Chapter 8 Transport in Mammals

Question 1

Mammalian circulatory system

Answer 1

A closed double circulation. This is because blood passes through the heart twice in one circulation of the body

Question 2

Function of pulmonary artery

Answer 2

Carries deoxygenated blood from the right ventricle of the heart to the lungs for gas exchange

Question 3

Function of pulmonary vein

Answer 3

Carries oxygenated blood from the lungs back to the left atrium of the heart

Question 4

Function of aorta

Answer 4

Carries oxygenated blood from the left ventricle to the rest of the body via systemic circulation

Question 5

Function of vena cava

Answer 5

Brings deoxygenated blood from the body back to the right atrium of the heart

Question 6

Structure of arteries

Answer 6

WALL THICKNESS: Thick
SMOOTH MUSCLE & ELASTIC: lots
LUMEN SIZE: narrow
VALVES: no
PRESSURE: high

Question 7

Structure of veins

Answer 7

WALL THICKNESS: Thin
SMOOTH MUSCLE & ELASTIC: less
LUMEN SIZE: wide
VALVES: yes
PRESSURE: low

Question 8

Structure of capillaries

Answer 8

WALL THICKNESS: one cell thick
SMOOTH MUSCLE & ELASTIC: none
LUMEN SIZE: very narrow
VALVES: no
PRESSURE: very low

Question 9

Inner layer of arteries and veins

Answer 9

Made up of a layer of endothelium consisting of a layer of flat cells, squamous epithelium, fitting together

Question 10

Middle layer of arteries and veins

Answer 10

Contains smooth muscle, collagen and elastic fibres

Question 11

Outer layer of arteries and veins

Answer 11

Contains elastic fibres and collagen fibres

Question 12

Elastic fibres

Answer 12

Recoil and contract, squeezing the blood and so moving it along in a continuous flow. They allow the walls to stretch, as pulses if blood surge through

Question 13

Smooth muscles

Answer 13

Contracts, reducing blood flow in arterioles. This controls volume of blood flowing into a tissue

Question 14

Collagen fibres

Answer 14

Give arteries strength, structure and flexibility

Question 15

Vasoconstriction

Answer 15

The narrowing of a muscular artery or arteriole, caused by the contraction of smooth muscles in its walls

Question 16

Vasodilation

Answer 16

The widening of a muscular artery or arteriole, caused by the relaxation of the smooth muscle in its walls

Question 17

Function of tissue fluid

Answer 17

Acts as the medium for exchange of substances between the blood and the cells. It delivers oxygen, glucose, amino acids, and other nutrients to the cells and removes waste products like carbon dioxide and urea

Question 18

Formation of tissue fluid

Answer 18

• At the arterial end of capillaries, hydrostatic pressure is high
• This pressure forces plasma out of the capillaries through the thin, permeable capillary walls. This fluid is called tissue fluid and it bathes the cells
• Red blood cells and plasma proteins are too large to leave the capillaries. Water, glucose, oxygen, amino acids, and other small molecules pass out
• Tissue fluid supplies nutrients and oxygen to cells by diffusion. It also picks up waste products like carbon dioxide and urea from cells
• At the venous end of capillaries, hydrostatic pressure falls as fluid has left
• Osmotic pressure from plasma proteins pulls some fluid back into the capillaries by osmosis
• Any excess tissue fluid is drained into the lymphatic system, eventually returning to the bloodstream

Question 19

Structure of red blood cells

Answer 19

• biconcave disc
• very small, 7 micrometres
• very flexible
• no nucleus, mitochondria, and endoplasmic reticulum

