Module 1 - Vascular System 1.1-1.4 Flashcards
Blood flow through the vascular system results from __________ created by the heart.
Blood flow through the vascular system results from pressure gradients created by the heart.
The rate of blood flow can be calculated using what equation?
Bloodflow = change in pressure (ΔP) / resistance (R)
The pressure gradient present across the systemic circuit arises from the difference in pressure between the _____ (leaves the left ventricle) and the ________ (entering the right atrium).
The pressure gradient present across the systemic circuit arises from the difference in pressure between the Aorta (leaves the left ventricle) and the Vena Cava (entering the right atrium).
Aortic pressure is equal to the ________ which is about 90mmHg
Aortic pressure is equal to the Mean Arterial Pressure (MAP) which is about 90mmHg
Pressure in the vena cava is equal to the _________ which is about 0mmHg
Pressure in the vena cava is equal to the Central Venous Pressure which is about 0mmHg
How is the pressure gradient of the systemic circuit determined and what does it equal?
Determined by:
Mean arterial pressure - Central Venous Pressure = 90mmHg
The pressure gradient across the pulmonary circuit arises from the difference in pressure between the ________\_
Pulmonary arterial pressure is about 15mmHg and pulmonary venous pressure is about 0mmHg. Thus the pressure gradient in the pulmonary circuit is equal to about _______
The pressure gradient across the pulmonary circuit arises from the difference in pressure between the pulmonary arteries and veins.
Pulmonary arterial pressure is about 15mmHg and pulmonary venous pressure is about 0mmHg. Thus the pressure gradient in the pulmonary circuit is equal to about 15mmHg
Under normal circumstances, blood flow through the systemic circuit _______ to blood flow through the pulmonary circuit, despite differences in both pressure gradients and resistance.
Under normal circumstances, blood flow through the systemic circuit remains equal to blood flow through the pulmonary circuit, despite differences in both pressure gradients and resistance.
What three factors affect resistance to blood flow?
Which is the most influential?
- Vessel Radius
- Vessel length
- Fluid viscosity
Vessel radius is the major determinant of resistance to blood flow.
Resistance is inversely proportional to _______
Resistance is inversely proportional to the fourth power of the radius
R α 1/r4
A small change in the radius produces a big change in _______ and thus in _____
A small change in the radius produces a big change in resistance and thus in bloodflow
Vessel radius is regulated at the level of the _____, which can be:
- _______ which decreases the radius and increases resistance
or
- _________ which increases radius and decreases resistance
Vessel radius is regulated at the level of the arterioles, which can be:
- Vasocontricted which decreases the radius and increases resistance
or
- Vasodilated which increases radius and decreases resistance
Vessel length is proportional to _______
Vessel length is proportional to Resistance
ie: an increase in vessel length results in a proportional increase in resistance
Fluid viscosity is related to the _____\_of the fluid; an increase in viscosity results in an ______\_ in resistance
Fluid viscosity is related to the thickness of the fluid; an increase in viscosity results in an increase in resistance
The combined resistance of all blood vessels within the systemic circuit is called __________
Total peripheral resistance
Within the systemic circuit, blood flow is equal to _____, the pressure gradient is equal to ________ and resistance is equal to ________
Thus we have the following two equations:
Bloodflow = change in pressure / resistance
CO = MAP / TPR
Within the systemic circuit, blood flow is equal to Cardiac output (CO), the pressure gradient is equal to Mean Arterial Pressure (MAP) and resistance is equal to Total Peripheral Resistance (TPR)
Thus we have the following two equations:
Bloodflow = change in pressure / resistance
CO = MAP / TPR
What are the two major functions of Arteries?
