3.1.2 - Transport in Animals Flashcards
Why do multicellular animals need a transport system?
As they get larger their surface area to volume ratio decreases so diffusion is no longer sufficient to provide for their needs and metabolic rate.
What are open circulatory systems?
- Found in insects and arthropods
- The transport medium haemolymph is pumped directly into the open body cavity and there are very few transport vessels
- Haemolymph is pumped at low pressure and transports food and nitrogenous waste but not gases
What are closed circulatory systems?
- Found in all vertebrates such as fish and mammals and some invertebrates
- The transport medium blood is pumped from the heart through vessels
- Blood transports oxygen and carbon dioxide
What are single circulatory systems?
- The blood passes through the heart once per cycle
- Found in fish
- The blood is pumped by the heart through the gills to the body and back to the heart
What are double circulatory systems?
- The blood passes through the heart twice per cycle
- Found in birds and most mammals
- One circuit of blood vessels carries blood from the heart to the lungs for gas exchange
- The second circuit of blood vessels carries blood from the heart to the rest of the body to deliver oxygen and nutrients and to collect waste
What is the function of arteries?
Carry blood away from the heart
What is the structure of arteries?
- No valves
- Thicker walls than veins to help maintain blood pressure
- Collagen outer layer to provide structural support
- Thicker elastic layer than veins to help maintain blood pressure. The walls can stretch and recoil in response to the heart beat
- Thicker smooth muscle layer than veins so that constriction and dilation can occur to control the volume of blood
What are arterioles?
Connectors between arteries and capillaries
What is the structure of arterioles?
- No valves
- Thinner walls than arteries as pressure is slightly lower
- Thinner collagen layer than arteries
- Thinner elastic layer than arteries as pressure is lower
- Thicker smooth muscle layer than arteries to help restrict blood flow into capillaries
What is the function of capillaries?
Responsible for the exchange of oxygen, nutrients, and waste products between the blood and the cells
What is the structure of capillaries?
- No valves
- No smooth muscular wall
- No elastic layer
- No collagen layer
- One cell thick consisting of only a lining layer which provides a short diffusion distance for exchanging materials between the blood and cells
What are venules?
Connectors between capillaries and veins
What is the structure of venules?
- Have valves
- A thin layer of smooth muscle
- No elastic layer
- No collagen layer
- Very thin wall
What is the function of veins?
Carry blood to the heart
What is the structure of veins?
- Have valves
- Relatively thin smooth muscle layer so it cannot control the blood flow
- Relatively thinner than arteries as pressure is much lower
- Contains lots of collagen
- Thin walls as the pressure is much lower than arteries so there is low risk of the vessel bursting. The thinness means the vessels are easily flattened which helps the flow of blood up to the heart
What is hydrostatic pressure?
The pressure from fluid on the walls of the capillary usually forcing plasma out of the circulatory system
What is oncotic pressure?
Osmotic pressure from proteins in the blood plasma that draws water into the circulatory system
How is tissue fluid formed in the plasma?
At the arterial end there is high hydrostatic pressure due to the smaller diameter as the blood enters from the arterioles to the capillaries. This means there is a net flow of fluid out of the capillary to form tissue fluid
How is tissue fluid reabsorbed?
At the venous end there is low hydrostatic pressure due to the loss of liquid at the arterial end. This means there is a net flow of fluid back into the capillary by osmosis
What happens to the remaining fluid which isn’t reabsorbed?
It is absorbed into the lymphatic system and called lymph. It eventually drains back into the bloodstream near the heart
What is the composition of blood?
- Contains plasma with dissolved glucose, amino acids, mineral ions, hormones and large proteins
- Contains red blood cells, platelets and white blood cells
- Erythrocytes carry oxygen, carbon dioxide and antigens
What is the composition of tissue fluid?
Same as blood but no red blood cells, leucocytes or large proteins
What is the composition of lymph?
Contains less oxygen, glucose and amino acids but more carbon dioxide, fatty acids, lymphocytes and antibodies than blood
What is the function of the pulmonary artery?
Transports deoxygenated blood to the lungs
What is the function of the aorta?
Transports oxygenated blood to the body
What is the function of the pulmonary vein?
