Transport in animals Module 3

Question 1

Reasons why multicellular organisms require transport systems?

Answer 1

Low surface area to volume ratio for diffusion
Too big of a distance too reach cells inside the organism via diffusion
High metabolic rate
Very active, so large amount of cells require a lot of oxygen and glucose quickly

Question 2

What type of circulatory system do fish have, and describe it?

Answer 2

Single circulatory system, blood only passes through heart once in complete cycle
The heart pumps blood to the gills (to pick up oxygen), and then to the rest of the body to deliver the oxygen in a single circuit

Question 3

What type of circulatory system do mammals have and describe it?

Answer 3

Double circulatory system, blood passes through the heart twice in a single circuit

Right side of the heart pumps blood to the lungs (to pick up oxygen), it then travels to the left side of the heart to be pumped to the rest of the body ( so travels more quickly), it then enters the right side again

Question 4

What type of circulatory system do all vertebrates (mammals and fish) have?

Answer 4

Closed circulatory system, blood is enclosed inside blood capsules

Question 5

What type of circulatory system do some invertebrates have, and what does this consist of?

Answer 5

Open circulatory system, blood isn’t enclosed in blood vessels all the time, instead it flows freely through the body cavity

The heart is segmented, it contracts in a wave starting from the back and pumping the blood into a single main artery

That artery opens up to the body cavity

The blood flows around the insects organs, gradually making it’s way back into the heart segments through a series of valves

Question 6

What does the circulatory system in insects transport?

Answer 6

Hormones and nutrients are transported

Not oxygen, this is done via the tracheal system

Question 7

What do arteries do and what are their properties?

Answer 7

Carry blood from the heart to the rest of the body
Their walls are thick and muscular and have elastic tissue stretch and recoil as the heart beats, which maintains the high pressure
The lining (endothelium) is folded allowing the artery to expand, helping maintain a high pressure
All arteries carry oxygenated blood, except pulmonary arteries which take blood to the lungs

Question 8

What do arterioles do and what are their properties?

Answer 8

Arteries branch off into arterioles, which are much smaller

Have smooth muscle which can expand or contract, thus controlling how much blood flows to the tissues

Question 9

What do capillaries do and what are their properties?

Answer 9

Arterioles branch off into capillaries which are the smallest of the blood vessels
Allow substances such as glucose and oxygen to be exchanged by cells and capillaries
One cell thick to increase diffusion

Question 10

What are venules?

Answer 10

Capillaries connect to form venules, which join together to form veins

Question 11

What do veins do and what are their properties?

Answer 11

Take blood back to the heart at low pressure, so have a wider lumen with very little muscular or elastic tissue
Contain valves to prevent the backflow of blood
Blood flow in veins is helped by the contraction of body cells surrounding them
All veins carry deoxygenated blood back to the heart, apart from the pulmonary vein

Question 12

What’s tissue fluid?

Answer 12

The fluid that surrounds cells in tissues, it’s made from substances which leave the blood plasma eg. nutrients oxygen and water (unlike blood as doesn’t contain red blood cells or proteins as too large too fit through the capillary wall)

Oxygen and nutrients go into the cells, and metabolic waste goes into the tissue fluid

Question 13

Describe pressure filtration in the capillary bed?

Answer 13

At the start of the capillary bed nearest the arteries the hydrostatic pressure inside the the capillaries is greater than the hydrostatic pressure in the tissue fluid.

The difference in hydrostatic pressure, forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid

As fluid leaves the hydrostatic pressure reduces in the capillaries and so the pressure is much lower at the end of the capillary bed near the venules

Oncotic pressure is present in the capillaries and is generated by plasma proteins, which lowers the water potential

Near the venule end of the capillaries water will re enter the capillaries via osmosis as it has a lower water potentia than the tissue fluidl, due to fluid loss and a high oncotic pressure

Question 14

What happens to the tissue fluid which doesn’t reenter the capillaries at the venule end of the capillary bed?

Answer 14

Drains into lymph vessels (capillaries are the smallest one) which take it into the lymphatic system where it’s now called lymph
Valves in the lymph vessel stop the lymph going backwards
Lymph gradually moves towards the main lymph vessels in the thorax, and return to the blood near the heart

Question 15

Blood contains red blood cells, white blood cells, platelets, proteins, water and dissolved solutes what does tissue fluid and lymph contain?

Answer 15

Tissue fluid:
Very few proteins and white blood cells
water
dissolved solutes

lymph:
White blood cells
water 
dissolved solutes
only antibody proteins

Question 16

Describe just structure wise the journey of blood through the heart?

Answer 16

Enters via either superior vena cava (top) or inferior vena cava (bottom)
Right atrium
atrioventricular valve
right ventricle
semi-lunar valve
pulmonary artery 
lungs
pulmonary veins
left atrium
atrioventricular valve
left ventricle
aorta

Question 17

How do the atrioventricular and semi-lunar valves in the heart prevent blood flowing the wrong way?

Answer 17

The valves only open one way
So if there’s high pressure behind a valve it’s forced open
If there’s high pressure in front of a valve it’s forced shut

Question 18

Describe the cardiac cycle?

