Neuroscience and Sensory Systems Lecture Review

Comprehensive set of vocabulary flashcards covering neural structure, communication, neuropharmacology, development, somatosensation, audition, vestibular and chemical senses, and vision.

Dendrites

Branch-like extensions that receive incoming signals from other neurons.

Cell body (soma)

Contains the nucleus; integrates incoming signals and maintains the cell.

Axon

Long fiber that carries the action potential away from the cell body.

Axon terminals

Axon endings that release neurotransmitter into the synapse.

Information flow through a neuron and synapse

Dendrites receive, soma integrates, action potential travels down axon, terminals release neurotransmitter across the cleft onto postsynaptic receptors.

Glial cells

Support cells: astrocytes (nutrients, blood-brain barrier, cleanup), oligodendrocytes (CNS myelin), Schwann cells (PNS myelin), microglia (immune defense).

Central nervous system (CNS)

The brain and spinal cord.

Peripheral nervous system (PNS)

All nerves outside the brain and spinal cord; links the CNS to body and environment.

Somatic nervous system

PNS division carrying sensory input and controlling voluntary skeletal muscles.

Autonomic nervous system

PNS division controlling involuntary functions of organs and glands.

Sympathetic vs. parasympathetic

Sympathetic: fight-or-flight arousal (heart rate up). Parasympathetic: rest-and-digest conservation (heart rate down, digestion up).

Frontal lobe

Planning, decision making, voluntary movement (motor cortex), personality, speech production.

Parietal lobe

Touch and body sensation (somatosensory cortex), spatial processing, attention.

Temporal lobe

Hearing, language comprehension, object recognition, memory.

Occipital lobe

Primary visual processing.

Basal ganglia

Subcortical structures for initiating and smoothing voluntary movement and habits; damaged in Parkinson's and Huntington's.

Limbic system

Network for emotion, motivation, and memory (includes hippocampus and amygdala).

Hippocampus

Forms new long-term memories and supports spatial memory.

Amygdala

Processes fear and emotional significance; emotional memory.

Cerebellum

Coordinates movement, balance, timing, and motor learning.

Brainstem

Midbrain, pons, medulla; controls breathing, heart rate, arousal, and basic reflexes.

Resting membrane potential

About $-70\,\text{mV}$ charge difference across the membrane (inside negative) when the neuron is not firing; set up by ion gradients, permeability, and the pump.

Diffusion

Movement of ions from high to low concentration.

Electrostatic pressure

Attraction of opposite charges and repulsion of like charges; pulls $\text{K}^+$ back in and pushes $\text{Na}^+$ in.

Selective permeability

Membrane lets some ions through more easily than others (more $\text{K}^+$ leak channels than $\text{Na}^+$), helping maintain the resting potential.

Sodium-potassium pump

Uses ATP to move $3\,\text{Na}^+$ out and $2\,\text{K}^+$ in, maintaining the gradients.

Action potential sequence

Threshold reached, $\text{Na}^+$ channels open and $\text{Na}^+$ rushes in (depolarization), $\text{Na}^+$ channels inactivate, $\text{K}^+$ channels open and $\text{K}^+$ exits (repolarization), brief hyperpolarization, return to rest.

Threshold

Critical level of depolarization (about $-55\,\text{mV}$) that triggers an action potential.

All-or-none property

An action potential either fires at full size or not at all; stimulus intensity is coded by firing rate.

Depolarization

Membrane potential becomes less negative (toward or above $0$), caused by $\text{Na}^+$ influx.

Repolarization

Membrane returns toward resting potential as $\text{K}^+$ flows out.

Hyperpolarization

Membrane becomes more negative than rest, making firing less likely; follows $\text{K}^+$ overshoot.

Absolute refractory period

Time when $\text{Na}^+$ channels are inactivated and no second action potential can fire; limits firing rate and keeps the signal moving one way.

Relative refractory period

Time right after when a stronger-than-normal stimulus can trigger an action potential, due to hyperpolarization.

Myelination

Fatty insulation that speeds conduction because the current jumps between gaps instead of traveling continuously.

Saltatory conduction

Action potential jumping from node to node along a myelinated axon.

Nodes of Ranvier

Gaps in the myelin where ion channels are concentrated and the action potential is regenerated.

Synaptic transmission steps

Action potential arrives, $\text{Ca}^{2+}$ enters, vesicles release neurotransmitter, it binds postsynaptic receptors, then is cleared by reuptake, enzymes, or diffusion.

EPSP

Excitatory postsynaptic potential: small depolarization that moves the neuron toward threshold.

IPSP

Inhibitory postsynaptic potential: small hyperpolarization that moves the neuron away from threshold.

Spatial summation

EPSPs and IPSPs from different synapses at the same time add together.

Temporal summation

Rapid successive inputs at the same synapse add together.

Neural integration

Neuron sums all EPSPs and IPSPs; if the total reaches threshold at the axon hillock, it fires.

