Module 3.2 - Transport in Animals Flashcards
What factors affect the need for a transport system?
- Size
- SA:vol ratio
- Level of metabolic activity
How does size affect the need for a transport system?
- Cells further from surface, diffusion pathway increases
- Diffusion rate reduced + diffusion too slow to supply all requirements
- Outer layers of cells use up all supplies so less would reach cells deep in body
How does surface area to volume ratio affect the need for a transport system?
-Larger organisms have larger SA:vol ratio so each g of SA has smaller body surface for exchange
How does level of metabolic activity affect the need for a transport system?
- Animals get energy from food for movement
- Releasing energy from food by aerobic respiration requires oxygen
- In animal is active, cells need good supplies of nutrients to supply energy for movement
- Animals that keep themselves warm need even more energy
What are the features of a good transport system?
-Fluid/medium to carry nutrients, oxygen + wastes around body (blood)
-Pump to create pressure to push fluid around body (heart)
-Exchange surfaces that enable substances to enter blood + leave again where needed (capillaries)
For efficiency:
> Tubes/vessels to carry blood by mass flow
> 2 circuits: one to pick up oxygen (pulmonary) + one to deliver oxygen to respiring tissues (systemic)
What is the route of blood through a single circulatory system (e.g. fish)?
heart –> gills –> body –> heart
What is the route of blood through a double circulatory circuit (e.g. mammals)?
heart –> body –> heart –> lungs –> heart
What are the disadvantages of a single circulatory system?
- Blood pressure drops as blood passes through tiny capillaries of gills
- Blood has low pressure as it flows towards body - won’t flow very quickly
- Rate at which O2 + nutrients delivered to respiring tissues + CO2 + urea is removed is limited
What are the advantages of a double circulatory system in mammals?
- Blood pressure mustn’t be too high in pulmonary circulation as may damage lung capillaries
- Heart can increase pressure of blood after passing through lungs, so blood is under higher pressure as it flows to body + flows more quickly
- Systemic circulation can carry blood at higher pressure than pulmonary circulation
Give an example of an animal with an open circulatory system.
Insects
How do substances get around animals with open circulatory systems?
- Movement helps to circulate blood, when stationary blood stops moving so transport stops
- Insects: muscular pumping organ similar to heart just under dorsal of body. Blood enters heart through pores (ostia) which pumps towards head by peristalsis. At front end of heart blood pours into body cavity. Can continue at rest but movement may affect circulation
- Larger insects (e.g. locusts): -Open ended tubes attached to heart. Direct blood towards active parts of body e.g. leg + wing muscles
What are the disadvantages of an open circulatory system?
- Blood pressure low + blood flow is slow
- Circulation of blood may be affected by body movements or lack of
What are the advantages of a closed circulatory system with tissue fluid to supply cells with the necessary substances?
- Higher pressure so blood flows quicker
- More rapid delivery of oxygen + nutrients
- More rapid removal of CO2 + other wastes
- Transport is independent of body movements
What is the blood in the arteries like?
-High pressure so arterial wall has to be thick
Describe the structure of arteries.
-Narrow lumen to maintain high pressure
-Thick wall to withstand high pressure. 3 layers:
> Inner layer: thing layer of elastic tissue allowing stretch + recoil to help maintain blood pressure
> Middle layer: thick layer of smooth muscle
> Outer layer: relatively thick layer of collagen + elastic tissue, providing strength to withstand high pressure + recoil to maintain pressure
Where are arterioles found?
Between arteries and capillaries - distribute blood from the artery to the capillary
Describe the structure of arterioles.
- Arteriole walls contain smooth muscle that contracts to constrict diameter of arteriole to increase resistance to decrease rate of flow of blood
- Constriction of arteriole wall can be used to divert flow of blood to regions of body demanding more oxygen
Describe the structure of capillaries.
- Very narrow lumen: diameter about same as RBC (7μm) so RBCs squeezed against walls of capillary as they pass along it, reducing diffusion path of oxygen to tissues. Also increases resistance so reduces rate of flow
- Walls consist of a single layer of flattened endothelial cells reducing diffusion distance for materials being exchanged
- Walls are leaky allowing blood plasma + dissolved substances to leave the blood
Where are venules found?
Between capillaries and veins - collect blood from capillary bed + lead into veins
Describe the structure of venules.
