Study Guide: Fundamentals of Neuroscience Exam 1

Neuron

a nerve cell; the basic building block of the nervous system

glial cells

cells in the nervous system that support, nourish, and protect neurons

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Myelin

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.

Translation

Process by which mRNA is decoded and a protein is produced

Transcription

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

cell membrane

A cell structure that controls which substances can enter or leave the cell.

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Ribosomes

Makes proteins

Microtubules

Microtubules carry proteins up & down the long processes of the neuron

Optogenetics

a technique in neuroscience in which genes for light-sensitive proteins are introduced into specific types of brain cells in order to monitor and control their activity precisely using light signals.

fMIR

Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow.

EEG (electroencephalogram)

An amplified recording of the waves of electrical activity that sweep across the brain's surface. These waves are measured by electrodes placed on the scalp.

ERP ( event-related potential )

An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event.

What are the functions of glia cells?

Some glial cells function primarily as the physical support for neurons. Others provide nutrients to neurons and regulate the extracellular fluid of the brain, especially surrounding neurons and their synapses.

What is the direction of information flow in a neuron?

From the Axon hillock to the axon terminals, to the next neuron

What does it mean to show a brain function is necessary for cognitive function?

Cut out genes which may encode a specific proteins, reduce or remove behavior

What does it mean to show a brain function is sufficient for a cognitive functions

Stimulate neuron, produce behavior, that neuron's activity must be

sufficient to produce that behavior

Potential

having or showing the capacity to become or develop into something in the future. ( action potential )

Resting potential

the electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse.

Synaptic potential

Synaptic potential refers to the potential difference across the postsynaptic membrane that results from the action of neurotransmitters at a neuronal synapse. In other words, it is the "incoming" signal that a neuron receives.

Action potential

the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.

Threshold potential

The minimum membrane potential that must be reached in order for an action potential to be generated. ( -55mv )

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

Hyperpolarization

The movement of the membrane potential of a cell away from rest potential in a more negative direction.

Diffusion forces/concentration gradient

ions of the same type (Na+, Cl-, etc) want to be distributed evenly on both sides of the membrane

Electrostatic force

The force between electrically charged objects (like charges repel and opposite charges attract each other).

Electrochemical equilibrium

When the chemical and electrical gradients are equal in magnitude, the ion is said to be in electrochemical equilibrium, and the membrane potential that is established at equilibrium is said to be the equilibrium potential (Veq.) for that ion under the existing concentration gradient.

Equilibrium potential

For each ion, the equilibrium (or reversal) potential is the membrane potential where the net flow through any open channels is 0.

Permeability

the state or quality of a material or membrane that causes it to allow liquids or gases to pass through it.

ion channels

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Nerst Equation

Calculates equilibrium potential ( Eion =58log[ion]out/[ion]in )

Goldman equation

is used in cell membrane physiology to determine the reversal potential across a cell's membrane, taking into account all of the ions that are permeant through that membrane.

Are K+ ions more concentrated inside or outside the cell?

inside

Is k+ equilibrium potential positive or negative

Negative

Are Na+ ions more concentrated inside or outside the cell?

outside

Is Na+ equilibrium potential positive or negative

Positive

At resting potential, the cell membrane is more permeable to which ion species?

Potassium ( K+ )

At the peak of the action potential, the cell membrane is most permeable to which ion species?

Sodium ( Na+ )

Why is the squid giant axon so useful to the study of electrical potentials?

They are large in size

What is the difference between the Nernst equation and the Goldman equation? When would you use each

In presence of more than one ion, the Nernst equation can be modified into Hodgkin-Katz-Goldman equation or is commonly known as Goldman equation. ... It is used to determine the equilibrium potential across a cell's membrane using all of the ions taht can cross the membrane. I would use the Goldman equationto determine the reversal potential across a cell's membrane, and the Nernst equation to find the cell potential at any moment in during a reaction or at conditions other than resting potential

Voltage clamp

A device that enables an investigator to hold the membrane potential constant while transmembrane currents are measured.

inward current

positive charge flowing into the cell

Outward current

Positive charge flowing out of the cell

Tetrodotoxin (TTX)

A toxin that blocks Na+ permeation through voltage-gated sodium channels, thereby blocking action potentials.

Tetraethylammonium (TEA)

blocks K+ channels

Ion channel activation

start the K+ conductance, takes some time

Ion channel inactivation

closing of the channel even when the stimulus continues.

