Blood Flow And Control Of Blood Pressure Flashcards
What is the meaning of two pumps and one? And what provides the initial pressure to push blood through the vessels?
Blood flows through systemic and pulmonary circuits and the heart provides the initial pressure to push the blood through the vessels
What is pressure reservoir and how does it help maintain blood pressure?
Arteries elastic and muscular help maintain blood pressure and pressure reservoir
What are arterials surrounded by and how do they contribute to blood flow
Arterials are surrounded by vascular smooth muscle that are able to partially constrict/daily to vary blood flow (variable resistance: size, length,) 
Meta-arterials and anastomoses
- Meta-arterials are bypass of vessels through capillary beds that can be constricted or dilated by precapillary sphincters that can cause an increase or decrease in capillary circulation.
- anastomosis are the shunt vessels that allow blood to bypass around the capillary beds (arterials to veins)
Capillaries
Are only one Cell thick endothelium only and are the site of tissue gas exchange
Venules
Venules are similar to capillaries at distal end of capillary beds but get larger and can start to have a smooth muscle around them. 
Veins
Are larger, more superficial and compliant then arteries may have valves and contain the largest volume of blood 60% of blood reservoir 
How does blood pressure initiate
Through ventricular contraction which is periodic
How is blood pressure achieved by a pump that is essentially repeatedly turning off and on
Elastic recoil of arteries and peripheral resistance of arterioles
Kinetic energy created during Ventricular systole
Is one of the two ways blood pressure is maintained. Kinetic energy a.k.a. elastic recoil is transferred to the expanding walls of the aorta and stored as potential energy then released as kinetic energy again as the artery walls return to an unexpanded state (they recoil) ballooning effect allows for continuous blood flow through rest of vessels.
* also responsible for your pulse
Peripheral resistance in maintaining blood pressure
Peripheral resistance is one of two ways to maintain blood pressure. through contraction of vascular smooth muscles around the outside of the arterials.
* smooth muscles exist in a tonic state partially contracted that allows for both dilation and constriction for varying metabolic needs
How is blood pressure typically measured and what does it take into account ?
Blood pressure is typically measured through mean arterial pressure MAP
which takes into account the pressure difference between
(ventricular systole - diastole = pulse pressure ) 
MAP= diastolic pressure + (1/3 pulse pressure)
*whiteboard/ YouTube **
Why is mean arterial pressure only 1/3 of pulse pressure?
Because diastole lasts about twice as long as systole 
What are the four laws that dictate blood flow
Pressure, resistance, volume, flow
Define pressure gradient
There must be a difference in pressure for fluids to flow from areas of high pressure to low pressure (pressure)
How is pressure usually measured
Millimeters of mercury (mm Hg) or torr (1torr=1mmHg)
Define hydrostatic pressure
Fluid in a closed container exerts pressure on the walls of the container.
(Resistance)
* fluid will flow from high pressure to low pressure least path of resistance
[ flow is directly proportional to differences in pressure. P1-P2 = pressure gradient ] no difference = no flow
What does flow of blood depend on
The difference in pressures, this allows flow to happen under the driving pressure of a pump example the heart or passively through vasodilation
How does mean systemic pressure and mean arterial pressure compare when they move further away from the heart
They are directly proportional going from high pressure in the aorta and lower pressure as it moves away from the heart
Where is systolic and diastolic pressure measured
In the arteries and arterioles
Flow is inversely proportional to
Resistance (R), meaning that it opposes flow
Flow is directly proportional to 1/R
[^flow=decrease in resistance/ Decrease flow=^ in resistance]
Three things that are responsible for creating resistance of flow
- Radius (r)
- Length (L)
- Viscosity (n)
Poiseuilles law
Measuring the amount of resistance taking in consideration radius, length, and viscosity
R=8 L n / 🥧 r4
(8and 🥧 are constants so we can drop and simplify)
R= L n/r4
Looking at each variable of (R) individually
Length
^ length = ^ resistance :
Imagine trying to drink soda through short straw compared to a long straw, the short one is much easier. In the body the length of the blood vessel is relatively constant so this variable has a little effect on blood flow
Looking at each variable of (R) individually
Viscosity
^n=^R:
Keep the straws length constant and imagine drinking water compared to thick milkshake, the less viscous the water the much easier it is to drink. Bloods viscosity is determined by the ratio of red blood cells to plasma which is fairly constant
Looking at each variable of (R) individually
Radius
^r = less R
Now imagine drinking a milkshake with the same length of straw with a larger radius. It’s much easier as the radius increases.
