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73 Cards in this Set
- Front
- Back
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If nerve impulses to the heart are blocked, its intrinsic rate will average around ____ beats per minute
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100
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Under normal at-rest conditions, the heart rate is kept in check by the _________nerves that originate in the dorsal motor nucleus of the vagus.
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parasympathetic
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Heart rate is increased when ______control is reduced and /or by direct _______stimulation of nerves.
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vagal
sympathetic |
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Sympathetic outflow for control of the heart originates in the ______.
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rostral ventrolateral medulla
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Blood flow (F) =
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volume of blood moving through a vessel per unit time (ml/min)
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Velocity =
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the distance the blood flow per unit time (cm/sec)
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Resistance (R) =
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The hindrance to the movement of blood through a vessel
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Pressure (P)
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= The force needed to move blood through the vessel
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Total Peripheral Resistance (TPR)
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= refers to the resistance of the entire vascular system
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Blood flow tends to become _____(can be detected as a murmur) when flow velocity is fast, when the diameter of the vessel is _____ or when there are irregularities in the vessel wall, i.e., plaque.
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turbulent
large |
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Flow =
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Pressure/Resistance
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Sympathetic discharge will release _______ which causes vasoconstriction of arteries, thus reducing the radius of the vessel causing a large increase in resistance to blood flow
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norepinephrine
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the major function of the arterial system is to distribute blood to the _____ for exchange of nutrients and wastes.
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capillary beds
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_______are described as compliance vessels
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Arteries
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Compliance =
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increase in volume/increase in pressure
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The ___ compliant an artery (aorta) the more work the heart has to perform in order to maintain a given cardiac output.
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less
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______ is the pressure in the artery averaged over time.
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Mean arterial pressure
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CO =
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H.R. (Heart Rate) X Stroke Volume
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Pulse Pressure =
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Systolic pressure - Diastolic pressure
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The two factors that act to determine arterial pressure (Pa) at a given time are
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blood volume and arterial compliance.
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is the difference between systolic and diastolic pressure
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Pulse pressure
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About ____% of the systemic blood volume is located on the venous side of the circulatory system
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75%
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Under______ stimulation, the veine can constrict
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adrenergic
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is a portion of the circulation where nutrients, water, hormones and waste products are exchanged
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microcirculation
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are responsible for regulation of vascular resistance
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small arterioles
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regulate the vessel radius altering resistance
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Smooth muscle cells
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radius is determined by the _________pressure gradient (intravascular - extra vascular pressure)
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transmural
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________are considered the major resistance vessels - thus they regulate blood flow to the capillaries
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muscular arterioles
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Law of LaPlace: (Fig. 20-3)
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T = Pr
T = Tension in the vessel wall (dynes/cm) P = Transmural pressure (diastolic?) r = Radius of vessel |
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occurs in the aorta, as the vessel dilates (radius gets large) wall tensions may become high enough to cause the vessel to rupture.
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an aneurysm
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role of the circulatory system is to provide a method for the
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supply of nutrients and removal of waste from tissues as well as help regulate temperature.
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blood flow remains relatively constant over a wide range of blood pressure changes. This concept refers to?
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autoregulation.
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Extrinsic control of blood flow is mainly under the control of the
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sympathetic nervous system.
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Local and Hormonal agents: Vasodilators
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· Bradykinins
· Serotonin · Histamine · Some Proslaglandins · Endothelial-Derived Relaxing Factor (Nitric Oxide) |
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Local and Hormonal agents: Vasoconstrictors
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· Norepinehrine
· Epinephrine · Angiotension II · Vasopressin (ADH) · Endothelin |
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(increase) will stimulate muscle to contract.
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Ca++
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(increase) in plasma can lead to relaxation in smooth muscle.
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K+
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(increase) in plasma is a strong vasodilator.
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Mg++
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can cause the carotid sinus to become stiffer, causing sensitivity to decrease.
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Hypertension
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The resting coronary blood flow in humans averages______ During very strenuous exercise, cardiac output can increase 6X or more - coronary blood can increase up 4x - thus if coronaries are narrow there is a problem supplying enough O2 and nutrients.
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225 ml/min.
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occurs when there is a reduction in oxygen supply or when an increased oxygen demand cannot be met by arterial supply.
