory system which contains dissolved nutrients
What is the function of tissue fluid?
- Transports substances to the tissues and returns waste products of the cells back to the circulatory system
- Allows the cells to take up the products needed
Give 3 examples of substances found dissolved in tissue fluid
- Glucose
- Amino Acids
- Oxygen
- Carbon Dioxide
What happens to excess tissue fluid?
- Drains into lymph vessels
- Some tissue fluid returns to capillaries
What is lymph ?
Tissue fluid that is collected in the lymph system
What is the lymphatic system?
System that contains drainage vessels for lymphatic fluids
What are the functions of lymph nodes?
Involved in immune response and contain lymphocytes
What is the function of pores in capillaries?
- Allows tissue fluid to leave capillaries
- Do not allow blood cells or large proteins out of the blood
Why does tissue fluid move in and out of capillaries?
Due to opposing blood pressures
What is hydrostatic pressure?
The pressure created by water in an enclosed system
What is oncotic pressure?
The pressure caused by water moving into the blood by osmosis as a result of plasma proteins
Why does hydrostatic pressure fall as blood and tissue fluid move through the capillaries?
Due to increased distance from the heart and branching of the arterioles into many capillaries
Why does oncotic pressure stay the same throughout the capillaries?
The plasma proteins in the blood which generate the pressure are too large to fit through capillary pores
In what direction does tissue fluid move at the arteriole end of the capillary?
Out of the capillary
Why is tissue fluid forced out of the capillary at the arteriole end ?
The oncotic pressure is greater than the hydrostatic pressure so tissue fluid is drawn into the blood
Outline the movement of blood through the heart
- vena cava into right atrium
- through tricuspid AV valve
- right ventricle
- semi-lunar valves
- pulmonary artery
- lungs
- pulmonary veins
- left atrium
- bicuspid AV valve
- left ventricle
- semi-lunar valve
- aorta
What is the heart made out of ?
Cardiac muscle
How is cardiac muscle described?
Myogenic
What does myogenic mean ?
Heart muscle has its own intrinsic rhythm
What is the difference between cardiac muscle and skeletal muscle ?
Cardiac muscle does not get fatigued and need to rest
Why is the heart described as a double pump ?
- Blood is pumped through the heart twice
- First time deoxygenated blood is pumped to lungs
- Second time oxygenated blood is pumped to the body
What is the function of the coronary arteries ?
Supply the heart muscle with oxygen and glucose in order to keep it contracting and relaxing all the time
What is the function of pericardial membranes ?
They help to prevent the heart from swelling with blood, due to increased pressures
Is the wall of the left ventricle thicker than the right?
Yes
Why is the wall of the right ventricle thinner than the wall of the left ventricle ?
- The right side only has to pump blood to the lungs which are close to the heart
- Right side must only overcome resistance of the pulmonary circulation
Why is the wall of the left ventricle thicker than the wall of the right ventricle?
- The left side must provide sufficient force to overcome the resistance of the aorta and arterial systems of the whole body
- Left side must move the blood under pressure to all extremities of the body
As the atrium fills with blood what happens to atrial pressure?
It increases
As ventricular pressure increases, what happens to aortic pressure and why ?
- It increases
- Blood flows into the aorta at high pressure
What is the sino-atrial node? and what is its function?
Region of the heart that initiates a wave of excitation that triggers the contraction of the heart
What is the sino-atrial node also known as?
The pacemaker region
What is the atrio-ventricular node? and what is its function?
It stimulates the ventricles to contract after a slight delay
Why does the atrio-ventricular node impose a slight delay?
To ensure atrial contraction is complete first before contracting blood out after
What is the bundle of His?
- Conducting tissue made of purkyne fibres that passes through the septum
What are Purkyne fibres?
Tissue that conducts the wave of excitation to the bottom (apex) of the heart
What is the function of the septum?
Prevents the mixing of oxygenated and deoxygenated blood
What is the function of the valves in the heart?
Prevents back flow of the blood and so ensures efficient movement of blood
What is the function of tendinous cords ?
They help to prevent prolapse of the valves
Why does hydrostatic pressure of blood drop as blood moves away from the heart?
