what is the purpose of the autonomic nervous system?
- acts upon…
the ANS control the internal enviroment, maintaining homeostasis, acting on:
- Heart (cardiac muscle): rate and force of contraction
- smooth muscle: organs, blood vessels, piloerector
- Gland secretion
what is the difference between somatic and visceral efferents?
- visceral is autonomous and involuntary
- visceral pathways contian at least 2 neurons between CNS and target
- visceral pathways may be inhibitory
how is the VNS divided?
VNS»_space;>
- Visceral afferent
- Visceral efferent
What does visceral afferents supply?
visceral afferent is sensory and recieves information from the core only
how is the visceral efferent of the visceral nervous system divided? (what is the other name for visceral efferent system)
visceral efferent (motor)»_space;> ANS
1. sympathetic (to core and periphery)
2. parasympathetic (to core only)
3 (metasympathetic)
what is the difference between pre and post-ganglionic neurons?
pre-ganglions neurons are those projecting from the CNS and their axons are finely myelinated on exit of the CNS.
post-ganglionic neurons are those projecting from peripheral ganglia heading towards their target and their axons are unmyelinated.
what are the divisions of the ANS based on?
- localisation of ganglia
- neurotransmitters of the visceromotor ganglia
- function - response on their activation
what is the difference between the ANS divisions:
- localisation of ganglia?
- sympathetic ganglia are found in the paravertebral chain and pre-vertebral plexus (close to CNS)
- parasympathetic and metasympathtic ganglia are found close or in its wall of the target being innervated.
what is the difference in divisions of VNS?
- neurotransmitters
- visceral afferents, pre and post use ACh
- parasympathetic visceral efferents (craniosacral):
- preganglionic - ACh
- postganglionic - ACh - sympathetic visceral efferents (thoracolumbar):
- preganglionic - ACh
- postganglionic - NE
+ exception with sympathetic: innervation of adrenal medulla chromaffin cells, use ACh to stimulate release of NE and E (epinephrine)
what are the locations of CNS neurons to the ANS divisions?
- parasympathetic: craniosacral
- cranial: CN III, VII, IX, X
- sacral: S2-S4
- sympathetic: thoracolumbar
- thoracolumbar: T1-L2
most organs have both ANS divisions, usually work as antagonists. what are the organs with only one ANS division innervation?
parasympathetic only: lacrimal glands
sympathetic only: adrenal medulla,
arterioles of Skeletal muscle
skin, viscera and kidneys
what are the pathways of sympathetic outflow?
from T1-L2 preganglionic neurons»_space; ganglia»_space; target
+ ganglia
- some preganglionic neurons synapse on closest ganglion (thoracic/upper lumbar) - some preganglionic ascend or descend in the paravertebral chain and synapse in the cervical or lumbosacral ganglia - some preganglionic neurons cross the paravertebral chain to synapse on the pre-aortic ganglia : splanchnic nerves
