transport animals Flashcards
1
Q
What is a transport system?
A
The system that transports required
substances around the body of an
organism
2
Q
Why are specialised transport
systems needed in
multicellular animals?
A
• High metabolic demands (need lots of O2 and food & produce lots of waste products) so diffusion over long distances isn’t enough to supply the quantities needed • SA:V ratio gets smaller as multicellular organisms get bigger, so the amount of surface area available to absorb or remove substances gets relatively smaller • Molecules e.g. hormones or enzymes may be made in one place but needed in another • Food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism • Waste products of metabolism need to be removed from the cells and transported to excretory organs
3
Q
What is a circulatory system?
A
The transport system of an animal • Liquid transport medium that circulates around the system (blood) • Vessels that carry the transport medium • Pumping mechanisms to move the fluid around the system
4
Q
What is a mass transport
system?
A
A transport system where
substances are transported in a
mass of fluid
5
Q
What is an open circulatory
system?
A
A circulatory system with a heart but few vessels to contain the transport medium. • Transport medium is pumped straight from the heart into the body cavity (haemocoel) , then it comes into direct contact with the tissues and the cells • This is where exchange takes place between the transport medium and the cells • Transport medium returns to the heart through an open-ended vessel • Mainly found in invertebrate animals inc. insects and molluscs
6
Q
Describe the circulatory
system in insects
A
• Insect blood = haemolymph; it doesn’t carry O2 or CO2, it transports food and nitrogenous waste products & cells involved in defence against disease • Body cavity is split by membrane and the heart extends along the length of the thorax and abdomen • The haemolymph circulates, but steep diffusion gradient cannot be maintained for efficient diffusion • Amount of haemolymph flowing through a particular tissue can’t be varied to meet changing demands
7
Q
What is a closed circulatory
system?
A
A circulatory system where the blood is enclosed in blood vessels and does not come into direct contact with the cells of the body beyond the blood vessels • Amount of blood flowing to a particular tissue can be adjusted by widening or narrowing of blood vessels • Contain a blood pigment that carries the respiratory gases • Found in many different animal phyla including: echinoderms, cephalopod molluscs, annelid worms and vertebrate groups (including mammals)
8
Q
What is a single closed
circulatory system?
A
A circulatory system where the blood flows through the heart and is pumped out to travel all around the body before returning to the heart • Blood passes through 2 sets of capillaries before it returns to the heart • 1st: Exchanges O2 and CO2 • 2nd: In the different organ systems, substances are exchanged between the blood and the cells • Due to passing though these 2 sets of very narrow vessels, blood pressure in the system drops, and so the blood returns back to the heart slowly • Limits efficiency of the exchange processes, so the activity of animals tends to be relatively low
9
Q
Explain how fish can be so
active with a single closed
circulatory system
A
• Low metabolic demands on their bodies and efficient gaseous exchange • Body weight is supported by water they live in and they don’t maintain their own body temperature • Countercurrent gaseous exchange mechanism in their gills that allows them to take lots of O2 from water
10
Q
What is a double closed
circulatory system?
A
A circulatory system where the blood travels twice through the heart for each circulation of the body. Most efficient system for transporting substances around the body and involves 2 separate circulations • 1st: Blood is pumped from the heart to the lungs to pick up O2 and unload CO2, and then returns to the heart • 2nd: Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again Each circulate only passes through one capillary network, meaning that a high pressure and fast flow of blood can be maintained
11
Q
Describe the following components found in some blood vessels: 1. Elastic fibres 2. Smooth muscle 3. Collagen
A
1. Composed of elastin and can stretch and recoil, providing vessel walls with flexibility 2. Contracts or relaxes, which changes the size of the lumen 3. Provides structural support to maintain the shape and volume of the vessel
12
Q
Describe the roles of arteries
A
Carry blood away from the heart to the tissues of the body • Carry oxygenated blood • EXCEPT in the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the umbilical artery (during pregnancy) which carries deoxygenated blood form the foetus to the placenta • Blood in arteries is under higher pressure than blood in the veins
13
Q
Describe the structure of
arteries
A
Artery walls contain elastic fibres, smooth muscle and collagen. The outer layer of an artery (endothelium) is smooth so the blood flows easily over it Wall consists of 3 layers: • Inner layer (tunica intima) consists of a thin layer of elastic tissue which allows the wall to stretch (within limits maintained by collagen) to take the larger blood volume, and then recoil to help maintain blood pressure • Middle layer (tunica media) consists of a thick layer of smooth muscle • Outer layer (tunica adventitia) is a relatively thick layer of collagen and elastic tissue. This provides strength to withstand the high pressure, and recoil to maintain the pressure
14
Q
What happens to the elastic
fibres in between the
contractions of the heart?
