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Physiology > Synapses > Flashcards

Synapses Flashcards

1
Q

what determines the function of the synapse?

A

The RECEPTOR not the nt.

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2
Q

what are the three morphological types of chemical synapses?

A
  • axosomatic
  • axodendritic
  • axoaxonal
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3
Q

what is axosomatic?

A

where synapses terminate on neuronal cell bodies and tend to be INHIBITORY

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4
Q

what is axodendritic?

A

where synapses terminate on dendrites or dendritic spines (out pouching parts that make a connection with an axon) and tend to be EXCITATORY

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5
Q

what is axoaxonal?

A

where synapses terminate on an axon, often close to synaptic terminals and modulate the release of nt.

They can modulate the release of nt by regulating the amount of Ca2+ that enters.

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6
Q

What happens during a presynaptic event?

A
  1. AP arrives at the terminal causing membrane depolarization
  2. V-gated Ca2+ channels open (OUR GOAL)
  3. Ca2+ enters the synaptic terminal
  4. Exocytosis of vesicles filled with nt
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7
Q

what are they two classifications of nt

A
  1. small molecules

2. neuropeptides

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8
Q

what are small molecule nt?

A

they are FAST

  • elicit acute responses
  • ex: Ach, NE, Dopamine, Serotonin, Histamine, Glycine, GABA, Glutamate, NO.
  • these nt vesicles are typically “prepackaged and ready to go” that is why they are fast
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9
Q

what are neuropeptide nt?

A

they are SLOWER

  • effects are slower to be produced, more potent and do not need as much, and are more prolonged
  • produced in the cell body and transported down axon
  • LH, ACTH, GH, Vasopressin. oxytocin, angiotensin II, substance P
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10
Q

how can a NT action be terminated?

A
  • Re-uptake by the presynaptic membrane
  • absorption by glial cells
  • inactivation by enzymes in the synapse
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11
Q

where do nt bind to when released?

A
  • post synaptic receptors

- presynaptic membranes

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12
Q

what happens during post-synaptic events if its an ionotropic receptor?

A

ionotropic receptors: directly affects the ion channels to directly open or close them

It can then do one of the following:

  • change of a cells membrane potential
  • stimulates muscle contraction/relaxation
  • stimulate secretion
  • act as a 2nd messenger to alter cell activity
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13
Q

what happens during post-synaptic events if its an metobotrophic receptor?

A

nt binds to Gprotein coupled receptors

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14
Q

How do ESPS occur?

A
  • opening of Na+ channels
  • closing K+ and/or Cl- channels
  • depolarized graded potentials
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15
Q

How do ISPS occur?

A
  • opening of Cl- channels
  • increased K+ conductance through and increase of all channels
  • hyperpolarization of the membrane
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16
Q

what is summation of EPSP

A
  • it will allow for an AP to be fired if all 16+ synapses come together to depolarize a neuron. It is almost always necessary to have summation to produce an AP.
17
Q

What are the two types of summation

A

Spatial and Temporal

18
Q

Explain spatial summation:

A

simultaneous EPSP and IPSP from multiple pre-synaptic neurons
-can happen at different places but at the SAME TIME. Individually not enough but all together it will be.

19
Q

Explain temporal summation:

A

Successive EPSP or IPSP from a single presynaptic nerve terminal. One could be enough but will increase the amount of times it does it within one succession.

20
Q

excitability of a neuron can change in response to:

A
  • synaptic input (due to axo-axonic synapses)
  • prolonged activation
  • changes in membrane permeability, ion concentration, or other chemicals
21
Q

What are the 3 ways a neuron changes excitability in response to synaptic input?

A
  1. synaptic input
  2. prolonged activation
  3. changes in membrane permeability
22
Q

How can a post-synapse input change excitability

A
  • an inhibitory nt (like GABA) produces an IPSP that decreases post synaptic neuron from reaching threshold
  • an excitatory nt (like Glutamate) can cause an EPSP (depolarization) that increases post synaptic neuron from reaching threshold
23
Q

How can a pre-synapse input change excitability

A

a third neuron (axo-axonal neuron) can impact the excitatory neuron on how much it will release nt to the post synaptic neuron. It can decrease/increase the AP which then changes the Ca2+ entry which leads to more or less nt being released

24
Q

how can an axoaxonal neuron change AP for facilitation or inhibition?

A

facilitation: opening more Na+ channels
inhibition: increase Cl- conductance that reduces AP size

25
Q

how can an axoaxonal neuron change the nt release for facilitation or inhibition?

A

facilitation: increasing Ca2+ and more nt are released
inhibition: decrease of Ca2+ because of the increased Cl- conductance

26
Q

how can the excitability of a neuron change in response to prolonged activation?

A
  • synaptic fatigue
  • long term potentiation
  • long term depression
27
Q

explain synaptic fatigue

A

stimulus is identical but the response begins to get smaller because of a presynaptic change.
Meaning that the presynapse will be constantly activating it could run out of vesicles or have less response which changes the excitability of the neuron

28
Q

LTP stands for what

A

long-term potentiation

29
Q

LTP and excitability of a neuron

A

the post synapse changes (having more receptors) that allows the synapse to be more active

30
Q

LTD stands for what

A

Long term depression

31
Q

LTD and excitability of a neuron

A

LTD decreases synaptic strength. The lack of use of a synapse can decrease the strength

32
Q

How can hyperkalemia alter neuronal excitability

A

if 6 or less: increase excitability

if 6 or more: decrease excitability

33
Q

how can hypo and hypercalcemia alter neuronal excitability

A

hypocalcemia: increase excitability
hypercalcemia: decreaes excitability

having more Ca2+ impedes Na+ movement through channels so decrease excitability

34
Q

How can caffeine alter neuronal excitability

A

increases excitability

35
Q

how can alkalosis and acidosis alter neuronal excitability

A

alkalosis: (up pH) so less H+ –> increase excitability
acidosis: (down pH) so more H+ –> decreases excitability

(acidosis happens to diabetic pts: too much H+ and can go into coma)

Physiology (6 decks)

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