Mod6-Obj3: Sympathetic ad parasympathetic divisions Flashcards
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)
Visceral reflexes
autonomic motor response to stimulus act to preserve homeostasis
e.g.) Baroreceptor or pupillary
Baroreceptor reflex
Monitors blood pressure
If blood pressure rises
-Baroreceptor activated: signals cardiovascular centre in medulla
Response: Increase parasympathetic and decrease sympathetic activity
Result: decreased heart rate and FOC to decrease blood pressure
