KINE 403 EXAM 1

K+

Na+

Cl-

Ca2+

Important ions to remember

Cation

Positively charged ion

Anion

Negatively charged ion

Charged particles

Ions are _____

Carry charge with them

When ions move across the membrane, they _____

Electrical differences

The fact that ions carry their charge with them creates _____ across the membrane

Diffusion

Net movement of a substance from areas of higher concentration to areas of lower concentration

Concentration gradient

The difference in concentration between two areas

Ion selective channels

Channels through the membrane that only allow one type of ion through

Appropriate channels for ion movement

Concentration gradient to drive movement

What is needed for ions to diffuse across the membrane?

Current

When charged particles move, it produces a _____

Electrical current

The movement of electrical charge

Amps

What is electrical charge measured in?

Electricity

Because ions are charged, _____ will also drive ion movement

Electrical potential

Conductance/resistance

2 factors important in how electricity drives ion movement

Electrical potential

Indicates the difference in charge between two points

Volts

What is electrical potential measured in?

More, more

The larger the electrical potential, the _____ ions will move (_____ current)

Electrical conductance (g)

The ability of an electrical charge to move

Electrical resistance (R=1/g)

Measures the inability of an electrical charge to move

Inversely

Electrical conductance and resistance are _____ related

Ohm's Law

Conductance, potential, and current are mathematically related through _____

I=gV

Ohm's Law

Current

I in Ohm's law

Conductance

g in Ohm's law

Potential

V in Ohm's law

Isn't firing

A cell at rest _____

Constant charge at rest

Neurons generate a _____

At any moment

Membrane potential (Vm) is measured across the cell membrane _____

Voltmeter

A _____ is used to measure the difference in voltage across the membrane

-65 mV

At rest, the Vm of a neuron is about _____

Vm

Membrane potential symbol

Diffusion

Electricity

What are the driving forces that cause ions to move?

Equilibrium Potential (E)

Electrical potential generated across the membrane at electrochemical equilibrium

+62 mV

The equilibrium potential of Na+ is _____

At equilibrium, net movement

Once the Vm reaches +62 mV, Na+ is _____, after this occurs, Na+ will continue to move in and out of the membrane, but there will be no _____

More positive

If a positively charged ion moves into the cell it makes the inside of the cell _____

More negative

If a positively charged ion moves out of the cell it makes the inside of the cell _____

Inside of the cell

Charge is referred to based on the _____

E and Vm

If we know _____ we can always predict the direction that an ion will move

Potassium

Most important ion in resting membrane potential

Nernst Equation

Calculates the exact value of the equilibrium potential (Eion) for each ion in mV

Universal gas constant

R in nernst equation

Absolute temperature

T in nernst equation

Charge of the ion in question

z in nernst equation

Faraday constant

F in nernst equation

Extracellular concentration

[ion]o in nernst equation

Intracellular concentration

[ion]i in nernst equation

-80 mV

Equilibrium potential of K+

K+ leak channels are open

Negatively charged molecules are stuck inside cell

Actions of Na+/K+ pump

Why is the resting membrane potential -65mV?

K+

At rest, the membrane is more permeable to _____ than it is to other ions

4 subunits surrounding central pore

The K+ channel structure is _____

Polypeptide chain loop

K+ channel pore contains a _____ that makes the pore highly selective for the ions that can pass through it

Selectivity filter

Polypeptide chain loop acts as a _____

Large effects on membrane potential

Because of K+ specific permeability, extracellular K+ concentrations can have _____

Inside to outside

What direction does K+ typically move?

Against

Sodium-potassium pump moves _____ concentration gradient

ATP

What does the sodium-potassium pump use as energy?

K+

Ions with higher distribution inside cell

Na+, Ca2+, Cl-

Ions with higher distribution outside cell

Ion pumps

Formed by membrane spanning proteins

Maintain

The sodium-potassium pump works to _____ ion gradients

70%

Sodium-Potassium pump uses _____ of the ATP within the brain

3, inside, outside

Sodium-potassium pump moves _____ Na+ from _____ to _____

2, outside, inside

Sodium-potassium pump moves _____ K+ from _____ to _____

More negative

Sodium-potassium pump moves ions which causes the inside to be _____ relative to the outside

Goldman-Hodgkin-Katz equation

Used to calculate membrane potential

Permeability, each

Goldman-Hodgkin-Katz equation takes _____ of _____ ion into account when calculating

40

The concentration of K+ is about _____x greater than Na+

Extracellular K+

The resting membrane potential is very sensitive to _____

Blood brain barrier

Highly selective semipermeable border that separates the blood in circulation from the brain

Endothelial cells of capillary walls and astrocytes

The blood brain barrier is made up of _____

Bacteria, large, and hydrophilic substances

What does the blood brain barrier restrict?

O2, CO2, hormones, small polar molecules

What does the blood brain barrier allow?

Hyperkalemia

Too much potassium in the system

Hyperkalemia, K+

The blood brain barrier protects against _____ by limiting the amount of _____ allowed in

Potassium buffering

The action of astrocytes in which they use K+ pumps to pump K+ out of the extracellular fluid and into the astrocytes to help regulate K+

Extracellular fluid

Astrocytes also have K+ pumps that pump K+ out of _____

Action Potential

Rapid change in membrane potential, where the membrane potential becomes positive for a brief period of time

2 msec

How long does an action potential generally last?

Action potentials

The basis for neural communication

Postive

Injecting a _____ current into the cell causes action potentials

Oscilloscope

Used to measure the fast membrane potential changes that occur during an action potential

The same

Every peak of an action potential for a neuron (amplitude) will be _____

Graded depolarizations that are strong enough to exceed threshold potential

Where do action potentials come from?

Mechanical perturbation of cell

Release of neurotransmitters

Injecting current with electrode

Where do graded depolarizations come from?

Mechanical perturbation

Touching the skin of your finger as a way to create a graded depolarization is an example of _____

Voltage gates closed; no AP

If depolarization is below threshold value, _____

Maximum potential change produced; AP

When depolarization reaches threshold, _____

Depolarizes to the same voltage (same amplitude)

Unlike graded potentials, an action potential always _____

Does not

The action potential _____ carry information about the input signal

Amplitude

The information being carried by an action potential isn't from its _____

The Neural Code

Neurons communicate with each other through the timing and number of action potentials

Timing and number of action potentials

Neurons communicate with each other through _____

Excitation

An increase in the rate of action potentials

Inhibition

A decrease in the rate of action potentials

T

All action potentials are a graded potential (T/F)

F

All graded potentials are action potentials (T/F)

Rising phase

Overshoot

Falling phase

Undershoot

Phases of the Action Potential

Voltage-gated Na+ channels open and ions rush in

What happens during the rising phase of an action potential?