T2 L5: Autonomic pathways Flashcards
What is the main autonomic centre?
Hypothalamus
What do descending fibres innervate in the brainstem?
The parasympathetic cranial nerve nuclei and critical autonomic centres in the ventrolateral medulla
What do descending fibres innervate in the spinal cord?
sympathetic and parasympathetic preganglionic neurones in the lateral horns
What structures make up the limbic system?
The amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus
What is the limbic system for?
Responsible for involuntary responses like emotions, blushing, and pallor
Where do the sympathetic components of the autonomic NS originate from?
From the thoracic spinal cord and L1 and L2 (T1-L2)
Where do the parasympathetic components of the autonomic NS originate from?
The brainstem and S2,S3, and S4 of the spinal cord
What type of autonomic circuit does not form a disynaptic pathway?
Sympathetic supply to the adrenal medulla
What is the main neurotransmitter found in autonomic ganglia?
Acetylcholine
What type of receptor does ACh bind to?
Nicotinic
How does ACh work to depolarise neurones?
Through ionotropic ligand-gated binding. It’s a fast process where ACh binds and opens the pore which depolarises the neuron
What is the main neurotransmitter in postganglionic sympathetic neurones?
Noradrenaline
What is the only area in the body that uses ACh in it’s sympathetic neurones?
Sweat glands
How does noradrenaline depolarise neurones?
Through metabotropic G-protein coupled slow depolarisation
Where are alpha-1 receptors found?
On blood vessels
Where are beta-1 receptors found?
On the heart
Where are beta-2 receptors found?
On the bronchi of the lungs
What is the main neurotransmitter within the adrenal medulla?
ACh
On which cells in the adrenal medulla are nicotinic receptors found?
Chromaffin cells
What is atropine used for?
Treat bradycardia, dilate pupils, reduce glandular secretions….
Which is faster, Metabotropic G-protein coupled release or Ionotropic ligand-gated release?
Ionotropic ligand-gated release
What effect does sympathetic NS have abdomino-pelvic viscera?
Inhibits peristalsis and stimulates glucagon
Through which structure do sympathetic preganglionic fibres enter the sympathetic trunk?
Through the white rami communicantes
What are splanchnic nerves?
They don’t synapse in the sympathetic trunk
What is the ratio of preganglionic neurones to postganglionic neurones?
1:20
What are the 2 ways that neurones can leave the sympathetic trunk?
Through the grey rami communicantes back into spinal nerves (periphery) or they can leave via the medial plexus (viscera)
Which parts of the body does cervical ganglia supply?
The head, upper limbs, and the heart
What are the 3 divisions of cervical ganglia?
Super, middle, and inferior
Where is the stellate ganglion?
It’s fused to the inferior cervical and first thoracic ganglia
What is the clinical significance of the stellate ganglia in terms of pain?
Blocking it is treatment for chronic pain
How do postganglionic sympathetic fibres get to the heart?
They piggyback along the common carotid artery towards the heart
How do postganglionic sympathetic fibres get to the head?
They piggyback up the internal/external carotid arteries towards the head
What does the internal carotid plexus supply?
The eyes (dilates pupils and raises eyelids) and the lacrimal gland (inhibits secretions)
What does the external carotid plexus supply?
The submandibular and parotid gland (inhibits secretions)
What causes Horners syndrome and what are the signs?
It’s caused by a disruption of sympathetic supply to the head and includes signs like miosis, ptosis, and anhidrosis
What does Miosis mean?
Excessive constriction of the pupil
What does Ptosis mean?
Drooping of the eyelid
What does Anhidrosis mean?
Lack of sweating
What can cause Horner’s syndrome?
Lesions within the brainstem/cervical spinal cord Eg. with Multiple sclerosis
What parts of the body do the thoracic ganglia supply?
Thorax, heart, lungs, and abdominal viscera
What are the 3 divisions of thoracic splanchnic nerves?
Greater, lesser, and least
What do the lumbar ganglia supply?
The abdominal viscera and lower limbs
What does sacral ganglia supply?
The pelvis and lower limbs
How do preganglionic lumbar sympathetic fibres exit?
Lumbar splanchnic nerves go to abdomen and synapse in the prevertebral ganglia
Where in the body does parasympathetic nervous supply have an effect of blood vessels?
In male erectile tissue
What nucleus does the oculomotor nerve (CN3) originate from?
The Edinger-Westphal nucleus in the midbrain
What nucleus does the facial nerve (CN7) originate from?
The superior salivatory nucleus in the pons
What nucleus does the Glossopharyngeal nerve (CN9) originate from?
The inferior salivatary nucleus found in the pons
What nucleus does the Vagus nerve (CN10) originate from?
From the nuclues ambiguous and the dorsal motor nucleus in the medulla
How do cranial parasympathetic preganglionic axons get into the cranium?
They pass through cranial nerves to ganglia
Which ganglia provides information to the lacrimal gland?
The Pterygopalatine ganglia
Which ganglia provides information to the parotid gland?
The Otic ganglion
Which ganglion provides information for the submandibular gland?
The Submandibular ganglion
Which ganglion provides information for the sphincter pupillae to contract pupils?
The Ciliary ganglion
What organs does the vagus nerve pass on?
The heart, lungs, and abdominal viscera
What functions do sacral parasympathetic nerves provide?
- Contraction of the bladder wall for urination and inhibition of the bladder sphincter
- Inhibition of the rectal sphincter to allow for defecation
- vasodilation in erectile tissues
What effect does parasympathetic nervous supply have on male erectile tissues?
Erection
What effect does sympathetic nervous supply have on male erectile tissues?
Ejaculation
What are the 2 complexes in the enteric nervous system?
Auerbach’s and Meissner’s
Where is the Auerbach’s plexus and what does it do?
Found between the longitudinal and circular layer of muscle in the intestines. It regulates muscle contraction
Where is the Meissner’s plexus and what does it do?
Found between the circular muscle and mucosa layer. It regulates glandular contraction
Which type of nervous system can be described as truly autonomic and why?
The enteric nervous system because you could remove it and it would still contract and secrete
What do afferent pathways of the autonomic nervous system do?
They convey sensory information to autonomic centres via dorsal roots into the spinal cord and via CN9 and CN10 into the brainstem