A
The elastic fibres recoil ad return to their original length, helping to even out the surges of blood pumped from the heart to give a continuous flow
15
Q
Describe the structure of
arterioles
A
• Arterioles link the arteries and the capillaries • Have more smooth muscle and less elastin in their walls than arteries, as they have little pulse surge • Can constrict or dilate to control the flow of blood into individual organs • Vasoconstriction: when the smooth muscle in the arteriole contracts, it constricts the vessel and prevent blood flowing into a capillary bed • Vasodilation: when the smooth muscle in the wall of an arteriole relaxes, blood flows into the capillary bed
16
Q
What are capillaries?
A
Microscopic blood vessels that link the arterioles with the venues, forming and extensive network through all the tissues of the body. They have very thin walls and allow the exchange of materials between the bloc and tissue fluid
17
Q
How are capillaries adapted for
their role?
A
• Provide a very large surface area for the dissuasion of substances into and out of the blood • Walls are 1 endothelial cell thick, giving a very thin layer for diffusion • Total cross sectional area of the capillaries is always greater than the arteriole supplying them so the rate of blood flow falls • Slow movement of blood through capillaries gives more time for exchange of materials by diffusion between the blood and the cells • Lumen is very narrow so red blood cells squeeze against the walls as they pass through, helping the transfer of O2 as it reduces diffusion path to the tissues. Also increases resistances and reduces rate fo flow • Walls are leaky allowing blood plasma and dissolved substances to leave the blood
18
Q
Describe the roles of veins
A
• Carry blood away from the cells of the body towards the heart • They carry deoxygenated blood • EXCEPT pulmonary vein (carries oxygenated blood from the Lins to the heart), and umbilical vein (carries oxygenated blood from the placenta to the foetus)
19
Q
Describe the structure of veins
A
• Walls have lots of collagen, relatively little elastic fibre and the vessels have a wide lumen smooth endothelium to ease blood flow • Thinner layers of collagen, smooth muscle and elastic tissue than in artery walls (because they don’t need to stretch and recoil and are not actively constricted in order to reduce blood flow) • Contain valves to help the blood flow back to the heart and prevent it flowing in the opposite directions
20
Q
How is blood kept flowing in
the right direction in veins?
A
• As walls are thin, veins can be flattened by the action of surrounding skeletal muscle • Contraction of the surrounding skeletal muscle applies pressure to the blood, forcing the blood to move along in a direction determined by the valves
21
Q
Do veins have a pulse?
A
No. The surges from the heart
pumping are lost as the blood
passes through the narrow
capillaries.
22
Q
Describe venules
A
• They link the capillaries with the veins • They have very thin layers of muscle and elastic tissue outside the endothelium, and a thin outer layer of collagen • Several venules join to form a vein
23
Q
What are the adaptations of
veins to overcome the problem
of transporting blood under
low pressure?
A
• Most veins have one way valves at intervals (flaps or inholdings of the inner lining of the vein) that only open when blood flows in the direction of the heart • Many of the bigger veins run between the big active muscles in the body; when the muscles contract, they squeeze the veins, forcing blood towards the heart • Breathing movements of the chest act as a pump. The pressure changes and squeezing actions move blood in veins of the chest and abdomen towards the heart
24
Q
What does blood consist of?
