Signal Transsuction Mechanisms: I. Electrical and Synaptic Signaling in Neurons

Central nervous system (CNS)

Brain and spinal cord.

Peripheral nervous system (PNS)

Sensory or motor components.

Neurons

Send and receive electrical impulses.

Glial cells

Encompass a variety of cells and the most abundant type of cell. (Supporting cells)

Sensory neurons

Detection of stimuli.

Motor neurons

Transmit signals from the CNS to the muscle and glands and they make synaptic connections.

Interneurons

Process signals and transmits information between parts of the nervous system.

Cell body

Includes nucleus and the endomembrane components.

Dendrites

Receive signals.

Axons

Conduct signals.

What is myelin?

Insulation that is wrapped to speed up the process.

Nerve

Is a tissue composed of bundles of exons.

Membrane potential (Vm)

The difference between electrical potential on the inside and outside of the cell.

Electrical excitability

Nerve, muscle and other cells types.

Squid giant axon

Allows microelectrodes to measure and control electrical potentials.

Action potential

Membrane potential changes back from negative to positive and then back again in a short period of time.

Certain stimuli triggers a rapid set of changes in membrane potential.

Leak channels

Not gated; always open.

Requires ATP.

Electrical equilibrium

When a chemical gradient is balanced with electrical potential.

Nernst equation

Relationship between an ion gradient and the equilibrium potential that will form when the membrane is permeable (allowing things to pass through) only to that ion.

Effects of ions on membrane potential

K+ : diffuse out of the cell, making the membrane potential more negative.

Na+ : flow into the cell, membrane potential is positive, causing depolarization.

Depolarization

More positive.

Hyper polarization

More negative.

Patch Clamping (signal-channel recording)

Permits the recording of ions currents passing through individual channels.

Voltage-gated ion channels

Respond to changes in voltage across a membrane.

Voltage-gated sodium channels

Large monomeric proteins with four separate domains.

Contains six transmembrane a helices.

Channel gating

Open rapidly in response to a stimulus and then close again.

Channel inactivation

When a channel is inactivated, it can not reopen immediately, even if stimulated to do so.

Threshold potential

Imitates an action potential.

What is myelin sheath formed by?

Oligodendrites in the central nervous system. Schwann cell in the peripheral nervous system.

Consequences of myelination

Myelination decreases the ability of the neuronal membrane to retain electrical charge (that is, it decreases capacitance).

Nerve impulses can spread farther and faster than in the absence of myelination.

The action potential must still be renewed; this happens at nodes of Ranvier.

Electrical synapse

One neuron.

Presynaptic

Is connected to a second neuron.

Excitatory receptors

cause depolarization of the postsynaptic neuron. (excite” the neuron and cause it to “fire off the message,” meaning, the message continues to be passed along to the next cell).

Inhibitory receptors

cause the postsynaptic cell to hyperpolarize.(prevent or block chemical messages and decrease the stimulation of nerve cells in your brain).

Optogenetics

genetically engineered channel proteins that are sensitive to light (meaning the ion concentration can be manipulated by light) can be introduced into neurons.

Bacteriorhodopsin

Inhibit neurons.

Channelrhodospins

activate neurons.