lec 21- gas exchange and circulation part 1

Question 1

what does surface area determine?

Answer 1

-the rate at which nutrients/ gases diffuse across a membrane and the rate at which waste products diffuse out
-when an object gets larger, its volume increases much faster than its surface area does
-large animals cannot rely on simple diffusion of gases/nutrients

Question 2

what is partial pressure?

Answer 2

the pressure of a particular gas in a mixture of gases

Question 3

how does oxygen and CO2 diffuse between environments and cells?

Answer 3

by their partial-pressure gradients, high to low

Question 4

why is it hard to breathe on Mt. Everest

Answer 4

because the partial pressure is low for oxygen, thus making it harder to take in the needed oxygen (partial pressure between atmosphere and lung tissues is small)

Question 5

what are the 5 parameters that rate of diffusion depends on?

Answer 5

1. solubility of gas
2. Temperature
3. surface area available for diffusion
4. differences in partial pressure of the gas across the gas exchange surface
5. thickness of the barrier in diffusion

Question 6

what 3 traits in animals maximize the rate of diffusion?

Answer 6

1. large surface area for gas exchange
2. thin respiratory surface
3. large partial pressure gradient of gas across surface

Question 7

how do small and large animals do gas exchange?

Answer 7

-small animals do direct diffusion across body surface
-large animals require a specialized organ, respiratory organs provide a greater surface area for gas exchange

Question 8

what are the 5 major steps in gas exchange?

Answer 8

1. ventilation is the movement of air or water through specialized gas-exchange organs
2. diffusion at the respiratory surface where O2 moves from air to water or into blood and CO2 moves from blood into air or water
3. circulation is the transport of dissolved O2 and CO2 throughout the body via the circulatory system
4. diffusion at the tissues where O2 moves from blood into tissues and CO2 moves from tissues to blood
5. cellular respiration is the cells use of O2 and production of CO2 which leads to low O2 levels and High CO2 levels in tissues

Question 9

what is responsible for the ventilation and diffusion at the respiratory surface?

Answer 9

the respiratory system

Question 10

what is responsible for the movement of O2, CO2, and other materials in the body?

Answer 10

circulatory system

Question 11

why do aquatic animals have to process 30 times more water than a land animal?

Answer 11

because the ocean contains way less oxygen the surface

Question 12

what are gills and the characteristics?

Answer 12

-outgrows of the body surface or throat, used for gas exchange
-present large surface area for oxygen to diffuse across
-can be internal or external

Question 13

how do fish ventilate their gills?

Answer 13

by opening and closing their mouths and the operculum (stiff flap over the gills, that creates a pressure gradient that moves water over the gills)

Question 14

what is ram ventilation?

Answer 14

it is when fast swimming fish get more water through their gills by opening their mouths

Question 15

how does movement of water through gills occur?

Answer 15

in one direction over long,thin structures called gill filaments that extend from each gill arch

Question 16

what is each gill filament composed of?

Answer 16

hundreds of thousands of sheetlike gill lamellae, capillaries run through each lamella

Question 17

what exchange system is used in each lamella in the gills?

Answer 17

countercurrent exchange so:

-small gradient in partial pressure of oxygen are maintained between water and blood over entire length of lamella
-large difference in partial pressure of oxygen between the start and the end

Question 18

what are examples of countercurrent exchange in animals?

Answer 18

fish gills, whale tongues

Question 19

what is the lung?

Answer 19

the organ of ventilation for terrestrial animals

Question 20

how does air enter the lungs?

Answer 20

air comes through the mouth and the nose where it then goes down the trachea to narrow tubes known as bronchi, the bronchi branch off into more narrow tubes known as bronchioles, then they go to alveoli which are tiny sacs of the lung that provide a large surface area for gas exchange

Question 21

how many alveoli do humans have per lung?

Answer 21

150 million

Question 22

what type of ventilation do humans and other mammals use?

Answer 22

negative pressure ventilation

Question 23

what is negative pressure ventilation?

Answer 23

it is when the pressure of the chest cavity is changed to allow ventilation

Question 24

what is the change in pressure in the chest cavity caused by?

Answer 24

by the downward motion of the thin muscular sheet called the diaphragm

Question 25

what is each lung surrounded by?

Answer 25

-a pleural sac which are two layers of cells with small space between them (pleural cavity)
-each pleural cavity has a small volume of pleural liquid
-intrapleural pressure is subatmospheric, keeps lungs inflated

Question 26

what are the two steps involved in the movement of the lungs?

