Module 3 Flashcards
why are specialised exchange surfaces needed/not needed?
- Single celled organisms don’t need them as they have low metabolic activity so low demands for oxygen and CO2 exchange. Mammals use lots of energy on temperature regulation which they maintain independent of the environment.
- Also have high SA:Vol ratio
- Land mammals need water and gas exchange, but the conditions needed for gas exchange like moist lining are ideal for evaporation of water. Systems help minimise water loss.
- They have also developed a waterproof surface to minimis water loss stopping gases diffusing through
features of a good exchange surface:
- Large SA (folding walls and membranes)
- Thin barrier reducing diffusion distance
- Maintenance of diffusion gradient by good supply and removal (blood) so occurs faster
- Ventilation helps maintain gradient in gases eg. Flow of water in fish
- Active transport also used to increase rate
difference between respiration and breathing?
Respiration: a chemical reaction at cellular level
Breathing: exchange of gases in blood. CO2 is very important to remove as a build-up can dissolve in blood and is acidic, affecting pH and enzymes. Intercostal muscles move rib cage in and out during deeper breathing
We breathe so we can respire
Ficks law
rate of diffusion is directly proportional to SA x conc. gradient
/ diffusion distance
what surrounds the lungs and what does this do?
Lungs are surrounded by double membranes called pleural membranes which have fluid in the pleural cavity. This provides lubrication between lungs and rib cage
Nasal cavity features
- Has a large SA with good blood supply warming air to body temp
- Hair lining which secretes mucus to trap dust and bacteria protecting lung tissue from irritation and infection
- moist surfaces which increase humidity of incoming air reducing evaporation from exchange surfaces
trachea features
- tube is supported by incomplete rings of strong, flexible cartilage which prevent it collapsing. They are incomplete so food can move easily down oesophagus behind trachea, and in-between rings flexibility Is retained. Ends of cartilage rings are joined by smooth muscle and elastic fibres
- is lined with ciliated epithelium and goblet cells that trap dust and microorganisms that escaped the nose lining and are wafted back up to the throat to be swallowed and digested.
bronchus features
- in chest cavity trachea splits into left and right bronchus leading to each lung
- when in the lungs the bronchi divide to form many small bronchioles with smooth muscle and elastic fibres on walls. This muscle can contract and relax changing the amount of air entering the lungs, but the smallest bronchioles only have elastic fibres not muscle.
- They are lined with a thin layer of flattened epithelium making gas exchange possible
- Bronchi have full rings of cartilage as wont rub against oesophagus, but bronchioles have none. Smallest bronchioles have no goblet cells or cilia.
alveoli features
• Tiny air sacs which are main gas exchange surface. Walls have flattened epithelium cells, collagen and elastic fibres, helping it stretch as air is drawn in and squeeze air out- elastic recoil makes expiration a passive process.
what cells make the wall of the alveoli and capillary?
- Squamous epithelium cells make the wall of the alveoli
- Endothelial cells make the wall of the capillary
what is the function of the capillary network in lungs?
• is mostly pulmonary capillaries
• Forms a dense network around each alveolus
• Alveolar macrophages (type of phagocytic white blood cell)
digest any foreign particles (dust and pathogen) that have reached
the alveoli
what is the function of the epithelial cells in lungs?
- Squamous epithelial cells
- Type 1 and type 2 pneumocytes
- Type 1 are large and flat that make up most of cell wall
- Type 2 secrete surfactant which has antibacterial properties
connective tissue structure and function:
- Forms a supporting layer beneath the epithelium
- Consists of fine collagen and elastin fibres and fibroblast cells
- Allows stretch and recoil of lung tissue with breathing, preventing alveoli bursting. The recoil also helps expel air.
cartilage structure and function:
• Form a connective tissue composed of cells surrounded by a material consisting of mucopolysaccharides, which are complex polysaccharides containing amino groups.
support preventing collapse
What is surfactant and what does it do?
- A mixture of lipids and proteins which helps reduce surface tension of liquid lining the inner surface of alveoli
- Speeds up transport of gases between the air and liquid lining alveolus
- Kills bacteria
- Helps alveoli remain inflated and they stick together as you exhale
Location and function of structures in respiratory system: Cartilage smooth muscle elastic fibres goblet cells ciliated epithelium
trachea and bronchi
support preventing collapse
bronchioles
contracts to constrict airways to control airflow
bronchioles
as smooth muscle relaxes fibres recoil so airways dilate
trachea and bronchi
secrete mucus to trap particles in air
trachea and bronchi
waft mucus up the throat by synchronised beating
why do insects a need gas exchange system?
• They have a tough exoskeleton which doesn’t allow gas exchange and have no blood pigment to carry oxygen
How is the amount of air entering insects gas exchange system managed?
- Has small openings called spiracles along the thorax and abdomen which allow water and air to leave and also for water to escape. There are a pair of spiracles pre abdomen segment.
- Sphincters can open and close the spiracles, and they are kept closed as much as possible to reduce water loss, especially when inactive so oxygen demand is low and there is little CO2 (this is minimised by fluttering when they open and close v quick)
- In discontinuous gas exchange there are 3 stages: open, closed and fluttering . When the spiracles are closed CO2 diffuses into the bodily fluids and is held in the process buffering.
What happens to air after it enters through the spiracles?
- Tracheae lead away from the spiracles, running into and along the body and are the largest respiratory tubes at 1mm diameter.
- Tracheae are lined with chitin which keeps them open if they get bent or pressed. As its relatively impermeable to gases little gas exchange occurs in the trachea
- Tracheae branch into narrower tracheoles diameter 0.6-0.8 um, which are single elongated cells with no chitin lining, therefore are permeable to gases. As they are very small, they run through tissues and through individual respiring cells allowing gas exchange and provide a large SA.
- The movement of air occurs by diffusion usually, and oxygen dissolves in the moisture of the tracheole walls.
How is the supply of oxygen increased in insects?
What can happen if oxygen demand is too high?
