09 Regulation of CVS Flashcards
What can affect the volume of venous return
Venoconstriction
Gravity
Respiratory and skeletal pumps
What is central venous pressure
Mean pressure in the right atrium
What are determined by the constriction of veins and arteries
Veins: 1) venous return 2) compliance 3) venous volume Arteries: 1) flow to the organ 2) MBP
What are the 3 categories of autoregulation
Myogenic
Metabolic
Injury (serotonin release from platelets to cause constriction)
List the local and systemic regulations of blood flow
1) autoregulation
2) substances released from endothelium
3) circulating hormones: kinins, ANP and vasoconstrictors (NA, AD, Ang II)
What vessels are not innervated by sympathetic nervous system at all
Capillaries, precapillary sphincter and some meta-arterioles
What vessels are not very heavily innervated by sympathetic nervous system
Skeletal muscles and brain
*More on kidneys, gut, spleen and skin
What is vasomotor centre, where is it and what does it regulate
VMC is composed of a vasoconstrictor (pressor) area, a vasodilator (depressor) area and a cardioregulatory inhibitory area
Vasomotor centre is located in the medulla and lower 3rd of pons. Medial portion transmits signals via vagus nerve to reduce HR. Lateral portion transmits signals via sympathetic nerves to stimulate HR and contractility
How does NA stimulate the increase in heart rate
Binding to B1 receptor causes the activation of Gs and hence the formation of cAMP which activates PKA. PKA increases the duration of opening of L type Ca2+ channel and RyR
What nerve supplies the baroreceptors
Carotid sinus: glossopharyngeal nerve
Aortic arch: vagus nerve
What is the sensitivity of baroreceptors at carotid sinus and why is it suited for its function
60 - 180 mmHg
Because it is most sensitive between 90 - 100 mmHg
