Physiology of Circulation Pages 382-390

What is Arterial Pulse? Alternating expansion and recoil of a blood vessel wall (the pressure wave) that occurs as the heart beats Locate arterial pulse at “pressure points” in superficial arteries These same points are used to stop blood flow due to hemorrhage from injury Avg is 70-76 bpm at rest for a healthy person © 2015 Pearson Education, Inc.

Figure 11.19 Body sites where the pulse is most easily palpated. Superficial temporal artery Facial artery Common carotid artery Brachial artery Radial artery Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery

Blood Pressure & the BP gradient: Blood pressure is: the pressure the blood exerts against the inner walls of the blood vessels Blood is forced along a descending pressure gradient Pressure is highest in the large systemic arteries, lower in the capillaries, and lowest in the veins Elasticity of vessels is pertinent to healthy, elastic arteries © 2015 Pearson Education, Inc.

Measuring Blood Pressure Systolic—pressure at the peak of ventricular contraction Diastolic—pressure when ventricles relax Expressed as systolic over diastolic 120/80 mm Hg is average The brachial artery is used for measurement Hypotension- low blood pressure (<100 sys.) Hypertension- high blood pressure (>140/90) © 2015 Pearson Education, Inc.

Factors that affect Blood Pressure Resistance within blood vessels (increases) Kidneys regulate blood volume via enzymes Temperature- cold causes vasoconstriction Heat causes vasodilation Chemicals Hormones like epinephrine Drugs/nicotine Diet © 2015 Pearson Education, Inc.

Capillary Exchange of Gases & Nutrients Gas and nutrient exchange occurs through capillary walls Driven by concentration gradients Oxygen and nutrients go from blood to tissues Carbon dioxide and other wastes go from tissue to blood Substances diffuse through the interstitial fluid (tissue fluid) found between cells © 2015 Pearson Education, Inc.

Methods of exchange: TRANSPORT Direct diffusion through membranes Diffusion through intercellular clefts/gaps Diffusion through pores Transport via vesicles (bulk transport) © 2015 Pearson Education, Inc.

Figure 11.23 Capillary transport mechanisms. Lumen of capillary Vesicles pore Intercellular cleft Transport via vesicles 4 3 Diffusion through pore Diffusion through intercellular cleft/gap 2 Direct diffusion through membrane 1 Interstitial fluid

The force of pressure in capillary beds Blood pressure forces fluid and solutes out of capillaries at the arterial end Osmotic pressure draws fluid into capillaries at the venous end At the arterial end, BP > OP At the venous end, BP < OP © 2015 Pearson Education, Inc.

Tissue cell Interstitial fluid Figure 11.24 Bulk fluid flows across capillary walls depend largely on the difference between the blood pressure and the osmotic pressure at different regions of the capillary bed. Tissue cell Interstitial fluid Net fluid movement out Net fluid movement in Arterial end of capillary Venule end of capillary At the arterial end of a capillary, blood pressure is more than osmotic pressure, and fluid flows out of the capillary and into the interstitial fluid. At the venule end of the capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary. Blood pressure is higher than osmotic pressure Osmotic pressure remains steady in capillary bed Blood pressure is lower than osmotic pressure