ZOO*3600 - CAP I > Theme 2 - Nerves > Flashcards

Theme 2 - Nerves Flashcards

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1
Q

Neuron

A

The anatomical and functional unit of the nervous system.

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2
Q

True or False: Neurons are continuous

A

False

Neurons are contiguous

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3
Q

The sympathetic and parasympathetic divisions work in ____ of each other

A

Opposition

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4
Q

Sympathetic

A
  • Usually stimulates, accelerates, or increases
  • Fight or Flight
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5
Q

Parasympathetic

A

Usually inhibits, slows, or decreases
- Rest and digest

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6
Q

What are the 4 Glial Cells

A
  1. Astrocyte
  2. Microglia
  3. Ogliodendrocyte
  4. Schwann cell
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7
Q

What 3 Glial Cells are part of the CNS

A

Astrocyte - Transport nutrients, remove debris, regulate synaptic neurotransmitter levels

Microglia - Remove debris and dead cells, immune responses

Ogliodendrocyte - Form myelin sheath

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8
Q

What Glial cell is part of the PNS

A

Schwann cell - forms the myelin sheath for motor and sensory neurons

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9
Q

What are the 4 Structure-Function Relationships of Neurons

A

Structure - Dendrites
Function: Signal Reception (input)

Structure: Axon Hillock
Function: Signal Integration

Structure: Axon
Function: Signal Conduction

Structure: Axon Terminals
Function: Signal Transmission (output)

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10
Q

Synapse

A

The connection between an axon terminal and target cell
- Target cells can be other neurons, muscle cells, secretory cells

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11
Q

Where can synapses be found?

A
  1. Dendrites/soma (receive signals
  2. Found at end of axon (send signals)
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12
Q

True or False: neural signals are unidirectional

A

True

always soma -> synapse

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13
Q

Afferent Neuron

A

Carries signal away from stimulus
- stimulus -> CNS

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14
Q

Efferent Neuron

A

carries signal to cause a response
- CNS -> effector

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15
Q

What does it mean when “neurons have resting membrane potential”

A

The inside of the cell has a different charge than the outside of the cell

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16
Q

Neurons are excitable meaning…

A

They can rapidly change their membrane potential
- Changes in membrane potential act as electrical signals

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17
Q

The distribution of an ion across an ion-selective membrane depends on two opposing forces:

A
  1. Chemical potential
  2. Electrical potential
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18
Q

Equilibrium Potential

A

The voltage difference across the membrane when the two forces acting on that ion are equal

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19
Q

What does the Nernst Equation calculate?

A

Equilibrium potential for single ions
- equilibrium potential is proportional to the ratio of concentrations of X across the membrane

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20
Q

The Goldman Equation

A

Calculates the final membrane potential from all the contributing ions
- membrane potential is proportional to the ratio of the ionic concentrations across the membrane and the permeability of the membrane to the ions

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21
Q

Why is Ca dropped from the Goldman Equation?

A

Permeability ti Ca2+ is so small and the membrane potential for Ca2+ is so low so its dropped from the eqn.

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22
Q

What ions potential is most influencial in the Goldman Eqn

A

K+ b/c permeability to K+ is 100x greater than to Na+

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23
Q

Why are the Goldman Eqn and Nernst Eqn ~equal when comparing K+ and Na+/K+ Pump

A
  • Cell membranes have higher permeability to K+ than to other ions
  • The Na+/K+ pump indirectly contributes to Vm by maintaining the high internal [K+]
  • K+ leak is main contributer to Vm
  • High intracellulat [K+] and high Pk
  • assymetiric concentrations of both ions across membrane
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24
Q

Neural Circuit

A

Structure: Neurons organized into functional circuits that rapidly conduct information

Function: Stimulus is converted into chemical and electrical signals that are carried rapidly through neuronal circuit

