Haemodynamic

Question 1

This is a study of the physical principles that govern blood flow through the blood vessels and heart

Blood is forced out of the heart and through blood vessels under great pressure. Blood flows through the narrow arterioles, capillaries and v………. with much …….. In other words, these vessels offer resistance to the flow of blood. The physiological regulation of blood flow, pressure. and resitstance in maintaining homeostasis is based on some simple laws of ………..s

Answer 1

This is a study of the physical principles that govern blood flow through the blood vessels and heart

Blood is forced out of the heart and through blood vessels under great pressure. Blood flows through the narrow arterioles, capillaries and venules with much difficulty. In other words, these vessels offer resistance to the flow of blood. The physiological regulation of blood flow, pressure, and resistance in maintaining homeostasis is based on some simple laws of haemodynamics

Question 2

Types of Blood vessels

Arteries
- Ela..
- Mu...
- Arte....
Capillaries: site of exchange with .........
Veins: t........ walls than arteries, contain less ...... tissue and fewer s......muscle cells
- Venules
- Small veins
- Medium or large veins

Answer 2

Arteries
Elastic
Muscular
Arterioles
Capillaries: site of exchange with tissues
Veins: thinner walls than arteries, contain less elastic tissue and fewer smooth muscle cells
Venules
Small veins
Medium or large veins

Question 3

Capillaries

Capillary wall consists of ………cells (simple squa……. epithelium), basement membrane and a delicate layer of …… ……..tissue (C.T.). Also consist of scattered ………. cells that are either fibro……., ma……..s or un……. smo..muscle cells.
Substances move through capillaries by diffusion through
- Lipid-……. and small water-soluble molecules through plasma ……..
- Larger water-soluble molecules pass through fenes… or gaps between end…..l cells.

Answer 3

Capillary wall consists of endothelial cells (simple squamous epithelium), basement membrane and a delicate layer of loose connective tissue (C.T.). Also consist of scattered pericapillary cells that are either fibroblasts, macrophages or undifferentiated smooth muscle cells.
Substances move through capillaries by diffusion through
Lipid-soluble and small water-soluble molecules through plasma membrane
Larger water-soluble molecules pass through fenestrae or gaps between endothelial cells.

Question 4

Capillary network

Blood flows from arterioles through me………., then through capillary network
Flow through thoroughfare channel fairly consistent while flow through arterial capillaries is inte………
Sm….. muscle in arterioles, metarterioles, and precapillary sph…… help to …….. blood flow

Answer 4

Blood flows from arterioles through metarterioles, then through capillary network
Flow through thoroughfare channel fairly consistent while flow through arterial capillaries is intermittent
Smooth muscle in arterioles, metarterioles, and precapillary sphincters help to regulate blood flow

Question 5

Tunica intima
- Endo…..
- Bas…. membrane
- Lam…. p…..(C.T. layer)
- Internal elastic membrane. Fenestrated layer of elastic fibers.
Tunica media: smooth muscle cells arranged c…… around the blood vessel.
Vasoconstriction: ….. muscles contract, ……. in blood flow
Vasodilation: muscles relax, …….. in blood flow
Tunica externa (adventitia): …… tissue, varies from dense r…. near the vessel to loose that ……. with the surrounding C.T.

Answer 5

Tunica intima
Endothelium
Basement membrane
Lamina propria (C.T. layer)
Internal elastic membrane. Fenestrated layer of elastic fibers.
Tunica media: smooth muscle cells arranged circularly around the blood vessel.
Vasoconstriction: smooth muscles contract, decrease in blood flow
Vasodilation: smooth muscles relax, increase in blood flow
Tunica externa (adventitia): connective tissue, varies from dense regular near the vessel to loose that merges with the surrounding C.T.

Question 6

Elastic artery

Elastic or conducting arteries
Largest ……., pressure high and fluctuates between …….. and ……. More …….. ………. than muscle.
Relatively ….. tunica in…., thin tunica ad…….indie indie vibes

Answer 6

Elastic or conducting arteries
Largest diameters, pressure high and fluctuates between systolic and diastolic. More elastic tissue than muscle.
Relatively thick tunica intima, thin tunica adventitia

Question 7

Muscular Artery

Muscular or ……. arteries
- Smooth muscle allows vessels to regulate blood supply by ………. or d……..
- Most of the smaller unnamed arteries
- Thick walls due to 25-40 layers of …….. muscle.
- Also called distributing arteries because ……… muscle allows vessels to pa……. regulate blood supply to different regions of the body.
Smaller ……….. arteries
- Adapted for………. and vasoco………..

Answer 7

Muscular or medium arteries
Smooth muscle allows vessels to regulate blood supply by constricting or dilating
Most of the smaller unnamed arteries
Thick walls due to 25-40 layers of smooth muscle.
Also called distributing arteries because smooth muscle allows vessels to partially regulate blood supply to different regions of the body.
Smaller muscular arteries
Adapted for vasodilation and vasoconstriction.

