Introduction to Neurones, Nerve Conduction & Synaptic Transmission

Question 1

what is the role of dendrites?

Answer 1

receives inputs and convey graded electrical signals passively to soma

Question 2

what does the cell body (soma) contain?

Answer 2

nucleus
ribosomes
mitochondria
endoplasmic reticulum (Nissi substance)

Question 3

what is the role of the cell body (soma)?

Answer 3

integrates incoming electrical signals that are conducted passively to axon hillock

Question 4

what is the role of the axon hillock?

Answer 4

site of initiation of action potential

Question 5

what is the role of the axon?

Answer 5

conducts output signals as action potentials to presynaptic terminal

Question 6

what is the role of the synapse?

Answer 6

point of communication between neurones

Question 7

give examples of the following types of neurones:

a) unipolar?
b) pseudounipolar?
c) bipolar?
d) multipolar?

Answer 7

a) unipolar - peripheral autonomic neurone
b) pseudounipolar - dorsal root ganglion neurone
c) bipolar - retinal bipolar neurone
d) multipolar - low motor neurone

Question 8

what causes upstroke of action potential?

Answer 8

influx of Na+ via voltage activated Na+ channel

Question 9

what causes downstroke of action potential?

Answer 9

efflux of K+ via voltage activated K+ channel

Question 10

what does the term “overshoot” mean in relation to action potential?

Answer 10

very brief period when polarity is reversed to inside positive

Question 11

what is the consequence of a nerve cell membrane being leaky (not perfect insulator)?

Answer 11

passive signals do not spread far from their site of origin due to current loss across membrane accompanied by reduced change in potential

Question 12

what does the distance travelled by membrane depend on?

Answer 12

membrane resistance - rm - (this needs to be high)

axial resistance - ri - (this needs to be low)

Question 13

what can increase passive current spread and therefore AP velocity?

Answer 13

decrease ri (possible by increasing axon diameter)

increase rm (by adding myelin)

Question 14

what provides myelin in the PNS and CNS?

Answer 14

schwann cells in PNS

oligodendrocytes in CNS

Question 15

where is conduction faster - myelinated or non-myelinated axons?

Answer 15

myelinated

Question 16

what is the name of the demyelination condition in:

a) CNS?
b) PNS?

Answer 16

a) multiple sclerosis

b) gullian-barre

Question 17

what is the membrane difference between pre synaptic and post synaptic membranes?

Answer 17

pre synaptically = active zones around which vesicles cluster

post synaptically = post synaptic density containing neurotransmitter receptors

Question 18

what is the most common type of synapse (classified by location of presynaptic terminal upon post synaptic cell)?

Answer 18

axodendritic

axosomatic (common) and axoaxonic (less common) are also types

Question 19

what is example of neurotransmitter which elicits excitatory synapse?

Answer 19

glutamate

depolarising response

Question 20

what is example of neurotransmitter that elicits inhibitory synapse?

Answer 20

y-aminobutyric acid (GABA)

glycine

(hyperpolarising response)

Question 21

what is meant by spatial summation?

Answer 21

many inputs converge upon a neurone to determine its output

Question 22

what is meant by temporal summation?

Answer 22

a single input may modulate output by variation in action potential frequency of that input

Question 23

where are acetylcholine, amino acids and amines released from?

Answer 23

synaptic vesicles

Question 24

where are peptides released from?

Answer 24

secretory vesicles

Question 25

what neurotransmitters activate ionotrophic ligand-gated ion channels (LGICs) and thus mediate fast transmission?

Answer 25

glutamate 
GABA
glycine 
acetylcholine 
5-HT

Question 26

which neurotransmitters activate metabotropic GPCR and thus mediate slow transmission?

Answer 26

all except glycine

Question 27

what of ionotrophic receptors and metabotropic GCPR are direct / indirect gating?

Answer 27

ionotrophic = direct (receptor is integral component of molecule that forms channel it controls)

metabotropic = indirect (receptor and channel it controls are distinct)

Question 28

give examples of amino acids in the CNS?

Answer 28

glutamate
GABA
glycine

Question 29

give examples of amines in CNS?

Answer 29

dopamine
histamine
noradrenaline
serotonin

Question 30

give examples of peptides in CNS?

Answer 30

CCK
dysnorphin 
ENK
neuropeptide Y
somatostatin 
substance P
TRH 
VIP

Question 31

what is the difference in speed of transmission in ligand gated ion channel receptors and GPCR?

Answer 31

ionotrophic ligand-gated ions mediate fast neurotransmission

GPCR mediate slow neurotransmission

Question 32

describe the structure of ionotropic LGIC receptors vs that of metabotropic receptors?

Answer 32

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

Question 33

if glutamate has both ionotropic and metabotropic receptors on post-synaptic membrane, what kind of response does this create?

Answer 33

a fast and slow EPSP are generated from each of channels respectively

Question 34

what types of ionotropic receptors can glutamate bind to and activate an ion channel?

Answer 34

AMPA
kainic acid
(collectively non-NMDA)

NMDA

Question 35

how do the responses of each ionotropic glutamate receptor differ?

Answer 35

AMPA - large but transient AP

NMDA - smaller and slower AP