Transcript of BLOOD PRESSURE - PHYSIOLOGY ROBYN DANE AND KATY DAVIDSON.
- Slide 1
- BLOOD PRESSURE - PHYSIOLOGY ROBYN DANE AND KATY DAVIDSON
- Slide 2
- How do you calculate MAP? MAP = CO x SVR MAP = (2DBP + SBP)/3
How do you calculate pulse pressure? Difference between diastolic
and systolic pressures PP = SBP - DBP
- Slide 3
- What factors affect cardiac output? (2) Changes in Heart rate
Stroke volume What factors affect SVR? (2) Changes in Compliance
(of the aorta or arterioles) Arteriolar resistance
- Slide 4
- What is compliance? The rigidity of vessles What may affect
compliance? Age makes vessels more rigid Poiseuilles equation How
is resistance related to the size of the vessel? Resistance is
inversely related to the radius cubed.
- Slide 5
- Describe the neuronal controls of blood pressure Baroreceptor
reflex Stretch receptors located in the carotid sinus (CN IX) and
the aortic arch (CN X) Vasomotor and cardiac control centres in the
medulla Parasympathetic and sympathetic effectors to the heart and
blood vessels Fall in blood pressure sympathetic parasympathetic
Rise in blood pressure sympathetic parasympathetic
- Slide 6
- Chemoreceptor reflex Increase in blood acidity caused by
increase in CO2 and lactic acid levels. Detected by chemoreceptors
(in carotid arteries and aortic bodies) Nerve impulse sent to
cardiac centre in medulla oblongata Via CN X and CN IX Nerve
stimulation to SAN decreases vagal and increases sympathetic
impulses to increase heart rate. Results in an increased cardiac
output.
- Slide 7
- Local control of BP Blood pressure is also controlled locally
Firstly via stretch receptors to maintain flow - Increase in
transmural pressure should increase radius, causes muscle
contraction, which reduces radius and maintains flow Also by
release of vasoactive agents locally NO causes dilation and
endothelin 1 causes constriction Metabolites that result in
vasodilation include; H+ K+ adenosine CO 2 hypoxia (systemic
circulation only) This is to increase flow in areas of increased
metabolism to reduce the concentration of the metabolites in the
area.
- Slide 8
- Hormonal control of blood pressure Mainly involves which
hormones? Adrenalin and angiotensin II What affect does angiotensin
II have on blood pressure ? angiotensinogen angiotensin I
angiotensin II renin angiotensin converting enzyme from kidney acts
on vascular smooth muscle causing contraction
- Slide 9
- Starlings compensation Works initially to maintain stroke
volume in early heart failure, however, an optimal fiber length
exists. Excessively high filling pressures that over-stretch the
myocardial fibers, reduces the pumping capacity of the ventricles.
Therefore eventually reducing stroke volume later on in the
disease. The stretch of cardiac myocytes is directly related to the
force at which they contract
- Slide 10
- Performers will often use running as part of their training
programme. Both heart rate and stroke volume increase when running.
Use 'Starling's law of the heart' to explain how stroke volume
increases when running (4)
- Slide 11
- St arlings Law states that the greater venous return, the
greater stroke volume is. As venous return increases the walls of
the ventricles are stretched further. Results in a more powerful
contraction. Increases the amount of blood pumped around the body
during exercise.
- Slide 12
- Briefly explain the terms cardiac output and stroke volume and
the relationship between them Explain how it is possible for a
trained performer and an untrained performer to have the same
cardiac output for a given workload
- Slide 13
- Cardiac output is the volume of blood leaving left ventricle
per minute. Stroke volume is the volume of blood leaving left
ventricle per beat. Stroke volume x heart rate = cardiac output
Trained atheltes will have larger stroke volume. Can therefore
achieve same cardiac output with lower heart rate. Untrained
athlete compensates for smaller stroke volume by increasing heart
rate.
- Slide 14
- Calculate the MAP and PP for someone with a systolic BP of 120
and a diastolic BP of 90 MAP = 100 PP = 30 Calculate the cardiac
output for a patient with a HR of 100 and a stroke volume 70ml?
7000ml/minute or 7L/min MAP = (2DBP + SBP)/3 PP = SBP - DBP CO = SV
x HR
- Slide 15
- How do the following effect blood pressure Endothelin 1
Angiotensin II NO H+ vasoconstricts (increases BP) locally
vasodilates