PSYCH 110 Midterm 1

Basic functional unit of the nervous system

Neuron

Broca's area

Region of the cerebrum associated with speech production

Flourens' lesion findings

Cerebrum = perception/cognition/voluntary action; Cerebellum = movement coordination

Animal model

A non-human organism used to study a biological process or disease relevant to humans

Neuron doctrine

The idea that neurons are discrete, individual cells (not a continuous connected network) — credited to Santiago Ramon y Cajal

Nissl stain

Stains the cell bodies (soma) of ALL neurons, but not their full dendritic/axonal arbor

Golgi stain

Randomly and completely stains a small percentage of neurons, including dendrites and axon

Anterograde transport

Movement from soma to axon terminal, powered by kinesin proteins

Retrograde transport

Movement from axon terminal back to soma, powered by dynein proteins

Interneurons

Neurons that connect only to other neurons (not sensory receptors or muscles); most abundant neuron type

Oligodendrocytes

Glial cells that myelinate axons in the CENTRAL nervous system

Schwann cells

Glial cells that myelinate axons in the PERIPHERAL nervous system

Astrocytes

Glial cells that sponge up excess potassium, support the blood-brain barrier, and provide metabolic support

Microglia

The immune cells of the central nervous system

Central dogma (of molecular biology)

DNA is transcribed into mRNA, which is translated into protein

Rough endoplasmic reticulum

ER studded with ribosomes; synthesizes membrane-bound and secreted proteins

Golgi apparatus

Packages and processes proteins, including peptide neurotransmitters, into vesicles for transport

Axon hillock / spike initiation zone

Cone-shaped region where the axon exits the soma; densely packed with voltage-gated Na+ channels; where action potentials normally originate

Resting membrane potential

Approximately -65 mV; the voltage difference across the membrane when the neuron is not firing

Phospholipid bilayer

Two layers of phospholipid molecules; hydrophilic heads face extracellular/intracellular fluid, hydrophobic tails face each other

Na+/K+ pump (sodium-potassium ATPase)

Pumps 3 Na+ out and 2 K+ in per cycle, against their gradients, using ATP

Concentration gradient

The difference in the amount of a substance (e.g. an ion) between two areas; substances passively diffuse from high to low concentration

Electrical gradient

The difference in electrical charge between two areas; positive ions are pulled toward negative areas and vice versa

ATP (adenosine triphosphate)

The cell's main energy-carrying molecule; breaking a phosphate bond releases usable energy

Nernst equation

Calculates the equilibrium potential for a SINGLE ion, accounting for its charge, temperature, and concentration ratio across the membrane

Goldman equation

Calculates overall membrane potential accounting for the RELATIVE PERMEABILITIES of multiple different ions (what the Nernst equation does not do)

Why resting potential is negative despite high internal K+

The membrane is far more permeable to K+ than Na+ at rest, so membrane potential sits close to the (negative) K+ equilibrium potential

Action potential

An all-or-none electrical signal triggered when depolarization reaches threshold

Threshold

The membrane potential (around -40 mV) that must be reached to trigger an action potential

Rising phase

Rapid depolarization caused by voltage-gated Na+ channels opening and Na+ rushing in

Falling phase (repolarization)

Na+ channels inactivate while delayed-rectifier K+ channels open, causing K+ efflux and a drop back toward resting potential

Undershoot / hyperpolarization

Occurs because delayed-rectifier K+ channels are slow to close, letting K+ continue leaving past resting potential

Absolute refractory period

Period right after firing when voltage-gated Na+ channels are inactivated and CANNOT be triggered again, no matter the stimulus strength

Relative refractory period

Period when Na+ channels have reset but threshold is temporarily elevated, requiring a stronger-than-normal stimulus to fire again

Conductance

Proportional to the number of open channels for a given ion

Tetrodotoxin (TTX)

A puffer-fish toxin that selectively blocks voltage-gated Na+ channels, preventing action potentials

