Quiz 2 - Neurophysiology Flashcards
Study to ACE quiz 2! (75 cards)
1
Q
What is a microglia responsible for?
A
Immune system function.
2
Q
What kinds of macroglia are there?
A
Astrocytes (do a little bit of everything)
- Schwann Cells
- Radial Glia
- Oligodendrcytes
3
Q
What are glia responsible for?
A
- Act as glue
- Exchange signals with neurons
- Help establish synapses
- Remove neurotransmitters after release
- Release “gliotransmitters” to regulate activity of neurons.
- make proteins and pass it on to the neurons.
4
Q
What is ataxia?
A
Gene mutations of glia result in this neurological disorder.
5
Q
How can neurons be classified?
A
By structure or function
- Unipolar
- Bipolar
- Multipolar
6
Q
What are some examples of different types of neurons?
A
Sensory neurons: bring information to the central nervous system.
Inter-nuerons: associate sensory and motor activity in the cns.
Motor neurons: Send signals from the brain and spinal cord to muscles.
7
Q
Describe the pathway of a neuron.
A
- Dendrites
- Cell body
- Axon hillock
- Axon
- Presynaptic Terminal
8
Q
What do reflexes do?
A
pass information to brain.
- Used to study behavior
- Automatic
- Include inhibition and excitation
9
Q
What are convergence and divergence reflex pathways?
A
- Convergence (many signals come to one) and divergence (one signal splits to many) pathways.
10
Q
What is feed forward inhibition?
A
When a excited pathway inhibits a second pathway.
11
Q
What is feedback inhibition?
A
Excited pathway leads to inhibition of that pathway.
12
Q
What occurs at the axon hillock?
A
Integration of information.
- Rich in voltage-sensitive channels
- EPSPs and IPSPs integrated
- Action potentials initiated here
- Depolarize membrane at axon hillock to threshold.
13
Q
What is the usual membrane potential?
A
-70mV
14
Q
Does output of signal depend on input?
A
Yes, more input from initial signal = more output (more transmitter release)
- Frequency of firing tells intensity of signal
15
Q
What is a labeled-line?
A
Each neuron is prewired to carry information from a certain point to the appropriate part of the brain.
16
Q
Describe ion-channels.
A
Membrane-spanning proteins.
- regulate ion passage based on size and chemical identity.
- Gated: voltage, chemically, physically.
- Studied using patch clamps
17
Q
What are the factors for ion movement?
A
Concentration gradient and Electrical charge.
18
Q
How do channels open and close?
A
By changing conformation due to ligands, signals, etc.
19
Q
What do channels consist of?
A
Built of protein subunits and are distinct from each other.
- Subunits affect the channel kinetics.
20
Q
Do K+ and Cl- pass readily?
A
Yes.
21
Q
What are leak channels?
A
Ion channels that are always open and NOT gated.
- EG. K+ leak channel or Na+ leak channel
22
Q
What is Nernst (equilibrium) potential?
A
E(x) = 57mv/z log [Xout]/[Xin]
23
Q
What do graded potentials do?
A
Disrupt RMP
- small voltage fluctuation in cell membrane
- decay over time and space
- depolarizing (EPSP) or hyperpolarizing (IPSP)
- Combined through spatial or temporal summation.
24
Q
What are the differences between Graded and action potentials?
A
AP: all or none, slower, passive AND active
Graded: decremental, fast, passive
25
Factors that input depends on.
- Location and size of synapse (greatest at hillock)
- Proximity to other synapses
- Relative strength of other synapses
26
How do PSPs affect membrane voltage?
By 0.2 - 0.4 mV
27
Describe spatial summation.
The larger the slower the curve falls off.
| - Membrane length constant
28
Describe temporal summation.
Larger = drops off slowly
| - membrane time constant
29
How is the speed of an action potential affected?
Speed affected by myelination and diameter of axon.
| - Thicker diameter = faster
30
Describe the steps of an action potential.
1. Depolarization to threshold.
2. Activation of sodium channels and rapid depolarization (influx of Na+)
3. Inactivation of sodium channels and activation of potassium channels (efflux of K+) repolarization
4. Return to normal permeability after hyperpolarization
31
What is an absolute refractory period?
Action potentials can't generate during this time.
- Prevent backwards movement
- Limit rate of firing
- Na+ channels inactive
- Occurs during depolarization
32
What is the relative refractory period?
K+ channels still active
- Requires stronger than usual stimulus to trigger an action potential.
- Occurs during repolarization phase.
33
What is myelin for?
Formed by oligodendrocytes in CNS and Schwann cells in PNS
| - Speeds up neural impulse.
34
What is the node of Ranvier?
Part of axon not covered by myelin
- occur every 1-2 mm
- 50x more voltage-sensitive channels here
- Signal jumps to each node
35
What happens at regions with no myelin?
Many interactions between the outside and inside of cell leading to no completed travel of signal.
36
What are chemical synapses?
APs open Ca2+ channels
- Forces vesicles to fuse with membrane
- chemical released and diffuses across synaptic cleft (20-40 nm)
- neurotransmitter bins to receptors and causes change in postsynaptic cell
- slower than electrical synapses (0.3 ms)
- allows variability and signal amplification
37
What is the purpose of microtubules?
Transport structure that carries substances to the axon terminal.
38
What is an ionotropic transmembrane protein?
Ion movement through ion channels.
39
What are metabotropic transmembrane proteins?
Alter metabolism by changing shapes and effecting interactions inside.
