1Describe the vascularisation of an earthworm.
Closed circulatory system, with dorsal vessels bringing blood, then going through psuedohearts, and then goign back through ventral vessels.
2Describe the circulatory system of insects
Open circulatory system, dorsal tube shaped heart
3What's an closed circulatory system?
Where blood moves in blood vessels
4What's an open circulatory system?
Blood bathes the tissues directly while being held in haemocoel
5What's single circulation?
Blood goes through the heart once and around the body
6What's double circulation?
Blood is pumped through the heart twice
7Do fish have closed circulatory systems or open circulatory systems?
closed
8Do fish have a single or double circulatory system?
single
9What's pulmonary circulation?
Takes blood to the lungs to be oxygenated
10What's systemic circulation?
Takes oxygenated blood around the body and brings deoxygenated blood back
11Why is a double circulatory system more efficient than a single circulatory system?
The heart pumps the blood twice so a higher pressure can be maintained and the blood travels more quickly to the organs. In a single, blood loses pressure as it passes through the gills and travels relatively slowly to the organs.
12How does blood in veins above the heart return to the heart?
Via gravity
13How does blood in veins below the heart return to the heart?
They have valves to prevent back flow of blood, and recoil of elastic fibres in the tunica media push blood up
14How are capillaries adapted?
The wall is only one cell thick allowing a short diffusion pathway, the walls are permeable to allow diffusion and carry blood close to cells
15What's the function of the endothelium in blood vessels?
Smooth lining which reduces friction to minimise resistance of blood flow
16What's the function of the tunica externa in blood vessels?
Contains collagen fibres which resist over-stretching.
17Is the tricuspid valve located on the right or left side of the heart?
right
18Is the bicuspid valve located on the right or left side of the heart?
left
19What do myogenic contractions mean?
The cardiac tissue contracts and relaxes rhythmically on its own, never tiring.
20What events occur during atrial systole?
Atrium walls contract which reduces volume of the atria, causing blood to be pushed through the atrioventricular valves into the ventricles. The ventricles are in diastole.
21What events occur during ventricular systole?
The atria relax. The atrioventricular valves are shut close, contracting and pushing blood through the semi-lunar valves through to the pulmonary vein and aorta.
22Outline the steps of the electrical heartbeat mechanism.
1. Wave of electrical stimulation arises from the Sino-Atrial Node (SAN) over both atria.
2. It then encounters the atrioventricular node (AVN), which provides a slight delay in transmission of the electrical wave.
3. The AVN passes the excitation to the bundle of his, then down to the apex of the heart
4. The excitation then goes through the purkinje fibres into the ventricle walls
5. These impulses cause the ventricles to contract.
23What is the P wave of an ECG?
Atrial depolarization, initiated by the SA node, causes the P wave
24What is the QRS complex of an ECG?
ventricular depolarization and atrial repolarization
25What is the PR interval of an ECG?
The time taken for an excitation to spread from the SAN to the AVN
26What is the sino-atrial node (SAN)?
It is a cluster of specialised cardiac cells, which acts as a pacemaker
27Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?
Friction causes a loss of energy, slowing down transport of blood
28How are red blood cells adapted to carry oxygen?
- bi-concave shape gives a big surface area for absorbing oxygen. it also helps them pass smoothly through capillaries to reach body cells
- packed with haemoglobin which absorbs oxygen
- they have no nucleus to leave even more room for haemoglobin
29How many molecules of oxygen can a single haemoglobin molecule molecule bind to?
4 oxygen molecules
30Why are oxygen dissociation curves S-shaped? (Sigmoid)
Initially, oxygen struggles to join with iron atoms to form oxyhemoglobin. But then when it finally joins, it distorts the shape of the protein molecule, making it easier for the other oxygen molecules to join.
31Explain why the oxygen dissociation curves shifts to the right the Bohr shift?
Partial pressure of CO2 becomes higher, due to respiration.
Conditions become more acidic and shape of haemoglobin changes slightly.
Haemoglobin has a lower affinity for O2, and it unloads more easily.
32Why is the oxygen dissociation curve for fetal haemoglobin shifted to the left?
Red blood cells flow close to placenta (where the baby gets oxygen from whilst in the womb). 2 out of 4 polypeptide chains of haemoglobin differ from adult haemoglobin which makes it easier for oxygen to bind to: increasing the oxygen affinity to shift it to the left.
33Explain why oxygen dissociation curve for llama shifts to the left.
Llama lives at higher altitudes so their haemoglobin needs a higher affinity for oxygen, when there is a lower partial pressure of oxygen.
34Outline the reaction of carbon dioxide in red blood cells.
1. CO2 diffuses into the red blood cell.
2. Carbonic anhydrase catalysts CO2 reacts with H20 to form carbonic acid
3. Carbonic acid dissociates into H+ and HCO3-
4. HCO3- diffuses out of red blood cell. To balance the outflow of the negative ions, chloride ions diffuse into the red blood cell to maintain electrochemical neutrality. This is called the chloride shift.
5. H+ ions cause oxyhemoglobin to dissociate into haemoglobinic acid and oxygen. The oxygen molecules diffuse out of red blood cell.