*This is the factor that will largely determined resistance and blood flow because our bodies can and do bury the radius of blood vessels through there’s a dilation and construction.
*Very small changes in radius have a large effect on flow
Flow: change pressure/resistance
Bloodflow can change by altering the pressure differences and or resistance mostly through vessel radius 
Velocity of flow
(v measured in cm/min )
Speed of flow Depends on the amount/volume of blood being moved
(flow rate Q measured in L/min)
And the cross-sectional area of the tube it’s flowing through (A)
Mathematically: v=Q/A 
Velocity of flow
Vasodilation and vasoconstriction
- Vasoconstriction: less flow rate (Q) / ^velocity (v)
* vasodilation: ^ flow rate (Q) / low velocity
Why in the capillaries must blood flow rate be slow
Needs a higher cross-sectional area for gas exchange to happen this is accomplished by increasing the number of capillaries
(One aorta but a lot of capillaries therefore increasing cross-sectional area) 
Mean arterial pressure is primarily determined by
Cardiac output and peripheral resistance
If either heart rate or stroke volume increases then cardiac output and mean arterial pressure also increase
How can you maintain a relatively constant blood pressure MAP
By adjusting cardiac output or peripheral resistance
What are factors that affect MAP
Cardiac output( HR & SV [ preload {EDV & venous rerun } contractility {ca2+} Afterload )
Peripheral resistance: vasoconstriction vasodilation which are altered by ANS symp ans parasymp chemicals (ACh and Epi)
Peripheral resistance is regulated through
Variable Resistance of arterioles that account for 60% of peripheral resistance. Control is through local and systemic mechanisms
Local control , sympathetic reflex, hormones
Vasoconstriction vasodilation
Peripheral resistance local control
Intended to quickly match metabolic needs of the tissues, regulation of blood flow. local control can have a stronger overriding effect to remote ones.
Includes: myogenic auto regulation and paracrine signals
Myogenic auto regulation of local Peripheral resistance control
Vascular smooth muscle around arterioles have the ability to regulate its own state of contraction. Increased blood pressure makes the arterials constrict (opposite if regular)

Paracrine signals of local Peripheral resistance control
Include gases CO2, O2, NO
Active hyperemia: (from activity) as aerobic metabolism increases, O2 levels decrease while CO2 increase which dilates arteries increasing blood flow
Reactive hyperemia: increased concentration of NO, and CO2 and other paracrine molecules immediately trigger significant vasodilation and restore tissue blood flow the radius of the arterial gradually return to normal(an increase in tissue blood flow following a period of low perfusion due to occlusion is known as reactive hyperemia)
Sympathetic reflexes in peripheral resistance regulation through systemic mechanisms
Act to maintain mean arterial pressure and redistribute blood to various tissues across the body for a homeostatic needs example thermal regulation
Example of a sympathetic reflex works
SNS signals maintain vascular muscle tone around most systemic arterioles (but not all) which allows room for both vasoconstriction and vasodilation.
Sympathetic reflexes during SNS activation (systemic control) Epi and NE
Fight or flight response Epi and NE :
(NE higher affinity) binds to alpha receptors adrenergic ( most systemic arterioles) causing vasoconstriction
Epi binds to beta 2 receptors adrenergic ( vascular smooth muscle of heart, liver, skeletal muscle arterioles ) causing vasodilation
[beta 1 receptor on Autorythmic cells NE]
* there is no SNS innovation to these receptors, it’s solely due to epi-release
Hormones on Peripheral and Resistance (systemic)
Hormones have varying affects some simultaneously acting on other homeostatic mechanisms to maintain MAP.
