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D1 Spring - Physiology > 1/29: Synapses > Flashcards

1/29: Synapses Flashcards

1
Q

What do chemical synapses involve?

A

Neurotransmitters that are released from the presynaptci cell and bind receptors to excite, inhibit, or modify post-synaptic cell

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2
Q

What is a one-way conductor?

A

Chemical synapse

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3
Q

What determines the function?

A

The receptor, NOT the neurotransmitter

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4
Q

What is the largest known neurotransmitter receptor family?

A

serotonin

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5
Q

What are the 3 steps of a presynaptic event?

A
  1. AP arrival at the synaptic terminal causes membrane depolarization (whether it’s myelinated or unmyelinated)
  2. Voltage gated Ca2+ channels open and move out the cell
  3. Ca2+ enters the synaptic terminal
  4. Exocytosis of vesicles filled with NT
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6
Q

The amount of Ca2+ that enters dictates the amount of _______ released

A

NT
- different things (Ca channel blockers) that decrease amount of Ca entry

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7
Q

There is a synaptic delay of at least ______ between the pre-synaptic depolarization and post-synaptic response

A

0.5ms

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8
Q

What is the synaptic delay due to?

A

Time for calcium entry for exocytosis
Presynaptic neurotransmitter release
Diffusion in the synaptic cleft
Postsynaptic receptor activation

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9
Q

What does the synaptic cleft/space allow one to gauge?

A

The complexity of a reflex pathway (number of synapses) by looking at the speed of the reflex

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10
Q

What are the two classifications of neurotransmitters?

A
  1. Small molecules
  2. Neuropeptides
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11
Q

How do small molecule NT act?

A

Rapidly
- elicit acute responses
- ex: acetylcholine, norepinephrine, dopamine, serotonin (5-HT), histamine, glycine, GABA, glutamate, nitric oxide (NO)

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12
Q

How do neuropeptide NT act?

A

Larger molecules, slower
- effects are slower, more potent, and more prolonged
- fewer neuropeptides produced and released
- ex: LH, ACTH, vasopressin, oxytocin, angiotensin II, substance P

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13
Q

What does substance P do?

A

Connects with inflammation and pain pathway

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14
Q

What do NT bind to to cause a response?

A

receptors on a post-synaptic cell

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15
Q

What is NT action terminated by?

A

A. Re-uptake of the NT by the pre-synaptic membrane
B. Inactivation of the NT by enzymes in the synapse (ex: acetylcholinesterase)
C. Diffusion of the NT away from the synapse (and receptors)

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16
Q

What are post-synaptic events?

A

NT binds to receptor on post-synaptic cell

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17
Q

What are the two types of post-synaptic receptors?

A
  1. Ionotropic receptors
  2. Metabotropic receptors
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18
Q

What do ionotropic receptors affect?

A

Ion channels

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19
Q

Binding of the ligand and the opening or closing the channel can:

A
  1. Change a cell’s membrane potential
  2. Stimulate muscle contraction and/or relaxation
  3. Stimulate secretion
  4. Act as a second messenger to alter cellular activity
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20
Q

What are metabotropic receptors?

A

G-protein coupled receptors (GPCR)

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21
Q

Alpha and Beta adrenoceptors bind _______ and __________

A

Norepinephrine and epinephrine

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22
Q

All 9 adrenocoreceptors are what kind of receptors?

A

G-protein coupled receptors coupled to different G-proteins

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23
Q

When adrenocoreceptors couple to different g-proteins, this leads to production of different ________

A

2nd messengers

24
Q

What are the resting membrane potentials for Na,Cl, and K?

A

Na = 61 mV
Cl = 69 mV
K = 86 mV

25
Q

What are the two types of graded potentials?

A
  1. Excitation
  2. Inhibition
26
Q

What are EPSPs due to?

A

Opening of Na+ and Ca channels
Closing of K+ and or Cl- channels

27
Q

What do EPSPs increase the likelihood of?

A

That threshold is reached

28
Q

What are IPSPs due to?

A

Opening of Cl- channels
Increased K+ conductance

29
Q

What do IPSPs decrease the likelihood of?

A

That an action potential is reached

30
Q

It is the _______ , not the ______, that determines the response produced

A

specific receptor; NT

31
Q

Summation is almost always necessary to produce an ______

A

AP

32
Q

What are the two types of summation?

A
  1. Spatial
  2. Temporal
33
Q

What is spatial summation?

A

Simultaneous EPSPs or IPSPs from multiple pre-synaptic neurons

34
Q

Spatial summation is added in _______

A

Space
- different spots on post synaptic neuron

35
Q

What is temporal summation?

A

Successive EPSPs or IPSPs from a single presynaptic nerve terminal

36
Q

Temporal summation is added in _______

A

Time

37
Q

Can a spatial and temporal summation occur at the same time?

A

Yes

38
Q

What is the duration of a postsynaptic potential?

A

Up to 15 msec

39
Q

Excitability of a neuron changes in response to:

A
  1. Synaptic input (pre and post synaptic)
  2. Prolonged activation
  3. Changes in membrane permeability, ion concentration, other chemicals
40
Q

What makes up the synaptic input?

A

A. Postsynaptic inhibition or excitation
B. presynaptic inhibition
C. Presynaptic facilitation

41
Q

What makes up prolonged activation?

A

A. Synaptic fatigue
B. long term potentiation (LTP)
C. Long term depression (LTD)

42
Q

What is presynaptic inhibition and facilitation due to?

A

Axo-axonic synapses

43
Q

What does presynaptic inhibition and facilitation change?

A

The amount of NT released into the synapse
(how much Ca2+ enters the synaptic terminal)

44
Q

What is an example of an excitatory neurotransmitter?

A

Glutamate

45
Q

What is an example of an inhibitory neurotransmitter?

A

GABA

46
Q

What is synaptic fatigue due to?

A

Less neurotransmitter available to be released

47
Q

Each successive stimulus is ________, but the response is progressively _______, due to ______

A

Identical; smaller; presynaptic change

48
Q

Long term potentiaion and long term depression occur in response to?

A

Repetitive synaptic activity and cause changes in synaptic strength that can last for days to weaks

49
Q

What is long term potentiation due to?

A

Memory and hippocampus involved in learning/memory
Learn and develop things over time
Enhancement

50
Q

What is long term depression?

A

Opposite of long term potentiation

51
Q

Long term potentiation is best studied at _____ synapses

A

Glutamate in the hippocampus

52
Q

Glutamate can bind to ______ and ______ receptors on the post-synaptic neuron?

A

AMPA and NMDA

53
Q

LTD is the opposite of LTP as it _______ synatic strength

A

Decreases

54
Q

What are changes that increase excitability?

A
  • hyperkalemis (up to 6mM)
  • hypocalcemia
  • alkalosis
  • caffein and theophylline
  • up-regulation of receptors
55
Q

What are changes that decrease excitability?

A
  • hyperkalemia (above 6mM)
  • hypokalemia
  • hypercalcemia
  • acidosis (can cause a coma, a coma depresses nerve excitability)(ex: diabetic DKA)
  • anesthetics (ex: lidocaine (block VG sodium channel and puts it in an inactive state))
  • down regulation of receptors
  • hypoxia
  • fatigue
56
Q
A

Yes

57
Q

Neurons A and B synapse with neuron X. If both neurons A and B release neurotransmitter in the synapse with neuron X at the same time, this is an example of _____.

A

Spatial summation

D1 Spring - Physiology (17 decks)

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