b3 Flashcards
what is gas exchange?
process by which organisms obtain and return carbon dioxide and oxygen to and from the environment
two types of gas exchange
internal
external
concentration gradient
difference in concentration of a substance between two locations. requires for passive transport, including diffusion
alveolus
tiny spheres of one-cell thick tissue in the lungs.
what is each alveoli covered by?
capillary blood supply
surfactant
thin phospholipid and protein monolayer film. lines the inner surface of every alveolus
what lines the surface of every alveolus?
surfactant
what does trachea branch off to?
2 bronchi -> broncioles (small air tubes ultimately attached to the trachea)
How does SA:V affect gas exchange?
Higher SA:V leads to better gas exchange
how are concentration gradients maintained for gas exchange in animals with lungs?
as cellular respiration proceeds, the oxygen concentration in blood drops. frequent ventilation (i.e. breathing) means that there is a high oxygen concentration in the lungs. therefore concentration gradient betweeen lungs and tissues
how does structure of alveolus facilitate its function?
only one cell thick -> shorter distance for efficient diffusion. many small alveoli mean high SA:V ratio thus, efficient gas exchange
how does surfactant prevent lung collapse?
surrounding alveoli walls with monolayer of phospholipids mean that will not collapse
adaptations of gas exchange surfaces
thin (one cell thick) -> shorter distance of diffusion
moisture -> gases dissolve into water
large SA:V by lots of small surfaces
high permeability
what is external respiration
exchange of oxygen between alveoli and capillaries
what is internal respiration
exchange of oxygen between red blood cells and tissues
why is cellular respiration a form of gas exchange?
oxygen gas turns into carbon dioxide
which aspect of the body must have a high oxygen concentration for passive transport to occur?
alveoli
how is the high oxygen concentration of alveoli maintained?
when oxygen concentration drops, we exhale and replace. this exhalation is triggered by an increase in carbon dioxide levels
example of an adaptation to sustain concentration gradients
countercurrent gas exchange in fish
why does countercurrent exchange work to diffuse oxygen in fish?
oxygen concentration is always higher in water than in blood -> oxygen will move into blood
how does countercurrent exchange work?
fish swallow water with dissolved oxygen, and push water over the gills. at the same time, the blood stream moves in the concurrent direction. there is always a concentration gradient between the two flows and therefore, oxygen exchange occurs
structure of mammalian respiratory system
trachea (with adaptations such as cilia or cartilage) branch off into two bronchi. Bronchi branoff into many broncioles, each of which are connected to alveoli. the entire structure (from trachea down) is covered by lung tissue.
how does gas exchange in the capillary work?
alveoli is surrounded by capillary. deoxygenated blood enters via vein. due to the concentration gradient of oxygen and carbon dioxide, oxygen moves from the alveoli to the capillary; and carbon dioxide moves from the capillary to the alveoli. type two pneumocytes produce surfactant, which stops alveoli collapsing on expiration
inspiration
process of inhalation in which the diaphragm contracts (and pulls down) due to signal from nerves. external intercostal muslces are signalled by nerves to contract, and the internal intercostal muscles relax and stretch -> pushing the ribs out. this causes an increase in lung volume and thus, decreasse in lung pressure. as the atmospheric pressure is higher than that of the lungs, air moves into the lungs
ventilation
exchange of air between lungs and the environment (i.e. breathing)
expiration
process by which air is exhaled. diaphragm relaxes and is pulled back up. external intercostal muslces relax, and (if a forced exhale), internal intercostal muscles can contract and further pull in the ribs. this results in decreased lung volume adn thus, an increase in pressure. as the pressure inside the lungs is greater than that of the atmosphere, air is pushed out of the lungs (through airway) into the environment. this causes an exhale
diaphragm
thin, dome-shaped skeletal muscle that sits below sternum, ribcage and spine.
partial vacuum
pressure change caused by lungs increasing in volume (and thus, decreasing in pressure)
tidal volume
volume of fresh air inhaled and exhaled in a typical breathing pattern
inspiratory reserve volume
volume of air a person could forcefully inhale beyond normal tidal volume
expiratory reserve volume
volume of air a person can exhale beyond normal tidal volume through a forceful exhale
vital capacity
potential lung volume during deliberate/forced inhale and exhale
what is reserve volume
volume of air you wont exhale because body is keeping as reserve
haemoglobin
oxygen transport protein found in red blood cells
saturation
how many oxygen molecules are bound to haemoglobin
cooperative binding
the fact that each oxygen molecule that binds to haemoglobin makes it easier for the next one to bind
allosteric binding
carbon dioxide binds directly to the polypeptide of haemoglobin, which changes its shape and reduces the haemoglobin’s affinity for oxygen
foetal haemoglobin
distinct haemoglobin that fetuses have which make it have a higher oxygen affinity than mother’s Hb
placenta
highly vascularised tissue that connects bloodstreams of pregnant women to the fetus
oxygen partial pressure
pressure exerted by a gas in a mixture of gases
how does the bohr shift benefit respiring muscles
actively respiring tissues accumulate more carbon dioxide. as blood circulates these tissues, carbon dioxide binds to haemoglobin, which reduces the oxygen affinity. this causes oxygen to dissociate from haemoglobin, so it is delivered to cells in need
what is the binding of oxygen to Hb called?
