Term
Modulation CONTROL of cardiac output
Intrinsic (autoregulation)
Extrinsic |
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Definition
* Intrinsic control
o Starling's Law of the Heart-
-degree of contraction is proportional to degree of previous stretch (proportional to venous return)
o is autoregulation, so the cardiac output is equal to the venous return
* Extrinsic control
o Hormonal--epinephrine (adrenaline), from the adrenal gland on top of the kidney, stimulates rate and stroke volume
o Nervous
#1 vertebrate heart is myogenic--the beat is initiated by the sinoatrial node (SA Node) in the right atrium--is a pacemaker composed of specialized muscle cells
#2 invertebrate heart is neurogenic--beat is initiated in the central nervous system
o even though the beat of the vertebrate heart is initiated by the heart muscle itself, the rate can be modulated by input from the autonomic nervous system |
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Term
rate of flow,and pressure of the flow
controlled by two separate |
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Definition
* Central--modulation of cardiac output
o about 5 liters/min at rest
30 liters/min during exercise.
* Peripheral resistance
o determined by vascular diameter-
-vasoconstriction vs. vasodilation
o perfusion of tissues can be controlled by constriction of vessels |
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Term
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Definition
Recognize
* hypercapnia (too much CO2) or hypoxia (not enough O2) stimulates the stimulatory center--increases cardiac output and perfusion of the lungs, maximizing gas exchange to offset the hypercapnia and/or hypoxia. Perfusion of tissues is also increased to increase oxygen uptake and CO2 excretion. |
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Term
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Definition
Recognize fall or rise in blood pressure
* increase in blood pressure stimulates the inhibitory center -leads to fall in cardiac output--which leads to fall in blood pressure
* fall in blood pressure stimulate the excititory and to increase cardiac out put |
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Term
| How are Veins and Arteris able to constrict |
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Definition
Nervous
Message sent from VASOMOTOR CENTER (in medulla) to vasocontrictor nerves (keep tubes tight)
This can be reversed when blood pressure signals the vasodilator center in the vasomotor center- this inhibits vasoconstrictor
(baroreceptors in the aorta and carotid.)
Nerve impulses from the VD center inhibit the VC center. |
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Term
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Definition
* Vasopressin (peptide)
pituitary gland
baroreceptors sense a fall
produces vasoconstriction
* Angiotensin (peptide)
produced in the blood
kidney senses a fall -
produces vasoconstriction
Endothelin
released from the endothelium
after vascular damage
produces vasoconstriction
prevent blood loss
* Nitric oxide
(a gas)
from the endothelium
produces vasodilation |
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Term
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Definition
(fatty acid derivatives)
released from endothelial cells produces
vasoconstriction and vasodilation. |
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Term
| Atrial natriuretic peptide (ANP; peptide ) |
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Definition
*released from the heart
increases venous return
*Released from endothelium (excess stretching) and relaxes vascular smooth muscle
VASODILATION |
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Term
Cardiac center in the medulla
* is controlled by |
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Definition
| sensory input from the aorta and the carotid body |
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