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Chapter 15 Blood flow and the control of blood pressure
Terms in this set (134)
-the most common cause of fainting.
-Vasovagal syncope occurs when your body overreacts to triggers, such as the sight of blood or extreme emotional distress.
what is perfusion?
the process of delivery of blood to a capillary bed in the biological tissue
why are the arteries known as the pressure reservoir?
-pressure produced by contraction of the left ventricle is stored in the elastic walls of arteries and slowly released through elastic recoil
-this mechanism maintains a continuous driving pressure for blood flow during ventricular relaxation
what vessels have a leaky epithelium that allows exchange of materials between plasma, the interstial fluid, and the cells of the body.
what vessels are known as the volume reservoir?
the inner lining of all blood vessels
what makes the tunica intima?
-the endothelium and its adjacent elastic connective tissue
vascular smooth muscle
the smooth muscle of blood vessels
in most blood vessels, smooth muscle cells maintain a state of partial contraction at all times, creating a condition known as
the arteries and arterioles are characterized by a convergent pattern of blood flow. True or False
False, they are characterized by their Divergent pattern of blood flow
what forms the microcirculation?
arterioles, along with capillaries and small postcapillary vessels called venules
difference between arteriole and metarteriole
-True arterioles have a continuous smooth muscle layer
-Metarterioles is only partial surrounded by smooth muscle
where is the precapillary sphincter?
-in the microcirculation
what happens if the precapillary sphincter relaxes? contracts?
-Relaxation of precapillary sphincter: blood flows through all the metarterioles and the arterioles
-contraction of precapillary sphincter: blood bypasses the capillaries and goes directly to the venous circulation
the smallest vessels in the cardiovascular system
___ and ____ are the site of exchange between the blood and the interstitial fluid
3 characteristics of the capillaries
-lacks smooth muscle
-lacks elastic or fibrous tissue reinforcement
-walls are supported by a flat layer of endothelium, one cell thick, supported on an acellular matrix called the basal lamina
-highly branched contractile cells surrounding the capillaries
-forms a mesh-like outer layer between the capillary endothelium and the interstital fluid
-Pericytes contribute to the "tightness" of capillary permeability
-the more pericytes, the less leaky the capillary endothelium
- a good example of place with a massive amount of pericytes is the cerebral capillaries that make up the blood-brain barrier
Blood flows from the capillaries into small vessels called
How are venules different from capillaries?
they are distinguished from capillaries by their convergent pattern flow
To assist venous flow, some veins have internal one-way valves. True or False
Veins are more numerous and larger than arteries. They contained more than half of the blood in the cardiovascular system. This is why they are known as the volume reservoir. True or False
the process by which new blood vessels develop
two growth factors that promote angiogenesis
-vascular endothelial growth factor (VEGF)
-Fibroblast growth factor (FGF)
-these are also known as mitogens
what are mitogens?
-growth factor that promote mitosis
-produced by smooth muscle cells and pericytes
two cytokines that inhibit angiogenesis
coronary heart disease
-also known as coronary artery disease
-a condition in which blood flow to the myocardium is decreased by fatty deposits that narrow the lumen of the coronary arteries
-newly forming blood vessels that appear to compensate for a blocked vessel
-mostly seen in coronary heart disease patients
the force that creates blood flow through the cardiovascular system is
Blood pressure is highest in the arteries and increases continuously as blood flows though the circulatory system. True or False
False, it decreases continuously as blood flows through the circulatory system
what causes the loss of blood pressure as the blood pumps through the circulatory system?
-the resistance of the vessels
-the resistance of the blood cells
where does the highest pressure occur? and what causes it?
-in the aorta
-the left ventricle
the rapid pressure increase that occurs when the left ventricle pushes blood into the aorta can be felt as a _____, or pressure wave
a measure of the strength of the pressure wave, is defined as systolic pressure minus diastolic pressure
blood returned to the heart, known as venous return is aided by what 3 things?
reflects the driving pressure created by the pumping action of the heart
-arterial blood pressure or simply called blood pressure
Because arterial pressure is pulsatile, we use ___ ____ ____ to represent driving pressure
-mean arterial pressure
if a rupture occurs in the brain, it is called a ___ ____ and may cause the loss of neurological function commonly called a _____
We estimate arterial blood pressure in the radial artery of the arm using a _____, an instrument consisting of an inflatable cuff and a pressure gauge
the sound heard as the blood squeezes through the still compressed artery with each pressure wave
How do you obtain blood pressure using a sphygmomanometer?
