Control of Arterial Blood Pressure Flashcards
What is blood pressure?
outwards pressure exerted by blood on the blood vessel wall
What is systolic blood pressure? What is its normal values?
pressure exerted on the walls of the aorta and systemic arteries when the heart contracts
110-130mmHg
What is diastolic blood pressure? What is its normal values?
pressure exerted on the walls of the aorta and systemic arteries when the heart relaxes
60mmHg - 90mmHg
What is mean arterial blood pressure? What is its normal values?
average arterial blood pressure during a single cardiac cycle
70-105mmHg
How do you calculate MAP?
MAP = DBP + 1/3 Pulse Pressure MAP = [(2 x diastolic pressure) + systolic pressure] /3
Normal pulse pressure?
30-50mmHg
What are the Kortotkoff Sounds?
Sounds heard when measuring BP.
1. heart at peak systolic pressure
2 & 3. intermittent sounds are heard as blood pressure exceeds cuff pressure
4. last sound heard at minimum diastolic pressure
5. no sounds heard thereafter due to laminar flow
Consequences of MAP being too high?
damage blood vessels and places strain on the heart
Consequences of MAP being too low?
cannot perfuse internal organs
What does MAP=??
MAP = CO x SVR
What are the main resistance vessels?
Arterioles
What causes short term regulation of MAP?
Baroreceptor Reflex
What are the sensors, control centre and effectors of the Baroreceptor Reflex?
Sensors: baroreceptor
Control Centre: medulla
Effectors: blood vessels and heart
What is Postural Hypotension?
Disease resulting in the failure of baroreceptor respose to gravitational shifts in blood when moving from horizontal to vertical
What happens when a person goes from horizontal to vertical?
- decreased venous return to the heart
- decreased MAP
- decreased firing rate of baroreceptors
- decreased vagal tone
- increased sympathetic tone
- increased heart rate and stroke volume
- increased sympathetic constrictor tone
- increased systemic vascular resistance
The increases sympathetic constrictor tone to the veins increases venous return to the heart and stroke volume, this results in a rapid correction of MAP so an increased heart rate, stroke volume and systemic vascular resistance.
What is the long term regulation of MAP?
ECF Volume
What is ECF volume made up of?
Plasma volume and Interstitial Fluid Volume
What factors affect ECFV?
Na+ and water levels
What regulate the ECFV and how?
Hormones by regulating the water and salt balance in our bodies
Which hormones regulates the ECFV?
Renin-Angiotensin-Aldosterone-System RAAS, Natriuretic Peptides and Antiduiretic hormones
What is the rate limiting step for RAAS?
Renin Secretion
What does Renin do?
released from the kidneys and then stimulates the formation of angiotensin 1 from angiotensinogen
What does angiotensin 1 do?
converted to angiotensin 2 by angiotensin converting enzyme (ACE)
What does angiotensin 2 do?
stimulates the release of aldosterone from the adrenal cortex and causes systemic vasoconstriction
