Unit 10: Blood Vessels/ Blood Pressure Flashcards
What is the equation for Flow Rate?
Pressure/ Resistance
What is the relationship between resistance and flow rate?
An increase in resistance leads to a decrease in flow rate
Starting from the right atrium, name the structures that carry blood to organs.
Artery, arteriole and capillaries, which rejoin to form venules, and then veins which lead back up to the heart.
What structures make up microcirculation?
Arterioles, capillaries and venules
What 2 fibers make up arteries?
Elastin and Collagen
What are the 2 main functions of arteries?
- Act as rapid-transit pathways
- Act as a pressure reserve to provide a driving force for the blood when the heart is relaxing
What is Blood Pressure?
-The force exerted by the blood against a vessel wall, which is dependent on the volume of blood within the vessel and it’s compliance (how much it can stretch)
What is the systolic pressure?
The pressure exerted on the arteries when blood is ejected into them during systole, averaging 120 mmHg.
What is the diastolic pressure?
The minimum pressure within the arteries when blood is draining off into the rest of the vessels during diastole, averaging 80 mmHg.
What is a Sphygmomanometer?
Measures changes in arterial pressure throughout the cardiac cycle using this pressure measuring device.
What is the Pulse Pressure?
-The difference between the Systolic and Diastolic pressures
What is Mean Arterial Pressure?
- Diastolic Pressure + (1/3 the pulse pressure)
* Average pressure forcing blood into the tissues
Properties of Arterioles?
- ->MAJOR RESISTANCE VESSELS
- Have a pressure of 37mmHg
- Lower pressure of the arterioles compared to the heart open valves and encourages the flow of blood into the organs and tissues.
- Arteriole walls contain very little elastic tissue, but are highly innervated with smooth muscle tissue.
How does smooth muscle innervate arterioles?
When the arteriole contracts, the circumference of the arteriole decreases, which increases the resistance of the vessel and decreases blood flow- called vasoconstriction.
What is Vasodilation?
-Refers to the enlargement in the circumference and radius of a vessel as smooth muscle relaxes.
What is Vascular tone?
-Arterioles are generally in a state of minor-vasoconstriction, which establishes a baseline of arteriole resistance.
What is the relationship between Arteriolar radius and Blood Flow?
The greater the radius, the greater the blood flow as their is less resistance.
What is active Hyperemia?
- Local arteriolar vasodilation
* Increases blood flow*
How do endothelial cells participate as vasoactive mediators?
-Release chemical mediators that play a key role in locally regulating arteriole calibre.
What is Nitric Oxide’s (NO) effect on blood vessels?
- Causes local arteriolar VASODILATION as it induces relaxation of the smooth muscle around arterioles.
- Inhibits Ca2+ that causes contractions
What is endothelian’s impact on blood vessels?
Causes vasoconstriction
What is Histamine’s release on blood vessels?
Causes Vasodilation
-is released when tissue or organs are damaged, and promotes vasodilation, aka an increase in blood flow to these tissues
What is the effect of heat on blood vessels?
Vasodilation
What is the effect of cold on blood vessels?
Vasoconstriction
What is the blood vessel response to shear stress?
Make endothelial cells release NO, which in turn leads to vasodilation in blood vessels
*Increase is arteriolar diameter= decrease in sheer stress
What is a myogenic response?
-A response generated by the muscles
What is the blood vessel response to an increase in stretching, and well as a reduction in stretching?
Vasoconstriction, and vasodilation
Once a blockage is removed, why does blood flow to the area that was previously most deprived?
The arteriolar walls are widely dilated due to reactive hyperemia, so blood flows easiest to these areas first.
What is Autoregulation?
-Local arteriolar mechanisms that keep tissue blood flow fairly constant despite wide deviations in blood pressure.
What are the two main extrinsic controls affecting arteriolar radius?
- Neural/ hormone influences
* Mainly the sympathetic nervous system
Increased sympathetic activity= ___________
Vasoconstriction
Decreased sympathetic activity = ____________
Vasodilation
What is total peripheral resistance?
