Lectures 16 & 17: Circulation Flashcards
What type of vessel does gas exchange occur?
capillaries
Are arteries or veins more compliant? (compliant: referring to the ability to stretch out and not want to recoil and push back on the blood)
veins
Which vessel is the least compliant?
A: infused 200mL blood, pressure rose 20mmHg
B: infused 200mL blood, pressure rose 30mmHg
C: infused 100mL blood, pressure rose 30mmHg
Vessel C because you infused the least amount and pressure rose a greater amount
What will happen to blood flow through the body if blood pressure drops too low?
it will decrease
Which component of RAAS directly increases TPR?
Ang II
Which component of RAAS increases intravascular blood volume?
Ang II & Aldosterone
What receptors are responsible for increased HR?
Beta 1
What receptors are responsible for vasoconstriction and venoconstriction?
Alpha 1
What is the function of arteries?
transporting oxygenated blood
What is the function of arterioles?
they act as valves for entry into capillaries
What is the function of capillaries?
gas and nutrient exchange
What is the function of venules?
collects blood from capillary
What is the function of veins?
Carry deoxygenated blood back to the heart
The walls of arteries have three layers. The layers are also called what?
Tunics
What is the innermost layer of the wall of arteries called?
Tunica interna (intima)
What does the tunica interna contain?
lining of simple squamous epithelium (endothelium), basement membrane, and layer of elastic tissue (internal elastic lamina)
What does the endothelium (of the tunica interna) line?
the entire CV system
What is the only tissue (referring to the tunica interna) that contacts blood?
endothelium
What is the tunica media (arteries)?
the middle, thickest layer of the wall of arteries
What does the tunica media contain?
elastic fibers and smooth muscle that extend circularly around the lumen
What is the tunica externa?
the outermost layer of the wall of arteries
What is the tunica externa composed of?
Mainly of elastic and collagen fibers
In muscular arteries, what separates the tunica externa from the tunica media?
an external elastic lamina composed of elastic tissue
What are the two types of arteries?
elastic arteries and muscular arteries
What is an example of an elastic artery?
the aorta
Elastic arteries have the largest what?
diameter
Where are elastic arteries found?
Tunica media
Which type of artery is capable of greater vasoconstriction and vasodilation to adjust blood flow?
muscular arteries
What do arterioles do?
carry oxygenated blood and empty into capillaries
________ and ________ control blood flow into capillary bed.
Metarterioles and precapillary sphincters
Capillaries are the site of what?
gas and fluid exchange with the tissues
What makes the capillary good for gas exchange?
its thin wall
What does the capillary consist of?
a layer of endothelium and underlying basement membrane
Why aren’t capillaries capable of vasoconstriction or vasodilation ?
Because they don’t have smooth muscle
What do venules receive from capillaries?
deoxygenated blood
Arterioles and venules have smooth muscle so they are capable of what two things?
vasoconstriction or vasodilation
True or False? Veins consist of the same three tunics as arteries.
True
The tunica interna and tunica media of veins are _________ than that of arteries and they have less elastic tissue and smooth muscle than arteries.
thinner
The tunica externa of veins is _______ than that of the tunica media.
Thicker
________ can hold more blood and act as a reservoir.
Veins
What do veins contain to prevent backflow of blood?
valves
What is the primary purpose of CV system?
blood flow
what is the formula for blood flow?
CO= MAP/TPR MAP= CO x TPR
Are CO, MAP, and TPR related?
Yes, you cannot change one without changing the other
What is blood pressure?
Blood pressure is the force exerted on the walls of the blood vessels by the blood
Blood flows though the body due to what?
a pressure gradient
What is the pressure in the arteries?
80-120mmHg
What is the diastolic pressure?
80
What is the systolic pressure?
120
What two things does MAP represent?
- average arterial pressure during a single cardiac cycle
2. the pressure gradient in the systemic circulation since the pressure in the right atrium is nearly 0 mmHg
MAP formula
Mean (MAP) = DBP + 1/3(SBP-DBP) =93
What is the mean pressure in capillaries?
17mmHg
What is the pressure in the veins and right atrium?
0 mmHg
What is the major driving force for blood flow through the systemic circulation?
MAP
Pressure gradient in the pulmonary circulation is __________.
Lower
What is the pressure in the pulmonary artery?
8-25mmHg
What is the pressure of capillaries in the pulmonary system?
7mmHg
How do you calculate/determine pulse pressure?
SBP-DBP
What two factors affect pulse pressure?
Stroke volume and compliance
Greater stroke volume results in _____ pulse pressure rise with each heart beat.
greater
Lower compliance of artery results in a __________ pulse pressure rise with every beat.
greater
True or false? Pulsations are dampened further down the vascular tree.
