Week2AnatomyNotes.pdf BIOL 2020-002
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This 10 page Class Notes was uploaded by Paige Fairrow-Davis on Monday February 8, 2016. The Class Notes belongs to BIOL 2020-002 at Middle Tennessee State University taught by Dr. Vincent Cobb in Winter 2016. Since its upload, it has received 50 views. For similar materials see Human Anatomy & Physiology II in Biology at Middle Tennessee State University.
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Date Created: 02/08/16
Week 2 Anatomy Notes I. Depolarization of SA Node A. The SA Node has no stable resting membrane potential B. The cells of the SA node have a starting membrane potential of about -60 mV. 1. This number gradually shifts upward (gradually depolarizing) a. This gradual depolarization is called Pacemaker potential i. Pacemaker potential is the result of 2 reasons ▯ Slow inflow of Na + ▯ Leaky K channels C. Action Potential 1. Depolarization a. Have a threshold of -40mV. b. Upon reaching threshold, Ca channels open c. Calcium flows in 2. Repolarization a. Begins at 0mV and stops around -60 b. K channels open c. Potassium leaves the cell 3. Each depolarization= 1 heartbeat 4. At rest, the SA node fires every .8 seconds, creating about 75 beats per minute. II. Impulse Conduction to the Myocardium A. SA node signal to AV Node 1. Takes .04 seconds 2. Travels at a speed of about 1 meter per second B. Signal at the AV Node 1. Slows down to about .05 meters per second a. This is due to the thin myocytes of the AV node 2. This delays the signal for about .11 seconds a. The delay is what allows the ventricle to fill C. AV Bundle to Purkinje Fibers 1. The signal speeds up here to about 4 meters per second taking about .05 seconds D. Papillary Muscles 1. Get the signal next 2. This allows the AV valves to stabilize E. Ventricular Systole 1. This begins at the Apex and progresses upward 2. Here, there is a spiral arrangement of myocytes that twist the ventricles slightly III. Myocardial Contraction and Action Potential 1. Na Channels open 2. Positive Feedback Cycle a. A rapid rise in membrane voltage due to the opening of the Na that cause other sodium channels to open as well + 3. Na channels close 4. A FEW K channels open and slow Ca gates open 5. Ca channels close and K open IV. Electrocardiogram (ECG) A. Composite of all action potentials of nodal and myocardial cells detected, amplified, and recorded by electrodes on body surface P Wave: SA Node fires Atrial depolarization occurs Atrial systole begins QRS Complex Atrial repolarization Atrial diastole occurs AV Node fires Ventricular depolarization Ventricular Systole T Wave Ventricular repolarization V. Cardiac Cycle A. Blood moves through the circulatory system from areas of higher pressure to areas of low pressure 1. Contraction of the heart creates the pressure B. Steps of the Cycle 1. Systole: Period of isovolumic contraction a. Both semilunar valves and AV valves are closed b. Ventricles put pressure on fluid c. No blood ejected and volume remains constant 2. Systole: Period of Ejection a. Only Semilunar valves open 3. Diastole: Period of isovolumic relaxation a. Both Valves close again b. Ventricles open up 4. Diastole: Passive ventricular filling a. Only the AV valves open 5. Diastole: Active ventricular filling a. AV vales remain the only valves open VI. Heart Sounds A. Auscultation 1. Listening to sound made by the body B. Heart makes two sounds 1. First sound a. Louder than the second b. Symbolized as S1 c. Comes with the closure of the AV valves 2. Second Sound a. Much softer and sharper b. Characterized as S2 c. Occurs with closure of semilunar valves C. Occasionally makes a third sound 1. Normal to hear in children 2. When heard in people over 30, can symbolize a larger and failing heart 3. Caused by turbulent blood flow into ventricles 4. Detected near the end of diastole: period of isovolumic relaxation VII. Overview of Volume Changes A. End-systolic Volume (ESV) 60 mL Passively added to ventricle during atrial diastole 30 mL Added by atrial Systole 40 mL Total: End-diastolic Volume (EDV) 130 mL Stroke Volume (SV) ejected by -70 mL Ventricular systole End Systolic volume 60 mL VIII. Unbalanced Ventricular Output A. Respiratory distress 1. Right Ventricular output exceeds Left Ventricular Output 2. Pressure Backs up 3. Fluid accumulates in pulmonary tissue B. Edema Ascites 1. Left Ventricular output exceeds right ventricular output 2. Pressure backs up 3. Fluid accumulates in systemic tissue IX. Cardiac Output (CO) A. Defined as the volume of blood ejected by a ventricle per some unit of time B. CO (measured in ml/min) 1. = HR (beats per minute) x SV (stroke volume) (ml/beat) C. Resting Values 1. 