Question 8

Arterioles

Transport blood from small a…… to ……..
Smallest arteries where the three ……. can be differentiated
Like small arteries, capable of vas…… and dilation

Answer 8

Transport blood from small arteries to capillaries
Smallest arteries where the three tunics can be differentiated
Like small arteries, capable of vasoconstriction and dilation

Question 9

Venules drain capillary network. ……. cells and basement membrane with a few …… muscle cells. As diameter of venules increases, amount of smooth muscle ……..

Small veins. Smooth muscle cells form a continuous layer. Addition of tunica adv……. made of ……….. connective tissue

Answer 9

Venules drain capillary network. Endothelial cells and basement membrane with a few smooth muscle cells. As diameter of venules increases, amount of smooth muscle increases.
Small veins. Smooth muscle cells form a continuous layer. Addition of tunica adventitia made of collagenous connective tissue

Question 10

Medium and large veins

Medium veins. Go-between between …… veins and ….. veins.

Large veins. Tunica …….. is t…: endothelial cells, relatively …… layer of C.T and a few scattered e…… f……. Tunica media has circularly arranged ……. muscle cells. Ad……. is predominant layer.

Answer 10

Medium veins. Go-between between small veins and large veins.

Large veins. Tunica intima is thin: endothelial cells, relatively thin layer of C.T and a few scattered elastic fibers. Tunica media has circularly arranged smooth muscle cells. Adventitia is predominant layer.

Question 11

Valves

Valves found in all ….. greater than .. mm in diameter

Folds in …. form two flaps that …..

More valves in veins of lower … than in veins of ……… …….

Answer 11

Valves found in all veins greater than 2 mm in diameter.
Folds in intima form two flaps that overlap.
More valves in veins of lower extremities than in veins of upper extremities.

Question 12

Aging of Arteries

Arteriosclerosis: general term for ……… changes in arteries making them ….. elastic
Atherosclerosis: d…….. of ……. on walls

Answer 12

Arteriosclerosis: general term for degeneration changes in arteries making them less elastic
Atherosclerosis: deposition of plaque on walls

Question 13

Dynamics of Blood circulation

Interrelationships between

• p….
• f…..
• r…..
• control ….. that regulate …. and blood ….

Answer 13

Interrelationships between
Pressure
Flow
Resistance
Control mechanisms that regulate blood pressure and blood flow

Question 14

Blood pressure

Measure of … exerted by blood against the …..

Blood moves through …. because of blood pressure

Measure by listening for korotokoff sounds produced by …. flow in …. as pressure …. from pressure cuff

Answer 14

Measure of force exerted by blood against the wall
Blood moves through vessels because of blood pressure
Measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure released from blood pressure cuff

Question 15

Blood flow

Blood flow is the ……. of blood that passes a given point in the …….. in a given period
Blood flow is usually expressed in m….. …… minute
Blood flow in an adult at rest is approximately …….. mL/min

Answer 15

Blood flow is the quantity of blood that passes a given point in the circulation in a given period
Blood flow is usually expressed in mL per minute
Blood flow in an adult at rest is approximately 5000 mL/min

Question 16

Turbulent flow

When the blood flow becomes too ……, when it passes an …….. in a vessel, when it makes a ….. turn, or when it passes over a rough surface, the flow may become t……… rather than streamline
Turbulent flow means that the blood flows …….in the vessel as well as along the vessel forming ……. in the blood called ……. currents

Answer 16

When the blood flow becomes too great, when it passes an obstruction in a vessel, when it makes a sharp turn, or when it passes over a rough surface, the flow may become turbulent rather than streamline
Turbulent flow means that the blood flows crosswise in the vessel as well as along the vessel forming whorls in the blood called eddy currents

Question 17

Laminar flow

When blood flows at a steady rate through a long, smooth vessel, it flows in s………., with each layer of blood remaining the ……. distance from the …….
Also the central portion of blood stays in the centre of the …….
This type of flow is called …….. flow or str……… flow and is the opposite of t……….. flow

Answer 17

When blood flows at a steady rate through a long, smooth vessel, it flows in streamlines, with each layer of blood remaining the same distance from the wall
Also the central portion of blood stays in the centre of the vessel
This type of flow is called laminar flow or streamline flow and is the opposite of turbulent flow

Question 18

This is a term used to describe the diameter changes in large …….. when the heart is ejecting blood into the arteries (systole) and has stopped ejecting ……….. with each heartbeat. The walls of large arteries eg. aorta, common carotid, subclavian and pulmonary arteries and their larger branches, contain elastic fibres.
These arteries increase their ……. when the blood pressure rises during ……. and decrease their diameters when the blood pressure falls during ……… The diameter changes result in the large arteries containing ….. blood during systole than during diastole. That additional blood is ……… peripherally during the next ………
This compliance or Windkessel effect prevents excessive rises in blood pressure during systole. One major result is a lower fluid mechanical ……… load on the heart than otherwise would have occurred. Pressure wave reflections in the arterial system can and do alter this effect.
The Windkessel effect becomes diminished with age. This occurs because the walls of the …… and other arteries become less ……. as a result of arteriosclerosis or atherosclerosis. Then, for the same amount of blood ejected from the heart during systole of the same duration, an excess rise of pressure does occur in the large arteries, as the vessel walls are no longer able to ……. and ……. forces in the same way. Elevated ……… pressures have increasingly been shown to be associated with strokes, cardiac enlargement, heart failure and other undesirable events.

