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Flashcards in Mod 3 Chap 8: Transport In Animals Deck (34)
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1

Explain the need for specialized transport systems in animals.🌟

- bigger organisms = greater distance between cells + outside of the body, so diffusion too slow for these bigger organisms to transport substances in and out
- also, metabolic demands of multicellular animals = high so diffusion over long distances = not enough to supply quantities needed
- SA:V ratio smaller in bigger multicellular organisms, so diffusion distances = bigger + amount of SA to absorb / remove substances becomes smaller too
- waste products of metabolism need to be removed from cells + transported to excretory organs
- food digested in one organ system, but needs to be transported to every cell for respiration
- hormones or enzymes may be made in one place but needed in another
So all require specialized transport systems.

2

What are the different types of circulatory systems.🌟

- open circulatory systems
- closed (single / double) circulatory systems

3

Describe open circulatory systems.🌟

- mostly found in insects
- blood or 'haemolymph' not enclosed in blood vessels at all times
- haemolymph pumped straight from heart into open body cavity of animal called 'haemocoel', via main artery
- transport medium in haemocoel is under low pressure + comes into direct contact w/ tissues + cells
- exchange between transport medium + cells takes place here
- transport medium then returns to heart through open ended vessel
- however, oxygen transported differently, via tracheal system

4

Describe single closed circulatory systems.🌟

e.g fish
- blood flows through heart, pumped out + travels all round body before returning back to heart, so travels once through heart for each complete circulation of body
- blood passes through 2 sets of capillaries (exchanging O2 + CO2 in one, + exchanging substances between cells in other) before returning to heart
- blood pressure now V low as capillaries / vessels are v narrow, so blood returns to heart slowly
- this limits efficiency of exchange processes, meaning activity levels in animal w/ single closed circulatory systems = relatively low

5

Describe double closed circulatory systems.🌟

e.g. Humans
- most efficient system for transporting substances around body as has 2 separate circuits
- one takes blood to lungs to pick up O2 (pulmonary circulation) + unload CO2
- other carries blood w/ O2 + nutrients around body to tissues + cells, then picks up waste (systemic circulation)
- so blood travels twice through heart for each circulation of body
- this increases pressure of blood after passing through lungs, so blood flows more quickly to body tissues when needed urgently.

6

Describe the structure and function of the arteries.🌟

Function:
- carry blood away from heart to tissues in body
- carry oxygenated blood, (apart from pulmonary artery = deoxygenated to lungs)
- carry blood at high pressure

Structure:
- small lumen but thick walls
- elastic fibres: allow arteries to withstand force of blood pumped out of heart + helps stretching to take larger vols of blood
- smooth endothelium lining: blood flows easily over it
- thick wall: w/ collagen for strength to contain high pressure blood
- some smooth muscle

7

Describe the structure and function of the arterioles.🌟

Function:
- link arteries to capillaries
- constrict or dilate to control flow of blood into organs (vasodilation and vasoconstriction)

Structure:
- more smooth muscle + less elastin than arteries
- little pulse surge
- some collagen

8

Describe the structure and function of the veins.🌟

Function:
- carry blood towards heart from cells in body
- mostly carry deoxygenated blood, but pulmonary vein carries oxygenated blood from lungs to heart
- carry low pressure blood
- veins flattened by surrounding muscle to force blood up vein (hence why movement is needed to prevent blood clot)

Structure:
- large lumen but thin walls, so carry large vol of blood
- valves: prevent back flow of blood
- more collagen than elastic fibres
- smooth, thin endothelium lining so blood flows easily

9

Describe the structure and function of the venules.🌟

Function:
- carry deoxygenated blood from capillaries to larger veins, so link capillaries w/ veins
- several venules join to form a vein

Structure:
- v thin walls
- small amount of smooth muscle

10

Describe the structure and function of the capillaries.🌟

Function:
- link arterioles w/ venules
- substances exchanged through capillary walls between tissues + blood
- mostly receives oxygenated blood from arterioles
- by time blood leaves capillary for venules, it is deoxygenated.

Structure:
- microscopic blood vessels
- lumen so small that red blood cells travel through single file
- large gaps between endothelial cells in capillary walls: substances can pass out of capillaries into fluid of surrounding cells
- large SA for diffusion of substances into + out of blood
- cross-sectional area of capillaries = greater than arterioles supplying them blood, so rate of blood flow falls, giving more time for exchange of materials
- walls only one endothelial cell thick, giving v thin layer for diffusion.