Answer 26

1. inhalation- diaphragm moves down and the pressure in the chest cavity is lowered, causing lungs to expand and air to move in
2. exhalation- as the diaphragm relaxes, the chest cavity volume decreases and air is exhaled (passive process driven by elastic recoil of the lungs and chest wall as diaphragm and rib muscles relax, can become energy demanding during exercise)

Question 27

what part of the brain is responsible for the rate of breathing?

Answer 27

the medullary respiratory center (a part of the brain stem)

Question 28

during exercise, what happens to partial pressure of O2 and CO2?

Answer 28

muscles take up more O2, resulting in decrease of O2 partial pressure and increase in CO2 partial pressure

Question 29

what happens to the increased amount of CO2 in the blood during exercise?

Answer 29

-it reacts with water and cerebrospinal fluid (CSF) to form carbonic acid (H2CO3) which then dissociates into a hydrogen ion, H+, and bicarbonate ion, HCO3-.
-release of hydrogen ions lowers the blood and CSF pH, which is sensed by specialized chemoreceptors which stimulates CNS control centers to increase breathing rate and depth of inhalation
-increased breathing rate results in increased rate of oxygen delivery and increased rate of CO2 elimination to maintain constant partial pressures of both

Question 30

what is blood and plasma?

Answer 30

a fluid connective tissue consisting of cells in a watery extracellular matrix called plasma

Question 31

what is the bloods functions?

Answer 31

-transport oxygen and CO2
-transport nutrients to cells and digestive system
-move waste products to kidney and liver
etc.

Question 32

what are the 3 cellular components of blood?

Answer 32

1. platelets that minimize blood loss
2. white blood cells in the immune system
3. red blood cells transport oxygen from lungs to body and transport CO2 out

Question 33

what is the structure and function of hemoglobin?

Answer 33

-it consists of a four polypeptide chain, each of which binds to a non-protein group called heme that can bind to an iron ion which can bind to oxygen
-each hemoglobin molecule can bind to 4 oxygen molecules
-98% of oxygen is in blood, rest is in plasma

Question 34

why is there a diffusion gradient from hemoglobin to tissues?

Answer 34

because blood that leaves lungs has a high partial pressure of oxygen which can diffuse down the gradient to low partial pressure of oxygen in tissues

Question 35

what does 100% saturation of hemoglobin mean?

Answer 35

all possible binding sites contain an oxygen molecule

Question 36

what shape is the oxygen hemoglobin equilibrium curve and why?

Answer 36

-sigmoidal, because slow binding at start then leads to more binding known as cooperative binding. this then results in a capped 100% saturation of oxygen in hemoglobin

• low to high Po2 levels
  -low to high saturation of hemoglobin

Question 37

what happens with noncooperative binding of hemoglobin?

Answer 37

cant reach 100% saturation

Question 38

what causes a right and left shift of the oxygen hemoglobin equilibrium curve?

Answer 38

low pH = right shift due to low affinity for oxygen
high pH = left shift due to high affinity for oxygen
high temp = right shift due to low affinity for oxygen
low temp = left shift due to high affinity for oxygen
fetal hemoglobin = left shift due to high affinity for oxygen

Question 39

what catalyzes the formation of carbonic acid into bicarbonate and a proton, from CO2 in water in red blood cells?

Answer 39

carbonic anhydrase, CO2 diffuses into RBCs and turns into carbonic acid (H2CO3) then quickly dissociates into bicarbonate (HCO3-) and a proton

Question 40

what are the two reasons for why carbonic anhydrase activation in red blood cells is important?

Answer 40

1. protons produced induce bohr shift, which makes hemoglobin more likely to release oxygen
2. Pco2 in blood drops when CO2 is converted into bicarbonate, maintaining a strong partial pressure gradient (high in tissue low in blood)

-excess H+ binds to hemoglobin to prevent acidification

Question 41

once the blood returns to the lungs in the alveoli, how does CO2 release into the atmosphere?

Answer 41

the drop in Pco2 reverses the chemical reactions by:
1. protons leaving binding sites of hemoglobin
2. protons react with bicarbonate to form CO2
3. CO2 diffuses into alveoli and is exhaled from lungs

-causing Pco2 to increase

-high pressure in blood low in atmosphere

Question 42

what is the type of oxygen affinity of hemoglobin seen in the tissues and the lungs?

Answer 42

in tissues:
-right curve, low O2 affinity meaning release (low pH, high temp)

in lungs:
-left curve, high O2 affinity meaning loading (high pH, low temp)