cooperative binding, as the shape change causes the Hb increases the affinity of oxygen
most stable form of haemoglobin
when 4 oxygens are binded
x-axis of oxygen disssociation curve
partial pressure of oxygen
y-axis of oxygen dissociation curve
%saturation of Hb
what does the shape of the oxygen dissociatin curve mean
we dont have to live in extremes, and oxygen will respond quickly
what is the shape of the oxygen dissociation curve
non-linear sigmoid dissociation curve
why is the oxygen dissociation curve non-linear
cooperative binding
what does it mean when oxygen in bloodstream is high (terms of oxygen dissociation curve)
high saturation of Hb therefore, oxygen won’t dissociate from Hb to tissue
why does the shape of the oxygen dissociation curve rapidly increase ~centre?
increased oxygen affinity
what happens to the oxygen dissociation curve when we inhale
small increase in oxygen leads to a big increase in saturation
what does it mean if a tissue has low oxygen concentration
oxygen has been used in cellular respiration -> low saturation of haemoglobin, as the oxygen leaves to go into muslces
what happens to oxygen bound to Hb when oxygen concentration of tissue is low
oxygen leaves haemoglobin
what is the bohr shift
change in oxygen dissociation curve at a low pH/high carbon dioxide concentration
what is the impact of carbon dioxide in the blood?
carbon dioxide decreases the pH of blood, which alters the shape of haemoglobin and decreases oxygen affinity
AND
carbon dioxide binds to the allosteric sites of Hb,w hich decreases oxygen affinity
what is created when carbon dioxide binds to haemoglobin
carbaminohaemoglobin
what does the bohr shift causes?
lower oxygen affinity at higher oxygen concentrations -> oxygen detaches more readily
why would a tissue have high carbon dioxide concentration
actively respiring
what does the bohr shift permit
fast rate of cellular respiration to continue, as actively respiring muscle and actively accumulate carbon dioxide
what is the difference between fetal oxygen dissociation curve and maternaloxygen dissociation curve?
fetal experiences higher oxygen saturation at the same pressure
what does the difference in oxygen affinity of fetal and maternal haemoglobin permit?
gas exchange in the placenta. transfer of oxygen will happens naturally due to concentration gradient AND due to increase fetal haemoglobin oxygen affinity
cuticle
waxy lipid layer that covers surface of leaves and prevents uncontrolled/excessive leaf water loss by evaporation
epidermis (in plants)
small layer of cells at surface of leaves that secrete the cuticle that coats cells
palisade mesophyll
densely packed region of cylindrical cells in upper section of leaf
what do palisade mesophyll contain lots of?
chloroplasts
spongy mesophyll
loosely packed layer of cells below palisade mesophyll
why do spongy mesophyll contai fewer chlorpolasts than palisade mesophyll?
space to allow diffusion of gases into palisade cell
xylem
vascular tissue for transport of water (and dissolved nutrients) from roots to rest of plants
phloem
vascular transport cells that collects sugars made in photosynthesis and transfers them to other parts of the plant
stomata
openings in the epidermis to allow for gases to enter and exit
guard cells
pair of cells placed on either side of the stoma that control whether it is open/closed
transpiration
the movement of water vapour out of plant cells via stomata
stomatal density
mean number of stomata per unit area of leaf surface
potometer
tool that measure water uptake of a plant to estimate rates of transpiration
order of structures (top to bottom) in a leaf cross section
cuticle
epidermal cells
palisade mesophyll
spongy mesophyll/vascular bundle
epidermal cells
cuticle
guard cells/stomata
list of adaptations of leaves for gas exchange
cuticle
epidermis
palisade mesophyll
spongy mesophyll
guard cells
xylem
phloem
why is the cuticle an adaptation of leaves for gas exchange
waterproof layer over leaves to present excessive transpiration
why is the epidermis an adaptation of leaves for gas exchange
secretes layer of cuticle that is thin enough to allow light through
why is the palisade mesophyll an adaptation of leaves for gas exchange
lots of chloroplasts to increase photosynthesis rates, proximity to sunlight
why is the spongy mesophyll an adaptation of leaves for gas exchange
photosynthesis can occur due to chloroplasts
gaps between cells allow gases to diffuse
why is the guard cell an adaptation of leaves for gas exchange
open stomata for gas exchange, close for decreased transpiration
why is the xylem an adaptation of leaves for gas exchange
deliver h20 for photosynthesis
why is the phloem an adaptation of leaves for gas exchange
transport glucose
what is needed for stomata to be open
turgid guard cells (water supply) AND daytime. both are required to stimulate the opening of guard cells
what makes a guard cell turgid
full vacuole
what happens when stoma are open
photosynthesis occurs
transpiration occurs
when does stomata close
when there is either no water supply (flaccid guard cells) or no light
