Karius Autonomics ibook notes Flashcards
Movement: the Reflex
simplest level of integration between CNS and PNS occurring in the brain
afferent nerve
sensory, sends message to CNS about body or environment
efferent nerve
moto, sends command to PNS (then to muscles)
Simples reflexes
typically have just one synapse (two neurons involved: afferent and efferent) but may have two.
plan of a reflex
sensory information causes an AP to be delivered from the pre-synaptic neuron to the CNS where it synapses with a post-synaptic neuron, which initiates an AP down the efferent axon to a target muscle (alpha motor neuron based). Action potential from efferent causes an action potential on the muscle, exciting it and causing contraction.
Do reflexes require the brain to be involved?
All reflexes “notify” the brain by having a branch of the first neuron synapse or go to the brain, directly/indirectly
Reflexes in the ANS: part 1
the sensory component which is attempting to convey information about sensation internally and externally
Reflexes from the ANS: part 2
brain processing information received from ANS, similar to somatic side. this is all the information she has in the ibook on part 2.
the efferent side of ANS: part 3
message relayed to effectors (not skeletal muscle) –> smooth muscle and glands.
two parts: sympathetic and parasympathetic system
ANS anatomy, general considerations
always has two neurons, two synapses in the pathway going from the spinal cord to the effector organ in the periphery
ANS has how many neurons?
Two: one preganglionic (in the CNS) which synapse on a postganglionic neuron (outside the CNS).
ganglion
a collection of neuron cell bodies
equivalent of a nucleus in the brain
Pre-ganglionic neuron
small, sparsely myelinated B Fiber (relatively slow conduction velocity)
goes from CNS to a ganglion
B-fibers
Post-ganglionic neuron
small, unmyelinated type C fiber
C fibers
travels to actual target organ and synapses on that to do the brains command
ANS two divisions
sympathetic and parasympathetic
Parasympathetic
rest and digestL leave the CNS from the cranium and the sacrum
regardless of where they leave the CNS, the pre-ganglionic axons travel to the ganglion, which is located near the target tissue
Where is the “Ganglion” in the ANS?
on or near the target organ
Preganglionic fiber: short or long
long, has to be because it leaves from the cranium or sacrum and travels to the post-ganglionic target
Post-ganglionic fiber
short, only goes short distance
“PLS” nemonic
Parasympathetic, Long, then Short
Sympathetics: preganglionic
leave CNS via white rami from thoracic and lumbar regions
Preganglionic Sympathetics: regardless where they leave, where do preganglionic sympathetics have to go?
they have to go to:
the sympathetic chain
the mesenteric (inferior and superior) ganglia
the celiac ganglia
if axons go to the mesenteric or celiac ganglia, when then?
they have to pass through the sympathetic chain without synapsing THEN they go to these ganglia and synapse.
sympathetics pre ganglia: short or long?
short
Sympathetic nemonic “SSL”
sympathetic, short, long
Parasympathetic synapse #1 Where is the ganglia
located in the ganglia that are IN/ON/NEAR the target organ
Parasympathetic synapse #2 Between what structures
between preganglionic axon and the post-ganglionic dendrite
Parasympathetic synapse #3 NT
NT released by pre-synaptic terminal of the pre-ganglionic cell is acetylcholine
stored in clear vesicles
action is limited by acetycholinesterase bound to the post-ganglionic cell membrane
Parasympathetic synapse #4 receptors for NT
nAChR 5 subunit receptor, each coded for by a different gene
Parasympathetic synapse #5 receptor response
nAChR (ligand gated, not voltage gated) –> causes fast ESPS in the post ganglionic cell
Parasympathetic synapse #6 Synapse #2
between post-ganglionic neuron and the effector (smooth muscle or gland)
Parasympathetic synapse: IF smooth muscle is the effector
axons travel along smooth muscle and have little bumps called vericosities that contain the ACh and from which they are released, there may be half a dozen of them
Parasympathetic synapse: Postganglionic receptor specializations
none. there are none. just the nAChRs
Parasympathetic synapse: Postganglionic synapse #2 NT on effector
AChR —> mAChR
Parasympathetic synapse: Effector receptor
muscarinic receptor mAChR
M2
mAChR found on cardiac tissue, connected to Gi protein. activation decreases cAMP and an eventual increase in K conductance
M3
found on glandular tissues
ACh binding causes increase in IP3, DAG, and an intracellular increase in Ca levels because it is connected to Gq
M4
receptors are autoreceptors on neurons and control acetylcholine release, they connect to Gi proteins and inhibit adenylate cylcase
Gi
connect to M2 and M4, inhibit adenylate cyclase
Sympathetic: Synapse #1 fast ESPS
pre-gang axon synapsing on post-gang dendrite
ACh –> nAChR
fast ESPS
Sympathetic Synapse #1 IPSP
uses dopamine
released by interneurons within the ganglia
Sympathetic: Synapse “slow ESPS”
produced by ACh at the M1 receptors, lasts about 30 sec
Sympathetic: Synapse #1 “Late, slow ESPS”
caused by gonadotropin releasing hormone being used as a neurotransmitter by some pre-ganglionic cells
GnRH (a peptide)
causes late, slow acting ESPS
no all sympathetic synapses show these
Sympathetic: Synapse #2 where?
between the sympathetic post-ganglionic neuron and effector
norepinephrine (same as noradrenalin) and ATP, neuropeptide Y (particularly if they innervate blood vessels)
vericosities contain granulated densities
Sympathetic: Synapse #2 norepinephrine
noradrenalin
Adrenergic receptors
serpentine, metabotropic (connects to a G protein), higher affinity for norepinephrine than epinephrine
two kinds (alpha 1 and alpha 2)
Alpha 1 receptor
Adrenergic
serpentine, metabotropic (connected to g protein), prefers norepinephrein than epinephrine
has three subtypes
1a, 1b, 1d (1c was reassigned)
Sequence of events after Norepinephrine activates an alpha 1 receptor
increase IP3, DAG, and eventually to a decrease in K efflux and depolarization
Alpha 2 receptor
Adrenergic
serpentine, metabotropic (connected to g protein), prefers norepinephrein than epinephrine
has 3 subtypes
2a, 2b, 2c
Alpha 2 receptor sequence of events
norepinephrine binds
all 3 decrease cAMP and lead to increase of efflux of K and decrease in CA INFLUX
beta adrenergic receptor
three subtypes, serpentine, have greater affinity for epinephrine than NE but will bind both
metabotropic
binding of NE to beta-adrenergic receptor produces an increase in cAMP