A
• Plasma (55%) - main component; yellow fluid containing many dissolved substances and carrying blood cells • Red blood cells (erythrocytes) • White blood cells (leucocytes) • Platelets - fragments of large cells called megakaryocytes, and they are involved in the clotting mechanism of the blood • Dissolved glucose, amino acids, mineral ions, hormones • Large plasma proteins
25
Describe 3 plasma proteins
```
• Albumin - important for maintain
the osmotic potential in the blood
• Fibrinogen - important in blood
clotting
• Globulins - involved in transport
and the immune system
```
26
What are the functions of the
| blood?
```
Maintenance of a steady body
temperature
• Acts as a buffer, minimising pH
changes
Transport of:
• O2 to, and CO2 from, the respiring
cells
• Digested food from the small
intestine
• Nitrogenous waste products from
the cells to the excretory organs
• Hormones
• Food molecules from storage
compounds to the cells that need
them
• Platelets to damaged areas
• Cells and antibodies involved in
the immune response
```
27
What is oncotic pressure?
```
The tendency of water to move into
the blood in the capillaries from the
surrounding fluid by osmosis as a
result of the plasma proteins (which
gibe the blood in the capillaries a
low water potential)
• - 3.3 kPa
```
28
What is hydrostatic pressure?
```
The pressure created by water in an
enclosed system. As blood flows
through the arterioles into the
capillaries, it is still under pressure
every time the heart contacts. This is
hydrostatic pressure
• 4.6 kPa at arterial end
• 2.3 kPa at venous end
```
29
What is tissue fluid?
```
The solution surrounding the cells of
multicellular animals. Similar to
blood plasma, but doesn’t contain
most of the cells found in blood, nor
does it contain plasma proteins
Diffusion takes places between the
blood and the cells through the
tissue fluid
```
30
Describe the formation of
| tissue fluid
```
• At the arterial end, hydrostatic
pressure is higher than oncotic
pressure attracting water in by
osmosis, so fluid is squeezed out
of the capillaries
• This fluid fills the spaces between
the cells and is called tissue fluid
```
31
What happens as blood moves
through the capillaries towards
the venous system?
```
The balance of forces changes
• Hydrostatic pressure falls to
2.3kPa in the vessels, as fluid has
moved out and the pulse is lost
• Oncotic pressure is now stronger
than hydrostatic pressure, so
water moves back into the
capillaries by osmosis
• By the time blood returns to veins,
90% of the tissue fluid is back in
the blood vessels
```
32
What is lymph?
```
Modified tissue fluid that is collected
in the lymph system
• 10% of the liquid that leaves the
blood vessels drains into lymph
capillaries
• Similar in composition to plasma
and tissue fluid, but has less O2
and fewer nutrients
• Contains fatty acids absorbed
from villi in the small intestine
```
33
How is fluid in lymph vessels
| transported?
```
• Through the squeezing of body
muscles
• One-way valves (like in veins)
prevent back flow
• Eventually lymph returns to the
blood, flowing into the right and
left subclavian veins
```
34
Describe the lymph nodes
```
• Found along the lymph vessels
• Lymphocytes build up here when
necessary and produce antibodies
which are then passed into the
blood
• Also intercept bacteria and debris
from the lymph, which are
ingested by phagocytes found in
the nodes
• Major sites: neck, armpits,
stomach, groin
```
35
What are enlarged lymph
| nodes a sign of?
That the body is fighting off an
| invading pathogen
36
```
Describe haemoglobin (in
terms of transporting oxygen)
```
```
Very larger globular conjugated
protein made up of 4 peptide
chain, each with a Fe2+ containing
haem group which is said to have
a high affinity for oxygen
• The Fe2+ ion can attract and hold a
single O2 molecule
• 300 million haemoglobin
molecules in each red blood cell,
and each can bind to 4 O2
molecules
```
37
What is the reaction for oxygen
| binding with haemoglobin?
