Neuroscience 11 - Sympathetic nervous system and renin angiotensin system Flashcards
Where are noradrenaline and adrenaline systhesised in the neurone?
In the terminal varicosity.
What are the subdivisions of adrenoreceptors?
2 groups:
- Excitatory effects on smooth muscle = a-adrenoreceptor-mediated.
- Relaxant effects on smooth muscle + stimulatory effects on heart = b-adrenoreceptor-mediated.
Where are b1, b2 and b3 adrenoreceptors found?
- B1 = cardiac muscle, smooth muscle in GI.
- B2 = Bronchial, vascular and uterine smooth muscle.
- B3 = fat cells, smooth muscle in GI.
What are A1 and A2 adrenoreceptors?
- A1 = Located post-synaptically (on effector cells). Mediating constriction in resistance vessels.
- A2 = Located presynaptic (nerve terminal membrane). Activation by neurotransmitter causes negative feedback. HOWEVER, some are post-synaptic on vascular smooth muscle.
What is the mechanism for A1 adrenoreceptors?
- Based on G-proteins activating PLC enzyme.
- Produced IP3, which releases stored calcium in the cell.
- This causes activation of smooth muscle and platelets.
What is the mechanism for A2 and B arenoreceptors?
- G-protein linked.
- Activates cAMP.
- This is a relaxant in smooth muscle and GI. BUT stimulates heart by increasing intracellular Ca2+.
Which adrenoreceptors does noradrenaline activate?
A1, A2 and B1.
Which adrenoreceptors does adrenaline activate?
A1, A2, B1, B2.
Which adrenoreceptors does dopamine activate?
Weak effects on A1 and B1. Has its own receptors.
What are two synthetic catecholamines and which adrenoreceptors do they activate?
1, Isoprenaline = B1, B2.
2. Phenylephrine = A1.
What is the effect of systolic BP by noradrenaline, adrenaline and isoprenaline?
- Noradrenaline = Strong increase.
- Adrenaline = Increase.
- Isoprenaline = Slight increase.
What is the effect of diastolic BP by noradrenaline, adrenaline and isoprenaline?
- Noradrenaline = Increase.
- Adrenaline = Slight decrease.
- Isoprenaline = Decrease.
What is the effect of mean BP by noradrenaline, adrenaline and isoprenaline?
- Noradrenaline = Increase.
- Adrenaline = Slight increase.
- Isoprenaline = no change.
What is the effect of HR by noradrenaline, adrenaline and isoprenaline?
- Noradrenaline = Decrease.
- Adrenaline = Increase.
- Isoprenaline = Increase.
What causes Renin release? (3)
- Decrease in NaCl.
- Decrease in BP.
- B1 receptor activation in kidney by sympathetic nervous system.