C8- Transport in Animals Flashcards
Why do animals need specialised transport systems
high metabolic demands
small sa:v
molecules such as hormones made in one place but needed in the other
waste products from respiration need to be transported to excretory organs
Common features of circulatory systems
Liquid medium to transport substances
Vessels to carry the transport medium
A pumping mechanism to move fluid around the body
Disadvantages of open circulatory systems
Steep concentration gradients cannot be maintained by slow moving haemolymph
Diffusion is not efficient
The system is fixed
–> Doesn’t change if the metabolic demands of the insect changes
Open circulatory system
one in which there is a mixing of the blood and interstitial fluid (fluid that fills the space surrounding cells) to make up the haemolymph
Low pressure system
no blood vessels
Insects Circulatory system
Open circulatory system
cells obtain nutrients directly from the haemolymph
Explain why circulatory systems are found in multicellular organisms but not in unicellular organisms
Unicellular organisms have large SA : V ratio so diffusion distances small and metabolic demands low so diffusion can supply and remove substances quickly and efficiently enough
Multicellular organisms have small SA : V ratio, so long diffusion distances. Metabolic demands are high – diffusion alone can no longer supply all needs quickly and efficiently enough
Describe the function of a circulatory system
Transports requirements for metabolism, e.g., oxygen, food molecules, to cells
removes waste products of metabolism from cells and carries them to excretory organs
transports materials made in one place to another place where they are needed
Why do multicellular organisms have specialised transport systems
Small SA:V
Generally active
–> High metabolic demand and large amounts of waste products produced
Closed circulatory system
features 4
A liquid medium to transport substances (blood)
Blood vessels to carry the blood.
A pump to move the blood around the body.
A respiratory pigment that binds and transports oxygen e.g. haemoglobin
single closed circulatory system
Blood travels once through the heart for each for each complete circulation of the body
less efficient
Only deoxygenated blood passes through the heart
Heart has only 2 chambers
Advantages of a closed circulatory system
The blood is contained within vessels so pressure is high
Increases rate of blood flow to tissues so the system is more efficient
This meets high metabolic demands of many animals (many are ‘warm blooded’).
Amount of blood flowing to different tissues can be changed to meet current needs e.g. vasoconstriction, vasodilation
Double closed circulatory system
Blood passes through the heart twice for each circuit of the body.
More efficient
Oxygenated and deoxygenated blood never mix
Heart has 4 chambers
Arteries
direction of blood transport
carry blood away from the heart at high pressure.
arterioles
smaller arteries that carry blood from arteries to capillaries.
Cappilaries
tiny blood vessels that link arterioles to venules.
Veins
carry blood at low pressure from the capillaries back in to the heart.
venule
A small vein which links the capillaries to a vein
Lumen
the central cavity of a blood vessel (the hole!) through which the blood flows.
Vasoconstriction
the ability of blood vessels to make the lumen narrower due to contraction of smooth muscle in the vessel wall.
vasodilation
the ability of blood vessels to increase the size of the lumen due to relaxation of smooth muscle in the vessel wall.
4 components of blood vessel walls
veins and arteries
Endothelium
Elastic tissue
Muscle tissue
Tough collagen outer layer
Role of tough collagen outer layer in blood vessels
Strong, structural support of vessel, helps to maintain the shape of the vessel, limits stretch and resist pressure changes
Blood vessels
endothelium
a single layer of cells that is smooth to reduce friction
Blood vessels
Smooth muscles
A thick layer of smooth muscle tissue is able to contract or relax to change the diameter of the lumen and alter blood flow.
Muscle contracts: vasoconstriction: narrows the lumen
Muscle relaxes: vasodilation: widens the lumen
Blood vessels
Elastic fibres
made of elastin which allows the vessel to stretch and recoil.
Helps to even out the blood flow and keep blood pressure constant.
Difference between the function of elastic and muscle tissue in blood vessels
Muscle tissue changes the diameter of the lumen allows blood flow to be controlled
e.g. vasodilation increases blood flow during exercise
Elastic tissue allows the artery to stretch and recoil to maintain even blood pressure
Blood vessels
Valves
in which, and not and why
Found in all veins
Valves prevent backflow of blood
Not found in arteries as the blood is under high pressure so does not tend to flow backwards.
NB the pulmonary artery and the aorta where valves are present and prevent backflow of blood into the heart.
Pocket valves inside veins
Prevent backflow of blood.
Muscles around veins contract and squeeze veins aiding flow of blood back towards the heart (muscle pumps).
Structure and functions of veins
3
Veins carry blood from the cells and tissues back to heart.
They carry deoxygenated blood (except the pulmonary vein).
