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Transport in animals Flashcards

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1
Q

Single Circulatory system (fish)

A
  • DEOXYGENATED blood is pumped by the heart through blood vessels to the GILLS.
  • In the gills, the blood passes through narrow CAPILLARIES.
  • OXYGEN diffuse from the water into the blood.
  • OXYGENATED blood now passes from the gills through blood vessels to the BODY TISSUES.
  • The blood then passes through CAPILLARIES where oxygen diffuse from the blood into CELLS.
  • The DEOXYGENATED blood now RETURNS in blood vessels to the HEART.
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2
Q

The role of the CAPILLARIES in a single circulatory system

A
  • When the blood leaves the heart , the PRESSURE of the blood is HIGH and is moving RAPIDLY.
  • However, the blood passes through TWO SETS of capillaries .
  • These DECREASE the flow of blood and REDUCE the PRESSURE.
  • This LIMITS how rapidly oxygen can be delivered to the body cells.
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3
Q

Double Circulatory System (mammals)

A
  • DEOXYGENATED blood is pumped under HIGH PRESSURE from the heart to the LUNGS.
  • In the lungs, the blood passes through CAPILLARIES, reducing the speed and pressure.
  • OXYGEN diffuses from the air into the blood.
  • The OXYGENATED blood now returns back to the heart which pumps the blood at HIGH PRESSURE to the rest of the BODY.
  • As it passes through the body tissues ,the blood passes through CAPILLARIES and OXYGEN diffuses to the body cells.
  • The LOW PRESSURE , DEOXYGENATED blood now makes it way back to the heart to be pumped again.
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4
Q

Advantages of a Double Circulatory System

A
  • The blood moves through the heart TWICE
  • This ensures the blood moves to the tissues RAPIDLY and under HIGH PRESSURE.
  • This allows oxygen delivery to be more EFFICIENT.
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5
Q

CLOSED circulatory system

A
  • In fish and mammals
  • The blood is contained in BLOOD VESSELS when transported.

ADVANTAGES:

  • allows the blood to move relatively RAPIDLY , due to higher pressure.
  • rapid delivery of oxygen and nutrients and rapid removal of waste products.
  • Transport is independent of body movements.
  • The AMOUNT of blood passing to different organs can be CONTROLLED by constricting or dilating the blood vessels.
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6
Q

OPEN circulatory system

A
  • In insects
  • DO NOT contain blood
  • Insects contain a fluid called HAEMOLYMPH which carries nutrients but it does not carry oxygen.
  • Haemolymph is pumped out of the heart and passes DIRECTLY into the body cavity called HAEMOCOEL.
  • Molecules are transported between the haemolymph and the body cells.
  • The haemolymph then makes its way back to the heart.
  • Haemolymph is NOT carried in vessels therefore is apart of an open circulatory system.
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7
Q

The cardiac cycle

A

The control and coordination of the heart.

3 Stages:
- Atrial systole
- Ventricular systole
- Diastole

systole ~ CONTRACT
diastole ~ RELAX

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8
Q

1 Atrial systole

A
  • The atria CONTRACT
  • This causes the pressure in the atria to INCREASE.
  • The AV valves open, so the blood flows down into the VENTRICLES.
  • This causes the pressure of the ventricles to INCREASE.
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9
Q

2 Ventricular systole

A
  • The ventricles CONTRACT
  • The pressure in the ventricles INCREASES (more in the left side).
  • this is because the pressure in the ventricles is now GTREATER than in the atria.
  • The AV valves shut
  • The SEMILUNAR valves in the aorta OPEN because pressure in the ventricles is greater than in the aorta.
  • Blood now flows out of the ventricles through the aorta.
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10
Q

3 Diastole

A
  • The pressure in the ventricles DECREASES as the blood is LEAVING.
  • At a certain point, the pressure in the left ventricle is LESS than in the aorta.
  • Now the SEMILUNAR valves close preventing blood being drawn back into the left ventricle
  • While the ventricle was CONTRACTING, the left atrium was RELAXING.

-This means that blood was flowing into the atrium from the vena cava and pulmonary vein.