- Wall consists of a think layer of muscle + elastic tissue outside endothelium
- Thin outer layer of collagen
Describe the structure of veins.
- Relatively large lumen to decrease resistance to ease flow of blood
- Walls; thinner layers of collage, smooth muscle + elastic tissue than artery walls. Don’t need to stretch + recoil + are not actively constricted to reduce blood flow
- Valves: help blood flow back to heart + prevent it flowing in opposite direction
- Walls are thin so vein can be flattened by action of surrounding skeletal muscle. Contraction of surrounding skeletal muscle applies pressure to blood forcing blood to move along in a direction determined by valves
How does tissue fluid form?
- At arteriole end of capillaries blood is under high hydrostatic pressure due to heart’s contractions
- This pressure pushes blood fluid (plasma) out of capillaries through gaps between cells of capillary wall. This happens as the hydrostatic pressure is higher than the oncotic pressure
- Plasma + dissolved substances leave the blood
- RBCs, platelets + most WBCs are too large to leave so stay in capillary
- Tissue fluid surrounds cells for exchange to occur
How is tissue fluid drained?
- Some returns to capillaries: low hydrostatic pressure at venule end + oncotic pressure now high due to plasma proteins in the blood, fluid moves back into blood carrying dissolved wastes down a pressure gradient
- Rest leaves through lymphatic system
How does fluid from tissue fluid reenter the blood through the lymphatic system?
- Pores allow fluid to leave tissue fluid + enter lymph vessels
- Removes large proteins + neutrophils from tissue fluid to reenter blood
- Lymph vessels drain lymph into large vessels which eventually rejoin blood system in the chest (via subclavian vein)
What is the fluid in the lymphatic system called?
Lymph
Where are the lymphocytes present in lymph produced?
Lymph nodes
What is the role of lymph nodes?
- Swellings found at intervals along lymphatic system
- Have an important role in immune system
- Produce lymphocytes
What is hydrostatic pressure and what does it do?
- HS pressure of blood: tends to push fluid into tissues
- HS pressure of tissue fluid: tends to push fluid into capillaries
- Force a liquid exerts on the walls of its containers
What is oncotic (osmotic) pressure and what does it do?
- Oncotic pressure of blood: tends to pull water back into blood (has negative figure)
- Oncotic pressure of tissue fluid: pulls water into tissue fluid
- Oncotic pressure of solutes dissolved in solution have an influence on hydrostatic pressure
What is the muscle of the heart called?
Cardiac muscle
Which blood vessel supplies the cardiac muscle of the heart with oxygen and glucose for aerobic respiration?
Coronary artery
What happens if there is blockages in the coronary arteries?
- Restricted delivery of oxygen + glucose)
- Angina or myocardial infarction
What is attached to the valves and what do they do?
- Tendinous cords
- Prevent valves from turning inside out when ventricle walls contract
What is the role of the ventricular septum?
-Ensures the oxygenated blood left side + deoxygenated blood on right side are kept separate
Which blood vessel does deoxygenated blood leave the heart through?
pulmonary artery
Which blood vessel does deoxygenated blood enter the heart through?
vena cava
Which blood vessel does oxygenated blood enter the heat through?
pulmonary vein
Which blood vessel does oxygenated blood leave the heart through?
aorta
What is the width of the atria walls and why?
- Muscle of atria walls is very thin
- Don’t need to create much pressure (only enough to get through AV valves in ventricles)
- Function is to receive blood from veins and push into ventricles
What is the width of the right ventricular walls and why?
- Thicker than walls of atria
- Enables right ventricle to pump blood out of heart
- Pumps deoxygenated blood to lungs
- Lungs are in chest cavity beside the heart, so blood doesn’t need to travel far
- Can’t have too high a pressure as alveoli are delicate + could be damaged by high pressure
- Only needs to create enough pressure to overcome the resistance of the pulmonary circuit
What is the width of the left ventricular walls and why?
- Can be 2 or 3 times thicker than right ventricular walls
- Blood from left ventricle pumped out through aorta
- Left ventricle needs to create enough pressure to overcome the resistance of the systemic circulation
- Has to be pumped all around the body which is further than the lungs for the right ventricle
What is the structure of the cardiac muscle?
