Nerves of the Thorax Flashcards
What are the 2 main divisions of the nervous system?

Central Nervous System Peripheral Nervous System
What can the PNS be divided into?
- Somatic Nervous System 2. Autonomic Nervous System
What is the somatic NS?
- Voluntary - Controls external actions of skin and muscles (skeletal muscles) - Has both sensory and motor fibres
What is the autonomic NS?
- Involuntary - Innervating organs/viscera –> internal activities - Has parasympathetic (calming) and sympathetic (arousing) elements - Has both sensory and motor fibres
What are afferent fibres?
Sensory –> arriving at CNS back from body
What are efferent fibres?
Motor –> leaving CNS to body
What is effect of sympathetic motor fibres on heart?
Make it contract quicker and with more force
What is effect of parasympathetic motor fibres on heart?
Make it contract slower and with less force
What are the sensory fibres in the sympathetic system?
Pain fibres (go back to CNS)
What are the sensory fibres in the parasympathetic system?
Tell us about general condition of viscera (e.g. how full blood vessels are, how full/empty stomach is)
What is the spinal cord enclosed within?
The bony vertebral column
How many segments is the spinal cord divided into?
31 segments
What does each segment of the spinal cord give rise to?
A pair of spinal nerves (emerging from spinal cord): - 8 pairs of cervical spinal nerves - 12 pairs of thoracic spinal nerves - 5 pairs of lumbar spinal nerves - 5 pairs of sacral spinal nerves - 1 pair of coccygeal spinal nerves

Where do intercostal nerves arise from?
Thoracic spinal nerves
What do nerves contain?
Both motor (efferent) and sensory (afferent_ fibres within it
Segmental spinal nerve: What emerges from spinal cord?

A set of rootlets: - Dorsal rootlets - Ventral rootlets These project out laterally
What do dorsal rootlets contain?
Sensory (afferent) fibres
What do ventral rootlets contain?
Motor (efferent) fibres
What happens to these dorsal and ventral rootlets?
They come together to become a mixed spinal nerve (contains motor and sensory information)

What then happens to this mixed spinal nerve?
Has branches going towards dorsal and ventral aspects –> ventral and dorsal ramus
What is the ventral ramus?
Anterior division of a spinal nerve
What is the dorsal ramus?
Posterior division of a spinal nerve
What is a ganglion?
Cell body or nucleus outside of CNS
Autonomic (parasympathetic and parasympathetic) efferents. Describe neurne pathway:
2 neurone pathway:
- 1st neurone –> preganglionic neurone (cell body in CNS)
Leaves CNS and synapse with another neurone (cell body outside CNS –> ganglion)
- 2nd neurone –> postganglionic neurone