Answer 18

This is a term used to describe the diameter changes in large arteries when the heart is ejecting blood into the arteries (systole) and has stopped ejecting (diastole) with each heartbeat. The walls of large arteries eg. aorta, common carotid, subclavian and pulmonary arteries and their larger branches, contain elastic fibres.
These arteries increase their diameters when the blood pressure rises during systole and decrease their diameters when the blood pressure falls during diastole. The diameter changes result in the large arteries containing more blood during systole than during diastole. That additional blood is discharged peripherally during the next diastole.
This compliance or Windkessel effect prevents excessive rises in blood pressure during systole. One major result is a lower fluid mechanical pressure load on the heart than otherwise would have occurred. Pressure wave reflections in the arterial system can and do alter this effect.
The Windkessel effect becomes diminished with age. This occurs because the walls of the aorta and other arteries become less elastic as a result of arteriosclerosis or atherosclerosis. Then, for the same amount of blood ejected from the heart during systole of the same duration, an excess rise of pressure does occur in the large arteries, as the vessel walls are no longer able to absorb and dissipate forces in the same way. Elevated systolic pressures have increasingly been shown to be associated with strokes, cardiac enlargement, heart failure and other undesirable events.

Question 19

Pressure, flow and resistance

Flow through a blood vessel is determined by two factors:-
1) The ……… difference between the two …… of the vessel (referred to as the pressure ……), which is the force that pushes the blood through the vessel (P1 – P2)

2)The impediment to blood flow through the vessel, which is called v…….. ……….(measured in units of pressure, per unit time, per unit volume e.g. Pascals per second per cubic metre)

Flow through the vessel can be calculated by using Darcy’s
law (the fluid equivalent of Ohm’s law)
Q (i.e. blood flow) = ∆P ÷ R
Where ∆P is the pre….. ……..between the two ends of the vessel
and R is the ………

Answer 19

Flow through a blood vessel is determined by two factors:-

1) The pressure difference between the two ends of the vessel (referred to as the pressure gradient), which is the force that pushes the blood through the vessel (P1 – P2)
2) The impediment to blood flow through the vessel, which is called vascular resistance (measured in units of pressure, per unit time, per unit volume e.g. Pascals per second per cubic metre)

Flow through the vessel can be calculated by using Darcy’s
law (the fluid equivalent of Ohm’s law)
Q (i.e. blood flow) = ∆P ÷ R
Where ∆P is the pressure difference between the two ends of the vessel
and R is the resistance.

Question 20

Pressure, flow and resistance cont.

Q (i.e. blood flow) = ∆P ÷ R
This law expresses the most important of all the relations that needs to be understood with regard to the understanding of haemodynamics
The formula states, in effect, that the blood flow is ……. …………l to the pressure difference but …….. ………… to the resistance
There are two other forms of the equation:-
∆P = Q x ….
R = ∆P ÷ …..

Answer 20

Q (i.e. blood flow) = ∆P ÷ R
This law expresses the most important of all the relations that needs to be understood with regard to the understanding of haemodynamics
The formula states, in effect, that the blood flow is directly proportional to the pressure difference but inversely proportional to the resistance
There are two other forms of the equation:-
∆P = Q x R
R = ∆P ÷ Q

Question 21

Critical closing pressure, Laplace’s law and compliance

Critical closing pressure: Pressure at which a blood vessel …… and …… …….. stops
Laplace’s Law
Force acting on blood vessel ….. is proportional to …….. of the vessel times blood pressure
F= D X …; thus as diameter of a vessel increases, force on the wall …….. Weakened part of a vessel wall bulges out and is an………

Vascular compliance: Tendency for blood vessel volume to increase as blood pressure increases
Compliance = increase in …….. through an increase in …………..
More easily the vessel wall stretches, the greater its ………
Venous system has a large compliance (24 times greater than that of arteries) and acts as a blood ……… = capacitance

Answer 21

Critical closing pressure: Pressure at which a blood vessel collapses and blood flow stops
Laplace’s Law
Force acting on blood vessel wall is proportional to diameter of the vessel times blood pressure
F= D X P; thus as diameter of a vessel increases, force on the wall increases. Weakened part of a vessel wall bulges out and is an aneurysm.

