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Blood vessels and circulation
Blood vessels transport blood throughout the body. There are three main types: arteries, which carry blood away from the heart; capillaries, where nutrients and wastes are exchanged; and veins, which carry blood back to the heart. Blood flow is regulated through pressure, resistance, and the actions of the cardiovascular system to ensure adequate circulation throughout the body. Neural and hormonal mechanisms precisely control blood pressure and flow through reflexes and the release of substances like epinephrine and norepinephrine.
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Blood vessels and circulation
- 1. Blood Vessels andCirculation Chapter 13 Pgs 389-403
- 2. Overview • Introduction • Cardiovascular • The Anatomy of Blood Regulation Vessels – The autoregulation of blood – flow Structure of vessel walls – The neural control of blood – Arteries pressure and flow – Capillaries – Hormones and – Veins cardiovascular regulation • Cardiovascular Physiology – Pressure – Resistance – Circulatory pressure
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- 12. Circulatory Physiology • 2factors affect blood flow through capillaries: – Pressure – Resistance • Vascular resistance • Viscosity • Turbulence
- 13. Pressure • Hydrostatic pressure •Circulatory pressure – Overall pressure difference between base of aorta and entrance to RA • Avg is 100 mm Hg – Needed to force blood along – Divided into 3 components • Arterial pressure = blood pressure • Capillary pressure = pressure in caps • Venous pressure = pressure in veins
- 14. Resistance • For bloodto flow: – Circulatory pressure must be great enough to overcome total peripheral resistance • But pressure low in veins so focus on arterial system (called peripheral resistance) • Neural and hormonal controls • Sources of peripheral resistance: – Vascular resistance – Viscosity – Turbulence
- 15. Vascular Resistance • Resistanceof the blood vessels • Most important factor is friction between the blood and the vessel walls – Friction depends on: • Length • Diameter
- 16. Viscosity • Resistance toflow caused by interactions among molecules and suspended materials in a liquid • Viscosity of blood 5xs that of water • Remains constant
- 17. Turbulence • Blood flowsmooth – Slowest flow near the walls; fastest at the center • High flow rates, irregular surface, sudden changes in vessel diameter = turbulent flow (swirls and eddies created) • Slows the flow, increases resistance
- 18. Circulatory Pressure • Wherewould you expect to find pressure the: – Highest? – Lowest? • Arterial blood pressure – Systolic pressure – Diastolic pressure – Pulse pressure
- 20. Capillary Pressures • Unlikeother arteries because capillary walls permeable – Most reabsorbed – Some water and solutes enter lymphatic vessels • This continuous movement plays important role in maintaining homeostasis
- 21. Capillary Exchange • 4important functions – Maintain constant communication between plasma and ISF – Speeds the distribution of nutrients, hormones, and dissolved gases throughout tissues – Assists the movement of insoluble lipids and tissue proteins that are impermeable – Flushes bacterial toxins and other chemical stimuli to lymphoid tissue and organs that provide immunity from disease
- 24. Venous Pressure • Veinsbecome larger – Drops resistance, increases flow rate • 2 factors overcome gravity – Muscular compression – Respiratory pump
- 25. Cardiovascular Regulation • Tissueperfusion—tissue blood flow • Homeostatic mechanisms regulate cardiovascular activity to ensure tissue perfusion meets demand for oxygen and nutrients • 3 variable factors that influence tissue perfusion: – Cardiac output – Peripheral resistance – Blood pressure
- 26. Cardiovascular Regulation • Cellsbecome active = increased circulation to region • Goal of cardiovascular regulation is to ensure that these blood flow changes occur: – At an appropriate time – In the right area – Without drastically altering blood pressure and blood flow to vital organs • Factors involved in regulation of cardiovascular function include: – Local factors – Neural mechanisms – Endocrine factors
- 28. Autoregulation of BloodFlow • Precapillary sphincter – Respond automatically to alterations in local environment • Increased or decreased levels of oxygen and/or carbon dioxide – Dilation caused by vasodilators – Contraction caused by vasoconstrictors
- 29. Neural Control ofBlood Pressure (BP) and Blood Flow (BF) • Cardiovascular (CV) centers in medulla responsible – Includes a cardioaccelerator center and cardioinhibitory center • Vasomotor center (part of CV) – Primarily controls diameters of arterioles – Inhibition of center leads to vasodilation • Will this increase or decrease peripheral resistance? – Stimulation of center leads to vasoconstriction • CV centers detect changes in tissue by monitoring: – Arterial blood (esp bp) – pH – Dissolved gas concentrations
- 30. Baroreceptor Reflexes • Monitordegree of stretch in walls of expandable organs • Located in: – Carotid sinuses – Aortic sinuses – Wall of RA • Initiate baroreceptor reflexes – Autonomic reflexes that adjust CO and peripheral resistance to maintain normal arterial pressures
- 34. Chemoreceptor Reflexes • Respondto changes in carbon dioxide levels, oxygen levels, or pH in blood and CSF • Found in: – Carotid bodies – Aortic bodies – Medulla (CSF)
- 36. Hormones and Cardiovascular Regulation • Provides both short term and long term regulation • E and NE immediately stimulate CO and peripheral vasoconstriction • ADH, angiotensin II, EPO, and ANP – Affect long term regulation of blood volume