Visual Pathways Overview, Action Potential Overview, Neuronal Electrical Signals Overview, Neural Systems Overview, Directional Terms and Brain Anatomy, Eye Anatomy Overview, Ion Channels and Action Potentials, cogs1000 - the eye, The Eye, Week 1 - N…

Binocular Visual Field

Both eyes register central regions

Primary Visual Pathway

Retina > Thalamus > Striate cortex

Optic Radiations

Fibers from thalamus to visual cortex

Calcarine Sulcus

Primary visual cortex location

Dorsal Parietal Optic Radiations

Carry lower visual field information

Temporal Lobe

Path for upper visual field information

Pretectum

Coordinates pupillary light reflex

Edinger-Westphal Nucleus

Contains preganglionic parasympathetic neurons

Ciliary Ganglion

Innervates iris constrictor muscle

Suprachiasmatic Nucleus

Influences functions entrained to day-night cycle

Superior Colliculus

Coordinates head and eye movements

Retinal Ganglion Cells

Initiate interactions leading to visual perception

Optic Chiasm

Partial crossing of ganglion cell axons

Ganglion Cell Axons

Form optic tract after optic chiasm

Melanopsin

Photopigment in ganglion cells for light sensitivity

Retinotopic Representation

Brain processes visual field based on eye location

Fovea

Central area of retina with high acuity

Nasal Retina

Retina region where ganglion cell axons exit

Thalamus

Relay station for visual information to cortex

Striate Cortex

Primary visual cortex, Brodmann area 17

Occipital Lobe

Brain region where visual processing occurs

Temporal Retina

Receives information from the nasal visual field

Superior Retina

Receives information from the inferior visual field

Binocular Field

Overlap of visual fields from both eyes

Nasal Visual Field

Part of the visual field seen by the nasal retina

Cortical Magnification

Discrepancy in cortical representation of visual fields

Lateral Geniculate Nucleus

Thalamic structure relaying visual information to the cortex

Hubel and Wiesel

Researchers who studied visual cortex organization

Receptive Field

Area where stimuli influence neuron activity

Preferred Orientation

Specific angle at which a neuron responds most strongly

Neocortex

Outer layer of the brain responsible for higher functions

Pyramidal Neurons

Neurons with dendritic spines and glutamate neurotransmission

Smooth Dendritic Neurons

Neurons without spines involved in cortical inhibition

GABA

Inhibitory neurotransmitter used by smooth dendritic neurons

Laminar Structure

Distinct layers in the neocortex for processing information

Binocular Neurons

Neurons in the striate cortex responding to both eyes

Monocular Neurons

Geniculate neurons driven by one eye exclusively.

Ocular Dominance Columns

Cortical columns segregating signals from left and right eyes.

Ocular Dominance Stripes

Pattern reflecting the strength of eye inputs in cortical neurons.

Retinal Disparities

Differences in images from both eyes processed by specific neurons.

Stereoscopic Depth

Perception of depth created by binocular vision.

Magnocellular Layers

Layers with large neurons in the lateral geniculate nucleus.

Parvocellular Layers

Layers with small neurons in the lateral geniculate nucleus.

M Ganglion Cells

Cells terminating in magnocellular layers with larger structures.

P Ganglion Cells

Cells terminating in parvocellular layers with smaller structures.

Primary Visual Cortex

Receives axons from magnocellular and parvocellular layers.

Koniocellular Pathway

Distinct pathway in the lateral geniculate nucleus for fine-caliber axons.

Color Sensitivity

Ability of cells to detect differences in light wavelengths.

Temporal Resolution

Ability to perceive rapidly changing stimuli.

Spatial Resolution

Ability to analyze shape, size, and color details of an object.

Ventral Stream

System for high-resolution form vision and object recognition.

Dorsal Stream

System for processing motion and spatial location.

Visual Field Representation

Distinct areas in the brain processing different visual aspects.

Multisensory Integration

Combining information from different visual pathways in higher brain areas.

Spinal Reflexes

Reflex behaviors driven by sensory inputs without brain involvement.

Local Circuitry

Neural circuits within the spinal cord for reflex responses.

Action Potential

Fundamental electrical signal from nerve cells due to ion permeability changes

Voltage Clamp Technique

Method allowing detailed study of ion permeability changes with membrane potential

Sodium Permeability

Rapid rise in Na+ permeability during action potential generation

Potassium Permeability

Slower rise in K+ permeability following Na+ increase, restoring membrane potential

Passive Flow Currents

Currents through diffusion without cell energy expenditure

Voltage-Dependent Permeabilities

Na+ and K+ permeabilities increase with membrane depolarization

Equilibrium Potential

Voltage at which there is no net flow of ions across the membrane

Membrane Conductance

Reciprocal of membrane resistance, related to ion permeability

Ohm's Law

States voltage equals current multiplied by resistance

Inactivation

Decrease in Na+ conductance over time at depolarized levels

Voltage-Dependent Conductance

Na+ and K+ conductances increase with neuron depolarization

Ion Channels

Regulate ion flow, opening or closing based on membrane potential

Equilibrium Voltage (ENa)

Voltage where Na+ ion flow into neuron balances out, affecting membrane potential

Depolarization

Cell membrane becomes less negative, Na+ ions enter

Na+ Conductance Inactivation

Decrease in force driving Na+ ions, slows depolarization

K+ Conductance Activation

K+ ions leave cell, membrane potential more negative

Repolarization

Membrane potential returns to resting state

Undershoot

Brief hyperpolarization after repolarization

Positive Feedback Loop

Na+ entry depolarizes, activating more Na+ conductance

Regenerative Action Potential

Self-sustaining depolarization until restoration of resting potential

All-or-None Behavior

Action potentials either fully occur or not at all

Threshold

Minimum depolarization needed to trigger an action potential

Negative Feedback Loop

K+ conductance activation restores membrane to resting state

Hodgkin and Huxley Model

Explains action potential with voltage-sensitive ion conductances

Long-Distance Signaling

Action potential propagation along axon through current flow

Refractory Period

Limits neuron's ability to produce subsequent action potentials

Conduction Velocity

Speed of action potential propagation down axon

Myelination

Insulation of axon, speeding up action potential conduction

Nodes of Ranvier

Gaps in myelin where action potentials are generated

Potassium

Ion with positive charge, more inside cells

Sodium

Ion with positive charge, more outside cells

Fluoride

Ion with negative charge, more outside cells

Resting Membrane Potential

Average neuron potential around -70mV at rest

Sodium-Potassium Pump

Mechanism pumping 3 Na+ out, 2 K+ in to maintain potential

Diffusion Force

Depends on concentration gradient and channel permeability

Goldman Equation

Determines equilibrium potential based on ion concentrations

Action Potential

Rapid change in membrane voltage, neuron signal

Depolarization

Reduces membrane polarization, moves potential closer to 0

Threshold Membrane Potential

Level (-55mV) where sodium channels open, depolarization occurs

Repolarization

Restoration of membrane potential after action potential

Hyperpolarization

Membrane potential becomes more negative than resting potential

Neurotransmitters

Chemicals binding to receptors affecting neuron behavior

Axon Terminals

Ends of neuron transmitting signals to next neuron

Microelectrode

Device measuring electrical potential across neuron membrane