Vascular compliance: Tendency for blood vessel volume to increase as blood pressure increases
Compliance = increase in volume through an increase in pressure
More easily the vessel wall stretches, the greater its compliance
Venous system has a large compliance (24 times greater than that of arteries) and acts as a blood reservoir = capacitance

Question 22

Viscosity

Measure of resistance of liquid to flow
Resistance proportionate to flow
As viscosity increases, ………. …… ….. ……. ………….
Viscosity influenced largely by the ……..(percentage of the total blood …… composed of … blood cells).
Dehydration and/or uncontrolled production of RBCs can lead to increased ……. which increases the workload on the ………

Answer 22

Measure of resistance of liquid to flow
Resistance proportionate to flow
As viscosity increases, pressure required to flow increases
Viscosity influenced largely by the haematocrit (percentage of the total blood volume composed of red blood cells).
Dehydration and/or uncontrolled production of RBCs can lead to increased viscosity which increases the workload on the heart.

Question 23

poiseuille’s law

Flow decreases when resistance ……… and vice versa. Since resistance is proportional to blood vessel diameter, constriction of a blood vessel ……. resistance and thus decreases flow
Flow =(P1 –P2)/R or (P1 –P2)r4/8vl
r = radius of ……, v = visc….., l = length of ……
Rate of blood flow is directly proportional to the forth power of the ….of the vessel, which demonstrates that the ……. of a blood vessel plays the greatest role of all factors in determining the rate of blood flow through a vessel
During exercise, the heart beats with greater force ……. pressure in the a……. Capillaries in skeletal muscle i…… in diameter …….. resistance and increasing flow. Increased flow in the aorta can go from 5L/min to 25L/min

Answer 23

Flow decreases when resistance increases and vice versa. Since resistance is proportional to blood vessel diameter, constriction of a blood vessel increases resistance and thus decreases flow
Flow =(P1 –P2)/R or (P1 –P2)r4/8vl
r = radius of vessel, v = viscosity, l = length of vessel
Rate of blood flow is directly proportional to the forth power of the radius of the vessel, which demonstrates that the diameter of a blood vessel plays the greatest role of all factors in determining the rate of blood flow through a vessel
During exercise, the heart beats with greater force increasing pressure in the aorta. Capillaries in skeletal muscle increase in diameter decreasing resistance and increasing flow. Increased flow in the aorta can go from 5L/min to 25L/min

Question 24

Physiology of systemic circulation

Determined by

• Anatomy of circulatory system
• Dynamics of blood …..
• Regulatory mechanisms that control …. and blood vessels

Blood volume

• Most in the veins (greater compliance)
• Smaller ….. in arteries and capillaries

Answer 24

Determined by
Anatomy of circulatory system
Dynamics of blood flow
Regulatory mechanisms that control heart and blood vessels
Blood volume
Most in the veins (greater compliance)
Smaller volumes in arteries and capillaries

Question 25

Cross sectional area
As diameter of vessels ………, the total cross-sectional area increases and …… of blood flow …….. Only one aorta with a cross-sectional area of 5 cm2. Total cross-sectional area of the millions of capillaries is 2500 cm2.
Much like a stream that flows …….. through a narrow gorge but flows slowly through a broad plane

Answer 25

As diameter of vessels decreases, the total cross-sectional area increases and velocity of blood flow decreases. Only one aorta with a cross-sectional area of 5 cm2. Total cross-sectional area of the millions of capillaries is 2500 cm2.
Much like a stream that flows rapidly through a narrow gorge but flows slowly through a broad plane

Question 26

Pressure and Resisitance

Blood pressure averages 100 mm Hg in aorta and drops to 0 mm Hg by the time the blood gets to the right …….. Due to ……. resistance to flow as cross-sectional area increases.
Greatest drop in pressure occurs in ………. which regulate blood flow through tissues
No large fluctuations in c…… and v….
Muscular arteries and arterioles are capable of co…… or di…… in response to autonomic and hormonal stimulation. Muscular …… regulate flow into a region of the body; arterioles regulate flow into a …… ………

Answer 26

Blood pressure averages 100 mm Hg in aorta and drops to 0 mm Hg by the time the blood gets to the right atrium. Due to decreased resistance to flow as cross-sectional area increases.
Greatest drop in pressure occurs in arterioles which regulate blood flow through tissues
No large fluctuations in capillaries and veins
Muscular arteries and arterioles are capable of constricting or dilating in response to autonomic and hormonal stimulation. Muscular arteries regulate flow into a region of the body; arterioles regulate flow into a specific tissue.

Question 27

pulse pressure

Difference between systolic and diastolic pressures

Increases when stroke volume ……… or vascular compliance ………. Compliance tends to decrease with age (arteriosclerosis) and pressure …….
Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity
Most frequent site used to measure pulse rate is in the radial ……- the radial pulse.

