Neural Regulation of Blood Pressure (Nursing)

00:00 The two main neural mechanisms that are going to control our peripheral resistance are going to be when the mean arterial pressure is maintained by altering the diameter of our blood vessels.

00:13 This is going to alter the resistance.

00:16 So for example, if your blood volume were to drop, all of your vessels would constrict in order to increase resistance.

00:27 This can also alter the blood distribution to our organs in response to specific demands.

00:33 For example, during exercise or during our fight or flight response, we can alter where our blood goes and move it away from our digestive tract and toward our skeletal muscles.

00:47 Neural controls are going to operate by way of the reflex arcs.

00:51 They're going to involve the cardiovascular center of the medulla oblongata, baroreceptors, chemoreceptors, and our higher brain centers.

01:02 Starting with our cardiovascular center, this is composed of clusters of sympathetic neurons in the medulla oblongata.

01:12 The cardioinhibitory center and the cardioacceleratory center make up these cardiac centers.

01:19 We also had the vasomotor center, which is going to send steady impulses by way of the sympathetic efference called vasomotor fibers to the blood vessels.

01:31 This causes a continuous moderate constriction of our blood vessels known as our vasomotor tone.

01:39 The vasomotor center is going to receive inputs from our baroreceptors, our chemoreceptors, as well as our higher brain centers.

01:49 When it comes to the baroreceptors these are going to be located in the carotid sinuses, the aortic arch, and the walls of the large arteries of the neck and the thorax.

02:01 If our main arterial pressure is high, then the increased blood pressure will stimulate these baroreceptors to increase the input to the vasomotor center.

02:13 This is inhibits the vasomotor and cardioacceleratory center and stimulates the cardioinhibitory center.

02:23 This results in a decrease in our blood pressure.

02:27 The resulting decrease in blood pressure is then going to be due to two mechanisms.

02:33 First, vasodilation.

02:35 Where we decrease the output from the vasomotor center, which is going to cause dilation of our vessels.

02:44 Arteriolar vasodilation is going to reduce the peripheral resistance, which is then going to reduce the mean arterial pressure.

02:53 Venodilation is going to shift the blood to our venous reservoirs which then decreases the amount of venous return and then cardiac output.

03:05 The second factor that can lead to a decrease in blood pressure is decreased cardiac output.

03:11 Impulses to the cardiac centers are going to inhibit the sympathetic activity and stimulate parasympathetic activity.

03:20 This reduces the heart rate and the contractility.

03:23 So cardiac output decreases are going to cause a decrease in the mean arterial pressure.

03:32 So if our main arterial pressure is low, then reflex vasoconstriction is going to be initiated, which is going to increase our cardiac output and blood pressure.

03:44 And this includes the carotid sinus reflex, where baroreceptors are going to monitor the blood pressure to ensure that there is enough blood going to our brain.

03:56 We also have the aortic reflex which maintains our blood pressure in the systemic circuit.

04:03 Baroreceptors are ineffective if altered blood pressure is sustained.

04:09 And they become adapted by hypertension so that they are not triggered by elevated blood pressure levels.

04:16 if you have a sustained hypertension.

04:21 The aortic arch and the large arteries of the neck are going to detect increases in carbon dioxide or drops in our pH or oxygen levels.

04:33 These are going to cause an increased blood pressure by signaling the cardioacceleratory centers to increase cardiac output, and by signaling the vasomotor center to increase vasoconstriction.

04:49 Reflexes that regulate our blood pressure are going to be found in the medulla.

04:54 But also the hypothalamus and the cerebral cortex can modify arterial pressure via relays to the medulla.

05:03 For example, the hypothalamus increases the blood pressure during stress.

05:10 And the hypothalamus mediates redistribution of blood flow during exercise or changes in our body temperature.