ANS Flashcards
(19 cards)
Where is the sympathetic nervous system found? (Which spinal regions)
Thoracolumbar (T1- L2/3)
Where is the parasympathetic nervous system found? (Which spinal regions?)
Cranio-sacral (Cranial nerves III, VII, IX, X and Sacral S2-S4)
In terms of neurone length, how are sympathetic neurones different?
Shorter pre-ganglionic and longer post-ganglionic
In terms of neurone length, how do parasympathetic neurones differ?
Longer pre-ganglionic neurones and shorter post-ganglionic neurones
What are the two divisions of the autonomic nervous system?
Sympathetic and Parasympathetic
What is the overall effect of increased sympathetic activity on the heart?
Increase in heart rate (chronotropy), increase in force of contraction (inotropy)
Where does the sympathetic nervous input act on the heart?
B1 adrenoreceptors in the SAN, AVN, myocytes
What does the sympathetic branch of nervous system release?
Pre-ganglionic: ACh, post-ganglionic: NA
Where is NA released from in the axons of sympathetic neurones?
Varicosities
How does increased sympathetic activity to the heart increase force of contraction?
More Ca2+ in the cell, more can bind to troponin C, more contraction for same length of fibre
How does activation of phsopholamban increase heart rate/chronotropy?
When phospholamban is activated, it no longer inhibits SERCA, TF calcium can be taken back up into the SR, TF membrane potential repolarises much quicker meaning myocyte is ready to depolarise quicker–> action potentials can fire more frequently.
What is phospholamban?
Protein present on SR membrane, usually when inactivated inhibits SERCA
When protein kinase a is activated, what effects does it have?
Releases two catalytic sub units which phosphorylate L type calcium channels, increases sensitivity of Troponin C to calcium, phosphorylates phospholamban.
When a G protein is activated, what energy swap/trade is there?
The GDP attached to the g protein dissociates, a GTP binds.
What is the second function of the alpha i sub unit when released? (In muscarinic receptors)
Galpha i activates muscarinic K+ channels, they then open and allow and efflux of K+ out of the cell. The K+ leaving the cell makes the membrane potential more negative: hyperpolarisation.
What nerve acts on the hear with paarsympathetic activity?
Vagus nerve
Where does the parasympathetic input to the hear act?
M2 receptors in the SAN, AVN (doesnt act on myocytes)
What happens to the amount of [Ca2+]i when under parasympathetic activity? What is the effect?
Calcium channels arent activated TF less in the cytosol, also phospholamban remains inactivated and so inhibits SERCA, TF the calcium stays in cytosol longer, means contraction lasts longer but not extra force.
What effect does hyperpolarisation in response to parasympathetic activity have?
Lowers frequency of action potentials (ie decreases HR/chronotropy), also as it is harder to reach threshold, reduces AVN conductance velocity.