what happens when stoma are closed
no photosynthesis, no transpiration
is the signalling of guard cells to open/close due to light independent of water availability
yes, behaviour of stoma in relation to light is a part of daily signalling. whether there is water or not is simply a protective mechanism
environmental factors that can impact transpiration
light
temperature
wind
humidity
how does increase light impact transpiration
increases it, as it stimulates guard cells to open for carbon dioxide for photosynthesis
how does increased temperature impact transpiration
increases it, as increased temperature increases the kinetic energy of water molecules, leading to increased evaporation of water molecules -> water leaves plant to go to the environmetn
how does increased wind affect transpiration
increased it, as it moves released water away from stomata, which maintain low water potential of air and thus, maintain concentration gradient needed for transpiration
how does increased humidity affect transpiration
decreases it, as humidity increases the water potential of the air and thus decreases the concentration gradient between the atmosphere and leaf
what are arterioles
vessels that connect large arteries to capillaries AND move blood away from the heart
capillary beds
network of capillaries that receive blood from same ateriole
what are capillaries
thin blood vessels that cover all tissues from which gas exchange occurs
venules
smallest of all veins, capillaries from same capillary bed drain their deoxygnated blood into
fenestrations
small slits/openings that can allow tissue fluid to enter/exit capillaries
coronary arteries
large arteries that branch off the aorta to deliver oxygen-rich blood directly from the lungs to the heart muscle
occlusion
layer of plaque inside the lumen that impairs blood flow
why are some tissues highly vascularised
have higher oxygen needs -> need more capillary beds to support these needs
what is a pulse rate
how many times your heart beats per minute
what medical complications occur due to occlusion of coronary arteries
coronary heart disease
heart attack
interaction between blood vessels
artery delivers blood from the heart to the ateriole, to the capillary bed, to the venule to the vein. the vein then returns the blood to the heart
why is blood drawn from veins not arteries
thinner walls
lower pressure, so if less blood will be lost if it is damaged
veins are usually on top of arteries
what challenges do arteries need to overcome
high pressure
structure of artery
tunica externa
tunica median
tunia interna
lumen
what is the size of the lumen in the artery
thin
what is the tunica media made up of
smooth muscle
collagen
elastic fibres
adaptations of arteries to withstand high pressure
smooth muscle
elastic fibres
thick tunica media
how is smooth muscle an adaptation of the artery to withstand high pressure
expand with pressure and relax in between -> regulates lumen and stops it being solid
how is the elastic fibres an adaptation of teh artery to withstand high pressure
contract/expand in response to pressure
able to release potential energy to force blood forward
what is the challenge capillaries need to overcome
fast diffusion
adaptations of capillaries to allow for fast diffusion
one-cell across width AND small diameter to allow for a high surface area to volume ratio
fenestration allow for greater permeability of nutrients and hormones
basement membrane to prevent loss of plasma, red blood cells, etc. into body cells
structure of capillaries
basement membrane
one-cell thick tissue with fenestrations
one RBC thick
contains plasma and nutrients e.g. glucose
what do fenestrations provide
extra permeability and allows tissue fluid to escape
what is the challenge faced by veins
preventing backflow
how are veins adapted to prevent backflow
they have valves, which only allow forward movement
structure of veins
relatively thin tunica externa/media/interna
wide lumen (allows blood to accumulate)
valves
some degree of elasticity to allow for force
what are the two places you can measure pulse rate from
radial artery -> neck
carotid artery -> wrist
benefits of measuring pulse rate at carotid artery
closer to heart -> stronger pressure
negatives of measuring pulse rate at carotid artery
highly depend on position
benefits of measuring pulse rate at radial artery
accessible
thin skin
limited muslce and fat
negatives of measuring pulse rate at radial artery
not as much pressure
what are the causes of occluded coronary areas
plaque builds up over time. the high pressure of the coronary arteries disrupt the plaque, which can rupture due to high pressure. this is worsened by hypertension.
body attempts to form clot at the site of the rupture. this leads to an occlusion
symptoms of an occlusion
angina (pain) because heart cant get enough oxygen
what happens if occlusion of coronary arteries is partial
coronary heart disease -> cant get enough oxygen
what happens if occlusion of coronary arties is complete
heart attack, as blockage cannot get to heart
tissue fluid
fluid individual cells bathe in
what does tissue fluid allow for?