  • The ventricle now starts to RELAX, causing pressure in the ventricle to FALL, eventually below the pressure in the atria.
  • This causes the AV valves to open and blood flows into the ventricle from the atrium.
  • As the atria and ventricles refill , the heart is now ready to enter the next cardiac cycle.
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11
Q

Blood volume during the cardiac cycle

A
  • INCREASES as it is pumped into the left ventricle when the left atrium contracts.
  • DECREASES when the left ventricle contracts as blood passes out the aorta.
  • INCREASES AGAIN as the left ventricle relaxes and blood flows down from the left atrium.
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12
Q

Initiation and Coordination of the action of the heart

A
  • The heart beat is initiated from WITHIN the heart itself.
  • The heart does not need an EXTERNAL SIGNAL in order to beat.
  • Because the heart triggers its own beat , it is described as MYOGENIC.
  • There are two nodes in the heart:
    • Sino-atrial node
    • Atrio-ventricular node
  • Electrical impulses are sent from the SAN to the AVN coordinating heart muscle contractions.
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13
Q

The role of the SAN

A
  • In the wall of the RIGHT ATRIUM there is a group of specialised cells called the SINO-ATRIAL NODE.
  • This is also called the PACEMAKER.
  • The cells in the SAN DEPOLARISE (they become electrically excited.

-This triggers a wave of electrical excitation to spread across the ATRIA.

  • This causes the atria to contract ~ ATRIAL SYSTOLE
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14
Q

Why cant the wave of electrical excitation crossing the atria pass DIRECTLY down to the ventricles?

A
  • The ventricles are separated from the atria by a layer of NON-CONDUCTING TISSUE.
  • This layer of tissue will NOT pass the electrical excitation through it.
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15
Q

The role of the AVN

A
  • Between the ATRIA there is another group of specialised cells called the ATRIO-VENTRICULAR NODE.
  • The AVN is connected to the conducting fibres called PURKYNE FIBRES.
  • The AVN detects the electrical excitation passing over the atria.
  • After a SHORT DELAY, the AVN then transmits the electrical excitation down the PURKYNE FIBRES.
  • This electrical excitation causes the ventricles to contract from the apex upwards ~ VENTRICULAR SYSTOLE.
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16
Q

The purkyne fibres

A

-The AVN is connected to these conducting fibres .

  • Initially these fibres are bundled together so are described as the BUNDLE OF HIS.
  • However , this then BRANCHES , with purkyne fibres running down to the APEX or BASE of the heart and then up the walls of the VENTRICLES.
  • Located in the SEPTUM
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17
Q

Why do the ventricles contract from the apex upwards?

A

To ensure that the MAXIMUM VOLUME of blood is pumped out of the ventricles.

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18
Q

Why is there a slight delay before the AVN triggers the electrical excitation down the purkyne fibres?

A

To ensure that the ventricles contract AFTER the atria have contracted.

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19
Q

Polarisation and depolarisation

A
  • The MEMBRANES around the two nodes, allow a CHARGE to be maintained across the membrane.
  • At REST the nodes become POLARISED.
  • A POSITIVE charge builds up on the INSIDE of the node , and a NEGATIVE on the outside.
  • This is caused by IONS building up.
  • When CONTRACTION occurs, the nodes are DEPOLARISED.
  • Positively charged ions move out oof the nodes STIMULATING a move in electrical electricity in the heart.
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20
Q

An electrocardiogram

A
  • By attaching ELECTRODES to the surface of the skin, scientists can analyse the ELECTRICAL ACTIVITY of the heart.
  • The resulting TRACE is called an electrocardiogram or an ECG.
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21
Q

Calculating the Heart Beats Per Minute.

A
  • Pick an interval on the graph which begins and ends at equivalent points in a heart beat.

60/ value of ones space x number of spaces in that interval

x number of peaks in that interval

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22
Q

Bradycardia

A
  • When the heart rate drops below 60 BPM.

ATHLETIC TRAINING:
This increases the STROKE VOLUME of the heart meaning the heart pumps a greater blood volume per beat, so the number of BPM decreases.

DISEASE:
May require an artificial pacemaker.

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23
Q

Tachycardia

A
  • When the heart rate is greater than 100 BPM.

SHORT TERM:
-Fear
-Panic
-Exercise

LONG TERM:
- Caused by problems with the sinoatrial
node or other medical conditions.
- Requires surgery or drugs

24
Q

Ectopic heart beat

A
  • An EXTRA heart beat that is not part of the hearts usual rhythm.
  • The heart contracts again BEFORE the first contraction has finished.
  • This is followed by a SHORT PAUSE before the normal rhythm continues.
  • Relatively COMMON and does not pose any health risks.

