M3, C8 Transport in Animals Flashcards
What is transport
the movement of oxygen, nutrients, hormones, waste and heat around the body.
Why do animals need a transport system?
High Metabolic demand, ie need lots of oxygen and food, produce lots of waste, diffusion over long distances is not enough
Small SA:V ratio
Long diffusion distances so need to be able to transport hormones/enzymes quickly
Food digested in one organ, needs to be transported to all cells
Waste products of metabolism need to be removed from cells and excreted
what makes a good transport system?
fluid/medium (blood)
a pump
exchange surfaces
tubes/vessels
what is a mass transport system
when substances are transported in a mass of fluid with a mechanism for moving the fluid around
what is a closed circulatory system
In a closed circulatory system, blood is fully enclosed within blood vessels at all times.
From the heart, blood is pumped through a series of progressively smaller vessels.
In the smallest vessels, capillaries, substances diffuse in and out of the blood and into cells.
Blood then returns to the heart via a series of progressively larger vessels.
Use the example of insects to demonstrate how an open circulatory system works
An open circulatory system consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel.
In the haemocoel, the haemolymph directly bathes organs and tissues, enabling the diffusion of substances.
The transport medium is under low pressure.
Haemolymph moves around the haemocoel due to the movement of the organism.
The haemolymph returns to the heart through an open-ended vessel
what are the similarities between the open and closed circularity systems?
Liquid transport medium
Vessels to transport the medium
Pumping mechanism to move the fluid
what are the differences between the open and closed circulatory systems?
Open has few vessels, closed has a transport medium enclosed in vessels
Open transport medium is pumped into body cavity (haemocoel) under low pressure, in closed heart pumps blood around under high pressure
Blood has a higher rate of flow (moves faster) in open circulatory system
In open, transport medium directly contacts the body cells, in closed no direct contact between medium and cells
In open transport medium returns to heart through open ended vessels in closed blood flows relatively fast and returns to heart all within vessels
what are examples of organisms that have an open circulatory system and organisms with a closed circulatory system
Closed:
All vertebrates (fish and mammals)
Open:
Invertebrates (insects)
what is a single circulatory system
Blood goes once through the heart for each complete circuit of the body
For example fish – the heart pumps blood to the gills to pick up oxygen and then on through the body to deliver oxygen.
what is a double circulatory system
The blood travels twice through the heart for each circuit of the body
For example in mammals – the heart is divided down the middle
what is the advantage with a double circulatory system
Blood is pumped at a higher pressure so travels faster
So oxygen is delivered quicker to the cells
what are arteries
transport blood away from the heart
blood is pumped out of the heart at high pressure so arteries are structured to withstand and maintain high pressure
what are the 5 general layers found in blood vessels
Collagen Smooth Muscle Elastic FIbres Endothelium Lumen
what is the function of the collagen layer in blood vessels
Tough collagen fibers are protective and supportive
what is the smooth muscle layer in arteries
Allows arteries to expand and constrict
This is useful as it allows them to control the volume of blood reaching an organ.
Smooth muscle and elastic fibers are the thickest layers in arteries
what is the lumen layer in the artery
narrow to maintain high blood pressure
How does the collagen and smooth muscle layer in veins compare to that in arteries
thinner than arteries because don’t need to withstand high blood pressure
what is the lumen layer in veins
relatively large compared to artery because they don’t need to maintain high blood pressure
why do veins need valves
to prevent the backflow of blood away from the heart
also help prevent blood from pooling in the lower parts of the body due to gravity
what are capillaries and what are their adaptations
branch off from arterioles and are the smallest blood vessels
form capillary beds which function to bring the blood as close to cells as possible to enable the efficient exchange of substances
thin lumen - slows blood flow for diffusion
one cell thick endothelium
basement membrane anchors capillaries in position within tissues
what are arterioles
branch off from arteries
similar in structure to arteries but have less elastic tissue and more smooth muscle. this enables them to constrict and reduce blood flow through capillaries
can also vasoconstrict and vasodilate for thermoregulation
what are venules
They drain blood from capillary beds and feed it back into veins.
