Transport In Animals Flashcards
1
Q
Why ‘Specialised Transport Systems’ are needed in multicellular organisms?
A
- hormones & enzymes need to be transported from one place to another
- products of food digestion needs to be transported to every cell for respiration
- waste products need to be removed and transported to excretory organs
2
Q
Common Circulatory System features
A
- liquid transport medium that circulates around the body e.g. blood
- vessels to carry the transport medium
- pumping mechanism that moves the fluid around the system
3
Q
Open Circulatory System
A
- found in invertebrates e.g insects
- contains very few vessels
- transport medium = ‘haemolymph’
- ^ this is pumped straight from the heart into the body cavity
- open body cavity = ‘haemocoel’
- ^ it’s split by a membrane
- the heart extends along the length of the thorax and abdomen of insect
4
Q
Haemolymph
A
- moves at a low pressure
- comes into direct contact with tissues
- doesn’t carry oxygen or carbon dioxide
- transports food, nitrogenous waste products & immunity cells
- haemolyph vol. cannot be controlled to meet changing demands of tissues
5
Q
Closed Circulatory System
A
- blood is enclosed in vessels so it doesn’t come into direct contact with cells
- heart pumps blood around body under pressure (relatively fast process)
- substances leave and enter the bloodstream by diffusion through the walls of blood vessels
- blood flow can be controlled by vasodilation & vasoconstriction
- most systems contain a blood pigment that carries the respiratory gases
6
Q
Single Closed Circulatory System (FISH)
A
- Deoxygenated blood pumps from the heart at high pressure and travels to gills through respiratory capillaries
- Oxygen diffuses into bloodstream
- Oxygenated blood now travels at low pressure to the body tissues through systemic capillaries
- Oxygen diffuses into body tissues
- Deoxygenated blood travels back to heart at low pressure
7
Q
Single Closed Circulatory System (FISH) 2
A
- the low pressure of blood limits efficiency of exchange process
- ^ therefore, limiting organisms’ activity
- fish don’t maintain their body temperature or weight in water
- ^ metabolic demands are reduced so they can be active with a single c. system
8
Q
Double Circulatory System
A
1st loop:
1. Deoxygenated blood is pumped from heart to lungs to pick up oxygen & unload carbon dioxide
2. The now oxygenated blood returns to the heart to be pumped around body
2nd loop:
3. Oxygenated blood is pumped around the body provide oxygen to cells for aerobic respiration
4. The now deoxygenated blood moves from body cells back to heart
5. The deoxygenated blood in the heart is pumped again to lungs to gain oxygen
(Cycle repeats itself)
9
Q
Blood Vessels
A
- collagen outer layer strengthens walls against high blood pressure
- smooth muscle layer contracts and relaxes to change diameter of lumen to control blood flow to different organs
- elastic layer allows vessels to stretch and recoil without bursting (elastic recoil)
- lumen lined with thin layer of endothelium cells prevents friction
10
Q
Arteries
A
- carry oxygenated blood away from heart to tissues except ‘pulmonary artery’
- ^ pulmonary artery carries deoxygenated blood from heart to lungs
- umbilical artery carries deoxygenated blood from fetus to placenta
- blood is under relatively high pressure
- the ‘aorta’ is the biggest artery with the least smooth muscle
11
Q
Arterioles
A
- link arteries to capillaries
- contain more smooth muscle in walls (for vasoconstriction/vasodilation) & less elastin
- have a little pulse surge
12
Q
Capillaries
A
- link arterioles to venules
- form an extensive network through the tissues of the body
- walls are one cell thick
- lumen is so small that red blood cells can only pass in a single file
- cross-sectional area is bigger than the arteriole’s so blood pressure falls
- ^ this provides more time for exchange
13
Q
Veins
A
- carry deoxygenated blood from tissues to heart except ‘pulmonary vein’
- ^ pulmonary vein carries oxygenated blood from lungs to heart
- umbilical vein carries oxygenated blood from placenta to fetus
- blood is under relatively low pressure
- the superior & inferior ‘vena cava’ are the biggest veins with the most collagen
14
Q
Venules
A
- venules link capillaries to veins
- do not contain a smooth muscle or elastin layer
- have no pulse surge
15
Q
Vein Adaptations
A
- Medium sized veins have one way valves to prevent blood back-flow
- Bigger veins run between active muscles of body e.g. arms & legs
^ when they contract, it forces the blood towards the heart - Breathing movements create pressure changes and squeezing actions
^ this also moves blood in the chest & abdomen veins toward the heart
16
Q
Blood
A
- maintains body temperature & acts as a buffer to minimise pH changes
45% - ‘erythrocytes’ = red blood cells
- ‘leukocytes’ = white blood cells
- platelets = cell fragments found in bone marrow that’s involved in blood clotting
55% - plasma = yellow liquid
- ^ carries dissolved sugars, amino acids, mineral ions, hormones & large plasma proteins
17
