Control of Arterial Blood Pressure Flashcards
what is blood pressure?
the outwards hydrostatic pressure exerted by blood on the blood vessel walls
what is systolic blood pressure?
the pressure exerted by blood when the heart contracts
what is diastolic blood pressure?
the pressure exerted by blood when the heart relaxes
what value is considered to be hypertension?
clinic BP over 140/90 AND daytime average of over 135/85
what is pulse pressure?
the difference between systolic and diastolic blood pressures
what is the normal range for pulse pressure?
between 30 and 50 mmHg
what is the mean arterial blood pressure (MAP)?
the average arterial blood pressure during a single cardiac cycle
how is MAP calculated?
MAP = (2diastolic + systolic)/3
OR
diastolic + 1/3pulse pressure
what is the normal range for MAP?
70-105mmHg
what is MAP of at least 60mmHg needed for?
to perfuse the coronary arteries, brain and kidneys
what is MAP equal to?
cardiac output (CO) x systemic vascular resistance (SVR)
what is the cardiac output?
the volume of blood pumped by each ventricle per minute
how can cardiac output be calculated?
CO = stroke volume (SV) x heart rate (HR)
what is stroke volume?
the volume of blood pumped by each ventricle of the heart per heart beat
what is systemic vascular resistance?
the sum of the resistance of all the vasculature in the systemic circulation
which vessel is the major resistance vessel?
the arterioles
what is the baroreceptor reflex important for?
the moment-moment regulation of blood pressure, including prevention of postural changes
what causes postural hypotension?
failure of the baroreceptor response to gravitational shifts in blood when standing up
what is another name for postural hypotension?
orthostatic hypotension
what indicates postural hypotension?
a drop in SBP of at least 20mmHg when standing with/without symptoms
OR
a drop in DBP of at least 10mmHg with symptoms
what is total body fluid?
intracellular fluid + extracellular fluid (ECF)
what is ECFV?
extracellular fluid volume
what are the two main factors that affect ECFV?
water excess/deficit
sodium excess/deficit
name three hormones/hormone systems that regulate ECFV
RAAS natriuretic peptides (NPs) antidiuretic hormone (ADH)
what does altering ECFV affect?
blood volume and blood pressure
what does RAAS stand for?
the renin angiotensin aldosterone system
what are the three main components of RAAS?
renin
angiotensin
aldosterone
where is renin released from?
the kidneys
what does renin do?
stimulates formation of angiotensin I from angiotensinogen in the blood
what produces angiotensinogen?
the liver
what happens to angiotensin I?
converted to angiotensin II by ACE
what is ACE and where is it made?
angiotensin converting enzyme
the pulmonary vascular endothelium
what does angiotensin II do?
stimulates release of aldosterone
causes vasoconstriction
where is aldosterone released from?
the adrenal cortex
what is aldosterone?
a steroid hormone
what does aldosterone do?
acts on the kidneys to increase sodium and water retention
what is the rate limiting step in RAAS?
renin secretion
where is renin secreted from in the kidneys and what cells here release it?
the juxtaglomerular apparatus
granular cells
what are natriuretic peptides (NPs)?
peptide hormones synthesised by the brain and heart
when are NPs released?
in response to cardiac distension or neurohormonal stimuli
what do NPs cause?
excretion of salt and water in the kidneys
decreases BP
what is renin released in response to?
decreased blood pressure
RAAS aims to increase it
what are the two main types of NPs released by the heart?
atrial NP
brain type NP
what is another name for ADH?
vasopressin
what is ADH?
a peptide hormone derived from a prehormone precursor, synthesised by the hypothalamus
what stimulates secretion of ADH?
reduced ECVF
increased ECF osmolality
what does ADH act on and what does it do?
the kidney tubules
increases reabsorption of water
what effect does ADH have on blood vessels?
causes vasoconstriction
