1. First, finish the material from last week…

2. In skeletal muscle, a higher frequency of action potentials leads to a greater amount of tension Figure 2. Graphs showing muscle summation, demonstrating the relationship between stimulus frequency and muscle tension. http://slidingfilament.webnode.com/applications/nervous-system-control/

3. http://www.wellsphere.com/heart-health-article/some-of-the-best-illustrations-in- basic-cardiac-electrophysiology/921006

7. Children with Kwashiorkor http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Leukotr/Kwashiorkor.GIF

8. Blood Pressure, Hypertension and Atherosclerosis

9. Heart Disease Death Rates 2002-2007, Adults Ages 35+, by County Source: US CDC

10. Obesity Trends* Among U.S. Adults BRFSS, 2009 (*BMI ≥30, or ~ 30 lbs. overweight for 5’ 4” person) No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%

11. Arterial Blood Pressure One of the primary regulated variables of the cardiovascular system Sensed by arterial baroreceptors Regulated in the short term (sec. to min.) Blood volume, the other primary regulated variable, is regulated over the longer term (min. to hrs.)

14. Determinants of Blood Pressure MAP = CO x TPR CO = HR x SV MAP is mean arterial pressure (normal ~100 mmHg) CO is cardiac output (normal ~ 5 L/min) HR is heart rate (normal ~ 72 BPM) SR is stroke volume (normal ~ 70 L) TPR is total peripheral resistance

15. Determinants of Heart Rate Activation of the sympathetic NS increases HR Activation of the parasympathetic NS decreases HR At rest, parasympathetic neural activity predominates, so normal HR is slower than intrinsic rate of SA node depolarization.

16. Determinants of Stroke Volume Increased end diastolic volume (EDV) stretches cardiac muscle fibers, which causes heart to contract more forcefully, leading to an increase in SV. Increased sympathetic NS activity increases SV by increasing the influx of calcium into the cardiac muscle cells. These two mechanisms are additive.

20. Preload Preload is the amount that a muscle is stretched before it contracts. In the case of the heart, the end diastolic volume, which stretches the cardiac muscles, is the preload

21. Afterload Afterload is the force that a muscle contracts against. The afterload on cardiac muscle is the arterial blood pressure. High blood pressure (hypertension) increases the afterload, so the heart has to work harder.

22. Blood volume Most important long-term determinant of blood pressure Sensed by venous, atrial and arterial baroreceptors Regulated largely by the kidneys

23. The Role of the Vasculature in Arterial Blood Pressure Recall that arteries are elastic tubes with low resistance Serve as a “pressure reservoir”. They are stretched during systole, and their recoil during diastole maintains blood flow. The ease with which a structure can be stretched is called compliance Compliance =  volume /  pressure

24. MAP = DP + 1/3 (SP-DP) Systolic blood pressure (SP) is the maximum arterial pressure reached during peak ventricular ejection. Diastolic blood pressure (DP) is the minimum blood pressure that occurs just before ventricular ejection. Mean Arterial Pressure (MAP) is the average blood pressure over the course of the cardiac cycle. It is calculated to account for the fact that diastole lasts about twice as long as systole.

25. Arterioles regulate blood flow Determine relative blood flow to each organ Collectively the arterioles act as the major determinant in determining the TPR, and thereby influence the MAP

26. F = ∆PWhere: Flow = pressure gradient R resistance R =  L8  =fluid viscosity r4 p L=tube length r=inside radius of tube 8/p = a proportionality constant From these equations, we can derive Poiseuille’s equation: F = ∆P r4 p hL8 Factors influencing flow

27. Significance for blood pressure The radius of a blood vessel is the most important determinant of resistance A 2-fold decrease in radius will lead to a 16-fold increase in resistance Blood viscosity is proportionate to hematocrit – excess RBC’s increase TPR and therefore MAP

28. Local Control of Arteriolar Tone Increased metabolic –Local increases in CO2, H+, K+ –Local decreases in O2 Endothelial factors that cause vasodilation: –Nitric Oxide –Prostaglandins –Endothelium-derived Hyperpolarizing Factor Endothelial factor that causes vasoconstriction: –Endothelin 1

29. Systemic Control of Arteriolar Tone Increased sympathetic NS activity causes general vasoconstriction The following hormones also cause vasoconstriction: –Epinephrine and norepinephrine –Vasopressin –Angiotensin II

30. Hypertension

31. Distribution of hypertension

32. Blood pressure generally increases with age.

33. Cardiac Hypertrophy Consequence of increased afterload http://www.moondragon.org/health/graphics/cardiomegaly.jpg

34. Atherosclerosis

35. www-ermm.cbcu.cam.ac.uk/nfig003jal.gif The Arterial Wall

36. Yellow Streak

37. http://www.surrey.ac.uk/SBMS/MicrobialSciences/research/immunology.html

38. Development of Fibrous Plaque

39. 1. Abdominal obesity (waist circumference >40 inches for men, 35 inches for women) 2. Triglyceride levels >150 mg/dL 3. HDL cholesterol <40 mg/dL for men, <50 mg/dl for women 4. Blood pressure >130>85 mmHg (normal is about 120/80) 5. Fasting blood glucose >110 mg/dL (normal is 100 mg/dL) The Metabolic Syndrome

40. Vulnerable plaques are most likely to rupture, causing a myocardial infarction or a stroke