Transport In Animals❤️ Flashcards
Why do large organisms require vascular systems?
Because diffusion is inefficient over large distances
What is mass transport?
The bulk movement of substances through a transport system using force
Open circulation
- Blood doesn’t flow through vessels
- Flows freely over tissues
- Flow is slow and at low pressure
Closed circulation
- Blood flows through vessels
- Flows at high pressure
- Transported by a respiratory pigment
Single circulation, e.g. in a fish
- Blood passes through heart once in every circuit
- Blood leaves heart under high pressure
- The pressure falls
- Blood flows slowly around the rest of the body before returning to the heart
Double circulation
- Blood passes through the heart twice in every circuit
- Pulmonary circulation - heart and lungs
- Systemic circulation - heart and rest of the body
- Flow is is fast and under high pressure
The flow of blood in a double circulatory system
- The right pumps deoxygenated blood to the lungs
- Oxygenated blood returns to left
- The left pumps oxygenated blood to the tissues
- Deoxygenated blood returns to the right
Pulmonary artery function
Carries deoxygenated blood to lungs from right ventricle
Pulmonary vein function
Carries oxygenated blood from lungs to left atrium
Aorta function
Carries oxygenated blood from left ventricle to rest of the body
Vena cava function
Carries deoxygenated blood from body to right atrium
Atria function
Thin walled chambers which receive blood
Ventricles function
Generate a high pressure of blood to force it over a great distance
Why are the walls of the left ventricle thicker?
More muscular to generate a higher pressure so the blood can travel a greater distance to the extremities of the body
Atrioventricular valves function
Prevent backflow of blood from the ventricles to the atria during ventricular systole
Valve tendons/heart strings function
Keep valves under tension and prevent them from inverting during ventricular systole
Semi lunar valves function
Prevent backflow of blood from the arteries to the ventricles
Open circulation in insects
- Blood is pumped by a dorsal tube shaped heart
* Flows freely over tissues and thought spaces known as haemocoel
Closed circulation in earthworms
- Blood vessels under pressure
- Respiratory gases transported in blood
- Organs not in direct contact with blood
- Blood contains haemoglobin
What is myogenic muscle?
Can initiate its own contractions
Atrial systole
- The atria contract - volume decreases, pressure increases above ventricular pressure
- The AV open
- Blood flows into ventricles down a pressure gradient
Ventricular systole
- The ventricles contract - volume decreases, pressure increases above atrial pressure
- AV shut - produces lub sound
- Ventricular pressure exceeds aortic pressure
- SLV open
- Blood enters the arteries
Diastole
- Atria and ventricles relax - pressure decreases
- Ventricular pressure falls below that of the arteries
- SLV close - produces dub sound
- Low pressure blood in the veins returns to the atria as the atria relax
- Ventricular pressure falls below atrial pressure
- AV open
- Blood enters the ventricles
What is the cardiac cycle?
The sequence of events in one heartbeat
What is the SAN?
- Sino-atrial mode
- Acts as a pacemaker - sets base rate of contraction
- Located in the wall of the right atrium
The cardiac impulse
- An electrical impulse originates in the SAN and spreads across the atria, causing atrial systole
- The impulse is picked up by the AVN in the right atrium
- The impulse is conducted through the bundle of His to the apex of the ventricles
- The impulse travels up through the Purkinje fibres, through the walls of the ventricles causing ventricular systole
- The muscle cells of the ventricles repolarise during diastole
What is the function of an ECG?
- Calculate the heart rate by measuring the time interval between the same points of successive cycles on the trace
- Can be used to help diagnose cardiovascular disease and heart defects
What does the P wave show?
The depolarisation of the atria during atrial systole
What does the PR interval show?
Time for the impulse to spread to the ventricles
What does the QRS wave show?
The spread of depolarisation through the ventricles during ventricular systole
What does the T wave show?
The repolarisation of the ventricles during ventricular diastole
Control of the cardiac activity
- Heart rate can be varied by nerves that originate from the cardiovascular centre
- Impulses can be sent via different neurones which cause involuntary changes to heart rate
- Adrenaline can increase heart rate by causing SAN to discharge at a higher frequency
Arteries
- Transport blood away from heart
- Blood under high pressure
- Rapid blood flow
- Thick layer of smooth muscle
- Many elastic fibres
- Endothelium present
- Collagen fibres in outer layer
- Small lumen
Vein
- Carry blood back to the heart
- Blood under low pressure
- Slow blood flow
- Large lumen
- Thin layer of smooth muscle
- Little elastic tissue
- Valves
- Collagen fibres present in outer layer
- Endothelium present
Capillary
- From arteriole to venule
- Blood flows along pressure gradient
- Pressure falls as blood passes through
- Low pressure - reduced pressure gives more time for exchange
- Slow blood flow
- Small lumen
- No muscle or elastic tissue
- No outer layer
- Endothelium present
Arterioles
Connects arteries to capillaries
Venules
Connect capillaries to veins
Venous return
Blood flow back to the heart is difficult as the blood pressure is low in the veins and may be flowing against gravity
What is venous return aided by?
