Neuro 7

Question 1

How long do chemical neurotransmitter take to travel across synapse

Answer 1

2ms

Question 2

Role of spines

Answer 2

Project of dendrites and receive info

Question 3

Role of soma

Answer 3

Integrate all the info

Question 4

Role of axon

Answer 4

branches into many nerve ending which allow for rapid AP transmission

Question 5

Why is synapse asymmetric

Answer 5

Pre synaptic membrane densely packed with c=vesicle and neurotransmitters. Post = only receptors

Question 6

Properties of neurotransmitters

Answer 6

1. provide diversity in neurotransmitter and receptors
2. Can have quick or slow effects, 2us - 2ms
3. Can be found in high or low conc in CNS mM to nM
4. Neurones receive multiple transmissions, and then integrate them to produce diverse functional responses

Question 7

Type of neurotransmitters and examples and their abundance

Answer 7

Amino acids - gutamate, glycine, Gamma amino butyric Acid (GABA): highest abundance
Amines - noradrenaline, dopamine: medium abundance
Neuropeptides- Opiod peptide: lowest abundance

Question 8

Describe CNS synapse activation

Answer 8

AP depolarises cell due to sodium influx, causing VGCCs to open and allow Ca2+ ion entry
Calcium triggers vesicle fusion to release NT to cleft, for binding to the receptors on the postsynaptic neurone
Transporter removes NT from cleft to pre-synaptic neurone as it is repolarised by Na+/K+-ATPase

Question 9

What repolarises the pre synaptic terminal

Answer 9

Na+/K+ ATPase

Question 10

What Is essential for CNS synapse

Answer 10

Ca2+ , transmitter release requires 200um [Ca2+] for vesicles to fuse, each carrying 4-10k molecules of NT

Question 11

What is needed for activation of transmitter

Answer 11

Ca2+ dependant and rapid transduction

Question 12

How does Rapid Release occur

Answer 12

Vesicles docked in synaptic zone, primed for release
Ca2+ entry activates a Ca2+ sensor in the protein complex
Interaction between proteins on synaptic vesicle and proteins on membrane allow rapid release in response to ca2+, leading to membrane fusion and exocytosis

Question 13

What are requirements for rapid release

Answer 13

1. Vesicles containing TS must be docked onto membrane.
2. Protein complexes must form from vesicle, membrane and cytoplasmic proteins to enable both vesicle docking and a rapid response to Ca2+ entry leading to membrane fusion and exocytosis
3. ATP and vesicle recycling

Question 14

What toxins target vesicular proteins

Answer 14

Tetanus toxin: C. Tetani causes paralysis due to tetanic contraction
Botulinum toxin: C. Botulinum - membrane and vesicular proteins, causing flaccid paralysis
Zn2+-dependent endopeptidases inhibit transmitter release
Alpha Latrotoxin: produced by the black widow spider to stimulate transmitter release to depletion

Question 15

Neurotransmitter action is defined by receptor kinetics. Describe ion channel receptors

Answer 15

Its fast (m-sec)
Mediates all excitatory and inhibitory transmissions
In CNS: gamma amino butyric acid, Glutamate
In NMJ: Ach at nicotonic recpetors

Question 16

Describe action of G protein linked receptors in this topic

Answer 16

Slow (sec-min)
Effectors may be enzymes (adenyl cyclase, phospholipase c) or channels like Ca2+/K+
In CNS and PNS: ACh at muscarinic receptors, dopamine (DA), noradrenaline (NA), 5-hydroxytryptamine (5HT) and neuropeptides e.g. enkephalin