Hypertension Flashcards
Q: What is the response of the baroreceptor reflex to high blood pressure?
A:
- When the blood pressure is high, there is increased stretching of the vessel wall,
- which leads to the activation of mechanically gated sodium (Na+) channels in the sensory nerve endings of the baroreceptors.
- This results in an increased influx of Na+ and the generation of action potentials that travel via glossopharyngeal and vagus sensory fibers to the medulla, specifically the Nucleus Tractus Solitarius (NTS).
Q: What are the signals transmitted from the Nucleus Tractus Solitarius (NTS)?
A:
The NTS relays signals from the glossopharyngeal and vagus nerves to different centers in the medulla. These signals include:
- NTS to the cardiac inhibitory center in the medulla, leading to a decrease in heart rate.
- NTS to the cardioacceleratory center in the medulla, leading to a decrease in heart rate.
- NTS to the vasomotor center in the medulla, leading to a decrease in vasomotor tone and peripheral vascular resistance.
Q: How does preload affect stroke volume and cardiac output?
A:
- Increased preload, which refers to the volume of blood in the ventricles at the end of diastole,
- leads to an increased stroke volume (SV) and
- subsequently increased cardiac output (CO).
Q: What is the effect of afterload on stroke volume and cardiac output?
A:
- Increased afterload, which refers to the resistance the heart must overcome to eject blood,
- leads to a decreased stroke volume (SV) and
- subsequently decreased cardiac output (CO).
Q: Which center is responsible for inhibiting the parasympathetic nervous system and reducing heart rate in response to high blood pressure?
A: The Cardio-Inhibitory Center, located in the Dorsal Nucleus Vagus (part of the parasympathetic nervous system), is responsible for this response.
Q: What neurotransmitter is released by the parasympathetic nervous system to decrease heart rate?
A: Acetylcholine (ACh) is released by the parasympathetic nervous system to decrease heart rate.
Q: How does acetylcholine (ACh) decrease heart rate?
A:
- ACh binds to M2 receptors on nodal cells,
- leading to a decrease in heart rate through the inhibition of adenylate cyclase (AC),
- a decrease in cyclic adenosine monophosphate (cAMP) levels,
- and the activation of potassium (K+) channels, resulting in hyperpolarization.
Q: Which center is responsible for inhibiting the sympathetic nervous system and reducing norepinephrine release in response to high blood pressure?
A: The Cardio-Acceleratory Center, located in the sympathetic nervous system, is inhibited in response to high blood pressure.
Q: What is the effect of inhibiting the sympathetic nervous system on heart rate and contractility?
A: Inhibiting the sympathetic nervous system decreases norepinephrine release, leading to a decrease in heart rate and contractility.
Q: Which center is responsible for inhibiting the sympathetic nervous system and promoting vasodilation in response to low blood pressure?
A: The Vasomotor Center, located in the sympathetic nervous system, is inhibited in response to low blood pressure.
Q: How does inhibiting the sympathetic nervous system and promoting vasodilation affect blood pressure?
A: Inhibiting the sympathetic nervous system and promoting vasodilation result in a decrease in resistance, an increase in vessel diameter, and a subsequent decrease in blood pressure.
Q: What is the direct renal mechanism of blood pressure regulation?
A:
- The direct renal mechanism involves the kidneys altering blood volume independently of hormones.
- When blood volume or pressure increases, the filtration rate in the kidney tubules speeds up,
- leading to increased urine output and a decrease in blood volume and pressure.
Q: What is the renin-angiotensin-aldosterone system (RAAS)?
A:
- The RAAS is an indirect renal mechanism that regulates blood pressure.
- It involves the production of angiotensin II, a potent vasoconstrictor, through a series of steps involving renin, angiotensinogen, angiotensin I, and angiotensin-converting enzyme (ACE).
Q: What are the actions of angiotensin II?
A:
- stimulates vasoconstriction of systemic arterioles, leading to decreased vessel diameter,
- increased resistance, and increased blood pressure.
- It also stimulates the release of aldosterone, which promotes sodium and water retention, further increasing blood volume and pressure.
Q: Which hormone, stimulated by angiotensin II, increases sodium (Na+) and water reabsorption in the distal convoluted tubules of the kidney?
A: Aldosterone, produced by the Zona Glomerulosa of the adrenal cortex, increases Na+ and water reabsorption in the distal convoluted tubules of the kidney.