-the pressure at which a korotkoff sound is first heard represents the highest pressure in the artery and is recorded as the systolic pressure.
-the point at which the korotkoff sounds disappear is the lowest pressure in the artery and is recorded as the diastolic pressure
the average value for blood pressure
mean arterial pressure is proportional to cardiac output and peripheral resistance. True or False
what is peripheral resistance?
the resistance to flowed offered by the arterioles
4 factors that determine mean arterial blood pressure
-cardiac output(the effectiveness of the heart as a pump)
-resistance of the system to blood flow
-relative distribution of blood between arterial and venous blood vessels
Arteries usually only contain about ___% of total blood volume at any one time. Veins hold about ___% of the circulating blood volume at any one time
constriction of the veins redistributes blood to the arterial side of circulation, and raises the mean arterial pressure. True or False.
The kidney restores blood volume. True or False.
False, the kidney cannot restore blood volume, it can only conserve blood volume and prevent future decrease in blood pressure
the only to restore lost fluid volume is through
-drinking or IV infusions
-volume lost to external environment must be replaced from the external environment
what is the primary resistance to blood flow?
-the radius of the blood vessels
According to Poiseulle's Law, resistance to blood flow is directly proportionally to ___ and ___ and inversely proportional to the fourth power to ___
-P:the length of tubing through which the fluid flows and viscosity
-Inversely to the tubing radius
the main site of variable resistance in the systemic circulation and contribute more than ___% of the total resistance to flow in the system
arteriolar resistance is influenced by what three factors
-local control of arteriolar resistance
-when a vascular smooth muscle has the ability to regulate its own state of contraction
How does myogenic autoregulation work at the cellular level?
-when vascular smooth muscle cells in arterioles are stretched, mechanically gated channels in the muscle membrane open. Cation entry depolarizes the cell. the depolarization opens voltage-gated calcium channels, and calcium flows into the cell down its electrochemical gradient. Calcium entering the cell combines with calmodulin and activates myosin light chain kinase. MLCK in turn increases myosin ATPase activity and crossbridge activity, resulting in contraction.
the process in which an increase in blood flow accompanies an increase in metabolic activity is known as
-occurs when there is low oxygen levels and paracrines such as CO2 and H+ accumulate in the interstital fluid
-causes endothelial cells to synthesize the vasodilator nitric oxide.
-an increase in tissue blood flow following a period of low perfusion (blood flow)
Decreases in endogenous NO activity are suspected to play a role in hypertension and _____, the elevated blood pressure that sometimes occurs during pregnancy
In response to low tissue oxygen in the myocardium, the myocardial cells release _____(a vasodilator paracine). This dilates coronary arterioles in an attempt to bring additional blood flow into the muscle
____ and _____ are potent vasodilators that play a role in inflammation.
-Kinins and histamine
___ is a CNS neurotransmitter, it is also a vasoconstricting paracrine released by activated platelets, helps slow blood loss
Serotonin agonists called ____ that bind to 5 HT receptors and cause vasoconstriction. Used for migraines but may caused inappropriate cerebral vasodilation
Two hormones with significant vasoactive properties that have significant effects on the kidney's excretion of ions and water.
Atrial natriuretic peptide and angiotensin II
Most systemic arterioles are innervated by sympathetic neurons. The exception is arterioles involved in the?
-erection reflex of the penis and clitoris
-they are controlled indirectly by the parasympathetic innervation
Norepinephrine binding to alpha receptors on vascular smooth muscle causes
If sympathetic release of norepinephrine decreases, the arterioles ____. If sympathetic release of norepinephrine increases, the arterioles _____.
activation of vascular beta 2 receptors by epinephrine causes
drug that blocks the production of a chemical called angiotensin II(a powerful vasoconstrictor)
more than two-thirds of the cardiac output is routed to the _____,____,____,and _____
Total blood flow through all the arterioles of the body always equal the cardiac output. True or False
The main integrating center for coordinating of reflex control of blood pressure and distribution of blood to the tissues
-more specifically, the medullary network is known as the cardiovascular control center
The primary function of the cardiovascular control center is
to ensure adequate blood flow to the brain and heart by maintaining sufficient mean arterial pressure
the primary reflex pathway for homeostatic control of mean arterial blood pressure
stretch sensitive mechanoreceptors that located in the walls of the carotid arteries and aorta and monitor the pressure of blood flowing to the brain
When increased blood pressure in the arteries stretches the baroreceptor membrane, the firing rate of the receptor _____. If blood pressure falls, the firing rate of the receptor _____
The response of the baroreceptor reflex is quite rapid: changes in the CO and peripheral resistance occur within ____
two heartbeats of the stimulus
Heart function is regulated by antagonistic control. True or False.