- Rapidly transport blood away from the heart towards the arterioles and capillaries
- Serve as a pressure reservoir
Surrounding the endothelial cell layer of the arteries is a thick wall composed of ______ and ______
Surrounding the endothelial cell layer of the arteries is a thick wall composed of Smooth Muscle and Connective Tissue
The connective tissue layer of arteries contains:
- ________
- ________
Which provide elasticity and strength
The connective tissue layer of arteries contains:
- elastin - elasticity
- collagen fibres - strength
Having elastin and collagen in the CT layer of arteries allow for the arterial walls to _____ to accommodate increased volumes during cardiac _____ and to slowly relax during cardiac _____
Having elastin and collagen in the CT layer of arteries allow for the arterial walls to expand to accommodate increased volumes during cardiac systole and to slowly relax during cardiac diastole
The elastic recoil provided by elastin in the CT of arteries provides __________
The elastic recoil provided by elastin in the CT of arteries provides continuous blood flow through the systemic circuit throughout the cardiac cycle
Arteries are “low compliance” vessels and thus are considered __________
- compliance*- measure of how pressure changes with changes in volume
- low-compliance*- small change in volume = large change in pressure
Arteries are “low compliance” vessels and thus are considered pressure reservoirs
Arteries serve as pressure reservoirs: (Top) What happens as blood flows into arteries during systole? Why?
(Bottom) What happens as blood flows out of the arteries during diastole? How is blood moved through the vasculature during diastole?
Arteries serve as pressure reservoirs: (Top) As blood flows into the arteries during systole, the arterial walls are stretched outward and volume increases. This occurs because the pressure on the blood in the left ventricle is greater than that in the arteries. (Bottom) As blood flows out of the arteries during diastole, the arterial walls recoil inward and volume decreases. During diastole, blood is moved through the vasculature due to the elastic recoil of the arteries as the aortic valve is closed.
Arterial blood pressure is _________\_
- How does it vary with the cardiac cycle?
Arterial blood pressure is the pressure of the blood in the aorta
- Systolic blood pressure is the maximum pressure in the aorta during cardiac systole
- Diastolic blood pressure is the minimum blood pressure in the aorta during cardiac diastole. DOES NOT EQUAL 0mmHg
Arterial blood pressure is used as a measure of _______ and is indirectly measured using a sphygmomanometer:
Arterial blood pressure is used as a measure of Cardiovascular Function
What is happening at each of the numbers on the graph of sphygmomanometry:
- Cuff pressure is greater than 120mmHg and exceeds BP throughout the cardiac cycle = __________ =__________\_
- When Cuff pressure is between 120 and 80mmHg:
- ______________
- ______________
- Intermittent sounds are heard because of _____________\_
- The last sound is heard at __________\_
- When cuff pressure is less than 80mmHg and is below bp throughout the cardiac cycle:
- _______________\_
- __________________
What is happening at each of the numbers on the graph of sphygmomanometry:
- Cuff pressure is greater than 120mmHg and exceeds BP throughout the cardiac cycle = no blood flows through the vessel = no sound is heard because of no flow
- When Cuff pressure is between 120 and 80mmHg:
- blood flow through vessel is turbulent whenever bp exceeds cuff pressure
- The first sound is heard at peak systolic pressure
- Intermittent sounds are heard because of turbulent spurts of flow as blood pressure cyclically exceeds cuff pressure
- The last sound is heard at minimum diastolic pressure
- When cuff pressure is less than 80mmHg and is below bp throughout the cardiac cycle:
- blood flows through the vessel in smooth laminar fashion
- No sound is heard because of uninterrupted, smooth laminar flow
How is pulse pressure calculated?
By subtracting the diastolic pressure from the systolic pressure
eg:
120/80 pulse pressure = 120-80 = 40
What value can be estimated using the values for diastolic pressure and pulse pressure?
What is the equation?
Mean Arterial Pressure (MAP)
MAP=diastolic pressure + 1/3pulse pressure
eg: individual with arterial bp of 120/80mmHg, pulse pressure would be 40mmHg and MAP would be 93mmHg
Arteries branch into _____ when they reach the organ they are supplying
Arterioles
The largest decrease in pressure occurs in which blood vessels?
Arterioles
Among the various blood vessels, which supply the greatest resistance? By how much?
Arterioles
>60% total peripheral resistance
Changes to the radius of the arterioles are regulated to achieve two purposes:
- to distribute to individual ________\_, and
- to ______________\_.
Changes to the radius of the arterioles are regulated to achieve two purposes:
- to distribute _cardiac outpu_t to individual capillary beds, and
- to regulate mean arterial pressure (MAP).
Arteriolar radius is dependent upon the state of contraction of the ________\_ in the arteriole wall.
Arteriolar radius is dependent upon the state of contraction of the smooth muscle in the arteriole wall.
