The Autonomic Nervous System Flashcards
what are the two large divisions of the autonomic nervous system?
sympathetic and parasympathetic
what do the sympathetic and parasympathetic nervous systems do?
provide link between the central nervous system and peripheral organs. involuntary systems.
what is the basic anatomy of the autonomic nervous system? (which parts?)
cervical, gastrointestinal, lumbar, medullary, sacral, thoracic.
basic sections of sympathetic nerves?
thoracic, lumbar sections of spinal cord.
preganglionic nerves - ganglion - post ganglionic nerve.
basic sections of parasympathetic nerves?
cranial, sacral sections of spinal cord.
Preganglionic nerves – ganglion – postganglionic nerve.
basic difference between sympathetic and parasympathetic nerves?
s: preganglionic nerves short. ganglion located outside of innervated tissue
p: preganglionic nerves long. ganglion located within innervated tissue
name two neurotransmitters of the autonomic nervous system:
acetylcholine, noradrenaline.
noradrenergic neurons: what does it do and where is it located?
synthesize noradrenaline. located in periphery are sympathetic neurons, whose cell bodies lie in sympathetic ganglia.
store noradrenaline in vesicles and release into synaptic cleft. re-uptake of noradrenaline from synaptic cleft by noradrenaline transporter (SLC6A2) to reduce its effect
within the autonomic nervous system, what are cholinergic neurons?
choline taken up into the nerve. free choline within the nerve terminal is acetylated by choline acetyltransferase (CAT), which transfers the acetyl group from acetyl coenzyme A.
what terminates the effect of released acetylcholine?
acetylcholinesterase (AChE)
ACh + AChE –> choline and acetate.
what does botulinum toxin do?
Inhibits acetylcholine release from cholinergic neurons –> prevent exocytosis. progressive parasympathetic and motor paralysis.
name two indications of botulinum toxin poisoning
blepharospasm (persistent eyelid spasm)
urinary incontinence.
Anticholinesterease drugs: effects?
Inhibit acetylcholinesterase.
increases acetylcholine concentration by preventing its metabolism
Anticholinesterease drugs: effects mainly due to?
enhancement of cholinergic transmission at cholinergic autonomic synapses (and neuromuscular junction)
examples of anticholinesterease drugs: short acting and medium duration?
short: edrophonium
medium: neostigmine
indications of anticholinesterase drugs?
myasthenia gravis
(antibodies destroy the communication between nerves and muscle, resulting in weakness of the skeletal muscles. affects voluntary muscles)
simply: what are agonists and receptors of the following: pre-ganglionic nerves, sympathetic nerves, parasympathetic nerves.
- acetylcholine –> nicotinic receptors
- noradrenaline –> adrenoceptors
- acetylcholine –> muscarinic receptors
what releases adrenaline into vascular system to activate adrenoceptors?
adrenal medulla
what are nicotinic receptors activated by?
acetylcholine released from pre-ganglionic nerves
what happens when nicotinic receptors are activated?
tachycardia, an increase in blood pressure, and variable effects on gastrointestinal motility and secretions. salivary and sweat secretions
what are nicotinic receptors blocked by?
hexamethonium –> transmission block. causes hypotension and loss of cardiovascular reflexes (prev used to manage hypertension. ‘hexamethonium man’)
Name an exogenous agonist that activates nicotinic receptors. (what does exogenous agonist mean?)
Nicotine
external factors which bind to various receptors. induce biological response.
classification of adrenoceptors? (name first three)
alpha1, alpha2, beta. each splits into three further groups.
noradrenaline: where is it released, what does it activate?
released from sympathetic nerve terminals activates adrenoceptors
activation of a1 adrenoceptor: main effect?
vasoconstriction, gastrointestinal smooth muscle relaxation, salivary secretion, hepatic glycogenolysis
activation of a2 adrenoceptor: main effect?
inhibition of transmitter release (noradrenaline and acetylcholine release from autonomic nerves), platelet aggregation, contraction of vascular smooth muscle, insulin release inhibition.
activation of b1 adrenoceptor: main effect?
increased cardiac rate and force. delayed cardiac hypertrophy
activation of b2 adrenoceptor: main effect?
bronchodilation, vasodilation, relaxation of visceral smooth muscle, hepatic glycogenolysis, muscle tremor
activation of b3 adrenoceptor: main effect?
lipolysis.
can adrenoceptors co-exist? give example and effect.
b1 and b2 adrenoceptors in human heart. increase heart rate and force of contraction.
what family do the adrenoceptors/muscarinic receptors belong to?
G-protein coupled receptors. (GCPRs)
beta1 adrenoceptor: binding pocket: what does GPCR do?
GPCRs form a ‘binding pocket’ where agonists and antagonists enter.
agonists and antagonists bind to specific amino-acids on the GPCR
What does G-protein-coupled receptor (GPCR) act like in the cell? What is the role of the binding pocket in the GPCR?
GPCR receives signals from the outside. The binding pocket is where the receptor grabs onto specific molecules.
What is the function of agonists in GPCR signaling?
Agonists, like adrenaline, stabilize the receptor in a way that activates it and couples it to the cell’s internal G-protein, triggering a response.
How do antagonists, such as cyanopindolol, affect GPCR signaling?
Antagonists stabilize the receptor differently, preventing it from coupling to the G-protein and stopping the signal.
What happens to the pocket around adrenaline in GPCR binding?
There is a 2–3A ° tightening of the pocket around adrenaline, ensuring a strong and clear signal. (antagonists don’t produce this response)
critical anchoring points (endogenous catecholamines): when is beta2 adrenoceptor activated most effectively?
when there are precisely 2 carbon atoms between the ring and the amino group.
catecholamines: (class of neurotransmitter/hormone. e.g. dopamine, noradrenaline, adrenaline). endogenous means produced naturally in the body.