Transport in Animals Flashcards
Describe the vascular system of insects.
- Open circulatory system.
- Dorsal-tube shaped heart
- Respiratory gases not carried in blood.
Open circulatory system
The transport medium pumped by the heart is not contained within vessels, but moves freely. Transport fluid comes into direct contact with the cells.
Describe the vascular system of earthworms.
- Vascularisation.
- Closed circulatory system.
- Respiratory gases carried in blood.
Close circulatory system
The blood is pumped by the heart is contained within the blood vessels. Blood does not come into direct contact with the cells.
Advantages of a closed circulatory system.
- Blood pressure can be maintained.
- Blood supply to different organs can vary.
- Lower volumes of transport fluid required.
Single circulatory system
A circulatory system in which the blood travels one circuit. Blood flows through the heart and is pumped around the body before returning to the heart.
Double circulatory system
A circulatory system in which the blood flows through the heart twice in two circuits. Blood is pumped from the heart to the lungs before returning to the heart. It is then pumped around the body, after which it returns to the heart again.
Advantages of a double circulatory system.
- Maintains blood pressure around the whole body.
- Uptake of oxygen is more efficient.
- Delivery of oxygen and nutrients is more efficient.
- Blood pressure can differ in pulmonary and systemic circuits.
What are the names of the two circuits that blood enters the heart through?
Pulmonary circuit and systemic circuit.
Name the four chambers of the mammalian heart.
- Left atrium
- Right atrium
- Left ventricle
- Right ventricle
Outline the pathway of blood around the body.
Pulmonary vein, Left atrium, Left ventricle,
Aorta, Body, Vena Cava, Right atrium, Right ventricle, Pulmonary artery, Lungs.
Atrioventricular valves (AV)
Are found between the atria and ventricles and they prevent the back flow of blood from the ventricles into the atria.
There are two types; Bicuspid (left side) and Tricuspid (right side).
Semi-lunar valves
Are found between the ventricles and arteries and they prevent the backflow of blood into ventricles.
List the 5 types of blood vessels.
Arteries, arterioles, capillaries, venules and veins.
Outline the pathways of blood through the blood vessels.
Heart, arteries, arterioles, capillaries, venules, veins and heart.
Function of arteries
Carry blood away from the heart to the tissues, under high pressure.
Relate the structure of arteries in relation to their function
- Thick, muscular walls to handle high pressure without tearing.
- Elastic tissue allows recoil to prevent pressure surges.
- Narrow lumen to maintain pressure.
Function of veins
Carry blood towards the heart under low pressure.
Relate the structure of veins related to their function
- Thin walls due to lower pressure.
- Require valves to ensure blood doesn’t flow backwards.
- Have less muscular and elastic tissue as they dont have to control the blood flow.
Function of capillaries
Form a large network through the tissues of the body and connect the arterioles to the venules.
Relate the structure of capillaries to their function
- Walls only one cell thick therefore short diffusion pathway.
- Very narrow, so permeated tissues and red blood cells can lie flat against the wall, reducing the diffusion distance.
- Numerous and highly branched, proving a large surface area.
Function of the arterioles
Connect the arteries and the capillaries.
Function of venules
Connect the capillaries and the veins.
Relate the structure of arterioles and venules in relation to their function
- Branch off arteries and veins in order to feed blood into capillaries.
- Smaller than arteries and veins so that the change in pressure is more gradual as blood flows to the capillaries.
Cardiac cycle
The sequence of events involved in one complete contraction and relaxation of the heart.
Diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the AV valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so the semi lunar valves remain closed.
Atrial systole
The atria contract, pushing any remaining blood into the ventricles. AV valves pushed fully open.
Ventricular systole
The ventricles contact, the pressure in the ventricles increases, closing the AV valves to prevent back flow and opening the SL valves. Blood flows into the arteries.
Why is the cardiac muscle myogenic?
It initiates its own contraction without outside stimulation from nervous impulses.
Describe how the heart contracts.
- SAN initiates and spreads impulse across the atria, so they contract.
- AVN receives, delays, and then conveys the impulse down the Bundle of His.
- Impulse travels into the Purkinje fibres which branch across the ventricles, so they contract from the bottom up.
Electrocardiogram (ECG)
A graph showing the electrical activity in the heart during the cardiac cycle.
Describe patterns displayed on a typical ECG
- P wave (depolarisation of atria during atrial systole).
- QRS wave (depolarisation of ventricles during ventricular systole).
- T wave (repolarisation of ventricles during ventricular diastole).
Erythrocytes
The type of blood cell that is unucleated and biconcave. Carries haemoglobin which enables the transport of oxygen and carbon dioxide too and from the tissues.
Plasma
The main component of the blood (yellow liquid) that carries red blood cells.
Contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste.
It also distributes heat.
Role of haemoglobin
Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body, then released where they are needed in respiring tissues.
How does the partial pressure of oxygen affecting oxygen-haemoglobin binding?
Haemoglobin has variable affinity for oxygen depending on the partial pressure of oxygen:
- At high partial pressures, oxygen associates to form oxyhaemoglobin.
- At low partial pressures, oxygen dissociates to form deoxyhaemoglobin.
What do oxyhaemoglobin dissociation curves show?
- The saturation of haemoglobin with oxygen (%), plotted against partial pressure of oxygen (%).
- Curves further to the left show the haemoglobin has a high affinity for oxygen.
Explain the shape of oxyhaemoglobin dissociation curves
Sigmoidal curve (S-shaped):
- When the first oxygen molecule binds, it changes the tertiary structure of haemoglobin so that it is easier for the second and third molecule to bind.
- Third molecule changes the tertiary structure of haemoglobin so that it is more difficult for the fourth molecule to bind.
How does fetal haemoglobin differ from adult haemoglobin?
Has a higher affinity for oxygen than adult haemoglobin due to the presense of two different subunits that allow oxygen to bind more readily. This enables the fetus to obtain oxygen from the mother’s blood.
How is carbon dioxide carried from respiring cells to the lungs?
- Transported in aqueous solution in the plasma.
- As hydrogen carbonate ions in the plasma.
- Carried as carboaminohaemoglobin in the blood.
Chloride shift
Process by which chloride ions move into haemoglobin in exchange for hydrogen carbonate ions which diffuse out of the haemoglobin. It is a one-to-one exchange and maintains the electrochemical equilibrium.
Carbonic anhydrase
Catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid.
Bohr effect
The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases.
Explain the role of carbonic anhydrase in the Bohr effect
- Carbonic anhydrase is present in red blood cells and catalyses the reaction of carbon dioxide and water to form carbonic acid, which dissociates to produce hydrogen ions.
- Hydrogen ions combine with the haemoglobin to form haemoglobic acid which encourages oxygen to dissociate from haemoglobin.
Tissue fluid
The fluid that surrounds the cells of animals. It has the same composition as plasma but does not contain red blood cells of plasma proteins.
Describe the different pressures involved in forming 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 the proteins in the plasma).
How is tissue fluid formed?
As blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells,
Why does blood pressure fall along the capillary?
Because of friction and there is a lower volume of blood.
What happens at the venous end of the capillary?
Oncotic pressure is greater than hydrostatic pressure and so fluid moves down its water gradient back into the capillaries.