Answer 27

Difference between systolic and diastolic pressures
Increases when stroke volume increases or vascular compliance decreases. Compliance tends to decrease with age (arteriosclerosis) and pressure rises.
Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity
Most frequent site used to measure pulse rate is in the radial artery- the radial pulse.

Question 28

Capillary exchange: the movement of substances into and out of capillaries

Most important means of exchange: ………..
- Lipid solubl- e cross …… walls diffusing through ……..membrane. E.g., O2, CO2, steroid hormones, fatty acids.
Water soluble diffuse through ………. spaces or through ……….. of capillaries. E.g., glucose, amino acids.

Blood pressure, capillary permeability, and …….. affect movement of fluid from capillaries

Fluid moves out of capillaries at …… end and most but not all returns to capillaries at venous end. That which remains in tissues is picked up by the l…….. system then returned to venous circulation.

Answer 28

Capillary exchange: the movement of substances into and out of capillaries
Most important means of exchange: diffusion.
Lipid soluble cross capillary walls diffusing through plasma membrane. E.g., O2, CO2, steroid hormones, fatty acids.
Water soluble diffuse through intercellular spaces or through fenestrations of capillaries. E.g., glucose, amino acids.
Blood pressure, capillary permeability, and osmosis affect movement of fluid from capillaries
Fluid moves out of capillaries at arterial end and most but not all returns to capillaries at venous end. That which remains in tissues is picked up by the lymphatic system then returned to venous circulation.

Question 29

fluid exchange across capillary wall

Net filtration pressure (NFP)- force responsible for moving ……. …….. capillary walls. Two forces affect pressure

• Hydrostatic pressure: physical ……… of blood flowing through the …….or of fluid in ………. spaces
• Osmotic pressure: movement of solutes (plasma or tissue fluid) through a ……… (plasma membrane) in the presence of a non-……….. solute (large proteins). …….. proteins do not freely pass through the capillary walls and the ………. in protein …………. between the blood and ………. fluid is responsible for osmosis

Answer 29

Net filtration pressure (NFP)- force responsible for moving fluid across capillary walls. Two forces affect pressure
Hydrostatic pressure: physical pressure of blood flowing through the vessels or of fluid in interstitial spaces
Osmotic pressure: movement of solutes (plasma or tissue fluid) through a membrane (plasma membrane) in the presence of a non-diffusible solute (large proteins). Large proteins do not freely pass through the capillary walls and the difference in protein concentrations between the blood and interstitial fluid is responsible for osmosis

Question 30

Pressure Involved

Net Filtration Pressure (NFP) = Net h…… …….. pressure - net ……… pressure

Net hydrostatic pressure = ……-……
BP = ………. ………… pressure
IFHP = i…….. ……. ………… pressure

Net osmotic pressure = ….-……… where
BCOP = blood ……. ………… pressure
IFOP = ………….. pressure (lymphatic
vessels are pulling in tissue fluid)

Answer 30

Net Filtration Pressure (NFP) = Net hydrostatic pressure - net osmotic pressure

Net hydrostatic pressure = BHP-IFHP
BP = blood hydrostatic pressure
IFHP = interstitial fluid hydrostatic pressure

Net osmotic pressure = BCOP-IFOP where
BCOP = blood colloid osmotic pressure
IFOP = interstitial fluid osmotic pressure (lymphatic
vessels are pulling in tissue fluid)

Question 31

Oedema and Capillary Exchange

If capillaries become more permeable, …….. can leak into the ……….. fluid increasing ….. More fluid moves from the capillaries into the interstitial fluid: ……..

• Chemicals of inflammation ……….. permeability
• Decreases in plasma concentration of protein reduces ….; more fluid moves into ……….. fluid
  
  • Liver disease resulting in fewer ……. proteins
  • Loss of …….. proteins through the …….
  • ……….starvation

Blockage of veins increases capillary B…; reduced ……. return due to gravity

Blockage or removal of lymphatic vessels (blockage: elephantiasis; removal: cancer)

Answer 31

If capillaries become more permeable, proteins can leak into the interstitial fluid increasing ICOP. More fluid moves from the capillaries into the interstitial fluid: oedema.
Chemicals of inflammation increase permeability
Decreases in plasma concentration of protein reduces BCOP; more fluid moves into interstitial fluid
Liver disease resulting in fewer plasma proteins
Loss of plasma proteins through the kidneys
Protein starvation
Blockage of veins increases capillary BP; reduced venous return due to gravity
Blockage or removal of lymphatic vessels (blockage: elephantiasis; removal: cancer)

Question 32

Characteristics of Veins

Venous return to heart increases due to ………. in blood ……….., venous tone, and arteriole ……….