Blood pressure in the veins is very low (compared to arteries).
Structure and function of capillaries
4
Substances are exchanged between the blood and tissues here.
Walls made of a single layer of cells called endothelial cells (called a capillary endothelium).
Gaps (pores) exist between the cells – white blood cells can pass out of capillaries into tissues to fight infection.
Extensive network of capillaries – all cells lie close to a capillary.
Oncotic pressure
The blood contains a number of different proteins which also lower the water potential of the blood.
Oncotic pressure: the tendency of water to move by osmosis as a result of proteins in the blood plasma.
pulling water
Hydrostatic pressure
The pressure of a fluid in a closed space
Specific examples of proteins in plasma
albumin- maintains water potential of the blood
fibrinogen- blood clotting
immunoglobins- WBC
Osmosis
The movement of water from a high water potential to a lower water potential down a water potential gradient, through a partially permeable membrane
What properties of blood make it a good transport medium
95% water
Polar- can disolve many substances
Plasma
contents
Water
Glucose
Amino acids
Fatty acids
Vitamins
Minerals
White blood cells
Red blood cells carrying oxygen
Platelets
Ions
large proteins e.g. antibodies, blood clotting proteins
Tissue fluid
contents
Tissue fluid contains
Water
Glucose
Amino acids
Fatty acids
Vitamins
Minerals
Ions
Oxygen
Small proteins
What does plasma contain that tissue fluid does not
White blood cells
Red blood cells carrying oxygen
Platelets
large proteins
Tissue fluid doesn’t have any cellular components- too large to diffuse through capillary walls
How is water forced out through holes in the walls of capillaries
The hydrostatic pressure at the arterial end of the capillary is high.
It is generated by the pumping force of the heart (contraction of the left ventricle).
How is tissue fluid formed
two forces that drive the movement of water between the blood (inside capillaries) and the interstitial space (space between cells)
The difference in hydrostatic pressure between these two areas
(the pressure exerted by a liquid)
The difference in the water potential that exists between these two areas
(the tendency to draw water in or out as a result of the concentration of solute)
two forces that drive the movement of water between the blood (inside capillaries) and the interstitial space (space between cells)
Hydrostatic pressure
water potential
net filtration pressure
The net filtration pressure is the difference between the hydrostatic pressure (usually +) and the oncotic pressure (usually -)
net movement of fluid in capillaries
arterial vs venous end
arterial- into tissues
venous- into capillaries
oncotic pressure as you move from the arterial end to the venous end
remains constant
lymph nodes
Lymph nodes are swellings that contain white blood cells called lymphocytes
During infection lymph nodes can become swollen and sore due to the proliferation of lymphocytes.
lymphatic system
role
4
drains excess fluid
low pressure
The flow of fluid inside the lymphatic vessels is aided by body muscles that contract to move the fluid towards the heart.
Valves in the vessels prevent the backflow of lymph
composition of lymph
compared to tissue fluid
5
Less oxygen (O2 has been used up by cells for respiration)
More CO2
Fewer nutrients e.g. glucose
More fatty acids (absorbed from the small intestine)
Some antibodies (proteins) - made by plasma cells
arterial and venous ends of capillaries
forces and effect in net movement of fluid
arterial
hydrostatic>oncotic
fluid moves out of capillaries
venous
hydrostatic < oncotic
fluid moves into capillaries
Buffer
role
Maintain pH
Enzyme that catalyses reaction between water and carbon dioxide to carbonic acid
carbonic anhydrase
reaction between carbon dioxide and water
CO2 +H2O <=> H2CO3 <=> HCO3- + H+
3 ways carbon dioxide is transported in the body
hydrogen carbonate ions, HCO3- in blood plasma (75 - 85%)
carbamino compounds e.g. combined with the amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin (about 10 - 20%)
dissolved in solution (in blood plasma) (5 -10 %)
CO2 to H+ and HCO3- in rbcs process
Carbon dioxide diffuses into the cytoplasm of red blood cells.
Here the carbon dioxide reacts with water to form carbonic acid.
This reaction is catalysed by the enzyme carbonic anhydrase.
The carbonic acid dissociates almost immediately to form hydrogen ions and hydrogen carbonate ions.
How many binding sites for O2 on haemoglobin
How many O2 molecules needed for Hb to be fully saturated
There are 4 haem groups so 4 binding sites - places on the Hb molecule that O2 can bind to.
