Foundations of Neuroscience Exam 1

Dendrite

(look like branches) where the neuron receives input from other cells

Myotatic or knee-jerk reflex

a reflex is something you do not need higher brain function for to occur- hammer tap stretches tendon which in turn stretches sensory receptors in leg extensor muscle

fMRI

a tool that allows us to see changes in blood flow in response to sensory stimuli

Necessary

take away brain activity to look for impairments in behavior test for...

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

1) Na+ channels open, depolarizing the cell 2) Na+ channels close 3) K+ is moves out, hyperpolarizing the cell

Voltage Clamp

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

ATP

Adenosine triphosphate (ATP) is an important extracellular signaling molecule. ATP acts as a neurotransmitter in both peripheral and central nervous systems.

Neuron

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

Refractory period

a period of time during which a cell is incapable of repeating an action potential

Passive current flow

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

Transcription

DNA is the blueprint; you don't want to mess with the blueprint too much so you can make a copy to work with, takes the code in DNA and turns it into a copy of the form that the "processing plant", the ribosome, can work with mRNA, promoter regions of DNA are markers that transcription machinery recognizes, in order to know where to start reading and when

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

EARLY INWARD NA+late outward K+

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

Inward Na+ equilibrium potentialCurrent reverses at Na+ equilibrium potentialCurrent reduces in size when Na+ reduces

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

Ion pumps require energy usually from ATP hydrolysis, whilst exchangers use the energy established by the concentration gradient of another ion.

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

Macroscopic are made up of microscopic currentsThey are typically in the same direction

patch-clamp method

a recording pipette is attached to a single neuron. This allows experimenters to examine ion channels one at a time which allows us to see voltage changes

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

Potassium

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

Same- involve ion currents, involve the membraneDifferent- voltage-clamp involves adding electrical potential, patch-clamp involves PINCHING the cell membrane, patch-clamp looks at ion channels ONE at a time

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

The Nernst equation is a more simple version of the Goldman equation.

Electrochemical equilibrium

a balance between electrostatic forces and diffusion forces

Permeability

a material's capacity to transmit liquids or gases

Myelin

an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord.

Tetraethylammonium (TEA)

blocks K+ channels

Tetrodotoxin (TTX)

blocks Na+ channels

Action Potential

change in separation of charges when outgoing signal occurs (decision to send message along to next cell, in axon)

Synaptic Potential

change in separation of charges when outgoing signal occurs (decision to send message along to next cell, in axon)

Voltage-gated channel: inactivated state

closed, and not ready to be opened

Voltage-gated channel: open state

conducting ions

direction of flow in a neuron

dendrite to soma to axon to terminal buttons to synapse

Saltatory conduction

describes the way an electrical impulse skips from node to node down the full length of an axon

Resting Potential

due to separation of charges when no signaling is happening

Ion channel inactivation

even when you hold the voltage constant, the Na+conductance turns off quickly

True or false: Potassium ion channels are never voltage-gated

false

True or false: Voltage-gated ion channels are always open.

false

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

false

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

false

Microscopic currents

flow through individual channels

Nodes of Ranvier

gaps in the myelin sheath

Ion channel subunit

general composition of ion channels. Is equal to one amino acid.

Name one benefit to using Xenopus oocytes to examine ion channel function.

good expression system: will translate almost any RNA you inject, you can even control the amount of protein you assemble by controlling the amount of RNA you inject, Ultimate control over ion channels you record from: mutate ion channels proteins to get different characteristics

Potential

he way in which we can measure how much voltage exists between the two half cells of a battery.

Nucleus

holds information like DNA in the center

Pore

hole which the ion passes through

Equilibrium potential

in an ion, the greater the difference in concentration outside and inside the cell, the greater the...

Oligodendrocyte

in the central nervous system (brain & spinal cord)

Schwann cell

in the peripheral (somatic) nervous system: form myelin (helps electrical impulses travel faster and to sustain over long distances) , the insulating sheath that covers most axons

Motor Neurons

inputs other neurons, outputs muscles and glands, some processing only 1 (in passing) output

Interneurons

inputs other neurons, outputs other neurons, lots of processing (in-between other neurons)

Sensory Neurons

inputs sensory receptors, outputs other neurons, and made for quick relay, not much processing (get that information and send it back) example: something is touching your skin

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

inside

Ion channel activation

ion channel receptors open pores in the cell membrane, causing the formation of electrical current.

