Organisation of Nervous System Flashcards
what are the two branches of the nervous system?
CNS and peripheral nervous system
what are the two branches of the peripheral nervous system?
motor and sensory neurons
what are the two branches of the sensory neurones?
somatic and autonomic
what is the somatic nervous system?
controls voluntary movement
what is autonomic nervous system?
controls involuntary movement
what are the two branches of autonomic nervous system?
sympathetic and parasympathetic nervous system
what is the sympathetic nervous system?
fight or flight
what is the parasympathetic nervous system?
rest and digest
what is the difference between sensory and motor neurones?
sensory is afferent and motor is efferent
what are pre-ganglionic neurones?
ones that originate in the spinal cord or brainstem
what are post-ganglionic neurones?
ones that lie in the peripheral nervous system in nerve cell called autonomic ganglia
what is a chromaffin cell?
a type of cell that makes neurohormones which are chemicals that are made by nerve cells that signal other cells
what role do pre-ganglionic neurones have?
creates synapses with chromaffin cells and stimulates the release of epinephrine
what kind of muscles are involved in the somatic nervous system?
skeletal
what kinds of muscles are involved in autonomic nervous system?
cardiac muscle, smooth muscle and glands
where are nicotinic receptors found?
somatic neuromuscular junctions, autonomic ganglia and adrenal medulla
where are muscarinic receptors found?
parasympathetic neuro-effector junctions
what effect does epinephrine and norepinephrine have on the heart?
increases force and rate of contraction
how does epinephrine effect blood vessels?
dilates vessels in skeletal muscle which decreases resistance and blood flow
how does norepinephrine effect blood vessels?
increases blood flow via constriction of vessels in skin
how does epinephrine effect blood pressure?
increases somewhat due to increased cardiac output
how does norepinephrine effect blood pressure?
increases greatly due to vasoconstriction
how does epinephrine effect airways?
dilates them
how does norepinephrine effect airways?
dilates slightly
how does epinephrine effect reticular formation?
activates
how does norepinephrine effect reticular formation?
little effect
what receptors does noradrenaline work on?
alpha or beta
where does acetylcholine act upon muscarinic receptors?
in sympathetic nervous system in sweat glands
how is adrenaline released into the blood stream?
released from adrenal medulla and acts upon nicotinic receptors which then causes it to be released into the blood stream
where is there a ganglionic modification present?
in adrenaline release as no post-ganglionic neurone present, just one long ganglion
what are the neurones like in the somatic nervous system?
single neurone with no ganglion
what are the neurones like in parasympathetic nervous system?
long-pre ganglionic and short post-ganglionic
what are the neurones like in sympathetic nervous system?
short pre-ganglionic and long post-ganglionic
what receptors used in somatic nervous system?
nicotinic receptors
what are nicotinic receptors used for?
rapid responses
what is the structure of a nicotinic receptor?
5 subunits, with each producing different receptor subunits that have different pharmacological effects
what is the skeletal and ganglionic subtype of the receptor?
skeletal is Nm and ganglionic is Nn
what does binding of Ach do on nicotinic receptors?
binding causes the opening of sodium channels leading to depolarisation
how is paralysis of skeltal muscles caused?
blocking of Nm receptors at somatic neurone-muscular junctions
do the drugs causing skeletal muscle paralysis have an effect the autonomic nervous system?
no as the drugs only effect the Nm receptors and not Nn receptors and therefore only acts upon somatic nervous system
what are the classes of neuromuscular blockers?
depolarising and non-depolarising
what are non-depolarising blockers?
competitive agonists that compete with Ach for the receptor
what are examples of non-depolarising drugs?
tubocurarine, pancuronium, vercuronium and rocuronium
what kinds of drugs bind to somatic neuromuscular junctions?
competitive agonists
what is tubocurarine and how does it work?
it is a competitive agonist that binds reversibly to receptor and prevents contraction
how can effects of tubocurarine be reversed?
concentrations of Ach can be increased
what did Claude Bernard do?
concluded that the site of paralysis is between the nerve and the junction as when the nerve was stimulated there was no contraction but contracted when muscle stimulated
what are the clinical uses of tubocurarine?
used for tube intubation, muscle relaxation during surgery, effects last about 30 minutes and does not cause muscle spasms
what is the negative effects of tubocurarine?
causes histamine release which causes vasodilation which therefore causes reception in blood pressure, itching and bronchoconstriction
what are the characteristics of rucaronium?
rapid onset and acts as a muscle relaxant, does not act as a depolarising block so rarely needs reversal
what are depolarising blockers?
persistant agonists that cause constant stimulation of nicotinic receptors
what is an example of a depolarising blocker?
suxamethonium/succinylcholine
how does succinylcholine work?
chemically similar to Ach so stimulates nicotinic Nm receptors yet cannot be broken down so remains in the cleft until the receptor looses sensitivity
what are the effects of succinylcholine? how is it terminated?
causes muscle spasms for a few seconds and then paralysis, terminated using pseudocholinesterase in the plasma
how quickly does succinylcholine work?
within 30 seconds
what drugs enhance cholinergic transmission?
physostigmine by blocking breakdown via AchE
what is physostigmine used for?
treating glaucoma
what is myasthenia gravis?
causes a reduces effect of receptors causing muscle weakness and fatigue
how is myasthenia gravis treated?
using reversible anticholinesterases which inhibit AchE causing more Ach to be present causing greater stimulation
what is botulinum toxin?
it inhibits Ach release and is injected into the muscles to reduce spasm
what are the negative effects of botulinum toxin?
causes progressive parasympathetic and somatic paralysis leading to respiratory failure
