3.2 Transport in animals Flashcards
factors influencing need for transport system
size
SA: V ratio
level of metabolic activity
why size affects need for transport system
multicellular organisms have multiple layers of cell
diffusion too slow for innermost layers (greater distance)
outer layer of cells use up supplies so less reach deeper cells
how SA:V affects need for transport system
larger animals have smaller SA:V ratio so diffusion is insufficient to meet each cell’s demands
how level of metabolic activity affects need for transport system
cells need to respire aerobically more if organism needs to move around
cells need good supply of nutrients and oxygen to supply energy
animals that need to keep warm need to respire more
features of good transport system
fluid / medium to carry nutrients, oxygen and wastes around body (blood)
pump to create pressure to push fluid around body (heart)
exchange surfaces that enables substances to enter and leave blood freely (capillaries)
tubes to carry blood by mass flow
two circuits (one picks up oxygen and other to deliver oxygen to tissues)
single circulatory system
blood flows through heart once for each circuit e.g. fish
heart -> gills -> body -> heart
double circulatory system
blood flows through heart twice for each circuit of body
two separate circuits
pulmonary circulation (carries blood to lungs to pick up oxygen)
systemic circulation (carries oxygen and nutrients around body to tissues)
heart -> body -> heart -> lungs -> heart
disadvantages of single circulatory system
blood has low pressure as so flows not very quickly
limited rate of oxygen and nutrient exchange and waste removal
advantages of double circulatory system
blood pressure in pulmonary circulation must be low so capillaries aren’t damaged
heart can increases pressure of blood in systemic circulation so it flows more quickly
oxygen and nutrient exchange and waste removal in rest of body is hastened
artery definition
vessel that carries blood away from heart
arteriole
small blood vessel that distributed blood from artery to capillaries
capillary
very small vessels with very thin walls
closed circulatory system definition
one in which blood is held in vessels
open circulatory system
one in which blood is not held in vessels
vein
vessel that carries blood back to heart
venule definition
small blood vessels that collect blood from capillaries and lead into veins
how open circulatory systems work
blood fluid circulates through body cavity, tissues and cells bathed directly in blood
long muscular pumping organ located under dorsal (upper) surface of body
blood enters organ through pores (ostia)
heart pumps blood towards head by peristalsis
blood pours out into body at forward end of head
body movements affect circulation
bigger insects have open-ended tube attached to heart that lead to active parts of body
Disadvantages of open circulatory systems
blood pressure and flow is slow
may be affected by body movements (or lack of)
how closed circulatory system
blood stays in vessels separate fluid (tissue fluid) bathes tissues and cells
advantages of closed circulatory system
higher pressure so blood flows more quickly
more rapid delivery and removal of oxygen, nutrients and waste products
transport independent to body movements
endothelium function
thin inner lining of vessels
single layer to reduce diffusion distance
smooth to reduce friction with flowing blood
artery function and structure
carries blood away from heart
from outside
outer, thick layer of collagen withstand and maintain high pressure
middle, thick layer of smooth muscle
inner, thin layer of elastic tissue, allows wall to stretch and recoil (helps maintain blood pressure)
endothelium
narrower lumen than vein
vein function and structure
carries blood back to heart
from outside
collagen fibres, smooth muscle, elastic fibres, endothelium
wider lumen than artery (ease blood flow)
valves (prevent back-flow of blood, helps blood move in right direction when skeletal muscles contract)
thinner walls (don’t need to stretch and recoil, not actively constructed as to reduce blood flow)
capillary structure
from outside
very thin walls (endothelium) (reduces diffusion distance)
very narrow lumen (squeezes RBCs against walls, reduces diffusion distance, increases resistance and rate of flow)
leaky (allows blood plasma and dissolved substances to leave blood)
arteriole function and structure
distribute blood from artery to capillaries
smooth walls contain smooth muscle (contracts to constrict diameter of arteriole, reduces rate of blood flow by increasing resistance)
constriction of arteriole walls can direct flow of blood to more demanding regions
venule function and structure
collect blood from capillary bed and lead into veins from outside endothelium thin wall (thin layers of smooth muscle, elastic tissue and collagen)
hydrostatic pressure definition
pressure exerted by fluid when pushing against sides of vessel or container
lymph definition