-However, if experienced more frequently, this may indicate a more serious heart condition.

25
Q

Atrial fibrillation

A
  • IRREGULAR waves of electrical excitation pass over the atria.
  • This causes the atria to contract RANDOMLY & RAPIDLY. (up to 100BPM)
  • In most cases, the electrical excitation is not transmitted to the VENTRICLES.
  • This means the ventricles contract LESS FREQUENTLY than the atria.
  • Because the normal rhythm of the heart is disrupted it is considered a type of ARRHYTHMIA.
26
Q

Arteries : STRUCTURE related to FUNCTION

A

FUNCTION ~ carry blood AWAY from the heart at high pressure.

THICK WALL:
- allows the artery to withstand high pressure of the blood.
- The wall consists of several layers.

OUTER LAYER ( tunica adventitia)
- Rich in the fibrous protein collagen.
- Collagen plays a structural role, strengthening the artery wall against the pressure of blood.

SECOND LAYER ( tunica media)
- Contains smooth muscle.
- This contracts , narrowing the diameter of the arteries.
-This allows the body to control how much blood flows to different organs.
- Smaller arteries tend to contain a greater proportion of smooth muscle compared to larger arteries as they play a bigger role in controlling blood flow.

THIRD LAYER ( tunica intima)
- Rich in elastic fibres which contain the protein elastin which can stretch.
- When the elastic fibres recoil it helps to keep the blood moving smoothly forward on between contractions of the heart.

CENTRAL CAVITY ~ LUMEN:
- Where the blood flows through
- Lined with a thin layer of endothelial cells.
- This presents a very smooth surface to reduce friction as the blood flows through.

27
Q

Arterioles

A
  • Their walls contain the SAME layers as arteries but they differ in relative THICKNESS.
  • Have SPHINCTER MUSCLE

THINNER collagen & elastic layer:
- This is because the blood pressure is lower than in arteries and the effect of the pulse is weaker.

THICKER smooth muscle layer:
- This is because they are involved in controlling the amount of blood passing through the capillaries.

VASOCONSTRICTION ~ when smooth muscle contacts and blood flow in capillaries is reduced.

VASODILATION ~ when smooth muscle relaxes and blood flow in capillaries increases.
This takes place when an organ requires an increased amount of carbon dioxide.

28
Q

How has the STRUCTURE of CAPILLARIES evolved to maximise the rate of DIFFUSION?

A

EXTENSIVE BRANCHING:
- Provides a massive SA for the exchange of materials.

EXTREMELY THIN WALL:
- Consists of a single layer of endothelial cells.
- Creates a short diffusion distance between the blood and the cells nearby .

LUMEN ONLY SLIGHTLY LARGE THAN THAT OF A RED BLOOD CELL:
- When red blood cells pass through they are pressed against the capillary wall.

  • This reduces the distance for the diffusion of oxygen from red blood cells to the tissue cells.
  • This also means red blood cells move single file, slowing down their movement which increases the time available for molecules to diffuse in and out of the blood.

SMALL GAPS BETWEEN THE ENDOTHELIAL CELLS:
- Tissue fluid,, which bathes cells and provides essential molecules, can pass out of the blood.

  • Also allow white blood cells to leave through the bloodstream.
29
Q

BLOOD ~ the two main parts

A

CELLS:
- Red blood cells (erythrocytes) ~ transport oxygen.
- White blood cells (leucocytes) ~ play a role in the immune system.
- Platelets ~ cell fragments which are involved in blood clotting.

BLOOD PLASMA:
- The blood cells are suspended in this watery solution.

Contains a range of dissolved molecules:
- glucose
- amino acids
- mineral ions , Na+

  • Contains dissolved OXYGEN which diffuses out of the red blood cells.
  • Contains PROTEINS, for example ALBUMIN, which are referred to as PLASMA PROTEINS.
30
Q

Tissue fluid

A

THE FLUID SURROUNDING THE CELLS AND TISSUES.

