Control of blood flow Flashcards
What is acute control?
local blood flow control that is rapid (occurs in seconds to minutes). It includes the vasodilator theory and the oxygen (nutrient) lack theory.
What is long-term control?
local blood flow control that occurs over a long period. An increase in the size and numbers of vessels results.
What is the vasodilator theory?
Theory of SHORT TERM local blood flow control. As metabolism increases, oxygen availability to the tissues decreases, and vasodilators are formed.
When do vasodilators form?
under conditions of low oxygen (hypoxia).
What are some examples of vasodilators?
adenosine, CO2, histamine, K+, H+
What is the oxygen (nutrient) lack theory?
a decrease in oxygen causes blood vessel relaxation and dilation..
What is vasomotion?
the cyclical opening and closing of pre-capillary sphincters. They open in proportion to the needs of tissues.
What is hyperemia?
increased blood flow
What is reactive hyperemia?
increased blood flow after a blocked artery is no longer blocked. The flood flow increases 4 -7 x, which can be fatal.
What is active hyperemia?
When any tissue becomes active, the rate of blood flow increases.
An increase in blood flow is ____ proportional to the rate of metabolism.
directly
An increase in blood flow is ____ proportional to the rate of arterial oxygen saturation.
inversely
In tissues, autoregulation will decrease high blood flow, but it will not decrease what?
blood pressure; high blood flow is regulated by negative feedback.
What are two theories of autoregulation?
metabolic and myogenic
What is the metabolic theory of autoregulation?
increase in blood flow -> too much oxygen or nutrients -> vasodilators washed out
What is the myogenic theory of autoregulation?
stretching of vessels -> reactive vasculature constriction -> blood flow returned to normal.
Generally, when blood flow increases, ___ also increases.
blood pressure; an acute response increases in pressure more rapidly than a long-term response.
What three organs use special acute flow mechanisms?
kidney (tubuloglomerular feedback), brain and skin (blood flow linked to body temperature and is regulated by sympathetic nerves to the CNS).
What is the special acute flow control mechanism for the brain?
increase in CO2/H+ -> cerebral vessel dilation -> washing out of excess CO2/H+
In endothelial cells, what molecule initiates the process of vasodilation?
cyclic GTP (cGTP)
in endothelial cells, what molecule activates cGTP?
Nitrous oxide (NO)
In endothelial cells, cGMP activates what proteins?
protein kinases.
Protein kinases directly activate the blood vessels to do what?
dilate
In damaged endothelial cells, what protein is secreted?
endothelin; it causes vasoconstriction.
In damaged endothelial cells, what molecules is not released that would otherwise activate cGTP and hence vasodilation?
NO
What are some vasoconstrictors?
norepinephrine, epinephrine, angiotensin II, vasopressin (ADH)
What are some vasodilators?
bradkinins and histamine
What kind of vessel does the sympathetic nervous system not innervate?
capillaries
Innervation from the sympathetic nervous system causes the vessels to do what?
constrict
The vasocontrictor area in the upper medulla does what?
transmits continuous signals to blood vessels, which results in sympathetic vasoconstriction tone.
The vasodilator area in the lower medulla inhibits what other area?
vasoconstrictor area
Where is the sensory area in the brain?
the medulla; it receives signals from the vagus nerves and glossopharyngeal nerves.
What is the sensory area controlled by?
reticular substance, hypothalaus and cerebral cortex
What is the function of basoreceptors?
They inhibit vasoconstrictor areas and activate vasodilator centers. They are found in the common carotid arteries and the aorta.
The glossopharyngeal nerve sends signals to what area of the brain?
sensory area
Signals from the sensory area in the brain are send to which region?
Vasodilator area
The vagus nerve sends signals to what area of the brain?
sensory area.
What are carotid bodies?
chemosensitive sells that sense hydrogen ion concentration. They are important for respiration.
What does the adrenal medulla secrete?
epinephrine and norepinephrine (sympathetic)
The rapid neural control of arterial pressure includes what simultaneous changes to vessels?
constriction of the arteries and veins and increasd heart rate. The response is rapid and leads to decreased cardiac output.
loss of vasomotor tone (e.g. sympathetic innervation) results in a _____ of blood pressure?
decrease
When are baroreceptors stimulated?
when arterial pressure is low.
Baroreceptors send signals where?
cerebral cortex, hypothalamus and reticular substance (e.g. the sensory area)
Baroreceptors function to do what?
activate vasodilator area, which can cause an increase or decrease in pressure. Barorecepors function to reduce the minute-by-minute variation in arterial lpresure.
As baroreceptors are activated, what happens to blood pressure?
the pressure increases , then levels off at around 240 mm Hg
When the vagus nerve has been cut, what happens to blood pressure?
It increases by 50%
When baroreceptors are denervated, what happens to blood pressure?
the pressure is highly variable.
What do low pressure atrial reflexes do?
minimize arterial pressure changes in response to blood volume.
