Ch. 20 Review Flashcards
Labe the following structure
What are the three layers of blood vessel walls?
Tunica intima, Tunica media, Tunica externa
What is the smallest of the arteries, thin-walled?
Arterioles
What are the smallest of the blood vessels, and the site of gas exchange between blood and tissue cells?
Capillaries
What are large, thick-walled arteries found near the heart that contain sheets of elastic fibers?
Elastic arteries
Small, thinned walls, porous veins
Venules
Arteries which deliver blood to specific organs: contain the most smooth muscles of the vessels
Muscular arteries
Larger vessels returning blood to the heart
Veins
What is the site where resistance to blood flow is greatest?
Arterioles
What is the site where exchanges of food and gases are made?
Capillaries
What is the site where blood pressure is lowest?
Large veins
What is the site where the velocity of blood flow is fastest?
Large arteries
Site where the resistance to blood flow is greatest
Arterioles
Site where exchanges of food and gases are made
Capillaries
Site where the velocity of blood flow is the slowest
Capillaries
Site where the blood volume is greatest
Large veins
Site where the blood volume is greatest
Large arteries
Site that is the major determinant of peripheral resistance
Arterioles
Label the diagram and answer the questions
Label the capillary bed
The mechanism that during inhalation abdominal pressure increases, squeezing local veins and forcing blood towards the heart and at the same time pressure in the chest decreases and thoracic veins expand speeding blood entry speeding blood entry to the right atrium
Respiratory Pump
What is the mechanism that helps return blood to the heart via the veins that involves skeletal muscle?
Muscular pump
What is the mechanism that helps return blood to the heart that involves pressure changes during breathing?
Respiratory pump
What prevents the backflow of blood in veins?
Venous valves
The action of skeletal muscle surrounding veins “milks” the blood upwards in the extremities
Muscular pump
Mechanism of the heart called that sympathetic nervous system can constrict the size of veins, pushing blood toward the heart
Sympathetic venoconstriction
What is the formula that relates blood flow to pressure change and resistance? What happens when the pressure decreases? Resistance decreases?
F = ∆P/R
Flow is directly related to the change in pressure and inversely related to resistance
If the change in pressure decreases– flow decreases
If resistance decreases, flow increases
Describe the relationship between pressure in blood flow as it relates to blood flowing in arteries, capillaries, and veins.
The volume of blood flowing through a given area/time period; equal CO for the whole system
Blood flow
Force per unit area exerted on the wall by blood (in mmhg)
Blood pressure
Pressure when ventricles relax
Diastolic pressure
The pressure that propels blood into the tissues
MAP mean arterial pressure
Pressure at the peak of ventricular contraction
Systolic pressure
Opposition to flow
Resistance
What happens to blood flow when the change in pressure decreases?
Flow decreases
What happens to blood flow when resistance decreases?
Flow increases
List three factors that determine resistance in a vessel.
- Blood viscosity
- Vessel length
- Vessel diameter
What is the significance of low blood pressure in capillaries?
Prevents capillary rupture and allows more time for nutrient/gas exchange
low pressure = low flow
Capillaries are fragile and high pressure would rupture them
Too much pressure would force unwanted fluid flow into interstitial spaces and tissues Due to permeability of capillary walls
low flow means more time for nutrients/ gas exchange to occur
What are the three most important factors regulating blood pressure?
- Cardiac output
- Resistance
- Blood volume
What two factors regulate blood pressure short term?
Neutral Controls & Hormonal controls
Explain the factor regulating blood pressure known as Neutral controls ( i.e. baroreceptors, chemoreceptors). Long and short-term goals?
Neutral controls alter both cardiac output and peripheral resistance. Neutral controls are directed at two goals
1) Maintaining adequate blood pressure by altering blood vessel diameter on a moment by moment basis
2) Altering blood distribution to respond to specific demands of various organs
What factor regulates blood pressure long term?
Kidney regulation
Kidney regulation
The kidneys controls blood pressure in the long term by adjusting blood pressure through the regulation of blood through both direct and indirect mechanisms
Direct renal mechanism
*High blood volume or BP – more urine is produced. The increased pressure forces filtrate through the kidneys before the kidney finish the job, more of it leaves the body
*Low blood volume or BP – Little urine is produced; slower flow and more water retention
Intdirect renal mechanism
When blood pressure falls, certain kidney cells release renin (renin causes the production of Angiotensin II acts in 4 ways to stabilize arterial blood pressure)
1) Stimulates the adrenal cortex to release aldosterone; aldosterone increases renal absorption of NA+ ions, which causes water to be retained( thus water reuptake occurs; lee urine is produced)
2) Causes the hypothalamus to release ADH (ADH promotes water reabsorption by the kidneys increasing blood volume)
3) triggers the sensation of thirst by activating hypothalamic thirst centers
4) Acts as a potent vasoconstrictor, increasing blood pressure by increasing peripheral resistance
True or False: Blood flow into capillaries is constant.
False
Blood flow into capillaries is subject to change and regulation
True or False: Blood flow into capillaries is regulated by the opening and closing of the precapillary sphincters.
True
What is bulk flow in capillaries?
Fluid is forced out of capillaries at the arterial end and returns at the venous end
What does hydrostatic pressure (HP) do in capillaries?
Forces fluid out of capillary to interstitial fluid
What does colloid osmotic pressure (OP) do in capillaries?
Forces fluid into the capillaries
What is the net filtration pressure (NFP) in a capillary bed?
