Module 4 Flashcards
How blood distributed throughout the circulatory pathway @ any 1 time?
70% in systemic circulation
18% in pulmonary circulation
12% in coronary circulation –> small organ BUT large demand for blood supply
Of that 70% in systemic circulation, how much is in the arterial system?
16%
**called “stressed” volume
Of that 70% in systemic circulation, how much is in the venous system?
54%
**largest “reservoir” of blood volume in body; called “unstressed” volume
How does the pressure gradient change in the heart (from when blood enters the heart to when it is pumped into systemic circulation)?
Enters @ 0 - 4 mmHg
Leaves @ 100+ mmHg
How does the pressure gradient change in systemic circulation (from when it enters systemic circulation to when it returns to heart)
Enters @ 100+ mmHg
Leaves @ 0 - 4 mmHg
What is the pressure in the right atria?
0 - 8 mmHg
What is the systolic and end diastolic pressures of the right ventricles?
Systolic = 15 - 28 mmHg (has to pump blood through pulmonary valve)
End Diastolic = 0 - 8 mmHg
What is the systolic and diastolic pressures in the pulmonary trunk?
Systolic = 15 - 30 mmHg
Diastolic = 3 - 12 mmHg
What is the pressure in the pulmonary capillaries?
10 mmHg
What is the pressure in the pulmonary veins?
4 - 12 mmHg
What is the pressure in the left atria?
4 - 12 mmHg
What is the systolic and end diastolic pressures in the left ventricle?
Systolic = 90 - 140 mmHg –> needs to pump blood systemically
End Diastolic = 4 - 12 mmHg
What is the systolic and diastolic pressures in the aorta?
Systolic = 96 - 140 mmHg
Diastolic = 60 - 90 mmHg
What is the pressure in the capillaries?
20 - 40 mmHg
**except renal capillaries = 45 mmHg –> encourage filtration
What is the pressure in the vena cava?
4 mmHg
What are the 3 layers of blood vessels?
Tunica Intima
Tunica Media
Tunica Externa
What is the tunica intima?
Smooth frictionless inner layer
What is the tunica intima made of?
endothelium
basement membrane
thin connective tissue
What is the tunica media made of?
Smooth muscle
Elastic fiber
What is the tunica externe?
Thin layer of connective tissue
Which arteries are considered elastic arteries?
Pulmonary Trunk
Aorta
Major Branches
What is the composition of the tunica media in elastic arteries?
Thick
Elastin > Smooth Muscle –> stretch to absorb systolic volume of blood and recoil to return to original diameter
Describe the blood flow in elastic arteries
High Pressure
High Veolicity
Small Total Cross Sectional Area
Which arteries are considered muscular arteries?
Medium/small size arteries
What is the composition of the tunica media in muscular arteries?
Less elastin, more smooth muscle than elastic arteries –> distributes blood flow to arterioles throughout the body
What do arterioles/metarterioles do?
Act as controller to direct blood to capillary beds @ slow/low pressure flow
How does the pressure change as it enters arterioles to as it leaves arterioles?
Enters ~ 90 - 100 mmHg
Leaves ~ 25 - 35 mmHg
**largest drop in arterial pressures
What is the composition of the tunica media in arterioles?
Thin
Mostly smooth muscle
Minimal elastin
**regulate blood flow into capillary beds via pre capillary sphincters
Describe the blood flow in arterioles
Decreasing pressure
Decreasing velocity
Increasing total cross sectional area
What are the intrinsic controllers of arterioles?
Metabolic demands:
O2 Levels
CO2 Levels
What are the extrinsic controllers of arterioles?
Autonomic Nervous System:
Mostly Sympathetic Innervation
What are capillaries made of?
Single endothelial layer w/ basement membrane
NO tunica media or tunica externa
Describe blood flow through capillaries
Low pressure
Slow velocity
HUGE total cross sectional area
What is the function of capillaries
Site of respiration (gas exchange)
**any given moment 5% circulating blood in capillaries
Describe the composition of veins compared to arteries
Thinner more fibrous walls
Less elasin
Larger diameters
What is important about venous system in regards to blood volume?
