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 What’s your weight in kg? (lbs x 0.45) What’s your heart rate? 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 BP = Systolic/Diastolic BP = 120/80 (Normal) Systolic = pressure in arteries Diastolic = pressure in veins BP = Systolic/Diastolic BP = 120/80 (Normal)

Question 2 True or False. Pressure increases as blood flows away from the heart.

Blood Pressure Depends on: Cardiac output (as cardiac output increases, blood pressure increases and vice versa) 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 Nerve transmits signals to medulla oblongata Vagus nerve transmits inhibitory signal to sinoatrial node Heart rate decreases Baroreceptors sense increased blood pressure

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? Blood vessels dilate and shivering Blood vessels constrict and shivering Blood vessels dilate and sweating 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 vessels in skin Body hairs become erect (goosebumps) Hypothalamus initiates shivering Heat is conserved More head is generated by increased metabolism (skeletal 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

Lymphoid Organs 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? Return leaked protein to the circulatory system Houses white blood cells Transports lymph into open-ended lymph vessels 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! Sympathetic nerves stimulate the adrenal glands which release epinephrine/adrenaline Epinephrine travels through the blood and stimulates the release of red blood cells from the spleen Increased numbers of red blood cells aid in oxygen delivery 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.