• When there is a high oxygen demand (flying) then lactic acid builds up in the tissues causing water to osmose out of the tracheoles, exposing more SA for gas exchange
• Some larger insects like bees have high energy demands so have other methods of increasing gas exchange:
- Mechanical ventilation of the tracheal system is where muscular pumping of the thorax/abdomen actively pump air into the system, by changing the volume of the body, therefore changing the pressure in the tracheae and tracheoles, drawing air in or forcing it out. When the body expands air is sucked in.
- Collapsible enlarged tracheae or air sacs act as air reservoirs which are inflated or deflated by the contractions of the thorax and abdomen. They help increase the amount of air moved through the gas exchange system.
Why do bony fish need an exchange system?
• Although they don’t have to prevent water loss like insects, they have to overcome the viscosity of water (100x more than air)
• Also the lower oxygen content causing slow diffusion rates
large active fish like cod cannot rely on diffusion alone to reach the inner cells due to their small SA:Vol ratio
scaly outer surface doesn’t allow gas exchange
• It can also be hard to maintain a constant flow of water over the gills when the fish isn’t moving, and this water flow is necessary to keep the gill filaments apart, exposing their large SA.
What are the adaptations of the gills?
- Tips of adjacent gill filaments overlap, increasing the resistance to the flow of water over the gills slowing it down so more time for gas exchange
- filaments/lamellae increase SA
- rakers trap food and absorb it into the blood
- The water moving over the gills and the blood in the (gill filaments- where?) flows in different directions to maintain a steep concentration gradient so that the water always has higher concentration than water?? and a counter current exchange system is set up. Parallel/concurrent systems only extract 50% of oxygen flowing past as they reach equilibrium halfway through compared to 80% with bony fish
Where are the gills found and what are their features?
- They have gills in the gill cavity covered by a protective operculum (bony flap) which helps maintain flow of water over gills.
- The gills have a large SA- lamellae
- good blood supply
- thin layers
- a one-way flow of water across them to reduce the energy used to move the viscous water in and out of respiratory systems like lungs.
What method of ventilation do some primitive fish use and what do bony fish use?
- For some primitive cartilaginous fish like sharks when they stop moving the flow of water stops and the gills can’t be ventilated, as they rely solely on this- ram ventilation.
- Bony fish have another system: the mouth is opened and the floor of the buccal cavity (mouth) is lowered, increasing its volume and decreasing the pressure so that water moves in. Whilst this is happening the opercular valve is shut and the opercular cavity containing gills expands, lowering the pressure below the buccal cavity. The floor of the buccal cavity starts to move up increasing the pressure, so water moves out of it and over the gills.
- When the mouth closes the operculum opens and the sides of the opercular cavity move inwards. This increases pressure in the opercular cavity forcing water out the operculum. The floor of the buccal cavity is steadily moved up, so a steady flow of water is over the gills.
Process of inspiration
inspiratory centre in medulla oblongata of brain sends out nervous impulse
external intercostal muscles contract moving the rib cage up and out
internal intercostal muscles relax
increases volume of thorax/thoracic cavity
reduces pressure inside so draws air in from higher pressure outside
diaphragm contracts and flattens
lungs expand to reduce pressure activating stretch receptors so the inspiratory centre stops sending impulses
process of expiration
external intercostal muscles relax and ribs move in and down naturally due to gravity
internal intercostal muscles relax
decreases volume of thoracic cavity increasing pressure inside so air released
diaphragm involuntary muscles relaxes and curves in
elastic fibres in alveoli of lungs return to normal length due to elasticity and pressure on them
pressure inside and outside is now equal
stress receptors in lungs are deactivated
inhibition of respiratory centre stops
when do the internal intercostal muscles contract?
what else is needed?
when you cough or sneeze as there is a forced expiration so ribs move rapidly down and in
during this the external intercostals are relaxed
the abdominal muscles contract forcing diaphragm up to raptly increase pressure in lungs
what is the limitation of the bell jar?
doesn’t show ribs moving as glass jar cannot expand
what is a spirometer?
what is the trace of the volumes called?
What absorbs CO2?
What must the person do?
a device used to measure and record the volumes of air inspired and expired over time
spirograph/ kymograph
soda lime
block nose using clip
breathing rate
number of breaths per minute
tidal volume
volume of air inspired and expired in 1 breath usually measured at rest (500ml)/ (o.5dm3)
oxygen uptake
volume of oxygen absorbed by lungs in 1 minute
vital capacity
the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath
pulmonary ventilation/ventilation rate
a measure of the volume of air that’s moved into lungs in 1 minute (dm3min-1)
tidal volume (dm3) x breathing rate (min-1)
What needs to be considered with spirometer measurements to make it a valid trial?
age, health, size
male have larger lung capacities
how do you use a float chamber spirometer?
the subject sits at rest a breaths NORMALLY
the spirometer chamber is filled with medical grade oxygen and float on water
as the subject inspires air is drawn in from the chamber and the lid moves down
during expiration the expired air is returned to the chamber and the lid moves up
these movements are recorded on the trace of a kymograph or spirograph
what precautions must be taken when using a spirometer?
healthy subject
wear nose peg
fresh soda lime to absorb co2
sterile mouthpiece
medical grade oxygen
no leaks to make results inaccurate/ invalid
water chamber not overfilled- inhale water
What do the lines mean if the y axis is lung volume?
what does the y axis mean if the y axis is spirometer volume?
up= inspire down= expire
up=expire
down= inspire
expiratory reserve volume
the volume of air that can be forced out after a normal tidal expiration
inspiratory reserve volume
the volume of air that can be inspired over and above a tidal inspiration
vital capacity
equation
affected by?
the greatest volume of air you can move into and out of your lungs in breath= IRV+ERV+TV
affected by age, sex, athleticism and posture
residual volume
What keeps alveoli open?
the volume of air that remains in the airways and alveoli after forced expiration (1.5dm3)
trachea and bronchi kept open by cartilage and surfactant strops alveoli collapsing
why are transport systems needed?
