lecture 7 - autonomic NS Flashcards
ANS operates without conscious control via
reflex arcs to regulate activity of smooth muscle, glands, and cardiac muscle
components of ANS reflex arc
sensory receptors (mostly interoceptors)
sensory neurons
integrating centres in CNS (brainstem and hypoth)
motor neurons
visceral effectors
ANS vs SNS - sensory input
ANS - mainly interoceptors, some from somatic senses/special senses
SNS - from somatic senses/special
ANS vs SNS - motor neuron pathway
ANS - usually 2 neuron, pre and post ganglionic. OR preganglionic neurons may synapse with cormaffin cells
SNS - one neuron pathway, from CNS directly with affector
ANS vs SNS - NTs and hormones
ANS - all preganglionic = ACh, most synpathetic post ganglionic = NE, most parasympathetic post ganglionic = ACh, cromaffin cells = E/NE
SNS - all somatic motor neurons release only ACh
ANS vs SNS - control of motor output
ANS - involuntary control from hypothalamus, limbic system, brainstem and spinal cord
SNS - voluntary control form C cortex, corpus striatum, cerebellum, brainstem, cord
ANS vs SNS - effectors
ANS - smooth muscle, cardiac, glands
SNS - skeletal muscle
sympathetic division ______ organ function
excites
ANS vs SNS - responses
ANS - contraction/relaxation of smooth muscle, increased/decreased rate/force of cardiac contraction, +/- secretions of glands
SNS - contraction of skeletal muscle
parasympathetic division ______ organ function
inhibits
dual innervation
when an organ is supplied by both para and sympathetic fibres
preganglionic neuron
myelinated, extends to autonomic ganglion or chromaffin cells
postganglionic neuron
extends from autonomic ganglion, nonmyelinated, extends to effector
hypothalamus regulates:
balance between symapthetic and parasympathetic activity levels
autonomic tone
total activity rate of the ANS, balances the two divisions
sympathetic components of the ANS
preganglionic neurons
autonomic ganglion
sympathetic ganglion
postganglionic neurons
parasympathetic components of the ANS
preganglionic neurons
autonomic ganglions
parasympathetic ganglion
postganglionic neurons
organization of the ANS (generic pathway)
CNS, preganglionic neurons, ganglion/chromaffin,, postganglionic neuron, effector
thoracolumbar division is where
cell bodies of preganglionis neurons are located in SNS (lateral grey horns)
t1-L2
sympathetic trunk (chain) ganglia are located
on either side of the spinal cord
facts about sympathetic trunk (chain) ganglion (
extend from skull base to coccyx
receive axons from thoracolumbar segements
form superior, middle and inferior cervical ganglia
close to spinal cord
sympathetic pregangionic neurons are long or short
short
sympathetic postgangionic neurons are long or short
long
prevertebral ganglia are located
anterior to vertebral column
prevertebral ganglia consist of how many ganglia
5
prevertebral ganglia innervates mostly
organs below the diaphragm
4 options of a preganglionic neuron (pathways to get somewhere)
- same level
- higher or lower
- goes to prevertebral ganglion
- goes to chromaffin cells
option details for preganglionic neuron once it leaves the cord)
- 1. stays at same level
axon exits cord, does a loop through white communicating ramus to sympathetic trunk ganglion, synapses in ganglion and leaves thru grey communicating ramus
option details for preganglionic neuron once it leaves the cord)
- 2. higher or lower
exact same as 1 but when the axon gets to the trunk ganglion, it goes up or down the trunk before exiting via grey communicating rami
(exit cord, white com ramus -> sympathetic trunk ganglion (moves up or down) -> grey com ramus)
option details for preganglionic neuron once it leaves the cord)
- 3. axon synapses in prevertebral ganglion
exits cord, enters symp trunk ganglion via white com ramus, continues thru a splanchnic nerve to a prevertebral ganglion
option details for preganglionic neuron once it leaves the cord)
- 4. axon goes to chromaffin cells
exits cord, goes to trunk ganglia via white com ramus, continues thru splanchnic nerve to chromaffin cells
white communicating ramus
short pathway where axons enter the sympathetic trunk ganglia after exiting the spinal cord
(far track on diagrams)
myelinated axons - hence white
connects spinal nerve to chain ganglia
grey communicating ramus
short pathways where axons in sympathetic trunk ganglia return to the spinal nerve
(close track to SC on diagram)
unmyelinated axons - hence grey
connect ganglia of sympathetic trunk to spinal nerves
in the sympathetic NS which axons are long and short?
long - postganglionic
short - preganglionic
this means that ganglia (being prevertebral or in the trunk) are close to CNS
how many postganglionic neurons can one preganglionic neuron synapse within the SNS
up to 20, supplying many body regions
cervical ganglia innervate:
heart and head
(all glands)
thoracic ganglia innervate:
heart, lungs, skin
(all glands)
hypogastric plexus innervates:
pelvis visceral effectors
preganglionic axons that pass thru the symapthetic trunk without synapsing in it are called?
what options are these part of?
splanchnic nerves
part of options 3 and 4
extend to prevertebral ganglia or chromaffin cells
suprarenal medulla houses
chromaffin cells
chromaffin cells function
secrete hormones into the bloodstream (NE and E)
