Transport In Animails Flashcards
Why do multi-cellular organisms require a transport system ?
- Large Size (Small surface area to volume ratio), High metabolic rates
- High demand for oxygen, so need a strong transport system to ensure a constant supply to respiring tissues
What is a open circulatory system ?
A transport system with a heart but with few vessels to contain the transport medium
What is a closed circulatory system ?
The transport medium is enclosed in vessels and does not come into contact with the cells of the body
What is a single transport system ?
A circulatory system where the blood flows through the heart once during a complete circuit of the body
What is a double circulatory system ?
A circulatory system where the blood flows through the heart twice during a complete circuit of the body
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
Relate the structure of arteries to their function
Thick, Muscular walls to handle high pressure. Elastic tissue allows recoil to prevent pressure surges. Narrow lumen to maintain pressure
Relate the structure of veins to their function
Thin walls due to lower pressure. Require valves to ensure blood doesn’t flow backwards. Have less muscular and elastic tissues as they do not have to control blood flow
Relate the structure of capillaries to their function
- Walls are only one cell thick; short diffusion pathway
- Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
- Numerous and highly branched, providing a large surface area
Relate the structure of arterioles and venues to their function
- Branch off arteries and veins in order to feed blood into capillaries
- Smaller than arteries and veins so that change in pressure is more gradual as blood passes through increasingly small vessels
What is tissue fluid ?
A watery substance containing glucose, amino acids, oxygen and other nutrients. It supplies these to the cells, while also removing any waste materials
What is hydrostatic pressure ?
The pressure created by water in an enclosed system
What is oncotic pressure ?
The pressure caused by the tendency of water to move into blood by osmosis as result of plasma proteins
What pressure influence formation of tissue fluid ?
Hydrostatic pressure = Higher at arterial end of capillary than venous end
Oncotic Pressure = Changing water potential of the capillaries as water moves out, induced by proteins in plasma
How is tissue fluid formed ?
As blood is pumped through increasingly small vessel, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells
How does tissue fluid differ from blood and lymph ?
- Tissue fluid is formed from blood, but does not contain red blood cells, platelets, and various other solutes usually present in blood
- After tissue has bathes cells it becomes lymph, and therefore this contains less oxygen and nutrients and more waste products
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
- mitral value
- left atrium
- left ventricle
- aortic valve
- aorta
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remains closed
Describe what happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles
Describe what happens during ventricular systole
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent back flow, and opening the semilunar valves. Blood flows into the arteries
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
What does myogenic mean ?
The hearts contraction is initiated from within the muscle itself, rather than by nerve impulses
Explain how the heart contracts
- wave of depolarisation begins at SAN (Sino-atrial node) causes atria to contract
- wave of depolarisation travels to AVN (Atrial-ventricular node)
- AVN (Atrial-ventricular node) imposes slight delay before stimulating the bundle of His
- AVN (Atrial-ventricular node) stimulates bundle of His
- Bundle of His splits into two branches and conducts the wave of excitation to the apex
- at apex Purkyne fibres spread out through ventricular walls
- spread of excitation triggers the contraction of 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 can the wave of depolarisation not travel directly to the ventricles ?
There is a ring of non-conducting tissue between the atria and ventricles
What is an electrocardiogram (ECG) ?
A graph showing the amount of electrical activity in the heart during the cardiac cycle
What does the P wave on an ECG show ?
Depolarisation of atria in response to SAN triggering the atria to contract
Refer To GoodNotes
What does the QRS wave on an ECG show ?
- Ventricular systole
- wave of depolarisation in ventricle walls
- ventricles contract
- AV valve closes
Refer to GoodNotes
What does the T wave on an ECG show ?
-ventricles relax
Refer To GoodNotes
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
Describe types of abnormal activity that may be seen on an ECG
- Tachycardia = Fast heartbreak (Over 100bpm)
- Bradycardia = Slow heartbeat (Under 60bpm)
- Fibrillation = Irregular, fast heartbeat
- Ectopic = Early or extra heartbeats
Describe the role of haemoglobin
Present in red blood cells. Oxygen molecules Bind to the heam groups and are carried around the body, then released where they are needed in respiring tissues
What occurs to the Hb once the first molecule of O2 has been taken up by it ?
The Hb changes shape
Why does Hb change shape once the first molecule of O2 has been taken up ?
- enables Hb to take up the 2nd O2 more quickly
- the 3rd O2 quicker still
- 4th O2 even more quickly
- allows a concentration gradient to be maintained as no free oxygen is dissolved into the blood
What is positive cooperactivity ?
- Hb which changes shape once 1st molecule of O2 is taken up
- enables 2nd, 3rd, 4th O2 molecules to be taken up more quickly
What do oxyhemoglobin dissociation curves show ?
Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (in kPa). Curved further to the left show the haemoglobin has a higher affinity for oxygen
Describe the Bohr effect
As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from heamoglobin .
Explain the role of carbonic anhydrase in the Bohr effect
- Carbonic anhydrase is present in red blood cells
- Converts carbon dioxide to carbonic acid, which dissociated to produce H+ ions
- These combine with the haemoglobin to form haemoglobinic acid
- Encourages oxygen to dissociate from haemoglobin
Why does foetal haemoglobin have a higher affinity for O2 ?
- a foetus obtains its O2 from maternal haemoglobin
- in the placenta maternal Hb releases the O2 which diffuses into the foetal bloodstream
- at the pO2 at which maternal Hb releases O2 which diffuses into the foetal bloodstream
- pO2 at which maternal Hb releases O2 the foetal Hb is able to pick up
- Foetal Hb becomes 95% saturated
How is CO2 transported in red blood cells ?
- CO2 diffuses into red blood cells
- Enzyme carbonic anhydrase catalyses the reaction of CO2 and water to produce carbonic acid which dissociates into HCO3- ions and H+
- HCO3- diffuse into plasma
- H+ buffered by Hb to form Haemoglobic acid, triggering the release of 4 molecules of O2
Why is the foetal haemoglobin curve to the left of the adult haemoglobin curve?
- placenta has low pO2
- adult Hb will release O2
- foetal Hb is still able to take up some O2 in placenta
- foetal Hb has a higher affinity for O2 than adult Hb
What are the 3 ways transport of CO2 occurs ?
- in blood plasma
- attaches to amine group of haemoglobin
- transported as hydrogen carbonate in red blood cells
Draw a diagram of the heart
Refer to GoodNotes
What is the chloride shift ?
- Movement of chloride ions into red blood cells, occurring when hydrogen carbonate Iona are formed
- Negative HCO3- are transported out of the red blood cells
- Prevent an electrical imbalance, negatively charged chloride ions are transported into red blood cells
- If did not occur blood cells wold become positively charged as a result of a buildup of hydrogen ions