- To supply nutrients and oxygen like if food is digested in one organ system but needed in all others for respiration and metabolism
- To remove waste products from cells to excretory organs
- Temperature maintenance In birds and mammals
- Hormone circulation if made in one place and needed in another
- Circulation of cells involved in defence
mass flow
The bulk transport of materials from 1 point to another as a result of a pressure difference between the 2 points
What are the components of the circulatory system?
- Circulatory fluid
- Contractile pumping device (heart or modified blood vessel)
- Tubes through which fluid can circulate (blood vessels)
example of an open circulatory system: What is blood called? what is the heart like? where is blood pumped to? what is the main vessel called? How does blood move between the tissues? What are the valves to the heart called? when does exchange occur? How else can circulation be affected? what is carried? How is the body cavity split?
invertebrates like insects
haemolymph
in the abdomen and tubular
haemocoel
dorsal vessel
slowly under low pressure due to low diffusion gradient and can’t be controlled
ostia
when the transport medium comes into contact with the cells
by body movements like muscle pump in insects and fish
not oxygen or carbon dioxide- trachea, but food and nitrogenous waste products and cells involved in defence against disease
a membrane and the heart extends along the length of the thorax and abdomen
example of a closed circulatory system:
Where does blood stay?
What pumps the blood and how is it pumped?
How is blood distributed?
How do things enter and leave?
what carries respiratory gases?
Describe blood vessels in invertebrates like earthworms:
Echinoderms, annelids and vertebrates: (fish and mammals)
blood stays in blood vessels pumped by heart rapidly under high pressure
adjusted on demand bu vasodilation/constriction to different tissues/organs
through capillary walls by diffusion
blood pigment
have the dorsal (upper) and ventral (lower) blood vessels connected by lateral vessels in every segment. The dorsal vessel receives blood from the lateral vessels and carries it towards the head. The ventral vessel carries blood to the segmental vessels. The dorsal vessel is the main method of propelling blood as its contractile, but there are also several contractile aortic arches (hearts) which propel blood.
Describe the single circulation system in fish:
How are active fish adapted?
- 2 chambered heart near gills
- Blood first travels to gills where it passes through capillaries, picking up oxygen but loosing pressure. It continues to travel around the body, back to the heart more slowly
- Efficiency of gas exchange is limited so activity levels are usually low, except in fish which have an efficient one. They have counter current gaseous exchange mechanisms in gills that allows them to take in oxygen from the water. They don’t regulate their own temperature as its determined by water temperature, and their body weight is supported by the water so metabolic demands are reduced.
Double circulation system :
why is it high pressure?
what does exchange occur between?
Why is it needed to be efficient?
- 4 chambered heart
- Deoxygenated blood travels into the right-hand side of the heart and is pumped to the lungs where it picks up oxygen. Oxygenated blood, returns to the left side of the heart which gives it a boost so that it can reach all other parts of the body quickly.
- Oxygenated blood that travels to an organ travels directly back to the heart, not another organ, apart from blood going to the gut, which then goes onto the liver via the hepatic portal vein before returning to the heart
- High pressure as only flows through one capillary network per circuit, so steep concentration, gradient and more efficient exchange
- Exchange occurs between blood and tissue fluid surrounding the cells of your body
- Very active, especially land mammals that maintain their own body temperature
pulmonary circulation
systemic circualtion
myogenic
right hand side of heart pumps blood to lungs only
the left side of the heart pumps blood to the rest of the body
contractions originate from the muscle tissue not nerve impulses to preserve resources
biozone pink
what do the valves do?
the atrioventricular valves prevent back flow of blood into atria when ventricles contract
the semi lunar valves prevent back flow of blood into ventricles when they relax
What separates the sides of the heart?
what is a hole in the heart?
septum
• The development of the septum isn’t complete until after birth, and the foetus; blood is oxygenated in the placenta so the blood in the heart is very similar and mixes freely.
• The gap closes in the days after birth, but if it doesn’t its called a hole in the heart and is heart as a murmur.
• Large holes may need surgery
What is the cardiac cycle?
what are the phases?
a sequence of events in 1 heartbeat
diastole
atrial systole
ventricular systole
What happens in diastole?
What happens in atrial systole?
What happens in ventricular systole?
Diastole:
• The atria and ventricles relax and blood flows into the atria of the heart from the veins at low pressure
• At the beginning of diastole the AV valves are closed but as pressure builds in the atria to higher that in the ventricles, they are forced open so blood can flow into the ventricles
Atrial systole:
• Both atrial walls contract pushing remaining blood into ventricles, so they are empty
• The sphincters where the vena cava and pulmonary veins enter the atria close to prevent backflow
• Once the ventricles are full of blood ventricular systole begins
Ventricular systole:
• As the ventricular walls start to contract pressure builds up to a point where it forces the AV valves closed
• As pressure continues to build the semi lunar valves will open when it higher than pulmonary arteries and aorta
• (de/oxygenated) blood flows into the arteries (names) which have elastic walls so can stretch to accommodate blood. The contraction or aorta walls helps valves prevent backflow of blood
What are the sound of the heart called and what causes them?
The sound is made by the valves closing
1st sound= lub (made by AV valve closing as ventricles start to contract)
2nd sound= dub (semilunar valves closing as ventricles start to relax)
stroke volume
cardiac output
the volume of blood pumped by the heart in 1 cardiac cycle (80cm3)
volume of blood pumped in 1 minute in litres
=stroke volume x HR
factors affecting HR
- Adrenaline
- Movement of limbs (stretch receptors)
- Levels of respiratory gases in blood
- Blood pressure -if it gets to high a safety mechanism prevents HR increasing further
Describe the initiation and control of the cardiac cycle
- The heartbeat originates in the wall of the right atrium due to a region of specialised muscle tissue – the Sino-atrial node (SAN/pacemaker)
- The SAN sends out a wave of electrical impulses across both atria, causing them to contract (atrial systole)
- Non-conductive tissue prevents the spread of the impulse to ventricles allowing time for the atria to complete their contraction
- The second node at the top of the septum- the atrioventricular node (AVN) picks up the impulse (waves of depolarisation) and passes it to the ventricles, but with a slight delay to ensure the atria have stopped contracting.