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25
Describe Neuronal Circuits in terms of their structure and function of components (3)
Structure: Sensory Neuron Function: Signal reception (input) Structure: Interneurons Function: Signal integration and conduction Structure: Motor Neuron Function: Signal transmission (output)
26
Information through neuronal circuits alternate between... (2)
Graded and all-or-none signals Electrical and Chemical signals
27
Graded vs All-or-none
Graded: magnitude of response is proportional to stimulus strength All-or-none: Response is invariant. Irrespective of stimulus strength.
28
Electrical vs. Chemical
Electrical: ions Chemical: Neurotransmitters
29
Ligand Gated ion channels
Convert chemical signals into electrical signals by changing th membrane potential
30
Graded Potentials
The electrical signals generated by ligand-gated ion channels in the dendrites and soma - Ligand binds to channel -> ions can now move across the membrane
31
True or False: Neurotransmitters can be released and used again
True
32
The magnitude of graded potentials is proportional to...
The stimulus strength - Ex. concentration of neurotransmitter
33
How can graded potentials depolarize the cell?
Via Na+ and Ca2+ channels
34
How can graded potentials hyperpolarize the cell?
Via K+ and Cl- channels
35
In graded potentials... Ions move ___ their electrochemical gradient Net movement stops when their ___ is reached
Down Equilibrium potential
36
Graded Potential Signals decay due to (2)
1. Membrane permeability: Leakage of ions across the membrane 2. Cytoplasmic resistance: Inherent resistance to current flown
37
Decremental Spread or Electrotonic Conduction
Signal magnitude decreases as it moves away from the source
38
Graded Potentials are ___-distance signals
short
39
What is required to fire an action potential?
Graded potentials in the axon hillock need to depolarize the membrane beyond the threshold potential
40
Sub-threshold graded potentials vs supra-threshold graded potential
Sub-threshold: Graded potentials do not initiate an action potential Supra-threshold: Graded potentials causes the axon to fire an action potential
41
Spatial Summation
Graded potentials from different locations can interact to influence the net change in membrane potential at the axon hillock.
42
Excitatory Signals vs Inhibitory Signals
Excitatory: Depolarize the membrane Inhibitory: Hyperpolarize the membrane
43
Temporal Summation
Graded potentials occurring at slightly different times can interact to influence the net graded potential.
44
Graded potentials are integrated to trigger___
Action Potentials
45
What are the Properties of an action potential? (5)
1. AP triggered when membrane potential at axon hillock reaches threshold potential 2. Once triggered it is an all or nothing response 3. Rapid changes to Vm caused by ions (not electrons) 4. AP does NOT require ATP 5. Ion concetration restored by NA+/K+ ATPase
46
Why is it useful for an action potential to end with neurons in a hyper-polarized state? (2)
1. If it stayed at threshold potential that means it would only take the tiniest gradient potential before the neuron fired 2. Disease state neurons don't enter the hyper-polarized state - epilepsy - causes abnormal firing
47
Describe the refactory period of an AP
- No AP can be triggered because the voltage-gated Na+ channels are in an inactivated state - It is harder to generate an AP because the membrane is hyperpolarized
48
Describe Patch-Clamp Recording (single chanel recording)
- Can isolate a single ion cannel and measure current - surrounding soln mimics the extracellular fluid - Negative pressure can control solution and movement by changing the bath
49
Describe the VG Na+ Channel (3)
1. Opens quickly 2. Inactivates quickly 3. Drives rapid reversal of membrane potential
50
Describe VG K+ Channel
1. Opens slowly 2. Stays open longer 3. Drives depolarization and after hyper-polarization - Lag time
51
What would happen if you electrically stimulate a resting neuron in the middle of its axon? Why is the movement of the AP in this scenario different from if you were to stimulate that neuron at the axon hillock?