What does Arteriolar tone refer to?
Refers to the state of partial constriction under basal conditions (i.e in the absence of other influences) which establishes the base-line arteriolar resistance
What two factors are responsible for arteriolar tone?
- myogenic activity of arteriolar smooth muscle ie self-induced contractile activity
- Continuous release of norepinephrine by sympathetic fibres
What is Vasoconstriction?
Increased contraction that serves to decrease arteriolar radius
What is vasodilation?
Decreased contraction (relaxation) of circular smooth muscle which increases arteriolar radius and leads to decreased resistance and increased flow through the vessel
Changes in arteriolar radius are regulated by both _____ and _____ mechanisms.
Changes in arteriolar radius are regulated by both intrinsic and extrinsic mechanisms.
Factors that influence level of contractile activity of arteriolar smooth muscle fall into two categories:
- Intrinsic (local) controls - important in determining _________ depending of the metabolic needs of individual capillary beds
- Extrinsic controls - important in regulation of _______
- Intrinsic (local) controls - important in determining the distribution of Cardiac output by altering blood flow patterns
- Extrinsic controls - important in regulation of blood pressure
Provide an example of how intrinsic controls alter the distribution of cardiac output:
(Consider exercise)
During exercise, blood flow to the heart, skeletal muscles, and skin is increased, whereas blood flow to the digestive tract, liver, kidneys, and bone is decreased
Intrinsic mechanisms are regulated by ________\_, many of which result from _______\_
Intrinsic mechanisms are regulated by local chemical factors, many of which result from local metabolic changes
Define Active Hyperaemia
Active hyperaemia refers to an increase in blood flow in response to an increase in metabolic demand, such as during exercise.
What does Reactive Hyperaemia refer to?
Reactive hyperemia refers to an increase in blood flow in response to a previous reduction in blood flow, such as following a blood vessel occlusion
Local metabolic changes that would result in Active hyperaemia (increases in blood flow through arteriolar vasodilation) include the following:
- decreased concentrations of _____
- increased _____\_
- increased concentrations of ______\_
- increased concentrations of _______\_
- increased concentrations of _______\_
- increased concentrations of _______\_
- increased concentrations of _______\_
- decreased concentrations of oxygen (O2)
- increased osmolarity
- increased concentrations of carbon dioxide (CO2)
- increased concentrations of hydrogen ions (H+)
- increased concentrations of potassium (K+)
- increased concentrations of adenosine
- increased concentrations of prostaglandins
What are two well-known vasoactive (acting on vessels) mediators?
- nitric oxide (NO), which causes vasodilation, and
- endothelin, which causes vasoconstriction.
During an allergic reaction or injury, the local chemical factor _______ is secreted from CT cells and leukocytes and acts directly on arteriolar smooth muscle to cause vasodilation
During an allergic reaction or injury, the local chemical factor histamine is secreted from CT cells and leukocytes and acts directly on arteriolar smooth muscle to cause vasodilation
Intrinsic mechanisms are regulated by ________, including temperature changes, shear stress, and the myogenic response.
Intrinsic mechanisms are regulated by local physical factors, including temperature changes, shear stress, and the myogenic response.
An example of intrinsic control on arteriolar resistance is temperature. What are the results of temperature changes:
An increase in temperature results in arteriolar ________, whereas a decrease in temperature results in arteriolar _________
An example of intrinsic control on arteriolar resistance is temperature. What are the results of temperature changes:
An increase in temperature results in arteriolar vasodilation, whereas a decrease in temperature results in arteriolar vasoconstriction
What is Shear stress?
What is the consequence of an increase in shear stress?
Shear stress is the force on the endothelial cells in response to blood flow.
An increase in shear stress results in the release of NO from endothelial cells, which results in arteriolar vasodilation.
Explain the myogenic response as an intrinsic control mechanism of arteriolar resistance.
What is the myogenic response to an increase in blood pressure?
The myogenic response is: the response of arteriolar smooth muscle to stretching.
An increase in blood pressure causes stretching of the arteriolar wall, which subsequently results in vasoconstriction to increase the resistance and decrease the blood flow.
Extrinsic mechanisms regulate ___________ through which two systems?
Extrinsic mechanisms function to regulate mean arterial pressure (MAP) and involve both the nervous and endocrine systems.
