Section 7 Flashcards
Among systolic pressure, diastolic pressure, pulse pressure, and mean arterial pressure, which is considered the most important driving force to keep blood circulating throughout the body?
Mean arterial pressure (MAP) is the most crucial, as it is the value regulated by the body to ensure blood circulation.
How is mean arterial pressure (MAP) constantly monitored in the circulatory system?
Baroreceptors monitor mean arterial pressure, allowing the body to make both short-term and long-term adjustments to maintain it.
What are the main mechanisms for short-term and long-term adjustments in mean arterial pressure?
Short-term adjustments involve the autonomic nervous system, enabling beat-to-beat changes in cardiac output and total peripheral resistance. Long-term adjustments focus on regulating blood volume through kidney function and salt and water balance.
What activates the autonomic-mediated baroreceptor reflex?
Anything that happens to change mean arterial pressure activates the autonomic-mediated baroreceptor reflex.
Where are the baroreceptors located, and why are these locations important?
Baroreceptors are found in the carotid sinus and the aortic arch. The carotid sinus monitors mean arterial pressure of blood being delivered to the brain, while the aortic arch monitors mean arterial pressure in the systemic circulation. These locations are crucial for monitoring and responding to changes in blood pressure.
How do baroreceptors respond to changes in arterial pressure?
Baroreceptors change their firing rate in response to alterations in arterial pressure. An increased pressure leads to an increased firing rate, while a decreased pressure results in a decreased firing rate.
Explain the firing rate of baroreceptors in different scenarios of arterial pressure.
Baroreceptors exhibit a stable firing rate during normal, stable mean arterial pressure. An increased mean arterial pressure leads to an increased firing rate, while a decreased mean arterial pressure results in a decreased firing rate.
Where is the cardiovascular control centre located?
The cardiovascular control centre is situated in the medulla within the brain stem.
How do the sympathetic and parasympathetic pathways mediate changes in blood pressure?
The parasympathetic nervous system, by releasing acetylcholine at the SA node, decreases heart rate, cardiac output, and blood pressure.
Conversely, the sympathetic nervous system increases heart rate, contractile strength of the heart, and vasoconstriction, leading to an increase in stroke volume, cardiac output, and ultimately blood pressure.
What are the other reflexes and responses that regulate the cardiovascular system besides the baroreceptor reflex?
Left Atrial Volume Receptors and Hypothalamic Osmoreceptors: Important for long-term control of mean arterial pressure, involved in water and salt balance.
Chemoreceptors in the Carotid and Aortic Arteries: Sensitive to low oxygen or high acid levels in the blood; their activity projects to both the respiratory and cardiovascular control centers to increase blood pressure.
Emotions: Certain responses initiated through cerebral cortex-hypothalamic pathways, like the generalized fight-or-flight response and localized cutaneous responses associated with blushing.
Hypothalamic Control of Skin Arterioles for Temperature Regulation: Can override the cardiovascular control center; skin arterioles dilate to reduce body temperature if body temperature is above normal despite a decrease in blood pressure.
Vasoactive Substances: Various substances released in response to local changes in the cardiovascular system, including nitric oxide and endothelin produced and released by endothelial cells independently of autonomic input.
How do chemoreceptors in the carotid and aortic arteries contribute to the regulation of the cardiovascular system?
Chemoreceptors in the carotid and aortic arteries, in addition to monitoring pressure, are sensitive to low oxygen or high acid levels in the blood. Their activity projects to both the respiratory and cardiovascular control centers, leading to an increase in ventilation and blood pressure.
How is hypertension defined, and what is the recommended approach for diagnosing it?
Hypertension is defined by a chronic elevation of blood pressure to greater than 140/90 mmHg. To diagnose hypertension, blood pressure should be measured on three separate visits, with each measurement taken at least two weeks apart. This approach helps account for transient elevations due to factors like exercise, stress, or White Coat syndrome.
What is White Coat syndrome, and why is it important to consider when diagnosing hypertension?
White Coat syndrome is a phenomenon in which patients exhibit a blood pressure level above the normal range in a clinical setting, though they don’t exhibit it in other settings. It’s crucial to consider when diagnosing hypertension because blood pressure readings can be transiently elevated during a medical visit due to factors like anxiety or stress, leading to a potential misdiagnosis if not accounted for through multiple measurements.
What is the estimated prevalence of hypertension in the Canadian adult population, and why is hypertension often clinically silent?
It is estimated that 35-50% of the Canadian adult population is affected by hypertension, and it often goes undiagnosed because it is clinically silent, especially in those with mild to moderate hypertension. There are usually no symptoms, and common signs like fatigue, blurred vision, or headaches can be easily attributed to stress.
What are the potential consequences of untreated hypertension, and how does it impact lifespan?
Untreated hypertension can significantly impact lifespan, shortening it by 10-20 years. Even with treatment, more than 50% of individuals with hypertension may develop end-organ damage. This emphasizes the importance of timely diagnosis and management to mitigate the long-term effects of hypertension.
