Jan 16 - Hypertension Flashcards
Why is hypertension dangerous?
High blood pressure (and high cholesterol) contribute to the risk of ACS
What is arterial blood pressure?
The pressure exerted on the artery walls
What are the two 2 measures of blood pressure?
Systolic: the pressure in the arteries during systole (contraction)
Diastolic: the pressure in the arteries during diastole (rest/filling)
What is the mean arterial pressure (MAP)?
The average pressure throughout the cardiac cycle (one heartbeat)
How is the MAP measured?
2/3 diastolic blood pressure (time spent in diastole) + 1/3 systolic blood pressure (time spent in systole)
What is good blood pressure?
120/80; MAP = 93 (normal = 70 to 110)
What happens when MAP drops below 65?
It’s an emergency because the person’s organs (brain, liver, kidneys, etc.) are not being perfused with enough blood (adequately)
What is blood pressure (mathematically)?
Blood pressure = total peripheral resistance x cardiac output
What is the definition of peripheral resistance?
The “squeeze” of the blood vessels outside the heart resisting blood flow
What is the definition of cardiac output?
A measure of how much blood is flowing through the heart
What is cardiac output (mathematically)?
Heart rate x stroke volume
What is stroke volume?
The amount of blood ejected with each beat of the heart
What happens to blood pressure if you give the patient a drug that increases heart rate?
Blood pressure will increase
What happens to blood pressure if you give a drug that decreases total peripheral resistance?
It will decrease blood pressure
What is the difference between essential and secondary hypertension?
About 90% of the time, we don’t know the actual cause of hypertension (essential). Secondary hypertension is caused by a drug or another disease
What are the short-term mechanisms of blood pressure regulation?
Humoral, neuronal, hormonal and vascular. These mechanisms kick in right away (e.g. if you start bleeding)
What is a long-term (within a few days) mechanisms of blood pressure regulation?
Renal
What is a third mechanism of blood pressure regulation?
Electrolytes
What makes up the humoral mechanism of blood pressure regulation?
The renin-angiotensin-aldosterone system (RAAS)
What does the RAAS regulate?
It regulates sodium ions, potassium ions and blood volume
How does the RAAS monitor blood pressure?
The kidneys have juxtaglomerular cells. These have cells have baroreceptors, which can detect changes in pressure. Renin is an enzyme that is synthesized, stored, and released by the kidneys in response to an increase in sympathetic activity or a decrease in blood pressure, extracellular volume, or extracellular sodium concentration
What is renin? How does it work?
It’s an enzyme that converts angiotensinogen into angiotensin I
What are ACE? How do they work?
Angiotensin converting enzymes that convert angiotensin I into angiotensin II
What are the different parts of the body that angiotensin II affects?
The adrenal cortex, the kidneys, the intestines, the CNS, the PNS, vascular smooth muscles, and the heart. All of the different affects work to raise blood pressure
How does angiotensin II affect the heart?
It raises contractility, which increases cardiac output (increase in blood pressure)
How does angiotensin II affect vascular smooth muscle?
It causes vasoconstriction, which increases total peripheral resistance (increase in blood pressure)
How does angiotensin II affect the PNS?
It causes sympathetic discharge, which increases total peripheral resistance (increase in blood pressure)
How does angiotensin II affect the CNS?
It causes sympathetic discharge, which increases total peripheral resistance. It also causes the secretion of vasopressin, which increases blood volume, which increase total peripheral resistance (increase in blood pressure)
How does angiotensin II affect the kidneys and the intestines
It causes sodium and water reabsorption, which increases blood volume, which increase total peripheral resistance (increase in blood pressure)
How does angiotensin II affect the adrenal cortex?
It causes an increase in aldosterone synthesis, which causes sodium and water reabsorption, which increases blood volume, which increase total peripheral resistance (increase in blood pressure)
Why is the RAAS so important?
Because the drugs we use to lower blood pressure affect this system
How does neuronal regulation of blood pressure work?
Extrinsic reflexes, intrinsic reflexes and higher centre reflexes affect the autonomic nervous system (ANS), which is the cardiovascular centre of the brain