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Biology > 8 - Transport in animals > Flashcards

8 - Transport in animals Flashcards

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1
Q

the need for specialised transport systems in animals

A
  • metabolic demands of multicellular animals are high so diffusion over the long distances is not enough to supply cells
  • SA:V gets smaller as multicellular organisms get bigger so the amount of surface area to absorb substances becomes relatively smaller
  • molecules like hormones and enzymes may be made in a different area than they are needed
  • products of digestion in one organ system is needed to be transported to every cell for cell metabolism
  • waste products of metabolism need to be removed from cells and transported to excretory organs
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2
Q

types of circulatory systems

A

open
closed
-> single closed
-> double closed

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3
Q

open circulatory system

A
  • few blood vessels that contain the transport medium
  • it is pumped from the heart into the body cavity
  • the open body cavity is called the haemocoel
  • here transport medium is under low pressure and come in direct contact with the cells and exchange
  • medium returns to the heart by and open ended vessel
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4
Q

what is haemolymph

A

insect blood
- it doesn’t carry O2 or CO2 but food and nitrogenous waste and the immune system
- steep diffusion gradients cannot be maintained and the amount of haemolymph cannot be controlled

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5
Q

closed circulatory system

A
  • blood is enclosed in vessels and doesn’t come in direct contact with the cells of the body
  • heart pumps the blood under pressure and quickly, blood directly returns to the heart
  • substances leave and enter by diffusion through the walls of the blood vessels
  • amount of blood can be controlled by vaso dilation/constriction
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6
Q

single closed circulatory systems

A
  • blood flows through the heart and is pumped out to travel around the body before returning to the heart
  • blood travels only once through the heart in a complete circulation
  • blood passes through two sets of capillaries
    -> first it exchanges O2 and CO2
    -> in the second it substances are exchanged between blood and the cells
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7
Q

downside of single circulatory system

A
  • blood passes through two sets of capillaries
  • so blood pressure drops very low and blood returns to the heart slowly
  • this limits the activity of the animals
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8
Q

double closed circulatory system

A
  • blood is pumped from the heart to the lungs to pick up O2 and unload CO2 and it returns to the heart
  • blood flows through the heart and is pumped out to travel around the body before returning to the heart
  • in one circuit blood travels through the blood twice
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9
Q

arteries

A
  • carry blood away from the heart, usually oxygenated (apart from pulmonary artery and umbilical artery)
  • blood is under high pressure compared to blood in veins
  • contain elastic, smooth muscle and collagen
  • elastic fibres: withstand the force of the blood and stretch to take the larger vol of blood. In between contractions fibres recoil and return to original length.
  • has endothelium is smooth so blood flows easily
  • arterioles link arteries and capillaries
  • smooth muscle in arterioles contract the vessel and prevents blood into a capillary bed (vasoconstriction, vasodilation)
  • There are no valves in arteries
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10
Q

Arterioles

A
  • Arterioles carry blood from arteries to capillaries.
  • Arterioles are very similar to arteries. They are different in that they are smaller in diameter and have a thinner muscle layer and lumen.
  • The muscle layer is thicker and elastic layer is thinner than in arteries. The muscle layer is thicker so that the movement of blood into the capillaries can be controlled, and the elastic layer is thinner because blood pressure is lower in the arterioles
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11
Q

Structure of Capillaries

A
  • Capillaries exchange substances between the blood and body tissues. They are the smallest of the blood vessels.
  • Capillary walls are just one cell thick. They are made up of a single layer of endothelial cells which allows for rapid diffusion of substances.
  • There are many capillaries throughout the body and they are highly branched. This means that there is a large surface area for the exchange of substances and that all cells are very close to a capillary.
  • Capillaries are extremely narrow. Red blood cells are flattened against the side of the capillary because they are so narrow. This decreases the diffusion distance between the red blood cells and the cells that need oxygen, increasing the rate of diffusion.
  • Small spaces are left between the endothelial cells that make up the capillary wall. These spaces allow white blood cells to leave the capillaries and destroy infections in tissues.
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12
Q

capillaries are adapted for their role

A
  • provide a very large SA for the diffusion of substances in ad out of the blood
  • cross section area is always greater than the arteriole supplying them so the rate of blood flow falls. This slow movement of blood through the capillaries gives more time for the exchange of materials by diffusion
  • walls are a single endothelial cell thick, giving a vert thin layer for diffusion
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13
Q

