Introduction to Neurones, Nerve Conduction & Synaptic Transmission Flashcards
what is the role of dendrites?
receives inputs and convey graded electrical signals passively to soma
what does the cell body (soma) contain?
nucleus
ribosomes
mitochondria
endoplasmic reticulum (Nissi substance)
what is the role of the cell body (soma)?
integrates incoming electrical signals that are conducted passively to axon hillock
what is the role of the axon hillock?
site of initiation of action potential
what is the role of the axon?
conducts output signals as action potentials to presynaptic terminal
what is the role of the synapse?
point of communication between neurones
give examples of the following types of neurones:
a) unipolar?
b) pseudounipolar?
c) bipolar?
d) multipolar?
a) unipolar - peripheral autonomic neurone
b) pseudounipolar - dorsal root ganglion neurone
c) bipolar - retinal bipolar neurone
d) multipolar - low motor neurone
what causes upstroke of action potential?
influx of Na+ via voltage activated Na+ channel
what causes downstroke of action potential?
efflux of K+ via voltage activated K+ channel
what does the term “overshoot” mean in relation to action potential?
very brief period when polarity is reversed to inside positive
what is the consequence of a nerve cell membrane being leaky (not perfect insulator)?
passive signals do not spread far from their site of origin due to current loss across membrane accompanied by reduced change in potential
what does the distance travelled by membrane depend on?
membrane resistance - rm - (this needs to be high)
axial resistance - ri - (this needs to be low)
what can increase passive current spread and therefore AP velocity?
decrease ri (possible by increasing axon diameter)
increase rm (by adding myelin)
what provides myelin in the PNS and CNS?
schwann cells in PNS
oligodendrocytes in CNS
where is conduction faster - myelinated or non-myelinated axons?
myelinated
what is the name of the demyelination condition in:
a) CNS?
b) PNS?
a) multiple sclerosis
b) gullian-barre
what is the membrane difference between pre synaptic and post synaptic membranes?
pre synaptically = active zones around which vesicles cluster
post synaptically = post synaptic density containing neurotransmitter receptors
what is the most common type of synapse (classified by location of presynaptic terminal upon post synaptic cell)?
axodendritic
axosomatic (common) and axoaxonic (less common) are also types
what is example of neurotransmitter which elicits excitatory synapse?
glutamate
depolarising response
what is example of neurotransmitter that elicits inhibitory synapse?
y-aminobutyric acid (GABA)
glycine
(hyperpolarising response)
what is meant by spatial summation?
many inputs converge upon a neurone to determine its output
what is meant by temporal summation?
a single input may modulate output by variation in action potential frequency of that input
where are acetylcholine, amino acids and amines released from?
synaptic vesicles
where are peptides released from?
secretory vesicles
what neurotransmitters activate ionotrophic ligand-gated ion channels (LGICs) and thus mediate fast transmission?
glutamate GABA glycine acetylcholine 5-HT
which neurotransmitters activate metabotropic GPCR and thus mediate slow transmission?
all except glycine
what of ionotrophic receptors and metabotropic GCPR are direct / indirect gating?
ionotrophic = direct (receptor is integral component of molecule that forms channel it controls)
metabotropic = indirect (receptor and channel it controls are distinct)
give examples of amino acids in the CNS?
glutamate
GABA
glycine
give examples of amines in CNS?
dopamine
histamine
noradrenaline
serotonin
give examples of peptides in CNS?
CCK dysnorphin ENK neuropeptide Y somatostatin substance P TRH VIP
what is the difference in speed of transmission in ligand gated ion channel receptors and GPCR?
ionotrophic ligand-gated ions mediate fast neurotransmission
GPCR mediate slow neurotransmission
describe the structure of ionotropic LGIC receptors vs that of metabotropic receptors?
ionotropic receptor for neurotransmitter is itself a channel
metabotropic receptors bind neurotransmitter and then signal to other G proteins etc to open a channel to let ions in
if glutamate has both ionotropic and metabotropic receptors on post-synaptic membrane, what kind of response does this create?
a fast and slow EPSP are generated from each of channels respectively
what types of ionotropic receptors can glutamate bind to and activate an ion channel?
AMPA
kainic acid
(collectively non-NMDA)
NMDA
how do the responses of each ionotropic glutamate receptor differ?
AMPA - large but transient AP
NMDA - smaller and slower AP
