animal transport

Question 1

how do elastic fibres, smooth muscle and collagen utilised in blood vessels

Answer 1

elastic fibres - these are composed of elastin and can stretch and recoil, providing vessell walls with flexibility
smooth muscle - contracts or relaxes, which changes the size of the lumen
collagen - provides structural support to maintain the shape and volume of the vessel

Question 2

structure of arteries - what is the tunica intima

Answer 2

• consists of three layers: tunica externa, tunica media and tunica intima
• ## tunica intima - is made up of an endothelial layer, a layer of connective tissue and a layer of elastic fibres <– the endothelium is one cell thick and lines the lumen of all blood vessels, it is very smooth and reduces friction for free blood flow

Question 3

what is the tunica media

Answer 3

made up of smooth muscle cells and a thick layer of elastic tissue
- the layer of muscle cells strengthen the arteries so they can withstand high pressure. it also enables them to contract and narrow the lumen for reduced blood flow
- the elastic tissue helps to maintain blood pressure in the arteries. it stretches and recoils to even out any fluctuations in pressure

Question 4

what is tunica externa

Answer 4

• mostly made up of collagen
  <– a stroong protein protects blood vessels from damage by over stretching
• ## arteries have a narrow lumen which helps to maintain a high blood pressure

Question 5

structure of arterioles

Answer 5

• possess a muscular layer that means they can contract and partially cut off blood flow to specific organs
• when the smooth muscle in the arteriole contracts it constricts the vessel and precents blood flowing into a capilllary bed. - vasoconstriction
• when the smooth muscle in the wall of an arteriole relaxes, blood flows through into the capillary bed - vascodilation

Question 6

why is the tunica media thinner in veins

Answer 6

there is no need for a thick muscular layer as veins don’t have to withstand high pressure

Question 7

why do veins have a large lumem

Answer 7

• helps to ensure that blood returns to the heart at an adequate speed
• a large lumen reduces friction between the blood and endothelial layer of the vein
• the rate of blood flow is slower in veins but a larger lumen means the volume of blood delievered per unti of time is equal
• valve - prevent backflow of blood

Question 8

what are venules + their structure

Answer 8

venules connect the capillaries to the veins
- they have few or no elastic fibres and a large lumen
- as blood is at low pressure after passing through the capillaries there is no need for a muscular layer

Question 9

structure and function of capillaries

Answer 9

• very small lumen which forces blood to travel slowly providing more opportunity for diffusion to occur
• a large number of capillaries branch between cells so substances can diffuse between the blood and cells quickly as there is a short diffusion distance
• the wall of the capillary is made solely from a single layer of endothelial cells
  —> only one cell thick which reduces the diffusion distance for oxygen and carbon dioxide between the blood and tissues of the body
  –> cells of the wall have gaps called pores which allow blood plasms to leak out and form tissue fluid
  –> white blood cells can combat infection in affected tissues by squeezing through intercellular junctions in the capillary walls

Question 10

explain the flow deoxygenated of blood around the body including the heart

Answer 10

• deoxygenated blood enters the right artrium through the vena cave (superior and inferior)
• slight pressure builds up until the atrio-ventricular valve opens to let blood pass into the right ventricle
• when both the atrium and ventricle are filled with blood the atrium contracts, forcing all blood into the right ventricle
• as the right ventricle starts to contractm the atrio-ventricular closes preventing any backflow of blood tto the atrium
• the right ventricle contracts fully and pumps deoxygenated blood through the semiluner valves into the pulmonary artery, which transports ito to the capillary beds of the lungs
• the semiluner valves prevent the backflow of blood into the heart

Question 11

explain the flow of oxygenated blood

Answer 11

• oxygenated blood enters the left atrium from the pulmonary vein
• as pressure in the atrium builds the atrioventricular opens between the left atrium and left ventricle so the ventricle also fills with oxygenated blood
• when both the atrium and ventricle are full the atrium contracts forcing all oxygenated blood into the left ventricle.
• the left ventricle then contracts and pumps oxygenated blood through semilunar valves into the aorta and around the body
• as the ventricle contracts the atrioventricular valve closes, preventing any backflow of blood

