1. Peripheral Circulation & Regulation
Chapter 21
Peripheral Circulation & Regulation
The heart is the pump that provides the major force causing blood to circulate and the blood vessels are the pipes that carry the blood to the tissues of the body and back to the heart
2 major vessel types:
Systemic Vessels:
Transport blood from left ventricle to the body back to right atrium
Pulmonary Vessels:
Transport blood from the right ventricle to the lungs back to the left atrium
AP2 Chap. 21: Cardio Syst-Vessels

2. I. Functions of peripheral circulation
AP2 Chap. 21: Cardio Syst-Vessels

3. I. Fxns of peripheral circulation
5 major fxns:
Carries blood
Takes blood on a roundtrip from heart to tissues back to heart
XD’s nutrients, waste products, & gases w/tissues
Nutrients & O2 can diffuse from blood to cells
Wastes & CO2 can diffuse from cells to blood
Transports substances
Not only the nutrients & wastes but things like hormones & immune system components
Helps to regulate BP
Using contractions of smooth muscle to make vessels larger or smaller
Directs blood flow to tissues
It can flow with purpose directing circulation to areas in need.
AP2 Chap. 21: Cardio Syst-Vessels

4. VI. The dynamics of blood circulation
Laminar & turbulent flow in vessels BP
Blood flow & Poiseuille’s Law
Critical closing pressure & Laplace’s Law
Vascular Compliance
AP2 Chap. 21: Cardio Syst-Vessels

5. VI. The dynamics of blood circulation
Just like water flowing thru pipes certain relationships effect the function of the cardiovascular system these include: BP
Flow
Resistance
Control mechanisms of BP & blood flow
AP2 Chap. 21: Cardio Syst-Vessels

6. VI. The dynamics of blood circulation A
VI. The dynamics of blood circulation A. Laminar & turbulent flow in vessels
Laminar flow: fluid in a smooth tube moves in a stream lined fashion
It flows in concentric layers. Because the outmost blood is against the stationary wall of the vessel, it moves slowest; but as the layers go inward they become faster with the innermost fasted.
Turbulent flow: when a rate of flow exceeds a critical velocity or when fluid passes a constriction, sharp turn, or rough surface.
The vibrations caused by the chaotic blood flow cause sound (Some sounds thru valves in heart or BP cuff) Abnormal sounds can signal a blocked artery
Figure 21.31
Page 741

7. VI. The dynamics of blood circulation B. Blood Pressure
BP measure of the force bld exerts on the blood vessel walls
2 main methods for measuring:
Mercury Manometer
Indirect
Cannula
Direct (tube inserted directly into the blood vessel)
Although 2 methods exist, using a stethoscope (auscultatory methods) are more practical in a clinical setting.
Korotkoff Sounds: point at which cuff loosens enough to allow for turbulent flow in the artery (represents systolic pressure #)
Diastolic Pressure #: when sounds are no longer heard
Figure 21.32
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8. VI. The dynamics of blood circulation B. Blood Pressure
Figure 21.31
Page 753
Figure 21.32
Page 742
AP2 Chap. 21: Cardio Syst-Vessels

9. VI. Dynamics of Blood Circulation
Poiseuille’s Law
Laplace’s Law:
a small D in radius dramatically D’s resistance to flow thus the amount of blood flowing thru the vessel
The force acting on the wall of a blood vessel is proportional to the diameter of the vessel times BP
AP2 Chap. 19: Cardiovascular Syst