- The impulse is passed down specialised muscle fibres in the septum called the bundle of His
- This carries the impulse to the apex (base) of the ventricles
- The bundle of His is made of pukinje or purkyne fibres which penetrate though the septum between the ventricles causing them to contract, pushing blood up and out through the arteries. As the fibres spread through the walls from the apex, the contraction starts at the apex allowing more efficient emptying of them.
What do electrocardiograms do?
- Monitor the electrical activity of the heart by measuring tiny electrical differences in your skin due to the electrical activity of your heart
- Electrodes are stuck to clean skin to get good connection. Signal fed into machine
What is tachycardia?
when is is harmless?
when is it harmful?
- Very rapid heartbeat over 100 but evenly spaced
- Normal when exercise, fever, frightened or angry
- Abnormal is caused by problems in electrical control or heart and may need medication or surgery
What is bradycardia?
when is it harmless?
When is it harmful?
- Heart rate slows down to below 60bpm and evenly spaced
- May be due to fitness
- Can be serious is severe-electrical impulses from San not passed on properly so may need an artificial pacemaker
What is an ectopic heartbeat?
What causes it?
What is the normal amount to have them?
When are they serious?
- Extra beats that are out of the normal rhythm flowed by longer than normal gap.
- Can be caused by early contraction or atria (p wave is early) or ventricles (taller and wider QRS complex)
- Most people have one a day
- Can be serious if more frequent
What is atrial fibrillation?
What does it look like on a graph?
What causes it?
- A type of arrhythmia which is an abnormal rhythm
- Small and unclear p wave
- Rapid electrical impulses are generated in the atria which contract very fast (fibrillate) up to 400x a minute
- They don’t contract properly though and only some are passed into ventricles which contract less often so blood isn’t pumped effectively
Howe is blood pressure measured?
What is a normal value?
- Digital sphygmomanometer is used with a stethoscope built into cuff. The cuff is inflated, cutting off the blood circulation to lower arm
- Air is slowly let out of the cuff. The pressure at wich the blood sounds frst appear is noted by a tapping sound and is the blood under the highest pressure- left ventricle. This gives systolic pressure
- The blood sounds return to normal when even the lowest pressure blood can get through cuff. This gives diastolic blood pressure.
- 120/80 mmHg is normal
why is the right ventricle wall thinner?
less distance to pump
also less resistance as lung is a spongy organ and has fewer arterioles which provide the most resistance
what is the autonomic nervous system?
What does the parasympathetic nervous system do?
What does the sympathetic nervous system do?
part that controls involuntary activity
decrease HR
increase HR
Arteries
Function:
structure:
What are arterioles?
Structure:
What is found where arterioles meet capillaries?
why may the artery have folding in the walls?
carry blood at high pressure to tissues
tunica intima/interna- inner layer consisting of a 1 cell thick endothelium lining the lumen, and a network of connective tissue and a layer of elastic fibres. smooth surface reducing friction
tunica media- thick layer of smooth muscle strengthening artery resisting high BP and can contract to reduce flow. A thick layer of elastic tissue allowing blood vessel to stretch to maintain pressure- when it stretches pressure lowers then as it recoils pressure increases again, evening out fluctuations
tunica adventitia/externa- covers outside of artery consisting of collagen which is tough to prevent over stretching which would damage wall
smallest arteries which lead into capillaries
walls contain lots of smooth muscle so are important in controlling blood flow through contractions - controlled by autonomic nervous system but can also respond to external factors like pH and levels of gases
rings of smooth muscle called pre-capillary sphincters which allow blood to completely bypass a capillary bed if needed
so it can expand from blood
Capillaries
Function
structure
How do white blood cells leave?
exchange materials with cells so have to reach close to them so there are lots- large SA:vol ratio
small lumen causing friction slowing blood down and lowering pressure for exchange as it allows time and for the thin walls
tunica interna- 1 cell thick walls with an endothelial layer surrounded by a basement membrane. overall large volume than arterioles helps slow movement
squeeze through intercellular junctions
Veins
Function:
Structure:
venues
return blood to heart
same 3 layers from artery but tunica media is thinner as doesn’t have to withstand as much pressure and aren’t subjected to as much stretching force, and flow of blood is even with no pulse
large lumen speeds up blood flow from capillaries and compensates for the lack of speed, so the same volume enters the heart as leaves. as less of the blood is in contact with the walls friction is reduced
tuna externa is relatively thicker because of thinner media but actually the same as arteries
valves (flaps of inner lining) ensure one way flow to heart as no pulse to do this like in arteries
the force needed to push blood along comes from the muscles around the vein contracting due to normal activity and valves prevent bxackflwo when they realx. The thin vessel wall means the force isn’t resisted by the vessel
The breathing movement of chest also act as a pump as pressure changes and squeezing actions move blood in veins of chest and abdomen towards heart
vey thin walls with a little smooth muscle, and several join to forma. vein
What are the functions of blood?
Transport:
- oxygen and CO2 to and from respiring cells
- digested food from small intestine
- nitrogenous waste products from cells to excretory organs
- chemical messages (hormones)
- food molecules from storage compounds to cells in need
- platelets to damaged areas
- cells and antibodies involved in immune response
steady temperature
acts as a buffer to minimise pH changes
What is blood made of?
What is haemolymph made of?
55% plasma which is mainly water but also has
- dissolved glucose
- amino acids
- mineral ions
-CO2
- hormones
- large plasma proteins like albumin and fibrinogen (blood clotting) and globulins (transport and immune system)
45% cellular components:?? or above too?
Red blood cells (erythrocytes)
white blood cells (leucocytes)
platelets (fragments of large cells called megakaryocytes found in red bone marrow for clotting)
90% plasma with aa, proteins, sugars and inorganic ions
10% haemocytes involved in clotting and internal defence
Why do you get tissue fluid?