Venous tone: continual state of ………. contraction …………. stimulation

Answer 32

Venous return to heart increases due to increase in blood volume, venous tone, and arteriole dilation
Venous tone: continual state of partial contraction of the veins as a result of sympathetic stimulation

Question 33

Effect of Gravity on Blood pressure

In a standing position, ………. pressure caused by gravity increases blood pressure below the heart and ………. pressure above the heart.
Muscular movement ………. venous return.

Answer 33

In a standing position, hydrostatic pressure caused by gravity increases blood pressure below the heart and decreases pressure above the heart.
Muscular movement improves venous return.

Question 34

Control of Blood flow in Tissues

Local control: in most tissues, blood flow is ………. to metabolic needs of tissues
Nervous System: responsible for ……… blood flow and maintaining blood ……….
Hormonal Control: sympathetic action ……… stimulate ………….. and …………….

Answer 34

Local control: in most tissues, blood flow is proportional to metabolic needs of tissues

Nervous System: responsible for routing blood flow and maintaining blood pressure

Hormonal Control: sympathetic action potentials stimulate epinephrine and norepinephrine

Question 35

Local Control of Blood flow

Blood flow can increase 7-8 times as a result of ……….. of metarterioles and the ……… of precapillary …………, in response to increased rate of metabolism
Vasomotion: periodic ……….. and relaxation of ………… sphincters. Autoregulation.
Long-term local control: capillaries become more …… in a region that regularly has an ……….. metabolic rate.

Answer 35

Blood flow can increase 7-8 times as a result of vasodilation of metarterioles and the relaxation of precapillary sphincters, in response to increased rate of metabolism
Vasomotion: periodic contraction and relaxation of precapillary sphincters. Autoregulation.
Long-term local control: capillaries become more dense in a region that regularly has an increased metabolic rate.

Question 36

Nervous Regulation of Blood vessels

Important in minute-to-minute regulation of local circulation

Provides a means by which blood can be s…… from one large area of the peripheral ……… system to another area by increasing resistance

Sympathetic division most important. ……… all vessels except capillaries, precapillary sp……., and most metar……….

Vasomotor center in lower pons and upper medulla oblongata.

• Excitatory part is ………. active. Causes vasomotor tone. Norepinephrine
• Inhibitory part can cause ……….. by decreasing sympathetic output

Sympathetic stimulation of adrenal ……. causes output of norepinephrine and epinephrine into circulation. Causes ……… in vessels (α-adrenergic receptors) except in ……. muscle where …….takes place (ß-adrenergic receptors)

Answer 36

Important in minute-to-minute regulation of local circulation
Provides a means by which blood can be shunted from one large area of the peripheral circulatory system to another area by increasing resistance
Sympathetic division most important. Innervates all vessels except capillaries, precapillary sphincters, and most metarterioles.
Vasomotor center in lower pons and upper medulla oblongata.
Excitatory part is tonically active. Causes vasomotor tone. Norepinephrine
Inhibitory part can cause vasodilation by decreasing sympathetic output
Sympathetic stimulation of adrenal medulla causes output of norepinephrine and epinephrine into circulation. Causes vasoconstriction in vessels (α-adrenergic receptors) except in skeletal muscle where vasodilation takes place (ß-adrenergic receptors)

Question 37

Regulation of Mean Arterial Pressure

Mechanisms that maintain …….. blood ……. within a ….. ……. pressure (MAP): slightly less than the average of …….. and ……. pressures because ……. lasts longer than ……..
70 mmHg at birth, 100 mmHg from adolescence to middle age, 110 mmHg in healthy older individuals.
MAP = CO (cardiac output) x PR (…….. ………..)
MAP = HR (heart rate) x SV (stroke volume) x PR
MAP α HR, SV, and PR. If any of these go up, so does …..
Two systems to regulate pressure: short-term and long-term

Answer 37

Mechanisms that maintain arterial blood pressure within a normal range of values
Mean arterial pressure (MAP): slightly less than the average of systolic and diastolic pressures because diastole lasts longer than systole.
70 mmHg at birth, 100 mmHg from adolescence to middle age, 110 mmHg in healthy older individuals.
MAP = CO (cardiac output) x PR (peripheral resistance)
MAP = HR (heart rate) x SV (stroke volume) x PR
MAP α HR, SV, and PR. If any of these go up, so does MAP.
Two systems to regulate pressure: short-term and long-term

Question 38

Short - term regulation of blood pressure

Baroreceptor reflexes: change peripheral ………., h…. ……, and …… volume in response to changes in blood pressure

Chemoreceptor reflexes: sensory receptors sensitive to ox….., c…… ………, and … levels of blood

Central nervous system ischemic response: results from high …… …….. or low .. levels in ………. and increases p…….. ………..

