Unit 1 Exam (Ch 2,3,4) Flashcards
Resting Potential, Action Potential, Intro info
1
Q
Glia
A
-Contribute to brain fxn by insulating, supporting, or nourishing neighboring neurons
2
Q
Neuron
A
- Brain cell
- Basic unit of brain fxning
- Sense changes in environment
- Communicate changes to other neurons
- Command body’s response to these sensations
- Cell body, dentrites, axon, neuronal membrane (separates inside from outside)
3
Q
Histology
A
-The microscopic study of the structure of tissues
4
Q
Cajal
A
- Worked out circuitry of brain using golgi stain
* *Communicate through CONTACT not Continuity
5
Q
Soma/Cell body
A
- Cystol: watery fluid inside cell, K+ rich, separated from outside by neuronal membrane
- Contains organelles
- Cytoplasm: Everything inside cell membrane, including organelles but excluding nucleus’
6
Q
Nucleus
A
- Spherical
- double membrane
- Location of chromosomes/transciption
7
Q
Gene expression
A
- Reading of DNA
- Final product= proteins
- Give neurons unique characteristics
8
Q
Protein synthesis
A
- Creation of proteins (translation)
- Location= cytoplasm
- Done by mRNA (4 diff nucleic acids in chain, sequence represents genes)
9
Q
Transcription
A
-Assembling of mRNA that contains info of a gene
-Result= transcript
@ One end of gene= promoter, where RNA polymerase binds to initiate
-Other end= terminator, RNA recognizes as end of transcription
-RNA splicing
-mRNA leaves nucleus through pores
***Transcription of a single gene gives rise to several diff mRNAs and protein products
10
Q
RNA splicing
A
- In middle of gene= introns and exons
- introns removed and exons fused together
- Altetnatively spliced mRNA–> specific exons removed w/ introns
11
Q
Amino Acids
A
- Building blocks of proteins
- 20 kinds
12
Q
Translation
A
-Assembling of proteins from amino acids using mRNA
13
Q
Molecular Biology
A
-Study of DNA in the nucleus and synthesis of protein molecules in cell
14
Q
Genome
A
-Entire length of DNA that comprises the genetic info in our chromosomes
15
Q
Gene copy # variations
A
- Genes are missing or duplicated
- Potential cause of schizophrenia and autism
16
Q
Mutations
A
- Errors in gene
- Small mutations= single nulceotide polymorphisms
- Misspelling of word due to single letter
- Can affect protein/neuron fxn
17
Q
Genetic Engineering
A
-Ways to change organisms by design w/ gene mutations or insertions
18
Q
Knockout mice
A
-Mice w/ deleted gene
19
Q
Transgenic mice
A
-Genes introduced and overexpressed
20
Q
Knockin mice
A
-Negative gene replaced w/ modification
21
Q
Rough ER
A
- Membrane w/ ribosomes attached
- Stained by Nissl Stain
22
Q
Ribosomes
A
- Location of protein synthesis on rough ER
- Use the blueprint provided by mRNA to manufacture proteins from raw material to create amino acids
23
Q
Free Ribosomes
A
- Freefloating ribosomes
- Attached by strand of mRNA
- Create proteins in cytosol
24
Q
Smooth ER
A
- Membraneous organelle
- Proteins jut out of membrane, are folded
- Play no role in processing proteins, regulate calcium
25
Golgi Apparatus
- Membrane enclosed discs in soma
| - Sort proteins and deliver them to diff parts of neuron
26
Mitochondria
- Site of cellular respiration
- Folds= cristae
- Brings pyruvic avid and oxygen into cystol
27
The Neuronal Membrane
- Barrier to enclose cytoplasm inside the neuron
- Excludes certain substances that float in fluid that bathes neuron
- Protein comp. depends on whether soma, dendrites, or axon
28
Cytoskeleton
- Gives neuron shape
| - Made up of microtubules, microfilaments, and neurofilaments
29
Microtubules
- Largest
- Located at neurites (run longitudinally)
- Straight, thin, hallow pipe
- Small strands= tubulin
- Anchor microtubules to each other and parts of neuron
- Actin guides axons onto dendritic spines
30
Microfilaments
- Smallest
- Concentrated at synapses
- Run longitudinally along neurites (dendrites and axons)
- As thick as cell embrane
- Made up of two thin strands of actin (changes size of cell)
