S4L1 - Autonomic Innervation of the Cardiovascular System Flashcards
What effect does the sympathetic nervous system have?
Raises the heart rate Increases force of contraction Constrics most blood vessels Slows GI transit Constricts sphincters Bronchodilates Increases sweating Dilates the pupils
What effects does the parasympathetic nervous system have?
Slows heart rate (no effect on force of contraction) Relaxes blood vessels Speeds up GI transit Relaxes sphincters Increases salivation Bronchoconstricts Contracts pupils
Where does the sympathetic chain exit the spinal column?
With spinal nerves T1 to L2 (nowhere else).
The sympathetic chain communicate with spinal nerves via rami communicans. Describe the dorsal root ganglion and grey and white rami communicans.
The dorsal root ganglion contains cell bodies of sensory neurons.
Grey rami communicans are only seen before T1 or after L2 and are post-ganglionic fibres, which pass back into the spinal nerve.
White rami communicans are seen between T1 and L2 only. They are pre-ganglionic fibres, which pass into the sympathetic chain.
Describe the sympathetic supply to the head and why a spinal cord injury to T1 cord level can affect this.
Pre-ganglionic fibres origionate in the hypothalamus.
They then descend to T1 and synapse with a pre-ganglionic neuron in the lateral horn.
It then exits the cord with the T1 spinal nerve and travels to the sympathetic chain.
It then runs up the chain to the cervical ganglia and synapses with the post-ganglionic fibre.
It then enters the head as a plexus around the internal carotid artery and supplys the face via the external carotid artery
The cervical cardiac (splanchnic) nerves origionate in the neck - what are the three sympathetic chain ganglia in the neck?
- Superior cervical: C1-4 (near base of skull)
- Middle cervical: C5-6
- Stellate: C7-T1 (near lung apex)
What syndrome occurs with loss of sympathetic supply to the head and what are its symptoms? What can cause this?
Horner's syndrome: Pupil constriction (miosis); vasodilation; ptosis; lack of sweating (anhydrosis).
Causes: pancoast tumour; tumour of skull base; lyphadenopathy; latrogenic; trauma.
Adrenalin provides a mechanism for reaching cells with no sympathetic innervation. What cells of the adrenal medulla release adrenaline (95%) into the blood?
Chromaffin cells.
Parasympathetic outflow from the CNS is via four cranial nerves and three spinal nerves. What are they, and where do the parasympathetic nuclei sit in the brain?
The parasympathetic nuclei sin in the brainstem.
Cranial nerves: III (oculomotor); VII (facial); IX (glossopharyngeal) and X (vegus). All postganglionic parasympathetic fibres from cranial nerves travel with branches of CN V (trigeminal).
Spinal nerves: S2 to S4 (formed at L1/2 vertebral level).
What is the parasympathetic outflow to the eyes and what effect does this have?
Outflow from the Edinger Westphal Nucleus with CN III (oculomotor) synapses with the ciliary ganglion and then travels postganglionically with CN Va (trigeminal - opthalmic).
Pupil constriction and accomodation.
What is the parasympathetic outflow to the mucous membranes and what effect does this have?
Outflow from the superior salivatory nucleus with CN VII (facial) via the greater petrosal nerve to the pterygopalatine ganglion, then with CN Vb (maxillary nerve).
- affects everything above the maxillary teeth (eg. palate; nasal cavity; sinuses; lacrimal gland).
Outflow from salivatory nucleus with CN VII (facial) via chorda tympani to the submandibular ganglion, then with CN Vc (mandibular nerve).
- affects everything below the mandibular teeth (eg. sublingua and submandibular glands).
What is the parasympathetic outflow to the parotid gland?
Outflow from the inferior salivatory nucleus with CN IX (glossopharyngeal) via the lesser petrosal nerve to the otic ganglion, then with CN Vc (mandibular nerve) to the parotid gland.
What is the parasympathetic outflow to the organ-specific ganglia?
Outflow from the dorsal nucleus of the vagus, with CN X to the organ-specific ganglia.
Where do the pelvic splanchnic nerves emerge from?
S2 to S4
Describe the autonomic innervation of the heart:
Parasympathetic supply to the heart via the vagus nerve (X) to the SA and AV nodes.
Sympathetic innervation to the heart via the cervical cardiac (splanchnic) nerves to the SA and AV nodes and also to the ventricular muscle.
