UConn PNB 2264 Exam 2

Exciteable Cells

Cells that are able to send and receive electrical information.

Electrophysiology

The study of excitability.

Compartmentalization

Having different homeostatic set points in two different parts of the body or cell.

Ions

Positively and negatively charged atoms. E.g. Sodium, Potassium, Calcium, Chloride.

Gate mechanism

Stimulus required to open or activate an ion channel. i.e. voltage gates and ligand-gates.

ligand-gated ion channel

Channels that are gated by a chemical messenger (ligand) on the inside or outside of the cell.

voltage-gated ion channels

Channels that are gated by a change in the charge of their surrounding environment inside the cell.

Think: membrane potential

Conformation

3D shape of protein

passive transport

The movement of ions down its concentration gradient; uses no energy.

Anions

negatively charged ions

Cations

positively charged ions

Electrostatic forces

Forces between atoms due to charge

Membrane potential (Vm)

Difference in charge between the intracellular environment and the extracellular environment. Expressed as a voltage.

Voltage

The potential difference measured in volts

Recording electrode

Sensor placed inside a cell to measure a voltage difference compared to the extracellular fluid.

Reference electrode

A second sensor placed in extracellular fluid that allows the membrane potential (voltage difference) to be measured across the cell membrane.

Equilibruim (Nernst Potential)

Electrochemical equilibrium point. Point at which there is no net ion difference across the cell membrane.

Nernst Equation

parallel conductance equation

Conductance (g)

The ability of an ion to carry a current across a membrane; different but related to permeability (P).

Goldman-Hodgkin-Katz equation

Conductance

Permeability

Resting Membrane Potential (RMP)

Steady state at which the movement of all ions is equal and opposite across the cell membrane (net flux is zero). Typically accepted as Vm=-70mV

leaky potassium channels

Potassium channels that are always open to allow potassium to leave the cell, down the concentration gradient. Causes the negative Vm resting potential.

Transduce

to convert from one form of energy to another

Dendrites

Projections of the neuron's cell membrane that are responsible for receiving signals from neurotransmitters. They contain special receptors for the neurotransmitters (ligand-gated channels).

Soma

The main body of the neuron.

axon hillock (trigger zone)

The site where action potential is generated. The point of connection between the soma and the axon.

Axon

The extension of a neuron that acts as a wire, transmitting an electrical potential to the post-synaptic neuron.

axon terminal (synaptic knob)

The endpoint of a neuron that contain voltage gated channels that release neurotransmitters upon the stimulation by an action potential.

Nissl Bodies

Sites of extensive protein synthesis in a neuron.

Anterograde transport

From the soma down the axon. Like signal transmission

Retrograde transport

From the axon terminal up the axon to the soma. Like signal receiving.

Dendritic Spines

Thousands of tiny projections from the dendrites.

initial segment (axon hillock)

AKA Trigger Zone; the beginning of the axon that contains many volgate gated Na channels.

trigger zone (axon hillock)

aka initial segment.

Mylenated

Describes the insulated covering of some axons.

Glial Cells

Nervous cells that do not play a role in signal transmission, but perform maintenance on neurons.

Synapses

Small gaps between the axon terminals of one neuron and the dendrites of another neuron

Pre-synaptic

Describes a neuron that is sending a signal

Post-synaptic

describes a neuron that is receiving a signal

Synaptic cleft

A synapse filled with interstitial fluid.

Synaptic potential

Change in membrane potential produced on post-synaptic neuron.

Graded potentials

A change in membrane potential that decreases in intensity over time and distance

Action potentials

Opposite of a graded potential, where a change in membrane potential remains consistent over time and distance

Axodendritic synapses

synapse formed between a pre-synaptic cell's axon terminals and a post-synaptic cell's dendrites

Signal input

A signal that is being transmitted

Depolarization

Membrane potential moving from rest to a more positive value (positive slope, above resting Vm)

Hyperpolarization

Membrane potential moving from rest to a more negative value (negative slope, below resting Vm)

Synaptic potentials

Graded potentials in the dendrites

excitatory postsynaptic potential (EPSP)

depolarizing synaptic potential

inhibitory postsynaptic potential (IPSP)

Repolarizing (negative slope above the resting Vm) synaptic potential

Decremental

Get weaker over time and distance. i.e. graded potentials

Temporal summation

individual channels that are activated repeatedly over a short time

Spatial summation

Multiple channels that are simultaneously opened

Integration

Essentially taking the summation of signals inputted into a neuron; done in the soma

Threshold

The membrane potential required to start an action potential

subthreshold stimulus

Synaptic potentials that do not cause an action potential to be transmitted

suprathreshold stimulus

A synaptic potential that leads to an action potential to be generated and transmitted.

Action Potential phases

1. Resting/RMP

2. Stimulus/Depolarization

3. Rising/Depolarization

4. Peak Phase

4. Falling/Repolarization

5. Hyperpolarization

6. After Hyperpolarization

7. Resting/RMP

Voltage-gated sodium channels

Channels that cause depolarization phase due to suprathreshold stimulus

Closed state

The state of a Na Voltage channel that does not allow sodium to pass through. Entire protein closes off, different from "inactive" state.