the neuron and nerve transmission Flashcards
(105 cards)
1
Q
what are the 2 cells of the NS
A
neuron and neuroglia
2
Q
what is the function of the neuron
A
- receives, conducts and transmits electrical signals
- it’s the functional and structural unit of the NS
3
Q
what components make up a neuron
A
cell body and processes
4
Q
what is a cell body
A
cell mass of a neuron that contains nucleus and organelles
5
Q
what are processes
A
projections that come off the cell body (dendrites and axons)
6
Q
what organelles are found inside the cell body
A
- nissl bodies
- neurofibrils
- nerve fibers
7
Q
what are nissl bodies? what’s their function
A
- clusters of rough er
- synthesize proteins
8
Q
what are neurofibrils? whats their function
A
- bundles of intermediate filaments
- provide cell shape and support
9
Q
what are nerve fibers? what are some examples?
A
- neuronal extensions that emerge from the cell body
- axons and dendrites
10
Q
what are dendrites?
A
- processes that are the info receivors of a neuron
- conduct nerve impulses towards cell body
11
Q
what receptors do dendrites have
A
- receptor sites for chemical messengers from other cells to bind to
12
Q
what is an axon
A
- longer process that transmits a nerve impulse away from the cell body –> towards other neurons
13
Q
what components does an axon have
A
- axon hillock
- axon telodendria
- collaterals
14
Q
what is an axon hillock
A
site of transition between axon and cell body
15
Q
what is an axon telodendria
A
- branches/processes at the distal end of an axon
16
Q
what are collaterals
A
side branch of axons
17
Q
what is the axon terminal
A
axon ending that contain vesicles of NT
18
Q
what is a myelin sheath
A
- multilayer membrane coverings that wrap arounx axons
19
Q
what is the function of myelin sheaths
A
- insulate the axon
- inc speed of nerve impulses
20
Q
what are nodes of ranvier
A
- gaps along the myelin sheath
- location where collaterals arise
- where nerve impulse is transmitted
21
Q
how are neurons classified
A
structurally or functionally
22
Q
define the structural classification of neurons and what the types are
A
- number of processes on cell body
- unipolar (1), bipolar (2), multipolar (many processes)
23
Q
define the functional classification of neurons and what the types are
A
- classified according to the direction in which the nerve impulses travel
- sensory: delivers info (afferent)
- inter/association: makes a decision
- motor: sends info to muscle (efferent)
24
Q
what is the function of neuroglia
A
- support neurons –> holds nervous tissue together
- provide metabolic support for neurons
- aka helper cell
25
what are the types of neuroglia in the cns
- astrocytes
- oligodendrocytes
- miroglia
- ependymal
26
what are the types of neuroglia in the pns
- schwann cells
- satellite cells
27
which neuroglia is the largest and most abundant
astrocytes
28
what is the function of astrocytes
- hold and support neurons
- provide 3d framework
- regulate/control environment
- form the blood brain barrier
29
what is the function of oligodendrocytes
form and maintain myelin sheath
30
what is the function of the microglia
- immune function
- phagocytize microbes and damaged nervous tissue
31
what is the function of ependymal
- epithelial-like cells that line fluid-filled cavities
- produce cerebrospinal fluid
32
what is the function of schwann cells
- form myelin sheath
- each cell myelinates a single axon
33
what is the function of satellite cells
- same function of astrocytes
- provide structural support and regulate exchanges
34
what is a membrane potential
unequal charge difference across a membrane
35
what is the resting membrane potential
- membrane potential at rest
- -70 mV
36
what are the 2 types of potentials used by neurons
- grades: for short distance communication
- action: long distance communication
37
what are the factors that contribute to the membranes resting potential
- membranes
- sodium potassium ATPase pump
- negatively charged proteins
38
how do membranes contribute to the resting membrane potential
- barriers to charged ion
39
how does the sodium potassium ATPase pump contribute to the resting membrane potential
- establishes and maintains ion gradients
- responsible for unequal charge distribution --> 3 Na in/2 K out
40
what is the ion gradient caused by the sodium potassium pump
- high potassium inside cell
- high sodium outside of cell
41
how do negatively charged proteins contribute to the resting membrane potential
- their negative and are permanently inside the cell
42
at resting potential, what are the charges in and out of the cell
- negative inside
- positive outside
43
what do nerve and muscle cells have in common
the only ones who's change in membrane potential creates an electrical signal
44
what are ion channels
- channels that allow potentials to occur
- main path for current to flow across membrane
45
why do ion channels open or close
- in response to a stimuli
46
how do ion channels open
- due to the movement of ions through the membrane (down the electromagnet gradient)
- when ions move, they create electrical currents that changes the membrane potential
47
what is a chemically gated ion channel
ion channels that are opened/closed by a NT
48
what is a voltage gated ion channel
channels that are opened/closed by a change in membrane potential
49
whar are the 2 kinds of voltage gated ion channels? where are they located
- Na+ and K+ --> axon
- Ca2+ --> axon terminal
50
what type of chemically gated ion channel is used? where is it found?
- Na+ or K+ --> cell body and dendrites
51
what does polarized mean
another term for resting membrane potential
52
what does depolarization mean
potential become more positive (less polar)
53
what does hyperpolarization mean
potential becomes more negative (more polar)
54
what does repolarization mean
becomes more negative and returns to resting state
55
what does hyper-polarization mean
becomes more negative than -70 mV
56
a graded potential is due to what type of gate? where is it located?
- chemical gates
- along cell body and dendrites
57
what is an action potential
sequence of rapid events that depolarize and repolarize the resting membrane potential
58
what are the phases/steps in the formation of an action potential
1. threshold
2. depolarization
3. repolarization
4. hyperpolarization
59
what is the threshold?