fluid held by lymphatic system (which to system of tubes that returns excess tissue fluid in blood system)
similar to tissue fluid but contains more lymphocytes
oncotic pressure definition
pressure created by osmotic effects of large proteins (albumin)
plasma definition and what it contains
fluid portion of blood contains dissolved substances such as: oxygen carbon dioxide minerals glucose amino acids hormones plasma proteins
tissue fluid definition
fluid surrounding cells and tissues
similar to plasma but doesn’t contain most cells in blood and plasma proteins
blood composition
plasma
erythrocytes (red blood cells)
leukocytes (white blood cells)
platelets
how tissue fluid is formed
artery reaches tissues branches -> smaller arterioles-> network of capillaries -> venules-> veins
at arterial end of capillary, blood at high hydrostatic pressure
oncotic pressure higher in tissue fluid than in capillary
net pressure tends to push blood fluid out of capillaries through tiny gaps between cells in capillary wall
tissue fluid
all RBCs, most WBCs and plasma proteins stay in capillaries as too big to be pass through capillary wall
tissue fluid bathes body cells so exchange of gases and nutrients can occur across plasma membrane (via diffusion, facilitated diffusion and active transport)
how tissue fluid returns to blood
hydrostatic pressure in tissue fluid at venous end of capillary lower than within capillary
oncotic pressure in tissue fluid much higher than in capillary
net flow of fluid into capillary
some tissue fluid moves down oncotic pressure gradient and returns to capillary (carrying waste substances into blood)
some tissue fluid directed into lymphatic system
drains excess tissue fluid out of tissues and returns it to blood system in subclavian vein in chest
lymph contains more lymphocytes, produced at lymph nodes
lymph node definition
swellings found along lymphatic system
produces lymphocytes
has important role in immune response
movement of fluids in capillaries
hydrostatic pressure of blood pushes fluid out into tissues
hydrostatic pressure of tissue fluid tends to push fluid into capillaries
oncotic pressure of blood tends to pull water back into blood (has negative figure)
oncotic pressure of tissue fluid pulls water into capillary
net result of forces creates pressure to push fluid out of capillary at arterial end and into capillary at venule end
cardiac muscle definition
specialised muscle found in walls of heart chambers
bicuspid valve definition
valves found between left atrium and ventricle
ensure blood flows in correct direction
tricuspid valve definition
valve between right atrium and ventricle
ensure blood flows in correct direction
semilunar valves definition
valves in major arteries that prevent blood from re-entering heart
external features of heart
4 pumping chambers (2 thinner-walled atria and 2 thicker p-walled ventricles) made of cardiac muscle
bottom of heart comes to a point (apex)
coronary arteries over surface of heart (supplies cardiac muscle with oxygenated blood)
if coronary artery blocked, blood flow to heart muscle restricted so delivery of oxygen and glucose redirected (can cause myocardial infarction aka heart attack)
top of heart are tubular veins (blood into atria) and arteries (blood away from heart)
internal features of heart
heart divided into 4 chambers (left and right atria and ventricles)
vena cava (deoxygenated blood, from body, to right atrium)
pulmonary artery (deoxygenated blood, from right ventricle, to lungs)
pulmonary vein (oxygenated blood, from lungs, to left atrium)
aorta (oxygenated blood, from left ventricle, to body)
bicuspid / tricuspid valves (atrioventricular valves attached to tendinous cords between atrium and ventricles)
tendinous cords (prevents valves from turning inside out when ventricles contract)
septum (wall of muscle that separates ventricles and prevents oxygenated and deoxygenated blood separate)
blood pressure in atria
muscle of walls very thin
don’t need to create much pressure as only needs to push it to ventricles
blood pressure in right ventricle
walls thicker than atria’s (blood pumped out of heart)
lungs close to heart (doesn’t need to travel much further)
alveoli in lungs delicate (could be damaged by very high blood pressure so blood must be at low pressure)
blood pressure in left ventricle
can be 2-3x thicker than right ventricle
pressure of blood needs to overcome resistance of systemic circulation
cardiac muscle composition
fibres - branch producing cross-bridges (helps spread stimulus around heart
also ensures muscle produces squeezing action (instead of just a reduction in length)
lots of mitochondria between muscle fibrils (myofibrils)
muscle cells separated by intercalated discs (facilitates synchronised contraction)
each cell divided into sarcomeres
diastole method
after systole, ventricular walls relax and recoil
pressure in ventricles drops below atria’s
blood in atria pushes AV valves open and enter ventricles
blood volume in atria and ventricles rise
