HUBS192 Lecture 10 - Controlling the Heart and Blood Pressure Flashcards
what is the pattern of rise and fall of blood pressure?
cyclical pattern of rise and fall
what are 2 things that high pressure in the large systemic arteries is linked to?
1) linked to ventricular contraction and ejection of blood
2) pulsitility in major arteries (systolic / diastolic)
what is the critical factor that the human body is trying to control at all times?
mean arterial blood pressure (MAP)
what is mean arterial blood pressure (MAP)?
the driving force is an important determinant of blood flow and is tightly regulated within a narrow range
what is the blood pressure in the major arteries?
blood pressure is high in the major arteries (oscillatory)
what is the blood pressure in veins?
blood pressure is very low in veins
how is oscillatory nature reduced?
reduced by blood pressure falling steeply across the arterioles, capillaries, and venules
what helps to drive the unidirectional flow of blood in terms of pressure?
the large pressure difference (ΔP) between the major arteries and the veins helps to create a driving force for unidirectional blood flow
what is the relationship between difference in pressure and blood flow?
the greater the pressure difference, the stronger the flow of blood throughout your system
why does the body maintain mean arterial blood pressure at a high level at all times?
because if the level was any lower then there would be decreased pressure difference compared to the veins and there would be less blood flow
what are extremities?
the parts of your body that are located away from the heart that require the largest blood flow
e.g the brain
what is arterial blood volume and pressure determined by?
the balance between blood flow “in” and blood flow “out”
what is effect of having a larger blood flow “in” to the arteries?
blood pressure will be increased and blood volume will also increase
what is the effect of having a larger blood flow “out” of the veins?
blood pressure will fall and blood volume will decrease
what 3 features are associated with blood flow “in”?
1) fills arteries
2) increases arterial blood volume
3) raises arterial pressure
what 3 features are associated with blood flow “out”?
1) drains arteries
2) decreases arterial blood volume
3) lowers arterial pressure
what 3 things determine blood flow “in”?
1) ventricular contraction
2) ejection of blood
3) CARDIAC OUTPUT
what 2 things determine blood flow “out”?
1) capillary flow
2) controlled by resistance of the arteries
what is cardiac output?
blood flow leaving the heart
what 3 things does the balance of blood flow “in” and blood flow “out” determine?
1) increase cardiac output (increases inflow)
2) increase resistance (decrease outflow)
3) increase arterial volume and pressure
what are the 2 ways to increase mean arterial blood pressure (MAP)?
1) increase cardiac output (increase inflow)
2) increase resistance (decrease outflow)
how does increased resistance decrease blood outflow?
increase the difficultly of blood moving blood out into the capillaries, trapping blood in the arteries, keeping blood volume high
what is the equation for MAP (arterial pressure)?
MAP= CO x TPR
P= Q x R
Arterial pressure= Cardiac output x Total peripheral resistance
what are the 2 determinants of cardiac output?
1) stroke volume
2) heart rate
what is the equation for cardiac output?
CO = SV x HR Cardiac Output (L/min) = Stroke Volume (L/beat) x Heart Rate (beats/min)
what is stroke volume in terms of contraction?
the contraction strength
what is heart rate in terms of contraction?
the contraction speed
what does SV stand for?
stroke volume
what is the communication role of the brain to the heart?
the brain functions to tell the heartbeat to speed up or slow down
where is the homeostasis of arterial blood pressure?
coordinated within the brainstem
what is afferent input?
input from the systems that monitor from the body that communicate about what is happening in the body (sensory)
what is efferent output?
communication from the brain in response to afferent input out to the heart and vessels
where does afferent input come from?
input from both the CNS and the ‘periphery’
what are baroreceptors?
receptors that measure blood pressure
where are baroreceptors mainly located?
located in the aortic arch and in the carotid artery
what do baroreceptors sense?
they sense stretching of an artery by detecting artery stretch as they are embedded in the artery wall
what is the function of baroreceptors?
send afferent input to the brain about blood pressure all the time
what is the relationship between the amount of signal sent by baroreceptors and blood pressure?
- when blood pressure increases the baroreceptors send a larger signal to indicate to the brain that blood pressure is too high
- when blood pressure decreases the baroreceptors send a less of a signal to indicate that blood pressure is falling
what are the 2 systems that the brain uses to control the function of the heart?
1) parasympathetic nervous system neurons (brake)
2) sympathetic nervous system neurons (accelerator)
what colour is the parasympathetic nervous system represented by?
purple, the rest and digest system
what colour is the sympathetic nervous system represented by?
green, the fight or flight system
what is a way to reduce high blood pressure?
reducing the blood flow “in” by pushing less blood into the arteries from the PSNS by efferent output through the vagus nerve slows down heart rate
what is the vagus nerve?
the vagus nerve connects the brain to the heart at the SA node and the AV node
what do the SA (sinoatrial) node and the AV (atrioventricular) node have in common?
both are responsible for timing within the heart
what is the function of the vagus nerve?
the vagus nerve in the parasympathetic nervous system decreases heart rate
is the vagus nerve associated with the SNS or the PSNS?
parasympathetic
what is a way to increase low blood pressure?
the brain uses the sympathetic nervous system signalling through the sympathetic chain ganglia to communicate with the SA node to fire faster (more depolarisations = more contractions) and the communicates with the AV node to make the pause in the signal shorter therefore increase heart rate and stroke volume
is the sympathetic chain ganglia associated with the PSNS or the SNS?
sympathetic nervous system
what is the PSNS neural control signal?
vagus nerve
what is the SNS neural control signal?
sympathetic chain ganglia and the purkinje fibres
what is known as the “brake” of cardiac output?
parasympathetic nervous system
what is known as the “accelerator” of cardiac output?
sympathetic nervous system
when is cardiac output greatly increased?
during exercise
what is cardiac output measured in?
L/min
