Anatomy of the Autonomic Nervous System Flashcards
how are the CNS and PNS related?
they are anatomical
The CNS and PNS are a continuum, they are not sperate or distinct
you can have a neurone who’s cell body is located in the PNS but its axon extends into the CNS.
what is the difference between the afferent and efferent system?
they are directional
Efferent System – Carries impulses from the CNS to effectors in the PNS
Afferent – Carries sensory information from receptors in the PNS to the CNS
what is the difference between the somatic and autonomic NS?
they are functional
Somatic – produces voluntary actions via skeletal muscles
Autonomic – produces involuntary actions via smooth muscle, cardiac muscle and glands.
what part of the NS has meninges?
CNS - meninges (dura, arachnoid, pia)
PNS - no meninges and nerve made up of fascicles (endoneurium, perineurium, epineurium)
what is the structure of a transverse section of the spinal cord?
dorsal horn with dorsal root
in the dorsal root - somatic afferent synapses with CNS cell bodies
ventral horn with ventral root
in the ventral root - somatic efferent cell bodies and axons
at the start of the dorsal and ventral roots you have separate motor and sensory neurones
once the two roots merge, you get mixed nerves (i.e afferent & efferent, motor & sensory)
how do things transfer from the spinal cord (CNS) to the PNS?
horn –> root –> mixed spinal nerve –> dorsal/ ventral ramus
how does the transverse cross section of the spinal cord change as you move down the levels?
lateral horn- found in the thoracic and lumbar regions of the SC (found on the lateral portion of the grey matter
it contains the pre-ganglionic
sympathetic neuronal cell bodies (T1-L2)
in the PNS, nerves called pelvic
splanchnic nerves (parasympathetic) have pre-ganglionic cell bodies which are found in lateral (anterolateral) horn of sacral segments
(S2-4)
why is the lateral horn in the sacral segment sometimes referred to as anterolateral?
it isn’t as well defined in the sacral part causing so its called anterolateral
what does the autonomic NS do?
involuntary control
works continuously
Facilitates ‘fundamental’ life-functions
Maintains homeostasis by regulating CVS, respiratory, digestive, excretory and thermoregulation
Becomes active alongside organogenesis during embryo development
The ANS controls functions of the body by changing the balance of continuous outputs in two ‘opposing’ systems (SympaNS and ParaNS)
what is the autonomic NS divided into?
Divided into Sympathetic, Parasympathetic and enteric NS
how do the para and symp NS work together?
Both para and symp divisions are functionally antagonistic
both maintain homeostasis
what is the difference between ganglion and nuclei
ganglion- collection of neuronal cell bodies in the PNS
nuclei- collection of neuronal cell bodies in the CNS
how are the neurones arranged in the NS?
cell body - in the CNS (brain stem, cranial nerve nuclei, lateral horn of SC)
pre - ganglionic neurone would lead to a synapse which is in the ganglion in the PNS
that attaches to another ganglionic neurone (post- ganglionic fibre) that is connected to the target tissue/ organ
what is the difference between the pre and post ganglionic fibres?
pre - ganglionic:
myelinated
primary neurotransmitter is ACh
(cholinergic fibres)
post - ganglionic:
non- myelinated
depending on whether is symp or para the primary neurotransmitter is either ACh or noradrenaline
(adrenergic fibres)
what does visceral mean?
coming from organs and blood vessels
what do the different afferent fibres do?
- General visceral (coming from organs and BV) afferent (GVA) fibres (not sympathetic or parasympathetic)
send sensory information back to CNS via the dorsal root and horn. - Visceral/autonomic afferent fibres travel in the same way as somatic afferent fibres
- The neuronal cell bodies are located in specific sensory nerve ganglia of cranial nerves or dorsal root ganglia
is pain felt in the viscera?
- viscera are insensitive to cutting, crushing and burning
- excessive tension in smooth muscle and some pathological conditions produce visceral pain
what are dermatomes?
Afferent fibres have a segmental arrangement
they supply cutaneous innervation to a specific region of skin
Dermatome maps map out the region of skin innervated by a particular spinal nerve
There is considerable overlap between cutaneous innervation and spinal segments bc of the distribution of the nerves (can have visceral pain in multiple dermatomes)