Neurotransmission in the Nervous System

Question 1

what are the 2 classes of molecule that allow neurotransmission

Answer 1

• chemical molecules

- chemically gated receptors

Question 2

what do end plate potentials do

Answer 2

• it records the potential changes that are occurring across the muscle fibres

Question 3

if you are close to the end plate….

Answer 3

• If you are close to the end plate then you get a largest end plate potential as you move the voltage further away is gets smaller

Question 4

what are end plate potentials build up

Answer 4

• EPPs are built of whole numbers of miniEPPs

- Consists with evoked EPPs occurring in multiples of the quantal amplitude

Question 5

what do miniEPPs do

Answer 5

they occur close to the EPP and can correspond with 1 or 2 vesicles that are released, this gives rise to depolarisation that has a certain amplitude

Question 6

what can neurotransmitters released in the CNS cause

Answer 6

• EPSPs and IPSPs in the post synaptic cell

Question 7

how is an EPSP or EPP conducted

Answer 7

• There is an asymmetric complementary distribution of monovalent cations across the membrane
• on the inside there is a lot of potassium whereas on the outside there is a lot of sodium
• Because of this distribution of potassium ions there isa negative membrane potential, this is because the potassium ions are leaving the permeable membrane and this makes it negative
• Nitocinic AcH receptor – 2 acetylcholine receptors bind to the receptor and this opens the receptor
  This causes sodium to go in across the membrane in order to depolarise the membrane and gives rise to the EPP or EPSP

Question 8

How is an IPSP generated

Answer 8

• Chloride moves inwards because ECl is more negative than the resting potential, BUT importantly activating GABAa ALSO makes the membrane more leaky to current
• Makes the hyperpolarise the membrane, makes the membrane leaky at a charge, makes the membrane leakier and shuts down the cell making it less excitable

Question 9

what is the neurotransmitter in the primary sensory neurones

Answer 9

glutamate

Question 10

what are the neurotransmitters in the CNS

Answer 10

Acetylcholine

Amino acids:
Glutamate
g-aminobutyric acid (GABA) (inhibitory)
Glycine (inhibitory)

Biogenic Amines:
Noradrenaline
5-HT
Dopamine

Question 11

What are the inhibitor neurotransmitters in the CNS

Answer 11

GABA and glycine

Question 12

how does inhibition of a reflex work

Answer 12

• In order to inhibit the activity of the extensor motor neurone need to provide glycine in order to inhibit it ,
• need to have an inhibitory interneurone that is able to provide a glycine input, gives rise to reciprocal antagonist inhibition

Question 13

What are the excitatory neurotransmitters

Answer 13

• glutamate and acetylcholine

Question 14

What is an EPSP

Answer 14

An EPSP occurs when an excitatory neuron e.g Ach,
or Glutamate binds it’s respective post synaptic
receptor resulting in an influx of sodium, leading to
to depolarisation

Question 15

what is an IPSP

Answer 15

An IPSP is essentially the opposite. An inhibitory
neurotransmitter e.g. GABA or Glycine binds its
respective receptor, resulting in Chloride influx
which hyperpolarises the neuron.

Question 16

describe the fast and modulator effects of glutamate

Answer 16

Has a fast excitatory effect on postsynaptic cells via
AMPAr and a voltage dependent effect via the
NMDAr.
Modulatory effects via the metabotropic G
protein coupled receptors.

Question 17

describe the fast and modulator effects of acetylcholine

Answer 17

Fast excitatory effect on postsynaptic cells via
nicotinic receptors
a slower modulatory effect
via Muscarinic G protein coupled receptors.

Question 18

Describe glycine

Answer 18

The glycine receptor is a nicotinoid receptor and
chloride channel. Key inhibitory transmitter in spinal
cord.

Question 19

describe the fast and modulator effects of GABA

Answer 19

The GABA receptor is the key inhibitory
neurotransmitter of the brain and it has a fast
inhibitory effect via GABAa (a chloride channel)
a slower neuromodulatory action via GABAb
metabotropic receptors.

Question 20

what neurotransmitters have fast and modulator responses

Answer 20

• Glutamate
• GABA
• 5 HT
• acetylcholine

Question 21

what neurotransmitters have fast responses

Answer 21

glycine

Question 22

what neurotransmitters have modulator responses

Answer 22

noradrenaline

dopamine

Question 23

how does acetylcholine bind to open up a ligand ion channel

Answer 23

• it binds at a C loop, this destabilises the hydrophobic interactions and causes the channels to open

Question 24

give examples of neuromodulators that are not fast neurotransmitters

Answer 24

•	co-transmitter neuropeptide
		  substance P
•	e.g. inflammatory mediators etc
	prostaglandin E2
		  bradykinin

Question 25

How do you terminate the transmitter

Answer 25

• Transmitter breakdown

* Reuptake using selective transport mechanisms

Question 26

what happens when you terminate a neurotransmitter

Answer 26

this stops the EPSP, IPSP or end plate

Question 27

how do you inhibit neurotransmitter breakdown

Answer 27

• acetylcholinesterase can be inhibited by a enrol sagest such as Sarin, or Novicokck this is irreversible

Question 28

how can you tell if neurotransmitter breakdown has been inhibited

Answer 28

• pin point pupils

- kills you via paralysis of breathing

Question 29

how do you treat inhibition of a acetylcholinesterase

Answer 29

• medicinally inhibited by neostigmine, physostigmine etc for treatment of myasthenia gravis (pyridostigimine in Gulf War Syndrome)
- these work by binding to the receptors whcih sarin would bind to

Question 30

what are the waves and reflexes involved in testing muscle action potential

Answer 30

• M wave direct activation of motor units by electrical stimulation
• H-reflex, electrical equivalent to stretch-reflex
• F-wave, antidromic motor nerve action potentials bouncing off the a-motoneurons

Question 31

what abnormalities might you detect in muscle action potential that is recorded by electrical stimulation of a peripheral nerve

Answer 31

Recorded evoked muscle action potentials

• Peripheral demyelination - - Look for giant motor units (MND/ALS)
• Lambert-Eaton myasthenic syndrome
• Myasthenia Gravis
• Carpal tunnel entrapment

record sensory nerve volley by recording in the digits
- peripheral demyelination

Question 32

where are glutamate transporters for reputake

Answer 32

• neurones and glia
  Glutamate is taken-up into pre and post –synaptic terminals, and into the adjacent glia, terminating its neurotransmitter action

Question 33

how is GABA reuptaken

Answer 33

GABA reuptake into presynaptic terminals and astrocytes by GATs

Question 34

how are biogenic amines reuptaked into presynaptic terminals

Answer 34

Biogenic amine reuptake into presynaptic terminals (e.g. for noradrenaline uptake 1 and uptake 2 mechanisms

Question 35

what do amine and amino acid transporter use for reuptake

Answer 35

• they utilise the energy stored in the sodium gradient