Download CV Lecture 5

Allied Science Physiology 09-10. Cardiovascular System. Lecture 6.
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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Mean arterial pressure determined by:
1.  _________
2.  ___________
3.  __________
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
Flow = pressure gradient / resistance
CO = MAP / TPR
Therefore MAP=CO x TPR = HR x SV x TPR
TPR is the total peripheral resistance: this is the combined
resistance of all blood vessels (remember the importance
of vasodilation and vasoconstriction)
This means that MAP is completely determined by HR, SV
and TPR
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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Figure 14.25a, b
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
Figure 14.25a, c
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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MAP = driving force for blood flow
F = ΔP/R
•  Regulating MAP critical to normal function
•  MAP < normal
–  Hypotension
–  Inadequate blood flow to tissues
•  MAP > normal
–  Hypertension
–  Stress on heart and walls of blood vessels
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
•  Short-term regulation – seconds to minutes (this
lecture)
–  Involves heart and blood vessels
–  Primarily neural control
•  Long-term regulation – minutes to days
–  Regulate blood volume
–  Involves kidneys
–  Primarily hormonal control
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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Negative feedback loops
•  Detector = baroreceptors
•  Integration Center = cardiovascular centers in
the brainstem
•  Controllers = autonomic nervous system
•  Effectors = heart and blood vessels
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
•  Baroreceptors = stretch
receptors
•  Arterial baroreceptors
–  High pressure baroreceptors
–  Sinoaortic baroreceptors
•  Location
–  Carotid sinus
–  Aortic arch
Figure 14.26
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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Figure 14.27
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
•  Medulla oblongata
•  Integration center for blood pressure
regulation
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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•  Location
–  Walls of large systemic veins
–  Walls of the atria
•  Low pressure baroreceptors = volume
receptors
•  Decrease in blood volume activates receptors
triggering responses that act in parallel with
baroreceptor reflex
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
•  Output
–  Sympathetic nervous system
–  Parasympathetic nervous system
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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•  Parasympathetic input to:
–  SA node (decrease HR)
–  AV node
•  Sympathetic input to:
–  SA node (increase HR)
–  AV node
–  Ventricular myocardium (increase contractility)
–  Arterioles (increase resistance)
–  Veins (increase venomotor tone)
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
Figure 14.28
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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Negative feedback loop to maintain
blood pressure at normal level
•  Detectors = baroreceptors
•  Afferents = nerves
•  Integration center = cardiovascular control
center
•  Efferents = autonomic nervous system
•  Effectors = heart, arterioles, veins
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
A person who had been lying down stands up quickly
–  Gravity causes venous pooling in the legs.
–  This causes a decrease in VR, causing a decrease in
CO
–  This causes a decrease in blood pressure.
–  Baroreceptors sense the decrease: reflex occurs
–  The reflex causes increased sympathetic and decreased
parasympathetic activity.
–  CO and TPR are increased.
–  Blood pressure is increased back to normal.
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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MAP
Arterial baroreceptors
Frequency of
action potentials
conducted to CNS
Cardiovascular control center
Parasympathetic activity
Sympathetic activity
SA node
Ventricular myocardium
Veins
Arterioles
Action potential
frequency
Contractility
Venomotor tone
Vasoconstriction
Compliance
Venous pressure
Negative
feedback
EDV
HR
SV
TPR
MAP
Figure 14.29
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
•  Released by adrenal medulla in response to sympathetic
activity
•  Increases mean arterial pressure
•  Acts on heart
–  Increases HR
–  Increases SV
•  Acts on smooth muscle of arterioles
–  Increases TPR
•  Acts on smooth muscle of veins
–  Increases venomotor tone
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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•  Vasoconstrictors
•  Increase TPR
•  Increase MAP
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
Figure 13.2
Allied Science Physiology 09-10. Cardiovascular System. Lecture 5.
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