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Human Anatomy & Phisiology - Jason > L20 Signal Transmission > Flashcards

L20 Signal Transmission Flashcards

1
Q

How is the myelin sheath created?

A

By neuroglial cells

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2
Q

What are the two types of axons?

A

1) Unmyelinated
2) Myelinated

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3
Q

How does unmyelinated axons influence propagation?

A
  • Depolarization and repolarization occurs across entire length patch by patch
  • Continuous propagation
  • Very slow ~1meter/sec in shorter axons
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4
Q

How does myelinated axons influence propagation?

A
  • Myelin prevents ion leakage
  • Membrane proteins responsible for adjusting membrane potential are found at the Nodes of Ranvier
  • Signals travel much faster since depolarization jumps from node to node
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5
Q

What is saltatory propagation?

A
  • Very quickly
  • Jumping conduction
  • 18-140 meters per second
  • In all axons (sensory and motor neurons)
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6
Q

What types of myelinated axons do we have?

A
  • Type A
  • Type B
  • Type C
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7
Q

Which type of axons are myelinated?

A

Typa A axons ( most myelinated conduct signals very fast)
Type B axons ( less myelinated then A)

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8
Q

Which type of axons are unmyelinated?

A

Type C axons
Conduct singlas more slowly

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9
Q

What are the roles of the fastest axons?

A

Conduct position and balance signals

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10
Q

What are the roles of the slower axons?

A

Conduct temperature and pain signals instructions to autonomic effectors

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11
Q

What is neuronal communication?

A
  • Nerves talk to each other and to effectors accros synapses
  • Sensory neurons and interneurons pass their signals onto other neurons
  • motor neurons synapse onto somatic and autonomic effectors
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12
Q

What happens at a synapse?

A

and electrical signal is converted into a chemical signal via neurotransmitter release

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13
Q

What are neurotransmitters?

A

Chemicals stored in synaptic vesicles and released by a neuron at a synapse into a synaptic cleft

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14
Q

What are the types of neurotransmitters?

A

Acetycholine (Ach)
norepinephrine/noradrenaline (NE)
Other, less common neurotransmitters include: dopamine, GABA, serotonin, nitric oxide (gas), and carbon monoxide (gas)

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15
Q

The cholinergic synapse releases which neurotransmitter?

A

Acetycholine (Ach)

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16
Q

The adrenergic synapse release which neurotransmitter?
Broken down by acetycholine esterase

A

norepinephrine/noradrenaline (NE)
These are broken down by monoamine oxidase

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17
Q

What are the components of a synapse?

A
  • Presynaptic membrane
  • Synaptic cleft
  • Postsynaptic membrane
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18
Q

What is the first step of a electrical signal converting into a chemical signal (consider it a cholinergic synapse)

A

1) Arrival of an action potential at axon terminal

19
Q

Second step of a electrical signal converting into a chemical signal?

A
  • Presynaptic membrane is depolarized , causing voltage gated calcium channels to open
  • Ca2+ moves down its conc. gradient into the cell
  • Triggers exocytosis of synaptic vesicles full of neuro transmitter
20
Q

Step 3 of a electrical signal converting into a chemical signal?

A
  • Neurotransmitter diffuses across the synaptic cleft
  • Binds to chemically- gated Na+ channels on postsynaptic membrane (causes postsynaptic membrane to depolarize)
  • If this graded potential is strong enough to reach threshhold, an action potential is propagated
21
Q

Step 4 of a electrical signal converting into a chemical signal?

A
  • Neurotransmitter resorbed into presynaptic cell
  • Broken down by acetylcholine esterase (enzyme)
  • When neurotransmiter is removed, ready to respond to another event.
22
Q

What are the two types of effect neurotransmitters can cause?

A

Excitatory effect (depolarize)
Inhibitory effects (hyperpolarize)

23
Q

Which channels and neurotransmitters are correlated to excitatory effects (depolarize)

A

-Chemically gated Na+ channels
- Ach, NE, and dopamine

24
Q

Which channels and neurotransmitters are correlated to inhibitory effects (hyperpolarize)

A
  • Open chemically gated K+ channels
  • GABA, serotonin, and dopamine
25
Q

What can change synaptic activity?

A

External compunds

26
Q

What happens with medication and drugs that cross the blood-brain barrier?

A

Affects the nervous system commonly work at the level of the synapse

27
Q

What do selective serotonin reuptake inhibitoes do? (SSRIs)

A
  • prevent serotonin from being resorbed
  • Helps relieve symptons of depression
28
Q

What does cocaine do?

A
  • Inhibits removal of dopamine from excitatory synapses
  • Leads to a feeling of euphoria and alertness
29
Q

What does MDMA do?

A
  • Increases the release of serotonin, NE, and dopamine from presynaptic neurons and prevents their reuptale
  • Leads to symptoms of euphoria, alertness, and increased empathy
30
Q

What are neuromodulators?

A
  • Small peptides
  • Released from a neuron into a synaptic cleft
  • Alters responsiveness of a presynaptic or postsynaptic cell
31
Q

How do neurdomodulators alter neuronal responsiveness?

A
  • Changes how many synaptic vesicles are released by presynaptic
  • How postsynaptic cells respond to the neurotransmitter
32
Q

Give examples for neuromodulators and how they work

A

Endorphins
Ex: endogenous opioids, opium, moprhine, and heroic act as pain relievers by inhibiting the release of neurotransmitters in pain circuits.

33
Q

The activity of a neuron depends on the balance between?

A

the sum of excitatory and inhibitory signals
(Postsynaptic cell may have synapses with axon termini of multiple presynaptic cells)

34
Q

What are the postsynaptic potentials?

A
  • Excitatory postsynaptic potentials (EPSP)
  • Inhibitory postsynaptic potentials (IPSP)
35
Q

What is EPSP

A

A graded potential that depolarize the postsynaptic cell

36
Q

What is IPSP

A

Graded potential that hyperpolarize the postsynaptic cell causing it to become refractory

37
Q

What can the combination of EPSP and IPSP do?

A

Prevent a cell from reaching threshold

38
Q

What does EPSPs do ?

A

open chemically gated Na+ channels, causing depolarization towards -55mV

39
Q

What do IPSPs do?

A

Open chemically gated K+ channels, causing hyperpolarization towards -90mV, thus requiring a greater stimulus to reach threshold

40
Q

How does a cell reach threshold?

A
  • A single strong EPSP can depolarize to threshhold
  • Several small additive EPSPs
41
Q

What is temporal summation?

A
  • combination of many small graded potentials, following each other very quickly at a single synapse (causes enough Na+ to reach threshhold)
  • IPSPS can also act like this but lead to hyperpolarization
42
Q

What is Spatial summation?

A
  • Combination of many small graded potentials arriving simultaneously at different synapses on the same neuron
  • IPSPs can also act like this but they lead to hyperpolarization
43
Q
A

Human Anatomy & Phisiology - Jason (6 decks)

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