  • In the CAPILLARIES, tissue fluid passes out of the blood and bathes the tissue cells.
  • The tissue fluid then LEAVES the blood at the parts of the capillary which are near the ARTERY (arterial end).
  • Tissue fluid transfers molecules such as OXYGEN and GLUCOSE to the tissue cells, whilst WASTE PRODUCTS such as carbon dioxide from the tissue cells pass into the tissue fluid.
  • The tissue fluid then returns back to the bloodstream at the parts of the capillary which are near the VEIN (venous end).

IN CONCLUSION:

Tissue fluid is forced out of the blood at the ARTERIAL END of the blood capillary and returns back to the blood at the VENOUS END of the blood capillary.

31
Q

HYDROSTATIC pressure

A

The pressure that a fluid exerts when pushing against the sides of a vessel or container.

  • At the arterial end, the blood has just passed through an ARTERY and a ARTERIOLE.
  • This means the blood is still under relatively HIGH pressure.
  • This is known as HYDROSTATIC PRESSURE which tends to force fluid out of the blood and into the tissue.
32
Q

ONCOTIC pressure

A

The pressure created by the OSMOSIS effects of the solutes.

  • Plasma proteins are HYDROPHILLIC , so they lower the water potential of the blood plasma.
  • This means there is a tendency for water to move BACK into the blood by osmosis.
33
Q

At the ARTERIAL END of the capillary …

A

Hydrostatic pressure > Oncotic pressure

  • This means that tissue fluid is FORCED OUT .
  • Leaves through the GAPS between the ENDOTHELIAL CELLS.
  • This process is known as :
    ULTRAFILTRATION
  • Blood cells and plasma proteins are TOO LARGE to leave, so remain in the blood plasma.
34
Q

At the VENOUS END of the capillary …

A

Hydrostatic pressure < Oncotic pressure

  • A large amount of WATER has LEFT the blood.
  • However, the oncotic pressure is still high due to the PLASMA PROTEINS in the blood plasma.
  • This causes water to move BACK into the blood by OSMOSIS.
35
Q

The LYMPHATIC SYSTEM

A
  • 90% of the tissue fluid is REABSORBED back into the blood.
  • The remaining 10% drains into a series of blind-ended vessels called LYMPH CAPILLARIES.
  • These connect into larger lymph vessels, forming the lymphatic system.
  • LYMPH FLUID moves along when lymph vessels are SQUEEZED by nearby skeletal muscles.
  • VALVES in the lymph vessels help to keep the lymph fluid moving forward.
  • Eventually, the lymph fluid RETURNS to the bloodstream via blood vessels under the COLLAR BONE.
  • The lymphatic system also plays a role in IMMUNITY.
36
Q

ADAPTIONS of red blood cells (erythrocytes)

A

BIOCONCAVE STRUCTURE:
- Gives them a large surface area to volume ratio.
- Allows oxygen to diffuse in and out rapidly

HAEMOGLOBIN:
- Contain around 300 million molecules of these oxygen carrying proteins.

NO NUCLEUS:
- They do initially, but it is lost before the erythrocytes enter circulation.

  • The absence of a nucleus means that more of the erythrocytes volume is available to carry haemoglobin.
37
Q

STRUCTURE of haemoglobin

A
  • FOUR polypeptide chains.
  • Each polypeptide chain is bound to a prosthetic group HAEM, which contains the IRON ion Fe2+.
  • Each of the Fe2+ groups in the haem molecules can combine with ONE molecule of OXYGEN.
  • As there are four haem groups, one haemoglobin molecule can combine with FOUR molecules of oxygen.
  • When haemoglobin binds to oxygen it is now called OXYHAEMOGLOBIN.

Hb + 4O2 —————————– Hb(O2)4
( reversible reaction)

38
Q

Oxygen dissociation curve

A

A way to measure the amount of oxygen that combines with haemoglobin.

Y AXIS ~ % saturation of haemoglobin with
oxygen.

X AXIS ~ partial pressure of oxygen (KPa)

The curve is S shaped ~ sigmoid curve.

39
Q

Explaining the shape of the SIGMOID CURVE.

A

NO oxygen molecules bound :

  • The haem groups have a LOW AFFINITY for oxygen molecules.
  • This means it takes a relatively LARGE PARTIAL PRESSURE of oxygen for the first oxygen to bind to a haem group.

When ONE oxygen molecule binds :

  • The QUATENARY STRUCTURE of the haemoglobin changes.
  • This INCREASES the affinity of the haem groups for oxygen.

