Topic 5: Circulation and Gas exchange

Question 1

the by-products of internal processes must be removed from cells in the environment, how does the body do this?

Answer 1

food waste: digestion, metabolic waste: excretion, and gaseous waste: respiration

Question 2

how do simple animals (sponges) or animals with a gastrovascular cavity exchange gas and nutrients? what about more complex animals.

Answer 2

simple animals: simple diffusion (bc they have low metabolic need)

for very compartmentalized animals, diffusion is not fast enough, they need a circulatory system

Question 3

how do open circulatory systems work, (how is blood circulated and where does chemical exchange occur)

Answer 3

Blood cells can move from vessels into the interstitial fluid. Hemolymph is the interstitial and circulatory fluid. One (or more) heart contracts and pumps hemolymph through the circulatory vessels, it passes through interconnected sinuses (spaces around organs), chemical exchange occurs in the sinuses. Relaxation of the heart pulls the hemolymph back through pores (ostia that close when the heart contracts)

Question 4

what phyla have open circulatory systems, but what clade is the exception within one of these phylum

Answer 4

arthropods, and most molluscs (except cephalopods: squids, octopus, which have a closed circulatory system)

Question 5

which is more energetically costly open or closed circulatory systems

Answer 5

closed are more energetically costly, in open animals movement can help circulate hemolymph

Question 6

what is an advantage closed circulatory systems have that open don’t

Answer 6

Higher blood pressure (because of enclosed space) enables bulk flow of nutrients and gases in larger animals, also good for regulating blood to different organs and tissues.

Question 7

what is an additional function of open circulatory system in some animals

Answer 7

movement in some animals (spiders)

Question 8

how does a closed circulatory system work (how is blood circulated and where does chemical exchange occur)

Answer 8

Blood is contained in vessels and is distinct from the interstitial fluid. one (or more) heart pumps blood into large vessels that branch into smaller ones. Smaller vessels surround the organs for exchange. Chemical exchange occurs between the blood and interstitial fluid and also between the interstitial fluid and cells (2 steps).

Question 9

what are the 3 main blood vessels in vertebrates? what do they do?

Answer 9

Arteries- carry blood away from heart, veins- carry blood back to heart, capillaries-microscopic vessels at the site of exchange in organs.

arteries and veins are defined by direction (not oxygen concentration) a=away arteries

Question 10

list all the 5 blood vessel types in the order blood flows through them

Answer 10

arteries > arterioles (connect arteries to capillaries) > capillaries > venules (connect capillaries to veins) > veins

Question 11

what do capillary beds do

Answer 11

infiltrate every tissue to pass along substances into the interstitial fluid to deliver to all the cells

Question 12

what do portal veins do

Answer 12

carry blood between capillary beds (from the digestive tract to the liver)

Question 13

what are the two main muscles (chambers) in the heart

Answer 13

the atria and ventricles.

Question 14

explain single circulation, how blood flows and what animals is this in

Answer 14

seen in fish, 2-chambered heart, blood passes through the heart once per circuit. It enters the atrium, goes to ventricle, then arteries to gill capillaries where O2 diffuses in and CO2 diffuses out, blood travels to the rest of the body releasing O2 then returns to the heart.

Question 15

what are the drawbacks of a single circulation system

Answer 15

Blood pressure drops as it passes through the gills reducing efficiency of circulation, and the heart receives mostly deoxygenated blood.

Question 16

explain pulmocutaneous circuit, respiratory surfaces, how blood flows and what animals is this in

Answer 16

Occurs in reptiles and amphibians. Respiratory surfaces include lungs (pulmo) and skin (cutaneous). Frogs have a 3 chambered heart (2 atria, 1 ventricle), right atrium collects blood from the body and left atrium collects blood from the respiratory surfaces. Both atria empty into a single ventricle, with a ridge to separate the blood from the body and the respiratory surfaces. When the heart contracts oxygenated blood is sent to the systematic circuit while deoxygenated blood is sent to the pulmonary circuit.

Question 17

Double circulation involves 1. pulmonary circuit and 2. systemic circuit. Describe each circuit.

Answer 17

pulmonary circuit: blood moving between the heart and lungs is the pulmonary circuit. Systemic circuit: blood moving from the heart to the rest of the body.

Question 18

what are the drawbacks to double circulation

Answer 18

Energetically expensive BUT at least the heart receives oxygenated blood (unlike single circulation)

Question 19

what is an advantage to double circulation

Answer 19

heart repressurizes the blood

Question 20

explain the steps of double circulation in mammals and birds

Answer 20

Starts in the right ventricle. It contracts and pumps blood to the pulmonary arteries, which take the blood away from the heart to the lungs. Capillary beds in the lungs facilitate gas exchange there. Oxygenated blood flows through the pulmonary vein back towards the heart, in through the left atrium then the left ventricle, which pumps blood to the systemic circuit (to the body). The aorta brings blood to the arteries then arterioles, and capillaries exchange materials via diffusion. Then the blood is brought back to the heart from venules and veins to the superior (drains blood from head and forelimbs) and inferior vena cava (drains blood from trunk and hind limbs). It enters the heart from the vena cavae into the right atrium then back to the right ventricle to restart the process.

