Motor neurons of the ANS
Both divisions serve same organs
- Site of exit from CNS
- Relative lengths of axons
- Location of ganglia
Motor neurons of the ANS: Chain of 2 peripheral neurons
- ) CNS to effector
- ) Preganglionic neuron (thin and lightly myelinated axon)
- Postganglionic neuron (ery thin and non-myelinated axon)
Motor neurons of the ANS: Autonomic ganglia
Contain cell bodies of postganglionic neurons
- Site of synapse between pre and postganglionic neurons
- Located near spinal cord or target organ
- NT released from preganglionic axon (ACh)
Motor neurons of the ANS: Autonomic ganglia
Contain cell bodies of postganglionic neurons
- Site of synapse between pre and postganglionic neurons
- Located near spinal cord or target organ
- NT released from preganglionic axon (ACh)
Parasympathetic division
Craniosacral division
-Preganglionic neurons arise from opposite ends of CNS
+Brain stem
+Sacral region of spinal cord (S2-S4)
-Ganglia located close to or within target organ
Parasympathetic division (Preganglionic fibres)
Long, myelinated
- Synapse with postganglionic neurons
- Release ACh)
Parasympathetic division (Postganglionic fibres)
Short, unmyelinated
- Synapse with effector/target organ
- Release ACh
Parasympathetic: Cranial pathway
Preganglionic axons leave gray matter nuclei of brain stem via cranial nerves
Cranial pathway: CNIII
Oculomotor nerve
-Smooth muscle of the eye
Cranial pathway: CNVII
Facial nerve
-Salivary, nasal and lacrimal glands
Cranial pathway: CNIX
Glossopharyngeal nerve
-Salivary gland
Cranial pathway: CNX
Vagus nerve
-Neck, thoracic and abdominal visceral organs
Parasympathetic: Sacral pathway
Preganglionic neurons
- Lateral gray horns
- Axon exits ventral root of spinal nerves S2-S4
Sacral pathway: Postganglionic axon innervates
Pelvic organs (bladder, reproductive) -Distal portion of large intestine
Sympathetic division: Thoracolumbar division
All preganglionic fibres arise from neurons in spinal cord segments T1-L2
-Ganglia located close to spinal cord
Sympathetic division (Preganglionic fibres)
Long, myelinated
- Synapse with postganglionic neurons
- Release ACh)
Sympathetic (Postganglionic fibres)
Long, unmyelinated
- Synapse with effector/target organ
- Release NA
Sympathetic trunk
Chain of 23 sympathetic ganglia and fibres runnin from one ganglion to another
- Flanks both sides of the vertebral column (prevertebral ganglia)
- Extends from neck to pelvis
Sympathetic pathways:
segments T1-T4
Segments T1-T4 innervate the head
-Skin, blood vessels, pupil, nasal & salivary glands, heart
Sympathetic pathways:
segments T4-T6
Segments T4-T6 innervate the thorax
-Heart and lungs
Sympathetic pathways:
segments T5-L2
segments T5-L2 innervates the abdominopelvic organs
Sympathetic pathways:
segments T5-L2
segments T5-L2 innervates the abdominopelvic organs
Sympathetic pathways: The adrenal medulla
Sympathetic preganglionic fibres
- Synapse with adrenal medullary cells
- Release ACh (stimulates adrenal medullary cells to secrete hormones)
- Release NA and A (move through vascular system, to enhance and prolong sympathetic response)
Sympathetic effects are widespread
Single preganglionic neuron can synapse with multiple postganglionic neurons (activate multiple effectors)
