Synapses and drugs

Question 1

How is the speed of impulse propagation increased?

Answer 1

by myellin

Question 2

What is saltatory conduction?

Answer 2

action potentials are generated at the nodes of ranvier

Question 3

What is synaptic transmission

Answer 3

pass on the action potential

Question 4

Where is the action potential?

Answer 4

at the presynaptic neurone

Question 5

What are the 2 alternatives to explain the process of synaptic transmission?

Answer 5

electrical- potential goes from one cell to next

chemical- chemical is released by pre-synaptic neurone

Question 6

What is the evidence for chemical synaptic transmission?

Answer 6

Synaptic cleft- as its the section between the 2 neurones and if neurones are not touching each other then it cant be electrical
Synaptic delay- there is a delay of 0.5-0.8msec which means that a chemical must be involved unlike an electrical signal which is fast
Classic Otto Loewi experiment- 1 heart attached to a vagus nerve, whenn stimulating vagus nerve the heart would slow down. Then he attached 2 hearts with the vagus nerve and they both slow down. This could only happen from a chemical being released from a vagus nerve

Question 7

What is the length of the synaptic cleft

Answer 7

30-40nm

Question 8

What are electical synapses?

Answer 8

adjacent cells joined via gap junctions, thus ionic continunity between cells
fast but inflexible

Question 9

What do gap junctions act as?

Answer 9

electrical synapse

Question 10

What does it mean if the electrical synapse is inflexible?

Answer 10

you can transmitt action potential but cant modify action potential

Question 11

Why are electrical synapses fast?

Answer 11

No neurotransmitter is released

action potential potential will go from neurone directly to the post synaptic neurone

Question 12

Where are electrical synapse?

Answer 12

You have them in your heart and muscles of eye

Question 13

What is the structure of a chemical synapse?

Answer 13

mitochondria
vesicles ( containing neurotransmitter)
synaptic cleft
post synaptic receptors

Question 14

Why does the presynaptic area has lots of mitochondria?

Answer 14

its very energy intense

Question 15

What are the inital stages of chemical synaptic transmission?

Answer 15

1. the arrival of an action potential causes the influx of ca2+
2. this causes the vesicle to migrate towards the presynaptic membrane
3. here it fuses with the meembrane and releases the neurotransmitter via exocytosis
4. the transmitter diffuses down the concentration gradient across the synaptic cleft and binds to post synaptic receptors changing the shape of the protein and ion channels open and diffuse

Question 16

What can a single post synaptic cell receive their synaptic input from?

Answer 16

from several thousand presynaptic neurons

Question 17

What is motor endplate?

Answer 17

junction between nerve cell and muscle cell

a neuromuscular junction

Question 18

What is the experiment of recording from 2 points on a muscle fibre following neural stimulation?

Answer 18

1, A motor neurone is stimulated

2. 2 electrodes put on muscle cell
3. action potential recorded

Question 19

What is an endplate?

Answer 19

when recording the action potential close to where the stimulus was, you have a positive bump

Question 20

What did the drug curare do?

Answer 20

Used a drug curarae
It stopped action potential in muscle cells- paraylsis/not able to move
Ended in endplate potential

Question 21

What is an endplate potential?

Answer 21

when the action potential on a muscle fibre can be abolished by curare, revealing the endplate potential (triggering the action potential)

Question 22

What is a neurotransmitter?

Answer 22

ACH

Question 23

how does ACH trigger action potential at neuromuscular junction ?

Answer 23

bind to receptors on the sarcolemma, opening sodium channels
leading to influx of sodium ions and an EPP
If threshold is reached, an action potential is generated

Question 24

What happens when ACH is on the muscle cell?

Answer 24

it will contract as ACH is released and triggered EPP, initiating depolarisation which triggers action potential on the muscle

Question 25

What was the experiment between 2 neurones?

Answer 25

stimulated motor neurons in the spinal cord of a cat | then recorded from post synaptic neuron

Question 26

What are the 2 neurons he used?

Answer 26

EPSP and IPSP

Question 27

What is inhibitory?

Answer 27

When taking it further away from threshold (getting more negative)

Question 28

What does the post synaptic cell do?

Answer 28

takes a decision whether fire or not depending on the potentials added together in the cell body

Question 29

What is EPSP?

Answer 29

excitatory postsynaptic potential

Question 30

What is IPSP?

Answer 30

Inhibitory postsynaptic potential

Question 31

How do you make postsynaptic cell negative IPSP?

Answer 31

caused by neurotransmitter opening CL channels and CL go in to neurone or K+ open and K+ go out the cell Both would hyperpolarise the cell and cause IPSP

Question 32

How do you make the inside of a neurone positive EPSP?

Answer 32

``` Small depolarisation caused by neurotransmitter released binding to receptors opening Na+ ion channels Na+ go into the neurone causes EPSP (depolarisation) ```

Question 33

What can neurotransmitters do?

Answer 33

alter ionic permability by binding onto postsynaptic membrane protein receptors (activation of receptors) Only some neurotransmitters affect

Question 34

What are the 2 mode of action of transmitters?

Answer 34

Direct activation of an ionic channel (na+ etc) | Use of a secondary messenger

Question 35

What is a secondary messenger?

Answer 35

neurotransmitter released binds to receptor which is not the ion channel, but it releases chemicals which act on ion channel and open or shut them.

Question 36

What are the 3 mechanisms of transmitter inacitvation (get rid of neurotransmitter such as ACH)?

Answer 36

Diffusion Reputake- presynaptic neurone sucks neurotransmitter Enzymatic breakdown (ACH-esterase)- breakdown of neurotransmitter

Question 37

Summary of events at a chemical synapse

Answer 37

1. arrival of action potential causes influx of calcium ions 2. calcium causes vesicles contraning neurotransmitter to migrate to presynaptic membrane 3. transmitter is released via exocytosis 4. transmitter migrates to postsynaptic receptors 5. activation of receptors causes change in postsynaptic ionic permability 6. transmitter inacitvation via reputake,diffusion and enzyme breakdown 7. IPSP, EPSP (EPP)

Question 38

What is an example of another neurotransmitter?

Answer 38

nitric oxide

Question 39

What is dayls law

Answer 39

one neurone contains one neurotransmitter

Question 40

What are the 2 basic types of acetylcholine receptor?

Answer 40

nicotinic | muscarinic

Question 41

What does nicotinic receptor do?

Answer 41

it occurs at neuromuscular junction- ACH- open Na+ channels which therefore means its excitatory- muscles contract

Question 42

What does the muscarinic receptor do?

Answer 42

occur on heart-ACH- open K+ and Cl- channels- are therefore inhibitory

Question 43

What is the affect of ACH?

Answer 43

same neurotransmitter but 2 different effects depending on the receptor

Question 44

What is Agonists

Answer 44

drug that enhances effectiveness of a neuron- turn the neurone on

Question 45

What are antagonists

Answer 45

drug that supresses specific neurons- turn neuron off

Question 46

What do drugs do?

Answer 46

either enhance neurotransmission or depress

Question 47

What are the examples of the mode of action of a selection of therapeutic drugs?

Answer 47

L-dopa Botox Atropine Prozak