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Physiology > Neurons > Flashcards

Neurons Flashcards

Cellular and Network Properties

1
Q

The multiple thin branch structures on a neuron whose main function is to receive incoming signals are

A

Dendrites

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2
Q

The axon is connected to the cell body by the

A

Axon hillock

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3
Q

Graded potentials may

A

Initiate an action potential, depolarize the membrane to the threshold voltage, hyper polarized the membrane, be called EPSPs or IPSPs

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4
Q

An inhibitory post synaptic potential (IPSP)would have what effect on the post synaptic neuron

A

Hyper polarizing, it would move the membrane potential way from threshold and make the cell less likely to fire an action potential

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5
Q

What is a synaptic potential called when it is depolarizing

A

Excitatory post synaptic potential

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6
Q

What is spatial summation

A

The combination of several nearly simultaneous graded potentials

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7
Q

What happens when a presynaptic neuron releases 1 IPSP and 2 EPSP

A

The IPSP counteracts the to EPSP,, creating an integrated signal that is below threshold. No action potential is generated at the trigger zone.

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8
Q

What is spatial summation

A

A combination of several nearly simultaneous rated potential. They originate at different locations on the neuron

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9
Q

The falling phase of the action potential in a neuron is primarily due to what process

A

Potassium flow out of the cell

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10
Q

In order to signal a stronger stimulus, action potentials become

A

Higher in amplitude and more frequent

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11
Q

What is the role of the sodium potassium exchange pump during an action potential

A

Helps reestablish the ion concentrations to their original compartments

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12
Q

What happens when voltage gated sodium channels of a resting neuron open

A

Na+ Enters the neuron, further depolarizing the cell

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13
Q

What 2 things will increase the conduction rate of action potentials

A
  1. increasing the diameter

2. Decreasing the resistance of the axon membrane to ion leakage

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14
Q

Why is calcium important at the synapse

A

Because it signals the exocytosis of the neuro transmitter

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15
Q

What does an excitatory post synaptic potential do

A

Depolarizes a neuron, increasing the likelihood of an action potential

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16
Q

What happens when a second EPSP arrives at a synapse before the effects of the first have disappeared

A

Temporal summation

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17
Q

What effect doTetrodotoxin have on the function of neurons

A

It blocks voltage gated sodium channels. The neuron is not able to propagate.

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18
Q

What are the 2 primary cell types found in the nervous system

A

Neurons and glial cells (aka as glia or neuroglia)

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19
Q

What are glia cells

A

They communicate with neurons and provide important biochemical and structural support

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20
Q

What is a neuron

A

It is a nerve cell that carries electrical signals rapidly and long distances

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21
Q

What makes neurons and muscle cells excitable tissues

A
  1. They transmit electrical signals rapidly in response to their stimulus
  2. The stimulus creates a high initial amplitude with a strong local current flow which reaches the trigger zone and depolarizes to suprathreshold.
  3. This leads to an action potential and excitability of the cell or tissue.
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22
Q

What is a graded potential

A

These are variable strength signals that travel over short distances and lose strength as they travel through the cell. They are used for short distance communication

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23
Q

How do cells create electrical signals

A

Ion movement creates electrical signals. A change in the concentration gradient or ion perm ability changes the membranes potential. This determines their ability to cross the membrane

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24
Q

What determines the strength of the graded potential

A

The size or amplitude are directly proportional to the strength of the triggering event. A large stimulus creates a strong potential. A small stimulus creates a week potential.

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25
Q

What kind of graded potential will opening potassium and chloride channels provide

A

Hyperpolarizing

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26
Q

What area will a strong enough grated potential reach

A

Trigger zone

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27
Q

What happens if a graded potential reaches threshold at the trigger zone

A

An action potential takes place

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28
Q

What happens if a graded potential does not reach threshold

A

An action potential does not take place. A graded potential dies out and a subthreshold graded potential occurs.

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29
Q

What happens when several graded potentials reach the axon hillock or trigger zone at the same time

A

If 2 or more graded potentials reach the trigger zone, the successive graded potentials created by those stimuli can be added to one another, increasing the chances of an action potential

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30
Q

Define and describe an action potential

A
  1. It’s an electrical signal of uniform strength that travels from a neurons trigger zone to the end of its axon
  2. An action potential is where voltage gated channels in axon membrane open sequentially as electrical current passes down an axon. Additional sodium enter the cell. This reinforces depolarize ation and the action potential doesn’t lose strength over distance. Action potential strength at the end are the same as it was at the beginning. They are an all-or-none phenomenon.
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31
Q

Does the strength of a grated potential influence the amplification of an action potential

A

No.

