2.2 Neurophysiology Flashcards
1
Q
Neurons are highly
A
irritable
2
Q
Plasma membranes are peppered with a variety of
A
ion channels
3
Q
two types of channels
A
- passive or leakage channel (always open)
- active or gated channel
4
Q
two types of gated channel
A
- chemically gated channels
- voltage gated channel
5
Q
Body is electrically _____. But there are small differences in electrical charge between inside and outside of cell membranes due to differences in __________ on inside and outside of cell membrane.
A
neutral;
+ and – ions
6
Q
differences in charge = _________
A
potential (stored energy)
7
Q
resting cells (all cells in body) have potential difference (-50 to -200 mV)
A
membrane potential
8
Q
average muscle and nerve cells membrane potential
A
-70 mv
9
Q
Resting Membrane Potential is in _______ state
A
polarized state
10
Q
3 major processes of Resting Membrane Potential
A
- Different kinds concentration of ions inside and outside the cell membranes
- The differential permeability of the plasma membrane to Na+ and K+ ions
- The operation of the sodium-potassium pump
11
Q
There are different kinds and concentrations of ions inside and outside cell membranes: there are more ________ ions inside cell (especially ________)
A
negative ions, especially proteins
12
Q
Both Na+ and K+ can diffuse across cell membrane by ________ via leakage channels
A
facilitated diffusion
13
Q
In resting membrane potential, ___+ is more permeable than ___+
A
K+ > Na+
14
Q
a change in resting membrane potential can be produced by anything that changes _________
A
membrane ion permeability (opens or closes ion gates)
15
Q
Two kinds of potential changes
A
- Graded potentials
- Action Potential
16
Q
- local phenomenon, signal over short distances
- small to large changes in membrane potential due to opening and closing of chemical gates
A
Graded potential
17
Q
membrane potential decreases
A
- Depolarization
18
Q
membrane potential increases
A
- Hyperpolarization
19
Q
true or false
Graded potentials are given different names depending on where they occur and the functions they perform
A
True
20
Q
What do you call the graded potential in receptor region of dendrites and cell bodies of neurons? What are the two types?
A
Postsynaptic potentials
- Excitatory postsynaptic potential (EPSP)
- Inhibitory postsynaptic potential (IPSP)
21
Q
- local depolarization occurs and response stimulatory
- depolarization might reach threshold producing an action potential and cell response
A
Excitatory postsynaptic potential (EPSP)
22
Q
- local hyperpolarization and response inhibitory
- decrease action potentials by moving membrane potential farther from threshold
A
Inhibitory postsynaptic potential (IPSP)
23
Q
True or False
The EPSP is an all-or-none response.
A
False
The EPSP is not an all-or-none response but is proportionate in size to the strength of the afferent stimulus
24
Q
Two types of summation of post-synaptic potentials
A
Temporal and Spatial Summation
25
summation of EPSP’s or IPSP’s due to repeated stimulation by one neuron
Temporal Summation
26
summation of EPSP’s or IPSP’s due to stimulation by more than one neuron simultaneously
Spatial Summation
27
- long-distance signals
- a rapid, all-or-none change in the membrane potential, followed by a return to the resting membrane potential
Action potential
28
In action potential, there is a ______ depolarization and polarization of membrane due to sequential opening and closing of several voltage gates and active transport
complete
29
what cells can generate action potential
neuron and muscle cells only
30
how fast is an action potential
10ms
31
true or false
Do not decrease in strength with distance
true
32
In a neuron, a transmitted action potential is called
nerve impulse
33
Only _____ are capable of generating action potentials
axon (axon hillock)
34
three phases of action potential
1. depolarization
2. repolarization
3. undershoot
35
5 steps of action potential
1. Resting state
2. Depolarization
3. Rising phase of the action potential
4. Falling phase of the action potential
5. Undershoot
36
How does depolarization happens in the membrane?
due to the Na+ influx through Na+ channels that opens due to a stimulus
37
During the rising phase of action potential, most Na+ channels open while K+ channels ____?
remain closed
38
During falling phase of action potential, most Na+ channel close, blocking Na+ influx and K+ channels _____ which again makes the inside of the cell negative.
open
39
what step does the membrane return to its resting membrane phase?