Allows large blood volume fluctuations w/o dramatic blood pressure variations
What is a unique feature of veins?
1 way valves that help get blood back to the heart
**fuctions as muscle pump
What are vein valves formed by?
In-folds of tunica intima
How does the respiratory pump influence venous return/arterial pressures?
Changes will promote venous return:
Inspiration
“Muscular Pump” during exercise
How does inspiration promote venous return?
Transiently decrease right atrial pressure –> allows for increased filling
Venilation compresses IVC –> pushes more blood back into heart
How does the muscular pump during exercise promote venous return?
Combo of valves closing and contracting leg muscles compress blood toward heart
How is blood flow decree?
Volume per unit of time
What are the mechanical factors affecting blood flow?
Velocity
Pressure of blood
Laminar vs Turbulent flow
Resistance
How is velocity describe?
Distance per unit of time
How is velocity related to blood flow?
Directly related
**inversely related to TPR
How does pressure affected blood flow?
Pressure gradients; high –> low
What is laminar flow?
Smooth frictionless wall = smooth frictionless blood flow = increased blood flow
What is turbulent flow?
“Funny flow” = decreased blood flow
How is resistance related to blood flow?
Inversely related
**increased resistance = decreased blood flow –> less volume per unit of time
What is the most resistance in blood flow due to?
Length/diameter of blood vessel –> vasoconstriction and vasodilation
Viscosity of blood
How are viscosity and hematocrit related?
Viscosity will double if hematocrit increases from 40% - 60%
**polycythema/dehydration decreases fluid volume
How is total peripheral resistance (TPR) related to blood flow?
Inversely related:
↓ TPR = ↑ arterial blood flow to tissues and ↑ blood flow to venous system.
↑ TPR = ↓ arterial blood flow to tissues and ↓ blood flow to venous system
How does the sympathetic nervous system influence total peripheral resistance?
Blood vessels –> vasoconstriction/vasodilation
Heart –> increase HR/contractility
During a sympathetic fight or flight, which vessels are constricted and which are dilated?
Vasoconstriction = peripheral and Gi/GU blood vessels
Vasodilation = Skeletal muscle/Heart/CNS –> promotes action/stress response
Which sympathetic receptors are responsible for vasoconstriction/vasodilation?
Dilation = β2
Constriction = α1
How does the parasympathetic nervous system influence total peripheral resistance?
Blood Vessels = Vasodilation –> promote energy uptake/conservation
Heart = Atria ONLY –> decrease HR/contractility
Do parasympathetics innervate ventricles?
NO
Where are baroreceptors located?
Aorta
Carotid Sinus
How do baroreceptors (stretch receptors) influence total peripheral resistance if there is an increased stretch (↑ BP)?
↑ parasympathetic output
↓ sympathetic output
NET: ↓cardiac output (↓HR, ↓contractility) and ↑ systemic blood vessel dilation
How do baroreceptors (stretch receptors) influence total peripheral resistance if there is an increased stretch (↓ BP)?
↓ parasympathetic output
↑ sympathetic output
NET: ↑cardiac output (↑HR, ↑contractility) and ↓ systemic blood vessel dilation
How do the arterial chemoreceptors influence total peripheral resistance?
Major role is in respiratory rate
BUT they can vasodilate/vasocontrict blood vessels
What is compliance?
Ability of blood vessel to stretch per give increase of blood pressure
Describe the compliances of blood vessels
Veins = more compliant than aorta
Aorta = more compliant than arterioles
What is elastance?
Ability of blod vessel to return to original diameter
Which vessels have greater elastance?
Arterial > venous
Describe what happens to the arterial system if there is a large blood volume change
Can’t accommodate large blood volume change w/o large pressure increase
Describe what happens to the venous system if there is a large blood volume change
Reservoir system
Can accommodate large blood volume change w/ only small increase of pressure