10. AP2 Chap. 21: Cardio Syst-Vessels
VI. The dynamics of blood circulation C. Bld Flow & Poiseuille’s (pwah-zuh’yes) Law
Blood flow: amount of bld that moves thru a vessel in a given period
Blood flow is directly proportional to pressure differences
BP  = Bld flow 
Blood flow is inversely proportional to resistance
Resistance  = bld flow 
Resistance: sum of all factors that inhibit bld flow
Effected by:
’s in viscosity
’s in bld vessel diameter
’s in bld vessel length
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11. AP2 Chap. 21: Cardio Syst-Vessels
VI. The dynamics of blood circulation C. Bld Flow & Poiseuille’s (pwah-zuh’yes) Law
Viscosity: resistance of a liquid to flow
Bld’s viscosity is the result of [RBC]. As hematocrit (% of total bld vol. composed of RBC’s) increases so does bld viscosity
Poiseuille’s Law states that a small D in radius dramatically D’s resistance to flow thus the amount of blood flowing thru the vessel.
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12. AP2 Chap. 21: Cardio Syst-Vessels
VI. The dynamics of blood circulation D. Critical Closing Pressure & Laplace’s Law
As pressure in a vessel , the force holding the vessel open , & the vessel tends to collapse.
Critical Closing Pressure:
Pressure at which the blood vessel closes and blood flow stops
Laplace’s Law:
The force acting on the wall of a blood vessel is proportional to the diameter of the vessel times BP
F= force
D= diameter
P= pressure
F = D * P
Shock (BP drops) necrosis
Aneurysm
AP2 Chap. 21: Cardio Syst-Vessels

13. VI. The dynamics of blood circulation E. Vascular Compliance
Tendency for blood vessel vol to  as the BP 
Vessels with a high compliance exhibit large increases in volume when pressure increases a small amount. (vise versa)
Veins:
24X greater compliance than arteries
Thus veins can act as storage areas (reservoirs) for blood because high compliance allows them to hold larger volume than other areas of the vascular system
AP2 Chap. 21: Cardio Syst-Vessels

14. VII. Physiology of Systemic Circulation
Cross sectional area
Pressure & resistance
Pulse Pressure
Capillary XD & regulation of interstial fluid
Fxnal characteristics of veins
BP & FX of gravity
AP2 Chap. 21: Cardio Syst-Vessels

15. VII. Physiology of Systemic Circulation
Physiological characteristics of the circulatory system are determined by:
Anatomy of circulatory system
Dynamics of blood flow
Regulatory mechanisms of the heart & blood vessels
84% of blood resides in the systemic blood vessels
64% in the systemic veins
15% in systemic arteries
5% in capillaries
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AP2 Chap. 21: Cardio Syst-Vessels

16. VII. Physiology of Systemic Circulation A
VII. Physiology of Systemic Circulation A. Cross-sectional area of blood vessels
As the diameter of blood vessels decreases their total cross-sectional area (CSA) increases and the velocity of blood flow thru them decreases
Aorta= 5 cm2 cross sectional area
Capillaries (each with a very small cross sectional area) The total cross sectional area of ALL capillaries = 2500 cm2
Thus the smaller vessels have more area
Velocity of blood flow is greatest in the aorta but total CSA is small. Velocity of blood flow is low in capillaries, but the total CSA is large.
Figure 21.33
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17. VII. Physiology of Systemic Circulation B. Pressure & resistance
BP is initially 100mmHg in the aorta ending at 0mmHg in the right atrium (high to low movement)
Decreases in arterial pressure are directly proportional to resistance. With the highest encountered at the arterioles.
When it gets there 85mmHg at the end 35mmHg
Also fairly high resistance in the capillaries
Low resistance in veins b/c they have a relatively large diameter.
Arteries can contract or relax changing their diameter & pressure
Figure Page 756
Figure 21.34
Page 745
AP2 Chap. 21: Cardio Syst-Vessels

18. VII. Physiology of Systemic Circulation C. Pulse Pressure
Pulse pressure equals the difference between the systolic & diastolic pressures
Increases when:
Stroke volume increases
Vascular compliance decreases
Pulse pressure waves travel thru the vascular system faster than blood flows. PP can be used to take a pulse as the artery expands with the PP waves. (radial pulse)
Pg 746
Fig 21.35
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19. AP2 Chap. 21: Cardio Syst-Vessels
VII. Physiology of Systemic Circulation D. Capillary XD & regulation of interstitial fluid volume
3 things affect the movement of fluid from the capillaries: BP
Capillary Permeability
Osmosis
Capillary XD
Mvmt of substances into & out of the capillary
Most important method used is diffusion
Nutrients, gases & hormones
Some go thru fenestrations others between the cell spaces.
Pinocytosis does a very small amount
Net movement occurs from the blood vessel into the tissues. The lymphatic system removes XS tissue fluid.
AP2 Chap. 21: Cardio Syst-Vessels