Answer 38

Baroreceptor reflexes: change peripheral resistance, heart rate, and stroke volume in response to changes in blood pressure

Chemoreceptor reflexes: sensory receptors sensitive to oxygen, carbon dioxide, and pH levels of blood

Central nervous system ischemic response: results from high carbon dioxide or low pH levels in medulla and increases peripheral resistance

Question 39

Adrenal Medullary Mechanisms

Activated when stimuli result in a ……….. increase in ………. stimulation of …….. and ……. vessels (large decrease in blood pressure, sudden and substantial increase in physical activity, stress)

Adrenal releases ………. and n………..

Hormones mimic ………… stimulation of heart and blood vessels.

Answer 39

Activated when stimuli result in a substantial increase in sympathetic stimulation of heart and blood vessels (large decrease in blood pressure, sudden and substantial increase in physical activity, stress)

Adrenal releases epinephrine and norepinephrine

Hormones mimic sympathetic stimulation of heart and blood vessels.

Question 40

CNS Ischemic Response

Elevation of BP in response to a lack of blood flow to the … ………..

Functions in reponse to emergency situtations and BP …. ……… 50 mmHg

Neurons of vasomotor center strongly stimulated; increases …… …… to brain if vessels are intact but at the same time, decreases ……. … blood because blood does not go to lungs.
Lack of oxygen causes ……… ……. to become inactive; extensive vasodilation follows with concomitant drop in … ….. . Death if CNS ischemic response lasts longer than a few minutes.

Answer 40

Elevation of BP in response to a lack of blood flow to the medulla oblongata.
Functions in response to emergency situations and BP falls below 50 mmHg
Neurons of vasomotor center strongly stimulated; increases blood flow to brain if vessels are intact but at the same time, decreases oxygenation of blood because blood does not go to lungs.
Lack of oxygen causes vasomotor center to become inactive; extensive vasodilation follows with concomitant drop in BP. Death if CNS ischemic response lasts longer than a few minutes.

Question 41

Long-Term Regulation of Blood pressure

• Re…-angi………..-……………… mechanism
• ……….. (ADH) mechansim
• …… ……….. mechanism
• ……. ……. mechanism
• Stress - re…….. response

Answer 41

Renin-angiotensin-aldosterone mechanism

Vasopressin (ADH) mechanism

Atrial natriuretic mechanism

Fluid shift mechanism

Stress-relaxation response

Question 42

Atrial natriuretic hormone: released from ……. muscle cells when …… blood pressure ………, simulating an increase in ……. production, causing a decrease in …….. volume and ……. ……….

Fluid shift: movement of fluid from ……… spaces into ………s in response to ……… in blood pressure to maintain blood ……and vice versa.

Stress-relaxation response: adjustment of blood vessel ……… muscle to respond to change in blood …..1)… When blood ……… suddenly …….. and pressure drops, ……… muscles ………. and vice versa.

Answer 42

Atrial natriuretic hormone: released from cardiac muscle cells when atrial blood pressure increases, simulating an increase in urinary production, causing a decrease in blood volume and blood pressure

Fluid shift: movement of fluid from interstitial spaces into capillaries in response to decrease in blood pressure to maintain blood volume and vice versa.

Stress-relaxation response: adjustment of blood vessel smooth muscle to respond to change in blood volume. When blood volume suddenly declines and pressure drops, smooth muscles contract and vice versa.

Question 43

Intrinsic Regulaiton of Blood flow

1) Myogenic mechanisms
If the …….. blood pressure and flow through an organ are inadequate, the metabolism of the organ cannot be maintained beyond a limited period of time.

An excessively high blood pressure on the other hand can also be dangerous, particularly in the brain because this may cause the fine blood vessels to burst.

Thus, changes in systemic arterial pressure are compensated for in the brain, and some other organs, by the appropriate response of the vascular smooth muscle

A DECREASE in arterial blood pressure causes the cerebral blood vessels to DILATE, so that adequate rates blood flow can be maintained, despite the decreased pressure.

An INCREASE in blood pressure causes cerebral blood vessels to CONSTRICT, so that the finer vessels downstream are protected from the elevated blood pressure.
These are direct responses by the vascular smooth muscle to changes in blood pressure and are not under nervous control.

Answer 43

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Question 44

Intrinsic Regulaiton of Blood flow

1) Myogenic mechanisms
If the …….. blood pressure and flow through an organ are inadequate, the metabolism of the organ cannot be maintained beyond a limited period of time.

An excessively high blood pressure on the other hand can also be dangerous, particularly in the brain because this may cause the fine blood vessels to burst.

Thus, changes in systemic arterial pressure are compensated for in the brain, and some other organs, by the appropriate response of the vascular smooth muscle

A DECREASE in ….. ……. …….. causes the cerebral blood vessels to ……., so that adequate rates blood flow can be maintained, despite the decreased pressure.

An ………. in blood pressure causes cerebral blood vessels to ………, so that the finer vessels downstream are protected from the elevated blood pressure.
These are direct responses by the vascular ……. …….. to changes in blood …….. and are …… under nervous control.