Question 20

Structure of white blood cells

Answer 20

• spherical or irregular in shape
• larger than red blood cells
• have nucleus

Question 21

Structure of neutrophils

Answer 21

Type of phagocytic white blood cells
- lobed nucleus and granular cytoplasm

Question 22

Structure of monocytes

Answer 22

Largest type of white blood cell
- bean-shaped nucleus

Question 23

Mature monocytes

Answer 23

Macrophytes

Question 24

Role of haemoglobin - transport of O2

Answer 24

• In the lungs, where partial pressure of oxygen is high, haemoglobin binds oxygen to form oxyhaemoglobin
  Hb+4O2→Hb(O2)4
• In respiring tissues, where partial pressure of oxygen is low, haemoglobin releases oxygen for use in aerobic respiration

Question 25

Role of carbonic anhydrase - transport of CO2

Answer 25

- CO₂ diffuses into RBCs from respiring tissues - Inside RBCs, the enzyme carbonic anhydrase catalyzes this reaction: CO2 + H2O ⇌ H2CO3(carbonic acid) ⇌ H+ + HCO3- - Carbonic acid dissociates into hydrogen ions and hydrogencarbonate ions (HCO3-) - Most CO2 is transported in the blood as HCO3- in the plasma - In lungs, carbonic anhydrase converts HCO3- back into CO2 so it can be exhaled

Question 26

Formation of haemoglobinic acid

Answer 26

- H+ ions produced could lower pH, but they are buffered by haemoglobin - Haemoglobin binds to H+ ions to form haemoglobinic acid (HHb): Hb + H+ → HHb - This prevents blood from becoming too acidic and helps maintain blood pH

Question 27

Formation of carbaminohaemoglobin

Answer 27

- A smaller amount of CO2 binds directly to haemoglobin to form carbaminohaemoglobin: CO2  + Hb → HbCO2 - This occurs at amino groups on haemoglobin, not at the oxygen-binding sites

Question 28

The oxygen dissociation curve of adult haemoglobin

Answer 28

- The oxygen dissociation curve shows the percentage saturation of haemoglobin with oxygen plotted against the partial pressure of oxygen (pO2) - At low pO2, the curve is shallow. Haemoglobin has low affinity for oxygen and binds it slowly - As pO2 increases, the curve rises steeply. Hbinds oxygen more rapidly - At high pO2, the curve plateaus. Haemoglobin approaches full saturation and picks up little extra oxygen

Question 29

The importance of the oxygen dissociation curve at partial pressures of oxygen in the lungs

Answer 29

- The pO2 in alveoli is high, so haemoglobin has a high affinity for oxygen - The curve levels off near 100% saturation, meaning haemoglobin loads nearly all available oxygen - This ensures maximum oxygen uptake in the lungs to be transported around the body

Question 30

The importance of the oxygen dissociation curve at partial pressures of oxygen in respiring tissues

Answer 30

- The pO2 is much lower due to oxygen consumption by cells - The steep part of the curve means haemoglobin releases oxygen readily - This ensures efficient delivery of oxygen to tissues where it's needed most (especially during exercise, where pO2 drops further)

Question 31

The Bohr shift

Answer 31

The decrease in affinity of haemoglobin for O2 that occurs when CO2 concentration increases, or when pH decreases, or when temperature rises

Question 32

Importance of Bohr Shift

Answer 32

- Enhances O2 delivery to respiring tissues, which need more O2 for aerobic respiration - Ensures haemoglobin unloads more O2 where CO2 levels are high - Helps match O2 supply to metabolic demand, improving efficiency of gas exchange

Question 33

The chloride shift

Answer 33

The movement of chloride ions into red blood cells from blood plasma, to balance the movement of hydrogencarbonate ions into the plasma from red blood cells

Question 34

Process of the chloride shift

Answer 34

- CO2 diffuses from body tissues into red blood cells - Inside red blood cells, CO2 reacts with water to form carbonic acid (H2CO3), catalyzed by the enzyme carbonic anhydrase - Carbonic acid dissociates into hydrogen ions (H+)band hydrogen carbonate ions (HCO3-) - The HCO3- ions diffuse out of the red blood cell into the plasma - To maintain electrical neutrality, Cl- ions move into the red blood cell from the plasma