- Consists of fibres that branch to produce cross-bridges
- Help to spread stimulus around heart + ensure muscle can produce squeezing action rather than just a reduction in length
- Number of mitochondria between muscle fibrils (myofibrils) to supply energy for contraction
- Muscle cells separated by intercalated discs which facilitate synchronised contraction
- Each cell has a nucleus + is divided into contractile units: sarcomeres
- Is myogenic
The cardiac muscle of the heart is myogenic. What does this mean?
It initiates its own contractions
What is the cardiac cycle?
The sequence of events in one full heartbeat
What is the role of valves?
- Ensure blood is flowing in the correct direction
- Open + close by changes in blood pressure
Describe the movement of blood through the heart in relation to the atrio-ventricular valves (from diastole to ventricular systole).
- Pressure in ventricles rapidly drops below pressure of atria
- Blood in atria pushes AV valves open
- Blood entering heart flows straight through atria + into ventricles
- Pressure in atria + ventricles rises slowly as they fill w blood
- Valves remain open while atria contract but close when atria begin to relax
- Closure caused by swirling action in blood around valves when ventricle is full
- When ventricles start to contract pressure of blood in ventricles increases
- When pressure is above that of the atria, blood starts to move upwards
- Movement fills the valve pockets + keeps them closed
- Tendinous cords attached to the valves prevent them from turning inside out
- Prevents blood flowing back into atria
Describe the movement of blood through the heart in relation to the semilunar valves (from ventricular systole to diastole).
- Before ventricular contraction, pressure in major arteries > pressure in ventricles
- Semilunar valves are closed
- Ventricular systole raises pressure of blood in ventricles v quickly
- Once pressure in ventricles rises above pressure in major arteries, semilunar valves are pushed open
- Blood is under v high pressure so is forced out of ventricles in a powerful spurt
- Once ventricle walls finish contracting heart starts to relax (diastole)
- Elastic tissue in walls of ventricles recoils
- Stretched muscle out again + returns ventricle to its original size
- Causes pressure in ventricles to drop v quickly
- As it drops below pressure of major arteries, blood starts to flow back towards the ventricles
- Semilunar valves pushed closed by blood collecting in pockets of valves
- Preventing blood from returning to ventricles
- Pressure wave created when left semilunar valve closes is the pulse that we can feel at wrist/neck
What is it the pulse that can be felt at the wrist/neck?
Pressure wave created from left semilunar valve closing
Describe the pressure changes of the blood as it travels around the blood vessels and how does the structure of arteries help with that.
- Artery walls close to heart have lots of elastic tissue. When blood leaves heart these walls stretch
- As blood moves on + out of aorta pressure in aorta starts to drop
- Elastic recoil of wall helps maintain blood pressure in aorta
- Further blood flows along arteries, more the pressure drops + fluctuations become less obvious
- Important to maintain pressure gradient between arteries + arterioles as this keeps blood flowing towards tissues
- Fluctuations in pressure caused by pumping of heart
- Decreasing pressure from increased cross sectional area of arteries
- Low pressure in arteries
What is fibrillation?
When contractions of chambers aren’t synchronised
What initiates the heartbeat?
SAN - sino-atrial node. A small patch of tissue that generates electrical activity - a wave of electrical excitation, 55-80 times a minute in humans
Known as the pacemaker
Describe how the heartbeat is initiated and how the contractions of the 4 chambers are coordinated.
- SAN initiates a wave of electrical excitation
- Wave of excitation spreads over walls of both atria, travelling along membranes of muscle tissue
- As wave of excitation passes, causes cardiac muscle to contract: atrial systole
- Tissue at base of atria unable to conduct wave so can’t spread directly down ventricle walls. At top of septum is AVN (atrio-ventricular node)
- AVN delays wave for 0.1 seconds to allow time for atria to finish contracting + blood to flow into ventricles before they begin to contract
- After delay, wave is carried away from AVN + down conducting tissue: Purkyne fibres, that run down septum
- At base of septum, wave spread out over walls of ventricles
- Causes ventricular muscles to contract from apex upwards
- Pushes blood upwards to the major arteries at the top of the heart
On an electrocardiogram (ECG) what do P, Q, R, S and T represent?
