Intro Neuro Exam 2

What is a neural circuit?

A population of neurons connected by synapses to carry out a specific function once activated

What do neural circuits regulate?

Thoughts, perceptions, and behaviors

What is the contemporary neuroscience view of the brain?

The brain is a network of interconnected regions with distinct, but overlapping functions

What is the primary unit of the nervous system?

The neuron

All neurons are _____.

Cells

What did Paul Weiss discover?

By dissecting a squid cell, he figured that neurons survive by sending information down it’s axon (from the nucleus to the terminal buttons)

How can neurons be classified? (SSNL)What

Size, shape, number of projections, and location

What is the most *useful* way of classifying neurons?

By the types of post synaptic effects produced when they release a neurotransmitter/neuromodulator

GABA is a _____ neuron.

InhibitoryGLuta

Glutamate is a ______ neuron.

Excitatory

What does every cell fire?

Action Potentials

What does an local neuron do?

Only affects the activities of \[a group\] neurons in that specific area

What does a projection neuron do?

Affect the activity of distant neurons/neurons in another place

What is a neuromodulator?

Chemical messenger that affects a lot of neurons.

All neuromodulators are _______.

Projection Neurons

What limits excitatory and inhibitory neurons?

They are limited to the specific neurons they are in contact with.

How can you prove that something is *necessary* for a certain process?

Inhibit the specific thing in question (i.e. inhibiting glutamate to prove it’s necessary for working memory)

How can you prove something is *sufficient* for a certain process?

You could conduct a substitution experiment

What are glia?

The glue that holds neurons in place

What are glia involved in?

The development, patterning, and maintenance of neural connections

What type of glial cell is absolutely necessary for the normal function of GABAergic and glutamergic synapses?

Astrocytes

How are glia classified?

The basis of their location (PNS/CNS), function, and shape

What do Oligodendrocytes (CNS) and Schwann cells (PNS) produce?

The myelin sheath around axons

What do astrocytes do?

Maintain ionic homeostasis in the brain, and are __necessary__ for the **blood-brain barrier** to function

What is the equivalent of white blood cells (macrophages) in the CNS?

Microglia

What do microglia do?

They are blood cells that migrate to the brain and move by amoeboid motion. They mediate many immune and inflammatory responses in the brain

What are the 3 types of Glia in the CNS?

Oligodendrocytes, Astrocytes, and Microglia

What is the blood brain barrier?

Concept that describes the separation of the brain from some things in the blood stream. It filters stuff from the nervous system, preventing them from getting into the brain

What are the three main parts of the BBB?

1. Tight Junctions between endothelial cells
2. No fenestrations in endothelial cells
3. Astrocytes

What do molecular motors do?

Transport molecules towards/away from the nucleus of the neuron. This is an ENERGY DEPENDENT process

What do motor proteins do?

Transport large cargo about the cell to their destinations

Kinesin walks towards the:

(+) end of tubular

Dyenein walks towards the:

(-) end of tubulin Prob

Problems in axonal transport are seen in a lot of ______ diseases.

Neurodegenerative

A cell with a Vm of 0 indicates what?

A dead cell

What is voltage (V)?

a measure of electrical potential between terminals

What is current (I)?

A measure of how many electrons are moving across the terminals. Units are in mA

What is the relationship between current and voltage?

They are proportional, but not the same

What is Resistance (R)?

The measure of the inability for electrons to move

What is the relationship between voltage, current, and resistance?

V = I/R

What does unequal distributions of ions cause?

An electrical potential that can result in an electrical current

Describe the levels of Na+, K+, and Ca2+ inside and outside the cell:

Na+: Low inside conc, high outside conc

K+: High inside conc, low outside conc

Ca2+” Low inside conc, high outside conc.

What maintains ionic imbalance across the membrane?

Lipids, as the cell membrane is a lipid bilayer that is selectively permeable to certain ions

How does a phospholipid bilayer form?

Spontaneously because when fats mix with water, lipid bilayers will form

What os the fluid part of the fluid mosaic model?

Fats moving (Lipids) as fluid structures

What is the mosaic part of the fluid mosaic model?

Not just fats, but the other things present in the membrane

What do cell membranes contain that make them selectively permeable?

Transmembrane proteins

What is an ion channel?

Allows specific ions to travel through the membrane in the direction of their concentration gradient (passive)

Do ion channels require energy?

No

What is a voltage gated channel?

Opens and closes in response to changes in voltage across the membrane

What is a leak channel?