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Ischemia
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The most common cause of myocardial ischemia is
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atherosclerosis.
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classic neurotransmitter for both presynaptic fibers of the parasympathetic and sympathetic divisions is
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acetylcholine.
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There are two types of acetylcholine receptors in the autonomic ganglia and at target organs:
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nicotinic and muscarinic.
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The sympathetic postganglionic neurons release
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norepinephrine.
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The parasympathetic postganglionic neurons release
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acetylcholine.
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the second messenger for beta receptors is
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cyclic AMP.
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Stimulation of beta receptors increases cyclic AMP which will cause
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relaxation of smooth muscle
vasodilatation of arteries bronchodilation in the respiratory system reduction of tone in the gastrointestinal tract. |
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Stimulation of beta receptors will increase
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heart rate and contractility which increases cardiac output.
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Stimulation of Alpha 1 and Alpha 2 receptors located in smooth muscle will cause
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contraction of the muscle vasoconstriction of arteries and arterioles
bronchial constriction in the respiratory system · contraction of sphincters in the GI tract |
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Stimulation of Alpha 2 receptors in certain cardiovascular regulatory areas of the brain will lead to a
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reduction in sympathetic outflow, thereby causing a drop in blood pressure.
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physiological response of smooth muscle in an organ system is related to the number and type of _____ receptors
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adrenergic
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_______ system has more alpha 1 receptors than beta receptors
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arterial
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_________system has more beta receptors, thus catecholamine stimulation will lead to relaxation
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bronchial
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. How would increasing the radius of an arteriole from 1mm to 2mm affect arterial resistance?
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Resistance to flow is inversely proportional to the fourth power of the radius of the blood vessel. The resistance decreases 16 fold.
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What is meant by the term Laminar flow?
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Laminar Flow is streamlined flow. It is a parabolic profile of velocity within a blood vessel, with the velocity of blood flow highest in the center of the vessel and lowest toward the vessel walls
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What is the difference in resistance of vessels in series versus resistance of vessels in parallel?
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Series resistance is illustrated by the arrangement of blood vessels within a given organ. Each organ is supplied with blood by a major artery and drained by a major vein. Within the organ, blood flows from the major artery, to smaller arteries, to arterioles, to capillaries, to venules, to veins. The total resistance of the system arranged in series is equal to the sum of the individual resistances.
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What is the difference in resistance of vessels in series versus resistance of vessels in parallel?
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Parallel Resistance is illustrated by the distribution of blood flow among the various major arteries branching off the aorta. The cardiac output flows through the aorta and then is distributed, on a percentage basis, among the various organ systems. Thus, there is parallel, simultaneous blood flow through each of the circulations ( e.g. renal, cerebral, coronary). The total resistance in a parallel arrangement is less than any of the individual resistances.
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How do changes in viscosity affect blood flow through a vessel?
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The greater the viscosity, the less the flow in a vessel if all other factors are constant.
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Which vessels, vein or arteries, are the most compliant? Why?
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The compliance of a blood vessel describes the volume of blood the vessel can hold at a given pressure, and it is related to the distensibility of that vessel.
Compared to the arteries, the veins are more compliant. This is due to the fact that veins can hold large volumes of blood in low pressure. Compliance in the arteries is low because they hold much less blood than the veins, and they do so at high pressure. |
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How does age affect the compliance of arteries? Explain? See Fig 19-4
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As people age the characteristics of the arterial walls change. They become less distensible and less compliant. Hence, for any pressure above about 80mm Hg, the compliance decreases with age. This change in compliance is a manifestation of the increased rigidity (atherosclerosis) of the system caused by progressive changes in the collagen and the elastin content of the arterial walls.
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How do you measure arterial pressure?
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In measuring arterial blood pressure, several factors have to be taken into account. Arterial BP is determined by 2 major physical factors- arterial blood vol. and arterial compliance. These physical factors are in turn affected by certain physiological factors- heart rate, stroke vol. Cardiac output (HR * SV) and peripheral resistance.
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Discuss the factors that will act to change arterial pressure, i.e., Total Peripheral Resistance (TPR), Cardiac Output (CO).
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The mean arterial pressure depends on two physiological factors: cardiac output and peripheral resistance. If the cardiac output and total peripheral resistance is increased, the arterial pressure will increase.