75 beats/min x 70 mL/beat = 5250 ml/min = CO a. = 4 to 6 L/min D. Vigorous exercise increases CO 1. 21 L/min for a fit person 2. 35 L/min for a world class athlete E. Cardiac Reserve 1. Difference between maximum and resting CO X. Heart Rate A. Measured from Pulse B. Infants have a heart rate of 120 beats/min or more C. Young adult female 1. Avg. 72-80 bpm D. Young adult male 1. Avg. 64-72 bpm E. Heart Rate rises again in the elderly F. Tachycardia 1. Persistent, resting adult heart rate of >100 bpm 2. Can be caused by stress, anxiety, drugs, heart disease, or an increase in body temperature G. Bradycardia 1. Persistent, resting adult HR <60 2. Common in sleep and endurance trained athletes a. Common in Athletes because of their increased stroke volume XI. Regulation of the Heart A. Intrinsic Regulation 1. Results from normal functional characteristics, not on neural or hormonal regulation 2. Sterling’s law of the heart a. The ventricles eject as much as much blood as they receive B. Extrinsic regulation 1. Involves neural and hormonal control 2. Parasympathetic Stimulation a. Supplied by the vagus nerve b. Decreases heart rate c. Acetylcholine secreted 3. Sympathetic Stimulation a. Supplied by the cardiac nerve b. Increases heart rate and force of contraction c. Epinephrine and mostly norepinephrine used 4. Specific effects of the Nervous System a. m Sympathetic postganglionic fibers release norepinephrine Norepinephrine binds to Beta-adrenergic fibers in the heart This activate the cAMP system which then binds to an enzyme that opens the Ca channels in the membrane Ca inflow accelerates depolarization of the SA node, which increases heart rate XII. Stroke Volume A. Preload 1. Defined as the amount of tension in the ventricular myocardium before it contracts 2. An increase in preload causes an increase in contraction strength 3. Frank-Starling law of the heart a. An increase in venous return = increase in cardiac out put i. More blood in the heart increases cardiac output b. This is due to the stretch which leads to an increase in force of contraction and elastic recoil B. Afterload 1. Definitions a. Pressure in arteries above semilunar valves opposes opening of valves b. The sum of all forces a ventricle must overcome before it gets rid of the blood 2. An increase in afterload = a decrease in stroke volume a. Less blood pushed out b. An impedance in arterial circulation increases afterload 3. A continuous increase in afterload can cause hypertrophy of the myocardium, which can eventually lead to weaker and possibly failing heart 4. Effected by blood pressure, lung disease, atherosclerosis, and aortic stenosis XIII. Heart Homeostasis A. Baroreceptors 1. Monitor blood pressure 2. Pressure sensors in the aorta and internal carotid arteries send a continual stream of signals to the cardiac center 3. If pressure drops, signal rate drops and the cardiac center increases the heart rate 4. If pressure rises, signal rate rises and cardiac center decreases the heart rate B. Chemoreceptors 1. Monitor the effects of pH, carbon dioxide, and oxygen 2. Occur in the aortic arch, carotid arteries and medulla oblongata 3. An increase in CO (2nown as hypercapnia) causes an increase in hydrogen ion levels which may create acidosis (pH <7.35) C. Potassium in the Heart 1. Too much or too little K decreases the heart rate D. Effect of body temperature 1. An increase in body temperature, increases heart rate XIV. Inputs to the cardiac Center A. Parts of the brain that effect the heart 1. Cerebral Cortex 2. Limbic System 3. Hypothalamus B. Proprioceptors 1. Informs the cardiac center about changes in activity 2. Your heart rate will increase before your metabolic demands arise XV. Effects of an Aging Heart A. Hypertrophy of the left ventricle B. Increased oxygen uptake to pump the same amount of blood C. Increased risk of valve malfunction D. Maximum heart rate decrease End of First Power point 2 PowerPoint I. Peripheral Circulation A. Most Common Route 1. Heart > Arteries > arterioles > capillaries > venules > veins B. Portal System 1. When blood