-55 mV
60
describe the events that take place in the depolarization phase of an action potential
1. a stimulus brings the resting membrane potential to threshold
2. by reaching the threshold, it triggers the opening of the Na+ voltage gated ion channel to open
3. Na+ rushes in
4. because of the Na+, the membrane goes from -55 mV to +30 mV
5. at +30 mV, K+ channels open and Na+ channels close
61
describe the events that occur in the repolarization phase of an act pot
1. because the k+ gates are open, K+ rushes out of the cell, which causes repolarization
2. membrane potential returns back to -70 mV
62
describe the hyperpolarization phase of an act pot
1. overshoot (hyperpolarization) is corrected by the Na+k+ ATPase pump
2. the pump brings it back to rest
3. overtime, the pump restores the intracellular ion levels
63
what is a refractory period
- period in repolarization where the axon is unable to respond to a second stimulus
- Na+ channels are open and starting to close
- membrane can't response because it's already depolarized
64
what are the 2 types of refactory period
absolute and relative
65
what is an absolute refactory period
stimulus can't cause an act pot because it's happening during the opening/closing of Na channels
66
what is a relative refractory period
- Na gates are closes and K+ gates are open
- strong stimulus will reopen the Na channels and cause a second act pot
67
what is a graded potential
- small deviation from the resting membrane potential that either depolarizes or hyperpolarizes the membrane
68
how does a graded potential occur
- occurs when a stimulus causes chemically gated channels to open/close
69
where do graded potentials occur
cell bodies and dendrites
70
describe the current that's created by the graded potential
- electrical signals vary on magnitude depending on strength of stimulus
- are localized (current flows for a short distance)
- will quickly die out because the charge is loss
71
what is the all or nothing
a response will always occur at a given value or won't occur at all if that value isn't achieved
72
what are the 2 types of graded potentials
1. inhibitory post synaptic potential
2. excitatory post synaptic potential
73
what is ipsp (inhibitory post synaptic pot)
- NT binds to and opens K+ channel
- K moves out of cell
- causes hyperpolarization
74
what is excitatory post synaptic potential (epsp)
- NT binds to and open Na channel
- sodium moves into cell
- causes depolarization
75
list the difference between the graded potential and action potentials
graded
- magnitude varies
- depolarization or hyperpolarization
- signal fades
- in cell bodies or dendrites
- chemicaly gated ion channels
- NT driven
action
- same magnitude
- depolarizes and repolarizes
- signal is propagated
- found in axon and axon terminal
- voltage gated ion channels
- threshold driven
76
what is propagation
- when an ac pot (impulse) keeps its strength as it spreads along the membrane
- it's what allows communication from different parts of your body
77
when an impulse is spread along your body, is it the same act pot the whole time?
no
- they constantly regenerate
78
in what direction do act pot propagate?
- one direction only
- from trigger zone to axon terminal
79
why is transmission unidirectional
- because axon hillock cannot form an act pot
- previous segment enters into refractory period
80
what are the 2 types of propagation
- continuous conduction
- saltatory conduction
81
what is continous conduction
- step by step re/depolarization of each segment of the plasma membrane
- ions flow thru each voltage gated channel in each section
82
where do continous conductions propagate
unmyelinated axons and muscle fibers
83
what is saltatory conduction
- act pot occurs from node to node (leaps)
84
where does saltatory conduction occur and why
- myelinated axons
- myelinated axons inc speed and uses less energy
85
what are the steps of propagation
1. graded potential of +30 mV forms in axon hillock
2. current depolarizes the segment next to axon hillock which brings the sodium voltage gates to threshold
3. act pot forms while hillock enters refractory
4. +30 mv creates a current that brings next segment to threshold, which forms another act pot
5. this repeats until axon terminal
86
what is summation
process of adding up all graded potentials
87
what is temporal summation
adding up high frequency of graded potential
88
what is spatial summation
addition of epsp from several synapses in the same area, that arrive at the same time
89
what is a neuromodulator
compounds that stimulate or inhibit a NT
90
what are the 3 components of the synapse
1. axon terminal
2. synaptic cleft
3. motor end plate
91
what is a synapse
junction between 2 neurons or a neuron and effector
92
what is the axon terminal
- place filled with vesicles containing NT
93
what is the synaptic cleft
extracellular space between 2 neurons
94
what is a motor end plate (or posst neuron)
contains receptors for the incoming NT or chemically gated ion channels
95
what are the steps at the synapse
1. act pot arrives
2. Ca2+ gates open and calcium moves in
3. rush of calcium triggers the fustion of the vesicle membrane with the cell membrane
4. NT are released into the synaptic cleft
5. NT binds to receptors on post synaptic cleft/motor end plate
6. binding of NT causes the opening of gated ion channels
7. forms either EPSP or IPSP
8. depolarization may occur
96
what happens when a NT binds to and opens a Na channel
- epsp
- results in depolarization
97
what happens when a NT binds to and opens a K channel
- ipsp
- results in hyperpolarization
98
how many types of NT are there
50-100
99
what is the lock and key interactions of NT
a NT will only affect post synaptic receptors that have the correct shape for that specific NT
100
what is acetyl choline
- NT released at neuromuscular junction
101
epinephrine and norepinephrine
- NT released in sympathetic NS
102
what is a series circuit
info relayed step by step from one neuron to the next
103
what is a parallel circuit
several neuron circuits process the info at the same time
104
what is a converging circuit
info travels from many neurons to one neuron
105
what is a diverging neurons
info travels from one neuron to many neurons