31
Neurofilaments
- Middle size
- Structural support of axon
- Intermediate filaments in other cells, neurofilaments in neurons
- Multiple subunits wound together in ropelike structure
32
Axon
- Specialized for transfering info over distances
- Axon hillock: beggining of axon connected to soma
- Thicker the axon, faster impulse travels
33
Axon distinctions
(1) no rough ER
(2) diff protein comp than soma
(3) no protein synthesis
34
Axon collaterals
-Branches from axon
-Travel long distances to comm. w/ diff parts of NS
Ex: Recurrent collaterals: axon collateral returns to comm with same cell that gives rise to axon/ dendrites of neighbors
35
Axon Terminal
- End of an axon
- Comes in contact w/ other neurons at synapse
* Terminal arbor- short branches at end of axon that forms synapse
36
Innervation
-When a neuron makes synaptic contact with another cell
37
Cytoplasm in axon terminal differences from axon
(1) Microtubules do not extend into the terminal
(2) terminal contains synaptic vessicles
(3) inside surface of membrane that faces the synapse has a particularly dense covering of proteins
(4) Axon terminal cytoplasm has mitochondria (high energy demand)
(5) not myelinated
38
Synapse
- side: presynaptic (axon terminal) and postsynaptic (recieving dendrites/soma)
- Space btwn= synaptic celft
- Transfer of info= synaptic transmission
- electrical at axon, chemical at synapse, electrical at dendrites
* *Located at dendritic spines
39
Neurotransmitters
-Chem signal released at presynaptic end into synaptic cleft
40
Axoplasmic Transport
- Movement of materials down an axon
- Material is enclosed w/in vessicles, walk down microtubules of axon using protein
- Soma to terminal= anterograde transport w/ Kinesin
- Terminal to soma= retrograde transport w/ dynein
41
Dendrites
- Dendritic tree= dendrites of single neuron
- branch= dendritic branch
- Has RECEPTORS that detect the neurotransmitters in the synaptic cleft
- Dendritic spines- isolate various chem reactions triggered by synaptic activation
- Cytoplasm similar to axons
42
Ways to classify neurons
- Structure: # of neurites, types of dendrites, connections, axon length
- Classification based on gene expression
43
Number of Neurites
- Unipolar= 1 neurite
- Bipolar= 2 neurites
- Multipolar= 3 or more neurites (most pop in brain)
44
Dendrites as way of classifying neurons
- Stellate cells= star shaped
- Either spiny or aspinous
- Pyramidal cells
- Always spiny
* Spiny or aspinous (nonspiny)
45
Connections as way of classifying neurons
- Primary sensory neurons- @ sensory surfaces of body such as skin
- Motor neurons- muscles and command movements
- Interneurons- Connect to other neurons, brain and spinal cord
46
Axon length as way of classifying neurons
- Golgi type I neurons/ projection neurons
- One part of brain to another
- Golgi type II neurons/local circuit neurons
- short axons that do not extend beyond cell body
47
Neuron classifications based on gene expression
- Diff in gene expression causes physical differences
- Ex: pyramidal v stellate
- Which neurotransmitter used
- Due to diff in expression of proteins
- Ex: motor neuron= acetylchonline
48
Astrocytes
- Glia
- Abundant at synapses and nodes of ranvier
- Influence whether a neurite can grow or retract
- Regulates chemical content in extracellular space
- Restrict spread of neurotransmitters released at synpase/ remove neurotransmitters
- Control concentration of substances
49
Myelinating Glia
- Oligodendroglial (CNS, several axons) and Schwann cells (PNS, one axon)
- Insulate axons w/ myelin
- Uninsulated part of axon= Node of Ranvier (saltatory conduction)
- Speeds up impulses
- Highly enriched w/ ion channels
50
Microglia
- Glia
- Phagocytes
- Remove debris left by dead or decaying neurons and glia
51
Neuron Doctrine
1. Neuron is the basic unit of NS
| 2. Neurons in contact through synapse, not continuity
52
How is a neuron unique?
