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Neurology > Class 2 > Flashcards

Class 2 Flashcards

1
Q

What is a Soma?

A

Spherical central part of the neuron that contains all of the
organelles.

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2
Q

What is an Axon?

A

Structure that is unique to neurons & highly specialized for transfer of information over distances in nervous system. Axons vary in length & diameter.

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3
Q

What is Axon Hillock?

A

Tapers away from soma to form initial segment of axon. Site at which action potentials initiate.

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4
Q

What is an Axon Terminal?

A

Small swellings where axon ends, where it comes in
contact with another neuron called a synapse.

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5
Q

What is Myelin?

A

Protective layer around the axon?

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6
Q

What are Nodes of Ranvier?

A

Small interruptions in myelin sheath exposing axonal
membrane

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7
Q

What are Axon Collaterals?

A

Are branches off of main axon, so that one neuron can send signals to multiple other neurons.

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8
Q

What are Dendrites?

A

Are extensions of the soma.

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9
Q

What is a Dendritic Tree?

A

All of dendrites of a neuron are called the dendritic tree.

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10
Q

What is a Dendritic Branch?

A

A single branch of the dendritic tree.

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11
Q

What are Neurites?

A

Number of axons & dendrites that exist on a particular neuron

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12
Q

Neurons can be classified based on how many neurites (axons and dendrites) that extend from the soma. What are the 3 classifications?

A
  1. Unipolar
  2. Bipolar
  3. Multipolar
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13
Q

What is Unipolar?

A

• Only one neurite extending from soma
• Always attached to sensory receptor that carry afferent information (to CNS)
• Cell body is part of dorsal root ganglia, cluster of neurons in dorsal root of spine
• Sensory receptors convert stimuli into action potentials (nerve impulses)

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14
Q

What is Bipolar?

A

Two neurites extending from soma (not as common)

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15
Q

What is Multipolar?

A

Three or more neurites extending from soma (most neurons of the brain).

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16
Q

What is a Synapse?

A

Where information gets transferred from one neuron to the other.

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17
Q

What is the Presynaptic Side?

A

Where the information is generally coming from.

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18
Q

What is the Postsynaptic Side?

A

Where the information is generally going to.

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19
Q

What is the Synaptic Cleft?

A

The small space that these two sides create, where
transfer of information occurs called synaptic transmission.

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20
Q

What is the process of synaptic transmission?

A
  1. Synthesis of NT & formation of vesicles
  2. Transport of NT down axon (towards axon presynaptic terminals)
  3. AP travels down axon via saltatory or continuous conduction.
  4. Many NTs are stored in vesicles in axon terminals until they are ejected into synaptic cleft. In most cases, release of NTs occurs through exocytosis caused by calcium entering terminal because of AP. Key symptom of hypocalcemia is tingling (paresthesia) in extremities, especially in hands & feet. When calcium drops too low, nerve cells struggle to operate properly.
  5. NTs attach to protein receptors in cell membrane of postsynaptic neuron. (Think “lock and key”). NTs can excite or inhibit postsynaptic neuron.
  6. Separation of NT molecules from receptor.
  7. Reuptake of NT. NTs are then recycled.
  8. Empty vesicles are transported back to cell body.
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21
Q

What are Action Potentials?

A

Dramatic redistribution of electrical charges across the membrane, or the way neurons “communicate with each other.”

22
Q

What is an Electrochemical Event?

A

Action potentials have both electro (positive &
negative charge) & chemical (sodium & potassium) properties that drive event to occur.

23
Q

What is the All or Nothing Principle of Action Potentials?

A

States that an action potential can only occur when membrane depolarizes to certain threshold. If threshold is not met, then action potential does not occur.

24
Q

What is a Membrane Potential?

A

Difference in charge {millivolts (mV)} of outside & inside of a neuron at any particular time.

25
Q

What is Resting Membrane Potential?

A

Neuron is said to be at rest when it is not depolarizing or firing. At rest, membrane potential of neuron is generally around -70 mV. Resting neuron has more potassium ions inside cell & more sodium ions outside cell. Resting neuron remains this way until there is stimulus.

