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REGULATION OF BLOOD FLOW Biology 20 – Unit D: Human Systems Section 10.3 (pg. 328-335) Cardiac Output • Cardiac Output: The amount of blood that flows (is pumped) from the heart each minute • Amount of blood pumped from right side = amount of blood pumped from left side Stroke Volume • Stroke Volume: The quantity of blood pumped with each beat of the heart = ~70 mL/beat (resting) Cardiac Output = Stroke Volume x Heart Rate Cardiac Output = 70 mL/beat x 70 beats/min Cardiac Output = 4900 mL/min Cardiac Output Calculation 1. What’s your weight in kg? (lbs x 0.45) 2. What’s your heart rate? 3. Come up and tell me Question 1 What is Cardiac Output? (a) volume of blood that is pumped with each heart beat (b) volume of blood that is pumped by the heart each minute (c) The number of times the heart contracts per minute (d) The number of times the sinoatrial node stimulates the heart Blood Pressure • The force of the blood on the walls of the arteries • Measured by a sphygmomanometer • Gauge measures the pressure exerted by the blood during ventricular contraction • Bladder increases until a low-pitched sound can be detected – systolic blood pressure • Bladder is deflated even more until sound disappears – ventricular relaxation – diastolic blood pressure Blood Pressure • Measured in mmHg (mm of Mercury) • Systolic pressure/Diastolic pressure = Pressure in Arteries/pressure in Veins • Normal = 90/60 – 140/90; Average = 120/80 • Example of High Blood pressure = 160/100 • Hypertensive • Example of Low Blood pressure = 80/50 • Hypotensive Blood Pressure • Systolic = pressure in arteries • BP = Systolic/Diastolic • Diastolic = pressure in veins • BP = 120/80 (Normal) Question 2 True or False. Pressure increases as blood flows away from the heart. Blood Pressure • Depends on: 1. Cardiac output (as cardiac output increases, blood pressure increases and vice versa) 2. Arteriolar resistance (diameter of arteriole is regulated by smooth muscle) • Constriction closes the opening - reduces blood flow through the arteriole and increases blood pressure = vasoconstriction • Arteriole dilation increases blood flow and decreases blood pressure = vasodilation • Responds to neural and hormonal controls Blood Vessel Regulation • Diameter of arterioles adjusts in response to metabolic products such as • Glucose by-products (in the break down of glucose) • Carbon dioxide • Lactic acid • Causes relaxation of arterioles dilation blood flow (increase of oxygen) increases • How the body maintains equilibrium Hypertension • High blood pressure • Increased resistance to blood flow • Could cause vessels to weaken and rupture • Body increases the amount of connective tissue – leading to hardened/less elastic arteries. • Diet is mainly responsible • E.g. too much salt higher blood pressure • Heart Attack/Stroke! Hypotension • Low blood pressure • Reduces your capacity to transport blood and oxygen • Adjusted by the sympathetic nerves Blood Vessel Regulation • Vasoconstriction: the narrowing of blood vessels/arterioles (less blood to tissues) • Increases blood pressure • Caused by a nerve impulse that contracts smooth muscle • Less O2 to tissues • Vasodilation: the widening of blood vessel/arterioles (more blood to tissues) • Decreases blood pressure • Relaxation of smooth muscle • Helps you release excess heat Blood Pressure Regulation • Autonomic nervous system (controls motor nerves that regulates the diameter of arterioles; unconscious/involuntary) – medulla oblongata in the brain • Parasympathetic – decelerates heart beat • Sympathetic – accelerates heart beat Question 3 A blood pressure regulator in the brain is called the _____________ ______________. (don’t worry about spelling) Blood Pressure Regulation • Blood pressure receptors are called baroreceptors are located in the aorta and the carotid artery Baroreceptors sense increased blood pressure Heart rate decreases Nerve transmits signals to medulla oblongata Vagus nerve transmits inhibitory signal to sinoatrial node What happens when blood pressure drops…? Nervous System Parasympathetic Sympathetic Blood Vessels/Arterioles Dilate (widen) constrict (narrow) Blood Pressure Decreases Increases Cardiac Output Increases Decreases Question 4 • When a someone becomes hypertensive, the body tries to regulate itself by • Stimulating the ________________ nervous system • Causing arterioles to ________________ • Which ______________ blood pressure • And _____________ their