Note they also contain valves
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What is in blood?
consists of plasma containing: dissolved glucose amino acids mineral ions hormones proteins (including albumin, globulins and fibrinogen) red blood cells white blood cells platelets
what are platelets and what is their function
Fragments of large cells
They form blood clots, sealing off the site of a wound
what is are the 7 functions of blood?
To transport:
- oxygen to, carbon dioxide from, the respiring cells
- digested food from the small intestine
- nitrogenous waste products from the cells to the excretory organs
- chemical messages (hormones)
- food molecules from storage compounds to the cells that need them
- platelets to damaged areas
- cells and antibodies involved in the immune response
what else does blood contribute to
maintenance of a steady body temperature and acts as a buffer, minimising pH changes
what is osmosis
It is the net movement of water molecules from a region of high water potential to a region of low water potential, through a partially-permeable membrane.
what is tissue fluid
The fluid that surrounds cells in tissues
Made from substances that leave the blood plasma (oxygen, glucose, nutrients)
But NO red blood cells or big proteins, they are too big to get through the small holes (fenestrations) in the capillary wall
what is lymph
Excess tissue fluid gets returned to the blood through the lymphatic system (10%)
Similar composition to plasma and tissue fluid, but less oxygen and fewer nutrients.
what are the three components of the lymphatic system
lymph vessels
lymph capillaries
lymph nodes
what are lymph nodes
Found along the lymph vessels, sac-like organs, contain lymphocytes, which produce antibodies to intercept pathogens
compare blood, tissue fluid and lymph
only blood has red blood cells
all have white blood cells but tissue fluid has very few
only blood has platelets
Only blood has large plasma proteins
Lymph contains antibodies
all have water and all have dissolved solutes
Explain tissue fluid formation in capillaries
At the arterial end, hydrostatic pressure is higher than osmotic pressure, so components of blood plasma e.g. oxygen and glucose leave through fenestrations in the capillary endothelium.
Osmotic pressure remains constant throughout the capillary
At the venule end the hydrostatic pressure is now lower than the osmotic pressure so tissue fluid returns down the pressure gradients
overall how does blood plasma go to tissue fluid then to lymph and back to the blood plasma?
blood plasma to tissue fluid by ultrafiltration
tissue fluid to blood plasma by reabsorption
tissue fluid to lymph by drainage
lymph to blood plasma by lymph vessels
how are erythrocytes adapted for carrying lots of oxygen
no nucleus or other organelles to carry as much hemoglobin as possible
biconcave to increase surface area
almost same width as capillary - can fit through narrow capillaries
contains haemoglobin to react with 4 oxygen molecules making oxyhaemoglobin
what’s the structure of haemoglobin
It is a globular protein- hydrophilic interactions on outside, hydrophobic interactions on the inside
Quaternary structure- 4 polypeptide chains, 2 Alpha and 2 Beta Subunits
It contains 4 iron heam groups
Each heam group joins to one oxygen molecule
So in total, 4 oxygen molecules can join to a haemoglobin molecule to form: oxyhaemoglobin
Explain why the oxygen dissociation curve takes an S shape
shows how much oxygen the haemoglobin has compared to the oxygen available
0% saturation means none of the Hb molecules are carrying any oxygen
when the percentage of oxygen is low Hb has low affinity (hard to get) oxygen. It will release oxygen to the tissues
However there is steep increase in %saturation of O2 with haemoglobin with small increases in pO2 (middle section of graph) as after the first O2 molecule has bound to haemoglobin there is a change in its tertiary structure making it easier for subsequent O2 molecules to bing
when the percentage of oxygen is high Hb has a high affinity for the oxygen
It will join to oxygen and become more saturated
100% saturation means all Hb molecules are carrying the max of 4 oxygen molecules
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how is oxygen concentration measured?
As partial pressure (pO2)
what is fetal haemoglobin? how is it different to normal haemoglobin?