-True. Increased sympathetic activity increases HR at the SA node, shorten conduction time through the AV node, and enhances the force of myocardial contraction
-Increased parasympathetic activity slows HR but has only a small effect on ventricular contraction
Pathway of Baroreceptor reflex. Starting with the constriction of arteriole A.
-Arteriole A decreases
-this increases resistance in arteriole A
-the resistance in all arteriole increases, TPR(total peripheral resistance)
-higher TPR (with the assist of CO) leads to higher mean arterial blood pressure
-higher MAP stretched baroreceptors and activated the baroreceptor reflex
-barereceptors reflex leads to a decreased CO
-a higher TPR and lower CO compensate and create a normal MAP
the decrease in blood pressure upon standing
why is the baroreceptor not always effective?
In extended bed rest or zero gravity conditions, the blood evenly distributed through the body rather than pooled in the lower extremities. This even distribution elevates MAP and triggers the kidneys to excrete what is perceives as excess fluid. This leads to a lower blood volume
The cardiovascular control center also has reciprocal communication with centers in the medulla that control breathing. True or False
True, consequently when the tissues need more oxygen, breathing increases and CO increases to compensate
what and where are the continuous capillaries?
-endothelial cells that joined to one another with leaky junctions
-in the muscle, connective tissue, and neural tissue
the exception of continuous capillaries.
the continuous capillaries in the brain have formed the blood-brain barrier, these have tight junctions to protect neural tissue from toxins available in the blood stream
what and where are the fenestrated capillaries?
-large pores that allow high volumes of fluid to pass rapidly between plasma and interstitial fluid.
- found primarily in the kidney and intestine where they associated with absorptive transporting epithelia
What and where are the sinusoids?
-Modified vessels that five times wider than a normal capillary, have fenestrations, and gaps.
-located in the bone marrow, liver, and spleen
-they are needed for blood cells and plasma proteins need to cross the endothelium to enter the blood
in the liver, the sinusoidal endothelium lacks a basal lamina, which allows
even more free exchance between plasma and interstitial fluid
the primary determinant for velocity
-it is not the diameter of an individual capillary but the total cross-sectional area of all the capillaries
the fastest flow is in the relatively small diameter ___ ____. and the slowest flow is in the ___ and ____ which collectly have the largest cross-sectional area
most capillary exchange takes place by ____ and ___
Diffusion and transcytosis
refers to the mass movement of fluid as the result of hydrostatic or osmotic pressure gradients
if direction of bulk flow is into the capillary, the fluid movement is called
if the direction of flow is out of the capillary, the fluid movement is known as
the two forces that regular bulk flow in the capillaries
osmotic pressure is determined by
solute concentration of a compartment
the main solute difference between plasma and interstitial fluid is___. which one has more of the solute?
-proteins, which are present in the plasma and mostly absent from interstitial fluid
the osmotic pressure created by the presence of these proteins
-colloid osmotic pressure, also known as oncotic pressure
Colloid osmotic pressure is the total osmotic pressure in a capillary. True or False.
Colloid osmotic pressure is higher in the plasma than in the interstitial fluid. Therefore, the osmotic gradient favors water movement by osmosis from the interstitial fluid into the plasma. true or false
hydrostatic(Ph) - colloid osmotic pressure (pi sign)
in the arterial ends net pressure is ___ and indicates ____
in the venous ends, net pressure is ____ and indicates _____
if the point at which filtration equals absorption occurred in the middle of capillary, then....
there would be no net movement of fluid
the vessels of the lympathetic system interact with three other physiology systems:
3 functions of the lympathetic system
-returning fluid and proteins filtered out of the capillaries to the circulatory system
-picking up fat absorbed at the small intestine and transferring it to the circulatory system
-serving as a filter to help capture and destroy foreign pathogens
Blind-end lymph vessels (lymph capillaries) lie close to all blood capillaries except those in the ___ and ____
-central nervous system
the clear fluid in lympathetic system
bean-shaped nodules of tissue with a fibrous outer capsule and an internal collection of immunologically active cells, including lymphocytes and marcophages
does the lympathetic system has a pump?