blood pressure in atria and ventricles slowly rise
atrial systole method
after diastole, both atria contract
further pressure increase in atria
blood flows through AV valve to ventricles
blood volume increase in ventricles
ventricular systole method
when ventricles full, ventricles contract (from apex upwards)
pressure in ventricles rises above pressure in atria
AV valves shut, semilunar valves still shut as greater pressure in major arteries than ventricles
pressure rises quickly as blood can’t escape
pressure in ventricles rises above major arteries’
semilunar valves open and blood pumped out
volume and pressure drops quickly in ventricles
pressure decreases below pressure in semilunar valves so they close (slows back flow of blood into ventricles)
heartbeat sounds
1st lub-dub= AV shutting
2nd lub-dub = SL valves shutting
blood pressure in vessels
tissues require an even blood flow
artery walls contains a lot of elastic tissue
walls stretch as blood leaves heart
pressure in aorta drops as blood moves out of it
walls recoil to maintain blood pressure in aorta
fluctuations become less obvious as blood flows along arteries (pressure drops more)
important to maintain pressure gradient between aorta and arterioles (keeps blood flowing towards tissues)
myogenic definition
can initiate its own contraction
fibrillation definition
unsynchronised contraction of atria and ventricles
SAN-AVN method
SAN (sinoatrial node) initiates wave of excitement (WOE)
and reach atrial walls (atria contract / atrial systole simultaneously)
band of fibres between atria and ventricles stop WOE passing directly into ventricular walls
WOE reaches AVN (delays it for 0.1s so atrial systole can complete before ventricular systole starts)
WOE spreads down septum to bundle of His then Purkyne fibres
ventricles contract simultaneously from apex upwards to pump blood upwards (emptied ventricles)
ECG stands for
electrocardiogram
ECG parts meaning
wave P = excitation of atria
QRS complex = excitation of ventricles
T = diastole
sinus rhythm meaning
normal rhythm
bradycardia definition
slow heart rate
tachycardia definition
fast heart rate
ectopic heart beating definition
ventricular heart beat too early
patient often feels heartbeat has been missed
atrial fibrillation meaning
atria beating more frequently than ventricles
no clear P waves
affinity definition
a strong attraction
dissociation definition
when a molecule splits up to make 2 molecules
haemoglobin structure
4 subunits (2 alpha chains, 2 beta chains)
each subunit is polypeptide chains with prosthetic (non-amino acid) haem group
haem group contains Fe2+ (attracts and holds 1 oxygen molecule / 2 oxygen atoms)
partial pressure definition
amount of pressure exerted by a gas relative to total pressure exerted by all gases in mixture
measured in kPa
represented e.g. pO2 (oxygen tension)
factor of haemoglobin’s affinity to oxygen
oxygen tension (partial pressure of oxygen)
oxygen dissociation curve at low oxygen tension
low oxygen tension = low O2 percentage saturation in haem.
haem. doesn’t readily associate as haem groups at centre of haem. (difficult for O2 to associate with it)
oxygen dissociation curve as oxygen tension rises
rising oxygen tension = rising steeply O2 percentage saturation in haem.
steeper diffusion gradient to haem.
one O2 associates with a haem group
change shape of haem. (conformational change)
allows more O2 to enter haem. and associate with other groups more easily
oxygen dissociation curve at high oxygen tension
in lungs
close to 100% saturation
curve levels off, creating S-shaped curve
hard for 4th O2 to diffuse and associate with to reach 100%
oxygen tension at respiring cells
low
enough to cause oxygen to dissociate from oxyhaemoglobin
foetal haemoglobin vs adult haemoglobin
higher affinity than adult haemoglobin
has to associate with oxygen where oxygen dissociates with adult haemoglobin
how carbon dioxide is transported
5% dissolved directly into plasma
10% carbaminohaemoglobin
85% hydrogen carbonate ions
formation of hydrogen carbonate ions
carbon dioxide diffuses into RBCs
combines with water to form carbonic acid (using carbonic anhydrase enzyme)
carbonic acid dissociates into H+ + HCO3-
hydrogen carbonate ions diffuse out of RBCs
charge maintained in RBC by movement of chloride ions (chloride shift)
hydrogen ions taken out of solution by associating with haemoglobin (forming haemoglobonic acid) to maintain constant pH
haemoglobin acts as buffer
Bohr effect
presence of hydrogen ions affects pH of cytoplasm in RBC
affects tertiary structure of haemoglobin (reduces affinity for oxygen)
oxygen dissociates from oxyhaemoglobin
Bohr shift
more carbon dioxide produced in respiring tissue
more hydrogen ions in. RBCs
more oxygen dissociated with oxyhaemoglobin
oxygen dissociation curve shift downwards and to the right (Bohr shift)
myoglobin function
molecule found in muscle cells
only dissociates with oxygen at very low partial pressures
fenestrated meaning
“windowed”
regions of gaps
