Circulatory system Flashcards
What is the cardiac cycle?
The sequence of events in one heart beat
What are the stages that occur during the cardiac cycle?
Diastole
Atrial systole
Ventricular systole
What happens during diastole?
Atria and ventricles are relaxing
Blood flows into both the atria and ventricles
Atrioventricular valves are open
Equal pressure in the atria and the ventricles
What happens during atrial systole?
Heart beat starts as atria contracts
Right and left atria simultaneously contract
Right and left ventricles fill up
Pressure increases in ventricles and decreases in aorta
When ventricles are full, they contract and cause the atrioventricular valves to close
What happens during ventricular systole?
Ventricles contract increasing pressure
Semilunar valves open
Pressure in aorta and pulmonary artery increase
After blood has been pushed out, the ventricle walls relax
When do aortic pressure and ventricular pressure equal eachother?
When the semilunar valves open and close
When does atrial pressure equal ventricular pressure?
When the atrioventricular valve closes and opens
What materials are transported in the blood
Oxygen and Carbon dioxide
What materials are transported in the plasma
Hormones Heat Excretory products Digestive products Mineral salts Antibodies
Where is metabolic heat produced and transported to in the body?
From the liver to the muscles
Where does the renal artery transport blood to?
The kidneys
How is the diffusion rate sped up in the capillaries?
High surface area to volume ration
Walls are only one cell thick
What is the tip of the heart called?
The apex
The process of a heartbeat
Impulse starts in the sinoatrial node as an electrical impulse
The impulse travels down the atrial walls causing muscle contractions
The impulse is stopped by a fibrous non-conducting layer apart from at the atrioventricular node
There is a slight time delay before the electrical impulse travels from the AVN down the septum through purkyne tissue to the apexn
A wave of contractions occur from the apex upwards along the ventricular walls
How thick are the atrial walls and why?
They are quite thin as they only need to pump the blood to the ventricles
How thick is the right ventricle wall and why?
Relatively thick as they need to pump the blood to the lungs
How thick is the wall of the left ventricle and why?
Extremely thick as it needs to pump blood around the whole body to respiring cells
What does the P wave represent on a electrocardiogram?
Atrial depolarisation
What does the QRS complex represent on a electrocardiogram?
Ventricular depolarisation
What does the T wave represent on a electrocardiogram?
Ventricular repolarisation
What is an electrocardiogram?
a record of the voltage changes which occur during the cardiac cycle
Why is there a short delay between the excitation of the atria and excitation of the ventricles?
Not all the blood has passed into the right ventricle
To allow the atrium to contract fully
So ventricles do not contract too early
What are pressure levels like during diastole?
Low in arteries, artia and ventricles
What are pressure levels like during atrial systole?
Rises in both atria and ventricles
Stays low in arteries
What are pressure levels like during ventricular systole?
Atrial pressure falls
Ventricular pressure rises steeply then suddenly falls as the semilunar valve opens
Artery pressure is high
Progression of the cardiac cycle ( before oxygenation)
Deoxygenated blood arrvies in the blood
Blood fills the right atrium
The right atrium contracts
Blood is forced into the right ventricle
The right ventricle contracts
Blood is prevented from flowing back by tricuspid valves
Blood leaves heart through pulmonary artery
Progression of the cardiac cycle ( after oxygenation)
Blood is oxygenated in lungs Oxygenated blood travels along pulmonary veins Blood fills the left atrium The left atrium contracts Blood is forced into the left ventricles Blood is prevented from flowing back by bicuspid valves The left ventricle contracts Blood leaves heart through aorta
Characteristics of an open circulatory system
Blood is not always in the vessels
Insects have a muscular tube that moves blood around the body by peristalsis
Blood enters the heart in insects via pores called ostia
Only exists if the organism is small
In insects blood doesn’t transport the respiratory gases
Movement of blood is slow
Characteristics of a closed circulatory system
Blood always stays within vessels
Tissue fluid bathes the cells while blood transports repiratory gases
High pressure
What type of muscle is found in the wall of the heart chambers?
Cardiac muscle
What is transport?
The movement of oxygen, nutrients, hormones, waste and heat around the body
What are the three main factors affecting the need for a transport system?
Size
Surface area to volume ratio
Level of activity
How does size affect the need for a transport system?
Once an animal has several layers of cells, nutrients and gases cannot penetrate to the deepest layer of cells
How does surface area to volume ratio affect the need for a transport system?
A small surface area to volume ratio will result in not enough oxygen and nutrients reaching the cells so a transport system is required
How do levels of activity affect the need for a transport system?
If an animal is very active, more oxygen and nutrients have to be supplied to the respiring cells
If an animal also needs to keep themselves warm, they will need even more energy
What are the components of an effective transport system?
A medium to carry solutes
A pump to create pressure gradients
Exchange surfaces
What are the components for an efficient transport system?
Tubes or vessels to carry the blood
Two circuits; one to pick up oxygen and the other to deliver
What is a double circulatory system?
A transport system in which blood travels twice through the heart for each complete circulation of the body
Characteristics of a single circulatory system
Low blood pressure
Blood does not flow very quickly
The rate at which solutes are delivered to repairing tissues are slow
Characteristics of a double circulatory system
The heart can increase the pressure of blood increase the velocity
Blood can be carried at higher pressures
However, blood pressure cannot rise too high or vessel walls will be damaged
Give a description of the heart
The heart is a musclar pump that creates pressure to propel the blood through the arteries and around the body
Which ventricle pumps oxygenated blood?
