Heurohumoral Control of the Heart and Circulation
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What three important things does the Parasympathetic system do?
- 1.) conduction slows
- 2.) HR slows
- 3.) contraction decreases
What three important things does the Sympathetic system do?
- 1.) conduction increases
- 2.) HR increases
- 3.) contraction increases
When talking about cv physiology what system is more important the parasympathetic or sympathetic?
the sympathetic system
What do the sympathetic neural fibers do?
- they control the TPR by releasing norepinephrine which increases the tone of the arterioles
- also they have a continual or tonic firing activity which produce tone
- (firing rate increased=arterioles will constrict=blood flow decreased
- which decreases the diameter
- which decreases the flow of blood
What does the Innervation of the Vascular System?
- The sympathetic innervation will constrict both resistance (arterioles) and capacitance (veins) vessels.
- This than increases systemic vascular resistance and arterial blood pressure.
What does the parasympathetic innervation of the Vascular System do?
It regulates blood flow within specific organs.
- (Not the blood vessels going in and out of the organs)
- It doesn't play a huge role in regulation of SVR & arterial blood pressure.
What is the activity between the sympathetic and parasympathetic systems?
When one is active, the other one is being downplayed in the background.
How is the blood pressure maintained?
One thing that triggers the sympathetic system is the arterial baroreceptors.
Increasing the firing rate will lower the blood pressure.
Where are arterial baroreceptors located?
Found in the walls of the aortic arch and in the carotid sinus or carotid bulb.
Main concept to remember when discussing baroreceptors?
They regulated short-term arterial pressure.
Called the arterial baroreceptor reflex.
The arterial baroreceptors act to regulate arterial pressure in a "negative feedback".
If the mean arterial pressure drops what happens to the baroreceptors?
the firing of the baroreceptors will decrease
If the mean arterial pressure increases what happens to the baroreceptors?
the firing of the baroreceptors will increase
What is an non-medical example of negative feedback?
Compared to a thermostat controlling air-conditioning in a house.
What is the carotid sinus massage?
- This reflex can be activated by rubbing the neck over the carotid sinus.
- This increases the firing rate, which decreases the sympathetic activity and increases the parasynpathetic activity.
What are other receptors that affect the mean arterial pressure (5)?
- 1.) chemoreceptors reflexes
- 2.) receptors in exercising skeletal muscle
- 3.) dive reflex responses associated with emotion: flight or fight
- 4.) responses to pain
- 5.) temperature regulation reflexes
What is the long term arterial pressure is regulated by what is known as?
- fluid volume mechanism
- angiotensin-aldosterone system
An disturbance that causes an increase in arterial pressure causes what 5 things to follow?
- increase in urine output
- decrease in fluid volume
- decrease in blood volume
- decrease in cardiac output
- decrease in arterial pressure
An disturbance that causes an decrease in arterial pressure causes what 5 things to follow?
- decrease in urine output
- increase in fluid volume
- increase in blood volume
- increase in cardiac output
- increase arterial pressure
The steps to where angiotensin II comes from.
- 1.) Renin is an enzyme produced by the kidney.
- 2.) It acts upon angiotensinogen which is released from the liver.
- 3.) It undergoes some changes and becomes angiotensin I.
- 4.) Vascular endothelium of the lungs has an enzyme call ACE or angiotensin-converting enzyme.
- 5.)This interacts with angiotensin I and makes angiotensin II.
- 6.) Constricts resistance vessels-Arterioles-increasing TPR and arterial pressure.
- 7.) Facilitates norepinephrine release from the sympathetic nerve endings and enhances sympathetic adrenergic affects.
- 8.)Acts upon the adrenal cortex to release aldosterone which acts upon the kidneys to increase sodium and fluid retention, which in turn increases blood volume.
- 9.) It stimulates teh release of vasopressin from the posterior pituitary which acts upon the kidneys to increase fluid retention and blood volume.
- 10.) It stimulates thirst centers within the brain which lead to increase in blood volume.
- 11.) It stimulates cardiac and vascular hypertrophy.
What does hypertrophy mean?
is the increase in the volume in a tissue or organ due to the enlargement of its component cells.
What are the three endothelial factors?
- 1. Nitric oxide
- 2. Endothelin-1
- 3. Prostacycline
What are Nitric oxide and Prostacycline?
What happens if you block nitric oxide formation?
It will lead to an increase in vascular tone.
What is the most important in terms of regulating blood flow under normal physiologic conditions?
What does Endothelin-1 do?
What is an important function of vasoconstrictor mechanism?
maintaining systemic vascular resistance and arterial pressure
What is an important function of vasodilator mechanisms?
regulate blood flow within the organs
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