Q
Erythrocyte adaptations
A
- biconcave shape to provide a larger SA
- no nucleus to maximise amount of haemoglobin that can fit
- ^ however, this minimises their lifespan
18
Q
Tissue Fluid
A
- dissolved substances from plasma that pass through gaps in capillary walls
- ^ except large plasma proteins
- blood has a low water potential compared to surrounding fluid
- oncotic pressure = tendency of water to move into the blood by osmosis
- ^ remains the same throughout capillary
- hydrostatic pressure = tendency for fluid to be forced out of capillary
19
Q
Tissue Fluid (Arterial end)
A
Hydrostatic pressure is greater than oncotic pressure so…
1. “Plasma” leaves blood to become tissue fluid between body cells
2. Oxygen & glucose are transferred to the body cells from fluid
3. Waste products (inc. CO2) from body cells are transferred back to tissue fluid
20
Q
Tissue Fluid (Venous end)
A
Hydrostatic pressure is less than oncotic pressure so…
4. Fluid returns back to the bloodstream (around 90%)
5. Remaining 10% drains into ‘lymph capillaries’ of the lymphatic system
21
Q
Lymph
A
- contains similar components to plasma & tissue fluid
- ^ has less oxygen & nutrients but more fatty acids from villi in the small intestine
- transported through lymph vessels by the squeezing of body muscles
- ^ lymph vessels contain one-way valves
- returns to bloodstream via the subclavian veins
22
Q
Lymphatic System
A
- lymph nodes are located along the lymph vessels
- ^ they intercept bacteria so it can be ingested by the phagocytes in them
- ‘lymphocytes’ build up in lymph nodes when needed to produce antibodies
- enlarged lymph nodes are a sign the body is fighting off a pathogen
- major lymph nodes reside in the neck, armpit, stomach & groin
23
Q
Haemoglobin (Hb)
A
- a conjugated globular protein made of 4 polypeptide chains (2 αlpha & 2 βeta)
- contains haem prosthetic group ‘Fe2+’
- acts a red pigment in blood
- has a high affinity for oxygen
- each haemoglobin molecule can bind to four oxygen molecules
- oxygen binds loosely to Hb forming ‘oxyhaemoglobin’
- ^ reaction is reversible
24
Q
Haemoglobin 2
A
- oxygen from air in alveoli diffuses into erythrocyte & binds to a haem group
- ^ Hb molecule now changes shape - making it easier for the next oxygen molecule to bind
- ^ aka. ’positive cooperativity’
- a steep diffusion gradient is maintained until all of Hb is saturated with oxygen
- ^ vice versa for when oxygen needs to be removed from body cells
25
Q
Oxygen Dissociation Curve
A
- y axis = saturation of haemoglobin (%)
- 25% saturation is “equivalent” to one oxygen molecule bound to Hb
- x axis = partial pressure of oxygen (kPa)
- ^ partial pressure = measure of oxygen concentration in the air
- Hb has low affinity for oxygen at low partial pressures of oxygen
- a small change in kPa makes a big difference to Hb saturation %
26
Q
Oxygen Dissociation Curve 2
A
- 4th oxygen molecule binds to a haem group at a high partial pressure
- ^ due to majority of haem groups being filled - lowering the chances of another molecule being added (collision theory)
- it’s very unlikely for the final oxygen molecule to unload from haemoglobin
- ‘Bohr effect’ = Hb affinity for oxygen decreases as a result of partial pressure of carbon dioxide increasing
27
Q
Fetal Haemoglobin
A
- maternal blood (mb) has a higher level of oxygen than fetal blood (fb)
- ^ this causes oxygen in mb to diffuse across the placenta into fb
- 2 of the 4 polypeptide chains in fetal Hb are different to adult Hb
- fetal haemoglobin shifts the oxygen dissociation curve to the left
- ^ this causes its affinity for oxygen to slightly increase above adult Hb
28
Q
Fetal Haemoglobin 2
A
- the higher affinity of fetal Hb increases the oxygen transfer across the placenta
- carbon dioxide from fb diffuses into mb which reduces affinity of adult Hb
- ^ this also increases oxygen transfer because the adult Hb is more likely to dissociate with oxygen (give it away)
29
Q
Internal Carbon Dioxide
A
- ≈ 80% is converted into hydrogen carbonate ions (HCO₃-)
- ^ this is the form of carbon dioxide that’s transported to the lungs
- ≈ 15% is combined with amino groups in poly p. chains of haemoglobin
- ^ aka. carbaminohaemoglobin
- 5% is dissolved in plasma
30
Q
Internal Carbon Dioxide 2
A
- carbon dioxide shifts oxygen dissociation curve to the right
- ^ causing Hb affinity for O2 to decrease
- other forms of carbon dioxide ensure the level of it in the body cells is low
- ^ this creates a steep concentration gradient for gaseous exchange
31
Q
Chloride Shift
A
- Carbon dioxide from plasma diffuses into erythrocyte & reacts with water
- Carbonic anhydrase catalyses the reaction to produce carbonic acid
- Carbonic acid dissociates to form H+ & hydrogen carbonate ions
- Hydrogen carbonate ions diffuse out of erythrocyte into plasma
- Simultaneously, chloride ions diffuse into erythrocyte (chloride shift)
^ this maintains electrical balance of cell
32
Q
Chloride Shift 2
A
- H+ ions bind to Hb (to form ‘haemoglobinic acid’) as it dissociates from oxyhemoglobin
^ this prevents pH decrease in blood