Fetus gets O2 from its mother’s blood across the placenta
Mothers placenta has a low partial pressure of O2
Fetal haemoglobin has a higher affinity for oxygen at all partial pressures of O2
This means its oxygen dissociation curve is positioned to the left of adult hemoglobins one (same shape)
The difference in affinites is essential to the survival of the fetus as it means that oxygen will unload from oxyhaemoglobin at the placenta and bind to fetal haemoglobin; supplying the fetus with oxygen.
what is the Bohr effect?
In areas where theres is a high pCO2 the oxygen dissociation curve moves to the right signifying that there is a lower affinity of haemoglobin for oxygen in these conditions. This is known as the BOHR shift
At high pCO2 (e.g respiring tissues) haemoglobin has a low affinity for oxygen and a high affinity for CO2.
This is useful as it means that oxygen will unload from haemoglobin and CO2 will bind to haemoglobin/ diffuse into RBC instead.
This allows respring tissues to be supplied with O2 and CO2 to be taken away from them rapidly
what are the three ways carbon dioxide is transported around the body?
5% Dissolved in blood plasma
10-20% Carbaminohaemoglobin
75-85% Transported in the form of hydrogencarbonate ions
how do hydrogen carbonate ions form
As CO2 diffuses into the blood, some of it enters the RBC’s.
It combines with water to form a weak acid = carbonic acid
This is catalysed by carbonic anhydrase (an enzyme)
CO2 + H2O → H2CO3
This carbonic acid dissociates to release hydrogen ions (H+) and hydrogen carbonate ions (HCO3-)
The hydrogencarbonate ions diffuse out of the RBC’s into the plasma.
what is chloride shift
The negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion down a concentration gradient.
Negatively charged chloride ions move into the erythrocytes which maintains an electrolyte balance of the cell
how does haemoglobin act as a buffer
it acts as a buffer and prevents changes in the pH by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid
what happens when blood reaches the lung tissue
there is a relatively low co2 concentration
carbonic anhydrase catalyses the reverse reaction - breaking down carbonic acid into co2 and water
hydrogen carbonate ions diffuse back into the red blood cells and react with hydrogen ions to form more carbonic acid. this releases free carbon dioxide which diffuses from the blood to the lungs.
chloride ions diffuse out of the red blood cells back into the plasma down an electrochemical gradient.
what is the mammalian heart made of and how does it move
cardiac muscle
contracts and relaxes in a regular rhythm
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what are all the features in the heart
aorta pulmonary vein left atrium heart valve left ventricle septum right ventricle right atrium vena cava pulmonary artery
what is the order of blood flow in the body
left ventricle aorta body vena cava right atrium right ventricle pulmonary artery lungs pulmonary vein left atrium left ventricle
what is the septum
where the two sides of the heart are divided by a layer of muscle
what is the right atrium and the left atrium
the two small chambers at the top of the heart
what is the right ventricle and the left ventricle
two larger chambers at the bottom of the heart
what are the pulmonary veins
blood vessels that bring oxygenated blood from the lungs into the left atrium
what is the aorta
very large blood vessel that carries oxygenated blood from the left ventricle to the rest of the body
what is the pulmonary artery
blood vessel that takes deoxygenated blood from the right ventricle and delivers it to the lungs
what is the vena cava
blood vessel that brings deoxygenated blood from the body and empties it into the right atrium
what is diastole
the whole heart is relaxed and the atria fill with blood
what is atrial systole
the atria contract squeezing blood into the ventricles
what is the ventricular systole
the ventricles contract squeezing blood out of the heart
what is the first main stage of a heartbeat
Ventricles relaxed
The atria contract, which decreases their volume and increases their pressure
This pushes blood into ventricles through AV valves
There’s a slight increase in ventricular pressure and volume as the ventricles receive blood from atria
what is the second main stage of a heartbeat
Atria relax
Ventricles contract (decreasing their volume), increasing pressure
Pressure becomes higher in ventricles than atria, causes AV valves to shut preventing backflow
High pressure in ventricles opens semi-lunar valves
Blood is forces into the pulmonary artery and aorta
what is the third main stage of a heartbeat
Ventricles and atria both relaxed
Higher pressure in pulmonary artery and aorta causes semi-lunar valves to close, preventing backflow
Atria fill with blood (increasing their pressure), due to higher pressure in vena cava and pulmonary vein
Ventricles continue to relax, pressure falls below the pressure in the atria, causing AV valves to open and blood flows passively (70%) into ventricles from atria
The atria contracts, cycle starts again
when will the tricuspid and bicuspid valves open and why
During atrial systole. The atrial contraction causes the blood pressure to be higher in the atria than the ventricles forcing them open
when will the semilunar valves open and why
When the pressure in the ventricles is higher than the aorta/pulmonary artery, so that the blood is forced out into the arteries
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what causes the sounds in the heart
the sounds are from the blood pressure closing the heart valves.