Question 35

Role of plasma in the transport of CO2

Answer 35

- Dissovled CO2 in plasma: a small proportion of CO2 is dissolved directly in the plasma. This dissolved CO2 can diffuse into the alveoli in the lungs to be exhaled - As HCO3- ions in plasma: Most CO2 enters red blood cells, where it reacts with water to form carbonic acid (H2CO3), catalyzed by carbonic anhydrase. The HCO3- ions then diffuse out of red blood cells into the plasma, where they are transported in solution - As carbaminohaemoblobin: CO2 directly combine with the terminal amine groups (-NH2) of some of the haemoglobin molecules, forming carbaminohaemoglobin

Question 36

External structure of the heart

Answer 36

- made up of cardiac muscle - Blood vessels: Vena cava, Pulmonary artery, Pulmonary vein, Aorta - Coronary arteries

Question 37

Internal structure of the heart

Answer 37

- 4 chambers: right/left ventricles, right/left atrium - Valves: Atrioventricular valves ( tricuspid and bicuspid ), Semilunar valves - Septum

Question 38

Differences in thickness of walls: Artia vs Ventricles

Answer 38

- The walls of the atria are thinner than those of the ventricles - Atria only need to pump blood from the atria into the ventricle. Therefore, they require less force and less muscle. - Ventricles must pump blood out of the heart: Right ventricle pumps blood to the lungs. Left ventricle pumps blood to the entire body. This requires higher pressure, so their walls are thicker and more muscular

Question 39

Differences in thickness of walls: Left ventricle vs Right ventricle

Answer 39

- The left ventricle wall is thicker than the right ventricle wall - The left ventricle must generate high pressure to pump blood through the aorta to the whole body, which involves a longer distance and more resistance - The right ventricle only pumps blood to the lungs, which are nearby and require lower pressure - If the right ventricle were as strong as the left, it could damage the delicate capillaries in the lungs

Question 40

The cardiac cycle

Answer 40

- Atria contract, increasing atrial pressure - Atrial pressure > ventricular pressure, so the atrioventricular valves are open - Blood flows from atria to ventricles - Semilunar valves remain closed, as arterial pressure > ventricular pressure - Ventricles contract, increasing ventricular pressure - Ventricular pressure > atrial pressure, so AV valves close - When ventricular pressure > pressure in aorta and pulmonary artery, semilunar valves open, allowing blood to flow into the aorta and pulmonary artery - Both atria and ventricles relax - Ventricular pressure falls below arterial pressure, so semilunar valves close - As ventricular pressure < atrial pressure, AV valves reopen, and blood flows passively from atria to ventricles

Question 41

Roles of the sinoatrial node in the cardiac cycle

Answer 41

Acts as a pacemarker, generating electrical impulses ( action potentials ), causes the atria to contract

Question 42

Roles of the atrioventricular node in the cardiac cycle

Answer 42

Receives the electrical impulse from the SA node and provides a short delay before passing the impulse to the ventricles

Question 43

Roles of the Purkyne tissue in the cardiac cycle

Answer 43

- Conducts the electrical impulse from the bundle of His to the ventricles, causing the ventricles to contract - It ensures that the ventricles contract from the bottom upwards, which is important for efficient blood ejection into the pulmonary artery and aorta.

Question 44

How electrical excitation waves move through the heart

Answer 44

- SA node contracts, it produces an electrical excitation wave which sweeps through all the muscle in the atria of the heart - Atrial walls contract - Excitation wave sweeps onwards and reaches AV node - AV node delays the impulse for a fraction of a second, before it travels down into the ventricles - Excitation wave moves swiftly down through the Purkyne tissue - Once at the base of the ventricles it sweeps upwards, through the ventricle walls - Ventricles contract - Ventricles then relax, the muscle in the SA node contracts again and sequence repeats