True
Do arterioles and capillaries experience significant pulsations?
No
What is TPR also referred to as?
SVR (systemic vascular resistance)
What is TPR?
the resistance to blood flow through all of the vasculature in the body
What does TPR represent?
arterial resistance because most of the resistance is in the arterial vasculature since the venous vasculature is so compliant
What happens to the TPR as arterial vessels vasoconstrict?
TPR increases
What happens to the TPR as arterial vessels vasodilate?
TPR decreases
Resistance=
Resistance= 1/diameter^4
What helps to push blood in the veins towards the heart and increases venous return?
Rhythmic contraction of skeletal muscle
What prevents backflow during muscular relaxation?
valves
What happens to abdominal pressure and intrathoracic pressure during inspiration?
abdominal pressure increases and intrathoracic pressure decreases
What effect does the respiratory pump have on venous return?
increases venous return due to increased pressure gradient
What effect does the activation of RAAS have on blood pressure?
increases it
what is the Renin substrate also called? And from where is it secreted?
angiotensinogen; liver
Where is AT1 found?
brain, kidney, myocardium, peripheral vaculature, adrenal cortex
Why is AT1 important?
helps regulate blood pressure
Where is AT2 found?
adrenal medullary tissue, uterus, brain
Does AT2 have an effect on blood pressure?
no
What does Ang II do?
causes the kidneys to reabsorb salt and water in 2 ways
What 2 ways does Ang II cause the kidneys to reabsorb salt and water?
- acts directly on the kidneys to cause salt and water reabsorption
- stimulates adrenal glands (cortex) to secrete aldosterone
What does aldosterone do?
increases salt and water reabsorption in kidneys
Ang II causes what?
vasoconstriction
Ang II stimulates what 3 things?
- SNS
- thirst centers in the brain
- ADH release from posterior pituitary
What does Ang II inhibit?
renin release from kidney
Where is ACE most prominent?
in capillary wall of lung
Can Ang II be produced by other systems that function without ACE?
yes
What is ADH also called?
vasopressin
Where is ADH released from?
posterior pituitary gland
What triggers ADH release?
decreased blood volume and/or an increase in osmolarity
What effect does ADH have on blood pressure?
it increases it & causes vasoconstriction
Where does ADH act?
on the kidneys promoting reabsorption of water (NOT salt)
What are the 3 ADH receptors?
V1a, V1b, and V2
Describe the ADH receptor V1a
mediates vasoconstriction effects
Describe the ADH receptor V2
mediates anti-diuretic effect in kidneys
What is ANP also called?
ANF
What does ANP stand for?
Atrial natriuretic peptide (factor)
What is ANP released by?
cells of atria in response to increased stretch
What affect does ANP have on blood pressure?
decreases it and causes vasodilation
Where does ANP act and what does it cause?
acts on the kidneys and promotes loss of salt and water in urine
What does ANP suppress?
secretion of renin, aldosterone, and ADH
What is BNP also called?
BNF
Where is BNP released from?
ventricles in response to pressure & volume overload
What effect does BNP have on blood pressure?
it decreases it
The ANS subdivides into what?
SNS and PNS
What does the SNS play a role in?
controlling circulation
Which vessels does the SNS NOT innervate?
capillaries, precapillary sphincters, and metarterioles
What causes constriction of most vessels of the body via alpha-1 adrenergic receptors
SNS
what does stimulation of B2 receptors cause?
vasodilation
What will Beta-1 stimulate?
increased heart rate and contractility
Generalized activation of the SNS will have what effect on blood pressure and organ perfusion?
increase blood pressure and decrease organ perfusion (except in the heart and brain due to vasoconstriction of most of the vessels in the body)
True or false? SNS and PNS innervate the heart.
True
Are the majority of blood vessels innervated by the PNS?
No
What effect does the PNS have on heart rate and contractility?
decreases both
What regulates the ANS?
vasomotor center in the medulla
What are baroreceptors and where are they located?
stretch receptors that are located in walls of large arteries (carotid artery and aortic arch)
If arterial pressure increases, stretching of baroreceptors send info to vasomotor control center which then results in what?
increased TPR and CO
What are the 2 chemoreceptors that are mentioned in the notes?
carotid bodies and aortic bodies
What do chemoreceptors sense?
decrease in O2 content and an increase in CO2 and H+ content
If blood pressure decreases, what happens to blood flow through the chemoreceptors? what happens next?
decreases; then they become stimulated and excite the vasomotor center resulting in increased blood pressure
Do atria and pulmonary artery contain stretch receptors?
yes & they are also called low pressure receptors
Low pressure receptors are optimal for what?
detecting changes in pressure in low pressure areas & important in minimizing changes in pressure in response to volume changes