Binding MORE oxygen molecules , only requires a relatively small increase in the oxygen partial pressure :
POSITIVE COOPERATIVITY

FOURTH haem group:
- Only binds to oxygen at a fairly HIGH partial pressure.
- As 3 of the 4 haem groups have already been filled, the chances of an oxygen molecule COLLIDING with the fourth haem group is relatively LOW.

40
Q

Partial pressure of oxygen and the % saturation of haemoglobin with oxygen in the BODY.

A

ALVEOLI ~ the partial pressure of oxygen is HIGH and the haemoglobin in red blood cells is around 97% saturated.

BODY TISSUES ~ the partial pressure of oxygen DECREASES as the tissues are carrying out AEROBIC RESPIRATION.

  • At a certain point, one oxygen molecule UNLOADS from the haemoglobin which changes it QUATERNARY STRUCTURE.
  • This DECREASES the AFFINITY of the remaining haem groups.

ACTIVE TISSUE ~ the oxygen partial pressure will be even LOWER and TWO more oxygen molecules will rapidly unload from the haemoglobin.

  • The final oxygen molecule will unload if the oxygen partial pressure is EXTREMELY LOW.
  • Could take place in VERY ACTIVE TISSUE. E.g muscle tissue during very intense exercise.
41
Q

Affinity

A

How STRONGLY the oxygen is bound to the haemoglobin.

42
Q

The BOHR EFFECT

A
  • Aerobic respiration produces the gas CARBON DIOXIDE.
  • The effect of carbon dioxide is to SHIFT the whole oxygen dissociation curve tot he RIGHT.
  • This means carbon dioxide causes the oxygen AFFINITY of haemoglobin to DECREASE.
  • This causes the haemoglobin to UNLOAD its oxygen more EASILY.
43
Q

Effect of CARBON DIOXIDE in the LUNG and ACTIVE TISSUE.

A

LUNGS:
- Haemoglobin has a higher affinity for oxygen as the partial pressure of carbon dioxide is LOW.

  • This means haemoglobin has a high level of oxygen saturation.

ACTIVE TISSUE:
- The partial pressure of carbon dioxide will be HIGH.

  • This is because the active tissue ( e.g muscle tissue) is undergoing AEROBIC RESPIRATION.
  • This causes haemoglobin to have LOWER affinity for oxygen , allowing it to UNLOAD its bound oxygen more easily.
44
Q

The ROLE of CARBON DIOXIDE

A
  • In the blood, carbon dioxide can form the acidic molecule CARBONIC ACID.
  • Carbonic acid releases the HYDROGEN ION , H+ , which COMBINES with haemoglobin.
  • This causes the QUATENARY STRUCTURE of the haemoglobin molecule to CHANGE.
  • As a result, the haemoglobin has a LOWER affinity for oxygen allowing the haemoglobin molecule to UNLOAD its bound oxygen more EASILY.
45
Q

The DIFFUSION of oxygen from the MATERNAL blood to the FETAL blood.

A
  • In the PLACENTA, the fetal blood and the maternal blood pass CLOSELY to each other , but do not mix.
  • The maternal blood has a HIGHER level of OXYGEN than the fetal blood.
  • This causes oxygen to DIFFUSE cross the placenta and into the fetal blood.
46
Q

How is OXYGEN TRANSFER from the maternal blood to the fetal blood made more EFFICIENT?

A
  • On an oxygen dissociation curve, the curve for fetal haemoglobin is shifted to the LEFT compared to adult haemoglobin.
  • This means that fetal haemoglobin has a HGHER AFFINITY for oxygen than adult haemoglobin.
  • CARBON DIOXIDE from the fetus diffuses into the maternal blood, LOWERING the oxygen affinity of the maternal haemoglobin FURTHER.
  • This INCREASES the OXYGEN TRANSFER across the placenta from the maternal haemoglobin tot the fetal haemoglobin.
47
Q

Why is the oxygen affinity of fetal haemoglobin only SLIGHTLY GREATER than adult haemoglobin?

A

If fetal haemoglobin had a VEY HIGH oxygen affinity:

This could PREVENT the unloading of oxygen in the fetal tissues.

48
Q

How does the STRUCTURE of fetal haemoglobin DIFFER from the structure of maternal haemoglobin?

