Chap 8 - Transport in Animals PDF

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Populations and Sustainability...

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Biology Spec Led Revision Chapter 8 - Transport in Animals (a) the need for transport systems in multicellular animals. To include an appreciation of size, metabolic rate and surface area to volume ratio (SA:V). Circulatory Systems Multicellular organisms need transport systems 1) Single celled organisms can get substances via diffusion, multicellular cannot 2) Multicellular have low surface area to volume ratios, and a higher metabolic rates 3) A lot of multicellular organisms are also very active, which means there is a large number of cells respiring very quickly that need a constant rapid supply of glucose and oxygen 4) A transport system ensures that every cell can get the nutrients which it needs 5) In mammals, the circulatory system uses blood to carry glucose and oxygen around the body. Also carries hormones, antibodies and waste products. (b) the different types of circulatory systems Fish and Mammals have different circulatory systems Fish have a single circulatory system and mammals have a double circulatory system 1) In a single circulatory system, blood passes through the heart ONCE in one complete circuit of the body 2) In a double circulatory system, blood passes through the heart TWICE in one complete circuit of the body Fish: In fish, the heart pumps blood to the gills and then to the rest of the body in one complete circuit Mammal: - In mammals the heart is divided down the middle, so its really like two hearts joined together. - The right side pumps to the lungs to pick up oxygen. - From the lung the blood travels to the left side of the heart where it is pumped to the rest of the body. - Blood returns then to the right side of the heart.

Pulmonary System - Takes blood to the lungs Systemic System - Takes blood around the body An advantage of having double circulatory system is that it can give blood the extra push to get around the body faster, which means cells can get oxygen replenishment faster. Circulatory Systems can be open or closed Closed circulatory systems All vertebrates have CLOSED CIRCULATORY SYSTEMS - the blood is enCLOSED within blood vessels 1) The heart pumps blood into the ARTERIES, these branch out into millions of CAPILLARIES 2) Substances such as oxygen and glucose diffuse from the blood out of the capillaries into the body cells, but blood itself does not diffuse, only nutrients 3) Veins take blood back into the heart ! ARTERIES = AWAY VEINS = IN TO THE HEART

Open circulatory systems Some invertebrates have an OPEN CIRCULATORY SYSTEM - blood isn't enclosed within blood vessels all the time, instead it flows freely through the body cavity. 1) The heart is segmented. It contracts in a wave, starting from the back pumping blood into a single artery. 2) The artery opens up into the main body cavity 3) The blood flows around the insects organs, gradually making its way back into the heart via several valves The circulatory system in insects only transport nutrients and hormones to cells, it doesn't supply the cells with oxygen. This is done via the tracheal system. (c) the structure and functions of arteries, arterioles, capillaries, venules and veins. To include the distribution of different tissues within the vessel walls. Blood Vessels Blood vessels transport substances around the body 5 types of blood vessel: 1) Arteries - Carry blood from heart to the rest of the body. - Thick muscular walls that have elastic tissue to stretch and recoil with heart beats (helps maintain pressure) - Folded ENDOTHELIUM (inner lining), allowing the artery to expand - All arteries carry OXYGENATED BLOOD, apart from the pulmonary arteries, which take deoxygenated blood to the lungs. 2) Arterioles - Arteries branch into arterioles which are smaller than arteries. - Arterioles have a layer of smooth muscle but less elastic tissue - The smooth muscle allows them to expand or contract, controlling the amount of blood going to tissues 3) Capillaries - Arterioles branch into capillaries - Are the smallest blood vessels in the body - Substances like glucose and oxygen diffuse out from capillaries to the cells - They adapted for efficient diffusion (by them having thin one cell thick walls) 4) Venules - Capillaries branch into venules - They have very thin walls that contain some muscle cells - Venules join together to form veins 5) Veins - Take blood back from the body to the heart under low pressure - They have a wider lumen compared to arteries - Little muscle or elastic tissues - Contains valves to stop back flow of blood - Blood flows through veins is helped by muscle contractions from body around them - All veins carry deoxygenated blood apart from the pulmonary veins which carry oxygenated blood from the lungs into the heart.

