Baroreceptor reflex physiology short term regulation of blood pressure | CVS Physiology | MBBS

Summary

The video explains the regulation of blood pressure through the baroreflex mechanism. It discusses the role of baroreceptors in the carotid and aortic sinuses, which detect blood pressure changes. When blood pressure increases, the parasympathetic system is activated, decreasing heart rate and cardiac output, while the sympathetic system is inhibited, reducing peripheral resistance and diastolic pressure. The video emphasizes the importance of these systems in controlling blood pressure, with a focus on the interactions between the sympathetic and parasympathetic systems. It concludes by noting that a drop in blood pressure leads to opposite effects, activating the sympathetic system and reducing parasympathetic activity.

Takeaways

• 😀 Baroreflex is a key short-term mechanism in blood pressure regulation, involving baroreceptors in the carotid and aortic sinuses.
• 😀 The carotid sinus is located above the bifurcation of the common carotid artery, while the aortic sinus is located in the aortic arch.
• 😀 Baroreceptors are stimulated when the mean arterial pressure exceeds 70 mmHg and can operate up to 200 mmHg.
• 😀 The carotid sinus is more sensitive, working up to 30 mmHg lower than the aortic sinus.
• 😀 Information from baroreceptors is sent to the brain via the glossopharyngeal nerve (carotid sinus) and vagus nerve (aortic sinus).
• 😀 The brain's medulla and nucleus tractus solitarius play central roles in regulating blood pressure through parasympathetic and sympathetic pathways.
• 😀 Stimulation of the CVLM region of the medulla leads to parasympathetic activation and sympathetic inhibition, lowering blood pressure.
• 😀 Parasympathetic activation slows heart rate via the SA and AV nodes, resulting in lower cardiac output and systolic blood pressure.
• 😀 Sympathetic activation increases heart rate, contractility, arteriolar constriction, and venous return, leading to higher blood pressure.
• 😀 The opposing effects of parasympathetic and sympathetic systems allow the body to regulate both systolic and diastolic blood pressure in response to changes in blood pressure.
• 😀 If blood pressure decreases, baroreceptor activity decreases, which reduces parasympathetic activity and increases sympathetic activation, reversing the initial effects.

Q & A

What are the two primary baroreceptors involved in the regulation of blood pressure?

The two primary baroreceptors involved in the regulation of blood pressure are the carotid sinus and the aortic sinus.

Where is the carotid sinus located?

The carotid sinus is located just above the bifurcation of the common carotid artery, in the internal carotid artery.

What is the range of blood pressure in which baroreceptors are effectively stimulated?

Baroreceptors are stimulated when the mean arterial pressure is greater than 70mmHg and up to 200mmHg.

How do the carotid sinus and aortic sinus differ in terms of their operational range?

The aortic sinus works at a range that is 30mmHg higher than that of the carotid sinus, meaning the aortic sinus responds to higher blood pressures.

Which afferent nerves carry information from the carotid sinus and aortic sinus to the brain?

The glossopharyngeal nerve carries information from the carotid sinus, while the vagus nerve carries information from the aortic sinus.

What is the role of the nucleus tractus solitarius (NTS) in blood pressure regulation?

The nucleus tractus solitarius (NTS) receives information from the baroreceptors and is stimulated when blood pressure increases. It then plays a key role in regulating the autonomic response to adjust blood pressure.

How does the caudal ventral lateral medulla (CVLM) affect the parasympathetic and sympathetic nervous systems?

The CVLM stimulates the parasympathetic nervous system by activating the nucleus ambiguous and the dorsal motor nucleus of the vagus, while inhibiting the rostral ventral lateral medulla (RVLM) that controls the sympathetic system.

What is the effect of parasympathetic stimulation on the cardiovascular system during high blood pressure?

Parasympathetic stimulation mainly decreases heart rate, leading to a decrease in cardiac output and a reduction in systolic blood pressure.

What effects does sympathetic stimulation have on the cardiovascular system?

Sympathetic stimulation increases heart rate and the force of contraction, causes arteriole constriction, which raises peripheral resistance and diastolic blood pressure, and leads to venoconstriction, which increases venous return and further boosts heart contraction.

What happens when blood pressure decreases, and how does the baroreflex respond?

When blood pressure decreases, baroreceptor stimulation reduces, leading to less afferent activity and a decrease in NTS stimulation. As a result, the sympathetic system becomes more active, and the parasympathetic system's activity decreases, causing the opposite effects of those seen with high blood pressure.