What impact does albumin have?
How does tissue fluid reenter the capillaries?
What happens if too much tissue fluid?
some blood leaves the capillaries to bathe the surrounding cells do diffusion can occur, providing O2 and nutrients and removing waste.
this is because blood flowing through arterioles init capillaries is under pressure from surges of blood when the heart contracts- hydrostatic pressure is higher than osmotic pressure
it is a protein which remains in the capillaries and gives them a relatively low water potential compared to tissue fluid so water (from tissue fluid) moves back into capillaries by osmosis
by the venous system the hydrostatic pressure has fallen as lots of fluid lost and (osmotic pressure doesn’t really change) so water can move back in - 90% of tissue fluid returns. This allows substances like wast back in.
tissue swelling- odema
How is tissue fluid different to plasma?
What does tissue fluid supply cells with and what does it remove?
doesn’t have large plasma protein molecules in it as they were too big o pass through the tiny gaps between the endothelial cells
glucose, amino acids, fatty acids, salts and oxygen
CO2 and urea
What is oncotic pressure?
osmotic pressure caused by proteins (albumin) in blood plasma by pulling water into circulatory system
What happens to the remaining 10% of tissue fluid?
what happens when lymph capillaries join?
How do they prevent fluid leaving?
How is it different to plasma and tissue fluid?
How does lymph fluid move?
How does it return to there blood?
enters a system of microscopic tubes called lymph capillaries part of the lymph system
form lymph vessels
have valves
has less oxygen and fewer nutrients and contains fatty acids which have absorbed into lymph through lacteals in villi of small intestine
squeezing of body muscles, valves and negative pressure in chest when we breathe in. is slow as no heart.
through the right and left subclavian vein near collar bone
What are found at intervals along lymph vessels?
What do they do?
What happens to them at times of infection?
Where can they be found?
lymph nodes
part of the immune system as they produce lymphocytes, a type of white blood cell that produce antibodies which can be passed into blood
also intercept bacteria and other debris from the lymph which are ingested by phagocytes found in the nodes
swell up
neck, stomach, armpits, groin- lymph glands
Why can’t carbon dioxide accumulate in the blood?
How can it be carried?
The acid it forms could lead to fatal changes in pH
1. dissolved in plasma (5%)
The rest diffuses into red blood cells
2. combined with Hb (10-20%) . it combines with the amino group in polypeptide chains of haemoglobin to form carbaminohaemoglobin. the amount carried like this depends how much oxygen the haemoglobin is carrying
3. as hydrogen carbonate ions
What is haemoglobin?
How many oxygen can each haemoglobin carry?
What is the equation?
red pigment that carries oxygen
large globular conjugated protein made of 4 polypeptide chains (2 alpha, 2 beta), each with an iron containing haem prosthetic group
there are 300 million haemoglobin molecules in each red blood cell and each molecule binds to 4 oxygen
Hb + 402 Hb(02)4 (oxyhaemoglobin) reversible
How do hydrogen carbonate ions form?
Equation
Carbon dioxide diffuses into blood stream and into red blood cells
it combines with water to form carbonic acid (H2CO3 -) using the enzyme carbonic anhydrase (found in red blood cell cytoplasm)
carbonic acid then dissociates into ions as it is unstable - hydrogen ions and hydrogen carbonate ions (HCO3 -)
CO2 + H2O H2CO3 H+ + HCO3 -
What happens to the hydrogen ions?
What happens to the hydrogen carbonate ions?
What the process do the hydrogen carbonate ions cause?
Hb accepts some of them acting as a pH buffer allowing large amounts of carbonic acid to be transported to the lungs without major changes in blood pH. First the oxygen its carrying must dissociate and this can then go into the cells the Co2 is being removed from- more Co2 release means more ready dissociation so more o2 for respiring tissues.
It does this in a reversible reaction to form haemoglobinic acid which can be a substrate for carbamino formation which binds CO2 to haemoglobin
they diffuse out of the red blood cell into the plasma along a concentration gradient where they combine with sodium to form sodium hydrogen carbonate- neutral charges.
the loss of the -ve hydrogen carbonate ions from the red blood cell leaves them positively charged so negative chloride ions diffuse into the red blood cells to balance the charges- chloride shift
How is a steep concentration gradient of CO2 maintained?
by removing CO2 and converting it to HCO3 -
How is CO2 released at the lungs?
there’s a relatively low concentration of CO2 at the lungs so so carbonic anhydrase catalyses the reverse reaction breaking down carbonic acid into CO2 + H2O. Co2 is released
The HCO3 - ions diffuse back into erythrocytes and react with hydrogen ions to form carbonic acid
Cl- ions diffuse out of red blood cells into plasma down electrochemical gradient
What is positive coopertativity?
How does it affect the graph shape and why?
How is concentration gradient of oxygen maintained?
when 1 oxygen molecule binds to a haem group the molecule changes shape so its easier for the next one to bind
when unloading oxygen at the body cells, once the first oxygen molecule is released the molecule changes shape so its easier to remove the remaining oxygen
this creates a rapid rise at the beginning of the graph as red blood cells can be rapidly loaded with O2 when there is a decrease in levels. also because of low pH in tissues compared to lungs
as it is bound to haemoglobin, the free oxygen concentration in the erythrocyte maintains low so steep gradient stays until saturated
What does a oxygen dislocation curve show?
the affinity of haemoglobin for oxygen
at higher PO2 (partial pressure for oxygen) more haem groups are bound to oxygen so easier for oxygen to be picked up
low PO2 few haem groups are bound to O2
partial pressure
when you have a mixture of gases each gas contributes to part of the pressure. the overall pressure of gases doesn’t change but the partial pressure of oxygen would
What is the Bohr effect?
How do higher levels of CO2 affect the graph?
the effect of CO2 on haemoglobin
as partial pressure of CO2 rises, haem gives up O2 more readily (lower affinity to oxygen) which helps as in actively respiring tissues there is a high PCO2.
