What does blood flow refer to?

the volume of blood moved

What is blood flow measured in?

ml/min

What are the two factors that blood flow is dependent on?

blood pressure difference at each end of blood vesselresistance to blood flow

What is resistance?

the friction which impedes blood flow between two points

What are the factors that resistance is dependent on?

vessel lumen diameterblood viscositytotal vessel length

What are the two changes that blood flow change can be attributed to?

change in pressurechange in vessel diameter

If pressure stays the same but resistance increases, what happens to blood flow?

blood flow decreases

If pressure difference increases, what happens to blood flow?

blood flow increases

What are the neurovascular effects at blood vessels?

sympathetic nerves release norepinephrine - vasoconstrictionparasympathetic and sympathetic cholinergic nerves release acetylcholine - vasodilation

How does nitric oxide induce vasodilation?

nitric oxide is released from vascular endothelial cells which stimulates the formation of a 2nd messenger in the smooth muscle cell causing muscle relaxation

What are the physical factors that affect blood pressure?

arterial blood volume arterial compliance

What is compliance?

indicates elasticitythe ability to expand then contract passively

Why do blood vessels expand?

expands so that systolic pressure doesn't rapidly increase

What is the function of elastic arteries?

conductingblood from heart to small artery

How does an elastic artery act as a pressure reservoir?

during diastole elastic recoil generates pressure to propel blood distally

What is the function of muscular arteries?

distributingblood goes to organ and tissues

Why are arterioles called resistance vessels?

because they can vasoconstrict

Functions of arterioles

determine minute-to-minute blood flow into capillary bed lumen size has direct impact on blood pressure

What is systemic vascular resistance?

how we measure compliance

What is the major influence on systemic vascular resistance?

vessel radius

What is the function of precapillary sphincters?

guard entrance to each capillary open to allow blood through capillary for normal capillary functionclose with SNS stimulation which leads to blood being "shunted" to venous side using metarteriole

What happens to the flow of water in the capillary bed when hydrostatic pressure is high?

water exits

What happens to the flow of water in the capillary bed when osmotic pressure is high?

water comes back in

What happens to the total area of the vascular bed as blood vessels start branching?

area increases

What happens to blood flow as vessels branch and their lumens get narrower?

blood flow decreases

What is blood flow inversely proportional to?

cross-sectional area of blood vessels

What is hydrostatic pressure?

the force exerted by the fluid pressing against a wall

What is osmotic pressure?

force created by large nondiffusible molecules, such as albumin

Does hydrostatic pressure change as blood moves along the length of the capillary bed?

hydrostatic pressure decreases along its length

Does osmotic pressure change as blood moves along the length of the capillary bed?

it does not change along the length of the vessel

Where does diapedesis occur?

venule

Skeletal muscle pump

skeletal muscle contraction propels blood proximally one-way valves prevent backflow

At rest, what proportion of the body's blood do the veins contain?

veins contain almost 2/3 of the body's blood

What are the causes of increased venous pressure?

increased activity of sympathetic nerves to veinsincrease in skeletal muscle pumpincrease in blood volumeincreased inspiration movements

What is stroke volume?

volume (mL) of blood ejected per heart beat from the ventricle

What is stroke volume the difference of?

the difference between ventricular end-diastolic volume and end-systolic volume

What is end-diastolic volume?

how much blood is in the ventricle before the ventricle contracts max amount that can possibly leave the ventricle

What is end-systolic volume?

how much blood is in the ventricle at the end of systole

What is preload?

end-diastolic volume or venous return

How can you increase preload?

increase in blood volumeslower heart rate

How does an increase in preload affect stroke volume?

increase in preloadincrease in end-diastolic volumeincrease in stroke volume

What does an increase in venous pressure lead to?

increase in venous returnincrease in atrial pressureincrease in end-diastolic volumeincrease in stroke volume

What is afterload?

resistance that the heart must overcome to circulate blood

What happens if you increase afterload?

