Regulation of CVS 10 Flashcards
Stoke Volume Equation:
SV = End-diastolic volume - end-sytolic volume
Cardian Output equation:
CO = HR x SV
Mean systemic arterial pressure equation:
Mean BP = CO x TPR
What are the two parts of the CVS?
Systemic and pulmonary
What is venous volume distribution affected by?
- peripheral venous tone
- gravity
- skeletal muscle pump
- breathing
What mainly controls flow comtrol?
Arterioles
Constriction of arterioles =
- blood flow to the organs they serve
- mean arterial blood flow
- pattern of distribution if blood to organs
Number of adrenoreceptos will affect the blood flow to an organ
How is flow altered?
Affecting vessel radius
Methods of regulating flow:
- local mechanisms ( intrinsic to smooth muscle or close to it)
- hormonal
- autonomic nervous system
What is autoregulation?
The intrinsic capacity to compensate for perfusion pressure by changing vascular resistance
What are the two theories for autoregulation?
Myogenic: smooth muscle fibres respond to stretch so as pressure rises, contraction occurs to kepp flow the same
Metabolic: IF flow to a bed decreases, more metabolites are produced which cause vasodilation and increased flow which in turn washes away the produced metabolites
What endothelial substances regulate blood flow?
Endothelin 1
Nitric Oxide
Thromboxane A2
Prostacyclin
Which hormones affect systemic circulation blood flow?
Kinins and ANP (vasodilators)
Vasopressin, A2 and noradrenaline (vasoconstrictors)
Generalisation of ANS:
Sympathetic controls flow
Parasympathetic controls heart rate
Which vessels do sympathetic fibres not innervate?
Capillaries. Distribution of innervated vessels is not equal. More supply kidney, gut, spleen and skin than skeletal muscle and the brain
What does circulating noradrenaline preferably bind to?
Alpha-1-adrenoreceptors for smooth muscle contraction and vasoconstriction
What does circulating adrenaline preferably bind to?
Beta-2-adrenoreceptors to cause vasodilation to some organs
Where is the vasomotor centre located?
Bilaterally in the reticular substance of the medulla and lower third of the pons
What does the VMC comprise of?
- Vasoconstrictor area
- Vasodilator area
- Cardioregulatory Inhibitory area
What do lateral portions of the VMC control?
Heart rate and contractility
What do medial portions of the VMC control?
Signals to Vagus nerves to the decrease heart rate
How can cardiac force of contraction be increased?
Starlings Law
Describe cascade post noradrenaline binding to beta-1-adrenoreceptors:
Activated Adenylate cylase which converts ATP to cAMP. This activate PKA which phosphorylates L-type Calcium channels/ SR release channels and SERCA increasing intracellular Ca2+ concentration. This increases contraction of heart
How can stroke volume be increased?
Increased plasma adrenaline
Increased sympathetic activity
Where do baroreceptors feedback to?
VMC via glossopharyngeal nerve if carotid sinus
via vagus if aortic arch
When is baroreceptors most sensitive?
90-100mmHg
What does increased baroreceptor firing lead to?
Increased parasympathetic activity and decrease in sympathetic