26
Q

What are The Phases of an Action Potential?

A

• Hypopolarization
• Depolarization
• Overshoot
• Repolarization

27
Q

What is Hypopolarization?

A

Brief increase in membrane potential towards threshold

28
Q

What is Depolarization?

A

Drastic increase in membrane voltage, past threshold, due to influx of sodium ions via voltage gated sodium channels. This triggers nearby sodium channels to open as well, in a cascade event.

29
Q

What is Overshoot?

A

When the inside of cell becomes extremely positive

30
Q

What is Repolarization?

A

Potassium channels open, rushes in & makes inside of cell membrane potential more negative.

31
Q

What is Hyperpolarization?

A

Occurs when membrane potential decreases to that
below resting membrane potential. It is at this brief moment called refractory period where no action potential can occur, until it returns to “normal” resting membrane potential.

32
Q

Many axons are sheathed in______________.

A

myelin

33
Q

_____________ speeds up the conduction efficiency and speed.

A

Myelin

34
Q

Action potentials can propagate across an axon with or without myelin via?

A

• Continuous Conduction
• Saltatory Conduction

35
Q

What is Continuous Conduction?

A

Propagation of action potentials down an unmyelinated axon in continuous wave of depolarization.

36
Q

What is Saltatory Conduction?

A

Propagation of action potentials down a myelinated neuron from node of Ranvier, to node of Ranvier via “skipping,” or “jumping”. This occurs because sodium channels are concentrated in these nodes. This method retains more information, is a lot quicker, & uses less energy, making it overall more efficient.

37
Q

There are large number of neurotransmitters, detected by an ________________________.

A

even greater variety of receptors

38
Q

What is a neurotransmitter?

A

Chemical released by presynaptic neuron. Diffuses across synaptic cleft to postsynaptic neuron. Effect may be excitatory or inhibitory, depending on neurotransmitter and characteristics of receptors.

39
Q

What is an EPSP (excitatory post synaptic potential)?

A

Makes it more likely that an action potential will continue in post synaptic neuron. An EPSP makes it more likely that threshold of post synaptic neuron will be reached.

40
Q

What is an IPSP (inhibitory post synaptic potential)?

A

Makes it less likely that action potential will continue in post synaptic neuron.

41
Q

An IPSP __________________ the postsynaptic neuron, & an EPSP _______________ or _______________ the postsynaptic neuron.

A

• hyperpolarizes
• facilitates or hypopolarizes

42
Q

The output of a single neuron is not enough to cause a ____________________ or ____________________.

A

• postsynaptic neuron to fire
• prevent it from firing

43
Q

A typical neuron receives input from __________________________. Because each neuron has ____________________, this amounts to as many as 10,000 synaptic connections in most parts of the brain & up to 100,000 in the cerebellum.

A

• approximately one thousand
other neurons
• numerous terminals

44
Q

The ___________________ is the site on the soma of a neuron where the AP is initiated.

A

axon hillock

45
Q

What are the two types of summation?

A

• Temporal summation
• Spatial Summation

46
Q

What is Temporal Summation?

A

• Occurs when intense stimulation by one presynaptic neuron at the same synapse occurs in rapid succession.
• Effect of first potential does not have time to dissipate & succeeding potentials add to previous ones.

47
Q

What is Spatial Summation?

A

• Occurs when multiple excitatory signals stimulates various postsynaptic sites simultaneously

48
Q

Through temporal & spatial summation, the ________________ integrates its many excitatory & inhibitory inputs.

A

postsynaptic neuron

49
Q

If sum of all EPSPs & IPSPs reaches threshold, ___________________. If neuron does not reach threshold level, then ________________________.

A

• AP will result
• action potential will not occur

50
Q

Regulation of synaptic activity is produced by ___________________ & _______________________________.

A

• adjustment of neurotransmitter output
• changes in the number of sensitivity of postsynaptic receptors

Neurology (12 decks)

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