Diffusion forces/concentration gradient

ions of the same type want to be distributes evenly on both sides of the membrane

Cell Membrane

like the skin of your cell

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

sodium (na)

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

look in group me for answer

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

made it possible to determine the precise relationship between membrane current, membrane conductance, and membrane voltage, and consequently to derive a quantitative description of the ionic basis of the action potential.

Alpha subunit

made up of 4 repeating structures that make up the pore, some areas are voltage sensitive, allowing changes in shape with voltage changes

Depolarization

make the membrane less polarized or less negative

Depolarization

make the membrane less polarized, or less negative

Hyperpolarization

make the membrane more polarized, or more negative

Hyperpolarization

make the membrane more polarized, or more negative. This deos not turn on any active processes, now new ion channels are open

Goldman equation

more complicated version of a way to find equilibrium potential

Na-K pump

moves both Na and K against their concentration gradients by forming complexes with them. This requires a lot of energy in the form of ATP.

Consequently, is K+'s equilibrium potential positive or negative?

negative

ligand-gated ion channel

normally closed, but open when a ligand binds to the channel (neurotransmitter), this is how info is carried from one neuron to the next

Free Ribosomes

not attached to the RER and can make proteins in the cytoplasm

Voltage-gated channel: closed state

not conducting ions, but ready to be opened

Leakage Channels

open all the time

stretch-gated channels

open due to mechanical force acting on the channel

ligand-gated ion channel

open in response to a chemical ligand binding to the channel

Electrostatic forces

opposite (charges) attract

Active Transporter

substances move against the concentration gradient, from an area of low concentration to an area of high concentration

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

outside

How are neurons unique?

plasticity- neurons routinely change structure and biochemical properties, even after the development period has passed longevity- most neurons are never replaced, that means they can be 100 years old in some cases shape- neurons are exceptionally long and thin, the longest neuron is from the tip of the toe to the base of your neck

Ion Channel

pore-forming membrane proteins that allow ions to pass through the channel pore

Consequently, is Na+'s equilibrium potential positive or negative?

positive

Inward Current

positive charge flowing into the cell

Outward Current

positive charge flowing out of the cell

Name two types of active transporter we've learned about.

primary and secondary

Sufficient

producing or creating brain activity to look for increased behavior test for...

Golgi bodies and Microtubules

protein packaging and shipment, just as essential as the proper creation of proteins, is making sure they get into proper place Golgi bodies: wrap proteins up landmark them for where they go microtubules: carry proteins up and down the long processes of the neuron

Ribosome

protein- can be studded along the rough endoplasmic reticulum when the protein needs to be packaged up into membrane

Beta subunit

provides stabilization

EEG/ERP

recordings of the electrical frequencies and intensities of the living brain, typically recorded over relatively long periods

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

responsible for initiation of action potentials and graded membrane potential changes in response to synaptic input and other physiological stimuli.

Some Glial Cells are

scavengers, removing debris after injury or cell death

Ependymal Cells Secrete Cerebrospinal fluid (CSF) purposes?

shock absorber, helps eliminate waste, may be a source of nutrients, may help in brain cooling

Macroscopic currents

summation of microscopic currents

Transition

takes the code in the mRNA and makes a useable protein out, the ER is studded with ribosomes that read the mRNA, 3 nucleotide (1 codon)= 1 amino acid, Many amino acids together = 1 polypeptide chain (protein for our purpose), Proteins are coded as a 1-dimensional string, but their chemical properties cause theme to fold into indeful 3-dimensional figures

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

the cell would stop moving sodium out

Treshold potential

the membrane potential at the point where Na+permeability caused by depolarization increases to make Na+ inward flow volume just equal to the K+ outward flow volume.

Glial Cells functions

they serve as supporting elements, providing firmness and structure to the brain, help form blood-brain barrier, the impermeable tight junctions in endothelial cells that line the blood vessels in the brain, Dilate blood vessels to support increases brain activity

Lesion

tissue destruction in the form of a traumatic brain injury or stroke

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

to understand the ionic mechanisms that propagate action potentials

True or false: Voltage-gated ion channels are specific to individual ion species.

true

Nernst equation

used to calculate equilibrium potential

Axon

where electrical impulses from the neuron travel away to be received by other neurons

Voltage-gated ion channels

which open and close depending on the potential across the membrane