A channel that is open by default in a cell at rest

What is a ligand-gated ion channel?

Channel that opens up in response to a neurotransmitter binding (**NOT VOLTAGE CHANGE**)

What is another name for a ligand-gated ion channel?

Neurotransmitter receptor; b/c they open in response to a neurotransmitter binding

What is a ligand?

Anything that interacts with another protein. This can be naturally occurring or synthetic

What is an ion pump?

Moves specific ions across the membrane against their concentration gradients

Why is an ion pump necessary?

It helps to maintain the unequal concentration gradient

Why is the Na+/K+ pump electrogenic?

There is a net negative charge of -1 b/c for every 3 Na+ out, 2 K+ come in

What form of energy does the Na+/K+ pump require?

ATP

Do pumps require energy?

Yes

What is an anti porter? (ex: Na/K pump)

A membrane protein that transports two molecules at the same time

If some potassium channels are open in a resting membrane (leak current), how can there be no net movement of K+ ion out of the cell?

The electrochemical gradient will keep charge particles from moving

What is the equilibrium potential?

Voltage at which the intra/extracellular concentrations of an ion are electrochemically balanced

What is capacitance?

A charge that exists across a membrane

What is an action potential?

Rapid change in the resting membrane potential of a neuron

What is an action potential in terms of ion movement?

Sodium influx

What does the term “all or nothing” refer to?

A neuron will either fire an action potential or won’t

What are the exceptions to the all or none principle?

Hair cells in the cochlea and photoreceptors in the retina (they show a graded response to stimulation by vibration and light respectively)

How do neurons function systematically?

They function in a circuit

What are the two synaptic functions of a neuron?

Presynaptic and Postsynaptic

Where do action potentials originate and subsequently end up?

In the axon hillock (soma) and travel own the axon

Who discovered action potentials?

Emil du Bois Reymond

Who measured the velocity of the action potential (in frogs)?

Herman von Helmholtz

What did Bernstein propose?

Neurons at rest are permeable to only potassium, but become transiently permeable to sodium during an action potential

Who discovered that sodium influx caused action potentials?

Hodgkin and Huxley

What animal did Hodgkin and Huxley use, and why?

Squid giant axon to study the ionic basis of the action potential being propagated

What did H&H suggest as a result of their electrophysiology experiments?

That gates open or close in response to changes in voltage across the membrane

Voltage gated ion channels are ____ at rest

closed

What is a voltage gated sodium channel?

Primary channel responsible for the generation of an action potential; Allows Na ions to flow into the cell and down their concentration gradient

What is a voltage gated potassium channel?

Channel that restores the membrane potential to its resting potential following the action potential; allows potassium ions to flow out of the cell and down their gradient

When do sodium channels begin to open?

\-55 mV

What is the refractory period?

The period of time after an action potential where a channel is unable to open again

When do potassium channels open?

They open in response to membrane depolarization but with a delay

Where does potassium go once its channels open? (think during an action potential)

It leaves the cell

How is potassium able to leave the cell during action potentials?

The electrochemical gradient has become unbalanced. The Na+ moving inside decreases the positive charge outside of the cell, and now the K+ has room to efflux out

What is the resting membrane potential?

\-65mV

What is depolarization?

Period when Na+ ions enter and make the cell more positive

What is repolarization?

When K+ leaves the neuron, causing a decrease in Vm

What is the function of the Na/K pump in a cell?

It restores the resting electrochemical gradient

What occurs during the absolute refractory period?

A second stimulus no matter how strong will not excite the neuron

What happens during the relative refractory period?

A stronger than normal stimulus is needed to cause an action potential, due to undershoot

What are neurotransmitters and neuromodulators contained in?

Vesicles

What is Dale’s Law?

Each neuron produces a single type of neurotransmitter

What is a neuropeptide?

Messenger molecules that co-exist in nerve cells with one or more small neurotransmitters

What do dense-core vesicles contain?

Neuropeptides

The inward rush of Na+ into the cell/axon terminal is also known as:

An action potential

How does an action potential travel?

Travels down the axon and arrives at the axon terminal

What does the presynaptic terminal contain?

Voltage gated calcium channels

When do voltage gated calcium channels open?

They open in response to membrane depolarization

What is Calcium (Ca2+) needed for?

The opening of the fusion pore between the vesicle and presynaptic membrane

What is synaptotagmin?

Calcium sensing protein located in the vesicular membrane