Cardiac Muscle: Control and Coordination of Heart Contractions

1. Unit 8 Notes

3. Cardiac Muscle • Cardiac muscle can contract spontaneously and independently, even if all nervous connections are severed • Different muscle cells in different areas have different rhythms • Atrial cells: 60 beats/min • Ventricular cells: 20-40 beats/min • Because of this, we need a controlling system to regulate & coordinate contractions!

4. What controls the heart beating? • 2 controlling systems • Nerves of Autonomic Nervous System • Acts like “brakes” and “accelerators” • Intrinsic Conduction System • AKA nodal system • Enforces a contraction rate to keep everything together

5. Parts of Intrinsic Conduction System • Sinoatrial Node (SA node) - the pacemaker; where the action potential originates, starting each heartbeat • As action potential moves, contraction of atria is stimulated • Atrioventricular Node (AV node) - receives action potential from SA node and sends along to…

6. Parts of Intrinsic Conduction System • Atrioventricular Bundle (Bundle of His) – branches off into right and left bundle branches, and then sends action potential along to… • Purkinje Fibers – action potential received begins ventricular contraction at apex and continues contraction back up toward atria, helping to eject blood into pulmonary trunk or aortic arch

7. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html

8. The Cardiac Cycle • Refers to one complete heartbeat • Systole – heart contraction • Diastole – heart relaxation • Since most of pumping done by ventricles, terms usually refer to ventricles (unless otherwise stated) • Normal length of cycle: 0.8 seconds • Translates into 75 beats/min (average)

9. The Cardiac Cycle • First heart sound or “lub” • Atrioventricular valves close at beginning of ventricular systole • Second heart sound or “dub” • Aortic and pulmonary semilunar valves close at beginning of ventricular diastole

10. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_1_.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_1_.html

11. Electrocardiogram • Electrodes placed on the surface of the body • Action potentials through myocardium during cardiac cycle produces electric currents that can be measured • http://video.about.com/heartdisease/Electrocardiogram.htm

12. Electrocardiogram • Pattern • P wave • Impulse moves across atria (depolarization/contraction) • QRS complex • Spread of impulse to ventricles (depolarization/ contraction) • Atria repolarization/ relaxation • T wave: • Ventricle repolarization/ relaxation • End of electrical activity

13. Cardiac Arrhythmias • When any electrical activity of the heart is irregular

14. Types of Cardiac Arrhythmias • Heart Block • AV node damaged • Ventricles beat at their own rate (slower) • Slower heart beat can lead to ischemia: lack of blood flow to heart • Leads to fibrillation: rapid, uncoordinated movement of heart muscle (= cardiac arrest, death) • Artificial pacemakers usually implanted to correct problem

15. Types of Cardiac Arrhythmias • Tachycardia • Resting heart rate above 100 bpm • Bradycardia • Resting heart rate below 60 bpm • Heart Palpitations • Premature Atrial Contractions • Misshapen “P” Wave • Premature Ventricular Contractions • Misshapen “QRS” Complex / T Wave

17. Heart Murmurs • Heart Murmurs: unusual sounds from heart (besides normal “lub-dub”) • Often indicate valve problems • If valve does not close, “swishing” sound from blood flowing back • If valve is narrowed (stenosed), “rushing” sound

18. Heart Murmurs • Doctors will listen at different locations on your chest to see if valves are functioning properly

19. Now, let’s talk about blood flow in the rest of the body!!! The Vascular System: Taking Blood to the Body and Back

20. The Vascular System • Arteries – carry blood away from the heart • Branch into Arterioles • Pulmonary Arteries - carry deoxygenated blood • Systemic Arteries – carry oxygenated blood • Capillaries- exchange • One cell layer thick! • Oxygen and nutrients cross to cells • Carbon dioxide and wastes cross into blood • Veins – carry blood back to the heart • Branch into Venules • Pulmonary Veins – carry oxygenated blood • Systemic Veins – carry deoxygenated blood • Has valves internally!

