Structure of Autonomic Nervous System Flashcards
State the 2 main division of the ANS
Sympathetic
Parasympathetic
Enteric
Branches of the peripheral nervous system
Sensory (afferent)
Motor (efferent)
Function of the enteric nervous system
Self-contained autonomous control system for the gut
(heavily influenced by the ANS - can work on its own)
Describe the somatic motor system
Upper motor neurones which leave the cortex, come down and either in the brain stem or spinal cord synapse with lower motor neurones.
Lower motor neurones then head out into the periphery acting on skeletal muscle.
Describe the visceral motor system
AKA: Autonomic nervous system
(2 neurone system)
Origins of the 1st neurone is in the hypothalamus.
Neurones come out of the hypothalamus, head down and synapse onto a neurone either in the brainstem or spinal cord.
That neurone heads out, doesn’t go all the way to an effector, it goes to a ganglion and synapses.
Post-ganglionic neurone goes to an effector (smooth muscle etc.)
What is a ganglion ?
A collection of nerve cell bodies outwith the CNS
Nucleus
A collection of nerve cell bodies within the CNS
What is the ANS served by ?
A 2 neurone system
- Pre-ganglionic fibres originate from CNS
- Post-ganglionic fibres originate from autonomic ganglia
State pre-ganglionic fibre origins in the :
- Sympathetic
- Parasympathetic
- Thoracolumbar
- Craniosacral
State post-ganglionic fibre origins in the :
- Sympathetic
- Parasympathetic
- Paravertebral Chain/ Prevertebral ganglia
- In or near target origin
Parasympathetic cranial nerves from the brain
What do they innervate ?
Innervate :
- eye
- lacrimal gland
- salivary gland
Vagus nerve innervations
What do they innervate ?
- heart
- lungs
- upper GI tract
Parasympathetic sacral nerves
What do they innervate ?
- Lower GI tract
- Bladder
- Genitalia
Location of Vagus Nerve
Behind thorax
Running behind the lung root and onto the oesophagus.
Neck to splenic flexure of colon
Sympathetic supply
What do they innervate ?
Same as Parasympathetic
Also body wall and limbs
Sympathetic chain
Where does it run to and from ?
Runs form the base of the skull to the base of the coccyx
Describe sympathetic chain
Connections of ganglia (1mm)
Run all the way from the base of the skull down to the bottom end of pelvis
How to get sympathetics from the thorax up to the head and neck ?
Option 2
The neurone :
Comes out of the CNS into the sympathetic chain but don’t synapse.
Ascending, up the connected chain of ganglia to a higher ganglion, synapse in this ganglion and leave back to either a spinal nerve in the neck or a plexus in the neck, travel up into the head to supply things like the eye etc.
Describe how a neurone supplies a spinal nerve at the same segment
Option 1
Come out of the CNS, come into a sympathetic ganglion and synapse at the same level, either return to a spinal nerve or leave the sympathetic chain and go to some viscera.
How to get sympathetics from the thorax downwards ?
Option 3
Neurone leaves from a lower segment into the sympathetic chain, not synapse and descend.
Synapse at the level they are innervating, return to a spinal nerve, travel out to do things in lower limbs.
Option 4
Leave the CNS, enter the sympathetic chain
Don’t synapse
Leave the sympathetic chain as a presynaptic neurone in a thoracic splanchnic nerve.
These head down into the abdomen where they synapse in pre-vertebral ganglia.
These lie on the aorta.
What is the thoracic splanchnic nerve ?
A collection of un-synapsed pre-ganglionic sympathetic neurones.
What supplies abdominal viscera ?
Thoracic Splanchnic Nerves from the thorax
Describe the autonomic nervous reflex
Sensory afferent neurone heads to the CNS, interneurons involved, motor efferent neurone leaves.
Since ANS, 2 neurones in the effector pathway.
Pre-ganglionic –> Postganglionic