General pathway: starts in right side of heart which goes to the lungs, then back to heart this time left side from there blood goes to body. After body ends up back in right side heart.

Question 21

Partial pressure gradients are needed in gas exchange how does gas diffuse

Answer 21

from higher partial pressure to lower partial pressure

Question 22

whats respiratory media

Answer 22

the place where respiration occurs

Question 23

compare air and water respiratory media: O2 partial pressure, O2 concentration, density, viscosity. Which media is more demanding?

Answer 23

Air and water both have same partial pressure. Air has higher O2 concentration: 210 ml/L, water just has: 7 ml/L. Water is also more dense and viscous.

water is more demanding because of less O2 concentration and harder to move with higher viscosity and density.

Question 24

what’s a Respiratory surface?

Answer 24

specific structure that respiration takes place

Question 25

diffusion rate of gas exchange is directly proportional to __

Answer 25

the surface area of the respiratory surface

Question 26

diffusion rate is also inversely proportion to

Answer 26

distance, the closer the distance of diffusion, the faster is diffuses.

Question 27

In which animals do gases easily diffuse across their bodies because every cell is close to the external environment.

Answer 27

Sponges, cnidarians, flatworms

Question 28

what animals use skin as their respiratory surface

Answer 28

Frogs, other amphibians, earthworms

Question 29

what animals use gills as their respiratory surface

Answer 29

aquatic animals

Question 30

what animals use tracheae as their respiratory surface

Answer 30

insects

Question 31

what animals use lungs as their respiratory surface

Answer 31

terrestrial animals (most reptiles, all birds and mammals, amphibians have small lungs because mainly use skin to breathe)

Question 32

what's ventilation, how do aquatic animals do it

Answer 32

Movement of the respiratory medium over the respiratory surface. They must move their gills through the water or move water through their gills.

Question 33

whats countercurrent exchange

Answer 33

allows for exchange of materials/heat from fluids moving in opposite directions (blood flowing in opposite direction of water)

Question 34

describe tracheal systems in insects. How is it different in small vs large insects.

Answer 34

largest tubes are tracheae, open to the outside. Finest tubes (tracheoles) are close to the surface of nearly every cell. So there is gas exchange via diffusion across moist epithelium. Small insects don't need to ventilate. Diffusion is enough for gas exchange. Larger insects can ventilate with rhythmic pulses to expand and compress air in tubes.

Question 35

Describe how lungs are designed and how they transport oxygen.

Answer 35

Highly infolded and subdivided into numerous pockets (alveoli), requires the circulatory system to transport oxygen to body cells.

Question 36

How do amphibians breathe through their lungs

Answer 36

Positive breathing pressure inflates the lungs with forced air-flow (pushing).

Question 37

How do birds breathe through their lungs

Answer 37

circular breathing, when birds breathe air is passed over the gas exchange surface in 1 direction. Incoming air does not mix with the air going out. Uses 8-9 air sacs on either side of the lungs. Full cycle of air through the whole system requires 2 inhalation/exhalation cycles.

Question 38

How do mammals breathe through lungs. Which requires work and which is passive: exhalation or inhalation.

Answer 38

Negative breathing pressure pulls air into the lungs. Inhalation: diaphragm contracts (moves down), and rib muscles contract (outwards). This lowers the air pressure in the body compared to outside, and gas flows high to low. So inhalation requires work. Exhalation: diaphragm relaxes (moves up), increasing air pressure in the body, causing outflow of gas. So exhalation is passive.

Question 39

What 2 parts of the brain control breathing, which is the main one

Answer 39

medulla oblongata mainly, but also the pons.

Question 40

What allows for site-specific diffusion of gases along their partial pressure gradients

Answer 40

Partial pressures of CO2 and O2 can vary in the blood at different points. ex: alveolar capillaries have lower O2 partial pressure and higher CO2 partial pressure, allowing oxygen to flow high to low pressure, into the alveoli.

Question 41

What are respiratory pigments, what are they for, example?

Answer 41

They allow oxygen to bind to them and be circulated in the blood or hemolymph, to increase the amount of oxygen that can be transported at a given time. Protein bound to a metal (metalloprotein). Ex: hemoglobin

Question 42

How much of CO2 released by cellular respiration is transported in solution in the blood plasma. What happens to the rest of it.

Answer 42

7% of CO2 is transported. The rest diffuses from plasma into red blood cells. (erythrocytes) and reacts with water to from carbonic acid.

Question 43

How did diving mammals adapt to hold their breath longer?

Answer 43

They store large amount of oxygen in their blood or in specialized molecules called **myoglobin** in their muscles.