3.1.2 Flashcards
Why do animals need specialised transport systems?
- The metabolic demands of most multicellular organisms are high
- SA:V ratio is very small
- Molecules like hormones or enzymes may be produced in one place but needed in another
- Waste products of metabolism need to be removed
What are the common features of a circulatory system?
- They have a liquid transport medium that circulates around the system
- They have vessels that carry the transport medium
- They have a pumping mechanism to move the fluid around the system
What is a mass transport system?
When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
What is an open circulatory system?
A circulatory system with very few vessels to contain the transport medium. It is pumped from the heart into the body cavity of the animal. The open body cavity is called the haemocoel. Here, the transport medium is under low pressure, and comes into direct contact with the tissues and the cells. This is where exchange takes place betwee the transport medium and the cells
What is the blood in insects called?
Haemolymph
In what type of animals are open circulatory systems mainly found in?
Invertebrates, including most insects and some molluscs
What does haemolymph carry?
Food and nitrogenous wastes
What is a closed circulatory system?
A circulatory system in which the blood is enclosed in blood vessels and does not directly come into contact with the cells of the body. The heart pumps blood around the body under pressure and relatively quickly
What is a single circulatory system?
A circulatory system in which the blood flows through the heart once during each circulation
Which organisms have single closed circulatory systems?
Fish and annelid worms
What is a double circulatory system?
A circulatory system in which the blood flows through the heart twice during each circulation
What are the three main components of blood vessels?
Elastic fibres
Smooth muscle
Collagen
What is the function of elastic fibres?
Stretch and recoil, providing vessel walls with flexibility, and allowing the vessels to withstand the force of the blood pumped out of the heart and stretch. This evens out the surges of blood pumped from the heart, giving a continuous flow.
What is the function of smooth muscle?
Contracts or relaxes, which changes the size of the lumen
What is the function of collagen?
Provide structural support to maintain the shape and volume of the vessel
What are the functions of the blood?
Transport of oxygen, carbon dioxide, digested food, nitrogenous waste, hormones, food molecules, platelets, and white blood cells and antibodies
What is positive cooperativity?
The process by which haemoglobin changes shape each time one oxygen molecule binds to a haem group, making it easier for the next oxygen molecule to bind.
What is the shape of an oxygen dissociation curve?
Sigmoidal
How does CO2 impact the binding of oxygen with haemoglobin
As the partial pressure of CO2 increases, haemoglobin gives up oxygen more easily. This change is known as the Bohr effect.
Why is the Bohr effect important?
In active tissues with a high pCO2, haemoglobin gives up O2 more easily
In the lungs where pCO2 is low, oxygen binds to haemoglobin easily
How does foetal haemoglobin compare to adult haemoglobin?
Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin as the foetus is solely reliant on the oxygen provided to it via the placenta
How is CO2 transported?
- 5% is carried dissolved in the plasma
- 10-20% is combined with the amino groups in haemoglobin to form carbaminohaemoglobin
- 75-85% is converted into HCO3- in the cytoplasm of red blood cells
What is the equation for the formation of carbonic acid?
CO2 + H2O -> H2CO3
What catalyses the formation of carbonic acid?
Carbonic anhydrase
Where do the HCO3- ions go after being formed?
They move out of the erythrocytes into the plasma by diffusion, and Cl- ions move into the erythrocytes, maintaining the electrical balance of the cell. This is called chloride shift
How is the conversion of CO2 to HCO3- useful?
The erythrocytes maintain a steep concentration gradient for CO2 to diffuse from the respiring tissues into the erythrocytes
Where does the wave of excitation in the heart begin?
The sinoatrial node, and it causes the atria to contract and so the heartbeat starts. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles
Why is there a slight delay imposed by the AVN?
It is to allow the ventricles to completely fill
Why does the bundle of His travel to the apex of the heart?
This is to allow more efficient emptying of the ventricles, opposing gravity
What is an ECG?
An electrocardiogram, and it detects tiny electrical differences in the skin, which result from the electrical activity of the heart
What is tachycardia?
When the heartbeat is very fast, over 100 bpm.
What is bradycardia?
When the heart rate slows down to below 60 bpm
What is an ectopic heartbeat?
An extra heartbeat out of the normal rhythm
What is atrial fibrillation?
Rapid contraction of the atria (up to 400 times per minute) but they do not contract properly, and only some of the impulses are passed on to the ventricles, which contract much less often. This leads to inefficient pumping of the blood.