This would create 2 action potentials that propagate in opposite directions along the axon - One would travel towards the cell body and the other toward the axon terminal - This would then trigger neurotransmitter release and synaptic transmission. Usually the refractory period would prevent the backwards propogation
52
Signal conduction can occur by... (4)
1. Passive Spread (electritonic) 2. Action potential 3. Saltatory Conduction 4. Chemical and electrical synapse
53
Axonal Conduction
A combination of electrotonic current flow and APs - Electrotonic current flow is much faster than APs - graded and can only travel short distances
54
What are the two factors affecting conduction speed?
1. The length constant 2. The time constant
55
Electrotonic conduction is enhanced by _____ and ____
High membrane resistance and low longitudinal (axoplasmic) resistance
56
Membrane voltage changes are reduced by high membrane ___ and ___
Capacitance and resistance
57
the time taken to reach Vm is described by...
The time constant
58
What are the two factors that affect the speed of propagation?
1. Axon myleination 2. Axon diameter
59
Mylination greatly increases ___ and decreases ___
λ, τ
60
Segmented myelination leads to...
Fast saltatory conduction of APs
61
Why does AP jump down myelinated axons?
Saltatory Conduction 1. Myelination prevents ions from leaking out through a membrane as the charge spreads 2. Charge spreads until it eaches the note of ranvier, which is packed with Na+ and K+ channels 3. Signals jump down the axon node to node - much faster than unmyelinaed - signal slows with each node
62
How does axon diameter affect the speed of propagation?
Increasing axonal diameter reduces longitudinal resistance, thereby increasing the length constant and conduction velocity
63
Capacitance
Ability of an object to store an electric charge
64
What are the three components of the signal transmission zone?
1. Presynaptic cell - carries signal to the synapse 2. Synaptic cleft - space between the pre and post synaptic cells 3. Postsynaptic cell - neurons, muscles, and endocrine glands
65
Neuromuscular Junction
The synapse between a motor neuron and a muscle cell
66
Electrical Synapse (5)
1. Rare in complex animals 2. Comparativly fast 3. bi-directional 4. Postsynaptic signal is similar to presynaptic 5. Excitatory
67
What is the principal advantage and disadvantage of an electrical synapse?
Advantage: Fast Disadvantage: Does not spread as far
68
Chemical Synapse
1. Common in complex animals 2. Comparatively slow 3. Unidirectional 4. Postsynaptic signal can be different 5. Excitatory or inhibitory
69
What is the principal advantage and disadvantage of a chemical synapse
Advantage: Versatility and flexibility Disadvantage: inherent synaptic delay
70
In a chemical synapse, AP frequency determines ___ and therefore how much neurotransmitter is released
Ca2+
71
Fast vs slow chemical synaptic transmission is differentiated by ___ not by their ___
Post-synaptic mechanisms, neurotransmitters
72
Describe fast chemical synapses
Act through ionotropic receptors found on the post synaptic membrane
73
Describe slow chemical synapses
Act through metabotrobic receptors found on the post-synaptic membrane
74
Excitatory Post-Synaptic Potentials move Vm ___ threshold potential vs IPSPs move Vm ___ from the threshold potential
toward, away
75
Plasticity
Change in response to experience
76
Neuronal Plasticity
Ability to change synaptic strength over time via both synaptic connections and functional properties of neurons
77
The synaptic transfer of information depends on its ___
History
78
What are the mechanisms of learning
Evolutionary and environmental adaption
79
evidence for learning is...
modification of behaviour through experience
80
Simple reflex behaviour habituates with repeated stimulation... How?
The brain learns the stimulation is unimportant - repeated exposure leads to decreased synaptic activity and weaker response - less sensitive
81
Simple reflex can be enhanced or sensitized in response to novel stimulus, How?
sensitization - involves a facilitating interneuron
82
Short-term habituation
Occurs from a reduction in neurotransmitter release by the sensory neuron
83
Short-term sensitization
Occurs from an increase in neurotransmitter release due to presynaptic facilitation
84
Long term sensitization
Can occur if kinase activity elicits changes in sensory neuron protein synthesis
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