Grade 9 Biology - Circulation in Animals Notes PDF

**[Grade 9 ]** **[Biology]** **[Trans in animals notes1]** **Circulation in Different Animals** - Fish have a **two-chambered heart** and a **single circulation** - This means that **for every one circuit of the body, the blood passes through the heart once** - The single circulatory...

**[Grade 9 ]** **[Biology]** **[Trans in animals notes1]** **Circulation in Different Animals** - Fish have a **two-chambered heart** and a **single circulation** - This means that **for every one circuit of the body, the blood passes through the heart once** - The single circulatory system in fish Mammals have a four-chambered heart and a double circulation This means that for every one circuit of the body, the blood passes through the heart twice The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (the pulmonary circulation) The left side of the heart receives oxygenated blood from the lungs and pumps it to the body (the systemic circulation) ### Advantages of a Double Circulation - Blood travelling through the small capillaries in the lungs **loses a lot of pressure** that was given to it by the pumping of the heart, meaning it **cannot travel as fast** - By returning the blood to the heart after going through the lungs its **pressure can be raised again** before sending it to the body, meaning **cells** can be supplied with the **oxygen and glucose** they need for respiration **faster and more frequently** Structure of the heart external - Hollow, pear shape muscle about the size of a clenched fist - Its surrounded by a tough membrane called the pericardium - On the surface of the heart is an artery, the coronary artery that supplies the heart muscles with oxygenated blood - The position of the heart is between the lungs in the thorax called the mediastinum - Structure of the heart internal - The heart consists of 4 chambers, 2 atria on top and 2 ventricles at the bottom - The heart is divided into a left and right side by a muscular wall the septum. The left side receives oxygenated blood and the right side deoxygenated blood - The septum prevents blood from mixing - The atria are the receiving chambers and the ventricles the pumping chambers - Because the ventricles pump the blood they have thicker muscular walls - The left ventricle has the thickest muscular wall of all 4 chambers because it pumps blood under high pressure to the rest of the body - Between the atria and ventricles are valves that ensure one way flow of blood  **[Grade 9]** **[Biology]** **[Trans in animals notes2]** ### Heart Structure - The **ventricles** have thicker muscle walls than the atria as they are pumping blood out of the heart and so need to generate **a higher pressure** - **The left ventricle has a thicker muscle wall than the right ventricle** as it has to pump blood at high pressure around the **entire body**, whereas the right ventricle is pumping blood at lower pressure to the **lungs** - The **septum** separates the two sides of the heart and so **prevents mixing of oxygenated and deoxygenated blood**  ### The Function of Valves - The basic function of all valves is to **prevent blood flowing backwards** - There are two sets of valves in the heart: - The **atrioventricular valves** separate the atria from the ventricles - The valve in the right side of the heart is called the **TRICUSPID** and the valve in the left side is called the **BICUSPID** - These valves are pushed **open when the atria contract** but when the **ventricles contract they are pushed shut** to prevent blood flowing back into the atria - The **semilunar valves** are found in the two blood arteries that come out of the top of the heart - They are unusual in that they are the **only two arteries in the body that contain valves** - These valves **open when the ventricles contract** so blood squeezes past them out of the heart, but then shut to avoid blood flowing back into the heart **Functioning of the heart (cardiac cycle) / Pathway of blood through the heart** - **Deoxygenated blood** coming from the body flows into the **right atrium** via the **vena cava** - Once the right atrium has filled with blood the heart gives a little beat and the blood is pushed through the **tricuspid (atrioventricular) valve** into the **right ventricle** - The walls of the ventricle **contract** and the blood is pushed into the **pulmonary artery** through the **semilunar valve** which prevents blood flowing backwards into the heart - The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place (this is why there has to be low pressure on this side of the heart -- blood is going directly to capillaries which would burst under higher pressure) - **Oxygen-rich blood** returns to the **left atrium** via the **pulmonary vein** - It passes through the **bicuspid (atrioventricular) valve** into the **left ventricle** - The thicker muscle walls of the ventricle contract strongly to push the blood forcefully into the **aorta** and all the way around the body - The **semilunar valve** in the aorta prevents the blood flowing back down into the heart Heart Disease & Exercise ======================== ### Exercise & Heart Rate - Heart activity can be monitored by using an **ECG**, measuring **pulse rate** or **listening to the sounds of valves closing** using a stethoscope - Heart rate (and pulse rate) is measured in beats per minute (bpm) - To investigate the effects of exercise on heart rate, record the pulse rate at rest for a minute - Immediately after they do some exercise, record the pulse rate every minute until it returns to the resting rate - This experiment will show that during exercise the heart rate increases and may take several minutes to return to normal **Extended Only** ### Why does Heart Rate Increase during Exercise? - So that **sufficient blood** is taken to the working muscles to provide them with enough **nutrients and oxygen** for **increased respiration** - An increase in heart rate also allows for **waste products to be removed at a faster rate** - Following exercise, the heart continues to beat faster for a while to ensure that **all excess waste products are removed** from muscle cells - It is also likely that muscle cells have been respiring **anaerobically** during exercise and so have built up an **oxygen debt** - This needs to be 'repaid' following exercise and so the heart continues to beat faster to ensure that **extra oxygen is still being delivered to muscle cells** - The extra oxygen is used to break down the **lactic acid** that has been built up in cells as a result of anaerobic respiration ### Coronary Heart Disease The coronary arteries, IGCSE & GCSE Biology revision notes - The heart is made of **muscle cells** that need their own supply of blood to deliver oxygen, glucose and other nutrients and remove carbon dioxide and other waste products - The blood is supplied by the **coronary arteries** - If a coronary artery becomes partially or completely **blocked by fatty deposits called 'plaques'** (mainly formed from **cholesterol**), the arteries are not as **elastic** as they should be and therefore cannot stretch to accommodate the blood which is being forced through them -- leading to **coronary heart disease** - **Partial blockage** of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called **angina** - **Complete blockage** means cells in that area of the heart will not be able to respire and can no longer contract, leading to a **heart attack**  ***Buildup of plaque in the coronary arteries*** Effect of narrowing of arteries, IGCSE & GCSE Biology revision notes Extended  **Extended Only** ### Prevention & Treatment **Reducing the risks of developing coronary heart disease** - **Quit smoking** - **Reduce animal fats** in diet and eat more fruits and vegetables -- this will reduce cholesterol levels in the blood and help with weight loss if overweight - **Exercise regularly** -- again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress **Treatment of coronary heart disease** - **Aspirin** can be taken daily to **reduce the risk of blood clots** forming in arteries - Surgical treatments include: 1. **Angioplasty** - - A narrow catheter (tube) is threaded through the groin up to the blocked vessel - A tiny balloon inserted into the catheter is pushed up to the blocked vessel and then inflated - This flattens the plaque against the wall of the artery, clearing the blockage - To keep the artery clear, **a stent** (piece of metal / plastic mesh) is also inserted which pushes against the wall of the artery - Sometimes the stent is coated with a drug that slowly releases medication to prevent further build-up of plaque Inserting a stent into a blocked artery, IGCSE & GCSE Biology revision notes ***Inserting a stent into a blocked artery*** **2) Coronary bypass surgery** - A piece of blood vessel is taken from the patient's leg, arm, or chest and used to **create a new passage for the flow of blood** to the cardiac muscle, bypassing the blocked area - The number of bypass grafts gives rise to the name of the surgery, so a 'triple heart bypass' would mean three new bypass grafts being attached  ***Coronary bypass graft*** **[Grade 9]** **[Biology]** **[Trans in animals notes 3]** Blood Vessels ============= ### Arteries, Veins & Capillaries **Arteries** - Carry blood at **high pressure away from the heart** - Carry **oxygenated** blood (other than the pulmonary artery) - Have **thick muscular walls** containing elastic fibres - Have a **narrow lumen** - Speed of flow is **fast** **Veins** - Carry blood at **low pressure towards the heart** - Carry **deoxygenated** blood (other than the pulmonary vein) - Have **thin **walls - Have a **large lumen** - Contain **valves** - Speed of flow is **slow** Comparing arteries and veins, IGCSE & GCSE Biology revision notes***Comparing arteries and veins*** Capillaries - Carry blood at **low pressure** within tissues - Carry **both oxygenated and deoxygenated blood** - Have walls that are **one cell thick** - Have 'leaky' walls - Speed of flow is **slow**   Structure of a capillary, IGCSE & GCSE Biology revision notes ***Structure of a capillary*** Extended Only ### How Structure of Blood Vessels is Adapted to their Function **Arteries** - Have thick muscular walls containing elastic fibres **to withstand high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through** - Have a narrow lumen **to maintain high pressure** **Veins** - Have a large lumen **as blood pressure is low** - Contain valves **to prevent the backflow of blood as it is under low pressure** **Capillaries** - Have walls that are one cell thick **so that substances can easily diffuse in and out of them** - Have 'leaky' walls **so that blood plasma can leak out and form tissue fluid surrounding cells** Extended Only ### Arterioles & Venules - As arteries **divide more** as they get further away from the heart, they get **narrower** - The narrow vessels that connect arteries to capillaries are