Lidocaine

A local anesthetic that blocks voltage-gated Na+ channels, preferentially in smaller myelinated axons

Saltatory conduction

Action potentials "jump" from node of Ranvier to node of Ranvier along myelinated axons, increasing conduction speed

Nodes of Ranvier

Gaps between myelin segments where voltage-gated Na+ channels are concentrated

Orthodromic conduction

Normal direction of action potential travel: soma to axon terminal

Antidromic conduction

Reverse-direction conduction (axon terminal to soma); usually only occurs experimentally

Axodendritic synapse

Synapse where an axon terminal connects to a dendrite

Axosomatic synapse

Synapse where an axon terminal connects directly to the soma (cell body)

Axoaxonic synapse

Synapse where an axon terminal connects to another axon

Chemical synapse

Neurotransmitter is released from the presynaptic terminal, crosses the synaptic cleft, and binds postsynaptic receptors

Electrical synapse

Gap junctions directly allow ionic current to flow from one cell to another, without a chemical intermediary

EPSP (Excitatory Postsynaptic Potential)

A depolarizing potential caused by positive ion (Na+) influx, moving the membrane toward threshold

IPSP (Inhibitory Postsynaptic Potential)

A hyperpolarizing potential caused by Cl- influx or K+ efflux, moving the membrane away from threshold

Spatial summation

EPSPs (or IPSPs) generated simultaneously at many different synapses add together

Temporal summation

EPSPs generated by the SAME synapse firing rapidly in succession add together

Ionotropic receptor

Neurotransmitter binding directly opens an ion channel pore; fast-acting

Metabotropic receptor

Neurotransmitter binding activates a G-protein, which activates effector proteins/second messengers; slower, longer-lasting, can amplify signal

Quantal analysis

A method used to determine how many synaptic vesicles are releasing neurotransmitter

Criteria to be classified as a neurotransmitter

1) Synthesized/stored in the presynaptic neuron, 2) Released upon stimulation, 3) Applying the molecule mimics the effect of natural release

Amino acid neurotransmitters

Glutamate, GABA, Glycine — the brain's "fast and simple" neurotransmitters

Amine neurotransmitters

Dopamine, Serotonin, Norepinephrine, Acetylcholine — smaller molecules with broader, mood/state-regulating effects

Peptide neurotransmitters

Larger molecules (e.g. endorphins, oxytocin, Substance P) that act more slowly and often modulate pain/stress

Glutamate

The brain's main EXCITATORY neurotransmitter (amino acid type)

GABA

The brain's main INHIBITORY neurotransmitter (amino acid type); gates Cl- channels

Tyrosine

Amino acid precursor for the catecholamines: dopamine, norepinephrine, and epinephrine

Tryptophan

Essential amino acid precursor for serotonin

Vesicular transporters

Proteins that concentrate neurotransmitter molecules into synaptic vesicles against their gradient

Receptor agonist

A ligand that activates a receptor, mimicking the natural neurotransmitter (e.g. nicotine at nicotinic receptors)

Receptor antagonist

A ligand that blocks a receptor without activating it (e.g. curare at nicotinic receptors)

AMPA receptor

An ionotropic glutamate receptor; fast excitatory signaling; most subtypes are NOT calcium-permeable

NMDA receptor

An ionotropic glutamate receptor permeable to Na+, K+, and Ca2+; important for synaptic plasticity

GABA-A receptor

Ionotropic GABA receptor; opens a chloride channel, causing fast inhibition

GABA-B receptor

Metabotropic GABA receptor; activates G-proteins that open potassium channels, causing slower inhibition

Signal amplification (via G-protein cascades)

Second-messenger cascades can generate long-lasting chemical changes in cells, relevant to memory formation

Neuromuscular junction

The chemical synapse between a motor neuron and a skeletal muscle fiber; fast/reliable due to size and many active zones