Mean arterial pressure = Cardiac output x Total peripheral resistance CO = Heart Rate x Stroke Volume |
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Discuss how a change in stroke volume or arterial compliance would affect the pulse pressure.
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An increase in stoke volume will cause an increase in pulse pressure. A decrease in stoke volume will cause a decrease in pulse pressure. A decrease in arterial compliance will increase pulse pressure. A highly compliant aorta (i.e., less stiff) has a smaller pulse pressure for a given stroke volume into the aorta. A larger stroke volume produces a larger pulse pressure at any given compliance.
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Pulse Pressure is the difference between systolic and diastolic pressure. How would pulse pressure be affected in a person with severe congestive heart failure? In a person with aortic regurgitation? Explain.
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People with severe CHF are likely to have very small arterial pulse pressures because their stroke volumes are abnormally small. People with aortic regurgitation have large stroke volumes and increased arterial pulse pressures.
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How would atherosclerosis affect pulse pressure and compliance of large vessels?
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Atherosclerosis is a condition in which fatty material is deposited along the walls of arteries. This fatty material thickens, hardens, and may eventually block the arteries. Eventually, this fatty tissue can erode the wall of the artery, diminish its elasticity (stretchiness) and interfere with blood flow. Thus, the compliance would decrease and the pulse pressure would increase.
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circulatory system. Under adrenergic stimulation, the vein can constrict. Explain how a venoconstriction would affect the preload on the heart. How is this related to the Frank-Starling Principal?
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About 75% of the systemic blood volume is located on the venous side of the
This means that the venous system serves as a reservoir for much of the circulation. Constriction of the venous bed would propel blood “forward” into the RV and then to the LV. The result is an increase in ventricular end-diastolic volume (increased preload). Higher volume (preload) will stretch the ventricles and result in an increased force of contraction from the RV and the LV by the Frank-Starling Principle. |
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What is meant by critical closing pressure?
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Critical closing pressure: Progressive reduction in the intravascular pressure causes the decrease of vessel diameter and the decrease of tension in the wall of the vessel (Laplace’s Law) which leads to cessation of blood flow---the pressure that causes the cessation of blood flow is referred to as the critical closing pressure
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Transmural pressure?
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Transmural pressure: intravascular minus extravascular pressure which influences the contractile state of the precapillary vessels. An increase in transmural pressure, whether produced by an increase in venous pressure or by dilation of arterioles, results in contraction of the terminal arterioles. Decreased transmural pressure causes precapillary vessel relaxation.
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Define idiopathic cardiomyopathy.
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Idiopathic cardiomyopathy is dilation of the heart that occurs in heart failure produced by the combination of a weakened myocardium and increased left ventricular wall stress (determined by Laplace’s equation) which results in low cardiac output. A new remodeling procedure, ventriculotomy, can reduce diastolic volume of the left ventricle and enhance its efficiency.
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How do metabolites act to regulate vascular smooth muscles?
Vasoconstriction Agents |
The endothelium can synthesize endothelin which is a potent vasoconstrictor peptide. The presence of endothelin causes the vascular smooth muscle of the capillaries to contract, and may be involved in atherosclerosis, pulmonary hypertension, CHF, and renal failure.
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How do metabolites act to regulate vascular smooth muscles?
Vasodilatation Agents |
Two vasodilation agents synthesized by the endothelium are prostacyclin and nitric oxide (NO). Prostacyclin relaxes vascular smooth muscle via an increase in cAMP. The primary function of prostacyclin is to inhibit platelet adherence to the endothelium and platelet aggregation, thus preventing clot formation. Nitric oxide is produced by the endothelial cells when they are stimulated by a vasodilator agent
Nitroprusside, a vasodilator agent acts directly on the vascular smooth muscle. Substances such as adenosine, hydrogen ions, carbon dioxide, and potassium ions arise in the parenchymal tissue and cause vasodilation by direct action on the vascular smooth muscle. |
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Metabolic Substances that are Vasodilators:
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• Adenosine
• Prostaglandin • Low PO2 levels • K+: released w/ Skeletal muscle contraction • Inorganic Phosphate ions: released w/ Skeletal muscle contraction • Interstitial fluid osmolarity-increased during skeletal muscle contraction • Bradykin- Parasympathetic vasodilator polypeptide assist in cutaneous vasodilatation |