Criteria for a neurotransmitter

Made in the neuron, stored in the terminals, released with activity, causes a postsynaptic effect, mimicked by applying it, and has a removal mechanism.

Acetylcholine

Muscle contraction, attention, and memory; loss linked to Alzheimer's.

Dopamine

Movement (Parkinson's), reward and motivation; excess linked to psychosis.

Serotonin

Mood, sleep, and appetite; target of many antidepressants.

Norepinephrine

Arousal, alertness, and the stress response.

Glutamate

Main excitatory neurotransmitter; important in learning and memory.

GABA

Main inhibitory neurotransmitter.

Ionotropic receptors

Receptor is itself an ion channel; fast, brief effects.

Metabotropic receptors

Act through G proteins and second messengers; slower, longer lasting effects.

Agonist

Drug that mimics or enhances a neurotransmitter's effect.

Antagonist

Drug that blocks or reduces a neurotransmitter's effect.

Partial agonist

Binds a receptor but produces a weaker response than the full agonist.

Dose-response relationship

Higher doses produce greater effects, up to a maximum; shown as a curve.

Tolerance

Reduced drug effect with repeated use; involves receptor changes, faster metabolism, and compensatory (often conditioned) responses.

Drugs and neurotransmitter release

Drugs can increase or block release of a neurotransmitter from the terminals.

Drugs and reuptake

Drugs can block reuptake, leaving more neurotransmitter in the synapse.

Drugs and receptors

Drugs can activate or block receptors (agonists and antagonists).

Alcohol

Enhances GABA and inhibits glutamate; sedative depressant.

Cannabis

THC activates cannabinoid (CB1) receptors, mimicking endocannabinoids.

Nicotine

Agonist at nicotinic acetylcholine receptors; increases dopamine.

Opioids

Activate opioid receptors, mimicking endorphins; pain relief, euphoria, respiratory depression.

Stimulants

Boost dopamine and norepinephrine: cocaine blocks reuptake; amphetamine increases release and blocks reuptake.

Theories of addiction

Positive reinforcement (seeking pleasure), negative reinforcement (avoiding withdrawal), incentive-sensitization (cue "wanting" grows beyond "liking").

Ventral tegmental area (VTA)

Midbrain source of dopamine neurons in the reward pathway.

Nucleus accumbens

Forebrain target of VTA dopamine; key for reward and reinforcement.

Dopamine reward pathway

VTA to nucleus accumbens (mesolimbic path); activated by natural rewards and addictive drugs.

Neurogenesis

Birth of new neurons from stem cells.

Cell migration

Neurons travel to their final locations, guided by radial glia and chemical signals.

Differentiation

Cells become specific neuron types with specialized features.

Synaptogenesis

Axons grow to targets and form synapses.

Cell death

Many neurons (often about half) die during development.

Synapse rearrangement

Connections are refined and pruned based on activity and experience.

Neurotrophic factors

Chemicals (such as NGF, BDNF) that support neuron survival, growth, and connections.

Programmed cell death

Natural elimination of excess or poorly connected neurons; matches neuron numbers to targets and sharpens circuits.

Synaptic pruning

Removal of unused synapses; more synapses is not always better since pruning makes circuits efficient.

Sensitive periods

Time windows when experience has an especially strong effect on development.

Visual deprivation

Blocking input from one eye during a sensitive period weakens its cortical representation (amblyopia).

Genotype

An organism's genetic makeup.

Phenotype

Observable traits resulting from genotype plus environment.

Experience and gene expression

Experience can switch genes on or off without changing the DNA sequence.

Epigenetics

Study of changes in gene expression that do not alter the DNA sequence.

Methylation

Methyl groups attach to DNA, typically silencing the gene.

Gene-environment interaction

Genes set possibilities; environment and experience shape which are expressed.

Sensory transduction

Conversion of a physical stimulus into an electrical neural signal.

Labeled lines

Which neurons are activated tells the brain the type and location of the stimulus.

Pacinian corpuscles

Deep pressure and high-frequency vibration.

Meissner corpuscles

Light touch and low-frequency flutter; rapidly adapting, in fingertips.

Merkel discs

Sustained pressure, fine detail, edges, and texture.

Ruffini endings

Skin stretch and sustained pressure.

Receptive field

Area of the body (or visual field) where a stimulus changes a neuron's firing.

Phasic receptors

Respond at stimulus onset or change, then adapt quickly.

Tonic receptors

Keep firing during a sustained stimulus.

Sensory adaptation

Reduced response to a constant stimulus over time.

Touch pathway

Receptor, dorsal root, dorsal column up the spinal cord, crosses in medulla, thalamus, somatosensory cortex (parietal lobe).

Pain pathways

Spinothalamic route: fast A-delta fibers (sharp pain) and slow C fibers (dull, burning pain); crosses in the spinal cord, then thalamus and cortex.

Nociceptors

Receptors that detect damaging or potentially damaging stimuli.

Substance P

Neurotransmitter that transmits pain signals.