L5 - Hypertension Diagnosis / Concepts Flashcards
Short term mechanisms for regulating blood pressure
- regulate blood vessel diameter
- HR
- contractility
Long term mechanisms for regulating BP
regulating blood volume
Calculation for blood pressure
BP = Cardiac output * peripheral resistance
What is the vasomotor centre
Cluster of sympathetic neurons found in the medulla.
Sends efferent motor fibres that innervate smooth muscle of blood vessels.
Increase in sympathetic activity will lead to…
Vasoconstriction
Decrease in sympathetic activity will lead to…
Vasodilation
Short term regulation of rising blood pressure
- rising blood pressure
- leads to stretching of arterial walls
- stimulates baroreceptors in carotid sinus, aortic arch and other arteries of the neck and thorax
- increased impulses to brain
Where are baroreceptors found?
- carotid body
- aortic body
- wall of large arteries of the neck and thorax
Describe the effect of baroreceptors
- baroreceptors entered the medulla (tractus solitaturs)
- secondary signals inhibit the vasoconstrictor centre of medulla and excite the vagal parasympathetic centre.
Effects: - Vasodilation of veins and arterioles
- decreased heart rate and strength of heart contraction
Therefore, excitation of baroreceptors by high pressure in the arteries reflexively causes arterial pressure to decrease.
What is the effect of increased parasympathetic activity on the heart and blood pressure?
- increased activity of vagus (parasymp) nerve
- decreased activity of symp cardiac nerves
- reduction of heart rate
- lower cardiac output
- lower BP
Effect of decreased sympathetic activity on arteries and blood pressure?
- decreased activity of vasomotor fibres (symp nerve fibres)
- relaxation of VSM
- Increased arterial diameter
- lower BP
Describe short term regulation of falling blood pressure?
- baroreceptors inhibited
- decreased impulses to the brain
- decreased parasymp activity
- increased symp activity
Effects
- HEART: increased HR & contractility
- VESSELS: increases v.constriction
- ADRENAL GLAND: epinephrine & norepinephrine release, enhancing HR
- Contractility & v.constriction
- increased blood pressure
Effect of baroreceptors
- Baroreceptors entered the medulla (tractus solitarius)
- Secondary signals inhibit the vasoconstrictor centre of medulla & excite the vagal parasymp centre.
Effect
- vasodilation of veins and arterioles
- decreased HR and strength of contraction
Overall effect
- excitation of baroreceptors by high pressure in the arteries reflexively causes arterial pressure to decrease
Effect of increased parasympathetic activity and decreased symp activity on heart and bp
- increased vagus activity (p.symp)
- decreased activity of symp cardiac nerves
- reduction of HR
- lower co
- lower bp
Effect of decreased sympathetic activity on arteries and blood pressure
- decreased activity of vasomotor fibres (symp)
- relaxation of VSM
- increased arterial diameter
- lower bp