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32
Q

How is a graded potential different from an action potential

A
  1. Graded potential requires an input signal
  2. It has mechanical, chemical, and voltage gated channels
  3. Hyperpolarize
  4. Signal strength can be summed up
  5. No minimum is required to initiate
  6. Decreases in strength as it’s spreads out from point of origin and, has an increased ion leak

Action Potential

  1. Regenerates a constant conduction signal
  2. Only volted gated channels
  3. Can only depolarize
  4. Requires a threshold stimulus to initiate
  5. There’s a refactory period
  6. Decreased ion leak
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33
Q

What is the purpose of the absolute refractory period

A

It ensures one way travel of action potential. Action potentials moving from trigger zone to axon terminal cannot overlap and cannot travel backward. It allows for a 1-2 second delay for Na+ channels to reset to resting positions. A second action potential cannot occur before the 1st has finished no matter how large the stimulus.

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34
Q

What is the purpose of a relative refractory period

A

It limits the rate at which signals can be transmitted down a neuron. (It follows the absolute refractory period. Some sodium channel gates have reset, potassium channels are still open. The sodium channels that have not quite returned to their resting position can be reopened by a stronger than normal graded potential.)

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35
Q

Why can a greater than normal stimulus trigger an AP during the relative refractory, but not during the absolute refractory.

A

Because sodium channels are still opened and haven’t returned to their resting position during a relative refractory period. During an absolute refractory period sodium channels are in activated and cannot open again so soon

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36
Q

How does one neuron transmit information about stimulus intensity to the next neuron if all action potentials are identical in strength? How is stimulus coded by AP?

A

Signal strength is coded by frequency of action potential. A stronger stimulus will result in a burst of action potentials. The ion concentrations are not altered by very much and resetting the concentrations is fast but the next action potential can be initiated even before the potential is completely reset.

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37
Q

What things can conduct a faster AP and what does this do?

A

A larger neuron and myelinated neuron. More NT released

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38
Q

What does conduction ensure

A

That electrical energy is regenerated so that the electrical signal does not lose energy over distance like graded potentials

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39
Q

3 factors that affect the speed of conduction of an AP

A

Cable properties

  1. Diameter of axon, the larger the axon, lower its resistance to ion flow
  2. The resistance of an axon membrane to ion leakage out of cell-more leak resistant–> faster AP
  3. Myelinated create high resistance wall preventing ion flow out if cytoplasm–> increasing conduction
40
Q

What factor has a most significant impact on the rate of human nerve impulses

A

Myelinated neuron

41
Q

Do the nodes of ranvier in PNS axons have high or low concentrations of voltage gated sodium and potassium channels on

A

High

42
Q

What is saltatory conduction

A

Each node has a increased concentration of voltage gated sodium channels into the axon. The sodium entering the node reinforces the depolarization and restores the amplitude of AP as it passes node to node. This allows the jump of AP from node to node .

43
Q

What happens to conduction through axons that have lost their myelin? give an example

A

This slows conduction of AP. The current leaks out of an insulated regions between nodes. When the depolarization reaches the node it may no longer be above threshold. Conduction fails. An example is multiple sclerosis.

44
Q

What happens to AP conduction in a neuron whose voltage gated sodium channels have been blocked

A

Sodium cannot enter the cell, de depolarization may not be strong enough to reach the threshold resulting in a failed AP

45
Q

What happens to the likelihood of firing an action potential when that extra cellular potassium increases

A

It increases.This shifts the resting membrane potential of a neuron closer to threshold and causes the cells to fire AP in response to smaller graded potentials.

46
Q

Explain how hypokalemia decreases neuronal excitability

A

The resting membrane potential of the cell hyper polarizes moving farther from threshold

47
Q

Explain how exocytosis is initiated

A

In the axon terminal voltage gated calcium channels open in response to depolarization and calcium moves from the ECF to the cytoplasm. The movement of calcium is a signal that initiates exocytosis.

48
Q

What happens to the cell and to the membrane when chemically gated chlorine channels on a post synaptic neuron open

A

Chlorine moves into the cell and this movement hyperpolarizes the membrane

49
Q

How is the synaptic cleft cleaned up to end signal transmission

A
  1. Removal from cleft through receptor mediated endocytosis on the post synaptic membrane
  2. NT are inactivated by enzyme acetylcholinesterase
  3. NT removed from cleft by endocytosis by presynaptic cell: serotonin
  4. Remova6from ECF by transport back into presynaptic cell or adjacent neurons or glia
50
Q

What are the 2 efferent pathways

A

Somatic and Autonomic

51
Q

What are the divisions of Autonomic pathways

A

Sympathetic and parasympathetic

52
Q

What does the autonomic efferent pathway control

A

Heart, smooth muscle, glands and adipose tissues

53
Q

What is the main role of the parasympathetic division

A

Resting and digesting (breaks)

54
Q

What is the main role of the sympathetic division

A

Fight, flight, and fright (gas pedal)

55
Q

What does the CNS consist of

A

Brain and spinal cord, and ganglia

56
Q

What does the PNS consist of

A

Axons of efferent neurons and afferent neurons

57
Q

What are the 3 parts of the PNS

A

Autonomic, somatic, enteric

58
Q

What are the 3 functional types of neurons and what must they do to create an action potential

A
  1. Sensory
  2. Motor
  3. Interneurons
    Must have graded potential that meets threshold
59
Q

Function of dendrites

A
  1. For input of information ( listeners)
  2. Usually Multiple
  3. involved in learning, memory and some degenerative diseases
60
Q

