7 - Autonomic nervous system Flashcards
What does efferent mean?
- motor fibres
- CNS to PNS
What does afferent mean?
- sensory fibres
- PNS to CNS
What is the somatic nervous system?
- division of motor neurones
- efferent
- voluntary movement
What is the autonomic nervous system?
- division of motor neurones
- efferent
- controls involuntary movements and physiological processes
What is the sympathetic division?
- division of autonomic system
- efferent
- “fight or flight” response
What is the parasympathetic division?
- division of autonomic system
- efferent
- “rest and digest”
Describe autonomic pathways.
- efferent
- 2 neurones that synapse in ganglion
- preganglionic neurones are myelinated
- postganglionic neurones are non-myelinated
Describe the pre- and post-ganglionic neurones in the sympathetic system.
Pre - shorter
Post - longer
Ganglion is closer to the CNS
Describe the pre- and post-ganglionic neurones in the parasympathetic system.
Pre - longer
Post - shorter
Ganglion is closer to target organ
What are the transmitters used in the ANS?
- acetylcholine
- noradrenaline
What effect does ACh have on the body?
- parasympathetic
- excited gut
- slowed heart rate
What are neurones called that release ACh?
Cholinergic fibres
What are neurones called that release noradrenaline?
Adrenergic fibres
What effect does noradrenaline have on the body?
- sympathetic
- decrease in gut activity
- increase in cardiac activity
What makes up the parasympathetic nervous system?
Craniosacral
- cranial nerves (III,VII, IX, X)
- spinal segments S2-S4
What makes up the sympathetic nervous system?
Thoracolumbar
- spinal segments T1-L2 (lateral horn)
Describe the course of the sympathetic pre-ganglionic neurones.
- leave spinal cord via ventral root
- form a spinal nerve
- enter the ganglia of the sympathetic chain (white ramus communicans)
Describe the course of post-ganglionic sympathetic neurones.
- synapse in the ganglia at the same level (exit via grey ramus communicans)
- travel up/down chain to ganglia at different level (exit via grey ramus communicans)
- exit ganglia via splanchnic nerve to prevertebral ganglion (myelinated)
What are the cervical ganglia?
- where pre-ganglionic neurones synapse here on route to the head and neck
- 3 ganglia (superior/middle/inferior)
- form peri-arterial plexuses with vessels in the neck
Where is the superior cervical plexus located?
- C1/C2
- nerves travel along ICA and carotid plexus into head
Where is the middle cervical ganglion located?
C6
Where is the inferior cervical ganglion located?
- C7
- fuses with 1st thoracic ganglion to form stellate ganglion
- superior to 1st rib
What are the branches of the superior cervical ganglion?
- ICA and ECA (forms plexuses)
- cervical spinal nerves (C1-C4, cervical plexus)
- pharynx
- superior cardiac nerves
What are the branches of the middle cervical ganglion?
- middle cervical nerves (C5, C6)
- middle cardiac nerves
What are the branches of the inferior cervical ganglion?
- vertebral artery (forms plexus)
- cervical spinal nerves (C7-T1, C7 and C8 to brachial plexus)
- inferior cardiac nerves
What do the cervical ganglia innervate?
- SYMPATHETIC INNERVATION
- eyes (dilation)
- eyelids
- lacrimal glands
- salivary glands
- sweat glands
- carotid body
What is Horner’s syndrome?
- damage to cervical sympathetic trunk (affects ipsilateral side)
- miosis
- ptosis
- flushed face and anhydrosis
What is miosis?
- constriction of pupil
- parasympathetic sphincter is unopposed due to damage to cervical sympathetic trunk
What is ptosis?
- drooping of superior eyelid
- paralysis of smooth muscle component due to damage to cervical sympathetic trunk
What causes a flushed face and the absence of sweating in Horner’s syndrome?
- damage to cervical sympathetic trunk
- lack of sympathetic constriction to blood vessels and sweat glands
What are splanchnic nerves?
- preganglion nerves that exit the sympathetic chain without synapsing
- synapse at prevertebral ganglia
Where are the prevertebral ganglia located?
- anterior to aorta
- named based on the vessels they are near
What are the prevertebral ganglia?
- celiac
- superior mesenteric
- inferior mesenteric
What is the adrenal medulla?
- located within adrenal gland (superior to kidney)
- surrounded by adrenal cortex
Describe the innervation of the adrenal medulla.
- supplied by sympathetic pre-ganglionic neurones
- synpase with chromaffin cells that release adrenaline and noradrenaline in the blood
Describe the ganglion of the occularmotor nerve.
- CN III
- parasympathetic
- pre-ganglionic nerve travel from nucleus in brainstem to ciliary ganglion
- post-ganglionic neurones travel to innervate ciliary muscle and sphincter pupillae
Describe the ganglion of the facial nerve.
- CN VII
- pre-ganglionic neurones travel from brainstem to pterygopalatine and submandibular ganglia
- pterygopalatine ganglion to lacrimal gland and nasal mucosa
- submandibular ganglion to submandibular gland via chorda tympani
Describe the ganglion of the glossopharyngeal nerve.
- CN IX
- pre-ganglionic neurones travel from brainstem to otic ganglion
- post-ganglionic nerves travel to parotid gland
Where is the ciliary ganglion located?
Between optic nerve and lateral rectus muscle
Where is the pterygopalatine ganglion located?
Within pterygopalatine fossa
Where is the submandibular ganglion located?
Suspended from lingual nerve, close to submandibular gland
Where is the otic ganglion located?
- directly below foramen ovale
- medial to maxillary branch
- posterior to meidal pterygoid
Describe the ganglion of vagus nerve.
- CN X
- no parasympathetic supply within head and neck
- pre-ganglionic neurones travel from dorsal nucleus within carotid sheath to ganglia close to target organ
