The autonomic nervous system Flashcards
What are the divisions of the ANS?
- Sympathetic nervous system
- Parasympathetic nervous system
- Enteric nervous system
What are the general function of the SNS, PNS and ENS?
- SNS: Fight or flight (high energy state)
- PNS: Rest and digest (low energy state)
- SNS: Innervates GI tract and coordinates many reflexes
What is the general structure of autonomic outflow?
- There are usually 2 neurones linking the CNS to peripheral effectors.
- An exception is sympathetic outflow to the adrenal glands.
- Cell bodies of pre-ganglionic neurones are usually in CNS.
- Cell bodies of post-ganglionic neurones are outside the CNS and are usually found in ganglia.
What are the general locations of the sympathetic ganglia?
- Paravertebral sympathetic trunks.
- Prevertebral ganglia (e.g. coeliac ganglia) for splanchnic nerves
What are the general locations of parasympathetic ganglia?
Close to tissues.
What is convergence/divergence?
- Convergence: Multiple pre-synpatic neurones synapse with 1 post-synaptic neurone.
- Divergence: One pre-synaptic neurone synapses with multiple post-synaptic neurones.
What are the spinal levels where the SNS outflow originates?
T1-L2
Where are the cell bodies of pre-ganglionic sympathetic ganglia located?
Intermediolateral nucleus of spinal cord grey matter.
What is the significance of the association of sympathetic ganglia with the spinal levels?
- There is a sympathetic ganglion associated with each spinal level.
- There are fewer sympathetic ganglia compared to spinal levels because some are fused,
What is the structure of the nervous outflow from the spinal cord?
- The ventral roots are where the efferent motor axons leave the spinal cord.
- The dorsal roots are where the afferent motor neurones enter the spinal cord. It is the location of the dorsal root ganglia.
- These 2 roots merge to form one spinal nerve, allowing fibres from both roots to mix.
- The spinal nerve splits in to the ventral and dorsal rami that supply the trunks/limbs and back respectively.
What are the different types of sympathetic synapses?
- Hair follicles, sweat glands and blood vessels in skin: The pre-ganglionic neurone enters the sympathetic ganglion via white rami communicantes and synapses at sympathetic ganglion of same spinal level or different level. The post-ganglionic fibres then leave the sympathetic trunk at the same level or different levels.
- Thoracic organs: The pre-ganglionic neurone enters the sympathetic ganglion via white rami communicantes and synapses at the sympathetic ganglion of the same spinal level. The post-ganglionic neurone then leaves ganglion via visceral nerves without going through grey rami communicantes.
- Abdomen and pelvic organs: The pre-gangionic neurone enters the sympathetic ganglion through white rami communicantes. It leave the ganglion without synapsing and synapse in pre-vertebral ganglion nearer to their targets. These are called the thoracic splanchnic nerves.
- Adrenal medulla: The pre-sympathetic neurone enters the sympathetic ganglion through white rami communicantes. It leaves the ganglion without synapsing and directly synapses with the adrenal medulla.
What are the outflow levels for sympathetic innervation to thoracic organs?
- Middle, inferior cervical ganglia
2. T1-5
What are the outflow levels for the thoracic splanchnic nerves?
- Greater splanchnic: T5-9
- Lesser splanchnic: T10,11
- Least splanchnic: T12
What are the parasympathetic outputs?
- Edinger Westphal nucleus - midbrain (CN III)
- Lacrimal and superior salivary nuclei - medulla (CN VII)
- Inferior salivary nucleus - medulla (CN IX)
- Dorsal motor nucleus - medulla (CN X)
- Pelvic splanchnic nerves - pelvis (S2-4)
What are the ganglia and functions of the Edinger Westphal nucleus?
Ganglia: Ciliary ganglia
Innervation:
- Innervates sphincter pupillae (pupil constriction)
- Innervates ciliaris muscle (accommodation)
