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Generation of a resting membrane potential depends on
1. Differneces in ___ and ___ concentrations inside and outside of the cell.
2. Differences in ____ of the plasma membrane to those ions.
The ____pumps maintian the concentration gradiants of their elements across the membrane.
More K+ diffuses ___ than Na+ diffuses __ because the resting membrane is 25X more.
Maintenance of the resting membrane potential is possible due to ____.
- ATP expenditure of the neuron
- The actions o the sodium-potassium pump
Membrane potentials that act as signals : ____, ____, ____.
Neurons use changes in their membrane potentials as '_____' to detect or recieve, integrate, and send information.
Neuron changes come from anything that chances ___ concentrations on either side of the membrane or anything that changes ion ___ across a membrane.
Only permeability changes are important for transferring ____.
Types of signals that can be generated are
Graded Potential and Action potential
Graded Potentials are incoming signals operating over ___ distances.
i.e. dendrites to cell bodies.
Action potentials are ___ distance signals of axons .
Changes relative to the resting membrane potential are either
Depolarize: ____ potential (more postive) i.e. -70mV to -40mV
Hyperpolarize: ____ potential ( more Neg.)
ie. -70mV to -90 mV
How does a depolarization of the membrane affect the charge?
Becomes more Positive
What does a hyperpolarization membrane affect the charge?
During Depolarization there is an increased permeability to ___.
Hyperpolarization increases membrane permeability to ___ or __.
Graded potential are ____, local changes( shits) in membrane potential: Depolarization or hyperpolarization signals.
____ opens gaed ion channels.
Graded potentials are named according to ____ and ____.
Postsynaptic potential: neurons graded potential
Stimulated by a _____.
Depolarization: a small patch of the membrane ( red area) has become depolarized.
Spread of depolarization: the local currents that are created depolarize adjacent membrane areas and allow the wave of depolarization to ___.
Decay of membrane potential with distance:
Because current is lost through the leaky plasma membrane, the voltage ____ with distance from the stimulus ( the voltage is ___ ) Consequently, graded potential are ___ - distance signals.
Degrade of graded potential is rapid, as charge is lost across the ____. But short distance signals are critial for initialing an _____.
Action potentials occur only in ___ and ____.
Action potential is a brief change in membrane potential in a patch of membrane that is ____ by local currents. Totals change in charge is ____ mV.
During action potential's repolarization there is a ___ outflow and during hyperpolarization the ___ continues to flow out.
During action potentials, the membrane permeability depends on its membrane ___ and vise Versa.
At rest, only ____ channels for Na+ and K+ are open; maintaining the resting membrane potential.
The key players in an action potential are the _____ channals.
Voltage-gated Na+ channels have ___ gates and alternate between ___ different states.
Voltage-gated K+ channels have ___ gate and ___ states.
Voltate gated Na+ channels are closed during ____ states, and open by ____ .
- Resting State
Voltage-gated K+ channels are closed during ___, and open during ___.
- Resting State
Neurons generally repolarize once the membrane potential reaches approximately +30 mV because . . .
Voltage-gated K+ channel gates open
Action potential is generated at the ___ .
In Action potential, ions move ___; establishing a current flow & opening a ____ channel.
- Voltage-gated channel.
Original channel is ____ thus propagation is away from the point of origin and in one diection only.
Action potentials move in one direction from the point of origin
After AP, Na+ channels _____.
During action potentials, there is a Na+ influx during ____. and a K+ during ____.
For axon to fire, depolarization must reach ___.
Threshold: that voltage at which the AP is triggered.
Graded Potentials may be ___-threshold.
An action potential either happens completely, or it ____ happen at all.
But once generated, the ___ does not vary( all APs are identical).
During refractory periods
Voltage-gated Na+ channels are ___. Neurons cannot respond to ___.
During absolute refractory period,
Time form ___ of Na+ channels until ___ of the channels.
Ensures that _____ and enforces ____ transmission.
- All-or-none event
Relative refractory periods,
Inside of membrane is more ___ than resting . . . so ___ of AP generation is elevated.
During the relative refractory period, the ___ is substantially elevated and exceptionally ___ stimuli could trigger action potentials.
Conduction velocities in Axon depend on what two factors?