Extrinsic mechanisms function to regulate mean arterial pressure (MAP) and involve both the nervous and endocrine systems.
All arterioles are under which branch of the nervous system (with the exception of the erectile organs in the reproductive system)
With the exception of the erectile organs in the reproductive system, which are innervated by the parasympathetic nervous system, all other arterioles are under the control of the sympathetic nervous system.
The sympathetic nervous system releases the neurotransmitter norephinephrine, which binds to ______\_ receptors present in the smooth muscle cells of most arterioles to cause ________.
Note: There are NO a-1 receptors in the smooth muscle cells of the brain
The sympathetic nervous system releases the neurotransmitter norephinephrine, which binds to alpha-1 (α-1) adrenergic receptors present in the smooth muscle cells of most arterioles to cause vasoconstriction.
The ______\_ nervous system innervates the adrenal medulla and causes release of two neurohormones: _______ and ________.
Both of these neurohormones bind to a-1 receptors to cause vasoconstriction
The sympathetic nervous system innervates the adrenal medulla and causes release of two neurohormones: norephinephrine and epinephrine
Both norepinephrine and epinephrine bind to _____\_to cause vasoconstriction. However, epinephrine also binds to ______\_ receptors located in the smooth muscle cells of the arterioles supplying _____and _____\_ muscle, resulting in vasodilation
Both norepinephrine and epinephrine bind to α-1 receptors to cause vasoconstriction. However, epinephrine also binds to beta-2 (β-2) receptors located in the smooth muscle cells of the arterioles supplying skeletal and cardiac muscle, resulting in vasodilation
Two other hormones released from the endocrine system are involved in the regulation of arteriolar radius:
- _______ and
- _______
Two other hormones released from the endocrine system are involved in the regulation of arteriolar radius:
- vasopressin and
- angiotensin II
- Vasopressin is secreted from the ________\_ and is involved in the maintenance of _________.
- Angiotensin II is part of the _______\_system (RAAS) and is involved in the maintenance of _______\_.
- Both vasopressin and angiotensin II are secreted following decreases in blood volume and cause __________.
- Vasopressin is secreted from the posterior pituitary and is involved in the maintenance of water balance.
- Angiotensin II is part of the renin-angiotensin-aldosterone system (RAAS) and is involved in the maintenance of salt balance.
- Both vasopressin and angiotensin II are secreted following decreases in blood volume and cause vasoconstriction.
The following flow chart summarizes the intrinsic and extrinsic mechanisms that influence arteriolar radius and, thus, vascular resistance.
- Total peripheral resistance depends on ______ and ________
- Blood viscosity is primarily dependent on the number of _____
- Arteriolar Radius depends on both _____ and _____ control
- Local (intrinsic) control (local changes acting on the ________ in the vicinity) mechanisms include:
- Response to _______
- ________ responses to stress - plays minor role in active and reactive hyperaemia
- Application of _____/_____ - therapeutic
- _______ release (injury/allergic response)
- Extrinsic control mechanisms are important in regulation of ______ and include:
- Four hormones: ______(fluid balance - vasoconstrictor), _______(fluid balance, vasoconstrictro), and _______ and ________(reinforce sympathetic nervous system)
- ______activity (exerts generalized vasoconstrictor effect)
The following flow chart summarizes the intrinsic and extrinsic mechanisms that influence arteriolar radius and, thus, vascular resistance.
- Total peripheral resistance depends on arteriolar radius and blood viscosity
- Blood viscosity is primarily dependent on the number of red blood cells
- Arteriolar Radius depends on both local (intrinsic) and extrinsic control
- Local (intrinsic) control (local changes acting on the arteriolar smooth muscle in the vicinity) mechanisms include:
- Response to shear stress
- myogenic responses to stress - plays minor role in active and reactive hyperaemia
- Application of heat/cold - therapeutic
- histamine release (injury/allergic response)
- Extrinsic control mechanisms are important in regulation of blood pressure and include:
- Four hormones: vasopressin (fluid balance - vasoconstrictor), Angiotensin II (fluid balance, vasoconstrictor), and Epinephrine and Norepinephrine (reinforce sympathetic nervous system)
- Sympathetic activity (exerts generalized vasoconstrictor effect)
