22 - CNS, PNS and ANS Flashcards
What are the two parts of the CNS?
- Brain
- Spinal Cord
What are the two divisions of the PNS?
- Somatic
- Autonomic
What are the three divisions of the ANS?
- Sympathetic
- Parasympathetic
- Enteric
How is grey and white matter distributed in the spinal cord?
- Inner grey matter (butterfly shape)
- Outer white matter
How many:
- Cervical vertebrae?
- Thoracic vertebrae?
- Lumbar vertebrae?
- Cervical vertebrae = 7
- Thoracic vertebrae = 12
- Lumbar vertebrae = 5
At what level of the spine does the spinal cord end and continue as nerve fibres?
How is this useful clinically?
L1-L2
Allows you to do a lumbar puncture without damaging the spinal cord
The neurone at the dorsal side of the spinal cord is ……………
Sensory
The neurone at the ventral side of the spinal cord is ……………
Motor
The dorsal and ventral nerve roots come together to form a mixed ………… nerve
Spinal
How many vertebrae are fused to form the sacrum? What lies beneath the sacrum?
5 vertebrae form the sacrum
Coccyx
Spinal nerves innervate specific areas of skin and muscle, which can be mapped. What is this called for:
- skin?
- muscle?
- Skin - dermatome
- Muscle - myotome
What is a ganglion?
Collection of cell bodies in the PNS (e.g. dorsal root ganglion)
The somatic system has ……. motor neurone(s) from spinal cord to effector, the autonomic system has ……. motor neurone(s)
One
Two (pre and post ganglionic)
Where is the synapse between pre- and post-ganglionic neurones found in the CNS?
The autonomic ganglion
The pre-ganglionic neurone cell body is in the ………
The post-ganglionic neurone cell body is in the ………
CNS
PNS (autonomic ganglion)
The sympathetic system has a ……… pre-ganglionic neurone and a ………. post-ganglionic neurone
Short, long
The parasympathetic system has a ……… pre-ganglionic neurone and a ………. post-ganglionic neurone
Long, short
In the sympathetic system, the ganglia containing post-ganglionic cell bodies lies within a structure called ….
The sympathetic chain (paravertebral chain)
Where are the post-ganglionic cell bodies in the parasympathetic system?
Normally a ganglion in the wall of the target organ, as the pre-ganglionic fibres go almost all the way to the target.
Which segments of the spinal cord contain the sympathetic ANS?
Lateral horn in T1-L2 segments
Which segments of the spinal cord contain the parasympathetic ANS?
S2-S4 cord segments (structure homologous to lateral horn) and brainstem
What is the ramus communicans?
- Communicating branch
- Connects the sympathetic ganglion to the spinal nerve
What is the difference between the white and grey ramus communicans?
White (myelinated)
Grey (unmyelinated)
There are 3 routes for sympathetic fibres to reach the skin. What are they?
- Supply T1-L2 dermatomes by leaving at the level of entry
- Supply above T1 by ascending the sympathetic chain before synapsing, post-ganglionic fibres follow the path of blood vessels
- Supply below L2 by descending the sympathetic chain before synapsing, post-ganglionic fibres join the spinal nerves at L3 and below
How do sympathetic fibres reach the abdominal viscera?
- Pre- ganglionic neurones traverse the chain (i.e. do not synapse in the sympathetic chain)
- Instead synapse in a pre-aortic ganglion
- Post-ganglionic fibres get to target organs along blood vessels
What nerve is the main source of pre-ganglionic parasympathetic input to the thoracic and abdominal viscera?
Vagus nerve
What are the 4 specialised parasympathetic ganglia in the head (cranial)?
- Ciliary ganglion - pre-ganglionics from oculomotor nerve to eye
- Pterygopalatine ganglion - pre-ganglionics from facial nerve to lacrimal gland
- Submandibular ganglion - pre-ganglionics from facial nerve to submandibular and sublingual glands
- Otic ganglion - pre-ganglionics from glossopharyngeal nerve to parotid gland