- Activates second messenger via G protein
- Hydrolysis of membrane phospholipids (IP3, DAG, arachidonic acid (inflammation))
- Soluble gases (NO, CO)
- cAMP
- 7 domains.
40
What is an example of indirect gating?
G-protein coupled receptors
41
What is an example of direct gating?
Ion channels
42
Describe neuromusuclar junction
Axon branches
- ACh packaged in vesicles at active zones.
- ACh released onto unction folds
- AChE in basement membrane and diffusion rapidly inactivates signal.
43
Describe ACh-Gated Ion channels.
Requires 2 ACh to open
- Permeable to both Na+ and K+
- Rapid switching between on and off states.
- Allows 17 million ions to pass/sec
- Average open time 1 ms
- Normal stimulation opens ~200,000 channels
44
What are some examples of excitation and inhibition transmitters?
Glutamate = excitation
| GABA and Glycine = inhibition
45
What do IPSPs do?
Inhibit signal.
46
Describe a type 1 synapse (slide 69)
Excitatory
- typically coated on dendrites
- large active zone
- wide cleft
- round vesicles
- dense material on membranes (a lot)
47
Describe a type 2 synapse (slide 69)
Inhibitory
- typically located on cell body
- small active zone
- narrow cleft
- flat vesicles
- Sparse material on membranes (little)
48
Postsynaptic Potentials
Dendrites contain vlotage-gated Na+ and Ca2+ channels that amplify small EPSPs.
- Channels can also back propagate action potentials to dendrites, but function of this unclear.
49
What is dendrodendritic?
Dendrites send messages to other dendrites
50
What is axodendritic?
Axon terminal of one neuron synapses on dendritic spine of another.
51
What is axoextracellular?
Terminal with no specific target. Secretes transmitter into extracellular fluid.
52
What is axosomatic?
Axon terminal ends on cell body
53
What is axosynaptic?
Axon terminal ends on another terminal.
54
What is axoaxonic?
Axon terminal ends on another axon. (usually inhibitory)
55
What is axosecretory?
Axon terminal ends on tiny blood vessel and secretes transmitter directly into blood.
56
Basic pathway of metabotropic receptor.
1. External signal (first messenger)
2. Receptor (extracellular side)
3. Transducer
4. Primary effector
5. Second messenger
6. Secondary effector
57
What are some first messenger signals?
Norepinephrine, ACh, Histamine
58
What are some receptors?
Beta-adrenergic receptor, muscarinic ACh, Histamine receptor
59
What are some primary effectors?
Adenylyl cyclase, PLC, PLA2
60
What are some second messengers?
cAMP, IP3, DAG, Arachidonic acid
61
What are some transducers?
G subunits
62
What are some secondary effectors?
cAMP-dependent protein kinase, Ca2+ release, PKC, lipoxygenase
63
What is cAMP?
alpha subunit dissociates from G protein to affect target
- each with unique properties.
- process continues until transmitter removed.
64
IP3, DAG pathways
Membrane phospholipids hydrolyzed, separating polar head group from glycerol and tails
- most common target is PIP2
- DAG and IP3 produced
- DAG activates protein kinase C
- IP3 releases Ca2+ from storage.
65
What are tyrosine receptor kinases?
Activated by peptides: FGF, NGF, BDNF, insulin
- ligand binding causes dimerization, which activates TRK
- Activated enzyme ultimately causes long-term, slow-acting changes in gene expression.
66
What are soluble gases and their use?
NO, CO
- Easily cross membranes
- Don't use surface receptor
- Stimulates synthesis of cGMP
- Retrograde signaling: produced in postsynaptic travels backwards to interact with presynaptic.
- Must be made and used quickly because it can't be stored.
67
What does transmitter release depend on?
Ca2+ influx to presynaptic terminal
68
There is a ______ number of _____ _____ channels at _____ zone.
Large, voltage-gated Ca2+, active
69
What stores neurotransmitters and how are they released?
1. Packed into vesicles.
2. Vesicles fuse to membrane and release transmitter by exocytosis.
3. Fusion pore channel vs. complete fusion
70
What are the criteria for neurotransmitters?
1. Synthesized in neuron
2. Present in synaptic terminal and released to cause effect
3. Exogenous administration mimics endogenous effects.
4. Removal mechanism exists
71
Describe small-molecule transmitters.
1. Quick-acting neurotransmitters
2. Synthesized in axon terminal and pumped into vesicles.
EG: ACh, Amines (DA,NE, Histamine), Amino acids, ATP
72
Describe neuropeptide transmitters.
1. Multifunctional chain of amino acids that act as neurotransmitter
2. Synthesized from mRNA; often many different made from single mRNA
3. Do not bind to ion channels
4. Cause inhibition, excitation or both
73
What are the similarities and differences between small-molecule and peptide neurotransmitters?
Similarities: Send signals, used in most neurons, can coexist in vesicles for peptides
Differences: SM = synthesized locally, vesicles produced at presynaptic terminal and recycled, released by Ca2+ influx at active zones.
Peptides = synthesized in cell body, vesicles derived from golgi and are not recycled, released by non-specific mechanism anywhere in the cell, and requires higher Ca2+ concentration to cause exocytosis (repeated stimulation)
74
Why is the removal of neurotransmitters important?
To end current message and allow new message.
75
What are the three mechanisms for removal of neurotransmitters?
1. Enzymatic degradation: ACh esterase
2. Diffusion: Large molecules (transmitters, polypeptides)
3. Reuptake: Repackaged and reused (DA, NE, Serotonin)
