Final Exam Review Flashcards
What is the purpose of arterial baroreflex?
to regulate blood pressure and maintain circulation to brain and other organs.
How do you rearrange Ohm’s law to understand blood pressure regulation?
Q = ∆P / R
to
MAP = Q x TPR
Blood pressure rises with exercise to satisfy Ohm’s law. To ensure a linear increase in blood flow to active muscle during exercise___________
the sympathetic nervous system causes vasoconstriction to increase blood pressure and drive blood flow
To control MAP, you regulate the _______ and the _________
heart; vasculature
What roles does the sympathetic nervous system play in heart rate, vasoconstriction and TPR?
Increases heart rate (increase Q), cause vasoconstriction to increase TPR
What is parasympathetic nervous system responsible for?
Decreasing heart rate
To regulate blood pressure you can either change/regulate the _____ or the ________
Pump (heart) or blood (resistance)
What is reflex cardiovascular control?
built in pathways that are responsible for monitoring change, send signals to brain to make changes to sympathetic or parasympathetic neurons.
What do baroreceptors do when you stand up?
baroreceptors will detect change in blood pressure and send signal to central environment (brain, brain stem). Change behaviour to correct problem and get everything back to normal
Feedback regulation of room temperature can be compared to the arterial baroreflex. Explain this concept.
o Air conditioning made room to cold, furnace turns on to correct the problem in the loop.
o Negative feedback reflex. Room temperature dropped so it was brought back up to correct the problem.
o Idea of sensitivity. Room temp dropped to 18, thermometer stopped working. We don’t detect the problem. Not until minutes later, sensor starts to work and initiates process to bring temp back to 21. Less sensitive system. Such as when system gets older and parts start to fail.
What is the mechanism that governs blood pressure under ALL physiological conditions? (whether we are exercising or not)
The Arterial Baroreflex
Explain how impaired baroreflex function can be seen using a head up tilt.
Table slowly head up tilt (stimulated standing movement).
o Healthy individual maintains steady and well-regulated blood pressure throughout entire protocol.
o In someone who doesn’t have a working arterial baroreflex, blood pressure will plumet when the head up tilt is initiated. Insufficient blood pressure and can’t drive blood to the brain. Which causes fainting. These people have issues with daily life.
Effect of head tilt on sympathetic nervous system activity?
increase
Effect of head tilt on blood pressure?
mean pressure maintained, therefore no change.
Effect of head tilt on femoral artery blood flow?
decreased
Effect of head tilt on stroke volume?
decrease
Effect of head tilt on calf circumference?
increase
Effect of head tilt on heart rate?
increase
Why do these neural and hemodynamic changes occur during head up tilt? Use baroreflex in response
o Arterial baroreflex will detect these changes. Elicits changes. Increased sympathetic activity which causes vasoconstriction in blood vessels. This results in an increase in TPR. All of this results in the mean pressure maintained (no change). Not changed throughout the stimulated standing or on our own.
What are the sensory components of the baroreflex?
baroreceptors and sensory neurons
What are the central components of the baroreflex?
brain and brainstem
What is the efferent component of the baroreflex?
autonomic nervous system
Explain the stretch responses in baroreflex
o Blood vessels will stretch and reflex dependant on what blood pressure is. If blood pressure is high, vessels will stretch. If falls, vessels get smaller and will detect less stretch. Stretch is caused by changes in pressure. First step of the arterial baroreflex, stretch receptors, sensors, monitors.
Do baroreceptors know exactly what the blood pressure is?
o Baroreceptors don’t know exactly what blood pressure is but they detect stretch to “infer” what it is.
If blood pressure rises, P1 element will _____. Transmural pressure is ______
grow; larger
What is transmural pressure?
o Transmural pressure is the difference in pressure from inside of vessel compared to outside. (TP = P1 – P2). and vice versa.
Do baroreceptors respond to transmural pressure?
Yes
Blood pressure is ______ in diastole and _______ in systole.
low; high
Explain baroreceptor firing in a low MAP setting
o In low MAP (dehydrated, blood pressure low), every time there is a systole – there is a spike. Baroreceptor firing. Systole = stretches/larger vessel diameter. This causes baroreceptor to fire. In diastole, it is not firing. Diastole is associated with smaller vessel diameter. Eliciting less stretch.
