5. Autonomic Nervous System Flashcards
Where do parasympathetic nerve fibres originate?
Cranial and sacral nerves
What are preganglionic vs postganglionic parts of parasympathetic nerves like?
Pre: Long and myelinated
Post: Short and unmyelinated
What neurotransmitter is used in parasympathetic nerves?
ACh
Where do sympathetic nerves originate?
T1 to L3 in spinal cord
Describe preganglionic sympathetic neurons
Short, myelinated
ACh
Describe postganglionic sympathetic neurons
Long, unmyelinated
NA
What are the two types of cholinergic receptor?
Nicotinic (preganglionic)
Muscarinic (postganglionic)
Where are muscarinic receptors found?
On effector cell membranes
What occurs at an M2 muscarinic receptor?
Inhibitory response on cardiac tissue
Increases K+ conductance and inhibits Ca channels
What occurs at M3 muscarinic receptor?
Excitatory response in the digestive system
G protein couples to Ca++ second messenger system
Where are adrenergic receptors found?
Effector organ synapses
What response occurs at an alpha 1 receptor?
Located on sympathetic target cells
G protein couples to CA++ second messenger system
eg. vasoconstriction
What response occurs at an alpha 2 receptor?
G protein couples to inhibit cAMP system
Decreased smooth muscle contraction
What response occurs at a beta-1 receptor?
Couples via G protein to cAMP
eg. contraction of cardiac muscle
What response occurs at a beta-2 receptor?
Couples via G protein to cAMP
eg. relaxation of smooth muscle