veins

A
  • Veins transport deoxygenated blood from the body back to the heart.
  • The muscle and elastic layers are relatively thin. The muscle layer is thin because constriction isn’t needed to control the flow of blood to the tissues as veins take blood back to the heart. The elastic layer is thinner because the blood is transported slowly and under low pressure, so the veins won’t burst.
  • A thick wall isn’t needed because the pressure within the veins is too low for them to be at risk of bursting.
  • Veins have valves. As blood pressure in the veins is so low, the valves ensure that blood doesn’t flow backwards.
    -They have a wide lumen. This maximises the volume of blood that is carried
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14
Q

venules

A

-Larger than capillaries but smaller than veins.
-Blood travels from capillaries into venules, which then branches back into the veins ready to lead towards the heart.
-Venules have thinner walls than arterioles.
-They are porous in order to allow fluid and blood to easily move through their walls
‘- little smooth muscle

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15
Q

how does blood under low reassure get back to the heart

A
  • majority of veins have one-way valves at intervals. These are flaps that open when blood passes and closes when blood flows backwards
  • larger veins run between big, active muscles in the body, like arms and legs. When muscles contract they squeeze the veins, forcing the blood towards the heart.
  • breathing movements of the chest acts as a pump . The pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart
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16
Q

functions of the blood

A
  • O2 to CO2 the respiring cells
  • digested food from the small intestines
  • nitrogenous waste f=products from the cells to the excretory organs
  • hormones
  • food molecules from the storage compounds to the cells that need them
  • platelets to damaged areas
  • cells and antibodies involved in the immune response
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17
Q

Blood components

A
  • plasma (makes up 55%)
    -> glucose, amino acids, mineral ions, hormones and large plasma proteins (albumin, fibrinogen and globulins)
    -> red blood cells
    -> white blood cells
    -> platelets
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18
Q

platelets

A
  • fragments are large cells called megakaryocytes found in the red bone marrow, and are involved in the clotting mechanism
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19
Q

plasma proteins

A

albumin - important for maintaining the osmotic potential of the blood
fibrinogen - important in blood clotting
globulins- involved in transport and the immune system

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20
Q

Hydrostatic pressure

A
  • the pressure created by water in an enclosed system
  • The hydrostatic pressure in tissue fluid formation is the blood pressure, generated by the contraction of the heart muscle
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21
Q

Oncotic pressure - link to tissue fluid formation

A

the tendency of water to move into the blood by osmosis as a result of the plasma proteins

  • Plasma proteins lower the water potential within the blood vessel, causing water to move into the blood vessel by osmosis
  • plasma proteins cant go through fenestrations
22
Q

At the arterial end -tissue fluid formation

A
  • the hydrostatic pressure is greater than the osmotic pressure so the net movement of water is out of the capillaries into the tissue fluid by osmosis
  • this surrounds the spaces between cells
23
Q

tissue fluid composition

A
  • has the same composition s plasma, without the red blood cells and plasma proteins
  • diffusion takes place between the blood and cells through tissue fluid
24
Q

At the venous end - tissue fluid formation

A
  • the hydrostatic pressure within the capillary is reduced due to increased distance from the heart and the slowing of blood flow as it passes through the capillaries
  • At the venous end the osmotic pressure is greater than the hydrostatic pressure and water begins to flow back into the capillary from the tissue fluid

-Roughly 90 % of the fluid lost at the arterial end of the capillary is reabsorbed at the venous end

-The other 10 % remains as tissue fluid and is eventually collected by lymph vessels and returned to the circulatory system

25
Q

Formation of lymph

A
  • Some tissue fluid re-enters the capillaries while some enters the lymph vessels
  • it drains into blind ended tubes called lymph capillaries
  • it has similar composition to plasma, but with less oxygen and nutrients
  • it contains fatty acids that have been absorbed from the small intestine
  • fluid is transported by contracting muscles and they have valves
  • lymph returns back to the blood into the right and left subclavian vein
  • there are lymph nodes that contain lymphocytes (produce antibodies). they intercept bacteria and debris in the lymph and are ingested by phagocytes from the nodes
26
Q

Describe three ways in which the composition of tissue fluid is different to the composition of plasma.

