Central factors of cardiovascular regulation Flashcards
What is the main task of Regulation of circulation?
- substance transport to and from the tissues should be insured
- prevention of the collapse of circulation by providing sufficient blood supply to the organs according to the metabolic needs.
What types of Regulation of circulation do we have?
- Local (=intrinsic)
- short-term/long-term
- regulated by fast, local, auto-regulative processes - Central (=extrinsic)
- short-term/long-term
- coordinating redistribution
Function of the Local regulation?
- intensity of perfusion (blood flow) is determined mainly by the oxygen and nutrient demand of the organ
Function of the Central regulation?
- Maintaining the optimal working condition of the organs in the long run needs central (extrinsic) regulations provided by CNS/hormones, adjusting the contraction status of arteries and veins (coordinating redistribution?
Types of Extrinsic (neural/hormonal) regulation of circulation:
2/a: Extrinsic short-term regulation
- Sympathetic effects
- vasoconstrictor and local NO related vasodilator tone: the cardio-vasomotor center; thoracolumbal efferentation - Parasympathetic effects
- Humoral effects
- Vessel related reflexes
2/b: Extrinsic long-term regulation
What is the most important tas of the Extrinsic (neural/hormonal regulation)?
Is the compensation of differences in organ perfusion through redistribution.
- in other words: the extrinsic neural and hormonal mechanisms oversee the distribution of blood among organs.
- Vessels are under the balanced influenced of:
Small intensity sympathetic-vasoconstrictor tone and vasodilating tone maintained by locally produced NO.
The end result is: permanent, modest vasoconstriction at rest.
Factors of Neural regulation?
- The cardio-vasomotor Centers are located in the medulla oblungata. It is close to the respiratory center
- Pressor area (craniolateral part)
- Depressor area (caudomedial part)
- cardioaccelerator area (in the middle)
What is the effect/function of the Pressor center?
It has spontaneous activity, and is meadiated by the thoracolumbar sympathetic preganglionic neurons:
- the cardiac output increases, the peripheral resistance (TPR) increases.
What is the Sympathetic effect of the Depressor area?
It has no spontaneous activity.
Vasodilation is achieved by depressing the activity of the pressor area via inhibitory interneurons.
- this results n vasodilation via the decrease of the sympathetic vasoconstrictor tone.
-The negative effect of this center on the heart is mediated by vagal fibers.
Beside this: hypothalic, cortical and other CNS influences may modulate the activity of the depressor area.
Blood pressure will decrease
What is the Parasympathetic effect og the Depressor area?
- Vasodilation happens due to a decrease of symp. vasoconstrictor tone, rather than an active parasympathetic effect.
- Active parasympathetic effect are only found in penis, uterus, pancreas etc.
- Indirect vasodilation in selected organs may occur (in salivary gland etc)
When is appropriate Redistribution of the Circulating blood volume possible in Arteries?
- Arteries are under the influence of sympathetic postganglionic fibers (transmitter: norepinephrine). the actual response is also determined by the number and quality of the Catecholamine receptors in the given vessel.
- In the arteriles and metarteriols of the skeletal muscle dilation is the response
- in the splanchnic area vasoconstriction is seen
= this makes redistibution possible
When is appropriate Redistribution of the Circulating blood volume possible in Veins?
- Veins are also under the control of the sympathetic postganglionic (noradrenergic) effects.
- the high number of alpha-receptors found here results in an effective contraction as a response to sympathetic stimmulation.
- Result: blood is forwarded from the capacitance system into the resistance system.
Sympathetic predominace causes?
Vasoconstriction; postganglionic discharge of nor-epinephrine, alpha receptor stimulation.
Vasodilation is a result of?
the decrease of the sympathetic predominance rathr than the increase of the parasympathetic influence.
What causes increased perfusion of organs?
- Stress mobilizes the adrenal medulla and the consequent discharge of epinephrine dilates the vessels of the skeletal muscle causes increased perfusion in this organ.
- The general dilation in the skeletal muscle does not depress the blood pressure however, since the epinephrine increased the performance of the heart, leading ti increased Cardiac Otuput.