undershoot
40
During action potential, _____ is more permeable than ______
Na+ is more permeable than K+
41
- in the interval from the onset of the action potential until repolarization is about one-third complete, no stimulus can elicit another response
- to ensure that **each action potential is separate**
- to enforce **one-way transmission**of the AP
the dead phase (absolute refractory phase)
42
each action potential has the same amplitude independently from the strength of the stimulus
all or none
43
a second action potential cannot occur during this period
refractory period
44
During the ________, it is possible to generate a second action potential, but only if the stimulus is stronger than usual. Is important for regulating the frequency of action potentials and allowing the neuron or muscle cell to respond to stronger stimuli.
relative refractory period
45
is like a fast and efficient way for nerve signals to travel through jumping with the help of myelin sheath
saltatory conduction
46
Cellular junctions where signals are transmitted from neurons to target cells
synapses
47
Synapses target cells (3)
1. Other neurons:
- Axodendritic synapse
- Axoaxonic synapse
- Axosomatic
2. Muscle cell (Neuromuscular junctions)
3. Gland cells (Neuroglandular junctions)
48
Two types of communicating junctions or synapses
1. Electrical synapses via **gap junctions**
2. Chemical synapses involving **neurotransmitters**
49
- allows current to flow directly from one cell to another
- allows the exchange of small molecules between cells
- a patch where cells are separated by a narrow gap of ________
Electrical synapses (Gap junctions);
2-4 nm
50
Gap junctions are formed where hexameric pores called ______ connect with one between cells
connexons
51
Each connexon is comprised of ____ identical subunits called _____
six; connexins
52
in electrical synapses, permeability of junction is mediated by conformation of the ________
connexons
53
in electrical synapses, impulses can go in _____ direction, while chemical synapses are _______
either direction (bidirectional);
one direction only (unidirectional)
54
- allows the flow of ions between neuron and are specialized for the release and reception of chemical neurotransmitters
- actual gap or space between nerve cells
- prevents direct transmission of action potential
chemical synapses
55
chemical synapses are separated by the ______ (___ to ____ nm wide)
synaptic cleft (30-50 nm wide)
56
two parts of chemical synapses
1. axon terminals: synaptic vesicles
2. receptor region of the postsynaptic neuron
57
Criteria that define a neurotransmitter: (3)
1. present at presynaptic terminal
2. must be released by depolarization, **Ca++-dependent**
3. Specific receptors must be present
58
Synaptic vesicle release consists of three principal steps:
1. docking
2. priming
3. fusion
59
During ____, vesicles lie close to plasma membrane (within _____)
docking, 30nm
60
During _____, vesicles can be induced to fuse with the plasma membrane by :
* sustained depolarization,
* high K+,
* elevated Ca++,
* hypertonic sucrose treatment
priming
61
During ______, vesicles fuse with the plasma membrane to release transmitters. Physiologically this occurs near ________, but can be induced experimentally over larger area.
The ________ is the site of physiological release, and can sometimes be recognized as an *electron-dense structure*.
fusion, calcium channels
**active zone**
62
is a protein that helps in priming during the release of synaptic vesicle
Munc-13
63
complexes that forms during docking to pull the two membranes together
SNARE complexes:
* Vesicle
- Synaptobrevin
- Synaptotagmin
* Postsynaptic cell
- Syntaxin
- SNAP-25
64
What is the purpose of calcium during signal transmission at a chemical synapse? And how do they go in the presynaptic cell?
Calcium signals the vesicles to fuse with the presynaptic membrane and release the messenger chemicals.
Depolarization of presynaptic terminal causes opening of voltage-gated Ca2+ channels.
65
Two types of synapse according to how they affect the membrane potential of the postsynaptic neuron (2)
1. Excitatory Synapses - Excitatory postsynaptic potentials (EPSPs)
2. Inhibitory Synapses - Inhibitory postsynaptic potentials (IPSPs)
66
What determines whether a stimulus will be strong enough to produce an action potential in a nerve cell?
1. The resting membrane potential is about -70mV.
A **threshold stimulus** will sufficiently increase the permeability of the membrane to sodium ions to raise the membrane potential to about **-55mV**. Once this threshold potential has been reached, **complete depolarization and repolarization occur** and an action potential is generated.
67
Is the size of the action potential related to the strength of the stimulus?
No. Nerve and muscles obey the **all-or-none law**, which states that a threshold stimulus evokes a maximum response and that a subthreshold stimulus evokes no response.
68
What factors influence the speed at which impulses are conducted along excitable cell membranes?
* Diameter of the conducting fiber: proportional
* Temperature of the cell: proportional
* Presence or absence of the myelin sheath through **Saltatory conduction**: proportional