(d) The formation of tissue fluid from plasma. To include reference to hydrostatic pressure, oncotic pressure and an explanation of the differences in the composition of blood, tissue fluid and lymph. Tissue Fluid is formed from Blood • Tissue fluid is the fluid that surrounds cells in tissues. • It is made from substances that leave the blood plasma e.g. oxygen, water, nutrients • Unlike blood, tissue fluid does not contain red blood cells or big proteins because they are too large to fit through the capillary wall • Cells take in oxygen and nutrients from the tissue fluid, and release waste products into it • In a capillary bed (the network of capillaries in an area of tissue) substances move out of the capillaries, into the tissue fluid, by PRESSURE FILTRATION. 1) At the start of the capillary bed, nearest the arteries, the HYDROSTATIC PRESSURE inside the capillaries is higher than that of the hydrostatic pressure in the tissue fluid. 2) The difference in hydrostatic pressure leads to the forcing of fluid out of the capillaries and into the spaces around the cells, forming tissue fluid. 3) As fluid leaves, the hydrostatic pressure inside of the capillary bed decreases compared to the hydrostatic pressure in the tissue fluid.

4) Oncotic pressure also occurs, generated by plasma proteins present in the capillaries which lower the water potential. 5) The oncotic pressure is lower in the capillaries compared to that of the oncotic pressure in the tissue fluid, due to the fluid lost. 6) This means that some water re-enters the capillaries from the tissue fluid at the venue end by osmosis.

Excess tissue fluid drains into the lymph vessels Not all tissue fluid is reabsorbed into the capillaries at the venue end of the capillary bed. Some excess tissue fluid is left over. This extra fluid eventually gets returned to the blood via the LYMPHATIC SYSTEM - a drainage system, made up of lumps vessels. 1) The smallest lymph vessels are the lymph capillaries 2) Excess fluid passes into lymph vessels. Once inside it is called lymph 3) Valves in the lymph vessels stop the lymph going backwards (like in veins) 4) Lymph gradually moves towards the main lymph vessels in the thorax (chest cavity). Here it is returned to the blood near the heart.

Differences Between Blood, Tissue

Fluid and Lymph Blood

Tissue Fluid

Lymph

Comment

Red Blood Cells

Yes

No

No

Red blood cells are too big to get through the capillary walls into tissue fluid.

White Blood Cells

Yes

Few

Yes

Most white blood cells are in the lymph system. They only enter tissue fluid when theres an infection

Platelets

Yes

No

No

Only present in tissue fluid if the capillaries are damages

Proteins

Yes

Few

only antibodies

Most plasma proteins are too big to get through the capillary walls

Water

Yes

Yes

Yes

Tissue fluid and lymph have a higher water potential than blood

Dissolved Solutes (Ions)

Yes

Yes

Yes

Solutes can move freely between blood, tissue fluid and lymph.

(e) (i) The external and internal structure of the mammalian heart. (ii) the dissection, examination and drawing of the external and internal structure of the mammalian heart. The Heart Consists of Two Muscular Pumps Right side of the heart pumps deoxygenated blood to the lungs. The left side pumps oxygenated blood to the rest of the body.

Valves in the heart prevent blood flow in the wrong way The atrioventricular valves link the atria to the ventricles The semi-lunar valves link the ventricles to the pulmonary artery and aorta 1) The valves only open one way, whether they're open or closed depends on the relative pressure of the heart chambers 2) If theres a higher pressure behind a valve its forced open 3) If there a higher pressure in front of a valve its forced closed

