Blood Pressure and Capillary Exchange March 8 –March 9, 2016

Try to find several of these! Pulse Points Areas where can easily feel pulse Also act as pressure points. Compressing these points will reduce downstream blood flow useful when dealing with major wounds. Try to find several of these!

Blood Pressure Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels. Usually, we refer to the pressure of the arteries.

Blood Pressure Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels. Usually, we refer to the pressure of the arteries. Why does blood pressure drop so low in the capillaries? Because there are so many more capillaries So that the flow of blood will slow to facilitate exchange of materials

Blood Pressure Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels. Usually, we refer to the pressure of the arteries. Why do we record blood pressure as two numbers? Blood pressure in the arteries fluctuates with the cardiac cycle.

Blood Pressure Systolic pressure occurs due to ventricle contraction Diastolic pressure occurs when ventricles relax

Measuring Blood Pressure A sphymomanometer is placed over the brachial artery. The cuff is inflated to ~150 mmHg (above systolic pressure) Air pressure is slowly released from cuff while a stethoscope is used to listen for Korotkoff sounds in the artery. Correct responses: 118 /72 – normal 124/74/0 – absent 5th phase, so 4th phase is used for diastolic. This can occur in pregnant women, people with arteriovenous fistulas (a direct connection between an artery and a vein) – which sometimes just develops in the legs, but is also sometimes surgically created for hemodialysis, and /or in people with aortic insufficiency – a leaky aortic semilunar valve

Measuring Blood Pressure Test yourself! (Start at ~3:30) Korotkoff sounds Cuff pressure > systolic pressure there is no blood flow through artery  NO SOUNDS Cuff pressure = systolic pressure blood begins to flow turbulently through artery  TAPPING SOUND BEGINS Cuff pressure = diastolic pressure blood begins to flow smoothly  SOUNDS DISAPPEAR 3:30 #1: 118 / 72 - normal #2: 124 /74/0- absent 5th phase -- can be caused by atherosclerosis. Estimate 5th #3: 132 / 86 - elevated

Factors which affect BP Increased cardiac output (heart rate & stroke volume) increases blood pressure Exercise Stress / Sympathetic nervous system Increased peripheral resistance (friction of blood traveling through vessels) increases BP Atherosclerosis Constriction of blood vessels (due to sympathetic nervous system, cold, chemicals such as nicotine) Number of vessels (body size / fat / pregnancy) Increased blood volume increases blood pressure Kidney problems Book says “for each lb of fat, miles of additional blood vessels are needed” Which factors will decrease BP?

Resting Blood Pressure Hypotension is low blood pressure. May cause dizzy spells, especially when rising Not problematic among young, healthy people Acute hypotension may indicate shock Pulse pressure = difference between systolic and diastolic. High pulse pressure often indicates heart disease, while low pulse pressure often indicates an ineffective heart (such as leaky valves)

Resting Blood Pressure Hypertension can be a positive feedback cycle – why? Hypertension is high blood pressure. Damages blood vessels, which may lead to clots and atherosclerosis Causes heart to work harder, leading to enlarged heart that will eventually weaken Pulse pressure = difference between systolic and diastolic. High pulse pressure often indicates heart disease, while low pulse pressure often indicates an ineffective heart (such as leaky valves). Other causes of high pulse pressure are overactive thyroid and iron deficiency anemia

Capillary Exchange Capillary exchange is the movement of substances (water, gases, nutrients, wastes, etc.) between capillaries and the interstitial fluid of tissues Capillaries have special features which increase their permeability: Intercellular clefts: spaces between cells Fenestrations: very thin membrane- covered spots, or pores http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf

Capillary Exchange Capillary exchange is the movement of substances (water, gases, nutrients, wastes, etc.) Capillaries have special features which increase their permeability: Intercellular clefts: spaces between cells Fenestrations: very thin membrane -covered spots, or pores Clefts and fenestrations are most important for the diffusion of what kinds of substances? Water, and other lipid-insoluble substances What can get through without their help? O2, CO2, fats http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf

Capillary Exchange Capillary exchange is the movement of substances (water, gases, nutrients, wastes, etc.) Capillaries have special features which increase their permeability: Intercellular clefts: spaces between cells Fenestrations: very thin membrane -covered spots, or pores What type of capillaries don’t have fenestrations or intercellular clefts? Capillaries in the brain – work with astrocytes to form blood-brain barrier http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf

Capillary Exchange Differences in pressure in blood pressure and osmotic pressure help fluids move out of capillaries at the arterial end and into capillaries at venous end. Watch me! http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf; oncotic pressure – osmotic pressure due to proteins such as albumin; hydrostatic is more like fluid pressure

Closure What was our objectives, and what did we learn? What was our learner profile trait and how did we demonstrate it? How does what we did today tie to our unit question? http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf

Exit Ticket http://www2.sunysuffolk.edu/pickenc/Capillary%20Exchange.swf