Global and local control of circulation Flashcards
What is basal tone?
minimal amount of contraction in vascular smooth muscle in resting conditions
What is resting sympathetic tone?
in resting conditions, have basal sympathetic activity (through Epi). Allows contraction of smooth muscle, so have higher resistance than basal tone
What happens to SM tone when you increase sympathetic adrenergic influence?
active vasoconstriction
if you remove it or decrease: passive vasodilation
Where are alpha 1 receptors found?
adrenergic: work through NE or epi
when activated lead to vasoconstriction/venoconstriction
*not found in heart or brain! (no wanna constrict)
How do alpha 1 receptors work?
constriction leads to decrease in compliance or increase in tone in veins
- causes increase blood flow back to the heart
- incr BP
Where are Beta 1 receptors found?
only on heart! (no SM)
How do Beta 1 receptors work?
increase contractility of heart plus incr HR
Where are Beta 2 receptors found?
25% in heart and rest in smooth muscle!
- heart: same as beta 1- incr contractility + HR (used during heart damage)
- SM: vasodilator
How do cholinergic receptors work?
muscarinic recepotrs stimulated by Ach
What do cholinergic parasympathetic receptors innervate?
splanchnic, genitalia, bladder and large bowel
NO SM!
What do sympathetic cholinergic receptors innervate?
sweat glands! release Ach on them
Where are baroreceptors found?
carotid sinus [IX] (more sensitive) and aortic arch [X]
When are baroreceptors activated?
During decrease in Pressure (CHANGES)- start firing more
How do baroreceptors work?
they activate sympathetic NS and shut off para
- cause veno and vasoconstriction (incr peripheral resistance)
- incr HR (incr CO)
- incr contractility (more SV- incr CO)
- -> Incr BP!
*negative feedback: sense higher BP so fire to active parasympathetic to balance it out
What happens to baroreceptors in patients with HTN?
They reset at the higher pressure, less sensitive to changes
