CH EXAM REVIEW ADV. EX. PHYS. ch 3

Hemodynamics

the study of how blood flows through the cardiovascular system

Blood flow

the amount of blood that passes through a vessel in a given amount of time

the basic relationship of blood flow

blood flow = pressure / resistance

4 factors that increase blood flow

pressure gradient, vessel radius, blood viscosity, vessel length

pressure gradient

blood always flows from high pressure to low pressure. The larger the pressure difference, the greater the blood flow

vessel radius

this is the most important factor. Small changes in radius create HUGE changes in blood flow.

blood viscosity

how thick the blood is. thicker blood → higher resistance → lower blood flow

vessel length

longer blood vessels create more resistance. more distance = more friction =lower blood flow

Total peripheral resistance (TPR)

the total resistance the heart must pump against. most resistance comes from arterioles because arterioles have lots of smooth muscle that can constrict or dilate

Poiseuilles law

blood flow increases when: pressure increases, radius increases

blood flow decreases when: resistance increases, viscosity increases, length increases

Mean arterial pressure (MAP)

the average pressure in the arteries during one cardiac cycle

MAP equation

DBP + 1/3 (SBP-DBP)

Blood pressure is determined mainly by

cardiac output x total peripheral resistance. Higher CO → Higher BP → Higher TPR→ higher BP

Why doesn’t diastolic blood pressure increase during aerobic exercise?

during exercise, cardiac output increases a lot. Normally, this should increase blood pressure however, the exercising muscles release chemicals like nitric oxide, adenosine, prostaglandins.

These chemicals cause vasodilation. Vasodilation lowers total peripheral resistance. The decrease in resistance offsets the increase in cardiac output.

Therfore, Diastolic blood pressure stays about the same or may decrease slightly

Why doesn’t diastolic blood pressure increase during aerobic exercise? test

During aerobic exercise, local vasodilation in active muscles decreases total peripheral resistance. This offsets the increase in cardiac output, so diastolic blood pressure remains relatively unchanged

Is blood flow distribution even?

No the body constantly sends blood where it is needed. for example, during exercise, more blood goes to skeletal muscle, heart and skin instead of kidneys, liver, and GI tract

Functional sympatholysis

the sympathetic nervous system normally causes vasoconstriction. If this happened everywhere,working muscles wouldn’t get enough blood.

Instead, working muscles release chemicals. These chemicals override sympathetic vasoconstriction. This allows muscles to receive the blood they need which is called functional sympatholysis

so it stops the sympathetic effect in essence

exercise hyperemia

the increase in blood flow to working muscles during exercise. Because active muscles need more oxygen and nutrients, while removing carbon dioxide, heat, metabolic waste

What causes exercise hyperemia?

local vasodilators: nictric oxide, adenosine, potassium, hydrogen ions, prostaglandins

sympathetic receptors

alpha 1, alpha 2, beta 1, beta 2

alpha 1 location and action

most blood vessels. vasoconstriction → higher resistance → higher BP

alpha 2

Mainly presynaptic neurons, reduces norepinephrine release, acts as negative feedback

beta 1 location and effect

heart. increase hr, contractility, conduction velocity

beta 2 location and action

skeletal muscles vessels, coronary vessels, bronchioles. Vasodilation, bronchodilation

parasympathetic receptors

M2

M2 location and effect

heart. decrease in HR, decrease in conduction

Local vasodilators that are released by exercising muscles

nitric oxide, adenosine, prostaglandins, potassium, hydrogen ions. They all increase blood flow

endothelium

thin inner lining of blood vessels which releases nitric oxide. This causes smooth muscle to relax, causing vasodilation and more blood to flow

why do exercising muscles receive more blood

as muscles work, they use oxygen faster. they also produce more waste products. These waste products trigger local vasodilation. Blood vessels widen, allowing much more blood to reach the muscles which is called exercise hypermia

why are arterioles called resistance vessels?

Because they contain lots of smooth muscle. small changes in arteriole diameter produces large changes in resistance. since resistance controls blood flow, arterioles become the primary regulators of tissue perfusion

what is hemodynamics

it is the study of blood flow through the cardiovascular system

blood flow equation

flow= pressure / resistance

4 factors affecting blood flow

pressure, radius, viscosity, vessel length

which factor has the greatest effect on blood flow?

vessel radius

what is viscosity

thickness of blood

what is TPR

total peripheral Resistance

which vesseles create the most resistance?

arterioles

MAP stands for

mean arterial pressure

what determines blood pressure

cardiac output x total peripheral resistance

why doesnt DBP incrrease during exercise?

vasodilation decreases TPR, offsetting the increase in cardiac output

what is exercise hyperemia

increased blood flow to active muscles during exercise.

what is functional sympatholysis

local metabolites override sympathetic vasoconstriction in active muscles

what does a1 stimulation cause

vasoconstriction

what does B1 stimulation cause

increased HR and contractility

what does B2 stimulation cause?

vasodilation and bronchodilation

which parasympathertic receptor is found in the heart

M2

what does nitric acid do?

causes vasodilation

name three local vasodilators released during exercise

nitric oxide, adenosine, prostaglandins

why do active muscles receive more blood?

local metabolites cause vasodilation, increasing blood flow

why are arterioles called resistance vessels

they are the main site of vascular resistance because they can constrict or dilate significantly