11

Describe the formation of tissue fluid from blood plasma.🌟

- blood under high pressure, as flows through arterioles into capillary at arteriole end of capillary, from surge of blood occurring w/ heart contractions (this = hydrostatic pressure, so here = high)
- oncotic pressure, attracting water in by osmosis, = lower than HP, so fluid squeezed out of capillaries
- fluid fills spaces between cells, = called tissue fluid
- tissue fluid has same composition as blood plasma, just without red blood cells + plasma proteins
- diffusion between blood + cells occurs through tissue fluid.

12

Describe what the cardiac cycle involves.🌟

- includes all events taking place in heart during one heart beat
- when cardiac muscle contracts, pressure in heart increases, so blood forced out (systole)
- when cardiac muscle relaxes, pressure in heart decreases, so blood flows in (diastole)
- 'lub' sound of heartbeat caused by closing of valves between atrium + ventricle due to increased pressure
- 'dub' sound of heartbeat comes from closing of semi-lunar valves due to increased pressure in arteries

13

Explain the order of events during one heartbeat (the cardiac cycle).

- atrial pressure in left atrium = low, but starts to rise, + is highest when walls contract forcing blood into left ventricle. Left ventricular pressure increases when filled w/ blood.
- atrioventricular valve (bicuspid) valve closes + walls relax
- left ventricle thick wall contracts, causing dramatic rise in ventricular pressure, w/ help from closed AV valve (bicuspid)
- semi lunar valves open, blood passes into aorta so pressure in aorta rises
- ventricle pressure decreases as walls relax, blood empties from ventricles. Aortic pressure (in aorta) falls due to elasticity of aorta wall creating recoil action
- semi lunar valves closes. Recoil in aorta causes temporary rise in aortic pressure at start of relaxation phase of ventricle (where ventricular pressure is still falling)
- pressure falls to lowest in ventricles, walls completely relax. Atrioventricular / mitral valves open, some blood moves into ventricle so pressure slightly decreases in atrium
- aortic pressure continues to decrease due to relaxation caused by recoil of walls due to elasticity
- ventricular volume rises as atria both contract, ventricles fill with blood
- ventricular volume drops suddenly as blood forced out into aorta when semi lunar valves open
- volume in ventricles increases again, ventricles fill with blood

14

Describe the use of ECG traces.

- Electrocardiograms record electrical activity in heart by measuring electrical differences in skin, as a result of heart's electrical activity.
- electrodes stuck to clean skin to give good contact for reliable results
- signal from each electrode fed into machine which produces an ECG
- used to help diagnose heart problems

15

Explain the interpretation of ECG's by defining the terms
a) Bradycardia
b) Tachycardia
c) Ectopic heartbeat
d) Atrial Fibrillaation
🌟

a) Bradycardia: when heart rate slows to below 60bpm. Can occur in fit people as training slows heartbeat, but severe bradycardia may need artificial pacemaker to keep best steady

b) Tachycardia: when heart rate = v rapid, over 100 bpm. Often normal, e.g, when exercising. If abnormal, may be caused by problems w/ electrical control of heart, may need surgery / medication.

c) Ectopic heartbeat: extra heartbeats outside of normal rhythm. Most people have at least one a day, usually normal but can be linked to serious conditions when v frequent.

d) Atrial fibrillation: example of an Arrhythmia (abnormal rhythm of heart). Rapid electrical impulses generated in atria, + atria contract v fast (fibrillate). if don't contract properly + only some impulses are passed onto ventricles which contract much less often, heart will not pump blood v effectively.

16

Describe the internal structure of the mammalian heart.🌟

(From left top to right top, looking into it)

- pulmonary artery
- superior vena cava
- inferior vena cava
- right atrium
- tricuspid valve (atrioventricular / mitral valves)
- chordae tendinae
- right ventricle
- semi lunar valve (pulmonary)
- septum
- semi lunar valve (aortic)
- left ventricle
- chordae tendinae
- bicuspid valve (atrioventricular / mitral valves)
- left atrium
- pulmonary vein
- aorta

17

Describe the what can be seen from / in the external structure of the heart.🌟

Superior vena cava (top left)
Right pulmonary veins (left)
right atrium (left)
Right coronary artery (running on top of right ventricle)
Right cardiac vein (on top of right ventricle next to right coronary artery)
Inferior vena cava (bottom left)
Right ventricle (bottom left)
Left ventricle (bottom right)
Left cardiac vein (running on top of left ventricle)
Left coronary artery (next to left cardiac vein on top of left ventricle)
Left pulmonary veins (right)
Left atrium (right)
Left pulmonary artery (right)
Aorta (top right)

18

Describe the heart in general.

- located between lungs and behind septum
- a cardiac muscle w/ involuntary striated muscle found in walls, meaning it beats continuously + doesn't tire
- often referred to as myocardium
- enclosed by pericardium
- pericardium = tough double layered sac covering + protecting heart from over expansion + infection
- pericardial fluid secreted to aid movement + protect heart from jerking movements / shock.

