Autonomic NS Introduction Flashcards
What nerves make up the Peripheral NS
12 pairs of cranial nerves and 31 pairs of spinal nerves.
Afferent = tissue to the CNS = somatic/visceral.
= sensory.
Efferent = CNS to tissue = somatic motor or autonomic.
What is the autonomic NS?
The enteric, sympathetic and parasympathetic NS = everything out of voluntary control - BP, HR, kidneys, bladder, GI tract.
Subconscious control of organs and homeostasis.
All outputs from CNS to the body except somatic motor innervation.
CNS uses autonomic motor nerves to innervate visceral effectors - cardiac muscle, SM + glandular epithelium.
What are the functions of the ANS?
Contraction/relaxation of SM in blood vessels, organs, airways.
Regulate glandular secretion.
Control HR + metabolism.
What organs are sympathetic or parasympathetic innervated only?
Which organs have P and S do the same thing?
Sweat glands + blood vessels = sympathetic only.
Parasympathetic only = ciliary muscle in the eyes.
Salivation = activated by both parasympathetic and sympathetic…
What organs have sympathetic or parasympathetic dominance.
Sweat glands + blood vessels = sympathetic only.
Parasympathetic only = ciliary muscle in the eyes.
In the heart = Sympathetic NS is dominant.
In GI tract = parasympathetic NS is dominant.
How are ganglia arranged in the parasympathetic and sympathetic NS
Sympathetic = pre-ganglionic fibre is v. short and ganglia arranged in chain close to spinal cord = v. long post-ganglionic fibre.
Parasympathetic = long pre-ganglionic fibre, with ganglia v. close to the organ w/ short post-ganglionic fibre.
Where are the cell bodies of pre-ganglionic and post-ganglionic neurones?
What about myelination?
What can be considered a specialised ganglion?
Soma of pre-ganglionic fibre is in the CNS (spinal cord)…
Synapse at autonomic ganglia - release ACh on nicotinic receptors…
Soma of post-ganglionic fibre is in the autonomic ganglion + synapse close to target organ…
Pre-ganglionic fibre is small diameter + myelinated
Post-ganglionic fibre is small diameter + unmyelinated.
The adrenal medulla …. described as modified sympathetic ganglia - with Chromaffin cells as post-synaptic neurone equivelant…
What receptors are expressed in autonomic ganglia?
ONLY GANGLION-TYPE NICOTINIC ACH RECEPTORS!!!!!
FOR BOTH parasympathetic and sympathetic!
What are the consequences of unspecific nicotinic ACh stimulation?
Activation of both paraysmpathetic and sympathetic activity.
Skeletal muscle stimulation = somatic motor.
Secretion of adrenaline from adrenal medulla - from chromaffin cells?
What are stimulants?
Nicotine, DMPP.
Stimulate nicotinic ACh receptors + with ganglia prefernence!!..
Results in tachycardia, elevated BP + secretions…
What is trimetaphan?
Antagonist of GANGLIONIC nicotinic ACHh receptors.
= blocks autonomic ganglionic response.
= used adjunct to anaesthesia to induce hypotension + block secretions.. or emergency BP lowering!
What are the effects of ganglion blocking drugs?
Mostly cardiovascular effects:
Compensatory tachycardia, postural hypotension (loss of sympathetic vasoconstriction after standing), vasodilation, reduced secretion, pupil dilation..
What target organs of the sympathetic NS do not release NA at target?
Post-ganglionic fibre of sympathetic NS usually releases NA, except:
Dopamine = renal vessels.
Sweat glands = ACh…
What co-transmitters are released alongside NA/ACh?
Why?
Prostaglandins, histamine, adenosine, bradykinin…
Non-adrenergic, non-cholinergic transcrmitters = NANC.
To fine tune autonomic activity, different onset/duration of action, with different ratio of NANC released based on intensity of stimulus.
How is post-ganglionic synapse response changed by co-transmitters?
The release of NA at post-ganglionic synapse ALONE causes slow contraction of SM muscle.
Co-transmission with ATP causes fast onset, prolonged contraction.
The release of ACh causes rapid response…
NO leads to an intermediate response, with VIP causing a slow response in paraysmpathetic NS….
VPY with NA causes an intemediate response in sympathetic…
