8. Transport in Mammals

Question 1

What is the circulatory system in mammals called?

Answer 1

a closed blood system, made up of vessels containing blood

Question 2

What type of circulatory system do mammals have?

Answer 2

double circulation, passes through the heart twice

Question 3

Explain what 2 systems make up a double circulatory system?

Answer 3

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

Question 4

Describe the structure and function of arteries

Answer 4

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

Question 5

Describe the structure and function of capillaries

Answer 5

• 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

Question 6

Describe the structure and function of veins

Answer 6

• 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

Question 7

What is tissue fluid?

Answer 7

• 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

Question 8

What does excessive tissue fluid cause?

Answer 8

oedema, when blood pressure is too high and too much fluid is forced out of the capillaries, accumulating in the tissues

Question 9

What is the function of tissue fluid?

Answer 9

exchanges of materials between cells and blood occur through tissue fluid

Question 10

Draw and label the heart (21)

Answer 10

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

Question 11

What is the cardiac cycle and how many times does it occur in 1 minute for humans?

Answer 11

the sequence of events that take place during one heartbeat, average 70 bpm

Question 12

Explain the 3 stages of the cardiac cycle

Answer 12

1. atrial systole: both atria contract, blood flows into ventricles, valves close to prevent backflow
2. 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
3. ventricular diastole: atria and ventricles relax, semilunar valves pushed shut, blood flows from veins through the atria and into the ventricles

Question 13

What is the pressure in atrial systole?

Answer 13

higher in the atrium, opens atrioventricular valve

Question 14

What is the pressure in ventricular systole?

Answer 14

higher in the ventricle, closes atrioventricular valves

Question 15

What is the pressure in ventricular diastole?

Answer 15

higher in the arteries, closes semilunar valves

Question 16

How long does atrial systole last?

Answer 16

0.1 seconds

Question 17

How long does ventricular systole last?

Answer 17

0.3 seconds

Question 18

How long does ventricular diastole last?

Answer 18

0.5 seconds

Question 19

What is myogenic?

Answer 19

cardiac muscle is myogenic because it contracts and relaxes even without nerve impulses stimulate movement

Question 20

What is the sinoatrial node?

Answer 20

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.

Question 21

Explain a heartbeat

Answer 21

1. SAN contracts, produces an electrical excitation wave across muscles in the atria, atrial walls contact
2. excitation wave travels to the atrioventricular node (AVN) which delays the impulse, ventricular walls contract a fraction of a second after atrial walls
3. excitation wave moves down the septum, along the fibres known as Purkyne tissue, reaches the base and moves upwards, causing ventricles to contract

Question 22

Where is the atrioventricular node?

Answer 22

the AVN is another patch of cardiac muscle, located in the septum

Question 23

Describe the structure of a red blood cell and its purposes

Answer 23

• 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

Question 24

Describe the structure of a white blood cell and its purposes

Answer 24

• made in bone marrow
• has nucleus
• generally large than RBC
• spherical or irregular shape

Question 25

What are the 2 types of white blood cells?

Answer 25

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

Question 26

Describe the structure of a haemoglobin molecule

Answer 26

* made up of 4 polypeptides, each polypeptide containing 1 haem group * each haem group bind with 1 O2 * haemoglobin + oxygen --> oxyhaemoglobin * Hb + 4O2 --> HbO8

Question 27

What is partial pressure?

Answer 27

a measure of the concentration of a gas

Question 28

What is percentage saturation, and what is the maximum amount of oxygen that a sample can combine with?

Answer 28

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%

Question 29

What is a dissociation curve? Draw and label.

Answer 29

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

Question 30

What is the chloride shift?

Answer 30

* 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

Question 31

What are the percentages in carbon dioxide transport?

Answer 31

1. 85% CO2 transported by the diffusion of hydrogencarbonate ions into blood plasma, carried in solution 2. 5% CO2 remain as molecules and dissolve in blood plasma 3. 10% CO2 diffuse into RBCs and combine with terminal amine groups of haemoglobin molecules, forming carbaminohaemoglobin

Question 32

What changes when the blood reaches the lungs?

Answer 32

1. low conc. of CO2 in alveoli compared to in blood, CO2 diffuses from blood into the air inside the alveoli 2. stimulates CO2 in carbahaemoglobin to leave RBC 3. hydrogencarbonate and hydrogen ions recombine to form CO2 molecules once more 4. haemoglobin molecules free to combine with oxygen again

Question 33

Draw out and explain the Bohr Effect

Answer 33

1. CO2 diffuses from respiring tissue into plasma, then into RBC 2. CO2 and H2O combine to form carbonic acid (H2CO3), catalysed by enzyme carbonic anhydrase found in RBC cytoplasm 3. H2CO3 dissociates (splits) to form H+ and HCO3- 4. 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.