easier material exchange
pressure filtration
pushing out of fluid from blood plasma (creating tissue fluid) caused by gaps between cells of the capillary walls
lymphatic capillaries
thin-walled vessels with gaps between cells to allow for extra fluid uptake and prevent build-up of fluids around body tissues
pulmonary circulation
discrete set of vessels (i.e. pulmonary artery and pulmonary vein) specifically for the transport of blood from heart to lungs
systemic circulation
discrete set of vessels for the transfer of blood to and from organs and heart
septum
thick wall of muscular and fibruous tissue that separates sides of the heart
how are substances exchanged between tissue fluid and cells
when tissue fluid is sequeezed out of arterioles, it contains a variety of essential nutrients (e.g. glucose). Active or passive transport into cells
how are lymph vessels similar to veins
both have very thin walls and valves to ensure one-way flow
differences between atria and ventricle structure
atria = thinner, muscular walls / only pump to ventricles / receive blood
ventricles = thicker / pump out of heart / receive blood from atria
what do atrioventricular valves prevent?
backflow of blood into atria
what do semilunar valves prevent?
backflow of blood into ventricles
How does tissue fluid become tissue fluid?
As plasma moves from the ateriole to the capillaries the pressure change (i.e. big tube moving to the small tube), the plasma is pushed out of the capillary fenestrations.
Where does tissue fluid get reabsorbed?
Partially into venule, as the bigger tube has lower pressure which allows some tissue fluid to be reabsorbed. However, the majority is absorbed into lymph capillaries, as this allows for slow diffusion of tissue fluid
how does tissue fluid go out of lymph vessels?
FIlter into lymph node. Once the lymph node has filtered for pathogens, it returns the fluid to the veins.
what does tissue fluid do
allow for the diffusion of substances between substances adn tissue cells
what does single/double circulatory system refer to?
how many times blood goes through the heart to reach the body
example of creature with a single circulatory system?
fish
how does a single circulatory system occur in a fish?
deoxygenated blood arrives from body tissue (into atria-equivalent). ventricle-equivalent then pumps this deoxygenated blood to the gills. the blood becomes reoxygenated, and travels to the body tissue.
negative of having a single circulatory system
low blood pressure when travelling from gills to body tissue
what is the benefit of having a double circulatory system?
passes through heart twice, so blood has high pressure when it is reaching
what type of heart is in a double circulatory system
4-chambered
what are the two names of circuits in the circulatory system in humans?
pulmonary circuit
systemic circuit
what is the flow of blood through the heart
vena cava
right atrium
tricupsid valve
right ventricle
pulmonary valve
pulmonary artery
LUNGS
pulmonary vein
left atrium
mitral valve
left ventricle
aortic valve
aorta
BODY
what is the role of the septum
prevent mixing of blood
what makes up the heart
cardiac muscle
only artery to carry deoxygenated blood
pulmonary artery
only vein to carry oxygenated blood
pulmonary vein
what attaches ventricles to cardiac muscle in heart
tendons
cardiac cycle
series of events commonly referred to as one heartbeat
sinoatrial node
area of modified cardiac muscle in the right atrium that can generate a spontaneous electrical heartbeat
atrioventricular node
receives action potential from sinoatrial node + fires electrical signals throughout both ventricles
systole
movement of blood due to heart muscle contraction
diastole
when heart muscle does not contract and is relaxed
electrocardiogram
graph that plots the electrical activity of sionatrial and atrioventricular nodes
how many steps are there in the cardiac cycle
5
first step of the cardiac cycle
sinoatrial node independently fires action potentials to walls of atria and atriaventricular node. atrioventricular valves are open, semilunar valves closed
second step of cardiac cycle
atrial systole: atria contract and send all blood into ventricles. atrioventricular valves open, semilunar valves closed
third step of cardiac cycle
atrioventricular node fires to ventricles. semi lunar valve open.
fourth step of cardiac cycle
ventricular systole -> contraction of ventricles. AV valves are shut and SL valves open
fifth step of cardiac cycle
diastole. muscle relaxes and heart refills. AV valves are open and SL valves shut
different phases of electrocardiograms
PQRST
P of electrocardiogram
atrial systole
QRS of electrocardiogram
ventricular systole
T of electrocardiogram
diastole
cohesion-tension theory
the upwards movement of water through the xylem by capillary action is due to transpiration pull and tension
capillary action
tendency for water to move upwards against gravity when in a thin tube
lignin
special polymer that are inside thick vessel wall of xylem
vascular bundle
cluster of vessels -> xylem and phloem
cortex
thick layer of unspecialised tissue between epidermis and vascular bundle in the stem and roots of plants