A
  • In the fetus, TWO of the polypeptide chains of haemoglobin is different compared to adult haemoglobin.
  • This is due to differences in GENE EXPRESSION in the fetus compared tot he adult.
  • This difference means that fetal haemoglobin has a HIGHER O2 AFFINITY.
49
Q

Transport of carbon dioxide

A
  • All cells produce carbon dioxide when they carryout AEROBIC RESPIRATION.
  • This carbon dioxide has to be transported in the BLOOD from actively respiring tissues to the lungs, where it is breathed out.

It is transported in THREE ways:
- Dissolved directly in the blood ~ 25%
- Carbaminohaemoglobin in red blood cells ~20%
- Hydrogencarbonate ions in blood plasma~ 75%

50
Q

The formation of: CARBAMINOHAEMOGLOBIN

A
  • In each polypeptide of a haemoglobin molecule, the first amino acid has a FREE amino group.
  • When carbon dioxide reacts with haemoglobin, it forms the compound carbaminohaemoglobin.
  • This is a reversible reaction.
  • When the blood passes through RESPIRING TISSUE , the level of carbon dioxide is HIGH and carbaminohaemoglobin FORMS.

-In the LUNGS , the level of carbon dioxide is LOW causing the carbaminohaemoglobin to BREAK DOWN, releasing carbon dioxide.

51
Q

The formation of :
CARBONIC ACID

A
  • When carbon dioxide reacts with water it forms the compound carbonic acid.
  • This is a REVERSIBLE REACTION and takes place SLOWLY.
  • Red blood cells contain the enzyme , CARBONIC ANHYDRASE which speeds up the reaction.
  • By converting CO2 into carbonic acid, the level of CO2 in the red blood cells is kept LOW, creating a STEEP concentration gradient for CO2.
  • This creates a HIGH RATE of DIFFUSION of CO2 into the red blood cells.
52
Q

The formation of the :
HYDROGEN CARBONATE ION

A
  • When carbonic acid is formed, it then dissociates or splits forming:
  • Hydrogen carbonate ion ( HCO3-)
  • The HYDROGEN ION (H+)
  • HCO3- diffuses out of the red blood cell to the blood plasma.
  • As it has a negative charge, a CHARGE IMBALANCE is created within the red blood cell.
  • To prevent this, a chloride ion (Cl-) diffuses into the red blood cell , CHLORIDE SHIFT.
53
Q

The formation of the :
HYDROGEN ION

A
  • The H+ ions could cause the pH of the blood to DECREASE,
  • To prevent this, haemoglobin acts as a BUFFER, binding to the H+ ions and forming:

HAEMOGLOBINIC ACID.

54
Q

STRUCTURE related to FUNCTION of veins

A

FUNCTION ~ carry blood BACK to the heart.

Unlike arteries, the blood in venules and veins is under LOW pressure and is NOT travelling in pulses.

THINNER WALLS:
- Do not have to withstand high blood pressure.

LARGER LUMEN :
- Carry a LARGER volume of blood compared to arteries.

THINNER SMOOTH MUSCLE & ELASTIC LAYER:
- blood does not travel in pulses so there is no elastic recoil.

ENDOTHELIAL CELLS in the internal lining of the lumen:
- Same as arteries
- creates a smooth surface which reduces friction between the blood and the wall of the vein.

55
Q

VALVES in veins

A
  • help to keep the blood moving in the FORWARD DIRECTION.
  • The blood in veins is moving BACK to the heart.
  • This means the blood may well be moving against GRAVITY, especially if the veins are in the legs or arms.
  • The problem is that the blood in veins is travelling SLOWLY and is under LOW pressure.
56
Q

What makes the blood in veins move back to the heart?

A

MUSCLES SQUEEZING:
- Many veins are found lying between skeletal muscles.
- when these muscle contract, they squeeze the veins lying between them.
- as veins have a thin wall they change shape.
- this squeezing forces the blood along

VALVES:
- if the blood moves forward , valves remain open.
- if the blood start to move backwards, valves shut.

PRESSURE OF THE CHEST CAVITY:
- when we inhale , the pressure of our chest cavity decreases.
- this helps the blood in the chest veins to move towards the heart.

57
Q

The LUB & DUPP sound

A

LUB ~ closing of the bicuspid valve

DUPP ~ closing of the semi-lunar valve

Biology (7 decks)

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