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Pharmacology > Neuronal responces > Flashcards

Neuronal responces Flashcards

1
Q

Name the 6 locations of axons

A
  1. Axosecretory: axon terminal secretes directly into the blood stream
  2. Axoaxonic: Axon terminal secretes into another axon
  3. Axodendritic- Axon terminal ends on a dendritic spine
  4. Axoextracellular: Axon with no connection secretes into extracellular fluid
  5. Axosmotic: Axon terminal ends on soma
  6. Axosynaptic: Axon terminal ends on another axon terminal
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2
Q

Describe the process that occurs after an action potential arrives at the axon terminal

A
  1. Action potential reaches axon terminal
  2. Voltage gated Ca2+ channels open
  3. Ca2+ enters the cell
  4. Ca2+ signals to vesicles
  5. Vesicles move to the membrane
  6. Docked vesicles release neurotransmittersby exocytosis
  7. Neurotransmitters diffuses across the synaptic cleft and binds to receptors
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3
Q

Effect of ACh neurotransmitters at the neuromuscular junction?

A

At the neuromuscular junction (NMJ) on skeletal muscle release of ACh neurotransmitter always causes an action potential
Only excitatory inputs

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4
Q

What happens at other synapses not the NMJ? What causes an action potential at these regions?

A

There are excitatory and inhibitory inputs. An action potential is only produced if the sum of all the inputs is enough to depolarise the neurone above threshold

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5
Q

Describe the mechanism of Excitatory Post Synaptic Potential’s

A 
Increased Na+ permeability 
e.g. Nicotinic ACh receptor binds ACh
Opens cation channel
Influx of Na+ depolarises membrane 
Directly gated ion channel
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6
Q

Describe the mechanism of Inhibitory Post Synaptic Potential’s

A

Increased K+ permeability or increased Cl- permeability
e.g. Muscarinic ACh receptor
G-protein coupled

Acts via 2nd messenger:
Indirect: Opens K+ channel
e.g. GABAA receptor
Opens Cl- channel: direct

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7
Q

What is Sub-threshold stimuli

A

If a synapse in stimulated twice but the EPSPs do not overlap then threshold is not reached
No action potential fired

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8
Q

What does an IPSP do?

A

hyperpolarize the post-synaptic neuron

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9
Q

What happens when IPSP and EPSP occur at the same time?

A

they cancel each other out
No change in membrane potential
No action potential

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10
Q

Which receptors does ACh use? What type of receptors are they? Where are they located?

A

nicotinic receptors and muscarinic receptors

Ligand gated ion channels

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11
Q

What type of receptor is nicotinic receptors? Name where it could be found

A

Ligand gated sodium channel
Always excitatory
Skeletal muscle

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12
Q

What type of receptor is muscarinic receptors

? Name where it could be found

A

It is a G protein-coupled receptor
Used in the parasympathetic nervous system to turn things off (inhibitory)
Located on cardiac mucles. Hyperpolarizes cardiac muscle to slow it down

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13
Q

Describe the main properties for ligand gates ion channels

A

Ionotropic: very fast: milliseconds

Opens pore for ions: Na+, K+, Ca2+, Cl-

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14
Q

Describe the main properties for G-protein coupled receptors. How do they work?

A 
Metabotropic: response in seconds: slow
2nd messenge (external signal) binds to a GPCR. Causes a conformational change in the GPCR. GCPR then activates a G protein which affects enzymes
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15
Q

What do G proteins bind to?

A

nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP).

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16
Q

How many neurotransmitters do most neurons release? What is the exception?

A

2 or more different neurotransmitters (different vesicles)

NMJ only releases and responds to 1

17
Q

Main features of Ligand gated ion channel: Ionotropic receptors

A
  1. Excitaory
  2. Allow the entery of sodium from synaptic cleft to initiate voltage change post ACH binding
  3. Found in peripheral nervous system (all skeletal and Ans ganglia)
  4. Also found in CNS
  5. Nicotinic receptors
18
Q

What are the main CNS neurotransmitter? What type receptor does it use?

A
  1. Glutamate
    Uses either inotropic or metabotropic receptors
  2. GABA
    Ionotrophic recepto
    Inhibitory (hyperpolarises)
19
Q

What is a main similarity between ACH and Glutamate

A

They both use Ligand gated on channel receptors and G protein coupled receptors

20
Q

Name for Glutamate ligand gated ion channel (Ionotropic)? Describe function

A

NMDA and non-NMDA receptors
Excitatory- allow entry of Na+ or a little Ca++
Cause inside of cell to be more positive (depolarised) to stimulate and action potential

21
Q

Function and mechanism of GABA

A

GABA opens Cl- channel
Hyperpolarises the membrane
Causes a calming effect

22
Q

What happens when Benzodiazepines bind to GABAA receptor?

A

causes a structural change so channel stays open for longer.
Allows more Cl- to move through the channel into the neuron and hyperpolarises the neuron.
Sedative, sleep-inducing, anxiolytic

23
Q

Function of Benzodiazepines? Which neurone do they act on?

A

Sedative

GABAa receptor?

24
Q

Main structural feature of G protein coupled receptor? How many of these receptors is found in the human genome?

A

7 transmembrane segments

800

25
Q

Second messenger molecules used in G protein excitatory receptor

A

IP3 and DAG

26
Q

Second messenger molecules used in G protein inhibitory receptor

A

cAMP

27
Q

What type of receptor are G coupled protein receptors? Give an example Neurotransmitter which uses it

A

metabotropic receptors

Glutamate

28
Q

Schematic diagram for G coupled protein receptor activity

A

GCPR—-G protein (intracellular)—-Enzyme—2nd messenger

29
Q

Function of 2nd messenger in GCPR

A

They open or close an ion channel

30
Q

What is the over all function of 2nd messengers? Name the 3 different types and give examples for each

A
  1. transmit and amplify signals from receptors to downstream target molecules
    3 main types
  2. Hydrophilic water soluble:
    IP3, cAMP, cGMP and Ca2+
  3. Hydrophobic water insoluble: DAG and PIP3
  4. Gases: NO, CO and ROS
31
Q

What strengthens synapses? And how?

A 
Sleep- Strengthens synapses after learning
Shrinks spines (on dendrites) that are not being used to allow for more new spines to form
32
Q

How are Receptors modulated by other neurotransmitters?

A

Metabotrophic glutamate activation increases the amount of GABA receptor accumulation
Iontrophic glutamate increases GABA receptor dispersion (less localised

GABA and glutamate are opposing pathways. keep excitation and inhibition balanced in the brain by adjusting the location of GABA a receptors

33
Q

What is adaptation and what is its purpose?

A

Purpose- prevents sensory overload
Adaptation occurs when the neuron decreases the firing rate (receptor potential) with constant stimulus (generate potential decays) (action potential has been generated for some time

34
Q

Describe what slow and rapid adaption is and give examples for each

A

Slow adaption- olfactory system
- Good for coding intensity of a stimulus for entire duration

Rapid adaptation- pacinian corpuscles
-Good for coding changes in stimulus intensity but not duration

35
Q

Which skin receptors are slow adapting? Name there function

A

Merkel cells- Pressure texture

Ruffini endings- Stretching of skin

36
Q

Which skin receptors are rapid adapting? Name there function

A

Meissner corpuscles- Light touch

Pacinian corpuscle- Vibration

37
Q

Can the intensity of an action potential change?

A

No only the frequency

Pharmacology (7 decks)

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