(4) Neuron Physiology: Cells and Electrical Signals

Na+ is most concentrated in the

ECF

Cl- is more concentrated in the

ECF

K+ is more concentrated in the

ICF

At rest, the cell membrane has ______ leak channels. This makes resting potential ________ dependent on it.

K+, more

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Neurons outside of the CNS

Sensory (afferent) division

Carries signals TO the CNS

Efferent Division

Carries signals from the brain, output signals

Autonomic Division

Unconscious reflexes; glands, smooth muscle, and cardiac muscle

Somatic Motor Division

Conscious movement, skeletal muscle

Dendrites

Receive information from other neurons

Soma (Cell Body)

Contains the nucleus and provides maintenance

Axon Hillock

Cone shaped region of an axon where it joins the cell body. Decides if there will be an action potential

Axon

Passes messages through its branches to other neurons or to muscles or glands

Myelin Sheath

Insulating layers around axon, increases speed of impulses

Nodes of Ranvier

Gaps in between myelin sheath on axon, allows impulses to continue

Terminal Bouton

Synaptic vesicles located here

Glial cells (general)

10-50 times more glial cells than neurons, support structure and function of neurons

Ependymal Cells

Create barriers between compartments and are a source of neuron stem cells

Astrocytes

Support metabolic activity of neurons

Microglia

Scavenger cells that help immune functions

Oligodendrocytes

Create myelin sheath in CNS

Schwann Cells

Create myelin sheath in PNS

Satellite cells

Supports metabolic activity of neurons

What does the Nernst Equation calculate

Contribution of one ion to membrane potential

What does the GHK equation calculate?

Contribution of all ions to the membrane potential

Ions with _______ permeability have greater contribution to __________

greater, membrane potential

Resting Membrane Potential

The membrane potential of a cell at rest, typically -70mV

Hyperpolarization

Cell membrane decreases potential

Depolarization

Cell membran increases potential

If Na+ moves into the cell from open channels, the membrane potential will __________

Depolarize

If K+ moves into the cell from open channels, the membrane potential will ________

Hyperpolarize

Leak Channels

Open all the time; permit unrestricted leakage of specific ions

Gated Channels

Permit ion passage via a gate that can be open or closed

Voltage Gated Channels

Will respond to the cells current membrane potential

Chemically gated channels

Open with binding of a specific neurotransmitter

Graded potential

Changes in membrane potential on the dendrites or cell body of a neuron. Localized to site of stimulus and strength depends on strength of stimulus.