Term
| What is the location of the major groups of neurons that regulate cardiovascular function? |
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Definition
| The reticular formation of the ventrolateral medulla and the lower third of the pons. |
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Term
| What is the role of the hypothalamus in regulation of cardiovascular function? |
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Definition
| The hypothalamus acts on the medulla in an integrative capacity (ex regulating body temp during exercise by adjusting blood flow to the skin). The region of the hypothalamus involved in temp regulation sends fibers to the cardiovascular center in the medulla. |
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Term
| What are the higher centers of the brain that function to regulate the cardiovascular system connected to? What actions do they influence? |
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Definition
Higher centers are connected the the hypothalamus and medulla. These higher centers influence such actions as:
-The increase in heart rate and blood pressure that occur in response to certain emotional states such as anger
-Excitation of the vasomotor center via the hypothalamus that occurs when certain areas of the cerebral cortex are stimulated
-changes in heart rate observed in trained sprinters on the starting block before a race |
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Term
| What groups of neurons in the brain stem regulate cardiovascular function? |
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Definition
| The vasomotor center neurons. |
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Term
| Where is the vasomotor center primarily located? |
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Definition
| Bilaterally in the medulla oblongata. |
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Term
| What are the functional areas of the vasomotor center? |
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Definition
-Vasoconstrictor- activates vasocontrictor nerves
-vasodilator region-fibers from this region project to and inhibit neurons in the vasoconstrictor region
-Sensory area-modulates activities of the vasonstrictor and vasodilator regions |
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Term
| Where is the vasoconstrictor located, what is its role in the regulation of cardiovascular function, and where do its neurons project to? |
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Definition
| The vasocontrictor region is a part of the vasomotor center and is therefore located in the medulla oblongata. It functions to activate vasoconstrictor nerves. Neurons from the vasoconstrictor region project fibers to the spinal cord where they activate preganglionic vasoconstrictor neurons of the sympathetic nervous system. |
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Term
| What functional area of the vasomotor center can be inhibited to result in dilation? |
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Definition
| If the vasodilator region is inhibited then vasodilation occurs. Fibers from the vasodilatory region project to and inhibit neurons in the vasocnstrictor region. |
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Term
| Impulses from the lateral portion of the vasomotor center have what effect on the heart? What route do these impulses take to reach the heart? |
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Definition
| Fibers from the lateral portion of the vasomotor center transmit impulses via the sympathetic nerves increasing heart rate and contractility. |
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Term
| How does the vasomotor center signal for the heart rate to decrease? |
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Definition
| Fibers from the medial portion of the vasomotr center transmit cardioinhibitory signals to the dorsal motor nuclei of the vagus nerves that decrease heart rate and contractility via the vagus nerves. |
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Term
| What accounts for heart rate being lower than the intrinsic firing rate of the SA node? |
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Definition
| Under resting conditions the dorsal vagal nucleus and nucleus ambiguus of the medulla are tonically active and elicit bradycardia. |
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Term
| What portions of the vagus nerve inhibit the SA node? The AV node? |
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Definition
| The right vagus primarily inhibits the SA node whereas the left vagus primarily inhibits AV node conduction. |
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Term
| T/F. Ventricular myocardium is heavily innervated by the vagus nerve. |
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Definition
| False. The ventricular myocardium has only sparse vagal innervation. |
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Term
| How are vagal actions mediated? |
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Definition
| By postganglionic fibers releasing acetylcholine. |
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Term
| How can tachycardia and vasoconstriction be induced in the heart? |
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Definition
| Stimulation of certain regions in the reticular formation of the medulla oblongata. |
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Term
| Does vagal or sympathetic stimulation have a faster decay in regulation of heart rate? |
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Definition
| Vagal stimulation decays much faster. |
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Term
| How are the vasoconstrictor effects of the sympathetic nerves on blood vessels mediated? |
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Definition
| Noradrenergic fibers (fibers that release norepinephrine) mediate the effects of sympathetic nerves on blood vessels. |
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Term
| Define positive chronotropy. |
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Definition
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Term