- P: excitation of atria (atrial systole)
- QRS complex: excitation of ventricles (ventricular systole)
- T: diastole
What is the normal heartbeat rhythm known as?
Sinus rhythm
What is bradycardia?
Abnormally slow heart rate
What is tachycardia?
Abnormally fast heart beat
What is atrial fibrillation?
Atria beating more frequently than ventricles - no clear P waves seen
What is an ectopic heartbeat?
The third beat is an early ventricular beat. Patient often fells as though a heartbeat has been missed
What is the word equation for the association for oxygen with RBCs?
oxygen + haemoglobin –> oxyhaemoglobin
What is the structure of haemoglobin?
- Protein
- 4 subunits, each consisting of a polypeptide chain + a haem (non-protein) group
- Haem group contains a single iron ion in the form Fe2+
- Iron ion can attract + hold an oxygen molecule
- Haem group said to have a high affinity for oxygen
- 4 haem groups means 4 oxygen molecules can be held per haemoglobin
- 280 million Hb molecules in each RBC
How does haemoglobin help to maintain a steep concentration gradient at the alveoli?
When oxygen diffuses into capillary binds to Hb so taken out of solution so maintains steep concentration gradient of oxygen
What affects haemoglobin’s ability to associate with oxygen?
pO2/partial pressure of oxygen/oxygen tension
What causes the haemoglobin dissociation curve to be S shaped rather than being linear i.e. a straight line?
-Haem groups are at the centre of Hb molecule making
it difficult for oxygen molecules to reach and therefore associate with. Difficulty in binding with first O2 molecule explains low saturation level of haemoglobin at low pO2
-As pO2 rises, diffusion gradient into Hb molecule increases. Eventually 1 O2 molecule enters Hb molecule + associates with one of its haem groups, causing conformational (shape) change, allowing O2 molecules to enter Hb molecule + associate with haem groups more easily, hence steepness in curve as pO2 rises
How is the partial pressure of the lungs and respiring tissues suitable for oxygen to be transported from the lungs the respiring tissue?
- pO2 in lungs high enough to produce close to 100% saturation of oxyhaemoglobin
- pO2 of respiring tissues low enough for oxyhaemoglobin to dissociate for oxygen to be released for respiring tissues
How is foetal haemoglobin different from adult haemoglobin?
Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin
Why does fetal haemoglobin need to have a higher affinity for oxygen than adult haemoglobin?
-Fetal haemoglobin must associate with oxygen in an environment where the pO2 is low enough from the adult oxyhaemoglobin to dissociate
How does fetal haemoglobin obtain oxygen from adult oxyhaemoglobin?
- Placenta
- pO2 low enough for adult oxyhaemoglobin to dissociate but high enough for fetal haemoglobin to associate to oxygen
- Fetal haemoglobin absorbs oxygen from surrounding fluid
- Reduces pO2 of placenta further
- Oxygen diffuses from mother’s blood fluid into placenta
- Reduces pO2 of mother’s blood making the maternal haemoglobin release more O2 (dissociate)
How is carbon dioxide transported in the body?
- 5% dissolved directly in plasma
- 10% combined directly w haemoglobin as carbaminohaemoglobin
- 85% transported in the form HCO3 - ions
(MA) How does hydrogencarbonate ions form?
- CO2 diffuses into RBCs
- CO2 reacts with water, catalysed by the carbonic anhydrase enzyme, forming carbonic acid H2CO3
- Carbonic acid dissociates to form H+ ions and HCO3 -
- H+ ions make conditions acidic in RBCs
- To stop this H+ ions combine w haemoglobin in RBCs to form haemoglobinic acid (HHb)
- Chloride ions move from plasma to RBCs to maintain charge - chloride shift
- Haemoglobin acts as a buffer (maintains constant pH)
How does oxygen get into respiring tissues?
- pO2 in respiring tissues is lower than that of the lungs as O2 is used in aerobic respiration
- Oxyhaemoglobin dissociates + releases oxygen to these tissues
- Haemoglobin available to take up H ions to form haemoglobinic acid as more CO2
- Where tissues are active lots of CO2 released, affecting the haemoglobin (Bohr effect)
(MA+) Describe the Bohr effect.