Hb + 4O2 ⇌ Hb(O2)4
| haemoglobin + oxygen ⇌ oxyhaemoglobin
38
Describe how oxygen is
| carried by erythrocytes
```
1. In the lungs, O2 moves into the
erythrocytes and binds with the
haemoglobin
2. Arrangement of haemoglobin
molecule means that as soon as
one O2 molecule binds to a
haem group, the molecule
changes shape, making it easier
for the next O2 molecules to bind
(known as positive cooperativity)
3. O2 is bound to the haemoglobin
so, free O2 concentration in the
erythrocyte stays low and steep
diffusion gradient is maintained
until all of the haemoglobin is
saturated with O2
4. When blood reaches body
tissues, O2 moves out of the
erythrocytes down a
concentration gradient
5. Once the first O2 molecule is
released by the haemoglobin,
the molecule changes shape,
and it becomes easier to remove
the remaining O2 molecules
```
39
What is an oxygen dissociation
| curve?
```
Graph showing the relationship
between oxygen and haemoglobin
at different partial pressures of
oxygen (pO2)
• They show the affinity of
haemoglobin for oxygen
```
40
Describe the oxygen
| dissociation curve graph
```
• A very small change in the pO2 in
the surrounds makes a significant
difference to the saturation of the
haemoglobin with O2 because
once the first O2 is added, change
in shape of molecule means other
O2 are added rapidly
• Curve levels out at highest pO2s
because all the haem groups are
bound to O2 so the haemoglobin is
saturated
```
41
What is the effect of partial
pressure on the movement of
oxygen in the body?
```
• High pO2 in the lungs means that
the haemoglobin in erythrocytes is
rapidly loaded with O2
• Relatively small drop in respiring
tissues means O2 is released
rapidly from the haemoglobin to
diffuse into the cells
• This effect is enhanced by
relatively low pH in tissues
compared with the lungs
```
42
How much of the O2 carried in
erythrocytes is released into
the body cells when you’re not
very active?
• Only 25%
• The rest acts as a reservoir for
when the demands of the body
increase suddenly
43
What is the effect of carbon
| dioxide?
```
At high partial pressures of CO2,
haemoglobin gives up oxygen more
easily. This is known as the Bohr
effect
• Bohr shift on oxygen dissociation
curve = shift to the right
Important in the body because as a
result:
• In active tissues with high pCO2,
haemoglobin gives up its O2 more
readily
• In the lungs where the proportion
of CO2 in the air is relatively low,
O2 bids to the haemoglobin
molecules easily
```
44
What is the difference between
fetal and adult haemoglobin
and why?
```
Fetal haemoglobin has a higher
affinity for oxygen than adult
haemoglobin at each point along the
dissociation curve
• Foetus completely depends on its
mother to supply it with oxygen
• Mother’s oxygenated blood runs
close to the deoxygenated fetal
blood in the placenta
• If fetal blood had the same affinity
for O2 as the blood of the mother,
the little or no O2 would be
transferred to the blood of the
foetus
• Fetal haemoglobin has a higher
affinity for O2, so it removes O2
from the maternal blood as they
move past each other
• Fetal haemoglobin on oxygen
dislocation curve = shift to the left
```
45
What are the 3 ways in which
| carbon dioxide is transported?
```
• 5% is dissolved in the plasma
• 10-20% is combined with the main
groups in polypeptide chain of
haemoglobin to form a compound
called carbaminohaemoglobin
• 75-85% is converted into
hydrogencarbonate ions (HCO3-) in
the cytoplasm of red blood cells
```
46
What happens when CO2
| diffuses into red blood cells?
```
It combines with water to form a
weak acid called carbonic acid. This
reaction is catalysed the enzyme
carbonic anhydrase
CO2 + H2O ⇌ H2CO3
The carbonic acid then dissociates
to release H+ and HCO3- ions
H2CO3 ⇌ HCO3- + H+
```
47
What happens to the HCO3-
| and H+ ions next?
```
Hydrogencarbonate ions (HCO3-)
• Diffuse out of the red blood cell
into the plasma
• Chloride shift - charge in the red
blood cell is maintained by the
movement of chloride ions (Cl-)
from the plasma into the red blood
cell
Hydrogen ions (H+)
• Build of of these could cause the
contents of the red blood cell to
become very acidic
• Taken out of solution by
associating with haemoglobin to
produce haemoglobinic acid (HHb)
• The haemoglobin is acting as a
buffer (a compound that maintains
a constant pH)
```
48
What is the benefit of
converting the carbon dioxide
into hydrogencarbonate ions?
