RAT 6 Flashcards
what is meant by mechanical physiology?
the actual processes by which blood fills the cardiac chambers and is pumped out of them
what is a cardiac cycle?
sequence of events that take place within the heart from one heartbeat to the next
which valves open when the ventricles contract?
aortic valve
which valves open during ventricular relaxation?
mitral valve (AV valves)
what most likely causes heart sounds?
vibrations of the ventricular and blood vessel walls when the valves shut
when does S1 occur?
when the AV valves close (longer, louder)
when does S2 occur?
when the SL valves close
what are the four phases of the cardiac cycle?
- ventricular filling phase
- isovolumetric contraction phase
- ventricular ejection phase
- isovolumetric relaxation phase
what is EDV?
- end-diastolic volume
- the ventricular volume at the end of ventricular diastole
what is ESV?
- end-systolic volume
- volume of blood present in the ventricles at the end of the ventricular ejection phase
what is SV?
- stroke volume
- amount of blood pumped in one heartbeat
what is a typical value for SV?
70 mL
what is blood pressure?
the outward force that the blood exerts on the walls of the blood vessels
where is blood pressure the highest?
large systemic arteries
what is blood flow?
volume of blood that flows per minute
what are two factors that determine blood flow?
- pressure gradient
- resistance
how is pressure gradient related to blood flow?
directly proportional
how is resistance related to blood flow?
inversely proportional
what has the largest influence on the velocity of blood flow?
the cross-sectional area of the blood vessel
where is blood flow the fastest?
aorta
where is blood flow the slowest?
capillaries
where is blood pressure the lowest?
arteries
what 3 factors determine blood pressure?
- peripheral resistance (PR)
- cardiac output (CO)
- blood volume and vessel compliance
what three factors determine peripheral resistance?
- blood vessel radius
- blood viscosity
- blood vessel length
how does blood vessel radius impact PR?
inversely related; vessel radius increases, resistance decreases
how does blood viscosity impact PR?
PR increases by conditions that increase blood viscosity and vice versa
how does blood vessel length impact PR?
longer the vessel, the greater the resistance
what fourth factor influences PR?
presence of obstructions within the blood vessels that are caused by certain disease states
how do changes in CO impact blood pressure?
- increase CO output, Increase blood pressure
- decrease CO output, decrease blood pressure
the total volume of blood is directly linked to the amount of ___________ in the blood
water
how do changes in blood volume impact blood pressure?
blood volume increases, blood pressure increases
explain how vessel compliance impacts blood pressure
stretch to accommodate the added fluid when blood volume increases, resulting in only a small rise in pressure
which vessels are most compliant?
veins
is the right or left ventricle stronger and thicker?
left ventricle
does the right or left ventricle pump more blood?
left ventricle
does the systemic or pulmonary circuit have more peripheral resistance?
systemic circuit
does the systemic or pulmonary circuit have a higher pressure system?
systemic circuit
what does the orange line represent?
pressure pulsates
what does the black line represent?
mean arterial pressure (MAP) - the average pressure in the arterial circuit
why is blood pressure often represented by two numbers?
because it has both contraction and relaxation periods generated by pulsates
what is systolic pressure?
blood pressure in the arteries when the ventricles are in systole
what is diastolic pressure?
blood pressure in the arteries when the ventricles are in diastole
what is the pulse pressure?
difference between the systolic and diastolic pressures
in what part of the systemic circuit is there a sharp decrease in pressure? why?
in the arterioles because of the sharp increase in peripheral resistance in the arterioles
what instrument is typically used to measure blood pressure?
sphygmomanometer
what changes in blood pressure occur in the capillaries? why?
pressure decreases because the reduction in blood volume that takes place in the capillaries
what changes in blood pressure occur in the veins? why?
pressure declines even further in veins due to the high compliance of veins and the declining resistance as these vessels merge and become larger
what are the four mechanisms that aid in the venous return of blood?
- venous valves that prevent backward flow in the veins
- smooth muscle in the walls of veins that may contract under sympathetic NS stimulation to increase the rate of venous return
- skeletal muscle pumps
- respiratory pumps
what are the branches of the subclavian artery that supply the majority of the arterial blood to the thorax?
anterior and posterior intercostal arteries
what organ does the celiac trunk supply?
abdominal organs
what organ does the superior mesenteric artery supply?
small intestine
what organ does the renal arteries supply?
kidneys
what organ do the gonadal arteries supply?
gonads
what organ does the inferior mesenteric artery supply?
large intestine
what organs do the common hepatic artery supply?
stomach, pancreas, duodenum
what organs does the splenic artery supply?
stomach and pancreas
what organ does the left gastric artery supply?
stomach
what is a pulse?
the pressure changes cause the arteries to expand and recoil with each heartbeat
what is a pulse point?
where the pulse can be felt through the skin in the superficial arteries
what are the most common pulse points?
- carotid
- radial
- brachial
- femoral
- dorsalis pedis
- posterior tibial arteries