Ex: atrial natriuretic hormone (ANP) and angiotensin ii I have both an effect on vasodilation/vasoconstriction, but also regulate excretion of ions and water by kidneys 
What are two other factors that are important for maintaining blood pressure besides elastic recoil and peripheral resistance
Distribution of blood in the systemic circuit and blood volume
Distribution of blood in the systemic circuit
Recall that most blood about 60% is in the veins as a blood reservoir. If blood pressure suddenly drops the sympathetic nervous system can constrict the veins (venoconstriction) and push the blood into circulation.
Therefore ^venous return=^ SV
Blood volume maintaining blood pressure (BV)
The circulatory system as a close circuit any addition or removal of blood will increase or decrease blood pressure.
- Increase in blood volume can occur through ingestion of food or liquids. The kidneys can control this to some extent urination ( slow response mechanism )
- decrease in blood volume can happen through blood loss or dehydration. The kidneys can slow fluid loss but not very effectively. Cardiovascular responses can help to some extent by increase heart rate and/or stroke volume, vasoconstriction (a fast response)
Nutrient demands of oxygen and glucose
Varies from different organs and tissues with metabolic needs and is distributed accordingly through mechanisms we talked about.
Total blood flow always equals cardiac output about 5 L per minute and vessels are arranged in a parallel circuit which means arterioles receive blood at the same time from the aorta
Total blood flow redistribution can happen through (mechanistic)
Meta-arterioles, increasing/decreasing arterial resistance, and modulation by ANS/hormonal input.
Example: at rest most blood flows to liver, kidneys and skeletal muscle about 20% of cardiac output each. When active blood flows to skeletal muscle increases four times to 85% of cardiac output
How much of cardiac output flows to the lungs same as Q of pulmonary vessels
5liters per minute
What are the two exceptions to the distribution of blood flow (have little neural input on control)
- Cerebral blood flow: remains nearly consistent, just about any cessation of oxygen or glucose supply to the brain will cause unconsciousness and or bring damage
- coronary blood flow: follows its metabolic demands more strictly the neural input and has additional local controls to maintain flow (myocardium uses 75% of o2 compared to 25% and other tissues)
What controls Organ perfusion through homeostasis a blood pressure
Micro control mechanisms are mainly controlled in the medulla oblongata with input from other parts of the brain what is referred to as a Cardiovascular and Control Center CVCC
How does the CVCC monitor MAP?
Through barrow receptors in the carotid artery (monitor BP going to the brain) and aorta (monitoring BP going to the rest of the body) constantly telling the brain the MAP is which is constantly and almost instantaneously making adjustments to all the micro controls HR, SV, PR ETC through baroreceptor reflex
If Vessel A constricts it will cause an overall increase in Mean arterial pressure as peripheral resistance increases an adjustmen must be made to bring down mean arterial pressure
- Barrow receptors detect the increase in Mean arterial pressure and a signal is sent to the medulla oblongata (efferent signals are sent to the heart):
- decrease in sympathetic input, increase in parasympathetic input> decrease in norepinephrine, increase in ACh release > decrease stimulation of alpha, beta1, beta2 adrenergic receptors by norepinephrine, increase stimulation of cholinergic muscarinic receptors by ACh> decrease in HR and force of contraction (decrease in CO > increase vasodilation > decrease MAP)
Three types of capillaries
- Continuous capillaries: make up most found in the body have a little space between endothelial cells allows passage of gases and ions between or through them paracellular, intercellular, or transcytosis** via vessels.
