Module 3.1.2 - Transport in animals Flashcards
What can single-celled organisms and multicellular organisms diffuse across?
single-celled - An outer membrane
multicellular - relatively big and have low SA to V ratio and a higher metabolic rate
What does the circulatory system do?
Uses blood to carry glucose and oxygen around the body, also carries hormones, antibodies and waste products
Why do multicellular organisms have a double circulatory system?
Very active so cells are respiring very quickly so need constant supply of glucose and oxygen, CO2 needs removing from cells quickly
What circulatory system do fish have?
Single
What circulatory system do mammals have?
Double
What is a single circulatory system?
- blood only passes through the heart once each complete circuit of the body
- fish are less active so only have a single C.System
What is a double circulatory system?
- blood passes through the heart twice for each complete circuit of the body
- mammals are more active so have a double C.System
What is a closed circulatory system?
All vertebrates (fish and mammals) have a closed system as blood is enclosed inside blood vessels
What is an open circulatory system?
Some invertebrates (insects) have an open circulatory system as blood isn’t enclosed in blood vessels all the time, instead it flows freely through the body cavity
What are types of blood vessels?
- arteries
- arterioles
- capillaries
- venules
- veins
What are arteries?
- carry blood away from the heart to rest of the body
- walls are thick and muscular, elastic tissue to stretch and recoil as heart beats to help maintain high pressure
- inner lining (endothelium) is folded, allowing artery to expand/maintain high pressure
- all arteries carry oxygenated blood except pulmonary arteries which take deoxygenated blood to lungs
- lumen is the space in the centre of the arteries
What are arterioles?
- arteries branch into arterioles which are much smaller than arteries
- have a layer of smooth muscle like arteries, but have less elastic tissue
- smooth muscle allows them to expand or contract, controlling amount of blood flowing to tissue
What are capillaries?
- arteries branch into capillaries, smallest of the blood vessels
- substances like glucose and oxygen, are exchanged between cells and capillaries, adapted for efficient diffusion
What are venules?
- capillaries connect to venules, which have thin walls that contain some muscle cells
- venules join together to form veins
What are veins?
- takes blood back to the heart under low pressure
- wider lumen than arteries have, with very little elastic or muscle tissue as less pressure
- contain valves to stop blood flowing backwards
- blood flows through the veins helped by contractions of body muscles surrounding them
- all veins carry deoxygenated blood except the pulmonary veins, which carry oxygenated blood to the heart
What is tissue fluid?
- surrounds cells in tissues
- made from substances that leave the blood plasma
- cells take in oxygen and nutrients from tissue fluid and release metabolic waste into it
- capillary bed (network of capillaries in an area of tissue) has substances move out of capillaries, into tissue fluid by pressure filtration
What is pressure filtration?
- hydrostatic pressure inside capillaries is greater than HP in tissue fluid at start of capillary bed, nearest arteries
- difference in HP forces fluid out capillaries and into spaces around cells, forming tissue fluid
- as fluid leaves, HP reduces in capillaries so HP is much lower at end of capillary bed that’s nearest to venules
- as water leaves capillaries, conc of plasma proteins in capillaries increases and water potential decreases
- plasma proteins in capillaries generate a form of pressure called oncotic pressure so at venule end of capillary bed, high oncotic pressure at low water potential
- because water potential in capillaries is lower than water potential in tissue fluid, some water re-enters capillaries from tissue fluid at venule end by osmosis
What are lymph vessels?
- not all tissue fluid re-enters capillaries at vein end of capillary bed, some tissue fluid is left over
- this extra fluid gets returned to blood through lymphatic system
- smallest lymph vessels are lymph capillaries
- excess tissue fluid passes into lymph vessels and is called lymph once inside
- valves in lymph vessels stop lymph going backwards
- lymph gradually moves towards main lymph vessels in thorax (chest cavity)
What is the lymphatic system?
Drainage system made up of lymph vessels
What does the heart consist of?
2 muscular pumps, right and left
What type of blood does each side of the heart pump?
Right - deoxygenated blood to the lungs
Left - oxygenated blood to the rest of the body
What do the Atrioventricular (AV) valves link?
The atria to the ventricles
What do the semi-lunar (SL) valves link?
The ventricles to the pulmonary artery and aorta
What is the purpose of the atrioventricular and semi-lunar valves?
To stop blood flowing the wrong way
What does the valves being open or closed depend on?
Relative pressure of the heart chambers as they only open one-way
What happens if there is high pressure behind a valve?
The valve is forced open
What happens if there is high pressure in front of a valve?
The valve is forces shut
What type of direction does blood flow have through the valves?
Unidirectional - only flows in one direction
What is the cardiac cycle?
- ongoing sequence of contractions and relaxations of the atria and ventricles
- volumes of atria and ventricles changes as they contract and relax, which alters the pressure
- this causes valves to open and close, which moves blood through the heart
How many stages are in the cardiac cycle?
3
What happens in stage 1 of the cardiac cycle?
- ventricles are relaxed and atria contracts which decreases volume of chambers, increasing pressure inside the chambers
- this pushes blood into ventricles through the atrioventricular valves
- there’s a slight increase in ventricular pressure and chamber column as the ventricles receive the ejected blood from the contracting atria
What happens in stage 2 of the cardiac cycle?
