Sesh 8: The Autonomic Nervous System Flashcards
What region of the spinal cord do sympathetic pre-ganglionic nerves arise from?
Thoracolumbar region, from the lateral horn of the spinal cord.
Where do pre-ganglionic parasympathetic nerves arise from?
Craniosacral regions.
Which division of the ANS has short post-ganglionic fibres?
Parasympathetic, as ganglia are close to target organs.
Where do pre-ganglionic sympathetic fibres first synapse?
In the paravertebral sympathetic chain ganglion, close to the spinal cord.
What neurotransmitter do all pre-ganglionic fibres use, and what post-ganglionic receptors does it activate?
Acetylcholine activates nicotinic AChRs.
What neurotransmitter do parasympathetic post-ganglionic neurones release, and what receptors does this activate at the effector?
Acetylcholine activates muscarinic AChRs (1-5).
What neurotransmitter do most sympathetic post-ganglionic neurones release? What are exceptions to this?
Most release Noradrenaline.
Exceptions= neurones to sweat glands, hair follicles etc, that release ACh.
What type of receptors receive signals at the neuroeffector junction?
GPCRs- transduce signal via intracellular cascade.
Give examples of Non-adrenergic, non-cholinergic (NANC) transmitters found in the ANS.
- ATP
- NO
- 5-HT
- Neuropeptides e.g. Substance P
Why is there a hormonal aspect to the sympathetic response?
Chromaffin cells in the adrenal medulla are considered specialised sympathetic post-ganglionic fibres that, when stimulated, release Adrenaline into the bloodstream.
What is the effect of increased parasympathetic tone on:
- the heart
- bronchial smooth muscle
- salivary/sweat/ lacrimal glands ?
- Bradycardia and reduced conduction velocity- M2 R’s
- Contraction of bronchiolar smooth muscle -M3 R’s
- Increased secretion via M1/3 R’s
What are the effects of increased sympathetic tone on:
- the heart
- bronchiolar smooth muscle
- vascular smooth muscle ?
- Tachycardia and positive inotropy via beta-1 R’s
- Relaxation via beta-2 R’s
- Contraction, to redistribute blood via alpha-1 R’s
What is the umbrella term for ANS disorders?
Dysautonomia
What is SLUDGE?
A clinical syndrome resulting from excessive activation of the parasympathetic nervous system: S=salivation L=lacrimation U=urination D=defaeaction G=GIT disturbance E=emesis
What are the main methods for termination of cholinergic neurotransmission and noradrenergic neurotransmission?
- Cholinergic- breakdown by AChesterase
- Noradrenergic- pre-synaptic uptake via Na+-dependent symport