20. VII. Physiology of Systemic Circulation
Fxnal Characteristics of Veins
BP & the effect of gravity
Factors that increase venous return to the heart include:
Increase in blood volume
Venous tone (constriction or dilation of the veins)
Based on SNS stimulation
Arteriole dilation
Hydrostatic pressure caused by gravity increases BP below the level of the heart & decreases BP above the level of the heart.
AP2 Chap. 21: Cardio Syst-Vessels

21. VIII. Control of Blood Flow in the tissues
Local control of blood flow by the tissues
Nervous & hormonal regulation of local circulation
AP2 Chap. 21: Cardio Syst-Vessels

22. VIII. Control of Blood Flow in the tissues
Blood flow to the tissues is highly controlled and matched closely to the metabolic needs of tissues.
2 mechanisms of control are:
Local Control
Fxnal characteristics of the capillary bed
Autoregulation of blood flow
Long-term local blood flow
Nervous & hormonal control
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23. AP2 Chap. 21: Cardio Syst-Vessels
VIII. Control of Blood Flow in the tissues A. Local control of blood flow by tissues
Blood flow can vary by organ with some getting more than others with little change.
Some tissues alter blood flow based on metabolic need such as skeletal muscle at rest vs. exercising (20X more flow than at rest).
Blood serves to deliver nutrients & remove waste, but:
Skin: blood flow dissipates heat
Kidneys: eliminated metabolic waste products, regulates water balance, controls pH of body fluids
Small intestine: blood removes the nutrients for liver processing
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24. AP2 Chap. 21: Cardio Syst-Vessels
VIII. Control of Blood Flow in the tissues A. Local control of blood flow by tissues Fxnal Characteristics of the capillary bed
Capillaries can alter blood flow based on the conditions of the tissues they supply
Vasomotion: cyclic fluctuation of contraction & relaxation of sphincters
Vasodilator substances are prod’d as metabolism increases. They literally diffuse from the tissue to the precapillary sphincter muscles to get them to relax.
Pg 751
Fig 21.37
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25. AP2 Chap. 21: Cardio Syst-Vessels
VIII. Control of Blood Flow in the tissues A. Local control of blood flow by tissues Autoregulation of Blood Flow
Arterial BP can D over a wide range, but blood flow remains relatively constant.
Autoregulation is maintenance of blood flow by the tissues themselves.
In the tissues:
Build-up of metabolic waste
Precapillary sphincters dilate
Blood flow increases
Nutrient & O2 supply adequate
Precapillary sphincters constrict
Blood flow decreases
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26. AP2 Chap. 21: Cardio Syst-Vessels
VIII. Control of Blood Flow in the tissues A. Local control of blood flow by tissues Long term regulation
Long term regulation of blood flow is matched to the metabolic needs of the tissue.
Metabolic activity in tissue increases over long term:
Diameter & # of blood vessels increase 
Results in increase in local blood flow.
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27. AP2 Chap. 21: Cardio Syst-Vessels
VIII. Control of Blood Flow in the tissues B. Nervous & hormonal regulation of local circulation
NS control of Arterial BP- important in the minute-to-minute regulation of local circulation
SNS (vasomotor center of the medulla oblongata) controls blood vessel diameter and can be influenced by other areas in the brain.
Vasomotor Tone: state of partial contraction of blood vessels
NS is responsible for routing the flow of blood & maintaining BP
SNS action potentials stimulate adrenal medulla to release epi & norepi which cause vasoconstriction of most blood vessels (Skeletal muscle is opposite)
Figure 21.38
pg 752
AP2 Chap. 21: Cardio Syst-Vessels