Increase of atrial stretch results in what?
the kidneys will dilate, which causes an increase of kidney fluid loss and decreased blood volume. Heart rate increases, ADH and Na+ reabsorption decrease in the kidneys.
What is the formula for arterial pressure?
cardiac output x total peripheral resistance.
Arterial pressure rises when what kind of resistance is acutely increased?
total peripheral resistance
How do kidneys return arterial pressure back to normal?
pressure diuresis or pressure natriuresis
What is primary hypertension?
increased blood pressure. It results in increased cardiac output, sympathetic stimulation, angiontensin II & aldosterone, and impariment of natriuses and secretion of salt & water
What are major factors that cause primary hypertension?
weight gain and sendentary lifestyle.
What are causes of secondary hypertension?
kidney tumors, kidney vessel constriction, preeclampsia, neurogenic hypertension, genetics
Secondary hypertension can be caused by many abnormalities in what organ?
kidney
Hypertension can be caused by the endocrine system. What are some disorders of the endocrine system that cause hypertension?
hyperthroidism/hypothyroidism, pregnancy
What are some cardiovascular causes of hypertension?
increased intravascular volume, increased cardiac output, rigid aorta
What are some neurologic causes of hypertension?
increased intracranical pressure, sleep apnea, acute stress, psychogenic factors
What are some general contributing factors to hypetension?
genetics, stress, obesity, smoking, physical inactivity, heavy consumption of salt.
Factors that lead to decreased resistance and blood pressure include what?
nitric oxide, prostacyclin, kinins, ANP, decreaed beta-andrenergic factors.
What are some cardiac factors that lead to decreased cardiac output?
decreased blood volume, heart rate and contractility.
What cardiac conditions lead to incresed blood pressure?
increased heart, volume, and contraction.
What factors cause incresed resistance and blood pressure?
increased angiotensin II, catecholaimnes, thromboxane, alpha-adrenergic factors.
What are the humoral vasoconstrictors?
angiotensin II, catecholamines, endothelin
Wht are the huoral vasodilators?
kinins, prostagalandins, nitric oxide.
What does chronic hypertension lea to?
early heart failure, cerebral infarct, kidney failure
What is the major characteristic of atherosclerosis?
the presence of lesions within the intima of the vessel wall that protrude into the vessel lumen.
What are risk factors (non-modifiable) for athersclerosis?
age (old), gender (post-menopausal women), genetics
What are modifiable risk factors for athersclerosis?
hyperlipidemia (high cholesterol), hypertension, smoking diabetes, inflammation (correlated with high cholesterol), hyperhomocystinemia (errors in metabolism), metabolic syndrome (obesity & insulin ressitance)
What is hyperhomocystinemia
A disorder in which metabolism is affected; it causes hypertension and premature vascular disease.
What is metabolic syndrome?
Syndome associated with insulin resistance. It causes obseity, increased lipids and cholesterol levels and hypertension.
Hypertension can be caused by what types of injury to the vessel?
Endothelial injuries. The intima thickens and an atheroma may result.
The accumulation of lipoproteins, especially oxidized LDL, can cause what?
hypertension
When monocytes adhere to damaged vessel epithelium, what do leukocytes and endothelial cells release?
growth factors that promote smooth muscle cell proliferation.
Smooth muscle proliferation converts fatty streaks into what?
matura atheroma
What is an atheroma?
a cap of smooth muscle cells, macrophages and foam cells that overlie a necrotic center composed cell debris, foam cellsa nd calcium.
What are the earliest lesion in vessels called?
fatty streaks
After plaques are deposited in the lumen and apoptose, what process do they undergo?
calcification
Where is athersclerosis most common?
lower abdominal aorta and the coronary arteries.
Where is athersclerosis leas common?
popliteal arteries, interal carotid arties and the circle of willis.
Short term control of arterial pressure results in what?
sympathetic control of the vascular resistance, capaacitance and cardiac pumping ability.
Long term control of arterial pressure is controlled by what?
nervous and hormonal controls, as well as local controls in the kidney that regulate salt and water excretion.
As arterial pressure increases, what happens to urinay output?
it also increases
An increase in arterial pressure results in an increase of what to things?
increased urine output and sodium output.
Pressure diuresis is associated with what?
increased urine output.
Pressure natriuresis is associated with what?
increased sodium output.
What are the primary determinants of long-term arterial pressure lvel?
degree of the pressure shift of the renal output curve and the level of water/salt intake.
How does increased salt intake affect arterial pressure?
Pressure is not greatly changed by salt intake.
What is chronic hypertension?
Blood pressure is greater than 110 mm Hg (135/90)
What are the lethal effects of chronic hypertension?
early heart failure, coronary heart disease, heart attack, cerebral infarct, destruction of areas of the kidney
When the renin-angiotensin curve is blocked, what happens to arterial pressure?
it decreases
What is “one-kidney” Goldblatt hypertension?
hypertension that results from the removal of one kidney and the constriction of the remaining renal artery.
