19 - Organisation of nervous system Flashcards
How is the nervous system broken down?
- Enteric (autonomic): Nervous system within the wall of the gut
- CNS: Processing
What are the main differences between the sympathetic and parasympathetic nervous system?
Sympathetic has chain
What is the difference between the somatic and autonomic nervous system?
Somatic is voluntary and uses one motor neurone
Autonomic is involuntary and uses two neurones between CNS and target organ
What is a ganglion?
A collection of cell bodies in the PNS
What is the spinal nerve?
When the dorsal and ventral root coalesce
What is the difference betweent the dorsal and ventral root?
Dorsal is purely sensory
Ventral is purely motor
Draw the cross section through a spinal cord.
How many spinal cord segments are there?
30-32, therefore there are 30-32 pairs of spinal nerve pairs
How do the dorsal and ventral roots plug into the spinal cord?
- Multiple times, has rootlets
What is a dermatome?
An area of skin supplies by a single spinal nerve
What is the monosynaptic reflex arc?
What are sensory and motor neurones?
Sensory - carry impulses towards CNS
Motor - carry impulses away from the CNS
Why can’t we normally see myelin?
Xyulene and toluene strip the lipid away, can only see with staining with metals
Where are the cell bodies of sensory neurones?
In the dorsal root of spinal nerves either in spinal or cerebral (head nerve) ganglia
Where is the synapse between the two motor neurones in the autonomic system?
- Autonomic ganglion (sympathetic)
- Ganglion near organs (parasympathetic)
Where are the cell bodies of the pre and post gaglionic neurones found?
Pre - CNS
Post - Autonomic ganglion (sympathetic), Walls of organs (parasympathetic)
What is the difference between the pre and post ganglionic neurones?
- Pre myelinated
- Post unmyelinated
- Cell bodies in different areas
What is the sympathetic chain?
Chain on the left and right of the spinal chord containing post-ganglion cell bodies
Where does the post ganglionic neurone sit in the parasympathetic nervous system?
- Close to or in the wall of an organ
Where are autonomic preganglionic neurone cell bodies found in the CNS?
- Parasympathetic: Brain stem (head and neck) and S2-S4 regions
- Sympathetic: From lateral horn in T1-L2
What is the lateral horn?
Found from T1-L2
Contain sympathetic pre-ganglionic neurones
Draw a picture to show where the pre-synaptic ganglion comes from in sympathetic and parasympathetic.
S - LHS
PS - RHS
In the sympathetic nervous system how does an electrical signal get from the CNS to the effector?
Pre ganglionic originates in LH, travels down VH, through VR as motory and into sympathetic ganglion where it meets post ganglionic.
Signal goes back into spinal nerve through grey ramus branch as unmyelinated
In the parasympathetic nervous system how do the electrical signals get from the CNS to the effector?
- Originate in same area of sacral chord
- Travel through VH, VR, spina nerve, to ganglion near organs
- This is because pre-ganglionic are longer in parasympathetic
How does the sympathetic nervous system get to the head and neck if only spans T1-T2?
- Ascend the sympathetic chain and then synapse
In the sympathetic nervous system what three routes can post-ganglionic neurones take to get to the skin?
- Synapse at level of entry (T1-L2) (post-ganglionics get to targets via spinal nerve)
- Ascend the chain and then synapse (post-ganglionics get to targets via walls of blood vessels, supplies head and neck)
- Desend the chain and synapse (post ganglions get to targets via spinal nerve below L3)
In the sympathetic nervous system what ways can pre-ganglionics take to get to the gut?
- Traverse the chain, dont synapse in it, go to pre-aortic ganglion where they synapse
- Ganglia sat in aortic blood vessels supplying the gut
- Post ganglions get to target via blood vessels
What are splachnic nerves?
Nerves that arise from the sympathetic chain and supply the gut with sympathetic pre-ganglionic supply
Apart from pre-ganglions and post ganglions, what else line sympathetics destined for the gut?
- Sensory fibres that relay pain from viscera back to CNS
What are the ganglia called that supply the viscera and the penis?
- Not named
What are the ganglia called that supply the head?
Parasympathetic
- Ciliary ganglion: pre from oculomotor nerve and post to eye pupil
- Pterygopalatine ganglion: pre from facial nerve and post to lacrimal gland
- Submandibular ganglion: pre from facial nerve and post to submandibular and sublingual salivary glands
- Otic ganglion: pre from glossopharyngeal nerve and post to parotid gland
What are the cranial nerves?
Nerves that come from the brain stem. Pre-ganglionic nerves go through this nerve
How does the CNS feel pain from the abdomen?
Sensory fibres travel along sympathetics destined for the abdomen so they can relay pain back to the CNS
