FHD- Neurotransmission

contains topics: neurotransmitters, neuronal signalling

what are excitable cells

cells that can generate action potentials

what is the voltage across an excitable cell for

to signal changes

how are the voltages and currents of excitable cells determined

via ions

what membrane potential do fully permeable membranes have?

0Vm

what do cells usually have a resting potential of (range)

between -70 and -90Vm

what is meant by equilibrium potential

the ideal potential of an ion

what will Vm reach if many Na channels are conducting in isolation 

+60Vm

what Vm will be reached if many K channels are conducting in isolation

-90Vm

what Vm would be reached if both Na and K channels are open (and the membrane is equally permeable to both)

-15Vm (the average between the two)

what is the range of membrane potential for action potential propagation

+20 to +40Vm

how does failed initiation of the action potential occur

when the permeability of K pulls Vm back to resting stage

what occurs post hyperpolarisation 

the refractory period 

what occurs during the refractory period

resting potential is reattained via the movement of ions

what type of conductions do synapses allow for (in terms of direction)

unipolar conduction

what are the two types of synapses

chemical and electrical

what do electrical synapses require

a gap junction

what are the three broad categories of neurotransmitters

amino acids, monoamines, others

which neurotransmitters are amino acids

glutamate, aspartate, GABA, glycine

which neurotransmitters are monoamines

dopamine, noradrenaline, adrenaline, serotonin

which neurotransmitters fall under the ‘others’ category

acetylcholine, peptides

where is noradrenaline released from 

sympathetic nerve terminals 

where is adrenaline secreted

by chromaffin cells in the adrenal medulla

what are metabotropic receptors

GPCRs (G protein coupled receptors)

what type of category do adrenoreceptors fall under

metabotropic/ GPCR

in terms of the release of noradrenaline, which receptor is postsynaptic

alpha 1

in terms of the release of noradrenaline, which receptor is presynaptic

alpha 2

what is the antagonist for both the alpha 1 and alpha 2 receptor

phentolamine

which receptor is found in the blood vessels and what is it responsible for 

alpha 1. it is responsible for vasoconstriction 

how is vasoconstriction linked to fight or flight 

it increases vascular resistance to either maintain or raise blood pressure during stress

which receptors are found in GI smooth muscle, and what are they responsible for 

alpha 1, and beta 2, they are responsible for relaxation 

which receptors are found in GI sphincteric muscle and bladder sphincter, and what are they responsible for 

alpha1 and beta 2, they are responsible for contraction

which receptors are found in the hepatocytes of the liver and what are they responsible for 

alpha 1 and beta 2, they are responsible for glycogenolysis 

which receptor is found in the presynaptic sympathetic neurons and what is it responsible for 

alpha 2, it is responsible for decreased neurotransmitter release 

why would alpha 2 receptors be responsible for decreased neurotransmitter release during fight or flight response

for energy efficiency, to prevent overstimulation, and for temporal control

what is temporal control

termination of a signal once a threat has passed allowing the system to reset

which receptor is found in the heart  and what is it responsible for 

beta 1, it is responsible for increased heart rate and force of contraction

which receptor is found in the bronchi and blood vessels, and what is it responsible for 

beta 2, it is responsible for dilation/ relaxation 

which receptor is found in the skeletal muscle and what is it responsible for 

beta 2, it is responsible for tremor and glycogenolysis 

which receptor is found in adipose tissue and what is it responsible for 

beta 3, it is responsible for lipolysis and thermogenesis 

what is lipolysis 

the conversion of triglycerides to fatty acids and glycerol 

what is glycogenolysis

the breaking down of glycogen to glucose

which receptor is found in the bladder (NOT the bladder sphincter) and what is it responsible for 

beta 3, it is responsible for relaxation which prevents urination 

how does relaxation prevent urination 

this contraction refers explicitly to the detrusor muscle that would otherwise contract to expel urine 

what secondary messenger effect does the alpha 1 receptor trigger

Gaq

what secondary messenger effect does the alpha 2 receptor trigger

Gai

what secondary messenger effect do the beta 1, beta 2, and beta 3 receptors trigger

Gas

what are the two receptors used for ACh

muscarinic and nicotinic 

what type of receptor is muscarinic (mAChR)

metabotropic/ GPCR

what type of receptor is nicotinic

ionotropic

where are the muscarinic receptors located

post synaptically (on effector) in smooth muscle, cardiac muscle and glands

which receptor primarily acts in the parasympathetic nervous system

muscarinic

what is the exception to muscarinic receptors only acting in the parasympathetic nervous system 

in sweat glands muscarinic receptors control sympathetic response 

what are the agonists for muscarinic receptors

ACh, muscarine

what are the antagonists for muscarinic receptors

atropine/ belladonna

where are nicotinic receptors located

on the postsynaptic membrane, in autonomic ganglia, motor endplate and CNS

what are the agonists for nicotinic receptors

ACh and nicotine

what are the antagonists for nicotinic receptors

curare/ tubocurarine

which receptors act where in terms of the parasympathetic ANS

nicotinic receptors act on the postganglionic neurone membrane, muscarinic receptors act on the effector 

which receptors act where in terms of the sympathetic ANS

nicotinic receptors act on the postganglionic neurone membrane, adrenoreceptors act on the effector 

what is the synapse like on the target organ in terms of the sympathetic ANS

long synapse on target organ 

what is the synapse like on the target organ in terms of the parasympathetic ANS

short synapse on target organ

what occurs to postganglionic axons in the adrenal medulla

they never develop and instead released adrenaline and noradrenaline directly into the blood stream 

what affects do the sympathetic and parasympathetic nervous systems exhibit on tropic force

the sympathetic increases it, whilst the parasympathetic has no affect on it

what affects do the sympathetic and parasympathetic nervous systems exhibit on GI transit

sympathetic slows it down, parasympathetic speeds it up 

what affects do the sympathetic and parasympathetic nervous systems exhibit on bronchi and bronchioles

sympathetic relaxes them, parasympathetic constricts them

how can drugs be used to treat hypertension in regards to agonism/ antagonism 

parasympathetic nervous system can be stimulated by a muscarinic agonist

how can drugs be used to treat asthma in regards to agonism/ antagonism 

parasympathetic response can be reduced via presence of a muscarinic antagonist