21. Vascular System Anatomy • Veins & Arteries have three layers (tunics) • Tunic interna • Tunic media • Tunic externa • Opening through which blood flows is called lumen

22. Vascular System Anatomy

24. Vital Signs

25. Vital Signs • Pulse • Blood Pressure • Respiratory Rate • Body Temperature • All indicate the efficiency of the system

26. Pulse • Pulse – pressure wave of blood • Monitored at “pressure points” where pulse is easily felt • Measured on arteries because pressure is strong enough to be felt

27. Pulse • Radial pulse and Carotid pulse most common (helps to have the artery close to the surface & hard surface to press it on) • Average pulse is 65-80 beats per minute • Pulse influenced by activity, postural changes, and emotions… stress… tests… homework… you know  • Pressure points can also be used as compression point if trying to stop blood flow

28. Blood Pressure • Measurements by health professionals are made on the pressure in large arteries (usually the brachial artery) • Pressure in blood vessels decreases as the distance away from the heart increases (not feeling the pressure created by the left ventricle as much!)

30. Blood Pressure • Systolic Pressure (heart ventricles contract) • Diastolic Pressure (heart ventricles relax) • Blood Pressure= systolic/diastolic • Normal= 120/80

31. Measuring Arterial Blood Pressure

32. Changing Blood Pressure • Temperature • Heat has a vasodilation effect • Cold has a vasoconstricting effect • Chemicals • Various substances can cause increases or decreases • Diet

33. Blood

34. Blood Facts • Only fluid tissue in human body • Blood heavier than water and 5 times thicker • Slightly basic – pH approximately 7.4 • Temperature slightly higher than body temperature (100.4°F) • Approximately 6 quarts (1.5 gallons) in adult

35. Blood Facts • Blood stays in a closed system except… • White blood cells travel in and out of the blood stream (lymphatic system) • Water and solutes (ions, nutrients, etc) travel in and out of the blood stream

36. Blood Functions Include… • Distribution & Transport • Respiratory Gases • Nutrients • Wastes • Bacteria, Viruses, Toxins, etc. • Regulation and Maintenance • Hormonal Regulation • pH balance (blood is a buffer!) • Temperature

37. Blood Functions Include… • Protection • Clotting • Immunity

38. Composition of Blood • Plasma – 55% of blood • Mostly water (90%) • Plasma proteins • Albumin – pH • Clotting Proteins • Antibodies - defense • Salts (electrolytes) • Nutrients • Waste Products • Hormones • Gases

39. Composition of Blood • Formed Elements - 45% of blood • Erythrocytes (Red Blood Cells) • Leukocytes (White Blood Cells) • Plateletes

40. Formed Elements • Erythrocytes (RBC) • No nucleus, very few organelles • Contains hemoglobin • Iron-containing protein that helps transport oxygen • Biconcave disk • Increases surface area for gas transport • Outnumber WBC 1000 to 1 • Formed by red bone marrow

41. Formed Elements • Leukocytes (WBC) • Only complete blood cell; contain nucleus and organelles • Needed for defense • Can slip in and out of blood vessels where needed for immune response • Also created in bone marrow • Types of WBC…

42. Formed Elements • Types of WBC • Granulocytes: contain granules • Neutrophils: most common WBC, active phagocytes (destroy harmful particles or cells) • Eosinophils: kill parasitic worms, allergies • Basophils: contain histamine (vasodilator)

43. Basophil Neutrophil & Eosinophil

44. Formed Elements • Types of WBC • Agranulocytes: no granules • Lymphocytes: produce antibodies, fighting tumors & viruses • Monocytes: largest WBC, fight chronic infections

45. Monocyte Lymphocyte

46. Formed Elements • Platelets • Not cells, but rather fragments • Important in blood clotting

47. Steps to Blood Clotting • 1. Vessel damage, blood loss; collagen fibers exposed • 2. Vascular spasm to decrease blood loss; Platelets become “sticky” and cling to fibers

48. Steps to Blood Clotting • 3. Anchored platelets signal to attract more platelets; Platelet plug forms • 4. Coagulation; fibers reformhttp://health.howstuffworks.com/human-body/systems/circulatory/blood3.htm

49. Blood Transfusions • Body can only compensate for a certain amount of blood loss • Loss of 15-30% of blood: weakness • Loss of over 30%: severe shock, usually fatal • Therefore, we need to replace the blood when it is lost! • Blood treated with an anticoagulant (prevents clotting) can be refrigerated at 4°C for about 35 days

50. Blood Transfusions • However, blood must be compatible with your body! • All plasma membranes of RBC bear certain proteins (antigens) which are unique • We also have antibodies looking for antigens • We can tolerate our own antigens, but if we get different antigens from another person, antibodies will attack RBC! • This causes RBC’s to clump (agglutination)