The total resistance offered by all systemic peripheral vessels together
What is the relationship between MAP, CO and TPR?
Mean arterial pressure= cardiac output x total peripheral resistance
What is Norepinepherine’s effect on blood vessels?
- Released by sympathetic nerve fibers
- Binds alpha 1 adrenergic receptors on arteriolar smooth muscle
- ->Produces vasoconstriction
Why can’t vasoconstriction occur in the brain?
-The brain doesn’t have alpha 1 receptors, so it can’t bind norepinepherine, thus it can’t cause vasoconstriction.
True or False- Outside controls, such as skeletal/ cardiac muscles override sympathetic vasoconstriction.
True.
Is there parasympathetic control in the blood vessels?
NO, only a decrease in sympathetic activity which causes vasodilation
*exception being parasympathetic stimulation of the penis and clitoris.
What region of the brain controls sympathetic output to the arterioles?
The cardiovascular control center in the medulla of the brain stem.
What is the function of the hypothalamus ?
Regulates blood flow to the skin & adjusts heat loss to the environment.
What is epinepherine’s effect on blood vessels?
Binds beta2 and alpha1 receptors (highest affinity for beta2)
–>Causes vasoconstriction
What is vasopressin’s effect on blood vessels?
Involved in maintaining water balance through urine formation
–>Vasoconstrictor
What is angiotensions II’s effect on blood vessels?
- Important in regulating bodily salt
- Vasoconstrictor
What is the main method capillaries exchange material between the blood and tissues?
-Diffusion
What is the diameter and thickness of capillary walls?
Diameter of capillaries is 7um and the thickness of them is 1um.
True or false- blood moves the slowest in the capillaries, and has the least resistance here.
True
What are capillary pores?
Permit passage of water soluble substances
*O2 and CO2 readily pass through the pores by dissolving in the lipid bilayer.
What is a metarteriole?
Metarterioles run between an arteriole and venule.
*Contain smooth muscle, which have precapillary sphincters, each that arise to begin a capillary from a metarteriole.
What is the role of precapillary sphincters?
- Not innervated, but have a high degree of myogenic activity.
- Sensitive to local changes, and act as a stopcock for blood flow.
What occurs to blood vessels with an increase in CO2?
As muscle metabolism increases, there is a greater need for O2, therefore a greater production of CO2, therefore the precapillary sphincters RELAX.
–.VasoDILATION
What components make up ECF?
20% plasma
80% interstitial fluid
-Interstitial fluid allows for passage exchange of materials
What are the 2 ways in which materials are exchanged between blood and tissues?
- Passive diffusion down concentration gradient.
2. Bulk Flow
What is Bulk Flow?
A volume of protein-free plasma filters out of the capillary (leaks out), mixes with the surrounding interstitial fluid and is then reabsorbed by the capillaries.
-Ultrafiltration & Reabsorbtion
What is Ultrafiltration?
Pressure inside the capillary is greater than outside –> pushes fluid out of the capillary
*Most proteins are trapped, like a sieve.
What is Reabsorbtion?
Pressure outside the capillary is greater than inside–> pushes fluid back into the capillary
What are the 2 forces pushing fluid OUT of the capillary?
- Capillary Blood Pressure
2. Interstitial fluid- colloid- osmotic pressure
What are the 2 forces pushing fluid INTO the capillary?
- Plama-colloid osmotic pressure
2. Interstitial Fluid Hydrostatic pressure
Net Pressure Change relationship?
Net Pressure exchange= Outward pressure- inward pressure
True or False- more fluid is filtered OUT of the capillaries than reabsorbed.
True.
*Extra fluid filtered out circulates the lymphatic system, called lymph.
How does lymph circulate?
Contraction of smooth and skeletal muscle.
What are the functions of the lymphatic system?