The left ventricle
What is the purpose of the pulmonary artery and vein?
To transport deoxygenated blood to the lungs so haemoglobin can be loaded with oxygen
The pulmonary vein then transports the oxygenated blood back to the left atrium
What are the tendinous cords for?
These are string like extensions that attach to valves to prevent valves from turning inside out
Why is cardiac muscle described as myogenic?
The muscle can contract and relax voluntarily even when it is not connected to the body
What is a closed circulatory system?
A circulatory system where the blood always remains within the vessels
What is an open circulatory system?
A circulatory system where the blood is not always in vessels
How open circulation achieved in insects?
A long muscular pumping organ helps to pump the blood around the body
Blood enters the heart through pores called ostia
The blood is pumped towards the head via peristalsis
What are the characteristics of an artery?
Narrow lumen
Thick wall containing collagen for structural strength
Walls contain elastic tissue to allow recoil that maintains pressure
Walls contain smooth muscle that narrows lumen to maintain presure
Endothelium is folded and can unfold when artery streches
What are the characteristcs of a vein?
Large lumen for easy flow
Walls contain collagen, elastic tissue and smooth muscle but is relatively thin
Have valves to prevent backflow of blood
What are the characteristics of capillaries?
Walls consist of one layer of squamous endothelial cells
Very narrow lumen to press blood cells against capillary walls
What is lymph?
Excess tissue fluid that is absorbed into the lymphatic system
How is tissue fluid formed?
At the arteriol end of the capillary, there is high hydrostatic pressure so blood fluid is pushed out of the capillary through small gaps
What forces act upon tissue fluid?
Hydrostatic pressure
Osmosis
How does tissue fluid return to the blood?
At the veniol end, there is a net inflow of tissue fluid as hydrostatic pressure is low and water potential witin the vessel is low
What do you have to watch out for when saying blood transports nutrients?
There has to be at least one named nutrient or the examiner cannot award the mark
Why does the lymph rejoin at the chest cavity?
Pressure is lowest just before blood enters the heart so it is easier for the lymph to enter
What is the main difference between lymph and tissue fluid?
Lymph contains lymphocytes that are prodcued in the lymph nodes
What are the lymph nodes for?
The lymph nodes filter bacteria and foreign material so the lymphocytes can then engulf and digest them
What is the difference between filtration and diffusion?
In diffusion, a concentration gradient must be present, however in filtration, there does not need to be a concentration gradient
Why does haemoglobin have an affinity for oxygen?
The haem groups on haemoblogin have Fe2+ ions that can attract both oxygen and carbon dioxide
What is dissociation?
When oxyhaemoglobin releases oxygen for respiration
What is partial pressure/ oxygen tension?
The amount of oxygen that is measured by the relative pressure that contributes to a mixture of gases
Why does haemoglobin not take up oxygen very readily at low pO2?
The haem groups that attract the oxygen are in the centre of the molecule so it is harder for the oxygen molecules to reach the haem groups
What is the conformational change?
The slight change in shape accompanied by the first oxygen molecule attaching to a haem group
Why can haemoglobin take up the second and third oxygen molecule more readily?
The conformational change makes it easier for oxygen molecules to attach to the haem groups
Why does the oxyhaemoglobin dissociation curve level off near the end?
The fourth haemoglobin molecule is hard to associate with, so it is therfore very difficult to reach 100% saturation
How are the mammalian lungs adapted for transporting oxygen?
Partial pressures of oxygen are high enough to fully saturate most haemoglobin molecules
Why does fetal haemoglobin have a higher affinity for oxygen?
Fetal haemoglobin has to pick up oxygen from regions where adult haemoglobin has released oxygen
So it has adapted to picking up oxygen from regions where there is low partial pressure
What is the Bohr effect?
Refers to a change in shape of the oxyWhy is the fourth oxygen molecule hard to associate with?haemoglobin curve when carbon dioxide is present
How is carbon dioxide transported?
5% dissolved in the blood plasma
10% combined directly with haemoglobin to form carbaminohaemoglobin
85% is transported in the form of hydrogencarbonate ions
What are the steps involved in making hydrogencarbonate ions?
Carbon dioxide diffuses into red blood cells to form carbonic acid using carbonic anhydrase as an enzyme
The carbonic acid dissociates to release hydrogen and hydrogencarbonate ions
Hydrogencarbonate ions diffuse out of the red blood cell
How is the charge of the red blood cell maintained?
The hydrogen ions positive charge must be counteracted so chlorine ions move into the red blood cell
This is called the chloride shift
How is pH maintained in the red blood cell?
Hydrogen ions are taken up by haemoglobin to form haemoglobinic acid
Why is haemoglobin referred to as a buffer?
It maintains constant pH
Why does oxyhaemoglobin dissociate more oxygen when partial pressures of carbon dioxide are high?
When there are high concentrations of carbon dioxide, there are more H+ ions present
These H+ ions displaces the oxygen on the haemoglobin so more oxygen is released
An increase in partial pressures of carbon dioxide shift the graph..
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