8. Transport in Mammals Flashcards
What is the circulatory system in mammals called?
a closed blood system, made up of vessels containing blood
What type of circulatory system do mammals have?
double circulation, passes through the heart twice
Explain what 2 systems make up a double circulatory system?
systemic circulation: oxygenated blood goes from the heart to all of the body except the lungs, and back to the heart
pulmonary circulation: deoxygenated blood goes from the heart to the lungs, and back to the heart as oxygenated blood
Describe the structure and function of arteries
tunica intima: a layer lining tissue called endothelium, a layer of flat cells called squamous epithelium, a layer of elastic fibres, smooth and minimises friction
tunica media: smooth muscle, collagen and elastic fibres
tunica externa: elastic fibres and collagen fibres
- responsible for vasoconstriction and vasodilation
- 2 types, muscular arteries and elastic arteries, depending on the amount of elastic fibres in the tunica media
- high pressure
- carries blood AWAY FROM the heart
Describe the structure and function of capillaries
- arteries branch out to form capillaries
- takes blood as close as possible to all cells for rapid transfer of substances between cells and blood
- extremely thin walls made of a single layer of endothelial cells
- low pressure
- partially permeable due to tiny gaps in between endothelial cells
Describe the structure and function of veins
- capillaries join to form veins
- very low pressure
- compared to arteries, thinner tunica media and fewer elastic fibres and muscle fibres
- has semilunar valves to help move blood towards the heart
- carries blood BACK TO the heart
What is tissue fluid?
- leaked plasma from the gaps between the cells in the walls of the capillaries
- on the arterial end, there is more protein in blood plasma than in tissue fluid, so water moves from capillaries into tissue fluid by osmosis (net movement of water out of the capillary)
- on the venule end, there is a net movement of water into the capillary
What does excessive tissue fluid cause?
oedema, when blood pressure is too high and too much fluid is forced out of the capillaries, accumulating in the tissues
What is the function of tissue fluid?
exchanges of materials between cells and blood occur through tissue fluid
Draw and label the heart (21)
right side: deoxygenated
vena cava (2, one from body, one from head)
valve in vena cava
pulmonary artery
pulmonary semilunar valve
right atrium
tricuspid valve
right ventricle
tendon
left side: oxygenated
aorta
pulmonary vein
valve in pulmonary vein
left atrium
aortic semilunar valve
bicuspid valve
papillary muscle
left ventricle
thick muscular wall of left ventricle
septum
What is the cardiac cycle and how many times does it occur in 1 minute for humans?
the sequence of events that take place during one heartbeat, average 70 bpm
Explain the 3 stages of the cardiac cycle
- atrial systole: both atria contract, blood flows into ventricles, valves close to prevent backflow
- ventricular systole: both ventricles contract, atrioventricular (_cuspid) valves pushed shut by the pressure in the ventricles, semilunar valves pushed open, flood flows into the arteries
- ventricular diastole: atria and ventricles relax, semilunar valves pushed shut, blood flows from veins through the atria and into the ventricles
What is the pressure in atrial systole?
higher in the atrium, opens atrioventricular valve
What is the pressure in ventricular systole?
higher in the ventricle, closes atrioventricular valves
What is the pressure in ventricular diastole?
higher in the arteries, closes semilunar valves
How long does atrial systole last?
0.1 seconds
How long does ventricular systole last?
0.3 seconds
How long does ventricular diastole last?
0.5 seconds
What is myogenic?
cardiac muscle is myogenic because it contracts and relaxes even without nerve impulses stimulate movement
What is the sinoatrial node?
SAN, or the pacemaker, is a patch of cardiac muscles in the right atrium of the heart that sets a rhythmic pattern for all the other cardiac muscle cells in the heart.