-Specialization for sending info rapidly along great distances
53
Action Potential
- A brief fluctuation in membrane potential caused by the rapid opening and closing of voltage-gated ion channels
- Spike, nerve impulse, discharge
- Fixed in size and duration
- Info encoded in the pattern of electrical impulses
- Positive inside, neg outside
54
Excitable Membrane
- Cells capable of generating and conducting action potential
- Nerve and muscle cells
55
Resting Membrane Potential
-Positive outside, neg inside
-Difference in electrical charge across membrane
Vm= -65 mV
-Calculated using Goldman equation
*K+ higher inside, Na+ and Ca2+ higher outside
*Membrane permeable to K+ at rest because potassium leak channels
56
Ions
- Atoms ot molecules that have a net electrical charge
| - Ex: Na- or Cl+
57
Neuronal Phospholipid Membrane
- Sheet of phospholipids 2 molecules deep
- Hydrophobic heads face inner and outer watery environment
- Hydrophilic tails face each other
58
Hydrophilic
-Polar Molecules/water loving
59
Hydrophobic
-Nonpolar molecules/water fearing
60
Lipid
- A class of water-insoluble molecules
- important to structure of all membranes
- Form barrier btwn water-soluble ions and water during RP and AP
61
Channel Proteins
-Rod-shaped proteins w/ polar groups exposed at either end by only hydrophobic groups showing on their middle surfaces
62
Ion channels
- Ion selectivity
- Specified by diameter of the pore
- Nature of lining R-group
- Gating= channels can open and close due to changes in microenvironment
63
Ion Pumps
-Enzymes that use energy to transport certain ions across membrane against concentration gradient
64
Influences on Movement of Ions
-Influenced by diffusion and electricity
65
Diffusion
- Net movement of ions from regions of high concentraton to regions of low concentration (Moving w/ conc gradient)
- Causes ions to be pushed through channels of the membrane
- Ions move this way when
(1) Membrane has channels permeable to ions
(2) Concentration gradient across the membrane
66
Concentration Gradient
- Differences in concentration from one region to another
| - Ions flow down their concentration gradient
67
Ohms Law
V=IR
- Relationship btwn conductance, potential, and ammount of current that will flow
- If no current, no voltage possible
68
What requirements are there to drive ions across a membrane?
1. Membrane that posesses channels permeable to that ion (provides conductance)
2. Electrical potential difference across the membrane
69
Membrane Potential
- The voltage across the neuronal membrane at any moment
* Close to Ek at RP
- Symbol= Vm
1. Larger changes in membrane potential caused by small changes in ionic concentration
2. Net diff in electrical charge occurs at the inside and outside surfaces of the membrane
3. Ions driven across membrane at rate equal to diff btwm membrane potential and equilibrium potential
4. Conc. diff across membrane is known for that ion, equilibrium potentials can be calculated for that ion
70
Voltometer
-Measures the electrical potential diff btwn tip of microelectrode and wire outside cell
71
Equilibrium state
-Diffusional and electrical forces are opposite and equal
72
Ionic equilibrium potential
- Electrical potential differences that exactly balances an ionic concentration gradient
- Eion
- Membrane potential that would result if a membrane were selectively permeable
73
Ionic Driving Force
- The diff between real membrane potential and equilibrium potential (Vm-Eion)
- Biggest absolute value
* Tells us which way and how powerfully an ion would flow if we opened a channel selective to that ion
74
Distribution of Ions across a membrane
- K+ more concentrated on inside
- Na+ and Ca2+ outside
- Ionic concentration gradients established by the actions of ionic pumps in the neuronal membrane
- Sodium-potassium pump & calcium pump
75
Sodium-Potassium Pump
- Uses ATP to drive Na+ and K+ against their. concentration gradients
- Na+ out, K+ in
- Maintains resting potential
76
Calcium Pump
-Active transport of Ca2+ out of cytosol across membrane
77
Goldman Equation
-A mathematical relationship used to predict membrane potential from the concentrations and membrane permeabilities of ions
Vm=RT/F *ln (sum of Pin*ion conc. at equilibrium)
***ACCOUNTS FOR ALL IONS
78
Depolarization
-The change in membrane potential from the normal resting value (-65mV) to a less neg value
79
Charge
- Colombs
- Positive or neg based on valence e-
- Ex: Na+ or Cl-
80
Energy
- Joules
| - Force x distance applied
81
Selective Permeability
- Cells leak K+ at rest
- K+ higher intercellularly, conc. gradient pushes the ion out of the cell--> inside more neg
* THE MORE PERMABLE A CELL IS TO AN ION, THE CLOSER THE CELLS POTENTIAL WILL BE TO THAT EQULIBRIUM POTENTIAL
82
How do we change membrane potential?
- Permeability
- Ion channels--> ligand gated channels, voltage gated channels, mechanically gated channels
- Concentration Gradients
- Electronic ion pumps regulate internal ion concentration
83
Pumps
-Membrane proteins that slowly move ions against their concentration gradient
84
Channels
- Allow ions to flown w/ concentration/ electrochemical gradient
- Selective to specific ions
85
Receptors
-Embedded within ion channels such as ligand's binding triggers to opening the channel
86
Action Potential Steps/ Info
- A positive voltage shift that activates voltage gated sodium channels
- Travels down axon to depolarize axon terminal
- Terminal depolarization initiates transmitter release
- Frequency and pattern used to transfer info
- Length: 2 mseconds
* ALL OR NONE
87
What would happen if a neuron where deprived of ATP?
