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2012-10-16 16:57:10
blood pressure

lecture notes
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  1. systemic blood pressure
    • when fluid flows through closed system it is under pressure
    • closer to the pum has the greatest pressure
    • blood flow move along the pressure gradient from nhigh to low pressure
    • result is that blood pressure is highest leaving the heart and lowest returing (near zero) dut to length of the cardiovasular system and diameter of vessels
  2. arteriole pressure depends on
    • how much elastic arteries cn be strecthed
    • volume of blood forced through them
    • the pressure is not constant due to heart beat
    • as ventricles contract and eject blood the arteries stretch
    • this causes an increase in pressure (sytole pressure)
    • blood flow away from heart because of difference of pressure
    • during ventricular distole similunar valves shut to prevent the back flow into the heart
  3. elastic recoil in the aorta propels
    • blood forward
    • the kinetic energy used to stretch aorta temporarily stored as potential
    • this energy is conveted back into kinetic (blood moving)as aorta relaxes
    • the energy maintains blood flow through arteries during ventricular diastole
  4. capillary pressure
    • large pressure gradient from aorta to arteriols
    • blood pressure drops to 35- 40 mmhg before entering capillaries
    • at the end of capillaries pressure drops to 20 mmhg
  5. why is low pressure required in capillaries
    • capillaries are very thin walled and cant handle high pressure and will burst if pressure is to high
    • capillaries are premeable to fluid even at low pressure
  6. edema
    swelling of tissue due to excess fluid in hands, feet, etc swells up
  7. venous pressure
    • pressure is steady not palstitle
    • pressure gradient is low
  8. factors aiding venous return
    • respiratory pump
    • muscular pump
  9. muscular pump
    • squeaze veins and pushes blood to the next area and backflow is prevented by valves(acts as elevators)
    • skeletal muscles relax and conctract forcing blood along (milking)
    • blood cannot flow backwards due to valves
    • most important of the two mechanism(respiratory pump and muscular)
  10. 3 factors of maintaining blood pressure
    • cardiac output
    • peripheral resistance
    • blood volume
  11. cardiac output
    • change in heart rate
    • change in stroke volume
    • change in both
  12. blood volume
    • change due to anything you drink or eat
    • under kidney control
    • can remove access fluid if volume is to great
    • cannot add fluid back if there has been loss, but can onlyu prevent further loss
  13. body loses water by
    • sweat
    • breathing
    • urine- the only one body can prevent from losing
    • defication
  14. peripheral resistance
    most important means of controlling blood pressure
  15. peripheral resistance is altered by
    • changing  in diameter of blood vessels(vasocontriction or vasodiliation)
    • distribution of blood between organs
  16. what pathways are used for distribution of blood between organs in the peripheral reisitance
    • neural
    • chemical
  17. vasomoter center
    • located in cardiovasular center of medulla oblongata
    • trasmits nervous impulse along motor nerves to smooth muscles linning blood vessels
    • muscles are always slightly constricted (vessel tone)
    • increase in firing rate causing (vasconctriction)
    • decreae in firing rate causes muscles to relax (vasodialation)
  18. barorecptor initiated reflex
    • pressure receptors located in cartotids, aorta, and large elastic arteries of throat and thorax
    • increase in pressure causes receptors to signal to vasomtor center resulting in vasodilation (bp decrease)
    • also sends message to cardiac center to cause reduction in heart rate
  19. baroreceptor reflex
    • decrease in bp causes oppposite reaction
    • receptor sends singals to vasomotor to cause vasocontriction
    • this cause an increase in bp
    • system helps protect body from rapid change in bp such as occur during standing
  20. chemoreceptor initiated reflex
    • respond to change in o2, co2, and ph levels
    • receptors are located in the carotids and aortic arch
    • low o2, high co2, or low ph sends signlas to vasomoter center to cause vasoconstriction
    • increase in bp speeds blood to heart and lungs
  21. chemical control
    epihephrine and norepinephrine
    • secreated by adrenal medulla
    • part of sympathetic nervous system
    • affects heart by increasing cardiac output
    • causes vasoconstriction of arteriols and blood vessels suppluing digestive organs
    • causes vasodialtion in skeletal and cardiac muscle
    • cause an over all increase in bp
  22. renin- angiotensin- aldosterone (raas)
    • involved in maintaine bp and blood volume
    • response to decrease in blood volume
    • vasoconstriction of aretioles
    • increase water and salt reabsorption
    • functions to increase overall bp
  23. total length of the blood vessels
    • as length increases so do resistance
    • stays relatively constant
  24. characteristic of blood vessels diameter
    • not constant
    • most important factor in determing resistacne
    • smaller in diameter, the greater the resistance
    • ristance is proportional to the 1/radius to the 4th power
    • more fluid in contact with the walls of the blood vessels
    • capiliaries have the greates resistance(smallest) and large vessels have low resistance (aorta)
  25. how is blood flow directly related to the blood pressure
    the higher the pressure the higher the flow
  26. how is flow negativly related to resistance
    • flow go down whe resistance increases
    • flow increases whe resistance decreases