Function of axons

A

1.For output communication (talking)
(Single)
2. Main location of NT production

61
Q

Sensory neuron

A

(Afferent) Relay information from sensory cells to CNS

62
Q

Interneurons

A

Integrate the information coming from many neurons. They are located in the CNS

63
Q

Motor neurons

A

( efferent) somatic or autonomic, carry the response signal out of CNS to effector tissues

64
Q

What is the NT transport mechanism

A

Located in the axon
Slow transport via cytoplasmic flow
Fast transport via motor-like vesicles and microtubules (like train tracks)

65
Q

Explain Neurotransmitter transport

A
  1. Peptides synthesized on RER and packaged by GA
  2. Fast axons transport walks and mitochondria along microtubules network
  3. Vesicles contents released by exocytosis
  4. Synaptic vesicle recycling
  5. Retrograde fast axonal transport
  6. Old membrane components digested by lysosomes
66
Q

Do neurons make ATP

A

No, they get it from glial cells

67
Q

What influences the permeability of a neuron

A

Channel proteins

  1. The amount of active channels
  2. The conductance of the channel (gating or isoform)
68
Q

When is a current generated

A

When ions flow

69
Q

Neurotransmitters are also

A
  1. Ligands that bind with ligand gated channels on next cell
  2. Has low affinity
  3. Is a chemical signal
  4. Common in input signals
70
Q

What happens when an axon is damaged

A

The section attached ro cell body will continue to live. The section of the axon distal to the injury will begin to disintegrate. Schwan cells will start to aggregate and create pathway to allow axon to repair proximal to cell body

71
Q

What is a nerve signal

A

A change in membrane potential

72
Q

In a neuron, when is a change in permeability created

A

When channels are activated and the distribution of ion changes creating a new state of disequilibrium leading to action potential or graded potential

73
Q

The strength of a GPis dependent on what

A

How long channels are open and

How much ligand there us available

74
Q

What will cause a localized depolarization

A

Excitatory potentials, usually due to increased permeability to Na+

75
Q

What will cause a localized hyperpolarization

A

Inhibitory potentials, usually due to increased permeability to K+ ors Cl-

76
Q

How does impulse get generated

A

Ther change in potential within proximity to a voltage gated Na+ channel must exceed threshold

77
Q

What is the key to an AP

A

Voltage gated channels.

78
Q

What is a synapse

A

Junction between a neutron and another cell

79
Q

What takes place at the synapse

A
  1. Location of information transfer between cells

2. Electrical signal(AP) is converted to a chemical signal

80
Q

What leads up to NT release

A
  1. AP reaches the axon terminal
  2. Change in membrane potential opens voltage gated Ca+++ channels
  3. Ca+++ influx causes the vesicles carrying NT (neurocrine) to fuse with presynaptic membrane
  4. NT is released into synaptic cleft
81
Q

Define neurocrine

A

A generic name for signal molecules that leave the axon

82
Q

Examples of neurocrines

A

Neurotransmitters
Neuromodulators
Neurohormones

83
Q

What are the 7 chemical charmed of Neurocrines

A
  1. ACh
  2. Amines
  3. Amino acids
  4. Peptides
  5. Purines: nucleotides (AMP & ATP)
  6. Gases: NO
  7. Lipids
84
Q

Receptor types

A

Many different kinds

Either ligabd-gated or G- protein coupled receptors

85
Q

Cholinergic receptor AKA

A

ACh receptor

86
Q

Nicotinic receptor

A 
ACh 
Agonist
Found on skeletal muscle, autonomic sympathetic division in CNS
Ligand gated channel
Activation -->Na+ influx
87
Q

Muscarinic receptor

A 
ACh 
Agonist 
Autonomic parasympathetic division  and CNS
Rceptir is G- protein coupled
Multiple cellular responses
88
Q

Adrenergic receptor

A

Bind epi or Norepi
2 classes–> alpha or beta
G-coupled, but 2 different 2nd msgrs pathways

89
Q

Glutaminergic receptor

A

Main excitatory NT in CNS
Also neuromodulator
2 classes–> AMPA & NMDA–> Cation flow allowed
Complicated signal transduction pathways

90
Q

Which cell responses will be fast

A

If channel gated by binding of NT

Whether for responses requiring excitability or inhibition

91
Q

What do slow cell responses involve

A

Complicated second messenger systems and can result in changes in the proteins in the cell:
learning

92
Q

Spatial summation

A

Addition of all the EPSP and IPSP that one cell receives in one location on the neuron. The small changes are localized so they are added spatially

93
Q

Temporal summation

A

Addition of all the EPSP and IPSP that one cell recieves over a period of time. It can mount up

94
Q

Neuromodulator

A

Released by adjacent neurons at synapses and can affect the release or activity of the NT

95
Q

Long term potentiation

A

Activity at synapse results in long term changes in the number of connections or quality of connections–>memory or learning
Some NT upregulat receptor–> increasing post synaptic sensi6to NT

Physiology (9 decks)

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