heart has to work harder thereby increasing cardiac workload which increases the oxygen requirement

How does an increase in afterload affect stroke volume?

increase in afterload leads to a increase in end-systolic volume leads to a decrease in stroke volume

What is an inotropic effect?

force that the muscle can create at a given length

How does preload affect inotropy?

increasing preload (increasing end-diastolic volume) increases muscle fiber lengthincreases magnitude of muscle shorteningincrease in inotropic effect

What is the Frank-Starling law?

states that the amount of blood ejected by the ventricle depends upon volume present in the ventricle at the end of diastole

What does stroke volume and cardiac output directly correlate with?

end-diastolic volume

What does the Frank-Starling law say about the relationship of stroke volume and cardiac output to venous return?

stroke volume and cardiac output are directly proportion to venous return

Does contractility increase or decrease stroke volume?

increase stroke volume

What can lead to an increase and decrease in contractility?

increase: exercisedecrease: heart failure

What is the ejection fraction?

measurement of the percentage of blood that exits the ventricle during one ventricular systole

What is the normal range for ejection fraction?

at rest, a normal heart only pumps out around 60% of the blood with each heartbeat

How can ejection fraction be increased?

increased contractility may increase the ejection fraction but will also increase cardiac muscle workload

What effect does an increase in end-diastolic volume have on stroke volume and ejection fraction?

increases stroke volume without changing ejection fraction- PSNS has negative chronotropic effect which allows higher preload - increased preload results in increased muscle stretch which then causes a positive inotropic effect

What effect does an increased force of contraction have on stroke volume and ejection fraction?

increase in stroke volume by increasing ejection fraction

Extrinsic control of stroke volume via positive inotropic effect include

sympathetic stimulation to ventricular muscle fibershormonal control (thyroid hormone, epinephrine/norepinephrine)

What is cardiac output?

total amount of blood (L) pumped out of ventricle in one minute

Generally how do you increase cardiac output?

increase heart rate and/or stroke volume

What neurotransmitters produce neuromuscular effects in the heart?

sympathetic nerves: norepinephrineparasympathetic nerves (vagus nerve): acetylcholine

What are the different neuromuscular effects of the heart?

chronotropy: timing, heart rateinotropy: (+) effect = more forceful contraction dromotropy: speed of conduction going through AV node lusitropy: rate of myocardial relaxation (speed of decrease of cytosolic calcium)

To speed up the heart rate (positive chronotropic effect):

deliver sympathetic hormone (epinephrine)release more sympathetic neurotransmitter (norepinephrine) reduce release of parasympathetic neurotransmitter (acetylcholine)

Negative chronotropic effect can be seen with:

increasing ageincreasing fitness level

How does heart rate affect preload?

a fast heart rate will leave no time for preloading

What is pulse pressure?

the difference between systolic blood pressure and diastolic blood pressure

What are the factors determining pulse pressure?

stroke volume- increase stroke volume will increase systolic blood pressurearterial compliance- a decrease of compliance occurs with atherosclerosis which can lead to increased systolic blood pressure

What is mean arterial blood pressure?

average driving pressure of blood throughout cardiac cyclebest indicator of tissue perfusion

How much time does the heart spend in diastole?

twice as long in diastole

How does short-term blood pressure regulation work?

every few secondsstretch-sensitive mechanoreceptors located in walls of specific arteriesmonitor pressure of blood flow to brain and body action potential fired continuously at normal blood pressure- rise in pressure stretches baroreceptor which leads to increased signals sent via ANS to CNS - low pressure decreases signals to CNS

Baroreceptor locations

in wall of arteryaortic archcarotid sinus (most proximal portion of carotid artery)all these baroreceptors send signals to medulla oblongata

What nerves are involved in baroreceptor messaging?

CN IX glossopharyngeal nerve- from carotid sinus receptorsCN X vagus nerve- from aortic arch receptors

What affects the stretch of baroreceptors?

mean arterial pressure