Fully saturated at 4
Reaction between oxygen and haemoglobin
haemoglobin + oxygen <======> oxyhaemoglobin
Function of haemoglobin
Bind to oxygen at a gas exchange surface to transport oxygen to the tissues where oxygen is released
Loading vs unloading of O2 haemoglobin
(association vs dissociation)
Loading- Hb binds to O2 at gas exchange surfaces
unloading- Hb releases its O2 in respiring tissues
Affinity of Hb
define- general then high/low
How readily Hb binds or releases O2
High-> loads easily, unloads less easily
Low-> unloads easily, loads less easily
Partial pressure
definition
Individual pressure of a gas in water
basically concentration
Why will blood never be 100% saturated with O2
some Hb will always be loading or unloading O2 for respiration
Effect of partial pressure of oxygen on saturation of hb
Small increase of PO2 results in a large increase of % saturation of Hb with O2- inc in loading of O2
Conversely a small decrease in the PO2 results in a large decrease in the % saturation - i.e. Hb unloads its O2
Shape of oxygen dissociation curve
Sigmoidal
Explain cooperative nature of Hb binding to O2
longer
When the first molecule of oxygen binds to Hb, the Hb molecule changes shape (this is called a conformational change).
This conformational change increases the affinity of the Hb for oxygen.
The change in shape of Hb exposes the next haem group and the next oxygen binds more readily.
Cooperative binding Hb
Binding the first molecule of oxygen to the Hb makes the second molecule of oxygen bind more easily. This is called COOPERATIVE binding. Hb shows positive cooperativity.
2 ways to read oxygen dissociation curve
Left to right = association (loading)
Right to left = dissociation (unloading)
Bohr effect
define
Effect of CO2 on O2 dissociation
CO2 reacts with water to form carbonic acid, releases H+ ions, lowers Ph, reduces affinity for O2
Bohr effect
Explain
high PCO2 in the tissues
Lowers the affinity of Hb for oxygen
Hb unloads oxygen more easily
The curve is shifted to the RIGHT
Shift in oxygen dissociation curve
Left
Curve shifted to the left:
Affinity of Hb for oxygen is HIGHER
Hb LOADS oxygen more easily
Left- LLLoad
Function of blood
5
oxygen to and carbon dioxide from respiring cells
transport chemical messengers- hormones
transport digested food from the small intestine
transport platelets to damaged areas
Transport of antibodies as a part of the immune system
Fetal hb vs adult hb
Fetal hb has greater affinity for oxygen as oxygen must be transferred form adult to fetal hb
what do the coronary arteries do
supply the cardiac muscle (heart muscle) with blood
Atria characteristics
Atria have thin, elastic walls which stretch as blood flows into the them
Ventricles
characteristics
Ventricles have thicker muscular wall.
This is able to contract strongly and generate a large force to pump the blood at high pressure over larger distances
atrioventricular valves
which are bicuspid and tricuspid
Between the atria and ventricles
Left atrioventricular valve (bicuspid valve)
Right atrioventricular valve (tricuspid)
Right tRi
These valves prevent backflow of blood.
What is a bicuspid and tricuspid valve
Bi- 2 flaps/ sections of valve
Tri- three flaps/ sections of the valve
Type of valves at bottom of aorta and pulmonary artery
semilunar valve
There is a valve at the point where blood leaves the heart in the aorta and the pulmonary artery - these are the
Role of tendons in heart
attach to valves
Tendons are strong and inelastic.
Tendinous cords (chordae tendinae) prevent the valves from turning inside out.
Heart muscle
Cardiac muscle
contracts and relaxes in a regular rhythm
Sequence of filling and emptying of heart
Left and right side of the heart both fill and empty together
Mass flow
heart
the bulk movement of blood from one part of the body to another as a result of a pressure difference between the two points.
The contraction of a heart generates a force which creates the high pressure needed to move blood over large distances.
Two parts of a heartbeat
contraction (also called systole): when the heart muscle contracts
relaxation (also called diastole): when the heart muscle relaxes
One complete heartbeat = 1 systole + 1 diastole
two types of systole
Atrial systole: contraction of the (muscle of the) atria
Ventricular systole: contraction of the muscle of the ventricles
Diastole
relaxation of the muscle in both atria and ventricles
Stroke Volume
The volume of blood pumped out of the left ventricle during each contraction.
Measured in cm3 or dm3.
What is cardiac output
the volume of blood pumped out of the heart during one minute
Cardiac output formula and units
cardiac output = stroke volume x heart rate
dm3 min-1 dm3 bpm
effect of regular exercise on cardiac output
Regular exercise increases the amount of muscle in the heart.
The muscle is able to contract more forcefully with each beat.
A larger volume of blood is expelled from the heart during each beat.
The stroke volume increases.
The heart rate will therefore decrease to maintain the same cardiac output.
What causes a valve to open or close
High pressure of blood behind a valve forces it to open.
