Lecture 5 - Membrane Potential Flashcards
1
Q
- functional units of nervous system
- receive, process and transnit infromation ot other cells
A
neurons
2
Q
parts of neurons
A
- soma
- dendrites
- axons
3
Q
- body of a neuron
- metabolic miantenance
A
soma
4
Q
receptive surface that brings signals from other neurons toward the cell body
A
dendrites
5
Q
- conduct signals away from the cell
- carry information for long distances with high fidelity and without loss
A
axons
6
Q
detect sensory information from receptors
A
Afferent (sensory) neurons
7
Q
carry impulses or motor commands to muscles and glands.
A
efferent (motor) neurons
8
Q
located inside the central nervous system and are in between afferent and efferent neurons
A
Interneurons
9
Q
Transmission of signals in a single neuron
A
- surface membrane innervated
- action potential initiation
- AP carried from spike-initiating zone to axon terminal
10
Q
nerve impulse
A
action potential
11
Q
corresponds to the site where action po- tentials are initiated
A
spike initiation zone (SIZ)
12
Q
- localized electrical gradient
- electrical potential difference across cell membrane caused by different concentrations of K+, Na+, and Cl- ions
A
membrane potential
13
Q
membrane potential of neurons is usually between
A
-60 to -80 mV
14
Q
where are excess negative charges found
A
plasma membrane side
15
Q
where are excess positive charges found
A
other side
16
Q
membrane potential is the source of __ __ to move molecules across membranes
A
potential energy
17
Q
how do excitable cells use changes in membrane potential
A
communication signals
18
Q
membrane potential is critical for what?
A
coordinated movements of cells and organisms
19
Q
what do every cell have
A
voltage or membrane potential
20
Q
more concentrated within a cell
A
anions (negative)
21
Q
more concentrated in the extracellular fluid
A
cations (positive)
22
Q
factors affecting potential difference
A
- concentration gradient of ion
- membrane that is permeable to that ion
23
Q
resting potential of unstimulated cell
A
-70mV
24
Q
the magnitude of membrane potential __ until an equilibrium is reached
A
increases
25
equal numbers of anions and cations
electroneutral
26
as more potassium leaves the cell , what happens to the electrical force
increases to level that balance driving force from potassium concentration gradient
27
draw positive charges into the cell
excess negative charge inside
28
cations in membrane potential
- K+
- Na+
29
K+
principal intracellular cation
30
Na+
principal extracellular cation
31
anions in membrane potential
- proteins, amino acids, sulfates, phosphate
- Cl-
32
proteins, amino acids, sulfates, phosphate
prinicpal intracellular anions
33
Cl-
prinipal extracellular anion
34
concentraiton of K+ is greater inside the cell, wile concentration of Na+ is greater outside the cell
resting potential
35
use ATP to maintain K+ and Na+ gradients
sodium-potassium pump
36
converts chemical potential to electrical potential
opening of ion channels
37
what does the neuron at resting potential contain
- many open K+ channels
- fewer open Na+ channels
38
- allow ions to diffuse across the plasma membane
- always open
non-gated ion channels
39
can generate large changes in their membrane potential
excitable cells
40
open or close in response to stimuli
gated ion channels
41
Types of gated ion channels
1. chemically-gated ion channels
2. voltage-gated ion channels
42
open or close in response to a chemical stimulus
chemically-gated ion channels (ligand-gated ioni channels)
43
open or close in response to a change in membrane potential
voltage-gated ion channels
44
changes in membrane potential
graded potentials
45
graded potentials
1. hyperpolarization
2. depolarization
46
membrane potential becomes more negative as gated K+ channels open and K+ diffuses out of the cell
hyperpolarization
47
membrane potential becomes less negative as gated Na+ channels open and Na+ diffuses into the cell
depolarization
48
all or nothing depolarization
action potential
49
what is triggered if graded potentials sum to ~-55mV
action potential
50
~-55mV of graded potential sum
threshold potential
51
Two volted gates of Na+ channels
1. closed activation
2. open inactivation
52
open rapidly in response to depolarization
closed activation gates
53
close slowly in response to depolarization
open inactivation
54
Five steps on action potential
1. resting state
2. depolarization
3. rising phase of action potential
4. falling phase of action potential
5. undershoot
55
what happens in depolarization
- voltage-gated Na+ channels open first
- Na+ flows into cell
56
what happens in rising phase
- threshold is crossed
- membrane potential increases
57
what happens in the falling phase
- voltage-gated Na+ channels inactivate
- voltage-gated K+ channels open
- K+ flows out
58
what happens during undershoot
- membrane permeability to K+ is first higher than rest
- voltage-gated K+ close
- resting potential restored
59
- result of a temporary inactivation of Na+ channels
- second action potential cannot be initiated
refractory period
60
different period in changes in ion channels on membrane potential
1. depolarizing stimulus
2. absolute refractory period
3. relative refractory period
61
where is action potential repeatedly regenerated
along length of axon
62
how is action potential generated
Na+ ions flow inward across membrane at one location
63
rapid method by which nerve impulses move down a myelinated axon with excitation occurring only at nodes of Ranvier
Saltatory conduction
64
where does excitation occur
nodes of Ranvier
65
action potential travels directly from the presynaptic to the postsynaptic cells via gap junctions
electrical synapses
66
how does electrical synapses travel from presynaptic to postsynaptic cells
via gap junctions
67
- information is transferred via the release of a neurotransmitter from one cell that is detected by an adjacent cell
- more common than electrical synapses
chemical synapses
68
region where neurons nearly touch and where nerve impulse is transferred
synapse
69
small gap between neurons
synaptic cleft
70
carries out transmission across a synapse
neurotransmitters
71
what happens during transmission across a synapse by neurotransmitters
1. sudden rise in calcium at end of one neuron
2. stimulates synaptic vesicles to merge with presynaptic membrane
3. neurotransmitter molecules released to synaptic cleft
72
Three primary factors influencing impulse transmission
1. axon diameter
2. myelination
3. temperature
73
diameter of axon
typically around 1 micrometer
74
formation of myelin sheath around nerve
myelination
75
the lower the temperature, the __ the impulses move
slower
76
what is affected by axon diameter and myelination
velocity of impulse propagation
77
how fast the membrane ahead of the active regions is brought to threshold by the local-circuit current
conduction velocity of AP
78
large axon diameter conduct __ due to less resistance
faster
79
how far a change in voltage will spread
length constant
80
greater the length constant the __ the conduction velocity of AP
faster
81
evolutionary adaptation to increase the length constant of invertebrates
increase in axonal diameter
82
evolutionary adaptation to increase the length constant of vertebrates
myelination
83
composition of myelin sheath
layered glial cell membrane
84
increase the transmembrane resistance and decrease the effective neuronal membrane capacitance
myelination
85
by definition a material which is able to hold an electrical charge
Capacitance
86
by definition is a measurement of the difficulty to pass an electric current through a materia
resistance
87
- where action potential is usually triggered
- region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons or the environment
axon hillock