called **arterioles** - Veins also get narrower the further away they are from the heart - The narrow vessels that connect capillaries to veins are called **venules**  ***blood vessel network*** Extended Only ### Shunt Vessels - Sometimes the **cardiovascular system needs to redistribute the blood** to specific areas of the body - For example: - **During exercise**, more of it goes to the working muscles and less of it goes to other body organs such as the digestive system - **When we are hot**, more blood flows through the surface of the skin and when we are cold less blood flows through the surface of the skin - This redirection of blood flow is caused by the use of a **vascular shunt vessel** - The shunt vessels can open or close **to control the amount of blood flowing** to a specific area   A shunt vessel in the skin when we are cold, IGCSE & GCSE Biology revision notes ***A shunt vessel in the skin when we are cold***  ***A shunt vessel in the skin when we are hot*** ### Circulation Around the Body & Important Blood Vessels - Blood is carried **away from the heart** and towards organs in **arteries** - These narrow to arterioles and then capillaries as they pass through the organ - The capillaries widen to venules and finally veins as they move away from the organs - **Veins** carry blood back **towards the heart** The circulatory system, IGCSE & GCSE Biology revision notes ***The circulatory system*** **Important blood vessels:**  The Lymphatic System ==================== Extended Only ### Lymph Fluid - The walls of the capillaries are so thin that water, dissolved solutes and dissolved gases easily leak out of them / pass through the walls from the plasma into the **tissue fluid** surrounding the cells - Cells **exchange materials** (such as water, oxygen, glucose, carbon dioxide, mineral ions) **across their cell membranes** with the tissue fluid surrounding them by diffusion, osmosis or active transport - More fluid leaks out of the capillaries than is returned to them, and this excess of leaked fluid surrounding the capillaries then passes into the lymphatic system, becoming **lymph fluid**   How lymph forms, IGCSE & GCSE Biology revision notes***How lymph forms*** Extended Only ### Lymph Vessels & Nodes - The lymphatic system is formed from a **series of tubes which flow from tissues back to the heart** - It connects with the blood system near to the heart, where lymph fluid is **returned** to the blood plasma - **Lymph nodes** are small clusters of lymphatic tissue found throughout the lymphatic system, especially in the neck and armpits - Large numbers of **lymphocytes** are found in lymph nodes - Tissues associated with the lymphatic system, such as bone marrow, produce these **lymphocytes** - Lymphocytes play an important role in **defending the body against infection**  Blood ====== ### Components of Blood - Blood consists of **red blood cells, white blood cells, platelets and plasma**   ***Composition of human blood*** Components of the blood: Blood table, IGCSE & GCSE Biology revision notes    ***Blood micrograph*** Extended Only ### Types of White Blood Cell - White blood cells are part of the body's **immune system**, defending against infection by pathogenic microorganisms - There are two main types, **phagocytes and lymphocytes** **Phagocytes** - Carry out **phagocytosis** by **engulfing and digesting pathogens** Phagocytosis, IGCSE & GCSE Biology revision notes***Phagocytosis*** - Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells - Once they encounter the pathogenic cell, they will engulf it and **release digestive enzymes** to digest it - They can be easily recognised under the microscope by their **multi-lobed nucleus** and their **granular cytoplasm** **Lymphocytes** - Produce **antibodies** to destroy pathogenic cells and **antitoxins** to neutralise toxins released by pathogens - They can easily be recognised under the microscope by their **large round nucleus** which takes up nearly the whole cell and their **clear, non-granular cytoplasm** ### Functions of the Parts of the Blood - **Plasma** is important for the transport of **carbon dioxide, digested food (nutrients), urea, mineral ions, hormones and heat energy** - **Red blood cells transport oxygen around the body** from the lungs to cells which require it for aerobic respiration - They carry the oxygen in the form of **oxyhaemoglobin** - **White blood cells** defend the body against infection by pathogens by carrying out **phagocytosis and antibody production** - **Platelets** are involved in **helping the blood to clot** Extended Only ### Blood Clotting - Platelets are **fragments of cells which are involved in blood clotting** and forming scabs where skin has been cut or punctured - Blood clotting **prevents continued / significant blood loss** from wounds - Scab formation seals the wound with an insoluble patch that **prevents entry of microorganisms** that could cause infection - It remains in place until new skin has grown underneath it, sealing the skin again  ***How the blood clots*** - When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding - A series of reactions occur within the blood plasma - Platelets release chemicals that cause **soluble fibrinogen proteins** to convert into **insoluble fibrin** and form an **insoluble mesh** across the wound, trapping red blood cells and therefore **forming a clot** - The clot eventually dries and develops into a **scab** to protect the wound from bacteria entering