- Divides into smaller vessels
- Vessels have larger total cross sectional area
- Loss of plasma from the capillaries
Outline the movement of electrical signals through the heart
- Wave of depolarisation begins at the SAN which causes atria to contract
- Wave of depolarisation travels to AVN
- AVN imposes slight delay before stimulating the bundle of His
- AVN stimulates the bundle of His
- Bundle of His splits into two branches and conducts the wave of excitation to the apex
- At the apex, the purkyne fibres spread out through ventricular walls
- Spread of excitation triggers the contraction of ventricles
Why can the wave of depolarisation not travel directly to the ventricles ?
There is a ring of non-conducting tissue between the atria and ventricles
Why is it important that the AVN imposes a slight delay?
- Ensures the atria contract before the ventricles
- All atrial blood empties into ventricles before the ventricles contract
Why do ventricles contract from the apex up?
- Blood needs to be moved upwards
- It ensures that there is complete emptying of ventricles
What is the effect on the heart of the sympathetic nerve releasing noradrenaline?
Heart rate increases
What is the effect on the heart of the vagus nerve releasing acetyl choline?
Heart rate decreases
What does ECG stand for?
Electrocardiogram
What does an ECG show?
Shows the spread of electrical excitation through the heart as a way of recording what happens when it contracts
What is the x axis on an ECG?
Time
What is the y axis on an ECG?
Electrical potential (mV)
What does the P wave on an ECG show?
Depolarisation of atria in response to SAN triggering the atria to contract
What does the QRS wave on an ECG show?
- Ventricular systole
- Wave of depolarisation in ventricle walls
- Ventricles contract
- AV valve closes
What does the T wave on an ECG show?
Ventricles relax
How can heart rate be measured using an ECG?
Heart rate is the time between the peaks (R)
What is the cardiac cycle ?
The sequence of events that occur in the heart during one heartbeat
What occurs during atrial diastole?
- Both atria and ventricles are relaxed
- Blood enters the right atrium via the vena cava and the left atrium via the pulmonary vein
- Atria fill with blood
- AV valves are closed
- Pressure in atria increases as they fill with blood
- Semi-lunar valves are closed
What occurs during atrial systole?
- Atria contract
- Contract almost simultaneously
- Atrial pressure higher than ventricular pressure so AV valves open
- The semi-lunar valves are still closed
What occurs during ventricular systole?
- Ventricles fill with blood and contract
- AV valves close so blood isn’t forced back into the atria
- Semilunar valves open with forces blood into the aorta/pulmonary artery
What occurs during ventricular diastole?
- pressure in the aorta and pulmonary artery increases
- ventricles relaxed
- Semi-lunar valves close to prevent backflow
What causes the heart sounds?
Blood hitting the heart valves
What causes the ‘lub’ sound?
Blood hitting AV valves as ventricles contract
What causes the ‘dub’ sound ?
Backflow of blood hitting the semilunar valves
When does the ‘lub’ sound happen?
During ventricular systole
When does the ‘dub’ sound happen ?
During ventricular diastole
What happens when ventricular pressure is greater than atrial pressure?
AV valve closes as systole is entered
Why do the semilunar valves open?
Because pressure in the ventricles is higher than the pressure in the aorta
Why do the semilunar valves close?
The pressure in the aorta is greater than in the ventricles
Why do AV valves open ?
Atrial pressure is greater than ventricular pressure
Why does ventricular pressure increase after the closing of the AV valve?
Due to the thicker ventricle wall
As the ventricles contract what happens to the ventricular volume and pressure?
- Volume decreases
- Pressure increases
What is arrhythmia?
An abnormal rhythm of the heart
What is bradycardia?
The heart beats more slowly than normal rhythm, less than 60bpm
What is Tachycardia?
A fast heart rate (over 100bpm)
What is ectopic heartbeart?
Extra heartbeats that are out of the normal rhythm
What is atrial fibrilation?
Abnormal rhythm of the heart when the atria beat very fast and incompletely
How are ECGs measured?
- Electrodes stuck on skin
- Measure electrical differences in the skin
- Signal fed into machine which produces an ECG
