Basic Sciences - Autonomic Nervous System Physiology Flashcards
Global constituents of autonomic nervous system (ANS)
Afferent pathways
Efferent pathways
Role of afferent pathways in ANS
Transmit sensory information from visceral structures
Also chemical and mechanical data from chemo- and baro- receptors
Role of efferent pathways in ANS
Control cardiac muscle, smooth muscle and glands
Central components of the ANS
Midbrain
Medulla
Limbic system
Hypothalamus
Brainstem
Spinal cord
Limbic system
Emotion
Two main divisions of the ANS
Sympathetic nervous system (SNS)
Parasympathetic nervous system (PNS)
Often antagonistic
Parts of the body supplied by SNS
All parts of body including trunk and limbs
Parts of the body supplied by PNS
Viscera only
(except adrenal glands and gonads - only SNS supply)
Efferent pathways of both SNS and PNS structure
Preganglionic neurones
Intermediary ganglion
Postganglionic neurones
Preganglionic neurones features
Cell bodies in brain or lateral horns of spinal cord
Myelinated axons
Slow conducting B fibres
Number of postganglionic neurones innervated by each preganglionic neurone
8 to 9 postganglionic cells
Produces diffuse responses characteristic of ANS
Postganglionic neurones features
Unmyelinated
C fibres
Outflow of sympathetic efferent neurones
Thoracolumbar outflow
T1 - L2
Methods of preganglionic neurone axon termination
1) Most synapse in paravertebral sympathetic chain
2) Some pass through sympathetic chain via splanchnic nerves to synapse in a peripheral autonomic ganglion in abdo / pelvis
3) Few preganglionic fibres synapse directly with chromaffin cells in medulla of adrenal gland
Examples of peripheral autonomic ganglions in the abdomen or pelvis
Coeliac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglia
Location of preganglionic cell bodies in SNS
Lateral horns of spinal cord levels T1 - L2
Outflow of efferents in PNS
Cranio-sacral outflow from:
- Cranial nerves 3, 7, 9 and 10
- Spinal roots S2-4
Location of preganglionic cell bodies of PNS
Cranial nerve nuclei or lateral horns of sacral spinal cord
Parasympathetic ganglia sites from vagus an sacral efferents where preganglionic neurones synapse
Diffusely located in the walls of the viscera they supply
Eg. heart, gut, lungs