Question 12

why is the left side of the heart thicker

Answer 12

• the lungs are relatively close to the heart and the lungs are also much smaller than the rest of the body so the rights side has to pump blood and relatively short distance and only has to overcome the resistance of the pumonary circulation
• the left side has to produce sufficient force to overcome the resistance of the aorta and the arterial systems of the whole body and move the blood under pressure to all extremities of the body

Question 13

what is the septum

Answer 13

inner dividing wall of the heart which prevents the mixing of deoxygenated and oxygenated blood

Question 14

explain the ‘lub-dub’ sound of the heart

Answer 14

• the first sound comes as the blood is forced against the atrio-ventricular valves as the ventricles contract
• the second sound comes as a backflow of blood closes the semilunar valves in the aorta and pumonary artery as the ventricles relax

Question 15

explain the basic rhythm of the heart (wave of electrical excitation)

Answer 15

• a wave of eletrical excitation begins in the pacemaker area called the sinoatrial node (SAN), causing the atria to contract and so initiating the heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles
• the eletrical activity is picked up by the atrio-ventricular node. the AVN imposes a slight delay before stimulating the bundle of His, a bundle of conducting tissue made of fibres (purkyne fibres), which penetrate through the septum between the ventricles #
• the bundle of His splits into two branches and conducts the wave of excitation to the apex (bottom) of the heart
• at the apex, the purkyne fibres spread out through the walls of the ventricles on both sides. the spread of excitation triggers the contraction of the ventricles, starting at the apex
• contraction starting at the apex allows more efficient emptying of the ventricles

Question 16

why does the atrioventricular node impose a slight delay before stimulating the bundle of His

Answer 16

to ensure that the atria have stopped contracting before the ventricles start

Question 17

what is used to record the electrical activity of the heart

Answer 17

an electrocardiogram (ECG)

Question 18

how to ECG’s work and what are they used for

Answer 18

• electrodes are stuck painlessly to clean skin to get the good contacts needed for reliable results.
• the signal from each electrodes is fed into the machine, which produces an ECG
• they’re used to help diagnose heart problems

Question 19

what is a bradycardia

who often has it
what is needed to help alter it

Answer 19

when the heart rate slows down to below 60bpm.
- many people have bradycardia if they’re fit as training makes heart ebat more slowly and efficiently
- severe bradycardia can be serious and need an artificial pacemaker to keep the heart beating steadily

Question 20

what is tachycardia

when it is normal and abnormal

Answer 20

when the heart beat is too fast, over 100 bpm
- often normal if you do exercise or have a fever etc
- abormal it may be caused by problems in the electrical control of the heart and may need to be treated by medication or by surgery

Question 21

what is an ectopic heartbeat

Answer 21

extra heartbeats that interrupts the regular rhythm
- most people have at least one a day, they’re usually normal but can be linked to serious conditions when they are very frequent

Question 22

what is atrial fibrillation

Answer 22

• a really irregular heartbeat
• atria or ventricles completely lose their rhythm and stop contracting properly
• can result in anything from chest pain and fainting to lack of pulse and death

Question 23

structure of haemoglobin

Answer 23

• found in red blood cells and its role is to carry oxygen around the body
• haemoglobin is a large protein with a quaternary structure
• its made up of four polypeptide chains
• each chain has a haem group which contains iron (red colour)
• each molecule of human haemoglobin can carry four oxygen molecules

Question 24

what does oxygen binding to haemoglobin create

Answer 24

oxyhaemoglobin

Question 25

how does partial pressure of oxygen affect affinity of oxygen

Answer 25

partial pressure is a measure of oxygen concentration <-- the greater the concentration of dissolved oxygen in cells, the higher the partial pressure - as the partial pressure of oxygen increases, haemoglobins affinity of oxygen also increases - oxygen loads onto haemoglobin to form oxyhaemoglobin where there's a high pp - oxyhaemoglobin unloads its oxygen where there's a lower pp