Axon diameter: big=faster
- Degree of myelination:
- -No myelin: slow, continous
- Saltatory: mylenated
In bare plasma membrane, voltage ____. Without volage-gated channels, as on a dendrite, voltage ___ because current leaks across the membrane.
In non-myelinated axons, conduction is ___.
IN myelinated axons, APs are generated only in the ____ and appear to jump rapidly from gap to gap.
Myelin sheath gaps
AP travels in one direction because it jumps to the next gap the Na+ channels are inactivated.
A local current produces a 'graded' depolaization that brings the ____ at the next node to ____.
Information gets between neurons via ____.
_____: axon to dendrite
_____: axon to cell body.
- Axodendritic synapses
- Axosomatic synapes
Most neurons function as ____ and postsynaptic neurons.
2 types of synapses:
- Chemical; release of neurotransmitters into a synaptic cleft
Chemical synapses transmit signals from one neuron to another using ______.
Neurotransmitter effects are _____ by reuptake throught proteins, enzymatic degradation, or diffusion away from the synapse.
Postsynaptic potentials ____ or ____ the receiving neuron
Neurotransmitter receptors cause ____ potentials that vary in ____ with
1: ____ of neurotransmitter released
2: ___ neurotransmitter stays in synaptic cleft
- Graded potentials
2 Types of chemical synapses
1: ___ Postsynaptic Potential (EPSP)
2: ___ Postsynaptic Potential (IPSP)
An excitatory postsynaptic potential is a local _____ of the postsynaptic membrane.
Bring neurons ____ to AP threshold.
Excitatory Postsynaptic potentials:
Neurotransmitters binding opens chemically gated ion channels, allowing ___ and ___ to pass at the same time.
Inhibitory postsynaptic potentials are _____.
Generally speaking, opening chloride channels in the postsynaptic membrane will result in an _______.
inhibitory postsynaptic potential
A single EPSP ___ induce an AP
EPSPs can ___ (add together) to influence the '___ neuron’
IPSPs can also summate, but ___ the probability
Most neurons receive both ‘excitatory and inhibitory’ inputs from thousands of other neurons
Only if EPSPs ____ & bring to it threshold will an AP be generated
2 types of summation:
Temporal: 1 or more presynsaptic neurons transmit impulses in rapid-fire. increased frequency
Spatial: Postsynaptic neurons stimulated by a large number of terminals at the same time.
Chemicals used for neural transmittion are classified ____ or ___.
Functionally classified Chemicals:
Excitatory or Inhibitory
Direct or indirect (ion channels or via 2nd messengers)
Ex., Direct: acetylcholine (excitatory, EPSP); Indirect: norepinephrine (either), Substance P (excitatory), endorphins (inhibitory), nitric oxide (either)
Depends . . .
on type of receptor &/or G-protein present
Neurotransmitter Function: Direct promotes ___ in membrane potentials. 1: Channel-linked (_____) receptors
2: ____-gated ions channels
Rapid, simple, brief.
Neurotransmitter Function: Indirect through ___ messenger systems
G-protein coupled (___) receptorsComplex, slow, prolonged
Neurons function in ‘___.
1st level of neural integration:
Functional groups of neurons
‘___ ’ incoming information received from receptors or other neuronal pools; ‘Process’, &
‘____’ information to other destinations
1st level of neural integration:
Patterns of synaptic connections in neuronal pools
Determine pool’s . . .
What occurs in the discharge zone of a neuronal pool?
Neurons are most likely to generate impulses.
___input, ___ outputs.
Reverberating circuits (_____)
control _____ activity.
Parallel after-discharge circuit:
Arranged in ___ arrays that eventually ____ on a single output cell.
Impulses reach output cell at ____ times.
Serial Processing for a simple reflex arc:
- Sensory Neuron
- Integration Center
- Motor Neuron
Patterns of Neural Processing:
Serial: Input travels along ___ pathway to a specific destination
Works in a ‘predictable’ all-or-nothing manner
Ex., reflex arc (spinal reflexes)
Patterns of Neural Processing:
Parallel: Inputs ___ into many ____ pathways
Ex., higher level thought processing
A ___ neuron sends information along several pathways
So a large amount of information is processed more quickly