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Define Hypertension
an elevated systemic arterial blood pressure that is consistently elevated over time.
Systolic 140 or greater
diabolic 90 or greater
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Define prehypertension
a category used to indicate an individual at risk of developing hypertension.
Systolic 121-139
Diabolic 81-89
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Define Hypotension
is blood pressure that is too low to adequately deliver oxygen and nutrients to vital organs.
Typically defined by signs and symptoms rather than by blood pressure #'s
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Loss of elasticity in arteries leads to
hypertension
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Heart works harder against increased
resistance
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Atherosclerosis leads to hypertension two ways:
- decrease in elasticity of arteries
- decrease in diameter of arteries
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Hypertension and Hypotension:
Increase Cardiac Output:
Increased blood volume; skeletal muscle; respiratory pump; vasoconstriction of veins
Increased venous return;
Increased stroke volume;
Increased cardiac output;
Increased blood pressure
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Hypertension and Hypotension:
Increase Cardiac Output:
Decreased parasympathetic impulses
increased heart rate;
Increased cardiac output;
Increased blood pressure
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Hypertension and Hypotension:
Increase Cardiac Output:
Increased sympathetic impulses and hormones from adrenal medulla
increased heart rate;
increased stroke volume;
increased cardiac output;
increased blood pressure
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Hypertension and Hypotension:
Increase Vascular Resistance:
R = nL/r4 ---> explain how "n" increases vascular resistance
increased number of RBC's, as in polycythemia;
increased blood viscosity;
increased systemic vascular resistance;
increased blood pressure
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Hypertension and Hypotension:
Increase Vascular Resistance:
R = nL/r4 ---> explain how "L" increases vascular resistance
increased body size, as in obesity;
increased total blood vessel length;
increased systemic vascular resistance;
increased blood pressure
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Hypertension and Hypotension:
Increase Vascular Resistance:
R = nL/r4 ---> explain how "r4" increases vascular resistance
Vasoconstriction;
increased systemic vascular resistance;
increased blood pressure
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Shock is a failure of the
cardiovascular system to deliver enough oxygen and nutrients to meet cellular needs.
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The body utilizes a _______ feedback loop to raise blood pressure.
negative;
Homestatic mechanisms can compensate for as much as 10% of total blood loss
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Baroreceptors in the kidneys and aorta sense falling blood pressure. Responses include:
Renin release initiates the renin-angiotensin-aldosterone system which acts to release aldosterone leading to conservation of salt and water in the kidneys and vasoconstriction of vessels.
ADH release which conserves water from kidneys
Increased sympathetic response causing an increase in heart rate and contractility and vasoconstriction
*The net result is to raise blood pressure
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The baroreceptor reflexes are homeostatic loops that
regulate blood pressure
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Baroreceptors sensing pressure are located in the
aorta, internal carotid arteries, and other large arteries in the chest and neck.
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An increase in blood pressure is detected by stretching at the baroreceptors. Impulses are sent at a faster rate to the cardiovascular center in the medulla. The response is
1. Nerves from the medulla increase parasympathetic stimulation by the vagus nerve and decrease sympathetic stimulation.
2. Rate of impulses on sympathetic neurons to the vessels slow, causing vasodilation.
*blood pressure drops as a result.
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When blood pressure is low, baroreceptors are stretched less and send impulses at a slower rate. The response is
1. The cardiovascular center decreases parasympathetic stimulation and increases sympathetic stimulation.
2. Adrenal medulla increases secretion of epinephrine and norepinephrine.
3. Blood vessels constrict blood pressure increases as a result.
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Chemoreceptors sense the
chemical composition of the blood
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Chemoreceptors of the carotid bodies and aortic bodies detect
pH, levels of O2 and CO2
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↑ CO2
↓ O2
↓ pH
Increase what?
respiratory rate
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Arteries have thick layer of _______ muscle. This muscle is responsive to _________ stimulation.
smooth; sympathetic (epinephrine and norephinephrine)
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Three types of smooth muscle receptors for sympathetic control for blood pressure?
α1 adrenergic: Epi/NE cause vasoconstriction
α2 adrenergic: Epi/NE cause vasoconstriction
β2 adrenergic: Epi/NE cause vasodilation
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Vasoconstriction does what to blood pressure?
increases
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Vasodilation does what to blood pressure?
decreases
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Hormones provide ____-_____ control of blood pressure. The renin-aniotensin-aldosterone system acts to conserve more
long-term;
sodium and subsequently water from the kidneys and eliminate potassium. This causes an increase in blood volume and pressure.
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The Venous Reserve:
About 60% of blood is in the
venous system
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If massive blood loss occurs, baroreceptors of carotid sinus signal ________. Nervous system can mobilize about 1 Liter blood from organs with venous reserves... Which are?
emergency;
- spleen
- liver
- large abdominal veins
- venous plexi beneath skin
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Define anastomoses
mostly, arteries branch like a tree as they move away from the heart. At anastomosis, branches fuse often to provide a "backup plan" is one route of blood supply is blocked.
- example: Brain
- cerebral arterial circle (circle of willis)
base of brain (inferior view): anastomoses between internal carotid and posterior cerebral
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Coronary arteries that are completely obstructed may result in
myocardial infarction (heart attack). Heart tissue distal to the obstruction dies.
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Lymphatic duct drains into
subclavian vein
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All lymphatic vessels eventually anastomose into
lymphatic duct
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Fetus unable to nutrify or oxygenate blood, relies on
mother for these functions
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