Nervous system and pain Flashcards
Which branches of body structures need innervation?
Somatic (skin, bones, parietal membranes), visceral/splanchnic (organs), branchial arches (head and neck)
Which motor neurons innervate the different branches of structures?
Somatic - spinal nerves (segmental and non); Visceral - Autonomic nervous system (sympathetic T1-L2 and parasymp. in certain cranial nerves); branchial arches - cranial nerves
Which sensory neurons innervate the different branches of structures?
Somatic - spinal nerves (segmental and non), sharp localized pain; Visceral - Autonomic nervous system (visceral afferents), respond to stretch and ischemia, dull delocalized pain; branchial arches - cranial nerves
Know the spreadsheet on slide 1
Spreadsheet
Where do different neurons reside in spinal cord?
Motor - ventral horn; sensory - dorsal horn; sympathetic - lateral horn (where applicable)
Spinal nerve definition
Union of the dorsal root and ventral root. Arise from spinal cord, 31 pairs.
Dorsal root
Sensory, combo from the dorsal and ventral rami sensory neurons.
Dorsal ramus
Splits off spinal root. All segmental. Contain sensory and motor fibers, and sympathetic between T1-L2/3
Ventral ramus
Same as dorsal, except only T1 to T2 are segmental.
Nerve plexuses
Formed by fusion of central primary rami that are non segmental
What do spinal nerves innervate?
Somatic structures (body wall, extremities) structures: skin, skeletal muscle, bone, parietal membranes; then become cutaneous (more superficial) to supply dermatomes
Why do spinal nerves have sympathetic fibres?
Sympathetic needed for smooth muscles in blood vessels, sweat glands,
Dermatome
band of skin with its own sensory innervation
Draw a picture of a spinal nerve
Picture
Draw diagram of the branches of the nervous system
Diagram
Fibres used for sensory, and sympathetic and parasympathetic motor branches
Sensory - visceral afferent; sympathetic - thoracolumbar outflow; parasympathetic - craniosacral
Somatic motor system
Single neuron goes from CNS to muscle
Autonomic motor system
2 neuron system. Preganglionic neuron leaves CNS, then synapses in autonomic ganglion, then postganglionic neuron goes to targets
Sympathetic nervous system neurons
Preganglionic neuron is short (Ach), post gang. is long (Norepinephrine) or can be short and then transmit via blood vessel to target (Epi and norepi)
Parasympathetic nervous system neurons
Preganglionic neuron is long (Ach), post gang. is short (Ach)
Draw diagrams to compare sympathetic and parasympathetic pathways
Two things.
What options do preganglionic sympathetic neurons get to different targets?
Start in T1-L2/3, go enter white ramus communicans then paravertebral sympathetic chains, then there are 5 options.
1
Go in white, then come out grey rams communicans then goes out spinal nerves at same level.
2
Synapses at same level, then goes up the paravertebral sympathetic chains then exit in grey ramus into spinal nerve at another level
3
Synapses at same level, then goes up the paravertebral sympathetic chains then exit in direct branch to thoracic organs (from T1 to T5)
4
Preganglionic neuron doesn’t synapse at own level, but synapse s in superior cervical ganglion (SCG) then goes to head and neck. All head and neck from T1-T5.
5
Goes through the chain along splanchnic nerve to prevertebral ganglia along blood vessel (at base of arteries), synapses, then supplies sympathetic fibres to abdomen
Outline pathways of the 5 options
Crazy diagram with 5 options
How do visceral afferent pain fibres return from abdomen and thorax to CNS?
Return along splanchnic nerves, enter the paracertenral sympathetic chain, leave the chain and enter spinal nerve, cell body is in dorsal root ganglion, then enter spinal cord and go to the cortex of brain.
Another name for T1-L2/3
Intermediolateral cell column (IML). This is where the pre-ganglionic sympathetic neurons come from, then postganglionic use the sympathetic chain to access all extremities
Parasympathetic nervous system summary
Leave brain from cranial nerves III, VII, IX and X, and sacral nerves II, III, IV
Types of pain
DIRECT (cutaneous or superficial pain) or REFERRED (indirect, deep pain)
Types of referred pain
Somatic - due to embryological displacement or projection. Visceral pain is always referred b/c brain doesn’t have visceral map, always misinterpreted
Direct pain
Sharp, easily localized. Carried by spinal nerves which respond to all stimuli. Perceived as arising directly from the injured site
Referred pain
From injured structure but perceived as arising from somewhere else, usually dermatome supplied by same spinal segments as the injured structure .
Describe somatic referred pain and reasons for it
Spinal nerves, sharp and easily localized. Referred for 2 reasons: 1. Embryological displacement (eg. diaphragm is supplied by C3,4,5 - but referred pain is felt in shoulder because same nerves). 2. Anytime you injure a nerve anywhere along its length, pain is projected or referred to the end of that nerve (eg. funny bone [ulnar nerve], prolapsed disc (sciatica), sinusitis, phantom pain)
Describe visceral referred pain and reasons for it
Carried by visceral nerves, which respond to stretch, ischemia, chemoreceptors. Dull and delocalized. Brain perceives pain from somatic structures supplied by same spinal cord levels
How would you differentiate b/w appendicitis and cholecystitis in a pregnant woman?
The initial pain will be referred lower in appendicitis. The acute somatic pain will be in the same place.