Answer 44

jjMyogenic mechanisms
If the arterial blood pressure and flow through an organ are inadequate, the metabolism of the organ cannot be maintained beyond a limited period of time.
An excessively high blood pressure on the other hand can also be dangerous, particularly in the brain because this may cause the fine blood vessels to burst.
Thus, changes in systemic arterial pressure are compensated for in the brain, and some other organs, by the appropriate response of the vascular smooth muscle
A DECREASE in arterial blood pressure causes the cerebral blood vessels to DILATE, so that adequate rates blood flow can be maintained, despite the decreased pressure.
An INCREASE in blood pressure causes cerebral blood vessels to CONSTRICT, so that the finer vessels downstream are protected from the elevated blood pressure.
These are direct responses by the vascular smooth muscle to changes in blood pressure and are not under nervous control.

Question 45

Intrinisic Regulation of Blood flow 2

Metabolic mechanisms
Local vasodilation within an organ as a result of the chemical environment created by the organs metabolism

A number of factors promote this local vasodilation uncluiding the following:

• …… O2 concentraition retults from increased metabolic rate present in organ or tissue
• ……… Carbon dioxide concentration as a result of …… metabolism
• Decreased tissue pH - dueto presence of …, lactic.. … and other …… products
• the release of adenosine (from…..) or ….. ions from the …….

Answer 45

Metabolic mechanisms
Local vasodilation within an organ can occur as a result of the chemical environment created by the organ‘s metabolism.
A number of factors promote this local vasodilation including the following :
1) Decreased O2 concentration results from increased metabolic rate present in organ or tissue,
2) Increased Carbon Dioxide concentration - as a result of the increased metabolism,
3) Decreased tissue pH - due to presence of CO2, lactic acid and other metabolic products,
4) The release of Adenosine (from AMP) or Potassium ions from the tissues.

Question 46

Summary affecting pressure and flow of blood through the various vessels

Elasticity of large arteries. This factor determines the level of the ….. pressure when the ventricles ……. If the vessels become less elastic (ageing or arterioclerosis) the ….. pressure rises, and the recoil of the vessel to push blood forwards is …..

Circulation volume of blood. This determines the pressure in a system of a given capacity. Conditions such as salt retention are associated with ……. ….. and the …. ……. ……

Viscosity of blood. This determines the resistance of blood flow. A thicker fluid flows less easity than a thinner one, and obviously requires a greater …… ….. …… to to circulate it

A decrease in oxygen tension (living at high altitude) or bone tumours lead to polycthaemia (> 6 x 10^6/mm^3) leads to an increase in viscosity. Amaemia, abnormal shape (……….) or abnormal size (an………. )lead to a lower viscosity

These factors are not under physiological control but usually change due to a disease state

Answer 46

Elasticity of large arteries. This factor determines the level of the systolic pressure when the ventricles contract. If the vessels become less elastic (ageing or arteriosclerosis) the systolic pressure rises, and the recoil of the vessel to push the blood forwards is lost.

Circulating volume of blood. This determines the pressure in a system of a given capacity. Conditions such as salt retention are associated with fluid retention and the blood pressure rises.

Viscosity of blood. This determines the resistance of blood flow. A ‘thicker‘ fluid flows less easily than a ‘thinner‘ one, and obviously requires a greater application of force (blood pressure) to circulate it.

A decrease in oxygen tension (living at high altitude) or bone tumours lead to polycythaemia (> 6 x 106/mm3) leads to an increase in viscosity.  Anaemia, abnormal shape (poikilocytosis) or abnormal size (anisocytosis) lead to a lower viscosity.

Question 47

factors affecting pressure and flow of blood through the various vessels - continued

Cardiac output. This determines the volume of blood pumped per minute into the circulation which have a ….. ……….. at a given time. This creates the basis …….. and flow that depends on the amount pumped and the volume of the vessels

If the CO goes up, and the volume of the vessels remain c………., pressure and flow must ……. If the output stays the same, but the volume of the vessels increases, pressure must fall

Peripheral resistance. This refers to the difficulty encountered by the blood in …. through the ….. …. of the vascular system. These vessels can actively change their ,,,,, A narrowing of the vessels ….. peripheral resistance and will result in a rise in …… in the vessels proximal to the narrowing

These last two factors are subject to control and it is alteration of these that govern pressure and low in the circulation

Answer 47

Cardiac output. This determines the volume of blood pumped per minute into the circulation which have a given capacity at a given time. This creates the basic pressure and flow that depends on the amount pumped and the volume of the vessels.

If the CO goes up, and the volume of the vessels remain constant, pressure and flow must rise.  If the output stays the same, but the volume of the vessels increases, pressure must fall.

5. Peripheral resistance. This refers to the difficulty encountered by the blood in passing through the small arteries of the vascular system. These vessels can actively change their size. A narrowing of the vessels increases peripheral resistance and will result in a rise in pressure in the vessels proximal to the narrowing.