28. IX. Regulation of Mean Arterial BP
Short term regulation
Long term regulation
AP2 Chap. 21: Cardio Syst-Vessels

29. IX. Regulation of Mean Arterial BP
MAP: proportional to cardiac output times peripheral resistance
Heart rate = HR
Stroke volume= SV
MAP= CO * PR or HR * SV * PR
Thus an increase in CO, PR, HR, or SV increases MAP or vise versa
2 major control systems to maintain homeostasis:
Short term
Respond quickly but can’t maintain for longer than a few days
Long term
Primarily mechanisms that influence kidney fxn
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30. AP2 Chap. 21: Cardio Syst-Vessels
Regulation of MAP
Short Term reg of BP
Baroreceptor Reflex
Adrenal Medullary Mechanism
Chemoreceptor Reflexes
CNS Ischemic Response
Long Term reg of BP
Renin-angiotensin-aldosterone Mechanism
ADH mechanism
Atrial Natriuretic Mechanism
Fluid Shift Mechanism
Stress relaxation response
AP2 Chap. 21: Cardio Syst-Vessels

31. AP2 Chap. 21: Cardio Syst-Vessels
Baroreceptor Reflex
Minute to minute monitoring of small changes in BP that respond quickly
Figure 21.39
pg 754
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32. AP2 Chap. 21: Cardio Syst-Vessels
Baroreceptor Reflex
Figure 21.40
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33. Adrenal Regulatory Mechanism
Figure 21.41
Page 756
Physical activity/ stress
Stimulation of Medulla oblongata
Signal to SNS to adrenal medulla
Releases Epi & norepi
Result:
Increased HR, SV, vasoconstriction of blood vessels to skin & viscera, and vasodilatation of blood vessels to heart
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34. AP2 Chap. 21: Cardio Syst-Vessels
Chemoreceptors
Figures 21.42
Page 757
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35. AP2 Chap. 21: Cardio Syst-Vessels
Figure 21.43
Page 758
Chemoreceptors
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36. AP2 Chap. 21: Cardio Syst-Vessels
CNS Ischemic Response
Elevation of BP in response to lack of blood flow to the medulla oblongata
Causes high CO2 & low pH levels
Responds to emergency situations where brain is starving for O2
Vasomotor center is stimulated  stimulates vasoconstriction systemic BP rises (provided blood vessels are intact)
AP2 Chap. 21: Cardio Syst-Vessels

37. AP2 Chap. 21: Cardio Syst-Vessels
Regulation of MAP
Short Term reg of BP
Baroreceptor Reflex
Adrenal Medullary Mechanism
Chemoreceptor Reflexes
CNS Ischemic Response
Long Term reg of BP
Renin-angiotensin-aldosterone Mechanism
ADH mechanism
Atrial Natriuretic Mechanism
Fluid Shift Mechanism
Stress relaxation response
AP2 Chap. 21: Cardio Syst-Vessels

38. AP2 Chap. 21: Cardio Syst-Vessels
Long term regulation
Regulation of the [ ] & volume of blood by the kidneys, mvmt of fluid across blood vessel walls, & alterations in the volume of the blood vessels.
Response is in minutes but maintenance can last for hours, days, longer
AP2 Chap. 21: Cardio Syst-Vessels

39. Renin-angiotensin-aldosterone Mechanism
Figure 21.44
Page 760
Decreased BP detected by kidney, results in renin secretion
Result:
Vasoconstriction
Increased H2O absorption
Decreased urine volume
Maintains BP
Renin-angiotensin-aldosterone Mechanism
AP2 Chap. 21: Cardio Syst-Vessels

40. Vasopressin (ADH) mechanism
Figure pg. 761
Increases in osmolarity of blood or decreases in BP result in ADH secretion. Increases H2O reabsorption by kidney, & large amounts result in vasoconstriction. Helps maintain BP
Vasopressin (ADH) mechanism
AP2 Chap. 21: Cardio Syst-Vessels

41. Summary of control of BP long term mechanisms
Page 764
Figures 21.46

42. Long term regulation of BP
Fluid Shift mechanism
Stress-relaxation response
Causes fluid to move from the interstitial spaces into the capillaries in response to a decrease in BP.
Attempt to maintain blood volume
An adjustment of smooth muscles of blood vessels in response to change in blood volume.
AP2 Chap. 21: Cardio Syst-Vessels