BP and HP regulation Flashcards
what is the formula for blood pressure (BP)
BP = CO x PR (cardiac output x peripheral resistance)
what is cardiac output (CO)?
quantity of blood move by ventricle into aorta per minute
what is peripheral resistance (PR)?
blood vessel resistance to flow
what is the formula for cardiac output?
Cardiac Output = Stroke Volume (SV = blood volume ejected per beat) x Heart Rate (HR = beats per minute)
what are the two intrinsic mechanisms for regulating stroke volume?
preload (frank-sterling)
afterload
explain the preload (frank-sterling) mechanism of stroke volume regulation
when more blood fills during diastole (ventricular relaxation) then there will be greater force of contraction in systole and great volume of blood ejected.
how is the contraction force of the heart regulated?
how does this differ from that of skeletal muscle?
increasing the number of actin-myosin cross bridges increases contraction force of the heart (alter length-tension relationship)
in skeletal muscle, the length-tension relationship already allows for optimal actin-myosin interaction, and therefore no alteration is needed (hardly ever)
how does preload impact venous return?
more blood will be returned to the heart will increase preload and therefore increase systole volume
what is afterload
resistance left ventricle must overcome to circulate blood
if a person has hypertension or atherosclerosis this will
_ stroke volume
why?
decrease
The ventricle is too busy fighting to overcome resistance of the vessels, therefore it will only push out a little bit of blood
When afterload is high, how does the body compensate?
increased preload
what are the long term effects of high afterload on heart muscle, stroke volume, and blood pathway
overworking the heart muscle which leads to decreased SV, the blood backs up and enters the lungs
pulmonary edema
what are the extrinsic controls of stroke volume
nervous system, which impacts contractility
how does the nervous system (fight or flight response) impact stroke volume
hormones cause increase/cause release of Ca2+ which leads to increase in contraction strength (via more crossbridges)
how does the autonomic nervous system help raise or lower stroke volume?
what chemicals are used?
increasing or decreasing calcium concentration
sympathetic nerves and adrenal medulla use norepinephrine and epinephrine
