Structure of the autonomic nervous system Flashcards
Describe the divisions of the nervous system to the sympathetic and parasympathetic nervous system
CNS // PNS PNS –> Motor (efferent) Somatic motor // Visceral motor visceral motor –> Sympathetic // parasympathetic
Describe the route of motor neurones
- Starts in the primary motor cortex, pre-central gyrus of the brain
- Travels down and synapses in the brain stem or the spinal cord onto somatic motor nuclei
- Heads out into the periphery
- Acts on skeletal muscle
What is a ganglion?
A collection of nerve cell bodies/ soma outside of the central nervous system
Where do Pre-ganglionic neurones originate from?
The CNS
Where do post ganglionic neurones originate from?
Autonomic fibres
Describe the outflow of the parasympathetic system
- Craniosacral outflow
- Neurones leave from the brain stem and the sacral section of the spinal cord
- Synapse on ganglia near or in target organs in the periphery
- Long pre-ganglionic neurones
- Short post-ganglionic neurones
Describe the outflow of the sympathetic nervous system
- Thoracocolumbar outflow
- Thoracic and upper lumbar sections
- Short pre-ganglionic neurones
- Long post-ganglionic neurones
- Synapse in the paravertebral chain
Where does each sympathetic trunk extend to?
- Superiorly: The atlas
- Inferiorly: they fuse together in the ganglion impair, opposite the coccyx
What are the 4 options that a sympathetic ganglion has when it leaves the CNS?
1) Emerges from CNS, enters the sympathetic chain and then ascends to a higher level e.g. the neck, then synapses onto a post ganglionic neurone
2) Emerges from the CNS, enters the sympathetic chain and stays at the same level, synapses and then passes out with the spinal nerve and goes on to innervated the body wall or organ
3) Emerges from the CNS, enters the sympathetic chain and descends to a lower level, synapses and then goes on to innervate structures in the lower limb
4) Emerges from the CNS and continues as a pregnaglionic neurone and then synapses in a preaortic or prevertebral ganglion - splanchnic nerve
Describe the route and innervation of the Vagus nerve
- From the Brain
- Down the neck
- Runs either side of the oesophagus
- Forms branches and a plexus
- When it enters the abdome, it becomes more diffuse
- Innervates the heart, lungs, neck and upper GI tract
What divison of the visceral motor system innervates the body wall?
Sympathetic only
What is contained in the Grey Rami Communicans?
Post Ganglionic neurones
What is contained in the white rami communicans?
Preganglionic neurones
Desrcibe the route of neurones regarding the rami communicans
White –> Ganglion –> Grey
Describe the autonomic motor reflex
- Spinal cord processing
- Unconscious feedback loop
Describe the feeling of visceral pain
- stretch
- Spasm
- Ischaemia
What is the referred pain of a heart attack?
- Left arm
- Jaw
Describe the mechanism of referred pain (using the example of a heart attack)
- Visceral afferent neurones from the heart come into the spinal cord
- The neurones synapse at the same place as somatic afferent neurones in the arm
- The signals from the heart are interpreted as somatic pain from the arm
What actions are associated with the parasympathetic nervous system
Rest and digest
What actions are associated with the sympathetic nervous system?
Fight or flight
What is the effect of the parasympathtic nervous system on the heart?
Slows it down
What is the effect of the parasympathtic nervous system on the Digestive tract?
Increases secretions and motility
What is the effect of the parasympathtic nervous system on the lungs?
Bronchoconstriction
What is the effect of the parasympathtic nervous system on the Urinary bladder?
Release of urine
What is the effect of the parasympathtic nervous system on the Pupil of the eye?
Constricts the pupil
What is the effect of the parasympathtic nervous system on the male sexual organs?
Erection
What is the effect of the parasympathtic nervous system on the blood vessels?
No effect (mostly)
What is the effect of the parasympathtic nervous system on the salivary glands?
Increases secretion
What is the effect of the parasympathtic nervous system on the sweat glands?
No effect
What is the effect of the parasympathtic nervous system on the liver?
no effect
What is the effect of the parasympathtic nervous system on the Pilomotor?
No effect
What is the effect of the sympathetic nervous system on the Heart
Increases the heart rate and the force of contraction
What is the effect of the sympathetic nervous system on the Digestive tract?
Shuts down the system so that blood and energy can be sent elsewhere
Increases motility and secretions
What is the effect of the sympathetic nervous system on the Lungs
Bronchodilaiton
What is the effect of the sympathetic nervous system on the Urinary bladder?
Urinary retention
What is the effect of the sympathetic nervous system on the pupil of the eye
Dilates it
What is the effect of the sympathetic nervous system on the male sexual organs?
Ejaculation
What is the effect of the sympathetic nervous system on the blood vessels
Constriction (mostly)
What is the effect of the sympathetic nervous system on the salivary glands?
Increases secretion
What is the effect of the sympathetic nervous system on the sweat glands?
Increases secretion
What is the effect of the sympathetic nervous system on the liver?
Glycogenolyis and gluconeogenesis
What is the effect of the sympathetic nervous system on the pilomotor?
Piloerection
What innervates the pupillary dilator muscle and what action does it bring about?
- Sympathetic nervous system
- Mydriasis
- When the muscle constricts, it causes dilation of the pupil
What is the innervation of the pupillary constrictor muscle and what action does it carry out?
- Parasympathetic
- Miosis
- When it contracts it constricts the pupil
Describe, refering to the nervous system, what happens when the bladder is filling
- Sympathtic control predominates
- Relaxation of the detrusor muscle
- Contraction of the internal sphincter muscle
Describe, refering to the nervous system what happens when the bladder is full
- Parasympathtic control predominates
- Contraction of the detrusor muscle
- Relaxation f the internal spincter muscle
What neurotransmitter and receptors are present in the pre-ganglionic neurones in the parasympathetic nervous system?
- Acetylcholine
- nicotinic receptors
What neurotransmitter and receptor are present in the postganglionic neurones in the parasympathetic nervous system?
- Acetylcholine
- Muscarinic receptors
What neurotransmitter is released in the sympathetic nervous system?
MOST:
• Noradrenaline
SOME:
• Acetylcholine (e.g. sweatgland)