High pressure in front of a valve closes it.
Exam technique to describe stages of the cardiac cycle
4 parts
Which way is the blood moving? “From …… to …..”
Which valves are open / closed?
How does the volume and therefore pressure change?
Is the cardiac muscle contracting or relaxed?
Two heart sounds and what makes the sound
The two heart sounds are described as ‘lub - dub’.
The first sound (lub) is made as the pressure of the blood closes the atrioventricular valves as the ventricles contract.
The second sound (dub) is made as the backflow of blood in the aorta and pulmonary arteries closes the semilunar valves as the ventricles relax.
Why can the cardiac muscle tissue in the heart be described as myogenic
The heart can contract and relax at a steady rhythm without any external nerve input.
This means that the body does not waste energy maintaining a basic heart rate.
The sino-atrial node
(SAN)
specialised group of muscle cells found in the upper back wall of the right atrium.
It produces regular waves of electrical excitation similar to nerve impulses which set the rhythm for the rest of the cardiac cycle.
The rate at which the SAN produces these waves determines the rate of the heartbeat - for this reason it is often called the natural pacemaker.
The initiation and coordination of the heartbeat
process
6 step
The sino-atrial node (SAN) produces a wave of electrical excitation (rather like a nerve impulse).
The electrical impulse spreads across both atria causing them to contract.
The wave of excitation is transmitted to the atrioventricular node (the AVN) where the impulse is delayed slightly.
The electrical impulse passes from the AVN to the bundle of His which is made of conducting fibres called Purkyne fibres. These fibres pass through the septum.
The bundle of His splits into two branches and conducts the wave to the apex (bottom) of the heart.
The wave of excitation spreads across both ventricles from the apex (bottom) up to the top of the ventricle. The ventricles contract from the bottom upwards to ensure all the blood is forced out.
Electrical activity key point within the cardiac cycle
SA node
AV node
Bundle of His (Purkinje fibres)
What is the purpose of the non conducting layer of tissue that lies between the atrium and the ventricle of the heart
To ensure that the excitation is not passed on to the ventricles before the atria have fully contracted and emptied.
The AVN imposes a slight delay before passing the wave of excitation on to the bundle of His. Suggest a reason for this.
To ensure that the excitation is not passed on to the ventricles before the atria have fully contracted and emptied.
What is an ECG
An electrocardiogram (ECG) is a simple test that can be used to check your heart’s rhythm and electrical activity.
Electrodes are attached to the skin of the chest - these detect the electrical impulses produced by different parts of the heart each time it beats.
These impulses are recorded and shown on an ECG trace.
ECG analysis
explanation of sections on graph
P wave = depolarisation of the atria (which causes the atria to contract)
QRS complex - depolarisation of the ventricles (which leads to contraction of the ventricles)
T wave - repolarisation of the ventricles (heart relaxes before the next beat)
Gaps between key points on ECG what is contracting
P, QRS, T
P wave= Muscle of the atria contracts
QRS complex= Muscle of the ventricles contracts
T wave= Both atria and ventricles are relaxed
Bradycardia
slow heart rate (less than 60 bpm)
Beats evenly spaced
Severe bradycardia can be serious and needs an artificial pacemaker.
Tachycardia
Fast heart rate
More than 100bpm
Beats evenly spaced
May need medication to slow the heart down
Ectopic heart beat / arrhythmia
Altered rhythm
Seen here an extra beat followed by a longer than normal gap before the next beat
Atrial fibrillation
seen on ECG
An arrhythmia
Abnormal rhythm of the heart
Many small P waves (rapid electrical impulses in the atria) so atria contract very fast.
Time between successive QRS complexes is not regular.
No clearly defined P wave or T wave in this trace
Effect of atrial fibrillation
Impulses are not passed on to the ventricles
Ventricles contract less often
Heart is not efficient
Which valve is pushed open by oxygenated blood entering a ventricle
bicuspid
relative proportions of components of the aorta
low smooth muscle, high elastin and fairly high collagen
What type of pressure causes tissue fluid formation from plasma
Hydrostatic pressure
how is each type of blood vessel adapted to its function
Collagen provides, structure / support.
Collagen maintains shape and volume
artery- elastic layer evens out surges from the pumping of the heart and allows a continuous flow of blood
Only large enough to allow red blood cells totravel through in single file (to increase contactof RBCs with capillary wall).
veins have more collagen than arteries to give structural support as they carry large volumes of blood.
function of collagen in a blood vessel
Collagen provides, structure / support.
Collagen maintains shape and volume
Why does oncotic pressure in the blood only depend on the concentration of plasma proteins
too large to leave vessel
remains constant