- Return of excess filtered fluid
- Defense against disease
- Transport of absorbed fat
- Return of filtered protein
What is Oedema?
-Swelling of tissues due to excess interstitial fluid.
What is the driving force for blood from the veins to be taken up to the heart?
Pressure difference between the veins and right atrium propels blood upward.
–>Large diameter of veins= little resistance
Why are veins called capacitance vessels?
They are blood reservoirs (can store lots of blood not needed)
What is venous capacity?
-Refers to the amount of blood the veins can accommodate (due to stretch and pressure)
What is the pressure of venous blood returning to the heart?
17mmHg
-If atrial pressure elevates, the blood flow is decreased and can be fatal!
How does sympathetic stimulation impact venous return to the heart?
Vasoconstriction, therefore an elevated blood pressure- fast drive of blood to the right atrium
What is the skeletal muscle pump?
Skeletal muscle contraction near large veins compresses the veins, increases venous pressure and blood pump.
Counteracting the effects of gravity on blood pressure?
–>Pooling of blood in the lower leg so venous capacity is reduced, as well as venous flow to the heart. The marked capillary pressure causes excess fluid out of the capillary beds, thus causing oedema of the feet and ankles.
What are venous valves?
Valves within veins that ensure blood stays unidirectional so it doesn’t move back into the tissues
What are Varicose veins?
The venous valves stop working, and can’t support the column of blood above them
What is the respiratory pump?
–Pressure difference from within the chest promotes increased venous return- which results from respiratory activity.
What occurs to the venous valves during venous return?
AV Values are pulled down, enlarging the atrial cavities.
*Negative pressure in the ventricles promotes blood to get “sucked in” to the atria.
What type of receptor monitors mean arterial pressure?
Baroreceptors within the circulatory system
–changes trigger a baroreceptor reflex which restores the circulatory to 120/ 80 mmHg
What and where are the most important mechanical barorecetors located?
- Carotid Sinus and Aortic Arch
- ->Action potentials generated by these receptors are sent along an afferent pathway to the cardiovascular control center in the medulla of the brain stem–> impacts the autonomic system!
What is hypertension?
Blood pressure is too high
–>Once baroreceptors are exposed to high elevated blood pressure, thy ADAPT to work at this blood pressure.
What are some of the common effects of hypertension?
- Congestive heart failure
- heart attacks
- stroke
- renal failure
- spontaneous hemorrhaging
What is Hypotension?
-Blood pressure is too low (100/60)
What is Orthostatic Hypertension?
Insufficient compensation to the gravitational shift of when a person lies down and then stands up
–>blacking out or fainting
What is Circulatory Shock?
-Blood pressure falls so low that adequate supply to the tissues cant be maintained.
What is Hypovolemic Shock?
-caused by a huge drop in blood volume
What is Cardiogenic shock?
-caused by a weakened heart’s failure to pump blood adequately
What is Vasogenic shock?
-Caused by widespread vasodilation by the presence of vasodialator substances
What is Neurogenic shock?
A loss of sympathetic vascular tone, leading vasodilation aka less movement of blood
What is Irreversible Shock?
- ->A point may be reached at which blood pressure continues to drop rapidly because of tissue damage, despite vigorous therapy.
- ->Can lead to cardiac arrhythmia
What is myocardial toxic factor?
–>Released from the blood deprived pancreas, and further weakens the heart (toxic) during irreversible shock
Conscious initiation of muscle contraction is controlled by?
The cerebral cortex
Chemoreceptors respond to rising H+/CO2 by?
An increase in H+ means there is an increase in CO2 in the blood and a decrease in pH, and it is producing carbonic acid.
–>The respiratory center (in the medulla) sends nervous impulses to the external intercostal muscles and the diaphragm, to increase breathing rate and the volume of the lungs during inhalation.
–>An increase in CO2 leads to hyperventilation, and along with that is vasodilation of blood vessels.
Which vessels contain the highest percentage of total blood volume?
Systemic Veins
*Veins are blood reservoirs