NFP = net HP - net OP
What is the role of baroreceptors in blood pressure regulation?
Respond to stretch in blood vessels to regulate vessel diameter
What is the role of chemoreceptors in blood pressure regulation?
Detect changes in blood chemistry to influence cardiac output and resistance
Explain how hormones regulate blood pressure
Hormones regulate blood pressure via changes in peripheral resistance and blood volume
What hormone promotes vasodilation short-term and decreases blood volume (by stimulating Na+ loss) Produced by the atria, promotes vasodilation? Short term
Atrial Natriuretic Peptide (ANP)
What hormone is released when blood pressure or blood volume is low, causing the kidney to release renin (intense vasoconstriction; increase BP rapidly)?
Short term
Angiotensin II
What hormone is made by the hypothalamus, makes kidneys conserve water, increased blood volume increasing blood volume thus increases BP (can also increase BP by causing VC if large enough amounts are released). Short term
Antidiuretic Hormone (ADH)
What hormone is a vasoconstrictor for blood vessels (thus increasing BP) but is a vasodilator for skeletal and cardiac muscle. Short term
Norepinephrine (NE) and Epinephrine
As blood flows from the heart to the systemic capillary beds, it travels through progressively smaller vessels. Why then does pressure fall instead of rise?
Because even though the vessels are smaller, there is a greater cross section of vessels in capillary beds.
Although the diameter of a single capillary is very small, the number of capillaries supplied by a single arteriole is so great that the total cross sectional are available for the floe is increased. Therefore the pressure of the blood as it enters the capillaries decreases.
Mechanisms that regulate tissue flows to tissues /tissue profession) include all the following except?
A)Levels of gases, or wastes products in a given tissue
B)The response of smooth muscle to it degree of stretch
C) The balance of endothelin and nitric oxide inside vessels
D)Temporary changes in systemic blood pressure
E) All mechanisms routinely regulate tissue perfusion
Temporary changes in systemic blood pressure
What is the primary function of the sympathetic venoconstriction?
Pushes blood toward the heart
Indicate whether decreased O2 causes vasodilation or vasoconstriction.
Vasodilation
Indicate whether increased CO2 causes vasodilation or vasoconstriction.
Vasodilation
Indicate whether increased nitric oxide causes vasodilation or vasoconstriction.
Vasodilation
Indicate whether local smooth muscle stretch causes vasodilation or vasoconstriction.
Vasoconstriction
Indicate whether decreased endothelin causes vasodilation or vasoconstriction.
Vasodilation
Indicate whether local smooth muscle stretch causes vasodilation or vasoconstriction.
vasoconstriction
Indicate whether Antidiuretic hormone causes vasodilation or vasoconstriction.
vasoconstriction
Indicate whether atrial natriuretic peptide (ANP) causes vasodilation or vasoconstriction.
Vasodilation
Indicate whether angiotensin II causes vasodilation or vasoconstriction.
Vasoconstriction
Indicate whether epinephrine causes vasodilation or vasoconstriction.
Vasoconstriction
True or False: Large molecules, such as proteins, move out of capillaries via pinocytosis.
True
True or False: Bulk flow is the most important mechanism by which nutrients and gases move in and out of capillaries.
False
Bulk flow is important in tissue fluid regulation
True or False: Blood flow into capillaries is constant
False
Flow is intermittent
True or False: Blood flow into capillaries is regulated by the opening and closing of precapillary sphincters
True
True or False: Lipid soluble molecules move between blood and interstitial fluid by osmosis?
False
water moves via osmosis
True or False: Small water soluble molecules move through capillary walls via capillary clefts or fenestrations?
True
True or False: Bulk flow in capillaries reflects a balance between hydrostatic and osmotic pressure
True
True or False: Due to differences in hydrostatic and osmotic pressure, fluid tends to be forced out of the capillaries at the venous end and pushed back in at the atrial end?
False
fluid is forced out at the atrial end, back in at the venous end
What vessel is the major determinant of peripheral resistance?
Arterioles
What is the significance of the greater cross-sectional area in capillary beds do to blood pressure?
Causes pressure to decrease as blood enters capillaries
What are the effects of high blood volume or pressure on urine production?
More urine is produced
What are the effects of low blood volume or pressure on urine production?
Less urine is produced
What is bulk flow of fluid across capillaries
With bulk flow, fluid is forced out of the capillaries on the arterial ends of the capillary bed and returns at the venous end. The direction and amount of flow across capillary walls reflects the balance between two dynamic and opposing forces: hydrostatic pressure and colloid osmotic pressure.
Hydrostatic pressure (HP)
is the force exerted by a fluid pressing against a wall. In capillaries HP is basically capillary BP and is higher at the atrial end and lower at the venous end which tends to force fluid out of the capillary to interstitial fluid
Colloid Osmotic Pressure (OP)
is the force created by large non-diffusible proteins which are abundant in capillaries. It does not change much from the arterial end to the venous end of capillary bed.
Because plasma proteins stay put in the blood (they cant move out ) blood is hypertonic to interstitial fluid
Net filtration pressure
All the forces acting on a capillary bed NFP(net HP-net OP)
1) at the beginning of the NFP is positive, pushing fluid out of the capillaries
2) at the end of the capillary bed negative NFP is pushing fluid back into the capillaries
With bulk flow, because of different forces acting upon the capillary beds fluid is forced out the capillaries on the arterial end of the capillary bed and returns at the venous end
