Chapter 11 - Part 2 Flashcards by Halle Kuck

______ should be used to separate the positive and negative charges

Energy

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A measure of potential energy generated by separated charge; Measured between two points in V or mV
A.k.a - Potential difference

Voltage

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Greater the difference between two points______
Greater the voltage (potential difference) ________

Higher voltage, greater current

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Charge difference in plasma membrane
Negative reading = more negative inside than outside

Membrane potential

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Flow of electrical charge (ions) between two points
Can be used to do work
Flow is dependent on voltage and resistance

Current

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Hindrance to charge flow
Insulator: substance with high electrical resistance
Conductor: substance with low electrical resistance

Conductor

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Nongated channels; Always open

Leakage channels

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Part of protein changes shape to open/close the channel
When opened, ions diffuse quickly towards opposite charge
3 types: Chemically, voltage, mechanically

Gated channels

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Open only with binding of specific chemical

Chemically gated channel

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Open and close in response to changes in membrane potential

Voltage gated channel

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Open or close in response to physical deformation of receptors, as in sensory receptors

Mechanically gated channel

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Combination of electrical and chemical gradients; Determines which way ions flow

Electrochemical gradient

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Voltage that exists across the plasma membrane during the resting state of an excitable cell
Approx. -70mV
Membrane = polarized ( inside - )

Resting membrane potential

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Differences in ion composition of intra/extracellular fluids
Differences in plasma membrane permeability to ions

Generating Membrane Potential

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When concentrations of ions across membrane change
Used as signals to receive, integrate, and send infomation
2 types: hyperpolarization, depolarization

Changing membrane potential

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Increase in membrane potential; Further from zero
Inside of membrane becomes more negative than resting potential
Probability of nerve impulse decreases

Hyperpolarization

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Decrease in membrane potential; Moves towards zero
Inside of membrane becomes less negative than resting membrane potential
Probability of producing nerve impulse increases

Depolarization

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Incoming signals operating over short distances; Results in depolarization
Short-lived; stronger the stimulus, the more the voltage changes and further the current goes
Occur at cell body and dendrites

Graded potentials

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Long-distance signals of axons

Action potentials

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Type of graded potential; Stimulus is a form of energy (heat, light, etc.)

Receptor potential

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Type of graded potential; Stimulus is a neurotransmitter from another neuron
Excitatory (EPSP) - Brings the neuron closer to AP threshold
Inhibitory (IPSP) - IPSPs drive the neuron away from AP threshold

Postsynaptic potential

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Transient (short) depolarization event along the cell membrane; Voltage changes from -70mV to +30mV
Principal way neurons send signals
Do not decay over distance

Action potential

Action pontential sheet for other facts

First part in action potential
All Na+ and K+ channels are closed; only leakage channels are open
Voltage gates are closed
-70mV

Resting state

Voltage sensitive gate in Na+ channel Closed at rest, opens with depolarization, allowing Na+ to re enter cell "Activates" action potential

Activation gates

Voltage sensitive gate in Na+ channel Block channel once it is open to prevent more Na+ from entering cell

Inactivation gates

How many voltage sensitive gates does K+ have? - Closed at rest - Opens slowly with depolarization

One

Second step in action potential; Na+ channels open; Local currents depolarize the axon membrane Na+ rushes into cell, and intracellular fluid becomes (+) (-55mV to +30mV)

Depolarization

For axon to "fire" depolarization must reach -55mV to trigger action potential Na+ permeability increases Na+ influx exceeds K+ influx Positive feedback cycle begins

Threshold voltage

Action potential either happens completely, or does not happen at all If number of Na+ ions that enter the cell is too low to achieve threshold, no action potential will occur

All or none response

Third part in action potential; Na+ channels are inactivating, K+ channels open AP spike starts to decline Na+ permeability declines Resting potential restored

Repolarization

Fourth part in action potential; Some K+ channels remain open, Na+ channels reset Inside of membrane becomes more (-) than resting state -80mV

Hyperpolarization

Transmission of action potential from it origin down entire length of the axon toward axon terminals Depolarization in one area causes depolarization in the next

Propogation

Once initiated, APs are _______

Self propogating

AP only occurs in the ______ direction

Forward

Time in which neuron cannot trigger another action potential Voltage gated Na+ channels are open, so neuron cannot respond to another stimulus Two types: 1. Absolute refractory period 2. Relative refractory period

Refractory period

Time from opening of Na+ channels until resetting of the channels

Absolute refractory period

Most Na+ channels have returned to their resting state Some K+ still open Repolarization occuring

Relative refractory period

1. Axon diameter: larger = faster 2. Degree of myelination: Continuous conduction/Saltatory conduction

Factors of AP rate propagation

Slow conduction that occurs in unmyelinated axons

Continuous conduction

Occurs only in myelinated axons and is 30x faster Myelin sheaths insulate and prevent leakage of charge Channels located at sheath gaps; AP only generated here Electrical signal jumps from gap to gap

Saltatory conduction

Autoimmune disease that affects primarily young adults Myelin sheaths are destroyed when immune system attacks myelin Symptoms: Visual disturbances, weakness, loss of muscular control, speech disturbance Treatment: drugs to modify immune system activity

Multiple sclerosis (MS)

Junctions that mediate information transfer; Neuron to neuron Two types: 1. Electrical - less common, neurons electrically coupled 2. Chemical - Specialized release of chemical neurotransmitter

Synapse

Neuron conducting impulses toward synapse (sending info)

Presynaptic neuron

Neuron transmitting electrical signal away from synapse (receives info)

Postsynaptic neuron

Synaptic connection between axon terminals of one neuron and dendrites of others

Axodendritic

Synaptic connection between two axon terminals of one neuron and soma (cell body) of others

Axosomatic

Fluid-filled cavity that prevents nerve impulse from directly passing from one neuron to the next

Synaptic cleft

"Language of the nervous system" Classified by either chemical structure or function Chemical passed through synptic cleft

Neurotransmitters

Excitatory vs. inhibitory Inhibitory - Hyperpolarization Excitatory - Depolarization

Effect neurotransmitter

Direct vs. indirect Direct - Neurotransmitter binds directly to and opens ion channels Indirect - Neurotransmitter acts through intracellular second messengers

Action neurotransmitter

Secreted in PNS; All neuromuscular junctions with skeletal muscle Effects prolonged when AChE blocked by nerve gas, leading to muscle spasms

Acetylcholine

Plays a role in sleep, appetite, nausea, migraine headaches, and regulating mood (happiness) Anti-depression/anxiety medications block function Activity blocked by LSD and enhanced by ecstasy

Serotonin