Studied by 3 people
Do single-celled organisms need transport systems?
No
Why do multicellular organisms need transport systems? (5)
Harder to supply cells with what they need
Big
Low SA:V
Higher metabolic rate
Active, so larger number of cells respiring, so need a rapid supply of glucose and oxygen
Two types of circulatory systems?
Open and closed
Two types of closed circulatory systems
Single and double
Open circulatory system
When the organism’s blood is free to flow throughout the body cavity and blood is not enclosed in blood vessels
Open circulatory system example
Insects
Closed circulatory system
Blood is restricted to flowing through blood vessels and a pump is required to get the blood to all parts of the body
Closed circulatory system examples
Fish and mammals
Single closed circulatory system
Blood only travels through the heart once every circuit around the body
Double closed circulatory system
Blood travels through the heart twice per circuit
Advantages to double circulatory systems (2)
faster to get oxygenated blood to tissues
greater concentration gradient (between blood and cells)
Artery function
to transport oxygenated blood away from the heart to organs under high pressure
Artery adaptations (3)
Thick layers of muscle
Elastic fibres in artery wall
Folded endothelium
Why do arteries have thick layers of muscle?
high pressure
Why are there elastic fibres in the artery wall?
Allows artery wall to stretch and recoil as the heart beats
Why does the artery have folded endothelium?
Allows the artery to stretch and expand
Arterioles function
To control the direction of blood flow by contracting the arterioles to restrict blood flow and relaxing the arterioles to allow blood to flow
Arteriole adaptations (3)
smaller than arteries
layer of smooth muscle
less elastic tissue than arteries
Why do arterioles have a layer of smooth muscle?
To allow the arteriole to contract and expand and control the amount of blood flowing to tissues
Capillaries function
Allow gas exchange between blood and organs
Capillary adaptations (3)
one cell thick
pass very close to body cells
networks of capillaries
Why are capillaries one cell thick and pass very close to body cells?
for efficient gas exchange due to the short diffusion distance
Why are capillaries found in networks?
To provide a large SA
Vein function
To transfer deoxygenated blood back to the heart under low pressure
Vein adaptations (4)
wide lumen
thin muscle wall
thin elastic tissue
valves
Why do veins have a wide lumen?
Allows blood to flow at low pressure
Why do veins have valves?
To ensure blood flows in one direction/ prevent backflow
Venule function
Collect blood coming out of capillaries
Venule adaptations (2)
Thin walls
walls contain some muscle cells
Tissue fluid
The fluid that surrounds cells in tissues
What is tissue fluid made of?
Substances that leave the blood plasma (e.g. oxygen, water and nutrients)
Hydrostatic pressure
liquid pressure
Oncotic pressure
pressure generated by plasma proteins present in capillaries which lower the water potential
Hydrostatic pressure that the start of the capillary bed (nearest to artery)
hydrostatic pressure inside capillaries > hydrostatic pressure in tissue fluid
Hydrostatic pressure in the end of the capillary nearest to the venules
hydrostatic pressure inside capillaries < hydrostatic pressure in tissue fluid
Lymph vessels
Recycles excess tissue fluid into the bloodstream
Flow of blood through the heart starting with vena cava (12)
Vena cava
Right atrium
Atrioventricular valve
Right ventricle
Semi-lunar valve
Pulmonary artery
Pulmonary vein
Left atrium
Atrioventricular valve
Left ventricle
Semi-lunar valve
Aorta
When is a valve forced open?
higher pressure behind the valve
When is a valve forced shut?
higher pressure in front of valve
Stages of the cardiac cycle (3)
Atrial systole
Ventricular systole
Diastole
Atrial systole
Ventricles relax, atria contract
Ventricular systole
Ventricles contract, atria relax
Diastole
Ventricles relax, atria relax
Cardiac output
Volume of blood pumped per minute
Cardiac output equation
cardiac output = hr x stroke volume
Myogenic
Can contract and relax without receiving signals from nerves
Sino-atrial node (SAN)
Like a pacemaker - sets the rhythm of the heartbeat by sending out regular waves of electricity to atrial walls
What does the SAN cause to contract?
The right and left atria at the same time
Atrioventricular node (AVN)
Passes electrical activity to the bundle of His
Bundle of His
A group of muscle fibres responsible for conducting waves of electrical activity to the Purkyne tissue
Purkyne tissue
Carries waves of electrical activity into muscular walls of the right and left ventricles, causing them to contract simultaneously from the bottom up
Electrocardiographs
Records the electrical activity of the heart by placing electrodes on the person’s chest
What happens when the heart contracts? (relating to charge)
The heart muscle depolarises, so loses electrical charge
What happens when the heart relaxes? (relating to charge)
The heart muscle repolarises, so regains electrical charge
P-wave
Contraction (depolariastion) of the atria
QRS complex
Contraction (depolarisation) of the ventricles
T-wave
Relaxation (repolarisation) of the ventricles
What does the height of a wave on an ECG represent?
How much electrical charge is passing through the heart
What does a bigger wave in an ECG mean?
There’s more electrical charge, so stronger contraction
Tachycardia
Heartbeat too fast
Bradycardia
Heartbeat too slow
Ectopic heartbeat
Early contraction of the atria/ ventricles, so the p-wave comes earlier than it should
Fibrillation
Irregular heartbeat - atria/ventricles lose rhythm and stop contracting properly
How many polypeptide chains is haemoglobin made up of?
Four
What is the prosthetic group in haemoglobin and what does it contain?
The haem group containing iron
How many oxygen molecules can each haemoglobin molecule carry?
four
What does haemoglobin saturation depend on?
The partial pressure of oxygen
What happens to the oxygen when it enters the capillaries at the alveoli in the lungs?
As there is a high partial pressure of oxygen, oxygen loads onto haemoglobin to form oxyhaemoglobin
What happens to oxygen after the cells respire?
The partial pressure of oxygen lowers, so red blood cells deliver oxyhaemoglobin to respiring tissues where it unloads the oxygen
What shape is a dissociation curve?
S-shaped
What does it mean when the dissociation curve is steep?
It is easy for oxygen to join
What does it mean when the dissociation curve is shallow?
It is harder for oxygen to join
What happens to the affinity of oxygen to haemoglobin when the partial pressure of oxygen is high?
Haemoglobin has a high affinity for oxygen, so readily combines with oxygen as there is a high oxygen saturation
What happens to the affinity of oxygen to haemoglobin when the partial pressure of oxygen is low?
Haemoglobin has a low affinity to oxygen, so oxygen is released as there is a low oxygen saturation
What’s the difference between the dissociation curve of fetal and adult haemoglobin?
The fetal haemoglobin graph is higher than the adult graph
What is the difference between fetal and adult haemoglobin?
Fetal haemoglobin has a higher affinity for oxygen
Why does fetal haemoglobin have a higher affinity for oxygen?
By the time the mother’s blood has got to the placenta, oxygen saturation has decreased
What’s the Bohr Effect?
when the partial pressure of carbon dioxide increases, the dissociation curve shifts right and more oxygen is released from blood
Chloride Shift
The movement of chloride ions into red blood cells that occurs when hydrogen carbonate ions are formed
How are hydrogen carbonate ions formed in chloride shift? (3)
Carbon dioxide diffuses into red blood cells
Carbonic anhydrase catalyses the combining of carbon dioxide and water to form carbonic acid
Carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions
Note
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