Carbon dioxide must be removed from the body or it makes the blood dangerously acidic .Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient
49
What happens when the blood
| reaches the lung tissue?
```
• Relatively low concentration of
carbon dioxide
• Carbonic anhydrase catalyses the
reverse reaction, breaking down
carbonic acid into CO2 and water
• HCO3- ions diffuse back into the
erythrocytes and react with H+
ions to form more carbonic acid
• When this is broken down by
carbonic anhydrase it releases free
CO2, which diffuses out of the
blood into the lungs
• Cl- ions diffuse out of the
erythrocytes back into the plasma
down an electrochemical gradient
```
50
Describe the Bohr effect
```
Effect an increasing concentration of
CO2 has on haemoglobin
• CO2 enters erythrocytes forming
carbonic acid, which dissociates
to release H+ ions
• H+ ions make pH of cytoplasm
more acidic
• Acidity alters tertiary structure of
haemoglobin and reduces the
affinity of it for O2
• Haemoglobin is unable to hold as
much O2, and O2 is released from
the oxyhemoglobin to the tissues
• Respiring tissues = more CO2, so
more O2 will be released
```
51
Why is the Bohr effect
| important?
```
It results in more O2 being released
where more CO2 is produced in
respiration, which is what muscle
need for aerobic respiration to
continue
```
52
Describe the flow of blood
| through the right side of the heart
```
Deoxygenated blood
1. Enters the right atrium from the
superior and inferior vena cave
at relatively low pressure
2. As blood flows in, slight pressure
builds up until the AV valve
opens to let blood pass into the
right ventricle
3. When both the atrium and
ventricle are filled with blood, the
atrium contracts, forcing all the
blood into the right ventricle and
stretching the ventricle walls
4. As right ventricle starts to
contract, AV valve closes,
preventing back-flow of blood
5. Tendinous cords make sure that
the valves are not turned inside
out by the pressures exerted
when the ventricle contracts
6. Right ventricle contracts fully
and pumps oxygenated blood
through the semilunar valves into
the pulmonary artery, which
transports it to the capillary beds
of the lungs. Semilunar valves
prevent back-flow of blood into
the heart.
```
53
Describe the flow of blood
| through the left side of the heart
```
Oxygenated blood
1. Enters the left atrium from the
pulmonary vein
2. As pressure in the atrium builds,
the AV valve opens, so the
ventricle also fills with blood
3. When both the atrium and
ventricle are full, the atrium
contracts, forcing all the blood
into the left ventricle
4. The left ventricle then contracts
and pumps oxygenated blood
through semilunar valves into the
aorta and around the body
5. As the ventricle contracts, the AV
valve closes, preventing any
back flow of blood
```
54
```
How are the following
chambers adapted for the
blood pressure they handle?
1. Atria
2. Right ventricle
3. Left ventricle
```
```
Atria
• Muscle of atrial walls is very thin
• These chambers do not need to
create much pressure
• Function is to receive blood from
veins and push it into ventricles
Right Ventricle
• Thicker walls than atria
• Needed to pump blood out heart
• Pumps deoxygenated blood to the
lungs, which are beside the heart,
so blood doesn’t travel very far
• Alveoli in the lungs are very
delicate and could be damaged by
very high blood pressure
Left Ventricle
• Walls 2 or 3 times thicker than RV
• Blood from LV pumped out aorta
so needs enough pressure to
overcome the resistance of
systemic circulation
```
55
What is the cardiac cycle?
The events of a single heartbeat
(which lasts about 0.8 seconds in a
human adult), composed of diastole
and systole
56
What happens in diastole?
```
• The heart relaxes
• The atria and then the ventricles fill
with blood
• Volume and pressure of blood in
the heart builds as the heart fills,
but the pressure in the arteries is
at a minimum
```
57
What happens in systole?