Question 26

why is affinity of oxygen low in respiring tissues

Answer 26

when cells respire, they use up oxygen - this lowers the partial pressure. red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen

Question 27

what does an oxygen dissociation curve show

Answer 27

how saturated the haemoglobin is with oxygen at any given partial pressure the affinity of haemoglobin for oxygen affects how saturated the haemoglobin is

Question 28

why is a dissociation curve for adult haemoglobin an S shape

Answer 28

- saturation of haemoglobin can also affect the affinity - when the haemoglobin combines with the first oxygen molecule , its shape alters in a way that makes it easier for other molecules to join too - but as the haemoglobin starts to become saturated, it gets harder for more oxygen molecules want to join - as a result, the curve has a steep bit in the middle where its really easy for oxygen molecules to join - -> and shallow bits at each end where its harder - when the curve is steep, a small change in pp causes a big change in the amount of oxygen carried by the haemoglobin

Question 29

why does fetal haemoglobin have to have higher affinity of oxygen + why is it futher to the left on a dissociation graph

Answer 29

- important because the fetus gets oxygen from its mother's blood across the placenta - by the time the mothers blood reaches the placenta, its oxygen saturation has decreased because some has been used up by the mother's body. the placenta has a low pp so adult oxyhaemoglobin will unload its oxygen - for the fetus to get enough oxyegn to survive its haemoglobin has to have a higher affinity for oxygen than adult haemoglobin - this means fetal haemoglobin takes up oxygen (becomes more saturated) in lower pp than adult haemoglobin - its its haemoglobin had the same affinity for oxygen as adults, its blood wouldn't be saturated enough

Question 30

explain the **Bohr effect**

Answer 30

- most of the CO2 from respiring tissues diffuses into red blood cell# - here it reacts with water to form **carbonic acid**, catalysed by the enzyme **carbonic anhydrase** - the rest of the CO2 binds directly to the haemoglobin and is carried to the lungs - the carbonic acid **dissociates** to give up **hydrogen ions** and **hydrogencarbonate ions** - this increase in H+ ions causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up the H+ ions. 'mops up' - this forms a compound called **haemoglobonic acid** - to compensate for the loss of hydrogen carbonate ions from the red blood cells, chloride ions diffuse into the red blood cell < -- this is called the **chlorise shift** and maintains the balance of charge between the RBC and plasma - when the blood reaches the lungs and the low partial pressure of carbon dioxide it causes some hydrogencarbonate ions and hydrogen ions to recombine with CO2. - CO2 then diffuses into the alveoli and is breathed out

Question 31

what is tissue fluid

Answer 31

fluid that surrounds cells in tissues its made from substances that leave the blood plasma e.g. oxygen, water, nutrients cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it. in the capillary bed, substances move out of the capillaries, into the tissue fluid, by pressure filtration

Question 32

explain pressure filtration

Answer 32

- at the start of the capillary bed, nearest the arteries, the **hydrostatic pressure** inside the capillaries is greater than the HSP in the issue fluid - this difference forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid - as fluid leaves, the hydrostatic pressure reduces in the capillaries <-- so that the hydrostatic pressure is much lower at the end of the capillary bed that's nearest the venules - as water leaves the capillaries, the concentration of plasma proteins in the capillaries increase and the water potential decreases - plasma proteins in the capillaries generate a form of pressure called **oncotic pressure** - so at the venule end of the capillary bed, there's a high oncotic pressure and low water potential - because the water potential in the capillaries is lower than in the tissue fluid, some water re-enters the capillaries from the tissue fluid at the venule end by osmosis

Question 33

what is the use of lymph

Answer 33

- not all the tissue fluid re-enters the capillaries at the vein end - some is left over