(f) the cardiac cycle. To include the role of the valves and the pressure changes occurring in the heart and associated vessels. The Cardiac Cycle The cardiac cycle is an ongoing sequence of contraction and relaxation of the atria and ventricles that keep blood continuously circulating round the body. 1) Ventricles relax, atria contract - Ventricles relax - Atria contract decreasing their volume, but increasing the pressure - Blood flows from the atria into the ventricles via the atrioventricular valves - Ventricles experience a slight increase in pressure, due to the ejected blood from the atria into ventricle 2) Ventricles contract, atria relax - Atria relax - Ventricles contract, decreasing their volume, increasing their pressure - Pressure in ventricle is higher than in atria, forcing the atrioventricular valve to shut - High pressure in the ventricle forces the semi-lunar valve to open and allow blood into the pulmonary artery and aorta 3) Ventricles relax, atria relax - Ventricles and atria both relax - Higher pressure in the pulmonary artery and aorta forces the semi-lunar valves to shut - Atria fill with blood, due to the increased pressure in the vena cava compared to the atria - The pressure in the ventricles falls below the atria, and so blood flows passively into the ventricle

(g) How heart action is initiated and coordinated. To include the roles of the sino-atrial node (SAN), atrio-ventricular node (AVN), purkyne tissue and the myogenic nature of cardiac muscle (no detail of hormonal and nervous control is required at AS level). Cardiac muscle controls the regular beating go the heart Cardiac muscle is MYOGENIC 1) The SINO-ATRIAL NODE (SAN) is like the pacemaker for the heart, sending out regular waves of electrical activity to the atrial walls 2) Causing the right and left atria to contract at the same time

3) A band of non-conductive collagen tissue stops the electrical signal from being passed from the atria to the ventricle

4) Instead, these waves of electrical activity are transferred from the SAN to the atrioventricular node (AVN). 5) The AVN is responsible for passing the waves of electrical activity onto the bundle of His. But there is a slight delay ensuring that the atrium have fully emptied 6) The bundle of His is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the left and right ventricular walls, called the Purkyne tissue 7) The Purkyne tissue carries waves of electrical activity into the muscular walls of the right and left ventricles causing them to contract simultaneously, from the bottom up.

(h) The use and interpretation of electrocardiogram (ECG) traces. To include normal and abnormal heart activity e.g. tachycardia, bradycardia, fibrillation and ectopic heartbeat. Electrocardiogram The heart muscle depolarises when it contracts, and depolarises when it relaxes. The trace seen of this is called an electrocardiogram (ECG) A normal ECG trace looks like this: PQRS - are points within an ECG which show different events within the cardio cycle P Wave - The contraction (depolarisation) of the atria PR segment - The delay for the contraction of ventricles, in order to allow atria to fully empty QRS complex - The contraction (depolarisation) of the ventricles T Wave - Relaxation (re-polarisation) of the ventricles The height indicates how much electrical charge is passing through the heart - the bigger wave means more electrical charge, so means a bigger contraction for the P and R waves.

ECG’s to Diagnose Heart Problems Doctors can compare their patients ECG with an normal trace, this helps them diagnose any heart problems. Tachycardia: - When the heart is beating too fast. - Around 120 BPM, it might be ok during exercise but not during rest - It can show that the heart isn't pumping blood effectively/ efficiently

Bradycardia: - When the heart is beating too slow - Around 60 BPM at rest

Ectopic Heartbeat: - An extra heartbeat - Caused by an earlier contraction of the atria than in previous heartbeats - Caused by earlier contraction of the ventricles too however - Occasional ectopic heartbeats in healthy people are okay

Fibrillation: - Irregular heartbeat - Atria or ventricles lose their rhythm entirely and stop contracting properly - Result in chest pain to lack of pulse, fainting or death