- The cell would die of excitotoxicity (too many action potentials)
- Loss of ATP--> Ion pumps cease to fxn-->intracellular K+ drops, Intracellular Na+ rises, Intracellular Ca2+ rises--> cell depolarizes and spikes uncontrollably-->all no longer polarized--> dead
88
Voltage Gated Sodium Channels
- Activated by voltage, inactivates itself
- Highly selective to sodium
- Closed at RP, twists open w/ depolarization
- S4=voltage sensor (activates pore opening through depolarization)
- Ball and chain
* Resting closed, activated open, inactivated closed
89
Voltage Gated Potassium Channels
-Activated by depolarized voltage
90
Voltage-gated Ca2+ channels
-Trigger burst firing
91
Ligand Gated excitatory channels
- Both bind to neurotransmitter glutamate
- AMPA: allows Na+ into cell
- NMDA: Allows Na+ and Ca2+ into cell
- Creates post synaptic potential (PSP) that could trigger AP
92
Ligand Gated Inhibitory Channels
-GABA-A: Binds to neurotransmitter GABA to allow the flow of Cl- ions into the cell
93
Mechanically Gated Touch Receptors
- Meissner's Corpuscles and Merkel's Discs
| - Concentrated near surface of skin
94
Mechanically Gated Pain Receptors
- Free nerve endings (heat) and Pacinian Corpuscus (deep pressure)
- Have a higher threshold activation
- Travel to brain via different routes than light touch
95
What causes post-synaptic potential?
-Caused by the activation of ligand gated channels and mechanically gated channels
96
Capacitance
- The ability to "store" charge
- Measured in Farads
- dependent on distance of separation of charge
- Neurons deal with this through myelination
- Decreases capacitance (AP travels faster)
97
Rising Phase
- Rapid depolarization of membrane
- About 40 mV
- Membrane sodium channels open, Na+ go into cell
- Inside membrane has neg membrane potential= driving force for Na+
98
Overshoot
- Membrane potential goes to value closer to Ena, greater than 0mV
- Due to relative permeability favoring Na+
99
Falling Phase
- Rapid repolarization until neuron is more neg inside than before
- Na+ inactivates
- K+ channels open--> outward
- Causes membrane potential to be neg again
100
Undershoot
- Hyperpolarization
- Gradual restoration of RP
- VG k+ channels add to resting K+ permeability
- Membrane potential goes towards Ek
101
How does Depolarization occur?
1. Caused by specialized Na+ ion channels sensitive to membrane stretching
2. Interneurons-> Na+ entry through channels sensitive to neurotransmitter
3. Injecting current through microelectrode
102
Generation of Multiple APs
-Firing frequency of AP reflects magnitude of the depolarizing current
103
Relative Refractory Period
- Amount of current required to depolarize a neuron to AP threshold is elevated above normal
- Difficult to initiate another AP
104
Optogenetics
- Controlling neural activity w/ light
| - Introduces neurons to foreign genes that express membrane ion channels that open in response to light
105
Hodgkins and Huxley
- Voltage clamp
- Proved rising phase= influx of Na+, falling= outflux K+
- Gates opened by depolarization, inactivated by + membrane potential, open again after membrane returns to neg value
- K+= delayed recifier, opens after Na+ channels
106
Patch Clamp
* *Allows you to control for current or voltage to find out the other in V=IR
- Used to study ionic currents passing through individual ion channels
- Sealing tip of electrode to small patch of neuronal membrane
- Patch torn away, measures membrane potential
* Enabled fxnal properties of VG sodium channels
107
Threshold
-Membrane potential at which enough voltage-gated Na+ channels open so relative ionic permeability of membrane favors Na+ over K+
108
Absolute Refractory Period
- Na+ channels inactivate when membrane becomes strongly depolarized
- Cannot be activated again, AP cannot be generated again till membrane potential is neg
109
Factors Influencing Conduction Velocity
- Velocity increases w/ increased axon diameter
- Presence or absence of myelin
- Axonal size and # of voltage gated chanels in membrane
110
Spike Initiation Zone
- The part of the neuron where axon originates from the soma
| - Axon hillock
111
Why does sodium go into the cell instead of out?
- Higher conc outside than in
| - Ena= +60mV
112
Why does potassium go out of the cell instead of in?
- Higher conc. inside than out
| - Ek=-90mV
113
Characteristics of Action Potential
- All or none, either reaches threshold or doesn't
- Same magnitude and duration
- Membrane briefly more positive inside than out
- Regenerated over distance
- Wave motion