When there are higher levels of CO2 the curve shifts to the right so lower % saturation of haem
Where does haemoglobin have a high affinity for oxygen?
lungs, surrounding capillaries and where its well ventilated so lots of oxygen. When your not very active, (very active is small mammals and birds) only 25% of oxygen carried by erythrocytes is released into body cells and the rest is a reservoir incase demand increases suddenly
What does the graph for a foetus look like?
Why?
How does this happen?
What else has a graph shifted to the left and why?
shifted to the left
to ensure the foetus gets enough oxygen as the oxygenated mothers blood runs close to the deoxygenated foetal blood in placenta and oxygen must be transferred.
Fetal Hb is different as the 2 beta chains are replaced by 2 gamma chains so it has a higher affinity to oxygen that the mothers so can take up oxygen at low pp like the placenta causing the adult oxyhaem to dissociate at lower ppO2, otherwise it wouldn’t give the O2 up
llamas as in mountains high altitude so higher affinity for oxygen as better at hanging onto it/ doesn’t dissociate readily
What are the benefits of the Bohr shift?
- actively respiring tissues need more oxygen
- to release more energy in aerobic respiration
- actively respiring tissue produces more CO2
- haemoglobin is involved in the transport of CO2
- less haemoglobin is to combine with O2??
- Bohr shift causes more oxygen to be released
What is myoglobin?
Where is is found?
What is it used for?
How does it get its oxygen?
specialised form of Hb found in muscle cells that has a higher affinity for oxygen than haemoglobin so can release at very low pp.
used as a store of O2 to be used if the ppO2 gets too low due to active respiring muscle cells
takes O2 from Hb
What are the structures of the xylem and how do they help its function?
What are the 2 main functions?
- made from dead cells with no or perforated end walls and no cytoplasm- allows water and mineral ions to move through easier
- xylem tubes are narrow?- force of adhesion is stronger to support transpiration
- lignified walls- reinforce vessels so don’t collapse under transpiration pull
- non lignin pits- allow water to move transversely from cell to cell
- lignin first laid down in spiral- prevents collapse, gives support, adhesion of water, prevents vessel being to rigid and allows flexibility or stem/branch
- transport mineral ions and water from roots to shoots and leaves
- support and strengthen plant
What are the features of the phloem and how do they help its function?
- reduced cytoplasm and organelles and no nucleus. - aid the transport of assimilates and minerals from leaves to cells for respiration and synthesis of useful molecules- they need sugars and aa. reduce resistance to flow
- companion cells have lots of mitochondria- very active as provide materials to keep sieve tube elements alive and involved in transport, and ribosomes to make ATP and nucleus and genes for proteins
- plasmodesmata are microscopic channels through cellulose cell walls that link cytoplasm of sieve tube element and companion cell- allow transport of molecules
- sieve plate formed by perforated end wall allow mass flow
How do mineral ions move into the root hair cell?
How do mineral ions aid the movement of water into the root hair cell?
- Mineral ions either move down their diffusion gradient into the root HAIR cell or are actively transported across the membrane into the root hair cell using energy from ATP
- minerals lower the water potential in the cytoplasm of the root hair cell so water crosses the cell membrane by osmosis down the water potential gradient with its dissolved mineral ions like nitrates, through the cortex until it reaches the xylem. as it moves out of each cell it lowers the water potential to aid the gradient.
What are the adaptations of the root hair cell?
microscopic so can penetrate between soil particles
large SA: vol ratio
thin surface layer on hairs
gradient created by active transport
Describe the apoplast pathway through the cortex
Why does this path have the least resistance?
What is negative about this path?
water travels in between cellulose strands of the cell wall and through spaces between the cells. the water doesn’t pass through any membranes so the mineral ions are carried with the water. Simple diffusion
This pathway has the least resistance as cell walls are readily permeable so most water uses this path. cohesive forces between water molecules pull water along creating a constant flow
no opportunity to select what comes in- everything dissolved in water travels through
Describe the symplast pathway through the cortex
What is another word to describe cells linked by plasmodesmata?
water enters the cytoplasm through the cell membrane of the root hair cell and then travels from cell to cell through the plasmodesmata. travels by osmosis
continuous network of interconnected plant protoplasts
Describe the vacuolar pathway through the cortex
similar to symplast pathway but water travels through vacuoles aswell
What is the endodermis?
What is the casparian strip?
What does it do?
Why is this needed?
The endodermis (or starch sheath because starch granules are present) is a layer of cells surrounding the xylem in the root
The root endodermal cells have a band of waterproof Suberin in their cell wall forming the casparian strip
It blocks the apoplast pathway between the cortex and the xylem forcing water into the symplast pathway just before the endodermis. To get to this cytoplasm it therefore must go through a plasma membrane which is selectively permeable
this removes potentially toxic solute from reaching living tissues as membranes would have carrier proteins to admit them
What happens after the casparian strip?
How do mineral ions get to the xylem?
once in the cytoplasm, the water can continue through the symplastic pathway or return to the apoplastic pathway where it continues to the xylem.
the membrane in the endodermal cells contains a number of protein carriers that regulate transport. this is how mineral ions are transported in by active transport, as there are more in the xylem. This helps water osmose through by the symplast.
What causes root pressure?
What does this do?
What evidence is there for active transports involvement in root pressure?
what are the limitations
active transport of mineral ions from cortex into the xylem
pushes water up the xylem
- poisons like cyanide affect mitochondria and prevent function of ATP. if apple dot root cells there is no energy supply and root pressure disappears.
- root pressure increases with rise in temperature and falls with a decrease suggesting chemical reactions are involves
- if levels of O2 drop root pressure falls - respiration
- xylem sap may exude from cut end of stems. Xylem sap is forced out of special pores at the end of leaves in some conditions like overnight when transpiration is low- Guttation.
can’t force water all the way to the top though
How does meristem tissue undergo cell division to form xylem and phloem?
Is a stem cell so differentiates by cell elongation, deposition of lignin and end walls break down????
How does water move up the stem?