No, lymph flow depends primarily on waves of contraction of smooth muscle in the walls of the larger lymph vessels.
-it is also aided by one-ways valves, compression created by skeletal muscles, contractile fibers fibers in the endothelial cells
what is an edema?
an accumulation of fluid in the interstitial space usually caused by sprained wrist or ankle
Why is so important for lympathetic vessels to distribute and recycle the plasma proteins?
the body must maintain a low protein concentration in the interstitial because colloid osmotic pressure is the only significant force that opposes capillary hydrostatic pressure
the two causes of edema
-inadequate drainage of lymph
-blood capillary filtration that greatly exceeds capillary absorption
chronic condtion marked by gross enlargement of the legs and lower apendages when parasites block the lymph vessels
Factores that disrupt the normal balance between capillary filtration and absorption include
-an increase in capillary hydrostatic pressure
-decrease in plasma protein concentration
-an increase in interstitial proteins
A common cause of increased venous pressure is
-the right ventricle begins to fail but the left ventricle maintains CO, blood acculumates in the systemic circulation, when capillary hydrostatic pressure increases, filtration exceeds absorption, leading to edema
the main site of plasma protein synthesis
abdominal edema usually caused by protein malnutrition(also known as kwashiorkor)
a form of cardiovascular disease in which the coronary arteries become blocked by cholesterol deposits and blood clots
Coronary heart disease (CHD)
who has a higher risk of CHD? men or women? what is the exception?
-men have a 3-4 times higher risk
-but after women hit menopause, the risk equalizes among the sexes
the primary preventable cause of death in the US
two risk factors for cardiovascular disease
-elevated blood lipids
what is atherosclerosis?
-fatty deposits form inside arterial blood vessels.
the single largest killer of Americans
what is the healthy cholesterol?
high-density lipoprotein-cholesterol (HDL-C)
what is the lethal cholesterol?
low-density lipoprotein-cholesterol (LDL-C)
is all LDL-C bad?
no, LDL-C is necessary for a binding site of protein called apoB to help make cell membranes
if a clot blocks blood flow to the heart muscle this is called
-heart attack or myocardial infraction
what happens during a myocardial infraction?
Blocked blood flow in coronary artery cuts off the oxygen supply to myocardial cells supplied by that artery. as ATP declines, the contractile cells are unable to pump calcium out of the cell. the unusually high calcium concentration in the cytosol closes gap junctions in the damaged cells. the Closure electrically isolated the damaged cells so that they no longer contract, and it forces AP to find an alternate route from cell to cell. This causes an irregular heartbeat(arrhythmia) and could lead to cardiac arrest or death
the nine steps for development of atherosclerotic plaques
1= LDL-C cholestrol accumulates between the endothelium and connective tissue and is oxidized
2= macrophages ingest cholestrol and become foam cells
3= smooth muscle cells, attracted by marcophage cytokines, begin to divide and take up cholesterol
4=a lipid core acculumates beneath the endothelium
5= fibrous scar tissue forms to wall off the lipid core
6=smooth muscle cells divide and contribute to thickening of the intima
7=calcifications are deposited within the plaque
8= macrophages may release enzymes that dissolve collagen and convert stable plaques to unstable plaques
9=platelets that are exposed to collagen activate and initiate a blood clot
more than 90% of all patients with hypertension are considered to have ____ ____
-essential (or primary ) hypertension, with no clear cut cause other than heredity
what is a key cause of hypertension?
-the adaption of baroreceptor
-without input from the baroreceptors, the cardiovascular control center interprets the high blood pressure as "normal", and no reflex reduction of pressure occurs
what does the heart do to adapt to higher systemic resistance?
the heart muscle hypertrophies, increasing the size and strength of the muscle fibers
if cardiac output of the right heart remains normal while the output from the left side decreases, fluid collects in the lungs, this is called
-lack of oxygen due to this condition, further weakens the heart, and leads to congested heart failure
calcium channel blockers
-these drugs bind to calcium channel proteins, making it less likely that channels will open in response to depolarization.
-with less calcium entry, vascular smooth muscle dilates, while in the heart the depolarization rate of the SA node and the force of contraction decrease
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