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Lecture 4

BIOL 2213 Lecture 4: Phys11:5

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BIOL 2213

Slide 26: Two forces involved in bulk transport: hydrostatic pressure (water pressure/ blood pressure – always high inside the capillary than outside) and net colloid osmotic pressure (pressure that makes osmosis occur) Slide 27: Always higher inside the capillaries Slide 28: Pressure changes -Hydrostatic pressure relative to the osmotic pressure: osmotic pressure stays the same throughout, but the hydrostatic pressure changes (35 in artery vs. 15 in vein) -Osmolarity of interstitial fluid is low, not a lot of dissolved substances in the interstitial fluid -At the arteriole end, the hydrostatic pressure in the capillary and the net hydrostatic pressure exceeds the net osmotic pressure and we get filtration -At the venous end, the hydrostatic pressure has dropped and is lower than the osmotic pressure and we get absorption Within a capillary we have filtration at one end and absorption at the other end – filtration exceeds reabsorption (net loss of blood plasma at the capillaries) Build up of interstitial fluid in the tissue: enema – interstitial goes to the lymphatic system so that we don’t get a build up of it (important for the immune system) Slide 29: Difference between net hydrostatic pressure and net osmotic pressure Net hydrostatic pressure: Hydrostatic presure inside capillary – hydrostatic pressure outside (interstitial fluid) HP drops as you go from arteriole side to venous side Slide 30: A large portion of the blood is in the veins Blood pressure refers to arteriole blood pressure – needs to be maintained so we get proper functioning Hemorrhage: poke hole in major artery – the large volume of blood in the veins can be dumped into the arteries to keep the blood pressure up (Called: Venous Reserve) Smooth muscles in veins contract increase venous pressure and increase venous return which increases stroke volume which increases cardiac output Slide 31: Endothelium, smooth muscle, connective tissue Tend to be more elastic and have less smooth muscle – very stretchy so they can fill up with and store blood Slide 32: Don’t see a pulse in veins Force that moves blood through veins: blood pressure coming form ventricle Skeletal muscle pump: one way valves in veins that don’t allow blood flow back down, skeletal muscles contract, putting force on the blood in the veins and makes the blood move (movement is both down and up – but can’t go down because of valves so the blood goes up) No pumping of smooth muscles in the veins to get the blood to move***** Slide 33: When the one way valves become leaky and can’t prevent backflow – happens a lot in people who stand for large periods of time Slide 35: Another way blood moves in veins: respiratory pump – due to changes in pressure in the cavity where the heart is as you inhale and exhale Skeletal muscle separating pleural cavity and peritoneal cavity, to cause inhalation to occur – the diaphragm flattens out, increases the volume in the pleural cavity (causes negative pressure) which draws air in and causes the blood to get sucked up from the lower parts of the body As the diaphragm flattens out causes slight increase in pressure in the peritoneal cavity As your activity level increases, respiratory rate increases, activity level of skeletal muscles increase, and more blood is being forced through the veins (needed with increased activity) Smooth muscles in veins controlled by sympathetic nervous system Slide 36: Cause increase of blood volume: drinking a large volume of water If venous pressure is increased, stroke volume is increased and increased
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