19

Describe the aortas role.🌟

Leaves heart from left ventricle + distributes oxygenated blood to body in systemic circulation.

20

Describe the pulmonary artery's role.🌟

Leaves heart from right ventricle + carries deoxygenated blood to lungs, in pulmonary circulation.

21

Describe the vena cava's role.🌟

Enters heart through right atrium, delivering oxygenated blood to heart from rest of body.
(Superior: delivers blood from upper body
Inferior: delivers blood from lower body).

22

Describe the pulmonary veins🌟

Enters heart through left atrium, delivering oxygenated blood from lungs.

23

Describe how the heart action is initiated.🌟

- heart muscle that contracts is myogenic, meaning it is capable of contracting without nervous impulse

24

Describe how the heart action is coordinated.🌟

Achieved through actions of the:
- Sinoatrial node (SAN) aka 'pacemaker'
- atrioventricular node (AVN)
- purkyne tissue (pronounce purkinje)

SAN:
- located in upper wall of right atrium
- main job is atrial systole
- sets rate of contraction for heart
- spontaneously contracts + generates nerve impulses that travel through heart wall causing both atria to contract (initiating heartbeat)
- made of myogenic tissue

AVN:
- when impulses generated by SAN reach AVN, AVN, delays them for one tenth of a second
- delay allows atria to contract which ensures they are fully emptied of blood
- AVN then sends impulses down 'Bundle of His'
- this = bundle of purkyne fibres (nerve tissue) + branches into two bundles
- impulses carried down centre of heart to left + right ventricles (in the purkyne fibres in ventricle walls)

25

Describe heamoglobin.🌟

- heamoglobin = protein found in erythrocytes (red blood cells), made of four haems / peptide chains
- oxygen binds to it to make oxyhemoglobin
- without oxygen it is called deoxyhaemoglobin
- haem contains iron (2+) molecules, so attracts oxygen (2-) molecules.
(Affinity = haem's ability to bind w/ oxygen)

26

Describe how haemoglobin transports oxygen.🌟

- O2 levels in cells = low when erythrocytes enter capillaries in lungs
- gives steep concentration gradient between inside erythrocytes + air in alveoli
- O2 moves into erythrocytes + binds w/ haemoglobin
- as soon as one oxygen molecule binds to a haem group, haemoglobin molecule changes shape, so easier for next oxygen molecules to bind (this = positive cooperativity, haems affinity increases)
- now free oxygen concentration in erythrocyte stays low as oxygen = bound to haemoglobin, maintains steep diffusion gradient until all of haemoglobin = saturated w/ O2.
- when blood reaches tissues, situation is reversed
- concentration of O2 in cytoplasm of body cells = lower than in erythrocytes
- so O2 moves out of erythrocytes down conc gradient
- once first O2 molecule released by haemoglobin, molecule again changes shape, becoming easier to remove remaining O2 molecules (haem's affinity for oxygen decreases)

27

Describe an oxygen dissociation curve.🌟

- helps understand how blood carries + releases O2
- percentage saturation haemoglobin in blood plotted against partial pressure of O2
- shows affinity of haemoglobin for oxygen
- curve levels out at highest partial pressure of O2, as all haem groups are bound to oxygen, so haemoglobin = fully saturated

28

Describe how carbon dioxide is transported around the body.🌟

- 5% dissolved directly in blood plasma
- 10-20% combined directly w/ Hb (carbominohaemoglobin), but this does not interfere w/ oxygen transport as CO2 carried by globin protein, NOT haem
- 75-85% transported in form of hydrogen carbonate ions (HCO3-)

29

Explain the Bohr effect, and how it affects an oxygen dissociation curve.🌟

- H+ ions compete for space on Hb
- when pCO2 (partial pressure of CO2) = high, H+ ions displace O2, causing O2 to be released
- if more CO2 produced, greater release of O2 will occur, so useful in repairing tissues

Bohr effect: makes oxygen dissociation curve shift to right to show more O2 being unloaded, so lower percentage saturated.

30

Describe how 75-85% of carbon dioxide is transported in the form of hydrogen carbonate ions (HCO3-).

- 95% of CO2 diffuses from body cells in erythrocytes (other 5% directly into plasma)
- enzyme carbonic anhydrase catalyses reaction of CO2 w/ H2O to form H2CO3 (carbonic acid)
- carbonic acid (H2CO3) dissociates into H+ and HCO3- ions
- hydrogen carbonate ions (HCO3-) diffuse out of erythrocyte in exchange for Cl- (chloride ions)
- oxyhaemoglobin dissociates under influence of H+ ions as H+ ions want to bond w/ haeomoglobin, so haemoglobin gives up O2 for it to bond w/ H+.
- oxygen released into blood plasma.