(i) the role of haemoglobin in transporting oxygen and carbon dioxide. To include the reversible binding of oxygen molecules, carbonic anhydrase, haemoglobinic acid, HCO3– and the chloride shift. Oxygen is carried around the body as OXYHEMOGLOBIN 1) Red blood cells contain haemoglobin (Hb) 2) Haemoglobin is a large protein with a QUATERNARY structure - being made ip of more than one polypeptide chain 3) Each chain has a haem group which contains iron and given haemoglobin its red colour 4) Haemoglobin has a HIGH AFFINITY for oxygen - each molecule can carry 4 x O2 5) In the lungs, oxygen joins the iron in haemoglobin to form OXYHEMOGLOBIN 6) This is a reversible reaction, meaning oxygen LEAVES the oxyhemoglobin when it is near the cells and turns back into HAEMOGLOBIN. Hb + 4O2 HbO8 Haemoglobin + Oxygen Oxyhaemoglobin Haemoglobin Saturation depend on the Partial Pressure of Oxygen The partial pressure of oxygen (pO2) is a measure of oxygen concentration The greater the concentration of dissolved oxygen in cells, the higher the partial pressure Similarly, the partial pressure of carbon dioxide (pCO2) is a measure of the concentration of CO2 in a cell. Haemoglobin’s affinity for oxygen varies depending on the partial pressure of oxygen Oxygen loads onto haemoglobin forming oxyhemoglobin where theres a high pO2. Oxyhemoglobin unloads its oxygen where there is a lower pO2. Oxygen enters blood capillaries at the alveoli in the lungs. Alveoli have a high pO2 so oxygen loads onto haemoglobin to form oxyhemoglobin. When cells respire they also use up oxygen, this lowers the pO2. Red blood cells can deliver oxyhemoglobin to respiring tissues, where it unloads its oxygen The haemoglobin then returns to the lungs to pick up more oxygen.

Dissociation curves show who affinity for oxygen varies An oxygen dissociation curve shows how saturated the haemoglobin is with oxygen at any given partial pressure.

Where pO2 is high haemoglobin has a high affinity for oxygen, so it will have a high saturation of oxygen. Where pO2 is low haemoglobin has a low affinity for oxygen meaning it releases oxygen rather than combining with it. Thats why there is a low saturation of oxygen. The S-shaped graph is this way because when haemoglobin combines with the first O2 molecule, its shape alters in a way which makes it easier for other oxygen molecules to join too. But as the Hb starts to become saturated, it becomes harder for the oxygen to bind 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 it is harder. When there curve is steep a small change in pO2 causes a big change in the amount of oxygen carried by the Hb. Carbon dioxide concentrations affect oxygen unloading Oxygen is given more readily when there is higher pCO2 concentrations. It is a way to get more oxygen to cells during activity. When cells respire they produce carbon dioxide, raising the pCO2, increasing the rate of oxygen unloading. The reason for why CO2 affects blood pH. Most CO2 from respiring tissues diffuses into red blood cells. Here the CO2 reacts with WATER to form CARBONIC ACID, catalysed by the enzyme CARBONIC ANHYDRASE. (The remaining 10% of CO2 is bonded to haemoglobin and sent back to lungs).

The carbonic acid DISSOCIATED (splits) to give hydrogen H+ ions and hydrogen carbonate ions (HCO3-). The increase of H+ ions causes oxyhemoglobin to unload its oxygen so that haemoglobin can take up H+ ions. This forms a compound called haemoglobinic acid. The HCO3- ions diffuse out of the red blood cells and are transported in the blood plasma. To compensate for the loss of HCO3- ions from the red blood cells, chloride (Cl-) ions diffuse into the red blood cells. This is called the chloride shift and it presents any change in pH that could affect cells. When the blood reaches the lungs the low pCO2 causes some go the HCO3- and H+ ions to recombine into CO2 The CO2 then diffuses into the alveoli and is breathed out (j) the oxygen dissociation curve for foetal and adult human haemoglobin. Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin Adult haemoglobin and foetal haemoglobin have different affinities for oxygen. Foetal haemoglobin has a higher affinity for oxygen (the foetus’ blood is better at absorbing oxygen than its mother’s blood) at the same partial pressure of oxygen. 1) The foetus gets oxygen from its mother’s blood across the placenta 2) By the time the mother’s blood reaches the placenta, its oxygen saturation has decreased (because some has been used by the mothers body) 3) For the foetus to get enough oxygen to survive its haemoglobin has to have a higher affinity for oxygen. 4) If its haemoglobin had the same affinity for oxygen as adult haemoglobin its blood wouldn't be saturated....