A

In plasma there is:
A higher concentration of glucose; [1 mark]
A higher concentration of glycerol and fatty acids; [1 mark]
A higher concentration of amino acids; [1 mark]
A higher concentration of plasma proteins; [1 mark]
A lower water potential; [1 mark]
A higher oxygen concentration; [1 mark]
A lower carbon dioxide concentration; [1 mark]
In tissue fluid there is:
A higher concentration of the substances secreted by cells e.g. insulin; [1 mark]

27
Q

how are erythrocytes adapted for there function

A
  • biconcave - has a larger surface area than a disc for faster diffusion. And helps them pass through narrow capillaries
  • formed continuously in the red bone marrow
  • mature ones have no nuclei to maximise the amount of haemoglobin can fit
28
Q

haemoglobin

A
  • a large, conjugated protein made of 4 peptide subunits

-Each molecule of haemoglobin contains four haem groups, each able to bond with one molecule of oxygen

-This means that each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms in total

29
Q

what does the binding of O2 to haemoglobin form

A
  • oxyhaemoglobin
  • oxygen binds loosely to haemoglobin (ligand substitution)

Hb + 4O2 -> Hb(O2)4

30
Q

Carrying oxygen

A
  • [O2] in the alveoli is high but in the blood of the capillaries it is low (steep conc grad)
  • O2 moves into RBC and binds with Hb
    • as soon as one O2 binds to Hb, the molecule changes shape, making it easier for the next one to binf (Positive cooperativity)
  • when RBC reach body cells [O2] is low there, so O2 moves out of RBC down a conc grad.
  • once the first O2 leaves, it becomes easier to remove the remaining O2 as the molecule changes shape
31
Q

explain the oxygen dissociation curve

A

x-axis : pO2
y-axis: %saturation of Hb with O2

-The oxygen dissociation curve shows the rate at which oxygen associates, and also dissociates, with haemoglobin at different partial pressures of oxygen (pO2)

a) at low pO2, few haem groups are bound to O2, so haemoglobin does not carry much O2
b) at higher pO2, more haem groups are bound to O2, making it easier for more O2 to be picked up
c) the haemoglobin becomes saturated at very high pO2 as all haem groups become bound

32
Q

The effect of CO2 on Hb saturation

A
  • as PCO2 rises, Hb gives up oxygen mare easily
  • this is called the Bohr effect
    -> in active tissue with a high pCO2, Hb gibes up O2 more readily
    -> in the lungs where pCO2 is low, oxygen binds to Hb easily
33
Q

Fetal haemoglobin

A
  • The haemoglobin of a developing foetus has a higher affinity for oxygen than adult haemoglobin
  • This is vital as it allows a foetus to obtain oxygen from its mother’s blood at the placenta
  • Fetal haemoglobin can bind to oxygen at low pO2
  • On a dissociation curve graph, the curve for foetal heamoglobin shifts to the left of that for adult haemoglobin
    ->This means that at any given partial pressure of oxygen, foetal haemoglobin has a higher percentage saturation than adult haemoglobin
34
Q

what does saturated Hb mean

A

when all of its oxygen binding sites are taken up with oxygen; so when it contains four oxygen molecules

35
Q

Partial pressure of oxygen refers to

A

the pressure exerted by oxygen within a mixture of gases; it is a measure of oxygen concentration

36
Q

ways CO2 is transported from the tissues to the lungs

A
  • 5% is carried dissolved in the plasma
  • 10-20% is combined with amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin
  • 75-85% is converted into hydrogen carbonate ions (HCO3-) in the cytoplasm of the RBC

most CO2 is transported as HCO3-

37
Q

HCO3- as a way to transport CO2

A
  • CO2 reacts slowly with water to form carbonic acid, the acid then dissociates to form H= and hydrogen carbonate ions in the cytoplasm of RBC

CO2 + H2O <=> H2CO3 <=> H+ + HCO3-

  • this reaction is catalysed by the enzyme carbonic anhydrase to form carbonic acids
  • HCO3-moves out of the RBC into the plasma by diffusion(down a conc grad)
    -chloride ions move into RBCs to balances the electrical charge of the cell (chloride shift)
  • By removing HCO3- the RBC maintain a steep conc grad for CO2 to diffuse into from respiring tissue
  • when blood reaches lungs where [CO2] is low, carbonic anhydrase catalyses the reverse reaction, breaking it don into CO2 and H2O
    -> HCO3- diffuse back into RBC and reacts with H+ to form H2CO3. This is broken down into CO2 and H2O and diffuses into the lungs and chloride ions move out of RBC
  • Hb acts as a buffer and accepts free hydrogen ions and forms haemoglobinic acid
38
Q