Receives oxygenated blood from the lungs
What is the function of the vena cava?
Receives deoxygenated blood from the body
What are the 3 stages of the cardiac cycle?
- Diastole
- Atrial systole
- Ventricular systole
What happens during diastole?
- The atria and ventricular muscles are relaxed
- This is when blood will enter the atria via the vena cava and pulmonary vein
- The blood flowing into the atria increases the pressure within the atria
What happens during atrial systole?
- The atria muscular walls contract increasing the pressure further which causes the atrioventricular valves to open and blood to flow into the ventricles
- The ventricular muscular walls are relaxed
What happens during ventricular systole?
- The ventricle muscular walls contract increasing the pressure beyond that of the atria which causes the atrioventricular valves to close and the semi lunar valves to open
- The blood is pushed out of the ventricles into the arteries
What is the formula for cardiac output?
Cardiac output = heart rate x stroke volume
What is the cardiac output?
The volume of blood which leaves one ventricle in one minute
What is the heart rate?
Beats of the heart per minute
What is the stroke volume?
The volume of blood that leaves the heart each beat
What does the cardiac muscle is myogenic mean?
The heartbeat originates in the heart muscle
How is the heart action initiated?
The wave of electrical activity is initiated by the sino-atrial node which acts as a pacemaker. Located in the wall of the right atrium it generates a wave of excitation that causes the muscle in the atrial wall to contract
How is the heart action coordinated?
The atrioventricular node in the septum delays the impulse to let the atria contract fully before the ventricles contract
What is the role of the Purkyne tissue?
It distributes the impulse through the walls of the ventricles causing the muscles to contract
What are the stages of the heart action?
- Wave of electrical activity spreads out from the sino-atrial node
- Wave spreads across both atria causing them to contract and reaches the atrioventricular node
- Atrioventricular node conveys wave of electrical activity down the bundle of His in the septum between the ventricles along the Purkyne fibres and then releases it at the apex causing the ventricles to contract
What are the five features of a normal trace on an ECG?
P - contraction of the atrial muscles
QRS - contraction of the ventricle muscles
T - relaxation of the ventricle muscles
What is tachycardia?
When the heart is beating at over 100bpm
What is bradycardia?
When the heart is beating at less than 60bpm
What is fibrillation?
When there is an irregular rhythm of the heart
What is ectopic heartbeat?
When there are additional heartbeats that are not in rhythm
What is the structure of haemoglobin?
It is a protein with quaternary structure and it is made up of four polypeptide chains which each have a prosthetic haem group
How is carbon dioxide transported in the blood?
- Dissolved in the blood plasma as haemoglobinic acid
- In the cytoplasm of red blood cells in the form of hydrogen carbonate ions
- Can react reversibly with amino acids in haemoglobin to form haemoglobinic acid
How is carbon dioxide transported in red blood cells?
- It forms carbonic acid by reacting with water catalysed by carbonic anhydrase
- The carbonic acid dissociates into hydrogen carbonate ions and hydrogen ions
- The hydrogen carbonate ions diffuse out of the red blood cell into the plasma
- This leaves the inside of the red blood cell with a deficit of negative ions causing chloride ions to diffuse into the red blood cell from the plasma
- This exchange of ions is known as chloride shift
What is cooperative binding?
At the alveoli when the first oxygen molecule binds to the first haem group the haemoglobin changes shape which makes it easier to bind to a further three oxygen molecules
When does oxygen dissociate?
Oxygen dissociates from haemoglobin at the tissues when there is a low partial pressure of oxygen in the tisues
What happens to haemoglobin’s affinity for oxygen at different partial pressures of oxygen?
- At high partial pressures of oxygen haemoglobin has a higher affinity for oxygen so has high saturation levels.
- At low partial pressures of oxygen haemoglobin has a lower affinity for oxygen so has lower saturation levels
What is the Bohr effect?
When a high carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right. The affinity for oxygen decreases because the acidic carbon dioxide changes the shape of haemoglobin.
How is foetal haemoglobin different to adult haemoglobin?
It has a higher affinity for oxygen so that the foetus is able to receive enough oxygen from the maternal blood via the placenta