- Low pO2 (e.g. in respiring cells) oxyhaemoglobin dissociates + releases O2
- When CO2 present (e.g. in respiring tissues) more carbonic acid to dissociate + form more H+ ions
- H+ ions displace O2 molecules on Hb + form more HHb
- So presence of CO2 = more O2 released: Bohr effect
- Bohr effect results in O2 being more readily released when more CO2 produced from aerobic respiration. Releasing more CO2 means need more O2 for aerobic respiration
- Also: CO2 enters RBC forming H2CO3 with water that dissociates forming H+ ions that make cytoplasm more acidic. pH changes tertiary structure of Hb (as it’s a protein) reducing Hb’s affinity for O2 so can’t hold as much + it’s released from oxyHb to respiring tissues
- Conclusion: when more CO2 present Hb becomes less saturated w O2. Reflected in a change to Hb dissociation curve, shifting down + right w more CO2
(MA) Describe the control of the cardiac cycle in the heart.
- SAN initiates wave of electrical excitation
- Spreads over atrial walls
- Causing atrial systole (atria contracting), both simultaneously
- Band of fibres between atria + ventricles stops wave passing directly to ventricular walls
- Wave reach AVN on septum that delays wave for 0.1s to allow atrial systole to complete before ventricular systole
- Wave spreads down septum to bundle of His + then to Purkyne fibres
- Reaches apex and moves upwards
- Ventricles contract simultaneously
- Ventricles contract from apex upwards to pump blood upwards into arteries to completely empty ventricles
(MA) What is the function of the arteries?
Carry blood away from the heart at high pressure
(MA) What is the structure of the arteries?
-Small lumen to maintain high pressure
-Wall:
> Thick + contains collagen to give strength to withstand high pressure
> Elastic tissue: stretch when heart pumps + allows recoil to maintain high pressure when heart relaxes
> Smoot muscle: contract + constrict artery to narrow lumen (e.g. in vasoconstriction to redirect blood flow, maintains high pressure)
(MA) What is the function of the veins?
Carry blood back to the heart at low pressure
(MA) What is the structure of the veins?
- Lumen large to make flow of blood easier, lower resistance
- Thinner walls: thinner layers of collagen, elastic tissue + smooth muscle as don’t need to withstand high pressure + aren’t used to constrict blood flow
- Valves: stop blood flowing in wrong direction + help it back to the heart
(MA) What is the function of the capillaries?
Allow exchange of materials between blood cells
(MA) What is the structure of capillaries?
- Thin walls of flattened endothelial cells (squamous epithelial) to reduce diffusion distance
- Narrow lumen: squeezes RBCs up next to wall to reduce diffusion distance further
(MA) Describe the formation of tissue fluid.
- Due to contractions of heart, blood at high HS pressure at arteriole end of capillary
- Between cells of capillary walls there are many small gaps
- HS pressure greater than osmotic pressure
- Forces fluid out of capillaries carrying plasma + dissolve substances e.g. oxygen + glucose + neutrophils with it: this is tissue fluid
- RBCs, proteins + some WBCs can’t leave capillaries as they’re too large
(MA) How does some tissue fluid reenter the capillaries?
- HS pressure lower at venule end
- Osmotic pressure (in direction of capillary) now greater
- Due to presence of plasma proteins in blood that lower water potential
- Fluid moves back into capillary taking dissolved waste e.g. CO2 with it
(MA) Describe the formation of the lymph.
- Not all tissue fluid returns to capillaries
- Pores allow fluid to leave tissue fluid + enter lymph vessels
- It will remove proteins (made by cells) out of tissue fluid + neutrophils from tissue fluid
- Low in O2 + glucose (as used by cells)
- More CO2 + waste (made by cells)
- Lot of fats absorbed from intestine
- Contains lymphocytes (WBCs produced in lymph node) which engulf + digest bacteria in lymph fluid: part of immune system
(MA) What are the contents of the blood?
- RBCs
- Neutrophils
- Platelets
- Large proteins
- SOME fats
- Glucose
- Amino acids
- Oxygen
- LITTLE CO2
(MA) What are the contents of the tissue fluid?
-Neutrophils
(-Large proteins)
-LESS glucose than blood (as used by cells)
-LESS amino acids than blood (as used by cells)
-LESS oxygen than blood (as used by cells)
-MORE CO2 than blood (as released by cells)
(MA) What are the contents of the lymph vessel?