- atria relax and ventricles contract which decreases volume and increases pressure
- pressure becomes higher in ventricles than the atria, which forces the AV valves to shut to prevent backflow
- the pressure in the ventricles is also higher than then in the aorta and pulmonary artery, which forces open the SL valves and blood is forced out into these arteries
What happens in stage 3 of the cardiac cycle?
- ventricles and atria both relax
- higher pressure in pulmonary artery and aorta closes the SL valves to prevent backflow into the ventricles
- blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein
- this starts to increase pressure in the atria
- as ventricles continue to relax, their pressure falls bellow the pressure of atria and so AV valves open
- this allows blood to flow passively (without being pushed by atrial contraction) into the ventricles from the atria
- the atria contract and stage 1 starts again
What is cardiac output?
Volume of blood pumped by the heart per minute (cm3 min-1)
How do you calculate cardiac output?
Heart Rate x Stroke Volume
How is a heartbeat controlled?
- cardiac muscles can contract and relax without receiving signals from nerves, pattern of contractions controls a regular heartbeat
- starts in Sino-atrial node which is in wall of right atrium, set rhythm of heartbeat by sending regular waves of electrical activity over atrial walls
- causes right and left atria to contract at same time
- band of nonconducting collagen tissue prevents waves of electrical activity from being passed directly from atria to ventricle
- instead these waves are transferred from SAN to AV node
What is AVN responsible for?
passing waves of electrical activity to bundle of His
slight delay before AVN reacts to make sure ventricles contract after atria have emptied
What is the bundle of His?
Group of muscle fibres responsible for conducing waves of electrical activity to finer muscle fibres in right and left ventricle walls, called Purkyne tissue
What is Purkyne tissue?
carries waves of electrical activity into muscular walls of right and left ventricles, causing them to contract simultaneously from bottom up
What are electrocardiographs (ECGs)?
- machine that records electrical activity of the heart
- heart muscle depolarises (loses electrical charge) when it contracts and repolarises when it relaxes
- ECG records changes in electrical charge using electrodes placed on chest
- trace produced by an ECG is called an electrocardiogram
What is a P wave caused by?
Contraction of atria, main peak of heartbeat, together with dips at either side is called QRS complex, caused by contraction of ventricles
What are T waves caused by?
Relaxation of ventricles, height of wave indicated how much electrical charge is passing through the heart
What is a bradycardia heartbeat?
heart beats too slow, around 50 bpm
What is a tachycardia heartbeat?
Heat beats too fast, around 120 bpm at rest
How do you calculate heart rate (bpm)?
60 / time taken for 1 heartbeat
What are 4 types of heart problems?
- tachycardia
- bradycardia
- ectopic
- fibrillation
What is an ectopic heartbeat?
Extra heartbeat that interrupts regular rhythm
- can be caused by earlier contraction of atria or ventricles
What is a fibrillation heartbeat?
Irregular heartbeat
- atria or ventricles completely lose their rhythm and stop contracting properly
- can result in chest pain, fainting, lack of pulse or death
What is haemoglobin?
- found in red blood cells
- carries oxygen around the body
- large quaternary protein (4 polypeptide chains)
- each chain has a haem group containing iron
What gives haemoglobin its red colour?
The iron in the haem group
What does affinity for oxygen mean?
Tendency for molecule to bind with oxygen, varies depending on conditions (one is partial pressure of oxygen) and measure of oxygen conc
How many oxygens can haemoglobin carry
4
How is oxyhaemoglobin formed?
Oxygen joins to iron in haemoglobin in lungs, called association or loading
When oxygen leaves oxyhaemoglobin, what is it called?
Unloading or dissociation
What happens to partial pressure when there’s a greater conc of dissolved oxygen cells?
pO2 is higher
What happens with pO2 increases?
Haemoglobin affinity for oxygen also increases
What type of partial pressure do alveoli have?
High - cells use up oxygen when they respire so low pO2
What happens when oxygen is loaded on and unloaded off haemoglobin?
Oxyhaemoglobin is formed, pO2 increases
Oxyhaemoglobin unloads oxygen when pO2 decreases
What do red blood cells deliver to respiring tissues?
Oxyhaemoglobin - unloads oxygen
Haemoglobin then returns to lungs to pick up more oxygen
What is a dissociation curve?
Shows how saturated haemoglobin is with O2 at any given partial pressure
- affinity of haemoglobin for oxygen affects how saturated haemoglobin is
- shape alters when haemoglobin combines with O2 molecules to help them join
- the more saturated it becomes, more harder it is
What would happen if fetal haemoglobin had same affinity of oxygen as adult haemoglobin?
Its blood wouldn’t be saturated enough, fetus would die
What is fetal haemoglobin?
Haemoglobin in a fetus
- higher affinity of oxygen than adult haemoglobin
- transported across placenta, low pO2 so adult haemoglobin will unload its oxygen
What is pCO2?
Partial pressure of carbon dioxide
What does pCO2 affect?
Oxygen unloading
What happens to shape of curve when cells respire?
Shifts right as CO2 is produced which increases pCO2 and rate of O2 unloading
What is the Bohr effect?
Saturation of blood with O2 i lower for a given pO2 meaning more O2 is released
- most CO2 is released into red blood cells
- reacts with H2O to form carbonic acid
- rest of CO2 binds with haemoglobin in lungs
- carbonic acid unloads to give H+ and HCO3-