They are described as lub-dub.
The 1st sound comes from the blood forced against the AV valves as the ventricles contract.
The 2nd sound comes as a backflow of blood closes the semi lunar valves in the aorta and pulmonary artery as the ventricles relax.
What does it mean when you say the cardiac muscles is myogenic?
it doesn’t need to be told to beat
sets its own rhythm
what is the order of the wave of excitation?
- SAN (sinoatrial node) is located in the right atrium - it starts the wave of excitation
- The wave passes over the walls of the atria causing it to contract
- Non-conductive tissue prevents the wave from passing straight down to the ventricles.
- The wave is picked up by the AVN (atrioventricular node)
- This delays the wave slightly before passing it down the bundle of His in the septum.
- Bundle of His splits up both sides of the ventricles and passes the wave from the apex up the sides of the ventricles.
- This causes the ventricles to contract from apex to top.
why is the bundle of His important in a heartbeat
It splits into 2 branches and conducts the wave of excitation to the apex.
The purkyne fibres spread out through the wall of the ventricles.
This triggers contraction of ventricles starting at the apex.
Contraction starting at the apex allows more efficient emptying of the ventricles.
what is an ECG?
What are the stages?
Electrocardiograms measures electrical activity of the heart 1) contraction of atria 2) (the point) contraction of ventricles 3) relaxation of ventricles
what is tachycardia?
a fast resting (above 100bpm) heartbeat caused for no reason
the heart produces rapid electrical signals
pumps less efficiently so blood flow is reduced
the muscles are using more oxygen because they are pumping quicker so if it carries on then you could have a cardiac arrest because the muscles aren’t receiving enough oxygen
treatment includes relaxation therapy or beta blocker
what is an increased heartbeat due to?
excitement
stress
exercise
drugs
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what is bradycardia
when the heart rate slows down below 60bpm
what is an ectopic heartbeat
extra heartbeats that are out of normal rhythm
happens to everyone once a day but if it regular then it can be dangerous
What happens to the pressure of the left atria in a heartbeat
- The pressure is lower than ventricles and aorta as thin walls so doesn’t give much force
- when contracting the atria is at its highest pressure as there’s a lot of blood
- pressure then drops as no blood in atria and AV valve is closed so now in relax phase
- pressure increases again as atria fills with blood
What happens to the pressure of the left ventricle through a heartbeat
- When ventricles are relaxing, pressure is low
- when AV valves close, all blood in ventricles so pressure goes up as ventricles contract
- when pressure of ventricles goes above the aortic pressure, that’s when the SL valves open and blood goes into the aorta
- then pressure goes down as the blood leaving the ventricles and relaxing again
What happens to the aortic pressure in a heartbeat
Pressure rises when ventricles contract as blood is going into the aorta
Pressure falls once all the blood has gone through
Semilunar valve closing and recoiling phase produces a temporary pressure rise
Describe and explain how the structure of the artery is adapted to allow it withstand and maintain a high blood pressure [4]
Withstand:
Thick outer layer of collagen provide strength
Folded endothelium prevents damage to the artery walls e.g. tears as it will stretch
Maintain:
Elastic fibers allow the artery to stretch and recoil
Thick layer of smooth muscle constricts which narrows the lumen of the artery.
