Lecture #24 - Synaptic network (full)

Question 1

List 6 main neurotranmitters (2 EPSP and 1IPSP)

What’s a classical neurotransmitter?

Answer 1

Neurotransmitters:

• Acetylcholine(EPSP)
• Glutamate(EPSP)
• GABA(IPSP)
• Norepinephrine /Noradrenaline
• Dopamine
• Serotonin

A classical neurotransmitter is released from vesicles from within the presynaptic knob in response to Ca2+ influx

• Chemical compunds packed in vesicles = nerutotransmitters. During synaptic transmission, release of these compounds includes different signals at post synaptic membrane and signal can be IPSP or EPSP depending on chemical

Question 2

Methamphetamine - P/meth/speed

1. Increases levels of what?
2. Blocks what?
3. Stimulates what?
4. Acts in what centre?

5 Highly what?

Answer 2

1. Increases levels of:

-NE (noradrenaline/norepinephrine)

-dopamine

-serotonin

2. Blocks reuptake (excess neurotransmitter in synaptic cleft - everything esle normal)
3. Stimulates fight, flight, fright response
4. Acts in reward centre - highly addictive

5 Highly neurotoxic (can cause damage to brain)

Question 3

• Almost all drugs target (highjack) what?
• Give me three examples

Answer 3

• Almost all drugs target (highjack) endogenous neurotransmitter systems (we make these too but not in the high concs that we ingest)
• Three examples:
  • Nicotine - nicotine receptors (in the brain)
  • Heroin - opioid receptors (endogenous endorphins peptides)
  • Tetrahydrocannabinol - cannaboid receptors (brain)

Question 4

Excitatory neurotransmitters - cause what?

There’s two of them - what do they activate etc?

Answer 4

EXCITATORY – cause DEpolarisation

• Acetylcholine–neuromuscular junction & brain (released by presynaptic cell)
  
  • activates _stimulus-gated Na+ channel_s (ionotropic receptors)
• Glutamate–most common excitatory neurotransmitter in CNS
  
  • ​activates stimulus-gated Na+ channels
  • activates stimulus gated Ca2+ channels

EXCITATORY POST SYNAPTIC POTENTIALS - EPSPs…due to the inflow of positive charged ions (Na+ and Ca2+) (so reaches the threshold of -59mV - temporary depolarisation)

Question 5

Inhibitory neorotransmitters - cause what?

One example - what does it activate etc?

Answer 5

INHIBITORY – cause HYPERpolarisation

• •GABA – gamma amino butyric acid, most common inhibitory neurotransmitter in brain.
  
  • activates _Cl– channel_s (ionotropic receptor)
  • activates K+ channels (metabotropic receptor)

INHIBITORY POST SYNAPTIC POTENTIALS - IPSPs…due to the inflow of Cl– or outflow of K+ (more negative than RMP so temporary hyperpolarisation)

Question 6

Input zone:

1. Exicatory synapse
   - excitatory neurotransmitter (pre-synaptic)
   - a lot of ____ channels (post synaptic)
   - local ______
   - IPSP or EPSP?
2. Inhibitory synapse
   - inhibitory neurotransmitter (presynaptic)
   - _____ and K+ channels (postsynaptic)
   - local ______
   - IPSP or EPSP?

Answer 6

1. Exicatory synapse
   - excitatory neurotransmitter (pre-synaptic) (e.g. Ach activates Na+)
   - a lot of Na+ channels (post synaptic)
   - local depolarisation
   - IPSP or EPSP?
2. Inhibitory synapse
   - inhibitory neurotransmitter (presynaptic)
   - Cl- and K+ channels (postsynaptic)
   - local hypolarisation
   - IPSP or EPSP?
   * Different types of synapses in input zone of one neuron

Question 7

Input zone - synaptic summation

-Local Synaptic Potentials (EPSPs and IPSPs) _____ – or ______ within the ______

Answer 7

Input zone - synaptic summation

• Local Synaptic Potentials (EPSPs and IPSPs) ADD UP – or SUMMATE within the Dendrites
• Those 50k synapses from neuron can be excitatory or inhibitory

Question 8

Two types of summation

1. Spacial Summation

Spatial: latin – _____, engl. space
Integration of inputs from ____ synaptic knobs (different localisation)

2. Temporal Summation

______ dependent – integration of inputs within a short time at the _____ synaptic knob

Answer 8

Two types of summation

1. Spacial Summation

Spatial: latin – space, engl. space
Integration of inputs from different synaptic knobs (different localisation)

• In same neuron - come together so if signal reaches threshold then passed on else no - “integrative signal”

2. Temporal Summation

Time dependent – integration of inputs within a short time at the same synaptic knob

• EPSP longer than action potential and adds up. Signals arrive in consecutive order. Determined by refractory period (the “short time” part)

Question 9

Appreicate this

Answer 9

Question 10

Action potential is transmitted when neuron is above threshold at the ______?

Answer 10

Action potential is transmitted when neuron is above threshold at the axon hillock

Question 11

Time dependent – integration of inputs within a short time at ____ _____ synaptic knob (______ place)

Answer 11

Time dependent – integration of inputs within a short time at the same synaptic knob (identical place)

Question 12

Appreicate this

Answer 12

As you can see, the more the action potentials ina short time, the more IPSPS that will make the membrane reach the threshold

Question 13

Appreicate this

Answer 13

Question 14

Types of network - Divergence and Convergence

Information from a single neuron may _____ to different brain regions (multiple neurons) or different body parts

Provides…
1. … opportunity to ______ signals (________)

2. … ______ (_______ control of muscles)

Answer 14

Information from a single neuron may DIVERGE to different brain regions (multiple neurons) or different body parts

Provides:

1. … opportunity to amplify signals (multiple reactions in response to one stimulus)
2. … few control points (precise coordinated control of muscles)

Question 15

Types of network - Convergence and Divergence

Information from multiple neurons may ______ on one single neuron (______!) that initiates a _____ response

Provides…

…redundancy - ‘Back-up’ route for the transmission of signals

Answer 15

Types of network - Convergence and Divergence

Information from multiple neurons may CONVERGE on one single neuron (Summation!) that initiates a single response

Provides…

…redundancy - ‘Back-up’ route for the transmission of signals

Question 16

If you increase [Na+] outside by addition of salt - what happens?

Answer 16

It makes neuron cell membrane more exictable (as well as the muscle cells) - driving force for Na+ entry will be greater; drives local EPSP’s if EPSP greater than -59mV —-> AP —–> Contraction (twtiching)

If Na+ increase - can cause depolarisation so action potential formed and contraction of muscle results

Question 17

What happens if you increase K+ levels outside?

Answer 17

• High K+ inside and high K+ outside –

no K+ movement through the channels will be possible

• Cells do not repolarise, not enough K+ leaves the cell (cardiac cells - no contraction, cardiac arrest)