Explain a heartbeat
- SAN contracts, produces an electrical excitation wave across muscles in the atria, atrial walls contact
- excitation wave travels to the atrioventricular node (AVN) which delays the impulse, ventricular walls contract a fraction of a second after atrial walls
- excitation wave moves down the septum, along the fibres known as Purkyne tissue, reaches the base and moves upwards, causing ventricles to contract
Where is the atrioventricular node?
the AVN is another patch of cardiac muscle, located in the septum
Describe the structure of a red blood cell and its purposes
- shaped like a biconcave disc: larger surface area for oxygen to diffuse quickly
- small, 7um in diameter: haemoglobin molecules close to cell surface membrane and can quickly exchange oxygen with external tissue fluid, or as close as possible to adjacent cells
- flexible: can squeeze through capillaries that are narrower than 7um
- made up of a mesh-like network of protein fibres: spring back to biconcave shape when squashed
- no nucleus, no mitochondria, no endoplasmic reticulum: more room for haemoglobin
- broken down in liver, made in bone marrow
Describe the structure of a white blood cell and its purposes
- made in bone marrow
- has nucleus
- generally large than RBC
- spherical or irregular shape
What are the 2 types of white blood cells?
phagocytes:
* destroy invading microorganisms by phagocytosis
* neutrophil, with lobed nucleus and granular cytoplasm
* monocytes, can develop into different type of phagocyte macrophage, which is found in tissues, acting as antigen-presenting cells (APCs)
lymphocytes:
* destroy invading microorganisms by secreting antibodies that attach to invading cells
* smaller than phagocytes
* large round nucleus
* small amount of cytoplasm only
Describe the structure of a haemoglobin molecule
- made up of 4 polypeptides, each polypeptide containing 1 haem group
- each haem group bind with 1 O2
- haemoglobin + oxygen –> oxyhaemoglobin
- Hb + 4O2 –> HbO8
What is partial pressure?
a measure of the concentration of a gas
What is percentage saturation, and what is the maximum amount of oxygen that a sample can combine with?
percentage saturation: calculated as a percentage of the maximum amount
* the degree of oxygen that is combined with haemoglobin in blood
maximum amount of oxygen: 100%
What is a dissociation curve? Draw and label.
a graph showing the percentage saturation of a pigment with oxygen (y axis), and the partial pressure of oxygen (x axis)
- S shaped sigmoid curve
- Bohr shift, to the right due to higher CO2 concentration, decrease in affinity of haemoglobin for oxygen when carbon dioxide is present
What is the chloride shift?
- negatively charged hydrogencarbonate ions diffuse into plasma, chloride ions move into RBC to balance the movement
- otherwise, the inside of the RBC would have a positive charge because hydrogen ions would acumulate as they cannot leave the cell
What are the percentages in carbon dioxide transport?
- 85% CO2 transported by the diffusion of hydrogencarbonate ions into blood plasma, carried in solution
- 5% CO2 remain as molecules and dissolve in blood plasma
- 10% CO2 diffuse into RBCs and combine with terminal amine groups of haemoglobin molecules, forming carbaminohaemoglobin
What changes when the blood reaches the lungs?
- low conc. of CO2 in alveoli compared to in blood, CO2 diffuses from blood into the air inside the alveoli
- stimulates CO2 in carbahaemoglobin to leave RBC
- hydrogencarbonate and hydrogen ions recombine to form CO2 molecules once more
- haemoglobin molecules free to combine with oxygen again
Draw out and explain the Bohr Effect
- CO2 diffuses from respiring tissue into plasma, then into RBC
- CO2 and H2O combine to form carbonic acid (H2CO3), catalysed by enzyme carbonic anhydrase found in RBC cytoplasm
- H2CO3 dissociates (splits) to form H+ and HCO3-
- Hb has higher affinity for H+ than it does for O2, therefore an increase in H+ conc. causes oxyhaemoglobin to split: HbO8 + H+ –> HHb + 4O2 (haemoglobinic acid)
- haemoglobin removes excess hydrogen ions from the solution, helping to maintain pH of blood as neutral, because the high concentration of hydrogen ions that would be formed by carbon dioxide dissociating produces a low and acidic pH
- presence of a high partial pressure of carbon dioxide causes haemoglobin to release oxygen more readily, and high conc. of CO2 are found in actively respiring tissues which need oxygen.