The heart

A
  • consists of two pumps
  • deoxygenated blood enters in the right side, and pumps to the lungs
  • oxygenates blood from the lungs enters in the left side and travels to the body
  • made of cardiac muscle which contracts in a regular rhythm. it doesn’t get fatigued lie skeletal muscle
  • coronary arteries supply the muscle with oxygenated blood
  • surrounded by inelastic pericardial membranes which prevents the heart from over-distending the blood
39
Q

Heart structure

A

-The heart is divided into four chambers. The two top chambers are atria and the bottom two chambers are ventricles
-The left and right sides of the heart are separated by a wall of muscular tissue, called the septum. The portion of the septum which separates the left and right atria is called the interatrial septum, while the portion of the septum which separates the left and right ventricles is called the interventricular septum
-The septum is very important for ensuring blood doesn’t mix between the left and right sides of the heart

40
Q

Valves in the heart

A

-The right atrium and right ventricle are separated by the atrioventricular valve, which is otherwise known as the tricuspid valve

-The right ventricle and the pulmonary artery are separated by the pulmonary valve

-The left atrium and left ventricle are separated by the mitral valve, which is otherwise known as the bicuspid valve

-The left ventricle and aorta are separated by the aortic valve

-There are two blood vessels bringing blood to the heart; the vena cava and pulmonary vein

-There are two blood vessels taking blood away from the heart; the pulmonary artery and aorta

41
Q

pathway of blood in the heart

A
  • Deoxygenated blood returns to the heart from the body through the superior and inferior vena cava at low pressure.
  • The blood enters the right atrium. The atria has thin walls and as it fills with blood, pressure builds up until the tricuspid valve opens to let blood into the right ventricle
  • when both the atrium and ventricle are full, the atrium contracts, forcing the blood into the right ventricle, stretching its walls.
  • The right ventricle contracts, closing the tricuspid valve and opening the semilunar valve.
  • Blood is pumped through the semilunar valve into the pulmonary artery, which carries it to the lungs for oxygenation.
  • In the lungs, oxygen is picked up by red blood cells, and carbon dioxide is released.
  • Oxygenated blood returns to the heart via the pulmonary veins and enters the left atrium.
  • as the pressure in the left atrium builds, the bicuspid valve opens, allowing blood to flow into the left ventricle.
  • When both the ventricle and atria are filled, the atrium contracts. Foring all the blood in the left ventricle
  • The left ventricle contracts, closing the tricuspid valve and opening the semilunar valve.
  • Blood is pumped into the aorta, which carries it to the rest of the body.
  • This cycle repeats with each heartbeat, maintaining circulation throughout the body
42
Q

why is the left side of the heart thicker than the right

A
  • Has to produce sufficient force to overcome the resistance of the aorta and arterial systems of the whole body, and mover the blood under pressure to all extremities of the body
43
Q

Diastole

A
  • heart relaxes
  • atria and ventricles fill, volume and pressures build, The pressure in the arteries at a minimum
44
Q

Systole

A

the atria contracts followed by the ventricle
- pressure in the heart increases dramatically and blood is forced out of the right side of the heart to the lungs and from the left side to the body
- the volume and pressure of the blood in the heart are low at the end of systole, and pressure in the arteries is at a maximum

45
Q

Heart sounds

A

lub-dub
lub; when blood is forced against the atrio-ventricular valves as the ventricles contract

dub: backflow of blood closes the semilunar valves in the aorta and pulmonary artery as ventricles relax

46
Q

cardiac muscle is ___

A

myogenic
- it has its own intrinsic rhythm

47
Q

The basic rhythm of the heart

A
  • a wave of electrical excitation begins in the pacemaker SAN, causing the atria to contract and initiating a heartbeat, a layer of non-conducting tissue prevents the excitation passing directly to the ventricles
  • the electrical activity from the SAN is picked AVN. It imposes a delay before stimulating the bundle of His, a bundle of conducting tissue made up of fibres (Purkyne fibres), which penetrate through the septum between the ventricles
  • the bundle of His splits into two branches and conducts the wave of excitation to the apex of the heart
  • at the apex of the Purkyne fibres spread out through the walls of the ventricles on both sides. The spread of excitation triggers the contraction of the ventricles, starting at the apex. Contraction starting at the apex allows more efficient emptying of the ventricles
48
Q

Tachycardia

A

HB is very rapid, over 100bpm

49
Q

Bradycardia

A

HR slows down to below 60bom

50
Q

ectopic heartbeat

A

extra HB that are out of the normal rhythm

51
Q

atrial fibrillation

A

abnormal rhythm of the heart

Biology (24 decks)

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