^ this also causes the quaternary structure of Hb to change shape - The now separated oxygen molecules diffuse out of cell into plasma
^ the reverse reaction takes place when carbon dioxide level is low e.g. in the lungs
33
Q
Heart
A
- left side = oxygenated blood flow
- right side = deoxygenated blood flow
- made of cardiac muscle that does not get fatigued/needs to rest
- coronary arteries supply oxygenated blood to cardiac muscle
- inelastic pericardial membranes prevent it from over-distending with blood
- muscular wall on left ventricle is thicker than the right because oxygenated blood needs to be pumped under pressure to reach the whole body
34
Q
Blood Flow in Heart
Right side
A
- Deoxygenated blood enters right atrium from superior & inferior vena cava
- Pressure builds up inside until tricuspid valves are “forced open”
- Blood flows into the right ventricle
- Tricuspid valves close after right atrium contracts to prevent backflow
- Right ventricle contracts and blood passes through semilunar valves
- Tendinous cords ensure valves don’t turn inside out by pressure from ventricle contraction
- Blood reaches the pulmonary artery to be transported to lungs
35
Q
Blood Flow in Heart
Left side
A
- Oxygenated blood enters left atrium from pulmonary vein
- Pressure builds up inside until by bicuspid valves of forced open
- Blood flows into left ventricle
- Bicuspid valves close as left atrium contracts to prevent backflow
- Left ventricle contracts and pumps blood through semilunar valves
- Blood reaches the aorta to be transported to respiring cells in the body
36
Q
Cardiac Cycle
Diastole
A
- heart muscles are relaxed
- atrio-ventricular valves are slightly open
- blood begins to fill atria and passively trickles down into ventricles
- volume & pressure increases
37
Q
Cardiac Cycle
Atrial Systole
A
- Blood is filled in the atria
- Pressure in atria becomes higher than pressure in ventricles
- Atria contract so blood passes through the atrio-ventricular valves
38
Q
Cardiac Cycle
Ventricular Systole
A
- Blood fills ventricles
- Atria relax so pressure inside ventricles become higher
- Ventricles contract from apex upwards
- Blood is pushed up through semilunar valves to pulmonary artery/aorta
39
Q
Cardiac Output
A
- shows the volume of blood pumped into the circulatory system per min
- = heart rate x stroke volume
- stroke volume = vol. of blood pumped out during each ventricular contraction
- ^ usually 70 cm³
40
Q
Pressure Changes in the Heart
A
Aortic pressure
- rises when ventricles contract
- never falls below 12 kPa because of the elasticity in its walls
Atrial pressure
- always relatively low
- ^ due to thin walls of atria that cannot create much force
- increases as atria fill with blood
- ^ drops as soon as the AV valves open
41
Q
Pressure Changes in the Heart 2
A
Ventricular pressure
- increases dramatically as ventricles contract & AV valves close
- when higher than that of the aorta, blood is forced past the SL valves
- decreases dramatically as ventricles relax & SL valves close
Ventricular volume
- increases as ventricles fill with blood
- suddenly decreases as blood is forced into aorta past semilunar valves
42
Q
Heart Sounds
A
- made by blood pressure closing heart valves
- sounds are described as ‘lub-dub’
- ‘lub’ = blood forced against atrio-ventricular valves as ventricles contract
- ‘dub’ = backflow of blood closes semilunar valves as ventricles relax
43
Q
Heart Rhythms
A
- cardiac muscle is myogenic
- ^ it has its own intrinsic rhythm of around 60 bpm
- ^ this prevents the body from wasting resources to maintain a basic heart rate
- sino-atrial node = a wave of electrical excitation in the pacemaker area (wall of the right atrium)
- ^ causes the atria to contract which initiates a heartbeat
- ^ a layer of non-conducting tissue prevents excitation passing to ventricles
44
Q
Heart Rhythms 2
A
- atria-ventricular node = interprets electrical activity from SAN to impose a delay before stimulating ‘bundle of His’
- ^ the slight delay ensures atria have stopped contracting before allowing ventricles to contract
- bundle of His = bundle of conducting tissue made up of Purkyne fibres that penetrate through the septum
- ^ bundle splits into two branches & conducts a wave of excitation to the apex
- Purkyne fibres also spread throughout the walls of ventricles to trigger ventricular contraction from apex
45
Q
Electrocardiograms (ECG)
A
- an indirect recording of electrical activity in the heart
- ^ it directly measures tiny electrical differences in the skin resulted from the electrical activity in the heart
- uses electrodes stuck onto clean skin to pick up a signal
- used to help diagnose heart problems
46
Q
Types of Heart Rhythms
A
- tachycardia = evenly spaced heartbeats over 100 bpm
- bradycardia = evenly spaced heartbeats under 60 bpm
- ectopic heartbeat = extra heartbeats out of the normal rhythm
- ^ most humans experience at least one a day - becomes a problem when frequent
- atrial fibrillation = abnormal irregular rhythm from atria produced by rapid electrical impulses
