Chapter 9 Homeostasis and Circulation

Transcription

1 1 Chapter 9 Homeostasis and Circulation Section 9.1 Homeostasis: Life in the Balance Outcomes: I can explain homeostasis I can describe the importance of homeostasis to living things I can explain the importance of constant temperature to maintain homeostasis - Homeostasis the ability of the body to maintain a consistent internal environment. - The internal systems help to maintain homeostasis in the body. - The stability achieved by the homeostatic mechanisms is called dynamic equilibrium. - Dynamic equilibrium to maintain a state of balance within an environment that is continually exposed to outside forces that tend to change that environment Temperature Regulation - is one of the body s homeostatic mechanisms - Animals may incorporate behaviors to control temperature (flying south in winter) - Physiological mechanisms are also used (involves one/some of the internal body systems such as the circulatory system) - Body temperature of a human is roughly 37.5 C - Your body can regulate heat loss many ways: *behavioral mechanisms - putting a blanket on when you are cold *physiological mechanisms - circulatory system - The circulatory system plays an important role in regulating body temperature: - If heat needs to be conserved, blood vessels close to the skin will constrict (vasoconstriction) to limit blood flow. The extremities may become cold. - If heat needs to be released, blood vessels will dilate (vasodilatation) to increase blood flow under the surface of the skin. The skin may feel hot to touch. Section 9.2 The Circulatory System Outcomes: I can explain how the circulatory system helps maintain homeostasis - The need for a transport system - Identifying the main components of blood - Identifying the main components of the heart and their functions - The pathway of blood through the heart, pulmonary, and systemic pathways I can identify the impact of circulatory diseases on the homeostasis of an organism Circulatory System - The circulatory system acts as a link between the cells of a complex organism and its environment - Three parts: Transport Vessels - a network of tubes through which the fluid flows Blood - a fluid in which materials are transported Heart - a pumping mechanism

2 2 The Transport Vessels - Arteries - Veins - Capillaries Blood the transport medium (fluid) made up of different types of cells and plasma Blood Cells Erythrocytes (Red blood cells) - Mature red blood cells have no nucleus - Specialized for O 2 and CO 2 transport. - Contains iron - Life cycle ~ 120 days Leukocytes (White blood cells) - Have nucleus, appear colorless - Main function is to fight infection. Leukocyte numbers increase when the body is fighting infection. Main types: *Macrophages found abundantly in filter tissues (spleen, kidney etc). They pass through capillary walls and engulf/digest pathogens *Lymphocytes recognize and fend off specific pathogens the body has been exposed to before - Life cycle can be hours to years depending on the type of cell. Platelets - The most abundant cell in the blood - Actually fragments of cells created in the bone marrow - No nucleus and live about 7-10 days - Main function is aid in blood clotting Plasma - A straw-coloured liquid that carries the blood cells and the platelets. - Helps transport important substances such as: carbon dioxide, glucose, amino acids, proteins, minerals, vitamins, hormones, waste materials like urea Section 9.3 The Mammalian Heart Heart (The Pump) - Found slightly to the left of the middle of the chest cavity and is the size of two fists - Made of cardiac muscle - The pericardium is a tough membrane that surrounds the heart and protects it - Acts as a double pump as it contracts and forces blood through the vessels - Right side of the heart sends oxygen-poor blood to the lungs and the left side sends oxygen-rich blood to the rest of the body - The pumping action is divided into systole period of contraction and diastole period of relaxation.

3 3 Structure of the Heart: Four chambers - Left atrium and right atrium: thin walled - Left ventricle and right ventricle: thick walled - Left and right sides of the heart are separated by a wall called the septum which prevents nonoxygenated blood and oxygenated blood from mixing. Four flap-like valves - Control the direction of blood flow inside the heart and allow it to only flow one way - Atrioventricular valves (AV valves) allow blood to flow from the atria to the ventricles Right side - tricuspid valve has 3 flaps Left side - bicuspid valve (mitral valve) has 2 flaps - Semilunar valves allow blood to move from the ventricles into the arteries that carry blood away from the heart. They also stop the blood from flowing back into the ventricles. Right side - pulmonary valve Left side - aortic valve Control of the Heartbeat - Cardiac muscle has a built-in ability to contract - Even when it is removed from the body, the heart will keep beating for a while if it is kept in a special solution - Sinoatrial node (SA node) is our pacemaker. It is a small group of specialized muscle cells in the wall of the right atrium Contraction of the heart 1. Contraction of the heart begins when the atria receive electrical impulses from the sinoatrial node (SA node) ~ pace maker 2. As the atria contract, the impulse moves from the SA node to the atrioventricular node (AV node) which is located near the atria on the partition between the two ventricles. The impulse moves from the AV node slowly to allow time for the atrium to contract and release blood into the ventricles. 3. The impulse moves into the atrioventricular bundle (His Bundle) which splits into 2 atricoventricular branches (Bundle Branches) 4. The impulse moves down each bundle branch and enter each ventricle by Purkinje fibres.