Answer 18

1. Ventricles relax and atria contract:
   When the atria contract, their volume decreases and their pressure increases, pushing their blood into ventricles via the atrioventricular valves. There’s a slight increase in ventricular volume and pressure
2. Ventricles contract, atria relax:
   The ventricles contract (decreasing their volume) and increasing their pressure.
   The pressure become higher in the ventricles than in the atria, forcing the atrioventricular valves shut to prevent back-flow
   The high pressure in the ventricles opens up the semi-lunar valves, and blood is forced into the pulmonary artery and the aorta
3. Ventricles relax and atria relax:

The higher pressure in pulmonary and aorta causes the semi-lunar valves to close, preventing backflow.
The atria fill with blood increasing their pressure, due to higher pressure in vena cava and pulmonary vein.
As the ventricles continue to relax their pressure falls bellow that off atria, causing the atrioventricular valves to open and blood flows passively (without a contraction), into the ventricles from the atria

Cycle happens again

Question 19

What makes the sounds of the “lub” and “dub” of the heart?

Answer 19

Lub = atrioventricular valves closing
Dub = semi lunar valves closing

Question 20

Describe how cardiac muscle controls the regular beating of the heart?

Answer 20

Process starts in the sino-atrial node (SAN), which is in the wall of the right atrium

The SAN sends out regular waves of electrical activity which goes to the atrial walls

Causing the right and left atria to contract at the same time

A band of non conducting collagen tissue prevents the waves of electrical activity being passed directly from the atria to the ventricles

Instead these waves of electrical activity are transferred from the SAN to the atrioventricular node (AVN)

The AVN is responsible for passing the waves of electrical activity on to the bundle of His, but there’s a slight delay before the AVN reacts to make sure the ventricles contract after the atria have been emptied

The bundle of His, is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the right and left ventricle walls called the Purkyne tissue

The Purkyne tissue carries the waves off electrical activity to the muscular walls of the right and left ventricles, causing them to contract at the same time fr,om bottom up

Question 21

What’s an electrocardiograph measuring?

Answer 21

Records the electrical activity of the heart, as the heart depolaries when it contracts, and repolaries when it relaxes, so can be measured by having electrodes on the chest

Question 22

Describe one full heartbeat on a electrocardio graph?

Answer 22

Tiny peak ( P wave) from contraction (depolarisation of the atria

Then there’s the QRS complex, (trough, peak, trough) formed via contraction of the ventricles

T wave (peak) caused by relaxation of the ventricles

Question 23

What does the height of an electrocardio graph represent?

Answer 23

How much electrical charge is passing though the heart, so a higher peak represents a stronger contraction

Question 24

How do doctors diagnose heart problems with electrocardiograms and what are they looking for?

Answer 24

Compare it with a normal one
Problems:
Heart beat too fast or too slow
Ecoptic heartbeats, caused by early contraction of atria
Fibrillation, a really irregular heartbeat

Question 25

Structure of haemoglobin?

Answer 25

It’s a large protein, with a quaternary structure

Made up of 4 polypeptide chains each containing a haem group, which contains iron

Question 26

Hameoglobin has a high affinity for Oxygen, what does this mean?

Answer 26

It readily bonds to it, (4 oxygen molecules can bind to each haemoglobin molecule)

Question 27

Oxygen joins to the hameoglobin forming?

Answer 27

Oxyhaemoglobin

Question 28

What’s the reversible reaction of haemoglobin?

Answer 28

Hb + 4O2 = reversible reaction HbO4

Question 29

How does partial pressure effect Oxygen binding to haemoglobin?

Answer 29

High partial pressure of Oxygen (in the lungs), oxygen loads onto haemoglobin

Low partial pressure of Oxygen (in respiring tissues), Oxygen in unloaded from haemoglobin

Question 30

Describe a dissociation curve for oxygen affinity?

Answer 30

Partial pressure of Oxygen on x axis
% of saturated haemoglobin with oxygen on the y axis
Graph is S shaped, as after the first oxygen binds the shape alters so that it’s easier for other molecules to bind to
However as Hb starts to get saturated it becomes more difficult for more oxygen to bind ( after 3 oxygens roughly)

Question 31

How is fetal haemoglobin different to adult haemoglobin, and what effects does this have?

Answer 31

Fetal haemoglobin has a higher affinity for Oxygen (steeper S shaped curve)
Effect:
The fetus gets it’s oxygen from it’s mother blood across the placenta
By the time the mother’s blood reaches the placenta, some oxygen as already been taken by the rest of the mother’s body,
So the fetus haemoglobin requires a higher affinity for oxygen that the adults otherwise it wouldn’t get enough oxygen to survive

Question 32

Describe how a high partial pressure of CO2 makes haemoglobin more ready to offload oxygen?

Answer 32

Most of the CO2 from respiring tissues diffuses into red blood cells, here it reacts with water to from carbonic acid, catalysed by the enzyme carbonic anyhydrase ( The rest of the CO2 binds to haemoglobin and is taken to the lungs)

The carbonic acid dissociates to H+ ions and HCO3(-) ions

This increase in H+ ions causes oxyhaemoglobin to unload it’s oxygen, so it can take up H+ ions. This forms a compound called haemoglobinic acid (also stops H+ ions increasing acidity)

The HCO3- ions diffuse out of the red blood cells and are transported in the blood plasma. To compensate for the loss of HCO3- ions from the red blood cells Cl- ions diffuse into the red blood cells

This is the chloride shift and prevent any possible pH change

When the blood reaches the lungs the low concentration of CO2 causes some of the HCO3- and H+ to recombine into CO2 and water

The CO2 then diffuses into the alveoli and is breathed out

Question 33

What’s the tissue called after the bundle of hiss?

Answer 33

PURKYNE TISSUE