Download L06 - ISpatula

Physiology (L06)
Dr. Faisal :)
Slide#3:
-Mean arterial pressure is not systolic pressure and it is not the diastolic
pressure (because the diastole and systole are not equally in time, if we
suppose that the cardiac cycle is 0.8 second: heart rate=75beat/minute, 0.3
second is systole and 0.5 second is diastole).
-If you want to change the MAP, you change either the CO or the TPR or you
change both.
Slide#4:
-If you decrease the radius by half, the resistance will increase 16 times, and
same if you increase the radius by double, the resistance decrease 16 times.
-If we want to increase or decrease the flow of blood, we cause either
vasodilatation or vasoconstriction. Viscosity cannot be changed in order to
control the flow, because it depends on the number of RBCs found in blood.
Slide#10:
I remember that dr. Iyad said that you will have a question in the exam in how to
pronounce (sphygmomanometer) :p
Anyway;
-Such sphygmomanometer had disappeared because it contains mercury and
mercury is the most toxic and it would be fatal if the tool had exploded.
-We use the Cuff to increase pressure, if the pressure became above the
systolic pressure, there will be no flow, and thus no sounds, and we decrease
the pressure ‫ شوي‬،‫ شوي‬, then we have flow and we hear a sound (the flow here
happened because the systolic pressure became higher than the cuff pressure)
, such flow is called: turbulent flow, which gives sounds (S1) and (S2).
Slide#12: back to slide#136.
-We change cardiac output by changing heart rate or changing stroke volume
or by changing both.
Slide#13:
-The systolic blood pressure normally ranges from 90-140, and diastolic blood
pressure between 60-90.
-MAP is closer to diastolic pressure because in equation its 2/3 of diastolic.
(MAP=2/3diastolic + 1/3systolic)
-When we talk about hypertension, we talk about the MAP because it is the
pressure which pushes the blood through the circulation not the systolic
neither the diastolic. But the diastolic pressure affects the MAP more than the
systolic and thus it is more dangerous if it is higher or lower than the normal.
Slide#14:
-The vessels are only supplied by the sympathetic nervous system, they are not
supplied by the parasympathetic.
-Capillaries are not even supplied by the sympathetic nervous system because
they do not have smooth muscle.
-Sympathetic tones go to veins and arteries normally without any stimulations,
these tones give us vascular tone, this vascular tone may increase and cause a
vasoconstriction, or decrease and cause a vasodilatation. (vasoconstriction by
sympathetic stimulation, vasodilatation by sympathetic inhibition – not by
parasympathetic, because it only acts on the heart.)
- Parasympathetic stimulation increases heart rate and contractility
(chronotropic “on the pace of heart rate” and inotropic “on contractility” ) and if
contractility increases, stroke volume increases,
**Contractility means, when the end diastolic volume is fixed, an increase in
contractility means an increase in the stroke volume. But how? How can I
increase the stroke volume if the end diastolic volume is fixed? –I increase the
end systolic volume if I want to decrease the stroke volume. Otherwise, if you
increase the end diastolic volume, the stroke volume will increase, how? By
Frank-Starling law. Which tells you that if you increase end diastolic volume,
stroke volume will be increased, but within certain limits, but after this limit, the
inversion will happen : increasing end diastolic volume will cause a decrease in
stroke volume.
Slide#15:
-Short term regulation is usually nervous (rapidly); long term regulation is
usually hormonal.
-Baroreceptors are located in carotid sinus and in aortic arch. Carotid sinus is
supplied by the glossopharyngeal nerve which is the 9th cranial nerve; aortic
arch is supplied by the vagus nerve which is the 10th cranial nerve, they go to
the cardiovascular center in the medulla oblongata. Cardiovascular center has
two parts: cardiac and vascular parts, the cardiac center has two parts: cardio
acceleratory and cardio inhibitory. The vascular center has: vasoconstrictor
area, vasodilator area and sensory area.
-Cardio acceleratory sends its impulses to the heart through the sympathetic
system and causes: increase in heart rate and increase in contractility, if it is
inhibited, it causes decrease in the heart rate and decrease in the contractility.
-Cardio inhibitory sends its impulses to the heart through the parasympathetic
nervous system, through the vagus, and decreases the heart rate but it does
not affect the contractility neither stroke volume because the vagus does not
supply the ventricles.
-Baroreceptors sense any change in pressure whether decrease or increase,
they do not sense the pressure itself.
Slide#17:
-Vasoconstrictor area sends impulses downward through the sympathetic, and
cause vasoconstriction by increasing resistance. Inhibition in vasoconstrictor
area cause vasodilatation by decreasing resistance.
-Sensory area that receive the senses from the baroreceptors.
-Vasodilator area does not send impulses down, it works up stair in the medulla
oblongata because it does not supply the vessels. When it is stimulated, it
inhibits the vasoconstrictor area and vice versa.
Slide#18: ‫تبعوا معي من الساليدز‬
-the increase in pressure means increase in MAP.
-cardiovascular center sends less sympathetic signals to the heart and more
parasympathetic and less sympathetic to the vessels. Less sympathetic to the
heart, what it causes? Decrease in the heart rate, decrease in the contractility
and decrease in the cardiac output and therefore decrease the MAP back to
normal. Also, the impulses that are sent to the vasomotor center inhibit the
vasoconstrictor area and cause vasodilatation by decreasing resistance and
therefore decreasing MAP back to normal.
Slide#19:
-If the MAP fell below normal
less stretch in the baroreceptor
less
impulses go to the cardiovascular center
stimulates the cardio
acceleratory area and inhibit the cardio inhibitory
increase the heart rate
increase the contractility
increase the cardiac output. And in the same
time stimulation in vasoconstrictor area which cause vasoconstriction and
raise the resistance, if we raise the resistance, we raise the MAP back to
normal.
Slide#20:
-Sympathetic activity causes veins to constrict, if the veins are constricted,
how is this important? The veins have a large volume (60% or more of our blood
volume is found in the veins, and thus they are called: capacitance systems,
while arteries are resistance systems because their resistance is high “50% of
the TPR is found in arteries”.)
Slide#22:
-Chemoreceptors are located in the same area of the baroreceptors.
-Chemoreceptors are called peripheral chemoreceptors.
Slide#23:
-Decrease in pressure means decrease in flow and thus decrease in oxygen
levels, increase in carbon dioxide and increase in hydrogen ions. Therefore,
the chemoreceptors are activated.
Slide#25: THANK YOU.