-Neutrophils
-Lymphocytes
(-Large proteins, same as the tissue fluid as too small to get through pores into capillary)
-Fats
-LITTLE glucose
-FEW amino acids
-LITTLE oxygen
-CO2
(MA) Where are erythrocytes found?
Blood (NOT tissue fluid or lymph)
(MA) Where are neutrophils found?
Blood, tissue fluid + lymph
(MA) Where are lymphocytes found?
Lymph vessel (NOT blood or tissue fluid)
(MA) Where are platelets found?
Blood (NOT tissue fluid or lymph)
(MA) Where are large proteins found?
Blood and maybe in tissue fluid + lymph (lymph same as tissue fluid as too large to get through capillary pores so has to be drained via lymph)
(MA) Where are fats found?
Lymph + some in blood (NOT in tissue fluid)
(MA) Where are glucose found?
Blood, less in tissue fluid as used in respiration + little in lymph
(MA) Where are amino acids found?
Blood, less in tissue fluid as cells use it + few in lymph
(MA) Where is oxygen found?
Blood, less in tissue fluid as used in respiration + little in lymph
(MA) Where is carbon dioxide found?
Little in blood, more in tissue fluid as released from aerobic respiration, in the lymph
(MA) Explain the shape of the haemoglobin dissociation curve.
-Low pO2: low saturation of Hb w O2; haem group at centre so difficult to associate
-As pO2 increases: faster increase in saturation
> Higher conc of O2, steeper gradient for diffusion of O2 into haemoglobin
> When 1 O2 associated, conformational shape change of Hb so easier for O2 to diffuse in + associate
-High pO2: saturation high but levels of as unlikely to reach 100%
> When 3 O2 associated, difficult for 4th molecule to diffuse in + associate to reach 100% even at highest possible pO2
(MA) Why is it important that 2-5kPa is the steepest part of the haemoglobin dissociation curve?
- Low pO2 oxygen dissociates from Hb
- Happens in respiring tissues
- Steepest part of curve between 2-5kPa: drop in pO2 gives large group in saturation + releases a lot of O2
- Corresponds to pO2 in respiring tissue as they need a lot of O2 for aerobic respiration
(MA) Why is it important that foetal and adult haemoglobin is different?
- Foetus gains O2 for respiration from mother across placenta
- pO2 in placenta is low (2-4kPa)
- Maternal Hb releases O2
- Foetal Hb has higher affinity for O2
- Maintains a diffusion gradient towards foetus
(MA) Why is it important that after birth adult haemoglobin replaces foetal haemoglobin?
- Affinity of foetal Hb for O2 would be too high
- So wouldn’t release O2 readily enough
- Pregnant mothers would need a different between affinity between their Hb + their foetus for oxygen
What is the pulmonary circuit?
Carries blood to the lungs to become oxygenated
What is the systemic circuit?
Carries blood with O2 + nutrients to the body cells
What are the advantages of a double circulatory system?
- Blood can be maintained at higher pressure in systemic circuit so delivered more quickly
- Slightly lower pressure can be maintained in pulmonary circuit to prevent damage to capillaries in lungs
- Mammals more active than fish + maintain own body temp, both requiring lots of energy + therefore good + quick supply of O2 + glucose to cells
What are the external features of the heart?
- Made of cardiac muscle (myogenic)
- Most of heart is 2 ventricles - v thick walls of muscle
- Above ventricles are atria w thinner walls
- Coronary arteries lie over surface of heart - supply cardiac muscle w O2 for aerobic respiration
- If coronary artery becomes blocks it restricts blood flow + therefore delivery of O2 to muscle. Can cause myocardial infarction
- Top of heart are arteries + veins
- Bottom of the heart that comes to a point is apex
What is the endothelium?
Tissue that lines inside of a structure e.g. blood vessel
What is the surface of the endothelium like?
Very smooth to reduce friction
What is atrial systole?
Atria contract reducing volume + increasing pressure + blood goes down pressure gradient into ventricles
What is ventricular systole?
Ventricles contract, reducing volume + increasing pressure above that of the arteries (aorta + pulmonary artery) so blood moves down pressure gradient
What happens to the pressure of the blood during diastole?
Pressure decreases + heart starts to refill w blood
What happens during atrial systole?