- Valves - prevent backflow
- Muscles - squeeze against veins
- Suction effect from diastole
- Negative pressure in chest due to ventilation
What is elastic recoil?
The elastic fibres push blood along the artery which produces an even flow of blood
What is the purpose of the elastic fibres in the aorta?
- During ventricular systole they allow the aorta to stretch to accommodate the blood entering
- During diastole they recoil to maintain blood pressure
Why does blood pressure and rate of flow decrease as blood travels further from the heart?
- The increase in total cross sectional area
* Frictional resistance of blood flowing along the blood vessels
Adaptations of capillaries
- Dense network - S.A
- Walls are one cell thick and flattened, small diameter, red blood cells in contact with wall - short diffusion pathway
- Narrow lumen - reduces flow rate, giving more time for diffusion
- Permeable walls - O2 and CO2 cans easily diffuse in and out
- Pores in walls - allows formation of tissue fluid
Plasma
- Made up of water and solutes
* Transport the soluble products of digestion, ions, hormones, antibodies, excretory products and heat
Red blood cells
Responsible for transporting respiratory gases around the body
White blood cells
Involved in protecting the body against infection
Platelets
Involved in blood clotting
The formation of tissue fluid
- Ultrafiltration occurs at the arteriol end of the capillary as the hydrostatic pressure is high - fluid moves out
- The fluid forced out is now tissue fluid and it bathes the cells in essential nutrients
- The hydrostatic pressure falls as fluid is forced out
- Osmosis draws water back in at the venule end as the water potential of the blood is lower than that of the tissue fluid
The lymphatic system
- More fluid leaves the capillaries than is reabsorbed
- Excess fluid drains into lymph capillaries
- The lymph capillaries join to form lymph vessels which return the lymph to the blood via the thoracic duct
- Lymph vessels have valves
The quaternary structure of haemoglobin
- Made up of 4 polypeptide chains, each containing a haem group
- The haem groups contain iron ions which form a loose association with O2 molecules
- Each molecule of haemoglobin can transport 4 molecules of oxygen
Role of haemoglobin
- Loads oxygen in the lungs
* Unloads oxygen at the tissues where it is needed for respiration
What does the oxygen-haemoglobin dissociation curve show?
The relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin with oxygen
Why is the shape of the dissociation curve important?
- S shape - Hb is efficient at loading O2 and can become fully saturated at a lower pO2 than if it was linear
- Hb has a high affinity for O2 at a high pO2 and so loads O2 to form OHb
- Hb has a low affinity for O2 at a low pO2 and so unloads O2
- The steep part means that for a small decrease in pO2, there’ll be a large decrease in % saturation of Hb so more O2 will be unloaded to the tissues for aerobic respiration
Fetal haemoglobin
- Higher affinity for oxygen - at any pO2, % saturation is higher
- Maternal Hb will unload 70% O2 to placenta, fetal Hb will load O2 from placenta to become 80% saturated
- Curve will appear to the left of adult Hb
Dissociation of organisms in low O2 environments
- E.g. llamas and lugworms
- Pigments with higher affinity for O2 - to the left of adult Hb
- Can load more O2 and Hb can be fully saturated at a lower pO2
What is myoglobin?
- The respiratory pigment found in muscle fibres
* Appears to the left of adult Hb
The Bohr effect
- During exercise the rate of respiration increases as the muscles need more ATP
- This produces more CO2 which lowers the pH of the blood
- This causes the dissociation here to shift to the right
- Hb has a lower affinity for O2 - at any pO2, %saturation is lower
What is the advantage of the Bohr effect?
Hb unloads more O2 to the respiring muscle tissues for an increased rate of respiration
Three ways CO2 is transported in the blood
- 5% dissolves directly in plasma
- 10% combined with amino groups in Hb to form carbaminohaemoglobin
- 85% as hydrogen carbonate
What is chloride shift?
- Chloride ions diffuse into the red blood cells from the plasma
- Balance the electrical charge as the diffusion of hydrogen carbonate ions out of the cell left the membrane positively charged
- Maintain electrochemical neutrality
Reversible equation of haemoglobin and oxygen
Hb+4O2 -> oxyHb
3 adaptations of red blood cells
- Bioconcave - more S.A.
- Haemoglobin - high affinity for O2
- No nucleus - more space for Hb
What is the affinity like in Hb in respiring tissues?
Low because it means that Hb dissociates O2 which unloads more O2 for the tissues
What is a pH buffer?
Keeps the pH at an optimum level - Hb acts as a buffer in the RBC
Transport of CO2
- CO2 diffuses into the RBC
- CO2 combines with H2O to form carbonic acid - reaction is catalysed by carbonic anhydrase
- Carbonic acid dissociates into protons(H+) and hydrogen carbonate ions (HCO3-)
- The haemoglobin acts as a buffer as the H+ will lower the pH of the cell
- The oxyHb dissociates, unloading oxygen which diffuses into the tissues
- HCO3- diffuses into the plasma
- Chloride ions diffuse into the RBC from the plasma to obtain electro neutrality
What is the function of the basement membrane surrounding the capillary?
To hold the endothelium and filter through molecules
