79. Physiology - Control of arterial blood pressure 1 Flashcards
what is blood pressure
“the outwards (hydrostatic) pressure exerted by the blood on blood vessel walls”
what is ‘systemic systolic arterial blood pressure’
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
systolic blood pressure should not reach/exceed what?
140 mm Hg
what is Diastolic Arterial Blood Pressure
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
diastolic blood pressure should not reach/exceed…?
90 mm Hg (under resting conditions)
what is the term for very high blood pressure
hypertension
define hypertension
Clinic blood pressure of 140/90 mmHg or higher and day time average of 135/85 mmHg or higher
what is pulse pressure
the difference between systolic and diastolic blood pressure
what is the pulse pressure is systolic BP is 120 and diastolic is 80
40 mm Hg
what is the normal rage for pulse pressure
30 and 50
can Laminar Flow in Normal Arteries be heard
no
If external pressure (e.g. cuff pressure) exceeding the systolic blood pressure is applied to an artery. What happens? Can you hear anything
The flow in that artery would be blocked and no sound is heard through a stethoscope
if the external pressure is kept between systolic and diastolic pressure the flow becomes…. and can you hear anything
turbulent. yes, you can hear.
what equipment is used for blood pressure
sphygmomanometer and stethoscope
when is diastolic pressure recorded
fifth Korotkoff sound (point when sound disappears)
when do you record systolic BP
1st Korotkoff sound (first appearance of sound)
a pressure gradient between ……and ….. …… drives blood around the systemic system
aorta and right atrium
how would you calculate the pressure gradient
Mean Arterial Pressure (MAP) – Central Venous (right atrial) Pressure (CVP)
what is mean arterial blood pressure (MAP)
the average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart
how can MAP be estimated
MAP = (2x diastolic pressure) + systolic pressure
divided by 3
so if systolic BP is 120 and diastolic BP is 80. what is MAP?
93.3 mmHg
what is the normal range of MAP
70 -105 mmHg
MAP of at least … mm Hg is needed to perfuse the coronary arteries, brain, and kidney
60
what happens if MAP is to high
puts strain on vital organs
what is cardiac output
The volume of blood pumped by each ventricle of the heart per minute
what is stroke volume
Stroke Volume is the volume of blood pumped by each ventricle of the heart per heart beat
what is systemic vascular resistance
The sum of resistance of all vasculature in the systemic circulation
which vessels are the major resistance vessels
arterioles
what is the short term regulation of mean arterial blood pressure
the baroreceptor reflex
what kind of feedback does baroreceptor reflex use
negative
where are the baroreceptors
Carotid Baroreceptor - carotid artery- via IXth CN
Aortic Baroreceptors - aorta-via Xth CN
where do baroreceptors signal
send signals through the Vagus and glossopharyngeal nervs to the medulla
The baroreceptor reflex helps maintain stable blood pressure, especially during sudden changes like when?
Postural changes aka standign up quickly
when you stand up quickly, what happens to your venous return and MAP
- Gravity causes blood to pool in your legs which reduces venous return to the heart
- MAP briefly drops
when you stand up quickly, your MAP drops. what happens next?
the drop in MAP reduces the firing rate of baroreceptors
what are the autonomic adjustments when you stand up quickly and decrease MAP.
- Decrease Vagal tone increasing HR and SV (Vagal tone refers to the activity of the vagus nerve, which is a key part of the parasympathetic nervous system)
- Increased sympathetic tone - sympathetic tone increases causing
Inc. SVR (arterioles constrict)
Inc Venous return (veins constrict)
failure of Baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position is called?
Postural Hypertension
risk factors of postural hypertension are…?
Age, medication, certain diseases, prolonged bed rest, reduced intravascular volume
Baroreceptors ONLY Respond to ‘…………’ Changes in Blood Pressure
Acute
baroreceptor firing decreases if HBP is …..?
sustained
Control of MAP in the longer-term is mainly by control of…?
Blood Volume
