Feedback Control and the Cardiovascular System Flashcards
What does a negative feedback system require?
Sensor
Control Centre
Effector
A controlled variable
What the controlled variable in the cardiovascular system?
Mean Arterial Blood Pressure
What are the sensors in the Cardiovascular system?
Baroreceptors
What are the effectors of the Cardiovascular system?
Heart
Blood Vessels
What is Blood Pressure?
Blood Pressure is the outward hydrostatic pressure exerted by the blood on the blood vessels
What is Systemic Systolic Arterial Blood Pressure?
Systemic systolic blood pressure is the pressure exerted by the blood on the walls of the arteries when the heart contracts
What is Systemic Diastolic Arterial Blood Pressure?
Diastolic Blood Pressure is the pressure exerted by the blood on the walls of the arteries when the heart relaxes
What is Mean Arterial Blood Pressure?
This is the average arterial blood pressure during a single cardiac cycle (Systolic and diastolic )
How is the Mean Arterial Blood Pressure calculated?
MAP = (2xDiastolic) + Systolic
———————————
3
This is because the diastolic period is 3 times the length of the systolic period
What is normal Arterial Blood Pressure?
< 140 Systolic and < 90 Diastolic
What is normal Range of Mean Arterial Blood Pressure?
70 - 105 mm Hg
What is the minimum Mean Arterial Blood Pressure required to perfuse the coronary arteries, brain and kidneys?
60 mm Hg
Where are the two groups of Baroreceptors located?
Aortic Arch
Carotid Sinus
What nerve takes the signal for the carotid sinus Baroreceptors?
The IXth Cranial Nerve
-Glossopharyngeal
What nerve takes the signal for the Aortic Baroreceptors?
The Xth Cranial Nerve
- Vagus Nerve
What type of receptors are Baroreceptors?
They are Mechanoreceptors that a sensitive to stretch.
What increases the firing rate of a Baroreceptor?
Increase in the Mean Arterial Blood Pressure
What decreases the firing rate of a Baroreceptor?
Decrease in the Mean Arterial Blood Pressure
What is the site of the first synapse for all Cardiovascular Control Centre signals?
Nucleus Tractus Solitarius
How does the control centre of the cardiovascular system receive a signal and act on it?
Information sent to the Nucleus Tractus Solitarius (NTS)
NTS relays information to other parts of the brain
Relay to Nucleus Ambiguus (Part of the autonomic Nervous system)
Regulates spinal sympathetic neurones
Using Cardiac output how is Mean Arterial Pressure worked out?
MAP = Cardiac Output x Total Peripheral Resistance
How is Cardiac Output worked out?
Cardiac Output = Stroke Volume x Heart Rate
What is the definition of Total Peripheral Resistance?
Total Peripheral Resistance is the sum of all peripheral vasculature in the systemic circulation
What is the Sympathetic nervous system’s affect on the heart?
Accelerates the heart rate (Tachycardia)
Noradrenaline actions on Beta 1 Receptors
What is the Parasympathetic nervous system’s affect on the heart?
Stimulation of the 10’th cranial nerve slow the heart down (Bradycardia)
Acetylcholine acts on Muscarinic receptors
What is Tachycardia?
Speeding up the of the heart
What is Bradycardia?
Slowing down of the heart
What increase the Stroke Volume of the heart?
Stimulation of the Sympathetic nervous system
What is the neurotransmitter used for the smooth muscles of the vasculature?
Part of the Sympathetic Nervous System
Noradrenaline
What occurs if the smooth muscles of the vasculature vasoconstrict?
Increase in TPR
Increase in MAP
What occurs if the smooth muscles of the vasculature vasodilate?
Decrease in TPR
Decrease in MAP
What is Vasomotor Tone?
Vascular Smooth Muscle partially constricted at rest
What increases the Vasomotor Tone?
Increased Sympathetic Discharge
What decreases the Vasomotor Tone?
Decrease Sympathetic Discharge
What happens in a decrease in B.P?
Decrease in Baroreceptor Discharge
Signal sent to Medulla of Brain
Vagal Activity decreased - Increases heart Rate
Sympathetic activity increased - Stroke Volume increased
Sympathetic increase - Vasoconstriction
TPR increases
What affect does the Parasympathetic system have on stroke volume?
No effect
What happens in a increase in B.P?
Increase in Baroreceptor discharge
Signal sent to Medulla
Vagal activity increased - Decrease in Heart rate
Sympathetic activity decreased - Decrease in Stroke volume
Sympathetic decrease - Vasodilation
TPR decreases
What is the disadvantage of Baroreceptors?
Only respond to acute changes in Blood Pressure
Baroreceptors re-set to a high MAP if B.P change lasts