- Both atria contract
- Causes further increase in pressure in atria
- Increase in pressure causes blood to be pumped through open AV valve into ventricles (causing vol in ventricles to increase)
What happens during diastole?
- Atria + ventricles relax + recoil
- Blood flows from veins into atria
- Pressure in ventricles lower than in atria
- Blood flows through open AV valves into ventricles
- Vol in atria + ventricles increases
- Pressure in atria + ventricles slowly increases
What does myogenic mean?
Muscle tissue that generates its own contractions
What is the heart’s own pacemaker?
SAN
What are the waves of electrical excitation (in the cardiac cycle) also known as?
Electrical impulses/waves of depolarisation
How is the heartbeat initiated and controlled?
- SAN initiates wave of electrical excitation which spreads over atrial wall causing atrial systole/atria to contract simultaneously
- Band of fibres between atria + ventricles stops wave passing directly to ventricular walls
- Wave of excitation reaches AVN on septum
- AVN delays wave for 0.1s to allow atrial systole to complete before ventricular systole
- Wave spreads down septum to double of His + then to Purkyne fibres
- Ventricles contract from apex upwards to pump blood upwards into arteries to completely empty ventricles
- Ventricles contract simultaneously
What is an ECG used for?
Monitor electrical activity of the heart
Why are there less amino acids in tissue fluid than the blood?
Used by cells in protein synthesis
Why are there fats in the lymph but not in the tissue fluid?
Absorbed from the small intestine
Describe the change in blood pressure as you go around the systemic circuit.
- Further away from heart decreases pressure
- Arteries: high pressure as near heart, so still feeling force of ventricular contractions so fluctuations in pressure (ventricular systole increases pressure + diastole decreases pressure). High pressure maintained by small lumen + elastic recoil
- Arterioles: pressure drops as further away from heart. Increased cross sectional area increases friction. Reduces pressure so blood can flow through capillaries w/out damaging them
- Capillaries: no fluctuations as no elastic tissue for recoil, lower pressure to prevent bursting. Pressure decreases still as further from heart
- Veins: large lumen to reduce friction
How many O2 molecules can each haemoglobin hold?
4
Describe the structure of haemoglobin.
- Found in erythrocytes - haemoglobin (protein) transports O2 as oxyhaemoglobin
- Has 4 subunits (2 alpha 2 beta) each made of a polypeptide chains a prosthetic (non amino acid) haem group
- Haem group contains 1 Fe2+ each which has an affinity for O2. Each one can attract + hold 1 O2 molecule
What is dissociation?
Breakdown of a molecule into 2 molecules (e.g. oxyhaemoglobin dissociates into oxygen + haemoglobin)
How does hydrogencarbonate form?
- CO2 diffuses into RBCs
- CO2 reacts w water
- Reaction catalysed by carbonic anhydrase enzyme
- Forms carbonic acid H2CO3
- Carbonic acid dissociates to form H+ ions + HCO3 - ions
What is HbO8?
Oxyhaemoglobin
What are chloride ions used for during the formation of hydrogencarbonate ions?
When HCO3 - ions diffuse out of RBC Cl- ions diffuse in to maintain charge
How does haemoglobin act as a buffer?
- H+ ions make conditions acidic
- Hb has higher affinity for H+ ions than O2 molecules, so binds to H+ ions + dissociates from oxygen to form HHb (haemoglobinic acid) increasing pH again
Why is it good that haemoglobin has a higher affinity for hydrogen ions than oxygen molecules?
- Tissues where lots of aerobic respiration occurring, more O2 needed + more CO2 produced
- CO2 ultimately leads to H+ ions as hydrogencarbonate ion dissociates
- H+ ion associates with Hb causing oxygen to dissociate so more readily available to be used in respiring cells for respiration
What causes the drop in pressure as the blood goes around the systemic circuit?
- Further away from heart
- Friction/resistance to flow caused by increase in cross sectional area
- Dissipation of elastic recoil
- Increasing volume of capillaries
Why might a person with a fibrillating heart be unlikely to survive for long if left untreated?
- Heart contractions aren’t coordinated
- Lack of PRT
- Reduced cardiac output
- Can’t get necessary oxygen to respiring cells
Other than their contents, what difference is there between tissue fluid and blood?
Tissue fluid is not contained in vessels where as blood is