Why are they passive?
root pressure
capillary action
transpiration pull
xylem is non living
If ventricular pressure is increasing what is happening to the volume?
Where is the lowest ventricular pressure on an ECG?
decreasing
flat bit at end during diastole
What is the transpiration pull?
Describe the cohesion tension theory
What does it rely on?
Describe how water leaves the leaf
when water is drawn up the xylem in a continuous stream to replace water lost by transpiration
water molecules are attracted to each other by hydrogen bonds (weak electrostatic forces of attraction) since they are polar between delta positive H and delta neg O of another water molecule. This creates cohesive forces holding the water molecules together in a continuous column.
As water is lost form the top by evaporation (not transpiration) the whole column is pulled up which creates tension in the lignified xylem vessels
An unbroken column of water
Water vapour evaporates from the mesophyll cells just below guard cells and diffuses out of the leaf through pores in the epidermis called stomata because it is less humid out there- down concentration gradient. More water then osmoses into the mesophyll cells to replace lost water from high to low water potential, from the app-last and symplast pathways.
loading tension
unloading tension
ppO2 at which 95% of pigment is saturated with O2
if have a higher affinity for oxygen, then the loading tension will be lower as need less oxygen to be that saturated
ppO2 at which 50% of pigment is saturated with O2
What is one function of mammalian blood not performed by insect haemolymph?
What is two functions of insect haemolymph not performed by mammalian blood?
transport oxygen
fluid pressure can facilitate moulting in insects and contains antifreeze like glycerol in plasma
If ventricular pressure is increasing what is happening to the volume?
decreasing
Why if fatal haemoglobin replaced after birth?
oxygen wouldn’t be related readily enough as affinity is too high and their foetus wouldn’t be able to extract oxygen from them
loading tension
unloading tension
ppO2 at which 95% of pigment is saturated with O2
ppO2 at which 50% of pigment is saturated with O2
Transpiration
3 processes:
the loss of water vapour from leaves and plants
- osmosis from xylem to mesophyll cells
- evaporation from surface of spongy mesophyll cells into the intercellular spaces (sub stomatal cavity)
- diffusion of water vapour from the intercellular spaces out through the stomata. There is a water vapour potential.
transpiration stream
uninterrupted stream of water and solutes taken up by the roots and transported via the xylem vessels to the leaves where it evaporates into the substomatal cavity
How do stomata affect the rate of transpiration?
When turgor pressure is low, the asymmetrical configuration of the guard cell walls closes the pore to prevent water loss.
When conditions are favourable, guard cells pump in solutes by active transport increasing their turgor. Cellulose hoops prevent cells swelling in width so they extend lengthways. inner walls in guard cells are less flexible so cells become bean shaped and pore opens to let water out.
When water becomes scare hormonal signals from roots trigger turgor loss so stomatal pores close - often at night when co2 isn’t needed for photosynthesis but a few remain open to get o2
Why is the transpiration stream useful?
- water is required for photosynthesis
- water is required for cells to grow and elongate
- water keeps the cells turgid for support
- flow of water carries minerals up the plant
- evaporation of water cools the plant
- mineral ions and products of photosynthesis are transported in aqueous solution
Factors affecting rate of transpiration
NUMBER OF LEAVES- more water leaves
NUMBER, SIZE AND POSITION OF STOMATA- more water leaves
PRESENCE OF CUTICLE- waterproof layer stops water
LIGHT- needed for photosynthesis and causes stomata to open for age exchange so increases the rate of water movement and increases evaporation. once open no further effect is gained by increasing light intensity
TEMPERATURE- more kinetic energy of water molecules so increases rate of transpiration. Also increases concentration of water vapour external air can hold before saturated so increases rate. very high temperatures cause stomata to close
HUMIDITY- amount of water in air compared to amount it can hold. High humidity reduces rate as reduces gradient- increases water vapour potential around stomata (not leaf)
AIR MOVEMENT- hairs on leaf surface trap air and decrease movement as water vapour accumulates at boundary layer so reduces gradient and rate of transpiration. Air movement can increase gradient and rate of transpiration.
WATER AVAILABILITY- dry plant has reduced rate, as less water to leave and stomata close to reduce loss and because they loose fluid themselves
why is a photometer used to measure transpiration?
Why is is hard to measure water uptake directly?
What 2 things do you need to remember?
How can you measure the effect of variables of temperature, light and wind?
hard to measure direct so instead assume water uptake is directly proportional to water vapour loss by transpiration but could be for photosynthesis
This is because is you just collect evaporated water some would have evaporated directly from the soil, and some would be water vapour from respiration not just transpiration
stem is cut underwater and transferred to apparatus to avoid introducing air bubbles to stem which would cause airlock preventing water movement
leaves dried as would create humidity reducing transpiration
heater, lamp and fan
What is the equation for rate of water uptake?
units?
when do you start measuring?
Pie x r2 x distance= volume
volume/time= rate
cms-1
when rate of movement of bubble is constant
why do terrestrial organisms loose water at exchange surfaces?
they are permeable and there is a higher concentration inside organism that outside
Beginning with the evaporation of water from the leaf surface, describe how water could be pulled up through a plant entirely within the apoplast (except for in the Casparian strip).
(There is outward diffusion of water vapour through the leaf stomata)
The humidity of mesophyll air space air falls;
Water evaporates from the wet cell walls of mesophyll cells;
Water passes from the leaf xylem along the apoplast route/along the cell walls (to replace what’s lost at the evaporating surface);
The column of water is drawn up the xylem (leaf, then stem, then root xylem);
It’s under tension/negative pressure;
Water molecules cohere;
They adhere to the sides of the xylem cells/vessels/tracheids;
They are pulled in from the root cell walls of the pericycle cells (and from endodermal walls);
They can’t pass along the radial walls of endodermal cells because of the hydrophobic/suberised Casparian strip;
They pass through the endodermis via the symplast route;
Using plasmodesmata;
They are drawn along cortical cell walls (apoplast);
And via root epidermal cell walls/cell walls of the root hairs from the soil solution.