Explain baroreceptor firing at 100 MAP
o 100 MAP, baroreceptors still responding to stretch (systole). Diastole, baroreceptors fire less. Overall more firing during systole since the MAP is higher than low.
Explain baroreceptor firing at high MAP
o In high MAP (hydrated, blood pressure is higher),
o Baroreceptors respond to pulsatile changes in BP. Systolic pressure causes vessels to stretch which causes baroreceptors to fire. Diastole causes vessels to get smaller so don’t fire.
o If increase MAP, stretch vessels. In diastole will be greater than lower pressure system.
What is baroreceptor unloading?
decreased blood pressure resulting in less vessel distension and therefore less baroreceptor firing. (blood pressure falling, such as when you stand up, head up tilt)
What is baroreceptor loading?
increased blood pressure resulting in more vessel distension and therefore more baroreceptor firing (doing hand stand, neck pressure)
What are the two types of baroreceptor populations?
Arterial and cardiopulmonary baroreceptors
Where are arterial baroreceptors located?
carotid sinuses and aortic arch
Where are cardiopulmonary baroreceptors located?
right atrium, right ventricle, pulmonary arteries (in the lower pressure areas)
What does arterial baroreceptors respond to?
changes in blood pressure
What do cardiopulmonary baroreceptors respond to?
change in blood volume
Sympathetic neurons innervate the ______, ______/_____ and _______.
heart, arteries/arterioles and veins
Parasympathetic neurons innervate the ______.
Heart
Describe the events that occur after an increased BP stimulus (transmural pressure)
Stretch aortic arch and carotid sinuses to signal baroreceptors to fire more. Sends signals to brain and brain stem to tell sympathetic nervous system to lessen its activity. Which reduces heart rate, stroke volume to decrease cardiac output. Increased parasympathetic activity, slows heart rate. Reductions in TPR. Opposite to initial change. Try to bring it back down.
Describe the events that occur after a decreased BP stimulus
baroreceptors detect less stretch. Need to bring blood pressure back up. Constrict blood vessels. Opposite
Give an overall explanation of the Neural/Hemodynamic Responses to Head up tilt chart.
Main diagram/chart description = Some will be stimulus, some will be response. You stand up, Gravity starts pulling blood downwards. That is the stimulus. Calf circumference increases, representative of the stimulus. This attenuates how much blood is returned to heart. Less blood returning to heart means less blood to pump. Reduction in stroke volume/aortic flow.
Why can we survive in an upright position? What is responsible for this?
baroreflex unloading stimulus. Tries to maintain pressure. Increases TPR and maintains cardiac output therefore mean pressure is maintained – no change. We can survive in up right posture. Baroreflex is responsible for this.
What is the mean arterial pressure (MAP) for young healthy individuals? Any differences between male and female?
MAP for young, healthy individuals have set point of around 100. Males have higher than females. Set point does change with exercise.
Where does information come into the brainstem from in the baroreflex negative reflex feedback?
from cranial nerves IX and X
What is the first neurone in the baroreflex negative reflex feedback?
Nucleus tractus solitarius (NTS)
If the nucleus tractus solitaires activity increases, it will ________ firing of neurons n_______ a_______ and d_______ m_______ n_______.
increase; nucleus ambiguous and dorsal motor nucleus.
The N______ a_______ and the d______ m_______ n______ affect parasympathetic outflows. The parasympathetic nervous system _______ the heart.
nucleus ambiguous and dorsal motor nucleus; inhibits
Other option is the n______ t_______ s_______ affects the c_______ v______ l_______ m_______. If NTS is high, CVLM will be ______. This is an _______ neurone.
nucleus tractus solitarius; caudal ventro lateral medulla; high; excitatory
C_______ v________ l_______ m______ is _________ over the r_______ v_______ l_______ m_______.
Caudal ventro lateral medulla; inhibitory; rostral ventro lateral medulla
If CVLM is activated, it will ________ the RVLM.
inhibit
If RVLM is not inhibited, it is _______!
firing