```
• The atria contract (atrial systole)
followed by the ventricles
(ventricular systole)
• Pressure inside 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 main body circulation
• Volume and pressure of the blood
in the heart are low at the end of
systole
• Blood pressure in the arteries is at
a maximum
```
58
Describe pressure changes
| during the cardiac cycle
```
Aortic pressure (brown)
• Rises when ventricles contract as
blood is forced into the aorta
• Then gradually falls but never below
12 kPa, as the elasticity of its wall
creates a recoil action
• Recoil produces a temporary rise in
pressure at the start of the relaxation
phase
Atrial pressure (pink)
• Always relatively low because thin
walls of the atrium can’t create
much force
• Highest when they are contracting,
but drops when the left AV valve
closes and its walls relax
• Atria then fill with blood leading to a
gradual build-up of pressure
• Slight drop when left AV valve closes
and some blood moves into the
ventricle
Ventricular pressure (yellow)
• Low at first, but gradually increases
as the ventricles fill with blood as
the atria contract
• Left AV valves close and pressure
rises dramatically as thick walls of
ventricle contract
• As pressure rises above aortic
pressure, blood is forced into the
aorta past the semilunar valves
• Pressure falls as the ventricles
empty and the walls relax
Ventricular volume (green)
• Rises as atria contract and ventricles
fill with blood, then drops suddenly
as blood is forced out into the aorta
when the semilunar valve opens
• Volume increases again as the
ventricles fill with blood
```
59
Describe the sounds of the
| heartbeat
```
• Made by blood pressure closing
the heart valves
• Two sounds of a heartbeat are
described as “lub-dub”
• 1st sound is when blood is forced
against the AV valves as ventricles
contract
• 2nd sound is when a back flow of
blood closes the semilunar valves
in the aorta and pulmonary artery
as the ventricles relax
```
60
Why is cardiac muscle said to
| be ‘myogenic’?
```
It has its own intrinsic rhythm at
around 60 bpm.
• Prevents the body wasting
resources to maintain basic heart
rate
• Average resting heart rate of an
adult is 70 bpm because other
factors also affect heart rate (e.g.
exercise, excitement and stress)
• Basic rhythm of the heart is
maintained by a wave of electrical
excitation
```
61
How is the basic rhythm of the
| heart maintained?
```
1. A wave of electrical excitation
begins in the pacemaker area
called the SAN, causing atria to
contract and so initiating the
heartbeat. Layer of nonconducting tissue prevents
excitation passing directly to the
ventricles
2. Electrical activity form the SAN
is picked up the the AVN, which
imposes a slight delay before
stimulating the bundle of His ( a
bundle of conducting tissue
made up of Purkyne fibres)
which penetrate through the
septum between the ventricles
3. bundle of His splits into 2
branches and conducts the
wave of exception to the apex of
the heart
4. At the apex, the Purkyne fibres
spread out through the walls of
the ventricles on both sides,
Spread of excitation triggers
contracting of ventricles, starting
at apex. Starting here allows
more efficient emptying of the
ventricles
```
62
What is the importance of the
delay is the spread of the
excitation from the SAN to the
AVN?
Ensures that the atria have stopped
contracting before the ventricles
start
63
What is an electrocardiogram
| (ECG)?
```
A technique for measuring tiny
changes in the electrical
conductivity of the skin that result
from the electrical activity of the
heart. This produces a trace that can
be used to analyse the health of the
heart
```
64
What is tachycardia?
```
• Heartbeat is very rapid; >100 bpm
• Normal during exercise, fever, fear
or anger
• If abnormal, may be caused by
problems in electrical control of
heart
• Treated by medication or surgery
```
65
What is bradycardia?
```
• Heart rate slows down < 60 bpm
• Common in people who are fit -
training makes heart beat more
slowly and efficiently
• Severe bradycardia can be serious
and may need an artificial
pacemaker
```
66
What is ectopic heartbeat?
```
• Extra heartbeats that are out of
normal rhythm
• Most people have at least 1 a day
• Usually normal but can be linked
to serious conditions when they
are frequent
```
67
What is atrial fibrillation (example of
| arrythmia)?
```
• Abnormal rhythm of the heart
• Rapid electrical impulses generated
in atria so they contract very fast
and not properly
• Only some of impulses passed to
ventricles, which therefore contract
less often, so heart doesn’t pump
blood effectively
```