flows through two capillary networks before returning back to the heart 2. Usually blood just flows through one capillary before returning to the heart II. Circulation Routes A. Arteriovenous Shunt 1. Artery directly to vein 2. No capillary in between as seen in the common route 3. Usually seen in fingers, toes, and ears in order to decrease heat loss B. Anastomosis 1. Venous Anastomosis a. More commonly seen b. When you have several routes of draining after the capillary bed. c. Pretty much one vein empting into another vein 2. Arterial Anastomosis a. When two arteries merge to provide a collateral/different route to a tissue III. The Vessel Wall A. Tunica Externa 1. Outermost layer 2. AKA tunica adventitia 3. Made of loose connective tissue B. Tunica Media 1. Middle layer 2. Made of smooth muscle, collagen, and elastic fibers C. Tunica Interna 1. Inner most layer, one exposed to blood 2. Made of simple squamous endothelium IV. Arteries A. Elastic (conducting) arteries 1. These are the largest 2. Ex. Pulmonary arteries, aorta, and common carotid artery 3. Expand during systole, recoil during diastole 4. Lessens fluctuations in blood pressure B. Muscular (medium) Arteries 1. Distributes blood to specific organs (femoral and splenic) 2. Smooth muscle constitutes ¾ of wall thickness V. Arterioles and Metarterioles A. Arterioles (resistant arteries) 1. Control the amount of blood to various organs B. Metarterioles 1. Short vessels that connect arterioles to capillaries 2. Muscle cells form a precapillary sphincter at entrance to capillary a. This helps regulate blood flow b. Only about ¼ of the precapillary sphincters are open at a time i. This prevents flooding of the blood out because that would happen if they were all open at the same time VI. Capillaries A. Thoroughfare channel 1. Connects a metarteriole directly to venule, bypassing a capillary bed B. Types of Capillaries 1. Continuous a. Occur in most tissues b. Mostly connected by tight junctions c. Made of endothelial cells that allow passage of solutes 2. Fenestrated a. Found in the kidneys, small intestine, and endocrine system b. These are for organs that require rapid absorption or filtration c. Have filtration pores called fenestrations d. For small molecules 3. Sinusoids a. Found in the liver, bone marrow, and spleen b. These are irregular blood-filled spaces in the liver c. Some have large fenestrations VII. Veins A. Venules 1. Very porous 2. May exchange fluid with tissues 3. Similar to a capillary B. From the capillary 1. Small vein > medium vein > large vein C. Veins 1. Lower blood pressure with little fluctuation 2. Expand easily and have high capacitance 3. Thinner walls 4. Less muscular and elastic tissue 5. Valves inside the veins help skeletal muscle with pushing blood back to the heart D. Venous Sinuses 1. Veins with thin walls 2. Have large lumens 3. No smooth muscle VIII. Blood Distribution in a Resting Adult A. Capillaries Arteries 11% 5% Heart 12% Veins Pulmonary 54% 18% IX. Principles of Blood Flow A. Blood Flow 1. The amount of blood flowing through a tissue in a given time (ml/min) 2. Forces that generate flow a. Resistance b. Pressure i. Outward force exerted by blood X. Blood Pressure A. Measured at the brachial artery B. Systolic Pressure 1. BP during ventricular systole C. Diastolic Pressure 1. Blood pressure during ventricular diastole D. Normal Value in young adult 1. 115/75 mmHg E. Pulse Pressure 1. The difference of diastolic pressure FROM systolic pressure F. Blood pressure determined by cardiac output, blood volume, and peripheral resistance 1. Peripheral Resistance a. Natural vassal constriction/vasodilation XI. Abnormalities of Blood Pressure A. Hypertension 1. Chronic resting Blood Pressure of >140/90 2. Can weaken small arteries and cause aneurysms B. Hypotension 1. Chronic Low resting Blood Pressure 2. Causes blood loss, dehydration, and anemia XII. Peripheral Resistance A. Blood Viscosity (thickness of the blood) 1. Affected by red blood cells and albumen concentration B. Vessel Length 1. Pressure and flow decline with distance C. Vessel Radius 1. Very Powerful influence over flow 2. Most adjustable variable 3. Controls resistance quickly 4. Change in vessel radius XIII. Laminar Flow and Vessel Radius A. Large Radius= average velocity of flow is high B. Small radius = average velocity of flow is low
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