4 4 An electrocardiogram (ECG) can record each time the heart contracts by placing electrodes on the chest. The rate of the heartbeat is regulated by certain nerves that enter the pacemaker. The rhythm is affected by the changes in body temperature and by certain chemicals or hormones (ex: adrenaline or a drug overdose) The rate of the heartbeat is determined by chemical regulators (CO 2, noradrenaline) in the blood stimulating the nerves entering the pacemaker; Vagus nerves slow down the pacemaker Cardioaccelerator nerves speed up the pacemaker Two Major Pathways of Human Circulation - Arteries move oxygenated blood away from the heart - Arteriole is a small thin walled blood vessel that extends and branches out from an artery and leads to capillaries. - Veins move deoxygenated blood toward the heart - Venule is a smaller blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins There are 2 main branches of circulation: pulmonary, and systemic. 1. Pulmonary Circulation - Carries blood between heart and lungs - Adds oxygen to the blood and removes carbon dioxide - The pulmonary arteries are the ONLY arteries that carry deoxygenated blood. They take blood from the right ventricle to the lungs to get oxygenated. - The pulmonary veins are the ONLY veins that carry oxygenated blood. They take oxygen rich blood from the lungs back to the heart and into the left atrium. 2. Systemic Circulation - Carries blood between the heart and the rest of the body - From the left ventricle, the blood is pumped into the Aorta (largest artery in the body) - The aorta branches off into arteries to serve all parts of the body - Exchange of materials between blood and body tissues takes place through the walls of capillaries - Capillaries merge to form veins. - The two largest veins in your body are: Superior vena cava - Carries deoxygenated blood from the head /upper body back to the right atrium Inferior vena cava Carries deoxygenated blood from the legs/lower body back to the right atrium.

5 5 Blood Flow Through the Heart 1. Deoxygenated blood from the superior vena cava and inferior vena cava enter the right atrium. 2. The right atrium releases blood through the tricuspid valve into the right ventricle. 3. The right ventricle pushes the blood through the pulmonary valve into the pulmonary arteries 4. The pulmonary arteries take the blood to the left and right lungs 5. In the lungs the blood flows through capillaries which allow for oxygen to enter the blood, and release carbon dioxide through the thin walled alveoli 6. The now oxygen rich blood flows from each lung back to the heart via two sets of pulmonary veins. 7. These veins enter the left atrium 8. The left atrium empties blood through the mitral valve (biscupid valve) to the left ventricle 9. The left ventricle pushes the oxygen rich blood through the aortic valve to the aorta 10. The aorta branches into many arteries which carry the oxygenated blood to all parts of the body Section 9.4 Transport Systems and Homeostasis Pulse - the expansion (high pressure) and relaxation (low pressure) that can be felt in an artery each time the left ventricle contracts and relaxes - Both the rate and the force of the heartbeat can be measured by the pulse Blood Pressure - Measured with an instrument called a sphygmomanometer - Stated in the form of systolic pressure/diastolic pressure - Normal blood pressure is considered 120/80 - During exercise or times of stress, blood pressure increases Anemia lack of iron in the blood, low RBC count Hemophilia bleeders disease, lack of clotting factor Circulatory Disorders Hypertension Chronic high blood pressure caused by: Diet high in salt (causes blood to retain more H2O) Diet high in cholesterol (clogs arteries making blood passage difficult) Regular use of artificial stimulants (caffeine, nicotine)

6 6 Atherosclerosis Narrowing of arteries due to plaque deposits (from cholesterol) ON the artery walls. Can occur in combination with hypertension Reduces blood flow to the heart muscle and lead to heart attack Arteriosclerosis Cholesterol or other fatty material deposited UNDER the lining of the artery wall Plaque blocks blood flow, can cause blood clots which may break free, travel and cause heart attack or stroke. *Hypertension, atherosclerosis and arteriosclerosis can ultimately lead to a heart attack where the blood vessels around the heart become blocked.* Medical Procedures/Treatments Patients with a risk of blood clots may be prescribed Asprin (to thin blood) or other prescriptions drugs that break down the clot or causes the heart contractions to intensify. Sometimes surgical procedures, such as coronary bypass or angioplasty, are necessary Coronary Bypass Angioplasty Involves removing a section of a healthy artery somewhere in the body and using it to create a new pathway for blood to flow. One end of the new segment is attached to the aorta and the other to the blood vessel beyond the blockage. Double, triple and quadruple refer to the number of vessels that require a new pathway. A surgeon inserts a fine plastic tube into a clogged artery up to the area that is restricted. A tiny balloon is pushed out the tip of the tube, inflated and forcing the vessel opened.

7 7 Lymphatic Circulation - Network of glands and vessels throughout your body - Contains a fluid called lymph - Helps maintain the balance of fluids in the body - Works with white blood cells to help guard against infection - Does not use a pump to circulate in the body - Muscles in the area of the intestines and the breathing muscles help the fluid move. - Parts of the Lymphatic System: Spleen creates & stores lymphocytes and aids in destroying old red blood cells Thymus gland Make special lymphocytes called T cells which also help with immunity Tonsils Made of lymph tissue, destroy and trap bacteria from further entering the body Peyer s Patches - Destroy bacteria, preventing them from reaching the wall of the small intestine and entering the bloodstream. - Generate memory lymphocytes for long term immunity