Unit 8 - Transport in Mammals Flashcards
What does closed circulatory system mean?
The blood pumped by the heart is contained within blood vessels and doesnt come into direct contact with cells
Describe the journey of blood through the circulatory system [9]
- Heart
- pulmonary artery
- lungs
- pulmonary vein
- heart
- aorta
- body
- vena cava
- heart
Define the term double circulatory system
The blood flows around the heart in two circuits
Advantages of a closed system [2]
- Lower blood vol required to keep system moving
- Pressure can be controlled and maintained
Advantages of a double circ system [4]
- Maintains blood pressure around whole body
- More efficient uptake of oxygen
- Effient delivery of oxygen and nutrients
- Blood pressure can differ in pulmonary and systemic systems
Relate structure of arteries to function [5]
- Thick muscular walls to withstand high pressure
- Elastic tissue allows stretching and recoil to prevent pressures surges
- Narrow lumen to maintain pressure
- smooth muscle which enables them to vary blood flow
- lined with smooth endothelium to reduce friction and ease blood flow
Relate vein structure to function [4]
- Wide lumen eases blood flow
- thin walls eases compression by skeletal muscles
- Require valves to prevent backflow of blood
- less muscular and elastic tissue as they dont have to control blood flow
Relate capillary structure to function [3]
- Walls only one cell thick giving short diffusion distance
- Narrow Lumen, red blood cells squeeze through decreasing the diffusion distance
- numerous and highly branched, providing large surface area
Relate arteriole structure to function [2]
- Branch off arteries and veins in order to feed blood into and take blood away from the capillaries
- Smaller than arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels
Describe structure of erythrocyte (red blood cell)
- Large surface area
- biconcave disks
- no nucleus and no organelles to maximize O2 carrying ability
Describe the structure of neutrophils [2]
- irregular lobed nucleus
- cytoplasm contains fine granules
Describe structure of lymphocytes [3]
- Very large nucleus in proportion to cell size
- small amount of cytoplasms
- round nucleus
What is tissue fluid? [2]
- A fluid surrounding cells and tissues that contains glucose, amino acids, oxygen and other nutrients.
- It supplies these to cells, while removing any waste material
Outline the different pressures involved in the formation of tissue fluid [2]
- 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 proteins in the plasma
How is tissue fluid formed? [2]
- 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? [2]
- Friction
- Lower volume of blood (Dispersion of blood through capillaries)
What happens at the venous end of the capillary [2]
- Oncotic pressure is greater than hydrostatic pressure
- fluid moves down its water potential gradient back into the capillaries
How is tissue fluid removed? [2]
- Tissue fluid drains into the lymphatic system where it is referred to as ‘lymph’
- the lymph returns to the blood via the subclavian veins
What is the main component of both blood and tissue fluid?
water
Why is water important in body fluids? [2]
- Water acts as a solvent in order to transport material in biofluids
- Water has a high specific heat capacity. Meaning, a large amount of energy is required to change its temperature, keeping the body at a consistent temperature.
Describe the role of haemoglobin [3]
- Present in red blood cells
- oxygen molecules bind to haem groups and are transported around the body
- They are released where oxygen is needed in respiring tissues
How does partial pressure of oxygen affect oxygen haemoglobin binding? [3]
- Haemoglobin has a variable affinity for oxygen depending on the partial pressure of xygen
- at high p(O2), oxygen associates to form oxyhemoglobin
- At low p(O2) oxygen disassociates to form deoxyhaemoglobin
How is carbon dioxide carried from respiring cells to lungs? [3]
- transported in aqueous solution in the plasma
- As hydrogen carbonate ions in the plasma
- Carried as carbaminohaemoglobin in the blood
What is the chloride shift?
- Process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes
Why is the chloride shift important?
It maintains the electrochemical equilibrium of the cell
What is the function of carbonic anhydrase
- Catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid
State the 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 shift [4]
- Carbonic anhydrase is present in red blood cells
- Catalyses the reaction of carbon dioxide and water to form carbonic acid, which dissociates to produce H+ ions
- H+ ions combine with the haemoglobin to form haemoglobinic acid
- Encourages oxygen to dissociate from haemoglobin
Why is a higher conc of red blood cells important for human populations living at high altitudes? [2]
- High altitude, low p(O2), oxygen saturation in red blood cells will decrease
- To carry an equal volume of O2 in blood, a higher conc of red blood cells is required
What is plasma [2]
- Main component of the blood (yellow liquid) that carries red blood cells
- Contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste. Also distributes heat
Describe and explain the shape of a dissociation curve for adult hemoglobin
- Sigmoidal curve (s shape)
- When the first O2 molecule binds, it changes the tertiary structure of haemoglobin so that it’s easier for the second and third molecules to bind
- Third molecule changes the tertiary structure of hemoglobin so that it is more difficult for the fourth molecule to bind
Describe what happens during cardiac diastole [4]
- Heart is relaxed
- Blood enters the atria, increasing the pressure and opening the atrioventricular valves
- This allows blood to flow into the ventricles
- Pressure in the ventricles is lower than in the arteries, so semilunar valves remain closed
Describe what happens during atrial systole [2]
- The atria contract, forcing the AV valves open.
- Blood flows into the ventricles
Describes what happens during ventricular systole [3]
- The ventricles contract
- The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves
- Blood flows into the arteries
Explain how the heart contracts [3]
- SAN initiates and spreads impulse across the atria, so they contract. Thick fibrous wall prevent impulse spreading directly to the ventricles
- AVN receives, delays and then conveys the impulse down the bundle of His
- Impulse travels into the purkyne fibres which branch across the ventricles, so they contract from the bottom up
Why do the walls of the chambers of the heart vary in thickness? [2]
- Walls of both atria relatively thin, only have to cap blood in ventricles as they fill mostly passively
- Left ventricle wall significantly thicker than right, left must provide pressure for systemic flow, right only has to supply pulmonary system. Both are thicker than atria