| Define negative dromotropy. |
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Definition
| Decreases conduction velocity. |
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Term
| Define positive inotropy. |
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Definition
| Increases the force of contraction. |
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Term
| What is the most important adrenergic receptor with respect to modulating cardiac function? |
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Definition
| The beta one receptor is most important. It induces + chronotropic, inotropic, and dromotropic effects |
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Term
| What stimulates alpha 1 receptors in the heart? What effect does this have? |
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Definition
| Alpha 1 receptors are stimulated by the sympathetic nervous system and results in a small positive inotropic effect. |
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Term
| What stimulates beta 2 receptors in the heart and blood vessels? What is the effect? |
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Definition
Sympathetic stimulation of the beta 2 receptors produces the same effects of stimulation of the beta one receptor:
+ chronotrophy,
+ inotrophy
+ dromotropy |
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Term
| What does activation of the alpha one receptor stimulate? |
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Definition
| Alpha one stimulation promotes smooth muscle contraction. |
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Term
| IF beta 2 receptors are activated and alpha adrenergic receptors are activated what will happen? |
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Definition
| Beta 2 receptors stimulate vasodilation and alpha receptors stimulate vasoconstriction, however alpha receptors normally overwhelm the effects of beta two receptors. |
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Term
| In the heart and blood vessles what division of the nervous system releases acteylcholine? What type of receptor does it bind to? |
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Definition
| ACh is released by nerve terminals of the parasympathetic nervous system and binds to M2 muscarinic receptors. |
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Term
| What effects do M2 muscarinic receptors have on the heart and blood vessels when activated? |
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Definition
| M2 muscarinic receptors have dramatic negative chronotropic and dromotropic effects, modest negative inotropic effect and also causes a decrease in the rate of atrial relaxation. |
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Term
| What inhibits NE release? |
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Definition
In the heart and blood vessels alpha 2 adrenergic receptors inhibit NE release.
In the heart M2 muscarinic receptors also inhibit NE release. |
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Term
| In the heart and blood vessels what promotes NE release? |
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Definition
| Beta 2 adrenergic receptors promote NE release. |
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Term
| What is the most important extrinsic regulator of heart rate? |
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Definition
| The autonomic nervous system--both sympathetic and parasympathetic fibers innervate the SA node and modulate heart rate. At rest sympathetic tone predominates. |
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Term
| What is the function of the baroreceptor reflex? |
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Definition
| The baroreceptor reflex is one of the most important mechanisms for short term regulation of blood pressure. |
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Term
| How are baroreceptors stimulated? |
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Definition
| Baroreceptors are stretch receptors and are stimulated by distention. |
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Term
| How are baroreceptor impulses from the carotid sinus transmitted to the CNS? From the aortic arch? |
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Definition
| From the cartodi sinus baroreceptor impulses are stransmitted to the CNS via the glossopharyngeal nerve and from the aortic arch via the vagus nerve. |
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Term
| What specifically do aortic and carotid baroreceptors monitor changes in? |
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Definition
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Term
| Baroreceptor firing ______ with increasing blood pressure and ______ with decreasing blood pressure. Baroreceptors are most sensitive to fluctuations in pressure within what range of pressure? |
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Definition
| Increase with increasing blood pressure and decrease with decreasing. Most sensitive to fluctuation s in pressure in the normal range of arterial pressure. |
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Term
| Describe the flow of the baroreceptor reflex after when there is a decrease in arterial pressure. |
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Definition
-Decreased arterial pressure leads to decreased firing of the baroreceptors. -Afferent signals are integrated in the medulla
-increased sympathetic activity and decreased parasympathetic activity
-increased vasoconduction, increased inotropy, and increased heart rate.
-increased cardiac output and vasoconstriction lead to a restoration in blood pressure. |
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Term
| T/F. Increased temperatures lower heart rate. |
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Definition
| False. Heart rate increases with higher temperatures (fever). |
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Term
| What are some factors that affect heart rate? |
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Definition
-temperature
-circulating hormones
-emotions
-exercise |
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