CH 1 2.0

Afferent

Arrives — signal coming INTO a structure

Efferent

Exits — signal leaving/sending away from a structure

Santiago Ramón y Cajal

Argued neurons are separate, individual (contiguous) cells — the correct view

Camillo Golgi

Argued neurons merge into a continuous net; his staining technique enabled Cajal's discovery. Both shared the Nobel Prize

Dendrites

Part of the neuron that receives signals

Soma (cell body)

Contains the nucleus; integrates incoming signals

Axon hillock

The trigger zone — where the action potential is generated

Axon

Carries the signal away from the soma

Myelin sheath

Fatty insulation around the axon that speeds up conduction

Presynaptic terminals (terminal buttons)

Release neurotransmitter onto the next cell

Dendritic spines

Small protrusions on dendrites where neurons connect; more common in enriched environments

Astrocytes

Star-shaped glia; support/synchronize neurons metabolically and help form the blood-brain barrier

Myelinating glia

Glia that wrap axons in myelin (oligodendrocytes in CNS, Schwann cells in PNS)

Microglia

Small immune/scavenger glial cells

Blood-Brain Barrier

Regulates what crosses from blood into the brain; blood supplies glucose and amino acids for energy

Phospholipid

Building block of the membrane; has a head and a tail

Phospholipid head

Made of phosphoric acid; hydrophilic (points outward, toward water)

Phospholipid tail

Made of glyceride; hydrophobic (points inward, away from water)

Phospholipid bilayer

Two layers of phospholipids forming the semipermeable neuron membrane

Ion channel (protein)

Protein that spans the membrane and forms a channel so ions can move through

Ions

Chemicals that carry a charge; cause neurons to be polarized

Chemical force

Concentration gradient — ions move from high concentration to low concentration

Electrical force

Electrostatic gradient — like charges repel, opposite charges attract

Sodium (Na+) — chemical force

Pushes Na+ from outside to inside (high to low concentration)

Sodium (Na+) — electrical force

Pushes Na+ inside, since the inside is negative and opposites attract

Sodium (Na+) — net effect

Both chemical and electrical forces push Na+ IN

Potassium (K+) — chemical force

Pushes K+ from inside to outside (high to low concentration)

Potassium (K+) — electrical force

Makes K+ want to stay inside, since opposites attract

Potassium (K+) — net effect

Chemical and electrical forces OPPOSE each other for K+

Concentration of Na+

Highest concentration OUTSIDE the cell

Concentration of K+

Highest concentration INSIDE the cell

Resting Membrane Potential (RMP)

-70 mV; the electrical difference between inside and outside of the cell when no action potential is firing

No action potential (AP) is occurring

What is "resting"

The electrical property of a cell, measured in millivolts (mV)

What is "potential"

Leaky potassium channels

Constantly let K+ leak out of the cell, making the inside more negative and helping establish RMP

Sodium-potassium pump

Uses ATP to pump ions against their concentration gradient; ratio is 3 Na+ out : 2 K+ in, which helps maintain -70 mV

Sodium-potassium pump ratio

3 sodium out, 2 potassium in

The chemical force

Which ionic force is stronger overall?