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33 Cards in this Set
- Front
- Back
Vessels innnervated by sympathetic nervous system:
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All vessels except capillaries
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Distribution of vasoconstrictor nerve fibers:
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More in kidneys, intestines, spleen and skin but less in skeletal muscle and brain.
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Vasomotor center:
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Bilaterally in the reticular substance of the medulla and of the lower third of the pons.
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Parasympathetic impulses is transmitted to cardiovascular system through:
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Vagus nerve
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Sympathetic impulses is transmitted to cardiovascular system through:
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Spinal cord and peripheral sympathetic nerve fibers
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Vasoconstrictor area:
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Bilaterally in the anterolateral portions of the medulla.
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Vasodilator area:
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Bilaterally in the anterolateral portions of lower half of medulla. They inhibit vasoconstrictor acticity
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Vasomotor tone:
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One half to two impulses fired per second by vasoconstrictor center maintain normal vasoconstrictor tone.
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Lateral portions of vasomotor center:
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Transmits excitatory impulses to the heart which increases heart rate and contractility.
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Medial portions of vasomotor center:
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Sends signals to adjacent dorsal motor nuclei of vagus nerves which sends parasympathetic signals to the heart to decrease heart rate and slightly decrease contractility.
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Hypothalamus and its relation to vasomotor center:
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Posterolateral portions cause excitation while the anterior portion cause mild excitation of inhibition.
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Norepinephrine:
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Secreted at the endings of the vasoconstrictor nerves and act on alpha adrenergic receptors of smooth mm.
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Activation of adrenal medulla:
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Sympathetic innervation in the same way as for vessels. Cause adrenal medulla to secrete epi and norepi into the blood stream.
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Emotional fainting- Vasovagal syncope:
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Disturbing thoughts in cerebral cortex from emotional disturbances--> vasodilatory center of anterior hypothalamus next to vagal centers of medulla---> vagus nerve to heart (slowing of HR) and through spinal nerves to the sympathetic vasodilator nerves of muscles (vasodilatation)
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Most important function of nervous system in regulation of circulation:
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Ability to cause rapid increase in arterial pressure by stimulation of vasoconstrictor and cardioaccelerator functions of sympathetic nervous system + blockage of parasympathetic NS
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Rapid increase of arterial pressure by the nervous system:
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1. Constriction of arterioles (increases total peripheral resistance)
2. Constriction of veins and large vessels (Redistribution of blood from periphery to the heart --> increased preload--> increased force of contraction) 3. Direct effect on heart (increased HR and contractile force) |
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Norepinephrine:
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Secreted at the endings of the vasoconstrictor nerves and act on alpha adrenergic receptors of smooth mm.
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Activation of adrenal medulla:
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Sympathetic innervation in the same way as for vessels. Cause adrenal medulla to secrete epi and norepi into the blood stream.
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Emotional fainting- Vasovagal syncope:
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Disturbing thoughts in cerebral cortex from emotional disturbances--> vasodilatory center of anterior hypothalamus next to vagal centers of medulla---> vagus nerve to heart (slowing of HR) and through spinal nerves to the sympathetic vasodilator nerves of muscles (vasodilatation)
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Most important function of nervous system in regulation of circulation:
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Ability to cause rapid increase in arterial pressure by stimulation of vasoconstrictor and cardioaccelerator functions of sympathetic nervous system + blockage of parasympathetic NS
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Rapid increase of arterial pressure by the nervous system:
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1. Constriction of arterioles (increases total peripheral resistance)
2. Constriction of veins and large vessels (Redistribution of blood from periphery to the heart --> increased preload--> increased force of contraction) 3. Direct effect on heart (increased HR and contractile force) |
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Norepinephrine:
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Secreted at the endings of the vasoconstrictor nerves and act on alpha adrenergic receptors of smooth mm.
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Activation of adrenal medulla:
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Sympathetic innervation in the same way as for vessels. Cause adrenal medulla to secrete epi and norepi into the blood stream.
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Emotional fainting- Vasovagal syncope:
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Disturbing thoughts in cerebral cortex from emotional disturbances--> vasodilatory center of anterior hypothalamus next to vagal centers of medulla---> vagus nerve to heart (slowing of HR) and through spinal nerves to the sympathetic vasodilator nerves of muscles (vasodilatation)
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Most important function of nervous system in regulation of circulation:
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Ability to cause rapid increase in arterial pressure by stimulation of vasoconstrictor and cardioaccelerator functions of sympathetic nervous system + blockage of parasympathetic NS
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Rapid increase of arterial pressure by the nervous system:
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1. Constriction of arterioles (increases total peripheral resistance)
2. Constriction of veins and large vessels (Redistribution of blood from periphery to the heart --> increased preload--> increased force of contraction) 3. Direct effect on heart (increased HR and contractile force) |
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General function of baroreceptor reflex.
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To adjust BP rapidly according dayly movements and provide effectively moment to moment regulation of BP, and avoid great variations in BP.
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Are the baroreceptors involved in long term regulation of BP:
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Most likely not, because they reset according to the mean pressure after a day or two. Increasing long term pressure from 100 to 160 mmHg leads to increased firing the first day, then it resets to that pressure and stops firing.
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Chemoreceptors and its control of arterial BP:
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Carotid bodies and aortic bodies with nutritive arteries supplying arterial blood for examination. Detect low O2, high CO2 and low pH and excite vasomotor center ---> increased arterial BP. Most important in BP below 80 mmHg
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Receptors in atria and pulmonary arteries and its regulation of BP:
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Sensitive to low pressure increase of volume after infusions. Activate reflex system and makes it more potent.
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The Bainbridge reflex:
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Stretch receptors of the atria elicit the Bainbridge reflex that transmits its afferent signal through the vagus n. to the medulla---> efferent through vagus and sympathetic nn. ==> increase HR and contractility (Prevents accumulation of blood in veins, atria and pulmonary circulation)
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CNS ischemic response:
(Most powerful of all activators of vasoconstrictor system) |
Vasomotor center responds directly to ischemia (by the failure to bring the accumulating CO2 away from the vasomotor center during low BP)---> Arterial pressure rises as high as heart can pump. Can increase BP 250 mmHg for as long as 10 min.
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Cushing reaction:
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Increased pressure of CSF that cuts of circulation activates the "CNS ischemic response" which increase BP higher than CSF pressure to ensure perfusion.
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