cardiac output. Regulating Body Temperature • Thermoregulation: maintenance of body temperature within a range that enables cells to function efficiently • Consider the exchange of heat between the body and the environment What is normal body temperature? Question 5 Which of the following regulates a body that has become too hot? (a) Blood vessels dilate and shivering (b) Blood vessels constrict and shivering (c) Blood vessels dilate and sweating (d) Blood vessels constrict and sweating Thermoregulation • Hypothalamus: a region of the brain that is responsible for coordinating many nerve and hormone functions Stimulus Physiological Response Result Decreased Environmental Temperature • Constriction of blood • Heat is conserved vessels in skin • More head is • Body hairs become generated by erect (goosebumps) increased • Hypothalamus metabolism (skeletal initiates shivering muscle movement) Increased Environmental Temperature • Dilation of blood vessels • Sweating • Heat is dissipated Capillary Fluid Exchange • Every tissue is within 0.1mm of a capillary • Capillaries provide cells with oxygen, glucose, and amino acids • Fluid exchange between the blood and the surrounding extracellular fluid • Water passes through spaces between the capillary cells • Fluid & Osmotic pressure influence water movement • Water moves from an area of higher pressure to an area of lower pressure Precapillary Sphincters Capillary Fluid Exchange Question 6 When fluid pressure outside of a capillary is greater than the fluid pressure inside a capillary, the water moves (a) into the capillary (b) out of the capillary (c) along side the capillary (d) nowhere The Lymphatic System • Lymph: the fluid found in lymph vessels that contains some proteins that have leaked through capillary walls • Leaked proteins drain from the extracellular fluid (ECF) and return to the circulatory system by way of the lymphatic system • Lymph is transported in open-ended lymph vessels (similar to veins) • Low pressure return system uses muscle contractions • Lymph is returned to the venous system Lymph Nodes • Are enlargements that house white blood cells that filter out any bacteria • Filter damaged cells and debris from the lymph and store lymphocytes • Red bone marrow is where all types of blood cells are produced • White blood cells • Spleen – has many blood sinuses (each hold ~150mL blood) – reservoir Lymphoid Organs Question 7 Which of the following does the lymphatic system NOT do? (a) Return leaked protein to the circulatory system (b) Houses white blood cells (c) Transports lymph into open-ended lymph vessels (d) Transports oxygen and carbon dioxide Edema (a.k.a. Swelling) Results when small blood vessels become leaky and release fluid into tissues. The fluid accumulates causing tissues to swell. Response of the Circulatory System to Exercise • Go for a run! • Oh no! Lactic acid buildup in your calf! 1. Sympathetic nerves stimulate the adrenal glands which release epinephrine/adrenaline 2. Epinephrine travels through the blood and stimulates the release of red blood cells from the spleen 3. Increased numbers of red blood cells aid in oxygen delivery 4. Epinephrine and stimulation from sympathetic nerves increases heart and breathing rates higher levels of blood and faster oxygen transport & wastes are removed! Summary • Cardiac output is the amount of blood the heart can pump each minute • Blood pressure is the force of blood on the walls of the arteries. It is measured as systolic and diastolic blood pressure in millimetres of mercury (mmHg) • Blood pressure is higher in vessels closer to the heart • Increased cardiac output increases blood pressure. If arteries are constricted, blood flow is slower and blood pressure is higher Summary • Capillaries are associated with fluid exchange between blood and extracellular fluid • The movement of water between blood and the ECF is regulated by fluid pressure and by osmotic pressure • Water moves from an area of high fluid pressure, the capillary, to an area of low fluid pressure, the ECF • Proteins and dissolved minerals in the blood cause fluid from the ECF to move into the blood by osmosis Summary • Proteins in the ECF are returned to the circulatory system by the lymphatic system • Lymph nodes house white blood cells that filter bacteria • Red bone marrow is where all types of blood cells are produced • The spleen stores and purifies blood. The spleen releases red blood cells in response to low blood pressure or low oxygen levels in blood.