How to respiratory poisons affect root pressure?
They inhibit ATP so no energy for active transport of mineral ions by specific carrier proteins
Why doesn’t root pressure cause water and solutes to be squeezed the roots?
root pressure occurs in the xylem so casparian strip of endodermal cells prevents it
Comparing transpiration of upper epidermis of 2 leaves
(Remove the leaves from freshly cut shoots)
Determine the surface areas of the two leaves, using graph paper and counting squares;
Smear petroleum jelly (all) over the lower epidermis (of each type of leaf);
Smear petroleum jelly over the petiole (of each type of leaf);
Weigh the leaves immediately, leave them for the same time attached to the string, reweigh;
All conditions the same, e.g. temperature/light and dark/air currents;
Subtract the final mass from the initial mass (for water loss through transpiration);
Calculate transpiration per cm2 of the upper epidermis
Translocation
the movement of assimilates (sugars and other chemicals made by plants during photosynthesis) - mass flow
What are sugars transported as in translocation and why?
what is a source- examples
what is a sink- examples
Sucrose because its not used in metabolism as readily as glucose so is less likely to be metabolised during the transport process
The part of the plant that releases sucrose into the phloem EG green leaf, germinating blubs and seeds, tubes and roots that unload stores at begging of growth period
The part of the plant that removes sucrose from the phloem EG bulbs in winter, flowers, growing parts of roots, stems, leaves, developing seeds and fruit
What is a symport and antiport?
a symport cotransporter protein is where both the substances are transported in the same direction
antiport is different directions
What is the evidence for the transport of sucrose in phloem?
- Radioactive tracers - radioactive CO2 given to photosynthesising plant and sugars in phloem later are radioactive
- rings of trees can be cut through vascular bundles so you can see sucrose is in the phloem which oozes out
- aphids suck out the contents of the phloem. if you cut the aphid stylet off you can test the fluid in them
- sucrose concentrations higher in day due to photosynthesis
Evidence for the use of active loading?
- mitochondria produce ATP is aerobic respiration show active transport
- metabolic posions stop respiration so not ATP or active transport
- sugar flow rate is too fast it can’t be passive
- pH changes due to the H+ concentration
- sucrose concentrations can be measured
What is the evidence against the mechanism?
- No explanation for the presence of sieve plates that impede mass flow. Although it is suggested that they are a means of sealing off damaged elements, with rapid deposition of callose forming slime plugs. The sugar solution moved through the plasmodesmata into neighbouring undamaged cells.
- The theory suggests that all materials being transported in the phloem should travel at the same speed, but this is not the case.
What are the adaptations of most plants to reduce water loss?
- leaves have waterproof waxy cuticle so water can only be lost through stomata
- stomata mostly on lower leaf surface which is cooler as it doesn’t face the sun therefore reducing the rate if diffusion
- stomata close in dark when don’t need co2 as no light for photosynthesis
What are xerophytes?
Examples
plants that live in dry conditions, either bot and breezy or cold if water is frozen
Marram grass in sand dunes which don’t retain water and are windy and cacti
Xerophyte adaptations to water loss
- less stomata- reduces water loss by transpiration but also ability to gas exchange
- stomata in sunken pits- shelters water from air movement so high humidity builds up reducing the diffusion gradient so reducing rate of transpiration eg. marram
- hair leaves-trap water vapour lowering diffusion gradient eg. marram grass
- Thick waxy cuticle- prevents water loss eg. marram
- leaf may be rolled- lower surface inwards allowing humidity to build up eg. marram grass. this also means threes a low water pot. inside leaf.
- smaller leaves- eg. cactus spines or plant may loose leaves so less SA for transpiration
- Succulents- store water in specialised parenchyma tissue in stems and roots eg. cacti
- root adaptations- long tap roots eg. marram or shallow widespread eg. cacti to take up water before it evaporates. marram also have a mat of widespread rhizomes which have roots that change environment allowing it to hold more water
- some plants become dormant or die leaving seeds to quickly germinate when it rains
- densely packed spongy mesophyll- reduces the SA exposed to air inside the leaves so less water evaporates into leaf air space
What is a hydrophyte?
example
plants that live in water or permanently saturated soil
water lily
What are the adaptations of hydrophytes?
- cell wall prevent too much water being absorbed
- floating leaves have stomata on upper surface so gas exchange can occur with the air which has more gases than water eg. water lily’s
- stomata always open on upper surface as water loss isn’t an issue
- thin or no waxy cuticle as loss by transpiration and loss of turgor not an issue
- reduced structure of plant as water supports the leaves and flowers so no need, and less veins like xylem as less need for transporting water and support eg. water Lilys
- wide flat leaves capture as much light as possible on the surface eg. water Lilys
- reduced root system as water can diffuse directly into stem and leaf tissue
- buoyancy is aided by being thin and flat and having air sacs so they can get light for photosynthesis on water surface. Aerenchyma are specialised parenchyma with air spaces caused by apoptosis. they also allow a low resistance pathway for movement of eg. oxygen to tissues especially in low oxygen conditions
Why do plants need transport systems?
- They are very tall
- metabolic demands require transport of materials
- small SA:vol ration even though leaves have a large one, when taking into account with stems and roots they don’t so can’t rely on diffusion alone t meet needs of plant
Evidence for cohesion tension theory
- changes in diameter of trees. when transpiration is at its height during the day the tension in the xylem vessels is at its highest so the tree shrinks in diameter, and at night when it is lowest the diameter increases which can be tested my measuring the circumference of a tree
- when a xylem vessel is broken like when you cut flower stems, air is drawn in to the xylem rather than water leaking out
- if a xylem vessel is broken and air is pulled in, the plant can no longer move water up the stem as the continuous stream of water molecules from cohesive forces is broken
what is a plant that possesses transport tissues?
vascular
why should you transport a seedling at night?
closed stomata as dark so less transpiration so less water loss to prevent seedling dying, as the disturbed roots are not yet taking in water to compensate. the evening is also cooler