Refractory period

the time following an action potential during which a new action potential cannot be initiated

Voltage-gated ion channels

Channels that open or close in response to a change in the membrane potential.

Passive current flow

Current flow across neuronal membranes that does not entail the action potential mechanism.

Saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

Nodes of Ranvier

gaps in the myelin sheath

Why was the voltage clamp technique so important to early ion channel experiments?

Manipulating currents in order to measure ion currents

Study depolarization, ion species, etc

What two currents are evident under voltage clamp conditions when the membrane is depolarized?

EARLY INWARD NA+

late outward K+

What currents are evident under voltage clamp conditions when the membrane is hyperpolarized?

Give 3 pieces of evidence suggesting that Na+ is responsible for the early, inward current that comes with depolarization of the membrane potential

1.The reversal potential for that current matches the predicted equilibrium potential for Na+

2. You take the sodium away, you taje the early inward current

3. Block sodium ( Na+ ), block the inward current

Describe the order and time course of Na+ and K+ channels opening and closing and their consequent effects on voltage during an action potential

True or false: passive current flow moves in both direction on an axon

False

True or false: propagation of action action potential moves in both directions on an axon

Patch-clamp method

Allows experimenters to examine ion channels

one at a time

Microscopic currents

Ionic currents flowing through single ion channels.

Macroscopic current

Ionic currents flowing through large numbers of ion channels distributed over a substantial area of membrane.

Voltage-gated channel: closed state

not conducting ions, but ready to be opened

Voltage-gated channel: open state

conducting ions

Voltage-gated channel: inactivated state

closed / not ready

Ligant-gated ion channels

ion channels that are normally closed, but open when a ligand, or a very specific chemical, binds to the channel (like a neurotransmitter or a drug)

Stretch activated channels

which open due to mechanical force acting on the channel

Ion selectivity

a property of ion channels that are selectively permeable to some ions and not to others

Voltage sensor

detects the potential across the membrane

Ion channel subunit

Membrane-spanning protein chains that together make up an ion channel

Alpha subunit

Usually, the alpha subunit is the pore, or hole, which the ion passes through

Beta subunit

Beta and other subunits provide stabilization or other functions

Pore

Is the hole that allows ions to pass through

Selectivity filter

the part of an ion channel structure that determines which ions it can transport

Active transporter

is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient.

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

Na/K pump

3 Na out, 2 K in

Ion exchanger

membrane transporters that translocate one or more ions against their concentration gradient by using the electrochemical gradient of other ions as an energy source.

Name some similarities and some differences between macroscopic currents and their underlying microscopic currents.

Similares:the are going to have the same reversal potential, Na+ is going to be inward. Move same direction

Differences: shape, the size.

How are the patch-clamp and voltage-clamp techniques the same? How are they different?

In the voltage-clamp configuration, a current is injected into the cell via a negative feedback loop to compensate changes in membrane potential. Recording this current allows conclusions about the membrane conductance. The patch-clamp technique allows the investigation of a small set or even single ion channels.

Name one benefit to using Xenopus occytes to examine ion channel function

One of the primary advantages of oocytes is that these cells do not express a large number of ion channels and re- ceptors, so that the exogenous protein can be studied without contamination from endogenous channels.

True or false: voltage gated ion channels are specific to individual ion species

True

True or false: Voltage gated ions are always open

False

How do ion channels achieve specificity to Na+ or K+

Channels narrow to the size of K+ molecules

4 ions push off of each other/repel forces

What is the role of a voltage sensor in a voltage gated ion channel?

Channels have to be sensitive to voltage changes

When the voltage changes, voltage sensors change the shapes of proteins to open them

The Na/K pump moves which ion species outside and which inside? At what rate?

Moves Na+ OUTSIDE (3)

and pushes K+ INSIDE (2)

What happens to Na+ efflux when ATP metabolism is inhibited?

Name two types of active transporter we've learned about

Na+ channel

K+ channel

True or false: potassium ion channels are never voltage gated

False

What is the difference between an ion pump and an ion exchanger?

Ion exchanger uses energy from electrochemical gradient of Na+ rather than ATP, like in ion pumps

What would happen if there was no active transport in a neuron?

Passive transport: everything would move slowly with no sudden depolarization/hyper polarization