- Fenestrated capillaries: have larger pores between endothelial cells that allow higher volumes of fluids between the plasma and interstitial fluid located in the kidneys and small intestines
- Sinusoids have large gaps between cells up to five times larger than capillaries an incomplete basal lamina that allows passage of blood cells and plasma proteins. Found in bone marrow liver and spleen
What determines the density of capillaries
Density of capillary depends on typical metabolic requirements of the tissue think Forman function. More metabolic needs more blood means more capillaries 
Hydrostatic pressure
Pressure and Blood pushing from inside vesicles (Ph)
Osmotic pressure
‘Pull’ on fluids based on solute concentration
Colloid osmotic pressure
Type of osmotic pressure a.k.a. Oncotic pressure. Pulls on fluid by dissolve plasma proteins mainly albumin‘s (🥧)
Bulk flow
Mass movement of fluid due to hydrostatic and osmotic pressure gradients
Absorption
Bulk flow of fluid into capillaries from interstitial fluid
Filtration
Bulk flow of fluid out of capillaries into interstitial fluid
Recall that flow depends on a change in pressure, so pressure differences along the length of capillaries either
Deliver fluids (filter) or pick up (absorb) fluids,
*positive change in pressure equals filtration and negative change and pressure equals absorption
Hydrostatic pressure (Ph) decreases as
As blood moves from one end of the capillary beds to the other end
colloid osmotic pressure 🥧
does not change, plasma proteins normally stay in the plasma and are not found in interstitial fluid (or have a negligible effect)
Blood coming into capillary beds (arterial end)
Ph=32mmhg; 🥧=-25mmhg;
Pressure change = +7 mmhg
(same as net filtration occurs at the arterial end)
Blood leaving the capillary beds (Venous end)
Ph= 15mmhg;🥧=-25mmhg;
Pressure change =-10mmhg
(Same as net absorption occurs at venous end)
Somewhere along the middle of capillary beds
Ph=🥧; pressure change = 0 (same as no net flow)
What happens to blood pressure if Colloid osmotic pressure decreases
(Higher net filtration) Overall there is a net bulk flow of about 3 L of fluid leaving the blood and going to tissues. What happens to all that fluid? Luckily the lymphatic capillaries are there to absorb it as lymph and return it back to the general blood circulation! Otherwise tissue swell up causing edema
Cardiovascular diseases
The umbrella term describing problems of the heart and blood vessels. They are the number one cause of deaths worldwide. Myocardial infarction are 85%
Vessel Diseases include
Peripheral arterial disease, deep vein thrombosis, pulmonary embolism‘s etc.
Heart diseases include
Coronary heart disease (myocardial infarction #1) CHD or a coronary artery disease CAD arrhythmia, heart valve disorders, heart failure.
*one exacerbates another eg: peripheral arterial disease > increase risk of CHD , stroke, pulmonary embolism
Risk factors uncontrollable and controllable for heart disease
Uncontrollable genetics age and sex
Controllable diet activity weight smoking alcohol diabetes stress hypertension
Main causes of heart disease
Atherosclerosis hardening of the arteries, plaque builds up in coronary vessels that includes blood and oxygen supply to the heart. 6.7% of people 20+ years of age have coronary heart disease, 20% of deaths are people 65 years
Atherosclerosis is an inflammatory disease tied to the ratio of cholesterol CHL to Lipo proteins therefore my complex that makes CHL more soluble in plasma
HDL - C good cholesterol, LDL - C bad cholesterol. It’s the ratio of each other hi LDL can lead to atherosclerosis
Formation of atherosclerosis 3 steps
- Fatty streak formation:
- Stable fibrous plaque formation
- Vulnerable plaque formation
Hypertension categories/types
- Essential hypertension: or primary idiopathic 90% no identical cause other than hereditary but also associated with factors such as obesity salt and alcohol intake
- Secondary hypertension: has pathological causes such as endocrine and renal diseases
Hypertension is linked to
Blood vessel damage atherosclerosis, myocardial infarction, stroke, aneurysm, hydroxy of cardiac tissue due to an increase afterload leading to pulmonary Adema and congestive heart failure, renal failure, blindness, metabolic diseases such as diabetes and dementia
Treatments for hypertension
Aside from changing lifestyle habits include
•calcium channel blocker‘s that decrease heart contraction force, and increase vasodilation.
•Diuretics that decrease blood volume, •beta blockers that decrease the beta one receptor catecholamines stimulation,
•ace inhibitors that decrease angiotension a vasoconstrictor
